Monday.
1411.7378
Pathway to the galactic distribution of planets: combined Spitzer and ground-based microns Parallax measurements of 21 single-lens events
Novati, Gould, ... et al
Present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was ~1 AU West of Earth in projection. Combine these measurements with a kinematic model of the Galaxy to derive distance estimates for each lens, with error bars that are small compared to the Sun's Galactocentric distance. The ensemble therefore yields a well-defined cumulative distribution of lens distances. In principle it is possible to compare this distribution against a set of planets detected in the same experiment in order to measure the Galactic distribution of planets. Since these Spitzer observations yielded only one planet, this is not yet possible in practice. However, it will become possible as large samples are accumulated.
1411.7427
Future detectability of gravitational-wave induced lensing from high-sensitivity CMB experiments
Namikawa, Yamauchi, Taruya
Discuss the future detectability of gravitational-wave induced lensing from high-sensitivity CMB experiments. Gravitational waves can induce a rotational component of the WL deflection angle, usually referred to as the curl mode, which would be imprinted on the CMB maps. Using the technique of reconstructing lensing signals involved in CMB maps, this curl mode can be measured in an unbiased manner, offering an independent confirmation of the gravitational waves complementary to the B-mode polarization experiments. Based on the Fisher matrix analysis, first show that with the noise levels necessary to confirm the consistency relation for the primordial gravitational waves, the future CMB experiments will be able to detect the gravitational-wave induced lensing would be detected at more than 3 sigma significance level. Further, point out that high-sensitivity experiments will be also powerful to constrain the gravitational waves generate after the recombination epoch. Compared to the B-mode polarization, the curl mode is particularly sensitive to gravitational waves generated at low redshifts (z<10) with a low frequency (k<1e-3 Mpc^-1), and it could give a much tighter constraint on their energy density Omega_GW by more than 3 orders of magnitude.
1411.7999
The Atacama Cosmology Telescope: detection of lensing of the cosmic microwave background by dark matter haloes
Madhavacheril, Sehgal, ... et al
Present a statistical detection of the gravitational lensing of the CMB by 1e13 Msun DM haloes. Lensing convergence maps from ACTPol are stacked at the positions of around 12k optically-selected CMASS galaxies from SDSS/BOSS survey. The mean lensing signal is consistent with simulated DM halo profiles, and is favored over a null signal at 3.2 sigma significance. This result demonstrates the potential of microwave background lensing to probe the DM distribution in galaxy group and galaxy cluster haloes.
Sunday, November 30, 2014
Thursday, November 27, 2014
Day 795
Thursday.
1411.7029
On the recovery of galaxy properties from SED fitting solutions
Gladis, et al
Explore the ability of 4 different inverse population synthesis codes to recover the physical properties of galaxies from their spectra by SED fitting. DynBaS, TGASPEX, and GASPEX have been implemented by the authors and are described in detail. STARLIGHT is publicly available. DynBaS selects dynamically a different spectral basis to expand the spectrum of each target galaxy; TGASPEX uses an unconstrained age basis, where as GASPEX and STARLIGHT use for all fits a fixed spectral basis selected a priori by the code developers. Variable and unconstrained basis reflect the peculiarities of the fitted spectrum and allow for simple and robust solutions to the problem of extracting galaxy parameters from spectral fits. Assemble a Synthetic Spectral Atlas of Galaxies (SSAG), comprising of 100k galaxy spectra corresponding to an equal number of SFHs based on the recipe of Chen+2012. Select a subset of 120 galaxies from SSAG with a color distribution similar to that of local galaxies in SDSS DR7 and produce 30 random noise realizations for each of these spectra. For each spectrum, recover the mass, mean age, metallicity, internal dust extinction, and velocity dispersion characterizing the dominant stellar population in the problem galaxy. All methods produce almost perfect fits to the target spectrum, but the recovered physical parameters can differ significantly. The tests provide a quantitative measure of the accuracy and precision with which these parameters are recovered by each method. From a statistical point of view, all methods yield similar precisions, whereas DynBaS produces solutions with minimal systematic biases in the distributions of residuals for all of these parameters.
1411.7032
A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
Hönig, Watson, Kishimoto, Hjorth
The active galaxy NGC 4151 has a crucial role as one of the only two active galactic nuclei for which BH mass measurements based on emission line reverberation mapping can be calibrated against other dynamical methods. Unfortunately, effective calibration requires an accurate distance to NGC 4151, which is currently not available. Recently reported distances range from 4 to 29 Mpc. Strong peculiar motions make a z-based distance very uncertain, and the geometry of the galaxy and its nucleus prohibit accurate measurements using other techniques. Report a dust-parallax distance to NGC 4151 of D_A=19.0pm2.5 Mpc. The measurement is based on an adaptation of a geometric method proposed previously using the emission line regions of active galaxies. Since this region is too small for current imaging capabilities, use instead the ratio of the physical-to-angular sizes of the more extended hot dust emission as determined from time-delays and IR interferometry. This new distance leads to an approximately 1.4x increase in the dynamical BH mass, implying a corresponding correction to emission line reverberation masses of BHs if they are calibrated against the two objects with additional dynamical masses.
1411.7371
Uncovering blue diffuse dwarf galaxies
James, et al
Extremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy LF. Present a sub-sample of galaxies that were selected via a morphology-based search on SDSS images with the aim of finding the elusive XMP galaxies. By using the recently discovered extremely metal-poor galaxy, Leo P, as a guide, obtain a collection of faint, blue systems, each with isolated HII regions embedded in a diffuse continuum, that have remained undetected until now. Here show the first results from optical spectroscopic follow-up observations of 12 of ~100 of these blue, diffuse dwarf (BDD) galaxies yielded by the search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45<12+log(O/H)<8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young SF population (<10 Myr) and relatively high ionization parameters of their HII regions. Despite their low luminosities (-11<M_B<-18) and low surface brightnesses (~23-25 mag arcsec^-2), the galaxies were found to be actively SF, with current SFRs between 0.0003 and 0.078 Msun/yr. From the current subsample, BDD galaxies appear to be a population of non-quiescent dIrr galaxies, or the diffuse counterparts to blue compact galaxies (BCDs) and as such may bridge the gap between these two populations. The search algorithm demonstrates that morphology-based searches are successful in uncovering more diffuse metal-poor SF galaxies, which traditional emission-line based searches overlook.
1411.7029
On the recovery of galaxy properties from SED fitting solutions
Gladis, et al
Explore the ability of 4 different inverse population synthesis codes to recover the physical properties of galaxies from their spectra by SED fitting. DynBaS, TGASPEX, and GASPEX have been implemented by the authors and are described in detail. STARLIGHT is publicly available. DynBaS selects dynamically a different spectral basis to expand the spectrum of each target galaxy; TGASPEX uses an unconstrained age basis, where as GASPEX and STARLIGHT use for all fits a fixed spectral basis selected a priori by the code developers. Variable and unconstrained basis reflect the peculiarities of the fitted spectrum and allow for simple and robust solutions to the problem of extracting galaxy parameters from spectral fits. Assemble a Synthetic Spectral Atlas of Galaxies (SSAG), comprising of 100k galaxy spectra corresponding to an equal number of SFHs based on the recipe of Chen+2012. Select a subset of 120 galaxies from SSAG with a color distribution similar to that of local galaxies in SDSS DR7 and produce 30 random noise realizations for each of these spectra. For each spectrum, recover the mass, mean age, metallicity, internal dust extinction, and velocity dispersion characterizing the dominant stellar population in the problem galaxy. All methods produce almost perfect fits to the target spectrum, but the recovered physical parameters can differ significantly. The tests provide a quantitative measure of the accuracy and precision with which these parameters are recovered by each method. From a statistical point of view, all methods yield similar precisions, whereas DynBaS produces solutions with minimal systematic biases in the distributions of residuals for all of these parameters.
1411.7032
A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
Hönig, Watson, Kishimoto, Hjorth
The active galaxy NGC 4151 has a crucial role as one of the only two active galactic nuclei for which BH mass measurements based on emission line reverberation mapping can be calibrated against other dynamical methods. Unfortunately, effective calibration requires an accurate distance to NGC 4151, which is currently not available. Recently reported distances range from 4 to 29 Mpc. Strong peculiar motions make a z-based distance very uncertain, and the geometry of the galaxy and its nucleus prohibit accurate measurements using other techniques. Report a dust-parallax distance to NGC 4151 of D_A=19.0pm2.5 Mpc. The measurement is based on an adaptation of a geometric method proposed previously using the emission line regions of active galaxies. Since this region is too small for current imaging capabilities, use instead the ratio of the physical-to-angular sizes of the more extended hot dust emission as determined from time-delays and IR interferometry. This new distance leads to an approximately 1.4x increase in the dynamical BH mass, implying a corresponding correction to emission line reverberation masses of BHs if they are calibrated against the two objects with additional dynamical masses.
1411.7371
Uncovering blue diffuse dwarf galaxies
James, et al
Extremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy LF. Present a sub-sample of galaxies that were selected via a morphology-based search on SDSS images with the aim of finding the elusive XMP galaxies. By using the recently discovered extremely metal-poor galaxy, Leo P, as a guide, obtain a collection of faint, blue systems, each with isolated HII regions embedded in a diffuse continuum, that have remained undetected until now. Here show the first results from optical spectroscopic follow-up observations of 12 of ~100 of these blue, diffuse dwarf (BDD) galaxies yielded by the search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45<12+log(O/H)<8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young SF population (<10 Myr) and relatively high ionization parameters of their HII regions. Despite their low luminosities (-11<M_B<-18) and low surface brightnesses (~23-25 mag arcsec^-2), the galaxies were found to be actively SF, with current SFRs between 0.0003 and 0.078 Msun/yr. From the current subsample, BDD galaxies appear to be a population of non-quiescent dIrr galaxies, or the diffuse counterparts to blue compact galaxies (BCDs) and as such may bridge the gap between these two populations. The search algorithm demonstrates that morphology-based searches are successful in uncovering more diffuse metal-poor SF galaxies, which traditional emission-line based searches overlook.
Wednesday, November 26, 2014
Day 794
Wednesday.
1411.5398
Chitah: strong-gravitational-lens hunter in imaging surveys
Chan, Suyu, ... Marshall, Coupon, Oguri, et al
SL quasars provide means to study galaxy evolution and cosmology. Current and upcoming imaging surveys will contain thousands of new lensed quasars, augmenting the existing sample by at least 2 orders of magnitudes. TO find such lens systems, build Chitah that hunts for lensed quasars by modeling the configuration of the multiple quasar images. Given an image of an object that might be a lensed quasar, Chitah first disentangles the light from the supposed lens galaxy and the right from the multiple quasar images based on color info. A simple rule is designed to categorize the given object into a potential quad or double lensed quasar system. The configuration of the identified quasar images is subsequently modeled to classify whether the object is a lensed quasar system. Test the performance of Chitah using simulated lens systems based on CFHTLS. For bright quads with large image separations (r_Einstein > 1.1"), a high try-positive rate of >90% and a low cals-positive rate of <3% show that this is a promising approach. Obtain high true-positive rate for lens systems with r_Einstein > 0.5", so the performance of Chitah is set by the seeing. Further feed a known gravitational lens system in COSMOS to Chitah, and demonstrate that Chitah is able to classify successfully this real gravitational lens system. Chita is omnivorous and can hunt in any ground-based imaging surveys.
1411.6724
Dust content, galaxy orientations, and shape noise in imaging surveys
Pattarakijwanich, Schmidt
Show that dust absorption in disk galaxies leads to a color- and orientation-dependent centroid shift which is expected to be observable in multi-band imaging surveys. This centroid shift is an interesting new probe which contains astrophysical and cosmologically relevant information: it can be used to probe the dust content of a large sample of galaxies, and to reduce the shape noise due to inclination of disk galaxies for WL shear. Specifically, find that data sets comparable to CFHTLenS, the DES or the HSC survey should probe a dust measurement for several hundred galaxies per square degree. Conversely, given knowledge of the dust optical depth, this technique will significantly lower the shape noise for the brightest galaxies in the sample (S/N greater than a few hundred), thereby increasing their relative importance for the WL shear measurement.
1411.6628
Primordial star clusters at extreme magnification
Zackrisson, et al
If magnification of ~1000 possible (normally only up to 100), then can probe intrinsically small, high-z objects with very high number densities. Explore the prospects of detecting compact (<10 pc), high-z (z>7) Pop III star clusters at extreme magnifications in large-area surveys with planned telescopes like Euclid, WFIRST and WISH. Find that the planned WISH 100 sq. deg ultra deep survey may be able to detect a small number of such objects, provided that the total stellar mass of these star clusters is >1e4 Msun. If candidates for such lensed Pop III star clusters are found, follow-up spectroscopy of the surrounding nebula wit the JWST or ground based ELT should be able to confirm the Pop III nature of these objects. Multi band photometry of these objects with JWST also has the potential to confirm that the stellar IMF in these Pop III star clusters is top-heavy, as supported by current simulations.
1411.6807
The Sun and stars: giving light to dark matter
Casanellas, Lopes
Present recent results of use of stars to test new physics, in particular the properties of the hypothetical particles that constitute the dark matter of the Universe.
1411.5398
Chitah: strong-gravitational-lens hunter in imaging surveys
Chan, Suyu, ... Marshall, Coupon, Oguri, et al
SL quasars provide means to study galaxy evolution and cosmology. Current and upcoming imaging surveys will contain thousands of new lensed quasars, augmenting the existing sample by at least 2 orders of magnitudes. TO find such lens systems, build Chitah that hunts for lensed quasars by modeling the configuration of the multiple quasar images. Given an image of an object that might be a lensed quasar, Chitah first disentangles the light from the supposed lens galaxy and the right from the multiple quasar images based on color info. A simple rule is designed to categorize the given object into a potential quad or double lensed quasar system. The configuration of the identified quasar images is subsequently modeled to classify whether the object is a lensed quasar system. Test the performance of Chitah using simulated lens systems based on CFHTLS. For bright quads with large image separations (r_Einstein > 1.1"), a high try-positive rate of >90% and a low cals-positive rate of <3% show that this is a promising approach. Obtain high true-positive rate for lens systems with r_Einstein > 0.5", so the performance of Chitah is set by the seeing. Further feed a known gravitational lens system in COSMOS to Chitah, and demonstrate that Chitah is able to classify successfully this real gravitational lens system. Chita is omnivorous and can hunt in any ground-based imaging surveys.
