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Thursday.
1509.08923
The metal and dust yields of the first massive stars
Marassi, et al
Quantify the role of Pop III core-collapse SNe as the first cosmic dust polluters. Starting from a homogeneous set of stellar progenitors with masses in the range [13-80] Msun, find that the mass and composition of newly formed dust depend on the mixing efficiency of the ejecta and the degree of fallback experienced during the explosion. For standard Pop III SNe, whose explosions are calibrated to reproduce the average elemental abundances of Galactic halo stars with [Fe/H]<-2.5, between 0.18 and 3.1 Msun (0.39-1.76 Msun) of dust can form in uniformly mixed (unmixed) ejecta, and the dominant grain species are silicates. Also investigate dust formation in the ejecta of faint Pop III SN, where the ejecta experience a strong fallback. By examining a set of models, tailored to minimize the scatter with the abundances of carbon-enhanced Galactic halo stars with [Fe/H]<-4, find that amorphous carbon is the only grain species that forms, with masses in the range 2.7e-3 - 0.27 Msun (7.5e-4 - 0.11 Msun) for uniformly mixed (unmixed) ejecta models. Finally for all the models, estimate the amount and composition of dust that survives the passage of the reverse shock, and find that, depending on circumstellar medium densities, between 3 and 50% (10-80%) of dust produced by standard (faint) Pop III SNe can contribute to early dust enrichment.
1509.08930
Weak-lensing mass calibration of the Atacama cosmology telescope equatorial Sunyaev-Zeldovich cluster sample with the Canada-France-Hawaii Telescope Stripe 82 survey
Battaglia, Leauthaud, Miyatake, et al
Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constraint cosmo params. Present WL mass measurements from CFHT S82 survey for galaxy clusters selected through their high S/N tSZ signal measured with ACT. The average WL mass is (4.8±0.8)e14 Msun, consistent with the tSZ mass estimate of (4.70±1.0)e14 Msun which assumes a universal pressure profile for the cluster gas. Results are consistent with previous WL measurements of tSZ-detected clusters from the Plank satellite. When comparing the results, estimate the Eddington bias correction for the sample intersection of Planck andWL clusters which was previously neglected.
1509.08933
Unbiased methods for removing systematics from galaxy clustering measurements
Elsner, Leistedt, Peiris
Measuring the angular clustering of galaxies as a function of redshift is a powerful method for tracting information from the 3D galaxy distribution. The precision of such measurements will dramatically increase with ongoing and future wide-field galaxy surveys. However, these are also increasingly sensitive to observational and astrophysical contaminants. Study the statistical properties of 3 methods proposed for controlling such systematics - template subtraction, basic mode projection, and extended mode projection - all of which make use of externally supplied template maps, designed to characterize and capture the spatial variations of potential systematic effects. Based on a detailed mathematical analysis, and in agreement with simulations, find that the template subtraction method in its original formulation returns biased estimates of the galaxy angular clustering. Derive closed-form expressions that should be used to correct results for this shortcoming. Turning to the basic mode projections algorithm, prove it to be free of any bias, whereas it is concluded that results computed with extended mode projection are biased. Within a simplified setup, derive analytical expressions for the bias and discuss the options for correcting it in more realistic configurations. Common to all 3 methods is an increased estimator variance induced by the cleaning process, albeit at different levels. These results enable unbiased high-precision clustering measurements in the presence of spatially-varying systematics, and essential step towards realizing the full potential of current and planned galaxy surveys.
Wednesday.
1509.08473
A unified multi-wavelength model of galaxy formation
Lacey, Baugh, Frenk, Benson, Bower, Cole, Gonzalez-Perez, Helly, Lagos, Mitchell
Present a new version of the GALFORM galaxy formation SAM. This brings together several previous developments of GALFORM into a single unified model, including a different IMF in quiescent SF and in starbursts, feedback from AGN suppressing gas cooling in massive haloes, and a new empirical SF law in galaxy disks based on their molecular gas content. In addition, update the cosmology, introduce a more accurate treatment of dynamical friction acting on satellite galaxies, and update the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band LF and stellar MF, and the number counts and redshift distribution of sub-mm galaxies selected at 850 mu. This was not previously achieved by a single physical model within the LCDM framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is tested against a wide variety of observational data covering wavelengths form the far-UV to sub-mm and redshifts from z=0 to 6, and is found to be generally successful. These observations include the optical and near-IR LF, HI MF, Tully-Fisher relation, fraction of early type galaxies, metallicity-luminosity relation and size-luminosity relation at z=0, as well as far-IR number counts, and far-UV LFs at z~3-6.
Tuesday.
Astrosat Launches
It will observed the universe n the optical, UV, low and high energy X-ray regions of the EM spectrum. The 5 payloads of Astrosat will study star birth regions and black holes.
1509.07863
Abiotic O$_{2}$ levels on planets around F, G, K, and M stars: possible false positives for life?
Harman et al
Of the countless number of chemical species terrestrial life produces, only a few have the distinct spectral features and the necessary atmospheric abundance to be detectable. The easiest of these species to observe in Earth's atmosphere is O2 (and its photochemical byproduct, O3). But O2 can also be produced abiotically by photolysis of CO2, followed by recombination of O atoms with each other. CO is produced in stoichiometric proportions. Whether O2 and CO can accumulate to appreciable concentrations depends on the ratio of far-UV to near-UV radiation coming from the planet's parent star and on what happens to these gases when they dissolve in a planet's oceans. Using a 1-D photochemical model, demonstrate that O2 derived from CO2 photolysis should not accumulate to measurable concentrations on planets around F- and G-type stars. K-star, and especially M-star planets, however, may build up O2 because of the low near-UV flux from their parent stars, in agreement with some previous studies. On such planets, a 'false positive' for life is possible if recombination of dissolved CO and O2 in the oceans is slow and if other O2 sinks (e.g., reduced volcanic gases or dissolved ferrous iron) are small. O3, on the other hand, could be detectable at UV wavelengths (lambda<300nm) for a much broader range of boundary conditions and stellar types.
1509.07870
The galaxy luminosity function in groups and clusters: the faint-end upturn and the connection to the field luminosity function
Lan, Ménard, Mo
Characterize the LF of galaxies residing in z~0 groups and clusters over the broadest ranges of luminosity and mass reachable by SDSS. The measurements cover 4 orders of magnitude in luminosity, down to about Mr=-12 mag or L=1e7Lsun, and 3 orders of magnitude in halo mass, from 1e12 to 1e15 Msun. Find a characteristic scale, Mr~-18mag or L~1e9Lsun, below which the slope of the LF becomes systematically steeper. This trend is present for all halo masses and originates mostly from red satellite galaxies. The ubiquitous presence of this faint-end upturn suggests that it is formation, rather than halo-specific environmental effect, that plays a major role in regulating the stellar masses of faint satellites. Show that the observed LFs of satellite galaxies can be described in a simple manner by a double Schechter function with amplitudes scaling with halo mass over the entire range of observables. Combining these conditional LFs with the DM halo MF, can accurately recover the entire field LF measured over 10 visual magnets. This decomposition reveals that the field LF is dominated by satellite galaxies at magnitudes fainter than -18 mag or L<1e9 Lsun and central galaxies above. Find that the LFs of blue and red satellite galaxies show distinct shapes and present estimates of the stellar MF as a function of halo mass and galaxy type. Finally, using a simple model, show that the average number