1411.6724
Dust content, galaxy orientations, and shape noise in imaging surveys
Pattarakijwanich, Schmidt
Show that dust absorption in disk galaxies leads to a color- and orientation-dependent centroid shift which is expected to be observable in multi-band imaging surveys. This centroid shift is an interesting new probe which contains astrophysical and cosmologically relevant information: it can be used to probe the dust content of a large sample of galaxies, and to reduce the shape noise due to inclination of disk galaxies for WL shear. Specifically, find that data sets comparable to CFHTLenS, the DES or the HSC survey should probe a dust measurement for several hundred galaxies per square degree. Conversely, given knowledge of the dust optical depth, this technique will significantly lower the shape noise for the brightest galaxies in the sample (S/N greater than a few hundred), thereby increasing their relative importance for the WL shear measurement.
1411.6628
Primordial star clusters at extreme magnification
Zackrisson, et al
If magnification of ~1000 possible (normally only up to 100), then can probe intrinsically small, high-z objects with very high number densities. Explore the prospects of detecting compact (<10 pc), high-z (z>7) Pop III star clusters at extreme magnifications in large-area surveys with planned telescopes like Euclid, WFIRST and WISH. Find that the planned WISH 100 sq. deg ultra deep survey may be able to detect a small number of such objects, provided that the total stellar mass of these star clusters is >1e4 Msun. If candidates for such lensed Pop III star clusters are found, follow-up spectroscopy of the surrounding nebula wit the JWST or ground based ELT should be able to confirm the Pop III nature of these objects. Multi band photometry of these objects with JWST also has the potential to confirm that the stellar IMF in these Pop III star clusters is top-heavy, as supported by current simulations.
1411.6807
The Sun and stars: giving light to dark matter
Casanellas, Lopes
Present recent results of use of stars to test new physics, in particular the properties of the hypothetical particles that constitute the dark matter of the Universe.
Monday, November 24, 2014
Day 793
Tuesday.
1411.6009
Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens
Kelly, ... Treu, ... Filippenko, ... Riess, Bradac, ... Linden, et al
Discovery of the first multiply-imaged gravitationally-lensed SN. The 4 images form an Einstein cross with over 2" diameter around a z=0.544 elliptical galaxy that is a member of a galaxy cluster. The SN appeared in HST exposures as part of the Grism Lens-Amplified Survey from Space. The images of the SN coincide with the strongly lensed arm of a spiral galaxy at z=1.491, which is itself multiply imaged by the cluster potential. A measurement of the time delays between the multiple images and their magnification will provide new unprecedented constraints on the distribution of luminous and DM in the lensing galaxy and in the cluster, as well as on the cosmic expansion rate.
1411.6192
Unveiling the cosmological information beyond linear scales: forecasts of sufficient statistics
Wolk, Carron, Szapudi
Beyond the linear regime, Fourier modes of cosmological random fields become correlated, and the PS of density fluctuations contains only a fraction of the available cosmo information. To unveil this formerly hidden information, the A* NL transform was introduced; it is optimized both for the NLs induced by gravity and observational noise. Quantifying the resulting increase of the knowledge of cosmological parameters, forecast the constraints from the angular PS and that of A* from ell~200 to 3000 for upcoming galaxy surveys such as: WFIRST, LSST, Euclid, HSC and DES. Find that at low z this new data analysis strategy can double the extracted info, effectively doubling the survey area. To test the accuracy of the forecasting and the power of the data analysis methods, apply the A* transformation to the latest release of the CFHTLS Wide. While this data set is too sparce to allowl for more than modest gains (~1.1-1.2), the realized gain from the method is in excellent agreement with the forecast, thus verifying the robustness of the analysis and prediction pipelines.
1411.6212
Physical properties of compact star-forming galaxies at $z\sim2-3$
Ma, Fang, Kong, Fan
Present a study on the physical properties of compact SF galaxies (cSFGs) with M*>1e10 Msun and 2<z<3 in the COSMOS and GOODS-S fields, to explore whether they are a transitional type of galaxies between extended SF galaxies (eSFGs) and compact quiescent galaxies (cQGs) on the evolutionary path. The cSFGs distribute at nearly the same locus on the MS as eSFGs and dominate the high mass end. On the rest-frame U-V vs V-J and U-B vs M_B diagrams, cSFGs mainly distribute at the middle of eSFGs and cQGs in all colors, but are more inclined to "red sequence" than "green valley" galaxies. Find cSFGs have similar distributions with cQGs on the nonparametric morphology diagrams. About 1/3 of cSFGs show signatures of post mergers, and nearly none of them can be recognized as disks. The general distributions of cSFGs on stellar population and structural parameters are very similar to cQGs, implying the cSFGs are the direct progenitors of cQGs. In the meanwhile, cSFGs show the highest fraction of AGNs compared to eSFGs and cQGs, supporting the expectation that the transformation from eSFG to cSFG by gas-rich dissipative processes will intensify both the SF and the BH growth. The results of all the analysis described above suggest that cSFG is likely to be a transitional type of galaxy between eSFG towards cQG at z>2.
1411.6339
On the perturbation of the luminosity distance by peculiar motions
Kaiser, Hudson
Consider some aspects of the perturbation to the D_L(z) that are of relevance for SN1a cosmology and for future peculiar velocity surveys at non-negligible z. 1) previous work has shown that the correction to the lowest order perturbation dD/D = -dv/cz has the peculiar characteristic that it appears to depend on the absolute state of motion of sources, rather than on their motion relative to that of the observer. The resolution of this apparent violation of the equivalence principle is that it is necessary to allow for evolution of the velocities with time, and also, when considering perturbations on the scale of the observer-source separation, to include the gravitational z effect. Provide an expression for dD/D that provides a physically consistent way to compute the impact of peculiar motions for NS1a cosmology and peculiar velocity surveys. 2) Calculate the perturbation to the redshift as a function of source flux density, which has been proposed as an alternative probe of large-scale motions. Show how the inclusion of surface brightness modulation modifies the relation between dz(m) and the peculiar velocity, and that, while the noise properties of this method might appear promising, the velocity signal is swamped by the effect of galaxy clustering for most scales of interest. 3) Show how, in linear theory, peculiar velocity measurements are biased downwards by the effect of smaller scale motions or by measurement errors (such as in photometric redshifts). Results nicely explain the effects seen in simulations by Koda+2013. Critically examine the prospects for extending peculiar velocity studies to large scales with near-term future surveys.
1411.6355
Galaxy and mass assembly (GAMA): mass-size relations of z$<$0.1 galaxies subdivided by S\'ersic index, colour and morphology
Lange, et al
8399 GAMA galaxies of 0.01<z<0.1: derive the M*-HLR relation. Important: adopted mass limits and sample selections (rejection of outliers, use of robust fitting methods, etc). In particular, note that for samples extending to low stellar mass limits (<1e10 Msun) the S\'ersic index bimodality, evident for high mass systems, becomes less distinct and no-longer acts as a reliable separator of early- and late-type systems. The final set of M*-HLR relations are reported for a variety of galaxy population subsets in 10 bands (ugrizZYJHKs) and are intended to provide a comprehensive low-z benchmark for the many ongoing high-z studies. Exploring the variation of the M*-HLR relations with wavelength, confirm earlier findings that galaxies appear more compact at longer wavelengths albeit at a smaller level than previously noted: a 1e10 Msun both spiral systems and elliptical show a decrease in size of 13% from g to Ks (which si near linear in log wavelength). Finally, note that the sizes used in this work are derived from 2D Sersic light profile fitting (GALFIT3), i.e., elliptical semi-major HLR, improving on earlier low-z benchmarks based on circular apertures.
1411.6443
Predicted properties of multiple images of the strongly lensed supernova SN Refusal
Oguri
The best-fit model predicts 6 SN images in total; i.e., two extra images in addition to the observed 4 Einstein cross SN images S1-S4. One extra image is predicted to have appeared about 17 years ago, whereas the other extra image is predicted to appear in about one year form the appearance of S1-S4, which is a testable prediction with near future observations. The predicted magnification factors of individual SN images range from ~18 for the brightest image to ~4 for the faint extra images. Confronting these predictions with future observations should provide an unprecedented opportunity to improve the understanding of cluster mass distributions.
1411.6595
Near optimal bispectrum estimators for large-scale structure
Schmittfull, Baldauf, Seljak
Clustering of LSS provides significant info through the PS of density perturbations. Additional information can be gained from higher-order statistics like the bispectrum, especially to break the degeneracy between the linear halo bias b_1 and the amplitude of fluctuations sigma_8. Propose new simple, computationally inexpensive bispectrum statistics that are near optimal for the specific applications like bias determination. Corresponding to the Legendre decomposition of NL halo bias and gravitational coupling at second order, these statistics are given by the cross-spectra of the density with 3 quadratic fields: the squared density, a tidal term, and a shift term. For haloes and galaxies the first two have associated NL bias terms b_2 and b_s2, respectively, while the shift term has none in the absence of velocity bias (valid in the k->0 limit). Thus the linear bias b_1 is best determined by the shift cross-spectrum, while the squared density and tidal cross-spectra mostly tighten constraints on b_2 and b_s2 once b_1 is known. Since the form of the cross-spectra is derived from optimal maximum-likelihood estimation, they contain the full bispectrum information on bias parameters. Perturbative analytical predictions for their expectation values and covariances agree with simulations on large scales, k<0.09h/Mpc at z=0.55 with Gaussan R=20Mpc/h smoothing, for MMM, and MM-halo combinations. For halo-halo-halo cross-spectra the model also needs to include corrections to the Poisson stochasticity.
1411.6009
Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens
Kelly, ... Treu, ... Filippenko, ... Riess, Bradac, ... Linden, et al
Discovery of the first multiply-imaged gravitationally-lensed SN. The 4 images form an Einstein cross with over 2" diameter around a z=0.544 elliptical galaxy that is a member of a galaxy cluster. The SN appeared in HST exposures as part of the Grism Lens-Amplified Survey from Space. The images of the SN coincide with the strongly lensed arm of a spiral galaxy at z=1.491, which is itself multiply imaged by the cluster potential. A measurement of the time delays between the multiple images and their magnification will provide new unprecedented constraints on the distribution of luminous and DM in the lensing galaxy and in the cluster, as well as on the cosmic expansion rate.
1411.6192
Unveiling the cosmological information beyond linear scales: forecasts of sufficient statistics
Wolk, Carron, Szapudi
Beyond the linear regime, Fourier modes of cosmological random fields become correlated, and the PS of density fluctuations contains only a fraction of the available cosmo information. To unveil this formerly hidden information, the A* NL transform was introduced; it is optimized both for the NLs induced by gravity and observational noise. Quantifying the resulting increase of the knowledge of cosmological parameters, forecast the constraints from the angular PS and that of A* from ell~200 to 3000 for upcoming galaxy surveys such as: WFIRST, LSST, Euclid, HSC and DES. Find that at low z this new data analysis strategy can double the extracted info, effectively doubling the survey area. To test the accuracy of the forecasting and the power of the data analysis methods, apply the A* transformation to the latest release of the CFHTLS Wide. While this data set is too sparce to allowl for more than modest gains (~1.1-1.2), the realized gain from the method is in excellent agreement with the forecast, thus verifying the robustness of the analysis and prediction pipelines.
1411.6212
Physical properties of compact star-forming galaxies at $z\sim2-3$
Ma, Fang, Kong, Fan
Present a study on the physical properties of compact SF galaxies (cSFGs) with M*>1e10 Msun and 2<z<3 in the COSMOS and GOODS-S fields, to explore whether they are a transitional type of galaxies between extended SF galaxies (eSFGs) and compact quiescent galaxies (cQGs) on the evolutionary path. The cSFGs distribute at nearly the same locus on the MS as eSFGs and dominate the high mass end. On the rest-frame U-V vs V-J and U-B vs M_B diagrams, cSFGs mainly distribute at the middle of eSFGs and cQGs in all colors, but are more inclined to "red sequence" than "green valley" galaxies. Find cSFGs have similar distributions with cQGs on the nonparametric morphology diagrams. About 1/3 of cSFGs show signatures of post mergers, and nearly none of them can be recognized as disks. The general distributions of cSFGs on stellar population and structural parameters are very similar to cQGs, implying the cSFGs are the direct progenitors of cQGs. In the meanwhile, cSFGs show the highest fraction of AGNs compared to eSFGs and cQGs, supporting the expectation that the transformation from eSFG to cSFG by gas-rich dissipative processes will intensify both the SF and the BH growth. The results of all the analysis described above suggest that cSFG is likely to be a transitional type of galaxy between eSFG towards cQG at z>2.
1411.6339
On the perturbation of the luminosity distance by peculiar motions
Kaiser, Hudson
Consider some aspects of the perturbation to the D_L(z) that are of relevance for SN1a cosmology and for future peculiar velocity surveys at non-negligible z. 1) previous work has shown that the correction to the lowest order perturbation dD/D = -dv/cz has the peculiar characteristic that it appears to depend on the absolute state of motion of sources, rather than on their motion relative to that of the observer. The resolution of this apparent violation of the equivalence principle is that it is necessary to allow for evolution of the velocities with time, and also, when considering perturbations on the scale of the observer-source separation, to include the gravitational z effect. Provide an expression for dD/D that provides a physically consistent way to compute the impact of peculiar motions for NS1a cosmology and peculiar velocity surveys. 2) Calculate the perturbation to the redshift as a function of source flux density, which has been proposed as an alternative probe of large-scale motions. Show how the inclusion of surface brightness modulation modifies the relation between dz(m) and the peculiar velocity, and that, while the noise properties of this method might appear promising, the velocity signal is swamped by the effect of galaxy clustering for most scales of interest. 3) Show how, in linear theory, peculiar velocity measurements are biased downwards by the effect of smaller scale motions or by measurement errors (such as in photometric redshifts). Results nicely explain the effects seen in simulations by Koda+2013. Critically examine the prospects for extending peculiar velocity studies to large scales with near-term future surveys.
1411.6355
Galaxy and mass assembly (GAMA): mass-size relations of z$<$0.1 galaxies subdivided by S\'ersic index, colour and morphology
Lange, et al
8399 GAMA galaxies of 0.01<z<0.1: derive the M*-HLR relation. Important: adopted mass limits and sample selections (rejection of outliers, use of robust fitting methods, etc). In particular, note that for samples extending to low stellar mass limits (<1e10 Msun) the S\'ersic index bimodality, evident for high mass systems, becomes less distinct and no-longer acts as a reliable separator of early- and late-type systems. The final set of M*-HLR relations are reported for a variety of galaxy population subsets in 10 bands (ugrizZYJHKs) and are intended to provide a comprehensive low-z benchmark for the many ongoing high-z studies. Exploring the variation of the M*-HLR relations with wavelength, confirm earlier findings that galaxies appear more compact at longer wavelengths albeit at a smaller level than previously noted: a 1e10 Msun both spiral systems and elliptical show a decrease in size of 13% from g to Ks (which si near linear in log wavelength). Finally, note that the sizes used in this work are derived from 2D Sersic light profile fitting (GALFIT3), i.e., elliptical semi-major HLR, improving on earlier low-z benchmarks based on circular apertures.
1411.6443
Predicted properties of multiple images of the strongly lensed supernova SN Refusal
Oguri
The best-fit model predicts 6 SN images in total; i.e., two extra images in addition to the observed 4 Einstein cross SN images S1-S4. One extra image is predicted to have appeared about 17 years ago, whereas the other extra image is predicted to appear in about one year form the appearance of S1-S4, which is a testable prediction with near future observations. The predicted magnification factors of individual SN images range from ~18 for the brightest image to ~4 for the faint extra images. Confronting these predictions with future observations should provide an unprecedented opportunity to improve the understanding of cluster mass distributions.
1411.6595
Near optimal bispectrum estimators for large-scale structure
Schmittfull, Baldauf, Seljak
Clustering of LSS provides significant info through the PS of density perturbations. Additional information can be gained from higher-order statistics like the bispectrum, especially to break the degeneracy between the linear halo bias b_1 and the amplitude of fluctuations sigma_8. Propose new simple, computationally inexpensive bispectrum statistics that are near optimal for the specific applications like bias determination. Corresponding to the Legendre decomposition of NL halo bias and gravitational coupling at second order, these statistics are given by the cross-spectra of the density with 3 quadratic fields: the squared density, a tidal term, and a shift term. For haloes and galaxies the first two have associated NL bias terms b_2 and b_s2, respectively, while the shift term has none in the absence of velocity bias (valid in the k->0 limit). Thus the linear bias b_1 is best determined by the shift cross-spectrum, while the squared density and tidal cross-spectra mostly tighten constraints on b_2 and b_s2 once b_1 is known. Since the form of the cross-spectra is derived from optimal maximum-likelihood estimation, they contain the full bispectrum information on bias parameters. Perturbative analytical predictions for their expectation values and covariances agree with simulations on large scales, k<0.09h/Mpc at z=0.55 with Gaussan R=20Mpc/h smoothing, for MMM, and MM-halo combinations. For halo-halo-halo cross-spectra the model also needs to include corrections to the Poisson stochasticity.
Sunday, November 23, 2014
Day 792
Monday.
1411.5688
The evolution of clustering length, large-scale bias and host halo mass at 2<z<5 in the VIMOS Ultra Deep Survey (VUDS)
Durkalec, Le Févre, ... et al
Investigate the evolution of galaxy clustering for galaxies in the redshift range 2.0<z<5.0 using VUDS. Present the projected real-space 2PCF w_p(r_p) measured by using 3022 galaxies with robust spectroscopic redshifts in two independent fields (COSMOS and VVDS-02h) covering in total 0.8 deg^2. Quantify how the scale dependent clustering amplitude r_0 changes with z making use of mock samples to evaluate and correct the survey selection function. Using a power-law model xi(r)=(r/r0)^-gamma, find that the correlation function for the general population is best fit by a model with a clustering length r0=3.95pm0.5 Mpc/h and slope gamma=1.8pm0.005 at z~2.25, r0=4.35pm0.06 Mpc/h and gamma=1.6pm0.12 at z~3.5. Use this clustering parameters to derive the large-scale linear galaxy bias b_L^PL, between galaxies and DM. Find b_L^PL=2.68pm0.22 at z~3 (assuming sigma_8=0.8), significantly higher than found at intermediate and low z. Fit an HOD model to the data and obtain the average halo mass at z~3 is M_h=1e11.75 Msun/h. From this fit, confirm that the large-scale linear galaxy bias is relatively high at b_L^HOD=2.82pm0.27. Comparing these measurements with similar measurements at lower redshifts, infer that the SF population of galaxies at z~3 should evolve into the massive and bright (M_r<-21.5) galaxy population which typically occupy haloes of mass <M_h>=1e13.9Msun/h at z=0.
1411.5689
On the importance of sing appropriate spectral models to derive physical properties of galaxies at 0.7<z<2.8
Pacifici, ... Rix, ... Franx, ... van Dokkum, ... et al
Interpreting observations of distant galaxies in terms of constraints on physical parameters - such as M*, SFR and dust optical depth - requires spectral synthesis modeling. Analyze the reliability of these physical parameters as determined under commonly adopted 'classical' assumptions: SFHs assumed to be exponentially declining functions of time, a simple dust law and no emission-line contribution. Improved modeling techniques and data quality now allow use of a more sophisticated approach, including realistic SFHs, combined with modern prescriptions for dust attenuation and nebular emission. Present a Bayesian analysis of the spectra and multi-wavelength photometry of 1048 galaxies from the 3D-HST survey in 0.7<z<2.8 and in the M* range 9<log(M*/Msun)<12. Find that, using the classical spectral library, M* are systematically overestimated (~0.1 dex) and SFRs are systematically underestimated (~0.6 dex) relative to the more sophisticated approach. Also find that the simultaneous fit of photometric fluxes and emission-line equivalent widths helps break a degeneracy between SFR and optical depth of the dust, reducing the uncertainties on these parameters. Finally, show how the biases of classical approaches can affect the correlation between M* and SFR for SF galaxies (the 'SF MS'). Conclude that the normalization, slope and scatter of this relation strongly depends the adopted approach and demonstrate that the classical, oversimplified approach cannot recover the true distribution of M* and SFR.
1411.5691
A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift
Rydberg, ... Zitrin,.. et al
Pop III galaxies are predicted to exist at high z and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a FG galaxy cluster. Pop III galaxies that exhibit strong Lya emission should furthermore be identifiable from broadband photometry because other unusual colors. Report on a search for such objects at z>6 in the imaging data from CLASH, covering 25 galaxy clusters in 16 filters. Select algorithm returns 5 singly-imaged candidates with Lya-like color signatures, for which ground-based spectroscopy with current 8-10m class telescopes should be able to test the predicted strength of the Lya line. None of these 5 objects have been included in previous CLASH compilations of high-z galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, find that only two of these candidates are significantly better fitted by Pop III models than by more mundane, low-z stellar populations.
1411.5688
The evolution of clustering length, large-scale bias and host halo mass at 2<z<5 in the VIMOS Ultra Deep Survey (VUDS)
Durkalec, Le Févre, ... et al
Investigate the evolution of galaxy clustering for galaxies in the redshift range 2.0<z<5.0 using VUDS. Present the projected real-space 2PCF w_p(r_p) measured by using 3022 galaxies with robust spectroscopic redshifts in two independent fields (COSMOS and VVDS-02h) covering in total 0.8 deg^2. Quantify how the scale dependent clustering amplitude r_0 changes with z making use of mock samples to evaluate and correct the survey selection function. Using a power-law model xi(r)=(r/r0)^-gamma, find that the correlation function for the general population is best fit by a model with a clustering length r0=3.95pm0.5 Mpc/h and slope gamma=1.8pm0.005 at z~2.25, r0=4.35pm0.06 Mpc/h and gamma=1.6pm0.12 at z~3.5. Use this clustering parameters to derive the large-scale linear galaxy bias b_L^PL, between galaxies and DM. Find b_L^PL=2.68pm0.22 at z~3 (assuming sigma_8=0.8), significantly higher than found at intermediate and low z. Fit an HOD model to the data and obtain the average halo mass at z~3 is M_h=1e11.75 Msun/h. From this fit, confirm that the large-scale linear galaxy bias is relatively high at b_L^HOD=2.82pm0.27. Comparing these measurements with similar measurements at lower redshifts, infer that the SF population of galaxies at z~3 should evolve into the massive and bright (M_r<-21.5) galaxy population which typically occupy haloes of mass <M_h>=1e13.9Msun/h at z=0.
1411.5689
On the importance of sing appropriate spectral models to derive physical properties of galaxies at 0.7<z<2.8
Pacifici, ... Rix, ... Franx, ... van Dokkum, ... et al
Interpreting observations of distant galaxies in terms of constraints on physical parameters - such as M*, SFR and dust optical depth - requires spectral synthesis modeling. Analyze the reliability of these physical parameters as determined under commonly adopted 'classical' assumptions: SFHs assumed to be exponentially declining functions of time, a simple dust law and no emission-line contribution. Improved modeling techniques and data quality now allow use of a more sophisticated approach, including realistic SFHs, combined with modern prescriptions for dust attenuation and nebular emission. Present a Bayesian analysis of the spectra and multi-wavelength photometry of 1048 galaxies from the 3D-HST survey in 0.7<z<2.8 and in the M* range 9<log(M*/Msun)<12. Find that, using the classical spectral library, M* are systematically overestimated (~0.1 dex) and SFRs are systematically underestimated (~0.6 dex) relative to the more sophisticated approach. Also find that the simultaneous fit of photometric fluxes and emission-line equivalent widths helps break a degeneracy between SFR and optical depth of the dust, reducing the uncertainties on these parameters. Finally, show how the biases of classical approaches can affect the correlation between M* and SFR for SF galaxies (the 'SF MS'). Conclude that the normalization, slope and scatter of this relation strongly depends the adopted approach and demonstrate that the classical, oversimplified approach cannot recover the true distribution of M* and SFR.
1411.5691
A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift
Rydberg, ... Zitrin,.. et al
Pop III galaxies are predicted to exist at high z and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a FG galaxy cluster. Pop III galaxies that exhibit strong Lya emission should furthermore be identifiable from broadband photometry because other unusual colors. Report on a search for such objects at z>6 in the imaging data from CLASH, covering 25 galaxy clusters in 16 filters. Select algorithm returns 5 singly-imaged candidates with Lya-like color signatures, for which ground-based spectroscopy with current 8-10m class telescopes should be able to test the predicted strength of the Lya line. None of these 5 objects have been included in previous CLASH compilations of high-z galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, find that only two of these candidates are significantly better fitted by Pop III models than by more mundane, low-z stellar populations.
Thursday, November 20, 2014
Day 791
Friday.
1411.5039
Introduction to astroML: Machine Leraning for Astrophysics
VenderPlas, Connolly, Ivezic, Gray
Astronomy and astrophysics are witnessing dramatic increases in data volume as detectors, telescopes and computers become more powerful. During the last decade, sky surveys across the EM spectrum have collected hundreds of terabytes of astronomical data for hundreds of millions of sources. Over the next decade, the data volume will enter the petabyte domain, and provide accurate measurements for billions of sources. Astronomy and physics students are not traditionally trained to handle such voluminous and complex data sets. In this paper, describe astroML; an initiative, based on Python and scikit-learn, to develop a compendium of machine learning tools designed to address the statistical needs of the next generation of students and astronomical surveys. Introduce astroML and present a number of example applications that are enabled by this package.
1411.5363
The relation between dynamical mass-to-light ratio and color for massive quiescent galaxies out to z~2 and comparison with stellar population synthesis models
van de Sande, Kriek, Franx, Bezanson, van Dokkum
Explore the relation between the dynamical M/L and rest-frame color of massive quiescent galaxies out to z~2. Use a galaxy sample with measured stellar velocity dispersions in combination with HST and ground-based multi-band photometry. Sample spans a large range in log (M/L_g) (of 1.6 dex) and log (M/L_K) (of 1.3 dex). There is a strong, approximately linear correlation between the M/L for different wavebands and rest-frame color. The root-mean-scatter scatter in log (M/L) residuals implies that it is possible to estimate the M/L with an accuracy of ~0.25 dex from a single rest-frame optical color. SPS models with a Salpeter stellar IMF cannot simultaneously match M/L vs (g-z) and M/L vs (g-K). By changing the slope of the IMF, still unable to explain the M/L of the bluest and reddest galaxies. Find that an IMF with a slope between alpha=2.35 and alpha=1.35 provides the best match. Also explore a broken IMF with a Salpeter slope at M<Msun and M>4Msun and a slope alpha in the intermediate region. The data favor a slope of alpha=1.35 over alpha=2.35. Nonetheless, results show that variations between different SPS models are comparable to the IMF variations. In the analysis, assume that the variation in M/L and color is driven by differences in age, and that other contributions (e.g., metallicity evolution, DM) are small. These assumptions may be an important source of uncertainty as galaxies evolve in more complex ways.
1411.5039
Introduction to astroML: Machine Leraning for Astrophysics
VenderPlas, Connolly, Ivezic, Gray
Astronomy and astrophysics are witnessing dramatic increases in data volume as detectors, telescopes and computers become more powerful. During the last decade, sky surveys across the EM spectrum have collected hundreds of terabytes of astronomical data for hundreds of millions of sources. Over the next decade, the data volume will enter the petabyte domain, and provide accurate measurements for billions of sources. Astronomy and physics students are not traditionally trained to handle such voluminous and complex data sets. In this paper, describe astroML; an initiative, based on Python and scikit-learn, to develop a compendium of machine learning tools designed to address the statistical needs of the next generation of students and astronomical surveys. Introduce astroML and present a number of example applications that are enabled by this package.
1411.5363
The relation between dynamical mass-to-light ratio and color for massive quiescent galaxies out to z~2 and comparison with stellar population synthesis models
van de Sande, Kriek, Franx, Bezanson, van Dokkum
Explore the relation between the dynamical M/L and rest-frame color of massive quiescent galaxies out to z~2. Use a galaxy sample with measured stellar velocity dispersions in combination with HST and ground-based multi-band photometry. Sample spans a large range in log (M/L_g) (of 1.6 dex) and log (M/L_K) (of 1.3 dex). There is a strong, approximately linear correlation between the M/L for different wavebands and rest-frame color. The root-mean-scatter scatter in log (M/L) residuals implies that it is possible to estimate the M/L with an accuracy of ~0.25 dex from a single rest-frame optical color. SPS models with a Salpeter stellar IMF cannot simultaneously match M/L vs (g-z) and M/L vs (g-K). By changing the slope of the IMF, still unable to explain the M/L of the bluest and reddest galaxies. Find that an IMF with a slope between alpha=2.35 and alpha=1.35 provides the best match. Also explore a broken IMF with a Salpeter slope at M<Msun and M>4Msun and a slope alpha in the intermediate region. The data favor a slope of alpha=1.35 over alpha=2.35. Nonetheless, results show that variations between different SPS models are comparable to the IMF variations. In the analysis, assume that the variation in M/L and color is driven by differences in age, and that other contributions (e.g., metallicity evolution, DM) are small. These assumptions may be an important source of uncertainty as galaxies evolve in more complex ways.
Wednesday, November 19, 2014
Day 790
Thursday.
1411.4983
Probing the galaxy-halo connection in UltraVISTA to $z\sim2$
McCracken, et al
Use %-level precision photo-z in UltraVISTA-DR1 NIR survey to investigate the changing relationship between galaxy M* and the DM haloes hosting them to z~2. Achieve this by measuring the clustering properties and abundances of a series of volume-limited galaxy samples selected by stellar mass and SF activity. Interpret these results in the framework of a phenomenological halo model and numerical simulations. Measurements span a uniquely large range in stellar mass and z and reach below the characteristic stellar mass to z~2. Results are: 1. At fixed z and scale, clustering amplitude depends monotonically on sample M* threshold; 2. at fixed angular scale, the projected clustering amplitude decreases with z but the co-moving correlation length remains constant; 3. characteristic halo masses and galaxy bias increase with increasing median stellar mass of the sample; 4. the slope of these relationships is modified in lower mass haloes; 5. concerning the passive galaxy population, characteristic halo masses are consistent with a simply less-abundant version of the full galaxy sample, but at lower z the fraction of satellite galaxies in the passive population is very different from the full galaxy sample; 6. find that the ratio between the characteristic halo mass and median stellar mass at each redshift bin reaches a peak at log(Mh/Msun)~12.2 and the position of this peak remains constant out to z~2. The behavior of the full and passively evolving galaxy samples can be understood qualitatively by considering the slow evolution of the characteristic M* in the z range probed by the survey.
1411.5022
The fastest unbound stars in the universe
Guillochon, Loeb
Hypervelocity stars (HVS) can (theoretically) frequently ejected with v_inf>1e4 km/s, and occasionally with ~1e5 km/s (c/3) in an interaction with massive BH with M>1e5 Msun. Depending on MBH interactions, the space density of fast-moving (>1e4 km/s) semi-relativistic hypervelocity stars, unbound to any galaxy, can be as large as 1e3 per Mpc^3. Hundreds of the SHS will be giant stars that could be detected by WFIRST or Euclid and proper motion surveys such as LSST, with spectroscopic follow-up being possible with JWST.
1411.5030
Observational cosmology with semi-relativistic stars
Loeb, Guillochon
Tracing the stars to their part galaxies as a function of speed and age will provide a novel test of the equivalence principle and the standard cosmological parameters. Semi-relativistic stars could also flag BH binaries as gravitational wave sources for the future eLISA observatory.
1411.4983
Probing the galaxy-halo connection in UltraVISTA to $z\sim2$
McCracken, et al
Use %-level precision photo-z in UltraVISTA-DR1 NIR survey to investigate the changing relationship between galaxy M* and the DM haloes hosting them to z~2. Achieve this by measuring the clustering properties and abundances of a series of volume-limited galaxy samples selected by stellar mass and SF activity. Interpret these results in the framework of a phenomenological halo model and numerical simulations. Measurements span a uniquely large range in stellar mass and z and reach below the characteristic stellar mass to z~2. Results are: 1. At fixed z and scale, clustering amplitude depends monotonically on sample M* threshold; 2. at fixed angular scale, the projected clustering amplitude decreases with z but the co-moving correlation length remains constant; 3. characteristic halo masses and galaxy bias increase with increasing median stellar mass of the sample; 4. the slope of these relationships is modified in lower mass haloes; 5. concerning the passive galaxy population, characteristic halo masses are consistent with a simply less-abundant version of the full galaxy sample, but at lower z the fraction of satellite galaxies in the passive population is very different from the full galaxy sample; 6. find that the ratio between the characteristic halo mass and median stellar mass at each redshift bin reaches a peak at log(Mh/Msun)~12.2 and the position of this peak remains constant out to z~2. The behavior of the full and passively evolving galaxy samples can be understood qualitatively by considering the slow evolution of the characteristic M* in the z range probed by the survey.
1411.5022
The fastest unbound stars in the universe
Guillochon, Loeb
Hypervelocity stars (HVS) can (theoretically) frequently ejected with v_inf>1e4 km/s, and occasionally with ~1e5 km/s (c/3) in an interaction with massive BH with M>1e5 Msun. Depending on MBH interactions, the space density of fast-moving (>1e4 km/s) semi-relativistic hypervelocity stars, unbound to any galaxy, can be as large as 1e3 per Mpc^3. Hundreds of the SHS will be giant stars that could be detected by WFIRST or Euclid and proper motion surveys such as LSST, with spectroscopic follow-up being possible with JWST.
1411.5030
Observational cosmology with semi-relativistic stars
Loeb, Guillochon
Tracing the stars to their part galaxies as a function of speed and age will provide a novel test of the equivalence principle and the standard cosmological parameters. Semi-relativistic stars could also flag BH binaries as gravitational wave sources for the future eLISA observatory.
Tuesday, November 18, 2014
Day 789
Wednesday.
* Chondrite: a stony (non-metallic) meteorites that have not been modified due to melting or differentiation of the parent body. They are formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids. They are the most common type of meteorite that falls to Earth (~86%). Provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the origin of life or the presence of water on Earth. One of their characteristics is the presence of chondrules, which are round grains formed by distinct minerals, that normally constitute between 20% and 80% by volume. Chondrites can be differentiated from iron meteorites due to their low Fe and Ni content. Other non-metallic meteorites, chondrites, which lack chondrules, were formed more recently.
* Chondrules: round grains found in chondrites. Chondrules form as a molten or partially molten droplets in space before being accreted to their parent asteroids. Because chondrites represent one of the oldest solid materials within our Solar System and are believed to be the building blocks of the planetary system, it follows that an understanding f the formation of chondrules is important to understand the initial development of the planetary system.
Science
Solar nebula magnetic fields recorded in the Semarkona meteorite
Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constrains on the intensity of these fields. Show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54pm21 muT. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the sun. This implies that background B-fields in the terrestrial planet-formation region were likely 5-54 muT, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.
1411.4646
Main-sequence stars masquerading as Young Stellar Objects in the central molecular zone
Koepferl, et al
Estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the SFR previously determined from YSOs is likely to be at least a factor of three too high.
Tons of paper dedicated to Michel Henon today: "hommage a Michel Henon".
* Chondrite: a stony (non-metallic) meteorites that have not been modified due to melting or differentiation of the parent body. They are formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids. They are the most common type of meteorite that falls to Earth (~86%). Provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the origin of life or the presence of water on Earth. One of their characteristics is the presence of chondrules, which are round grains formed by distinct minerals, that normally constitute between 20% and 80% by volume. Chondrites can be differentiated from iron meteorites due to their low Fe and Ni content. Other non-metallic meteorites, chondrites, which lack chondrules, were formed more recently.
* Chondrules: round grains found in chondrites. Chondrules form as a molten or partially molten droplets in space before being accreted to their parent asteroids. Because chondrites represent one of the oldest solid materials within our Solar System and are believed to be the building blocks of the planetary system, it follows that an understanding f the formation of chondrules is important to understand the initial development of the planetary system.
Science
Solar nebula magnetic fields recorded in the Semarkona meteorite
Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constrains on the intensity of these fields. Show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54pm21 muT. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the sun. This implies that background B-fields in the terrestrial planet-formation region were likely 5-54 muT, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.
1411.4646
Main-sequence stars masquerading as Young Stellar Objects in the central molecular zone
Koepferl, et al
Estimate the fraction of misclassified "YSOs" to be at least 63%, which suggests that the SFR previously determined from YSOs is likely to be at least a factor of three too high.
Tons of paper dedicated to Michel Henon today: "hommage a Michel Henon".
Monday, November 17, 2014
Day 788
Tuesday.
1411.4052
On the signature of the baryon-dark matter relative velocity in the two and three-point galaxy correlation functions
Slepian, Eisenstein
Develop a configuration-space picture of the relative velocity between baryons and DM that clearly explains how it can shift the BAO scale in the galaxy-galaxy correlation function. The shift occurs because the relative velocity is non-zero only within the sound horizon and thus adds to the correlation function asymmetrically about the BAO peak. Further show that in configuration space the relative velocity has a localized, distinctive signature in the 3PCF. In particular, find that a multipole decomposition is a favorable way to isolate the relative velocity in the 3PCF, and that there is a strong signature in the ell=1 multipole for triangles with 2 sides around the BAO scale. Investigate a further compression of the 3PCF to a function of only one triangle side that preserves the localized nature of the relative velocity signature while also nicely separating linear from non-linear bias. Expect that this scheme will substantially lessen the computational burden of finding the relative velocity in the 3PCF. The relative velocity's 3PCF signature can be used to correct the shift induced in the galaxy-galaxy correlation function so that no systematic error due to this effect is introduced into the BAO as used for precision cosmology.
1411.4189
The chemical signature of surviving population III stars in the Milky Way
Johnson
Simulations suggest IMF of Pop III stars may have extended to sub-solar masses. If <0.8Msun PopIII stars did form, then they should still be present n the Galaxy today as either MS or red giant stars. None found to date; but possibly because the metal-free nature of primordial stars are masked due to accretion of metal-enriched material from the ISM over the course of their long lifetimes. Point out that while gas accretion from the ISM may readily occur, the accretion of dust from ISM can be prevented due to radiation pressure from the low-mass stars. This implies a possible unique chemical signature for stars polluted only via accretion: an enhancement in gas phase elements relative to those in the dust phase. Outline the conditions in which this signature could be exhibited, and derive the expected signature for the case of accretion from the local ISM. Due to the large fraction of Fe depleted into dust relative to that of C and other elements, this signature is similar to that observed in many of the so-called carbon-enhanced metal-poor (CEMP) stars. Therefore suggest that some fraction of the observed CEMP stars may, in fact, be accretion-polluted Pop III stars. Find that this effect could also be at play in accretion flows onto protostars, implying that it may also impact the chemical signatures of Pop II stars.
1411.4574
Dust destruction rates and lifetimes in the Magellanic clouds
Temim, et al
The nature, composition, abundance, and size distribution of dust in galaxies is determined by the rate at which it is created in the different stellar sources and destroyed by interstellar shocks. Because of their extensive wavelength coverage, proximity, and nearly face-on geometry, the MCs provide a unique opportunity to study these processes in great detail. IN this paper, use the complete sample of SN remnants (SNRs) in the MCs to calculate the lifetime and destruction efficiencies of silicate and carbon dust in these galaxies. Find dust lifetimes of 22pm13 Myr (30pm17Myr) for silicate (carbon) grains in the LMC, and 54pm32 Myr (72pm43 Myr) for silicate (carbon) grains in the SMC. The significantly shorter lifetimes in the MCs, as compared to the MW, are explained as the combined effect of their lower total dust mass, and the fact that the dust-destroying isolated SNe in the MCs seem to preferentially occurring in regions with higher than average dust-to-gas (D2G) mass ratios. Also calculate the SNe rate and the current SFR in the MCs, and use them to derive maximum dust injection rates by asymptotic giant branch stars and core collapse SNe. Find that the injection rates are an order of magnitude lower than the dust destruction rates by the SNRs. This supports the conclusion that, unless the dust destruction rates have been considerably overestimated, most of the dust must be reconstituted from surviving grains in dense molecular clouds. More generally, also discuss the dependence of the dust destruction rate on the local D2G mass ratio, the ambient gas density and metallicity, as well as the application of the results to other galaxies and dust evolution models.
1411.4052
On the signature of the baryon-dark matter relative velocity in the two and three-point galaxy correlation functions
Slepian, Eisenstein
Develop a configuration-space picture of the relative velocity between baryons and DM that clearly explains how it can shift the BAO scale in the galaxy-galaxy correlation function. The shift occurs because the relative velocity is non-zero only within the sound horizon and thus adds to the correlation function asymmetrically about the BAO peak. Further show that in configuration space the relative velocity has a localized, distinctive signature in the 3PCF. In particular, find that a multipole decomposition is a favorable way to isolate the relative velocity in the 3PCF, and that there is a strong signature in the ell=1 multipole for triangles with 2 sides around the BAO scale. Investigate a further compression of the 3PCF to a function of only one triangle side that preserves the localized nature of the relative velocity signature while also nicely separating linear from non-linear bias. Expect that this scheme will substantially lessen the computational burden of finding the relative velocity in the 3PCF. The relative velocity's 3PCF signature can be used to correct the shift induced in the galaxy-galaxy correlation function so that no systematic error due to this effect is introduced into the BAO as used for precision cosmology.
1411.4189
The chemical signature of surviving population III stars in the Milky Way
Johnson
Simulations suggest IMF of Pop III stars may have extended to sub-solar masses. If <0.8Msun PopIII stars did form, then they should still be present n the Galaxy today as either MS or red giant stars. None found to date; but possibly because the metal-free nature of primordial stars are masked due to accretion of metal-enriched material from the ISM over the course of their long lifetimes. Point out that while gas accretion from the ISM may readily occur, the accretion of dust from ISM can be prevented due to radiation pressure from the low-mass stars. This implies a possible unique chemical signature for stars polluted only via accretion: an enhancement in gas phase elements relative to those in the dust phase. Outline the conditions in which this signature could be exhibited, and derive the expected signature for the case of accretion from the local ISM. Due to the large fraction of Fe depleted into dust relative to that of C and other elements, this signature is similar to that observed in many of the so-called carbon-enhanced metal-poor (CEMP) stars. Therefore suggest that some fraction of the observed CEMP stars may, in fact, be accretion-polluted Pop III stars. Find that this effect could also be at play in accretion flows onto protostars, implying that it may also impact the chemical signatures of Pop II stars.
1411.4574
Dust destruction rates and lifetimes in the Magellanic clouds
Temim, et al
The nature, composition, abundance, and size distribution of dust in galaxies is determined by the rate at which it is created in the different stellar sources and destroyed by interstellar shocks. Because of their extensive wavelength coverage, proximity, and nearly face-on geometry, the MCs provide a unique opportunity to study these processes in great detail. IN this paper, use the complete sample of SN remnants (SNRs) in the MCs to calculate the lifetime and destruction efficiencies of silicate and carbon dust in these galaxies. Find dust lifetimes of 22pm13 Myr (30pm17Myr) for silicate (carbon) grains in the LMC, and 54pm32 Myr (72pm43 Myr) for silicate (carbon) grains in the SMC. The significantly shorter lifetimes in the MCs, as compared to the MW, are explained as the combined effect of their lower total dust mass, and the fact that the dust-destroying isolated SNe in the MCs seem to preferentially occurring in regions with higher than average dust-to-gas (D2G) mass ratios. Also calculate the SNe rate and the current SFR in the MCs, and use them to derive maximum dust injection rates by asymptotic giant branch stars and core collapse SNe. Find that the injection rates are an order of magnitude lower than the dust destruction rates by the SNRs. This supports the conclusion that, unless the dust destruction rates have been considerably overestimated, most of the dust must be reconstituted from surviving grains in dense molecular clouds. More generally, also discuss the dependence of the dust destruction rate on the local D2G mass ratio, the ambient gas density and metallicity, as well as the application of the results to other galaxies and dust evolution models.
Sunday, November 16, 2014
Day 787
Monday.
1411.3717
Synthetic galaxy images and spectra from the Illustrious simulation
Torrey et al
Method for generating a catalog of 7k synthetic images and 40k integrated spectra of z=0 galaxies from Illustris Sim. Mock data products produced by using stellar population synthesis models to assign SED to each star particle in the galaxies. The resulting synthetic images and integrated SEDs therefore properly reflect the spatial distribution, stellar metallicity distribution, and SFH of the galaxies. From the synthetic data products, it is possible to produce monochromatic or color-composite images, perform SED fitting, classify morphology determine galaxy structural properties, and evaluate the impacts of galaxy viewing angle. The main contribution of this paper is to describe the production, format and composition of the image catalog that makes up the Illustris Sim Observatory. As a demonstration of this resource, derive galactic stellar mass estimates by applying the SED fitting code FAST to the synthetic galaxy products, and compare the derived stellar masses against the true stellar masses from sim. Find from this idealized experiment that systematic biases exist in the photometrically derived stellar mass values that can be reduced by using a fixed metallicity in conjunction with a minimum galaxy age restriction.
1411.3725
Cosmological leverage from the matter power spectrum in the presence of baryon and nonlinear effects
Bielefeld, Huterer, Linder
Take into account uncertainties from ML density fluctuations, (scale dependent) galaxy bias, and baryonic effects. Allowing for substantially model independent uncertainties through separate fit parameters in each wavenumber bin that also allow for z evolution, quantify strong gains in DE and nu mass leverage with increasing maximum wavenumber, despite marginalizing over numerous (up to 125) extra fit parameters. The leverage is due to not only an increased number of modes but, more significantly, breaking of degeneracies beyond the linear regime.
1411.3729
The stability of stellar disks in Milky-Way sized dark matter haloes
Yurin, Springel
Improved methodology to insert live stellar disks into high-res DM sims of MW-sized halos, allowing investigation of the fate of thin stellar disks in the tumultuous environment of CDM structures. Study a set of 8 different halos, drawn from Aquarius simulation project, in which stellar disks are adiabatically grown with a prescribed structure, and then allowed to self-consistently evolve. The initial velocity distribution is set-up in very good equilibrium with the help of the GALIC code. Find that the residual triaxiality of the halos leads to significant disk tumbling, qualitative confirming earlier work. Show that the disk turning motion is unaffected by structural properties of the galaxies such as the presence or absence of a bulge or bar. In typical MW-sized DM halos, expect an average turning of the disks by about 40 degrees between z=1 and 0, over the course of 6 Gyr. Also investigate the impact of the disks on substructures, and conversely, the disk heating rate caused by the DM halo substructures. The presence of disks reduces the central sub halo abundance by about a factor of 2, due to an increase evaporation rate by gravitational shocks from disk passages. Find that substructures are important for heating the outer parts of stellar disks but do not appear to significantly affect their inner parts.
1411.3717
Synthetic galaxy images and spectra from the Illustrious simulation
Torrey et al
Method for generating a catalog of 7k synthetic images and 40k integrated spectra of z=0 galaxies from Illustris Sim. Mock data products produced by using stellar population synthesis models to assign SED to each star particle in the galaxies. The resulting synthetic images and integrated SEDs therefore properly reflect the spatial distribution, stellar metallicity distribution, and SFH of the galaxies. From the synthetic data products, it is possible to produce monochromatic or color-composite images, perform SED fitting, classify morphology determine galaxy structural properties, and evaluate the impacts of galaxy viewing angle. The main contribution of this paper is to describe the production, format and composition of the image catalog that makes up the Illustris Sim Observatory. As a demonstration of this resource, derive galactic stellar mass estimates by applying the SED fitting code FAST to the synthetic galaxy products, and compare the derived stellar masses against the true stellar masses from sim. Find from this idealized experiment that systematic biases exist in the photometrically derived stellar mass values that can be reduced by using a fixed metallicity in conjunction with a minimum galaxy age restriction.
1411.3725
Cosmological leverage from the matter power spectrum in the presence of baryon and nonlinear effects
Bielefeld, Huterer, Linder
Take into account uncertainties from ML density fluctuations, (scale dependent) galaxy bias, and baryonic effects. Allowing for substantially model independent uncertainties through separate fit parameters in each wavenumber bin that also allow for z evolution, quantify strong gains in DE and nu mass leverage with increasing maximum wavenumber, despite marginalizing over numerous (up to 125) extra fit parameters. The leverage is due to not only an increased number of modes but, more significantly, breaking of degeneracies beyond the linear regime.
1411.3729
The stability of stellar disks in Milky-Way sized dark matter haloes
Yurin, Springel
Improved methodology to insert live stellar disks into high-res DM sims of MW-sized halos, allowing investigation of the fate of thin stellar disks in the tumultuous environment of CDM structures. Study a set of 8 different halos, drawn from Aquarius simulation project, in which stellar disks are adiabatically grown with a prescribed structure, and then allowed to self-consistently evolve. The initial velocity distribution is set-up in very good equilibrium with the help of the GALIC code. Find that the residual triaxiality of the halos leads to significant disk tumbling, qualitative confirming earlier work. Show that the disk turning motion is unaffected by structural properties of the galaxies such as the presence or absence of a bulge or bar. In typical MW-sized DM halos, expect an average turning of the disks by about 40 degrees between z=1 and 0, over the course of 6 Gyr. Also investigate the impact of the disks on substructures, and conversely, the disk heating rate caused by the DM halo substructures. The presence of disks reduces the central sub halo abundance by about a factor of 2, due to an increase evaporation rate by gravitational shocks from disk passages. Find that substructures are important for heating the outer parts of stellar disks but do not appear to significantly affect their inner parts.
Saturday, November 15, 2014
Day 786
Friday.
1411.3330
Cosmic dawn: studies of the earliest galaxies and their role in cosmic reionization
Ellis
Recent progress and challenges of the earliest galaxies, when the Universe was <1Byr old. Can they be used as reliable traces of the physics of cosmic reionizaton thereby complementing other, more direct, probes of the evolving neutrality of the IGM? Were SF galaxies the primary agent in the reionization process and what are the future prospects for identifying the earliest systems devoid of chemical enrichment? Ambitious future facilities are under construction of exploring galaxies and the IGM in 6<z<20, corresponding to what is considered the heart of the reionization era. Review that can be inferred about this period from current observations and in the near future with existing facilities, and conclude with a list of key issues where future work is required.
1411.3333
Dust in the circumgalactic medium of low-reshift galaxies
Peek, Ménard, Corrales
Using spectroscopically selected galaxies from SDSS, present a detection of reddening due to dust in the circumgalactic medium of galaxies. Detect the mean change in the colors of "standard crayons" correlated with the presence of FG galaxies at z~0.05 as a function of angular separation. Following Peek&Graves(2010), create standard crayons using passively evolving galaxies corrected for MW reddening and color-redshift trends, leading to a sample with as little as 2% scatter in color. Devise methods to ameliorate possible systematic effects related to the estimation of colors, and find an excess reddening induced by FG galaxies at a level ranging from 10 to 0.5 mmags on scales ranging from 30 kpc to 1 Mpc. Attribute this effect to a large-scale distribution of dust around galaxies similar to the findings of Menard+2010. Find that circumgalactic reddening is a weak function of stellar mass over the range 6e9Msun-6e10Msun and note that this behavior appears to be consistent with recent results on the distribution of metals in the gas phase.
1411.3330
Cosmic dawn: studies of the earliest galaxies and their role in cosmic reionization
Ellis
Recent progress and challenges of the earliest galaxies, when the Universe was <1Byr old. Can they be used as reliable traces of the physics of cosmic reionizaton thereby complementing other, more direct, probes of the evolving neutrality of the IGM? Were SF galaxies the primary agent in the reionization process and what are the future prospects for identifying the earliest systems devoid of chemical enrichment? Ambitious future facilities are under construction of exploring galaxies and the IGM in 6<z<20, corresponding to what is considered the heart of the reionization era. Review that can be inferred about this period from current observations and in the near future with existing facilities, and conclude with a list of key issues where future work is required.
1411.3333
Dust in the circumgalactic medium of low-reshift galaxies
Peek, Ménard, Corrales
Using spectroscopically selected galaxies from SDSS, present a detection of reddening due to dust in the circumgalactic medium of galaxies. Detect the mean change in the colors of "standard crayons" correlated with the presence of FG galaxies at z~0.05 as a function of angular separation. Following Peek&Graves(2010), create standard crayons using passively evolving galaxies corrected for MW reddening and color-redshift trends, leading to a sample with as little as 2% scatter in color. Devise methods to ameliorate possible systematic effects related to the estimation of colors, and find an excess reddening induced by FG galaxies at a level ranging from 10 to 0.5 mmags on scales ranging from 30 kpc to 1 Mpc. Attribute this effect to a large-scale distribution of dust around galaxies similar to the findings of Menard+2010. Find that circumgalactic reddening is a weak function of stellar mass over the range 6e9Msun-6e10Msun and note that this behavior appears to be consistent with recent results on the distribution of metals in the gas phase.
Wednesday, November 12, 2014
Day 785
Thursday.
1411.1758
Where do the 3.5 keV photons come from? A morphological study of the galactic center and of Perseus
Carlson, Jeltema, Profumo
Test the origin of the 3.5 keV line photons by analyzing the morphology of the emission at that energy from the GC and from the Perseus cluster of galaxies. Employ a variety of different templates to model the continuum emission and analyze the resulting radial and azimuthal distribution of the residual emission. Then perform a pixel-by-pixel binned likelihood analysis including line emission templates and dark matter templates and assess the correlation of the 3.5 keV emission with these templates. Conclude that the radial and azimuthal distribution of the residual emission is incompatible with the DM origin for both the Galactic center and Perseus; the Galactic center 3.5 keV line photons trace the morphology of lines at comparable energy, while the Perseus 3.5 keV photons are highly correlated with the cluster's cool core, and exhibit a morphology incompatible with either DM decay or with axion-like particle conversions in the cluster's B-fields. The template analysis additionally allows to set the most stringent constraints to date on lines in the 3.5 keV range from DM decay.
1411.2552
The first light of Mini-MegaTORTORA wide-field monitoring system
Biryukov et al
Describe the first light of the novel 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which is being tested now at Special Astrophysical Observatory on Russian Caucasus. The system is able to observe the sky simultaneously in either wide (~900 sq deg) or narrow (~100 sq deg) FoV, either in clear light or with any combination of color (Johnson B,V or R) polarimetric filters installed, with exposure times ranging from 100 ms to 100 s. The primary goal of the system is the detection of rapid - with sub-second characteristic time-scales - optical transients, but it may be also used for studying the variability of the sky objects on longer time scales.
1411.1511
Galaxy groups
Tully
Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 1e12 Msun are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the DM and DE content of the universe and a crude estimate can be made from the current observations of Omega_m ~0.15 in a flat topology, with a 68% probability of being less than 0.44.
1411.2970
Anomalous coupling of the small-scale structures to the large-scale gravitational growth
Nishimichi, Bernardeau, Taruya
Present the first measurement of NL response of the PS to small variations n the linear counterpart in the context of cosmological LSS formation. While the mode-coupling structure can be explained to a large extent with the standard perturbation theory, show that the coupling of the short-wave modes are however significantly damped away making them contribute only weakly to the growth of long-wave modes. This is the first time such an effect is measured. It is of crucial importance for the use of large-scale cosmological data as probes of fundamental cosmological or physical parameters.
1411.2971
A simple physical model for the gas distribution in galaxy clusters
Patej, Loeb
The dominant baryonic component of galaxy clusters is hot gas whose distribution is commonly probed through X-ray emission arising from thermal bremsstrahlung. The density profile thus obtained has been traditionally modeled with a beta-profile, a simple function with only 3 parameters. However, this model is known to be insufficient for characterizing the range of cluster gas distributions, and attempts to rectify this shortcoming typically introduce additional parameters to increase the fitting flexibility. Use cosmological and physical considerations to obtain a family of profiles for the gas with fewer parameters than the beta-model but which better accounts for observed gas profiles over wide radial intervals.
1411.2976
The galaxy luminosity function at z~6 and evidence for rapid evolution in the bright end from z~7 to 5
Bowler, et al
266 bright Ly-break galaxies at 5.5<z<6.5 in COSMOS and UDS fields: At z~6 the galaxy surface density in the UltraVISTA field exceeds that in the UDS by a factor of ~1.8, indicating strong cosmic variance been between degree-scale fields at z>5. Calculate the bright end of the rest-farm UV LF at z~6. The galaxy number counts are a factor of 2 lower than predicted by the recent LF determination by Bowens+. In comparison to other smaller area studies, find an evolution in the characteristic magnitude between z~5 and z~7 of dM*~0.4 mag, and show that a double power-law or a Schechter function can equally well describe the LF at z=6. Furthermore, the bright end of the LF appears to steepen from z~7 to z~5, which could indicate the onset of mass quenching or the rise of dust obscuration, a conclusion supported by comparing the observed LFs to a range of theoretical model predictions.
1411.3193
Hopfield neural network deconvolution for weak lensing measurement
Nurbaeva, Tewes, Courbin, Meylan
Present a new method to measure the ellipticity of galaxies used in WL surveys. The method makes use of direct deconvolution of the data by the total PSF. Adopt a linear algebra formalism that represents the PSF as a Toeplitz matrix. This allows to solve the convolution equation by applying the HNN iterative scheme. The ellipticity of galaxies in the deconvolved images are then measured using second order moments of the autocorrelation function of the images. This is the first time full image deconvolution is used to measure WL shear. Apply method to the simulated WL data proposed in the GREAT10 challenge and obtain Q=87. This result is obtained after applying image denoting to the data, prior to the deconvolution. The additive and multiplicative biases on the shear PS are then 0.000009 and 0.0357, respectively.
1411.1758
Where do the 3.5 keV photons come from? A morphological study of the galactic center and of Perseus
Carlson, Jeltema, Profumo
Test the origin of the 3.5 keV line photons by analyzing the morphology of the emission at that energy from the GC and from the Perseus cluster of galaxies. Employ a variety of different templates to model the continuum emission and analyze the resulting radial and azimuthal distribution of the residual emission. Then perform a pixel-by-pixel binned likelihood analysis including line emission templates and dark matter templates and assess the correlation of the 3.5 keV emission with these templates. Conclude that the radial and azimuthal distribution of the residual emission is incompatible with the DM origin for both the Galactic center and Perseus; the Galactic center 3.5 keV line photons trace the morphology of lines at comparable energy, while the Perseus 3.5 keV photons are highly correlated with the cluster's cool core, and exhibit a morphology incompatible with either DM decay or with axion-like particle conversions in the cluster's B-fields. The template analysis additionally allows to set the most stringent constraints to date on lines in the 3.5 keV range from DM decay.
1411.2552
The first light of Mini-MegaTORTORA wide-field monitoring system
Biryukov et al
Describe the first light of the novel 9-channel wide-field optical monitoring system with sub-second temporal resolution, Mini-MegaTORTORA, which is being tested now at Special Astrophysical Observatory on Russian Caucasus. The system is able to observe the sky simultaneously in either wide (~900 sq deg) or narrow (~100 sq deg) FoV, either in clear light or with any combination of color (Johnson B,V or R) polarimetric filters installed, with exposure times ranging from 100 ms to 100 s. The primary goal of the system is the detection of rapid - with sub-second characteristic time-scales - optical transients, but it may be also used for studying the variability of the sky objects on longer time scales.
1411.1511
Galaxy groups
Tully
Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 1e12 Msun are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the DM and DE content of the universe and a crude estimate can be made from the current observations of Omega_m ~0.15 in a flat topology, with a 68% probability of being less than 0.44.
1411.2970
Anomalous coupling of the small-scale structures to the large-scale gravitational growth
Nishimichi, Bernardeau, Taruya
Present the first measurement of NL response of the PS to small variations n the linear counterpart in the context of cosmological LSS formation. While the mode-coupling structure can be explained to a large extent with the standard perturbation theory, show that the coupling of the short-wave modes are however significantly damped away making them contribute only weakly to the growth of long-wave modes. This is the first time such an effect is measured. It is of crucial importance for the use of large-scale cosmological data as probes of fundamental cosmological or physical parameters.
1411.2971
A simple physical model for the gas distribution in galaxy clusters
Patej, Loeb
The dominant baryonic component of galaxy clusters is hot gas whose distribution is commonly probed through X-ray emission arising from thermal bremsstrahlung. The density profile thus obtained has been traditionally modeled with a beta-profile, a simple function with only 3 parameters. However, this model is known to be insufficient for characterizing the range of cluster gas distributions, and attempts to rectify this shortcoming typically introduce additional parameters to increase the fitting flexibility. Use cosmological and physical considerations to obtain a family of profiles for the gas with fewer parameters than the beta-model but which better accounts for observed gas profiles over wide radial intervals.
1411.2976
The galaxy luminosity function at z~6 and evidence for rapid evolution in the bright end from z~7 to 5
Bowler, et al
266 bright Ly-break galaxies at 5.5<z<6.5 in COSMOS and UDS fields: At z~6 the galaxy surface density in the UltraVISTA field exceeds that in the UDS by a factor of ~1.8, indicating strong cosmic variance been between degree-scale fields at z>5. Calculate the bright end of the rest-farm UV LF at z~6. The galaxy number counts are a factor of 2 lower than predicted by the recent LF determination by Bowens+. In comparison to other smaller area studies, find an evolution in the characteristic magnitude between z~5 and z~7 of dM*~0.4 mag, and show that a double power-law or a Schechter function can equally well describe the LF at z=6. Furthermore, the bright end of the LF appears to steepen from z~7 to z~5, which could indicate the onset of mass quenching or the rise of dust obscuration, a conclusion supported by comparing the observed LFs to a range of theoretical model predictions.
1411.3193
Hopfield neural network deconvolution for weak lensing measurement
Nurbaeva, Tewes, Courbin, Meylan
Present a new method to measure the ellipticity of galaxies used in WL surveys. The method makes use of direct deconvolution of the data by the total PSF. Adopt a linear algebra formalism that represents the PSF as a Toeplitz matrix. This allows to solve the convolution equation by applying the HNN iterative scheme. The ellipticity of galaxies in the deconvolved images are then measured using second order moments of the autocorrelation function of the images. This is the first time full image deconvolution is used to measure WL shear. Apply method to the simulated WL data proposed in the GREAT10 challenge and obtain Q=87. This result is obtained after applying image denoting to the data, prior to the deconvolution. The additive and multiplicative biases on the shear PS are then 0.000009 and 0.0357, respectively.
Tuesday, November 11, 2014
Day 784
Wednesday.
1411.2590
The suppression of direct collapse black hole formation by soft X-ray irradiation
Inayoshi, Tanaka
The origins of SMBHs: hypothesis is that they grew from >1e5 Msun BHs that formed in the 'direct collapse' of massive gas clouds that have low concentrations of both metals and H2. Such clouds could form in the early (z>10) Universe if pre-galactic gas is irradiated by H2-photodissociating, FUV light from a nearby SF galaxy. The key uncertainties with this scenario are (1) how strong the FUV flux must be to sufficiently suppress the H2 abundance to prevent fragmentation and ordinary SF, and (2) whether the requisite conditions arise frequently enough in nature to account for the observed number density of SMBHs (luminous quasars) at high z. In this work, re-examine the critical FUV flux J_crit that is required to keep H2 photo dissociated and lead to direct collapse. Show that J_crit could be much higher than previously believed if the same FUV sources also produce X-rays, which can work to offset H2 photodissociation by increasing the ionization fraction and promoting H2 formation via electron-catalyzed reactions. Stress that soft (~1 keV) X-rays are far more effective at promoting H2 formation than hard (~10 keV) X-rays. Further, estimate how much soft X-rays can suppress the number density of direct-collapse BHs compared to previous calculations. Find that, even for conservative sets of assumptions, if J_crit is higher than 400-1000 then direct collapse would occur too rarely to explain the observed abundance of z>6 quasars.
1411.2597
On the intermediate-redshift central stellar mass-halo mass relation, and implications for the evolution of the most massive galaxies since z~1
Schankar, et al
The stellar mass-halo mass relation is a key constraint in all SAM, numerical, and semi-empirical models of galaxy formation and evolution. However, its exact shape and redshift dependence remain debated. Several recent works support a relation in the local Universe steeper than previously thought. Based on the comparisons with a variety of data on massive central galaxies, show that this steepening holds up to z~1, for stellar masses M*>2e11Msun. Specifically, find significant evidence for a high-mass end slope of beta>0.35-0.70, instead of the usual beta~0.20-0.30 reported by a number of previous results. When including the independent constraints from the recent BOSS clustering measurements, the data, independent of any systematic errors in stellar masses, tend to favor a model with a very small scatter (<0.15 dex) in stellar mass at fixed halo mass, in the redshift range z<0.8 and for M*>3e11 Msun, suggesting a close connection between massive galaxies and host halos even at relatively recent epochs. Discuss the implications of the results with respect to the evolution of the most massive galaxies since z~1.
1411.2608
Hierarchical probabilistic inference of cosmic shear
Schneider, Hogg, Marshall, Dawson, Meyers, Bard, Lang
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. Present a probabilistic forward model approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of the statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. Derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy preprocess via hierarchical inference with a suitable flexible conditional probability distribution specification. Use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering the algorithm computationally tractable for large surveys. With simple numerical examples, demonstrate the improvements in accuracy from the importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics.
[MBI submission of GREAT3 challenge]
1411.2626
Observational properties of galaxies in overdone and average regions at high redshifts z=6-12
Yajima, Sholsman, Romano-Diaz, Nagamine
Use high-res zoom-in cosmo sims and post-process with panchromatic 3D radiation transfer code to obtain the galaxy UV LF at z=6-12. A rare, heavily overdense region with a 5-sigma density peak evolve at a substantially accelerated pace. Most massive galaxy in this region has grown th M*~8.4e10 Msun by z=6.3, contains a dust mass of Mdust~4.1e8 Msun, and is associated with a very high SFR~745 Msun/yr. At the same time, the most massive object n the 'normal' region has M*~3e8 Msun and Mdust < 1e7 Msun. The attained SFR - M* correlation results in the sSFR slowly increasing with M*. Find that most of the UV stellar radiation in high-z massive galaxies is absorbed by the surrounding dust, and their escape fraction f_esc is low. Galaxies in the average region appear to be more transparent for the UV photons owing to a lower dust column, and they agree with the observed UV LF at z~6-10. Also show that the UV spectra properties of disky galaxies depend significantly upon the viewing angle. Find that the massive galaxies are bright in the IR band due to the dust thermal emission, with L_IR~3.6e12 Lsun at z=6.3, while L_IR<1e11 Lsun for the low-mass galaxies. Therefore, ALMA can probe the massive galaxies in the overdense region up to z~10 with a reasonable integration time. The stellar and dust masses of the most massive galaxy in the overdense region are comparable to those of the sub-millimeter galaxy recently discovered at z=6.3, while the modeled SFR and the sub-millimeter flux fall below the observed one.
1411.2590
The suppression of direct collapse black hole formation by soft X-ray irradiation
Inayoshi, Tanaka
The origins of SMBHs: hypothesis is that they grew from >1e5 Msun BHs that formed in the 'direct collapse' of massive gas clouds that have low concentrations of both metals and H2. Such clouds could form in the early (z>10) Universe if pre-galactic gas is irradiated by H2-photodissociating, FUV light from a nearby SF galaxy. The key uncertainties with this scenario are (1) how strong the FUV flux must be to sufficiently suppress the H2 abundance to prevent fragmentation and ordinary SF, and (2) whether the requisite conditions arise frequently enough in nature to account for the observed number density of SMBHs (luminous quasars) at high z. In this work, re-examine the critical FUV flux J_crit that is required to keep H2 photo dissociated and lead to direct collapse. Show that J_crit could be much higher than previously believed if the same FUV sources also produce X-rays, which can work to offset H2 photodissociation by increasing the ionization fraction and promoting H2 formation via electron-catalyzed reactions. Stress that soft (~1 keV) X-rays are far more effective at promoting H2 formation than hard (~10 keV) X-rays. Further, estimate how much soft X-rays can suppress the number density of direct-collapse BHs compared to previous calculations. Find that, even for conservative sets of assumptions, if J_crit is higher than 400-1000 then direct collapse would occur too rarely to explain the observed abundance of z>6 quasars.
1411.2597
On the intermediate-redshift central stellar mass-halo mass relation, and implications for the evolution of the most massive galaxies since z~1
Schankar, et al
The stellar mass-halo mass relation is a key constraint in all SAM, numerical, and semi-empirical models of galaxy formation and evolution. However, its exact shape and redshift dependence remain debated. Several recent works support a relation in the local Universe steeper than previously thought. Based on the comparisons with a variety of data on massive central galaxies, show that this steepening holds up to z~1, for stellar masses M*>2e11Msun. Specifically, find significant evidence for a high-mass end slope of beta>0.35-0.70, instead of the usual beta~0.20-0.30 reported by a number of previous results. When including the independent constraints from the recent BOSS clustering measurements, the data, independent of any systematic errors in stellar masses, tend to favor a model with a very small scatter (<0.15 dex) in stellar mass at fixed halo mass, in the redshift range z<0.8 and for M*>3e11 Msun, suggesting a close connection between massive galaxies and host halos even at relatively recent epochs. Discuss the implications of the results with respect to the evolution of the most massive galaxies since z~1.
1411.2608
Hierarchical probabilistic inference of cosmic shear
Schneider, Hogg, Marshall, Dawson, Meyers, Bard, Lang
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. Present a probabilistic forward model approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of the statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. Derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy preprocess via hierarchical inference with a suitable flexible conditional probability distribution specification. Use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering the algorithm computationally tractable for large surveys. With simple numerical examples, demonstrate the improvements in accuracy from the importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics.
[MBI submission of GREAT3 challenge]
1411.2626
Observational properties of galaxies in overdone and average regions at high redshifts z=6-12
Yajima, Sholsman, Romano-Diaz, Nagamine
Use high-res zoom-in cosmo sims and post-process with panchromatic 3D radiation transfer code to obtain the galaxy UV LF at z=6-12. A rare, heavily overdense region with a 5-sigma density peak evolve at a substantially accelerated pace. Most massive galaxy in this region has grown th M*~8.4e10 Msun by z=6.3, contains a dust mass of Mdust~4.1e8 Msun, and is associated with a very high SFR~745 Msun/yr. At the same time, the most massive object n the 'normal' region has M*~3e8 Msun and Mdust < 1e7 Msun. The attained SFR - M* correlation results in the sSFR slowly increasing with M*. Find that most of the UV stellar radiation in high-z massive galaxies is absorbed by the surrounding dust, and their escape fraction f_esc is low. Galaxies in the average region appear to be more transparent for the UV photons owing to a lower dust column, and they agree with the observed UV LF at z~6-10. Also show that the UV spectra properties of disky galaxies depend significantly upon the viewing angle. Find that the massive galaxies are bright in the IR band due to the dust thermal emission, with L_IR~3.6e12 Lsun at z=6.3, while L_IR<1e11 Lsun for the low-mass galaxies. Therefore, ALMA can probe the massive galaxies in the overdense region up to z~10 with a reasonable integration time. The stellar and dust masses of the most massive galaxy in the overdense region are comparable to those of the sub-millimeter galaxy recently discovered at z=6.3, while the modeled SFR and the sub-millimeter flux fall below the observed one.
Monday, November 10, 2014
Day 783
Tuesday.
Planetary-Science.com
Punga Mare Waves
Cassini/VIMS observes rough surfaces on Titan's Pnga Mare in specular reflection.
1411.2050
The impact of foregrounds on redshift space distortion measurements with the highly-redshifted 21 cm line
Pober
The highly redshifted 21 cm line of H has become recognized as a unique probe of cosmo from relatively low redshifts (z~1) up through EoR (z~8) and even beyond. To date, most work has focused on recovering the spherically averaged PS of the 21 cm signal, since this approach maximizes the S/N in the initial measurement. However, like galaxy surveys, the 21 cm signal is effected by z space distortion effects, and is inherently anisotropic between the LoS and transverse directions. A full measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter PS from astrophysical effects at high z. However, FGs also have an anisotropic footprint between the LoS and transverse directions: the so-called FG "wedge". Although techniques to subtract FGs are actively being developed, a "FG avoidance" approach of simply ignoring contaminated modes has arguably proven most successful to date. In this work, analyze the effect of this FG anisotropy in recovering the z space distortion signature in 21 cm measurements using a FG avoidance approach at both high and intermediate redshifts. Find the FG wedge corrupts nearly all of the z space signal for even the largest proposed EoR experiments (HERA and the SKA), making cosmological information unrecoverable without FG subtraction. The situation is somewhat improved at lower redshifts, where the z-dependent mapping from observed coordinates to cosmo coordinates significantly reduces the size of the wedge. Using only FG avoidance, find that a large experiment like CHIME can place non-trivial constraints on cosmological parameters.
Planetary-Science.com
Punga Mare Waves
Cassini/VIMS observes rough surfaces on Titan's Pnga Mare in specular reflection.
1411.2050
The impact of foregrounds on redshift space distortion measurements with the highly-redshifted 21 cm line
Pober
The highly redshifted 21 cm line of H has become recognized as a unique probe of cosmo from relatively low redshifts (z~1) up through EoR (z~8) and even beyond. To date, most work has focused on recovering the spherically averaged PS of the 21 cm signal, since this approach maximizes the S/N in the initial measurement. However, like galaxy surveys, the 21 cm signal is effected by z space distortion effects, and is inherently anisotropic between the LoS and transverse directions. A full measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter PS from astrophysical effects at high z. However, FGs also have an anisotropic footprint between the LoS and transverse directions: the so-called FG "wedge". Although techniques to subtract FGs are actively being developed, a "FG avoidance" approach of simply ignoring contaminated modes has arguably proven most successful to date. In this work, analyze the effect of this FG anisotropy in recovering the z space distortion signature in 21 cm measurements using a FG avoidance approach at both high and intermediate redshifts. Find the FG wedge corrupts nearly all of the z space signal for even the largest proposed EoR experiments (HERA and the SKA), making cosmological information unrecoverable without FG subtraction. The situation is somewhat improved at lower redshifts, where the z-dependent mapping from observed coordinates to cosmo coordinates significantly reduces the size of the wedge. Using only FG avoidance, find that a large experiment like CHIME can place non-trivial constraints on cosmological parameters.
Sunday, November 9, 2014
Day 782
Monday.
1411.1755
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies
Singh, Mandelbaum, More
Present results of IA measurements of galaxies on 0.1-200 Mpc/h scales using the LOWZ sample, in 0.16<z<0.36. Extend the existing IA measurements for spectroscopic LRGs to lower luminosities, and show that the luminosity dependence of large-scale IA can be well-dscribed by a power law. Within the limited z and color range of the sample, observe no significant z or color dependence of IA. Measure the halo mass of LOWZ galaxies using gg lensing, and show that the mass dependence of large-scale IA is also well described by a power law. Detect variation in the scale dependence of IA with mass and luminosity, which underscores the need to use flexible templates in order to remove the IA signal. Also study the environment dependence of IA by splitting the sample into field and group galaxies, which are future split into satellite and central galaxies. Show that group central galaxies are aligned with their haloes at small scales and also are aligned with the tidal fields out to large scales. Also detect the radial alignments of satellite galaxies within groups, which results in a null detection of large-scale IA for satellites. These results can be used to construct better IA models for removal of this contaminant of the WL signal.
1411.1761
The search for failed supernovae with the Large Binocular Telescope: first candidates
Gerke, Kochanek, Stanek
Monitoring 27 galaxies within 10 Mpc; Use LBT to search for failed SNe, massive stars that collapse to form a BH without a SN explosion. Yielded 3 successful SNe during the 4 year survey period. Only one candidate approaches the luminosity needed to address the absence of higher mass red supergiant SN progenitors. Under the assumption that further observations show that 1, 2 or 3 candidates are failed SN, the median fractions are f~0.30, 0.40, 0.48 respectively with symmetric 90% confidence limits of 0.07<f<0.062, 0.15<f<0.69, 0.22<f<0.69. If follow up data eliminates these candidates, find an upper limit on the fraction of core collapses leading to a failed SN of f<0.40 at 90% confidence. As the duration of the survey continues to increase, it will have no difficulty constraining the f~20-30% failure rates needed to explain the absence of massive SN progenitors.
1411.1828
Molecular gas and star formation in voids
Das, Saito, Iono, Honey, Ramya
Although void galaxies lie in the most underdense parts of the universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content of SF properties. In this study, searched for molecular gas in 5 void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes of Ha line luminosities. CO(1-0) emission was detected in 4 galaxies and the derived molecular gas masses lie between (1-8e9 Msun. The Ha imaging observations of three galaxies detected in CO emission indicates ongoing SF and the derived SFRs vary between 0.2-1.0 Msun/yr, which is similar to that observed in local galaxies. Study shows that although void galaxies reside in under dense regions, their disks may contain molecular gas and have SFRs similar to galaxies in denser environments.
1411.1755
Intrinsic alignments of SDSS-III BOSS LOWZ sample galaxies
Singh, Mandelbaum, More
Present results of IA measurements of galaxies on 0.1-200 Mpc/h scales using the LOWZ sample, in 0.16<z<0.36. Extend the existing IA measurements for spectroscopic LRGs to lower luminosities, and show that the luminosity dependence of large-scale IA can be well-dscribed by a power law. Within the limited z and color range of the sample, observe no significant z or color dependence of IA. Measure the halo mass of LOWZ galaxies using gg lensing, and show that the mass dependence of large-scale IA is also well described by a power law. Detect variation in the scale dependence of IA with mass and luminosity, which underscores the need to use flexible templates in order to remove the IA signal. Also study the environment dependence of IA by splitting the sample into field and group galaxies, which are future split into satellite and central galaxies. Show that group central galaxies are aligned with their haloes at small scales and also are aligned with the tidal fields out to large scales. Also detect the radial alignments of satellite galaxies within groups, which results in a null detection of large-scale IA for satellites. These results can be used to construct better IA models for removal of this contaminant of the WL signal.
1411.1761
The search for failed supernovae with the Large Binocular Telescope: first candidates
Gerke, Kochanek, Stanek
Monitoring 27 galaxies within 10 Mpc; Use LBT to search for failed SNe, massive stars that collapse to form a BH without a SN explosion. Yielded 3 successful SNe during the 4 year survey period. Only one candidate approaches the luminosity needed to address the absence of higher mass red supergiant SN progenitors. Under the assumption that further observations show that 1, 2 or 3 candidates are failed SN, the median fractions are f~0.30, 0.40, 0.48 respectively with symmetric 90% confidence limits of 0.07<f<0.062, 0.15<f<0.69, 0.22<f<0.69. If follow up data eliminates these candidates, find an upper limit on the fraction of core collapses leading to a failed SN of f<0.40 at 90% confidence. As the duration of the survey continues to increase, it will have no difficulty constraining the f~20-30% failure rates needed to explain the absence of massive SN progenitors.
1411.1828
Molecular gas and star formation in voids
Das, Saito, Iono, Honey, Ramya
Although void galaxies lie in the most underdense parts of the universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content of SF properties. In this study, searched for molecular gas in 5 void galaxies using the NRO. The galaxies were selected based on their relatively higher IRAS fluxes of Ha line luminosities. CO(1-0) emission was detected in 4 galaxies and the derived molecular gas masses lie between (1-8e9 Msun. The Ha imaging observations of three galaxies detected in CO emission indicates ongoing SF and the derived SFRs vary between 0.2-1.0 Msun/yr, which is similar to that observed in local galaxies. Study shows that although void galaxies reside in under dense regions, their disks may contain molecular gas and have SFRs similar to galaxies in denser environments.
Thursday, November 6, 2014
Day 781
Friday.
1410.1884
Detection of galactic center source G2 at 3.8 $¥mu$m during periapse passage
Witzel, et al
Report new observations of the GC source G2 from Keck. G2 is a dusty red object associated with gas that shows tidal interactions as it nears closest approach with the Galaxy's central BH. Observations, conducted as G2 passed through perhaps, were designed to test the proposal that G2 is a 3 M_earth gas cloud. Such a cloud should be tidally disrupted during periapse passage. The data were obtained using the Keck II laser guide star adaptive optics system (LGSAO) and the facility NER camera (NIRC2) through the K' [2.1 um] and L' [3.8 um] broadband filters. Several results emerge from these observations: 1) G2 has survived its closest approach to the BH as a compact, unresolved source at L'; 2) G2's L' brightness measurements are consistent with those over the last decade; 3) G2's motion continues to be consistent with a keplerian model. These results rule out G2 as a pure gas cloud and imply that G2 has a central star. This star has a luminosity of ~30 Lsun and is surrounded by a large (~2.6 AU) optically thick dust shell. The differences between the L' and Br-gamma observations can be understood with a model in which L' and Br-gamma emission arises primarily from internal and external heating, respectively. Suggest that G2 is a binary star merger product and will ultimately appear similar to the B-stars that are tightly clustered around the BH (the so-called S-star cluster).
1411.0709
Discovery of O VII line emitting gas in elliptical galaxies
Pinto, ... Zhang, et al
In the cores of ellipticals, clusters and groups of galaxies, the gas has a cooling time shorter than 1 Gyr. It is possible to probe cooling flows through the detection of Fe XVII and O VII emission lines, but so far O VII was not detected in any individual object. The Reflection Grating Spectrometers on XMM-Newton are currently the only instruments able to detect O VII in extended objects like elliptical galaxies and galaxy clusters. Searched for evidence of O VII through all the archival RGS observations of galaxy clusters, groups and ellipticals focusing on those with core temperatures below 1 keV. Discovered O VII resonance (21.6A) and forbidden (22.1A) lines for the first time in the spectra of individual objects. O VII was detected at a level higher than three sigma in six elliptical galaxies. 3 of which are members of the Virgo cluster, the other are central dominant galaxies of groups, and most of them show evidence of O VI in UV spectra. Detect no significant trend between the Fe XVII and O VII resonance-to-forbidden line ratios, possibly due to the limited statistics. The observed line ratios indicated that the spectra of all these ellipticals are affected by resonance scattering, suggesting low turbulence. Deeper exposures will help to understand whether the Fe XVII and O VII lines are both produced by the same cooling gas or by multi-phase gas. The O VII luminosities correspond to 0.2-2 Msun/yr that agree with the predictions for ellipticals. Such weak cooling rates would not be detected in clusters because their spectra are dominated by the emission of hotter gas and due to their larger distance the expected O VII line flux would be undetectable.
1411.1408
Star formation law at z=2.5 inferred from the electron density of ionized gas
Shimakawa, ... Steidel, et al
In 2<z<3, the physical conditions of the ISM in SF galaxies are likely to be different from those in the local Universe because of lower gaseous metallicities and higher gas fractions, and observations suggest higher electron densities, higher ionization parameters, and harder UV radiation fields may be common. Find that the sSFR and the surface density of SFR (Sigma_SFR) are correlated with the electron density at z=2.5. The Sigma_SFR - n_e relation is likely to be linked to the global SF law (Kennicutt-Schmidt law) where SF activity is regulated by gas density. Moreover, discuss the mode and geometry of SF in those galaxies, based on the correlation between sSFR and Sigma_SFR. Highly SF galaxies (with high sSFR) tend to be characterized by compact dense regions with high values of both n_e and Sigma_SFR.
1411.1409
Galactic outflow and diffuse gas properties at z>=1 using different baryonic feedback models
Barai, et al
Measure and quantify properties of galactic outflows and diffuse gas at z>=1 in cosmo hydro sims ("MUPPI", SNe feedback). At z=2, find outflow velocity and mass outflow rate (Mdot_out) exhibit positive correlations with galaxy mass and with the SFR, but with large scatter. The outflow mass loading factor (eta) is between 0.2-10. The comparison Effective model generates a constant outflow velocity, and a negative correlation on eta with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than 80% over z=1-5. High SF activity at z~2-4 drives strong outflows, causing the positive and steep correlations of velocity and Mdot_out with SFR. The outflow velocity correlation with SFR becomes flatter at z=1, and eta displays a negative correlation with halo mass in massive galaxies. Study demonstrates that both MUPPI and Effective models produce significant outflows at ~1/10 of the viral radius; at the same time shows that the properties of outflows generated can be different from they put speed and mass loading in the Effective model. MUPPI, using local properties of gas in the sub-resolution recipe, is able to develop galactic outflows whose properties correlate with global galaxy properties, and consistent with observations.
1411.1411
On the origin of near-infrared extragalactic background light anisotropy
Zemcov, Smidt, et al
EBL anistotropy traces variationsi n the total production of photons over cosmic history, and may contain faint, extended components missed in galaxy point source surveys. IR EBL fluctuations have been attributed to primordial galaxies and BHs at the EOR, or alternately, intra-halo light (IHL) from stars tidally stripped from their parent galaxies at low redshift. Report new EBL anisotropy measurements from a specialized sounding rocket experiment at 1.1 and 1.6 um. The observed fluctuations exceed the amplitude from known galaxy populations, are inconsistent with EOR galaxies and BHs, and are largely explained by IHL emission. The measured fluctuations are associated with an EBL intensity that is comparable to the BG from known galaxies measured through number counts, and therefore a substantial contribution to the energy contained in photons in the cosmos.
1411.1414
Hubble space telescope combined strong and weak lensing analysis of the CLASH sample: mass and magnification models and systematic uncertainties
Zitrin, et al
HST lensing analysis of the CLASH cluster sample. Identify new multiple-images, improving constraints on cluster inner mass distributions and profiles. Combine SL constraints with WL shape measurements within HST FOV to jointly constrain the mass distributions. Analysis performed in two different common parameterizations (light-traces-mass for galaxies and DM; and an analytic, elliptical NFW form for DM), to provide a better assessment of the underlying systematics - which is most important for deep lensing surveys such as CLASH and the Hubble Frontier Fields, especially when studying high-z magnified objects. Find that the typical (median), relative systematic differences throughout the central FOV are ~40% in the (dimensionless) mass density, kappa, and ~20% in the magnification, mu. For the Einstein radii, find that all typically agree within 10% between the two models, and Einstein masses agree, typically, within ~15%. At larger radii, the total projected, 2D integrated mass profiles of the two models within r~2', differ by ~30%. Stacking the surface-density profiles of the sample from the two methods together, obtain an average slope of d log(Sigma)/d log(r)~-0.64pm0.1, in the radial range [5,350] kpc. Examine the behavior of the average magnification, surface density, and shear differences between the two models, as a function of both the radius and the best-fit values of these quantities, uncovering some interesting trends. Lens models are made publicly available.
1411.1424
Optimal redshift weighting for Baron Acoustic Oscillations
Zhu, Padmanabhan, White
Future BAO surveys will cover very large volumes, covering wide ranges in z. Derive a set of redshift weights to compress the information in the z direction to a small number of modes. Suggest that such a compression preserves almost all of the signal for most cosmologies, while giving high S/N measurements for each combination. Present some toy models and simple worked examples. As an intermediate step, give a precise meaning to the "effective z" of a BAO measurement.
1411.1687
The impact of temperature fluctuations on the large scale clustering f the Ly$\alpha$ forest
Greig, Bolton, Wyithe
Develop SAM for assessing the impact of the large scale IGM temperature fluctuations expected following He II reionization on 3D clustering measurements of the Lya forest. Methodology builds upon the existing large volume, mock Lya forest survey simulations presented by Greig+2011 by including a prescription for a spatially inhomogeneous ionizing background, temperature fluctuations induced by patchy He II photo-heating and the clustering of quasars. This approach enables a dynamic range achieved within the SAM substantially larger than currently feasible with computationally expensive, fully numerical simulations. The results agree well with existing numerical simulations, with large scale temperature fluctuations introducing a scale dependent increase in the spherically averaged 3D Lya forest PS of up to 20-30 % at k~0.02 Mpc-1. Although these large scale thermal fluctuations will not substantially impact upon the recovery of the BAO scale from existing and forthcoming DE spectroscopic surveys, any complete forward modeling of the broadband term in the Lya correlation function will nonetheless require their inclusion.
1410.1884
Detection of galactic center source G2 at 3.8 $¥mu$m during periapse passage
Witzel, et al
Report new observations of the GC source G2 from Keck. G2 is a dusty red object associated with gas that shows tidal interactions as it nears closest approach with the Galaxy's central BH. Observations, conducted as G2 passed through perhaps, were designed to test the proposal that G2 is a 3 M_earth gas cloud. Such a cloud should be tidally disrupted during periapse passage. The data were obtained using the Keck II laser guide star adaptive optics system (LGSAO) and the facility NER camera (NIRC2) through the K' [2.1 um] and L' [3.8 um] broadband filters. Several results emerge from these observations: 1) G2 has survived its closest approach to the BH as a compact, unresolved source at L'; 2) G2's L' brightness measurements are consistent with those over the last decade; 3) G2's motion continues to be consistent with a keplerian model. These results rule out G2 as a pure gas cloud and imply that G2 has a central star. This star has a luminosity of ~30 Lsun and is surrounded by a large (~2.6 AU) optically thick dust shell. The differences between the L' and Br-gamma observations can be understood with a model in which L' and Br-gamma emission arises primarily from internal and external heating, respectively. Suggest that G2 is a binary star merger product and will ultimately appear similar to the B-stars that are tightly clustered around the BH (the so-called S-star cluster).
1411.0709
Discovery of O VII line emitting gas in elliptical galaxies
Pinto, ... Zhang, et al
In the cores of ellipticals, clusters and groups of galaxies, the gas has a cooling time shorter than 1 Gyr. It is possible to probe cooling flows through the detection of Fe XVII and O VII emission lines, but so far O VII was not detected in any individual object. The Reflection Grating Spectrometers on XMM-Newton are currently the only instruments able to detect O VII in extended objects like elliptical galaxies and galaxy clusters. Searched for evidence of O VII through all the archival RGS observations of galaxy clusters, groups and ellipticals focusing on those with core temperatures below 1 keV. Discovered O VII resonance (21.6A) and forbidden (22.1A) lines for the first time in the spectra of individual objects. O VII was detected at a level higher than three sigma in six elliptical galaxies. 3 of which are members of the Virgo cluster, the other are central dominant galaxies of groups, and most of them show evidence of O VI in UV spectra. Detect no significant trend between the Fe XVII and O VII resonance-to-forbidden line ratios, possibly due to the limited statistics. The observed line ratios indicated that the spectra of all these ellipticals are affected by resonance scattering, suggesting low turbulence. Deeper exposures will help to understand whether the Fe XVII and O VII lines are both produced by the same cooling gas or by multi-phase gas. The O VII luminosities correspond to 0.2-2 Msun/yr that agree with the predictions for ellipticals. Such weak cooling rates would not be detected in clusters because their spectra are dominated by the emission of hotter gas and due to their larger distance the expected O VII line flux would be undetectable.
1411.1408
Star formation law at z=2.5 inferred from the electron density of ionized gas
Shimakawa, ... Steidel, et al
In 2<z<3, the physical conditions of the ISM in SF galaxies are likely to be different from those in the local Universe because of lower gaseous metallicities and higher gas fractions, and observations suggest higher electron densities, higher ionization parameters, and harder UV radiation fields may be common. Find that the sSFR and the surface density of SFR (Sigma_SFR) are correlated with the electron density at z=2.5. The Sigma_SFR - n_e relation is likely to be linked to the global SF law (Kennicutt-Schmidt law) where SF activity is regulated by gas density. Moreover, discuss the mode and geometry of SF in those galaxies, based on the correlation between sSFR and Sigma_SFR. Highly SF galaxies (with high sSFR) tend to be characterized by compact dense regions with high values of both n_e and Sigma_SFR.
1411.1409
Galactic outflow and diffuse gas properties at z>=1 using different baryonic feedback models
Barai, et al
Measure and quantify properties of galactic outflows and diffuse gas at z>=1 in cosmo hydro sims ("MUPPI", SNe feedback). At z=2, find outflow velocity and mass outflow rate (Mdot_out) exhibit positive correlations with galaxy mass and with the SFR, but with large scatter. The outflow mass loading factor (eta) is between 0.2-10. The comparison Effective model generates a constant outflow velocity, and a negative correlation on eta with halo mass. The number fraction of galaxies where outflow is detected decreases at lower redshifts, but remains more than 80% over z=1-5. High SF activity at z~2-4 drives strong outflows, causing the positive and steep correlations of velocity and Mdot_out with SFR. The outflow velocity correlation with SFR becomes flatter at z=1, and eta displays a negative correlation with halo mass in massive galaxies. Study demonstrates that both MUPPI and Effective models produce significant outflows at ~1/10 of the viral radius; at the same time shows that the properties of outflows generated can be different from they put speed and mass loading in the Effective model. MUPPI, using local properties of gas in the sub-resolution recipe, is able to develop galactic outflows whose properties correlate with global galaxy properties, and consistent with observations.
1411.1411
On the origin of near-infrared extragalactic background light anisotropy
Zemcov, Smidt, et al
EBL anistotropy traces variationsi n the total production of photons over cosmic history, and may contain faint, extended components missed in galaxy point source surveys. IR EBL fluctuations have been attributed to primordial galaxies and BHs at the EOR, or alternately, intra-halo light (IHL) from stars tidally stripped from their parent galaxies at low redshift. Report new EBL anisotropy measurements from a specialized sounding rocket experiment at 1.1 and 1.6 um. The observed fluctuations exceed the amplitude from known galaxy populations, are inconsistent with EOR galaxies and BHs, and are largely explained by IHL emission. The measured fluctuations are associated with an EBL intensity that is comparable to the BG from known galaxies measured through number counts, and therefore a substantial contribution to the energy contained in photons in the cosmos.
1411.1414
Hubble space telescope combined strong and weak lensing analysis of the CLASH sample: mass and magnification models and systematic uncertainties
Zitrin, et al
HST lensing analysis of the CLASH cluster sample. Identify new multiple-images, improving constraints on cluster inner mass distributions and profiles. Combine SL constraints with WL shape measurements within HST FOV to jointly constrain the mass distributions. Analysis performed in two different common parameterizations (light-traces-mass for galaxies and DM; and an analytic, elliptical NFW form for DM), to provide a better assessment of the underlying systematics - which is most important for deep lensing surveys such as CLASH and the Hubble Frontier Fields, especially when studying high-z magnified objects. Find that the typical (median), relative systematic differences throughout the central FOV are ~40% in the (dimensionless) mass density, kappa, and ~20% in the magnification, mu. For the Einstein radii, find that all typically agree within 10% between the two models, and Einstein masses agree, typically, within ~15%. At larger radii, the total projected, 2D integrated mass profiles of the two models within r~2', differ by ~30%. Stacking the surface-density profiles of the sample from the two methods together, obtain an average slope of d log(Sigma)/d log(r)~-0.64pm0.1, in the radial range [5,350] kpc. Examine the behavior of the average magnification, surface density, and shear differences between the two models, as a function of both the radius and the best-fit values of these quantities, uncovering some interesting trends. Lens models are made publicly available.
1411.1424
Optimal redshift weighting for Baron Acoustic Oscillations
Zhu, Padmanabhan, White
Future BAO surveys will cover very large volumes, covering wide ranges in z. Derive a set of redshift weights to compress the information in the z direction to a small number of modes. Suggest that such a compression preserves almost all of the signal for most cosmologies, while giving high S/N measurements for each combination. Present some toy models and simple worked examples. As an intermediate step, give a precise meaning to the "effective z" of a BAO measurement.
1411.1687
The impact of temperature fluctuations on the large scale clustering f the Ly$\alpha$ forest
Greig, Bolton, Wyithe
Develop SAM for assessing the impact of the large scale IGM temperature fluctuations expected following He II reionization on 3D clustering measurements of the Lya forest. Methodology builds upon the existing large volume, mock Lya forest survey simulations presented by Greig+2011 by including a prescription for a spatially inhomogeneous ionizing background, temperature fluctuations induced by patchy He II photo-heating and the clustering of quasars. This approach enables a dynamic range achieved within the SAM substantially larger than currently feasible with computationally expensive, fully numerical simulations. The results agree well with existing numerical simulations, with large scale temperature fluctuations introducing a scale dependent increase in the spherically averaged 3D Lya forest PS of up to 20-30 % at k~0.02 Mpc-1. Although these large scale thermal fluctuations will not substantially impact upon the recovery of the BAO scale from existing and forthcoming DE spectroscopic surveys, any complete forward modeling of the broadband term in the Lya correlation function will nonetheless require their inclusion.
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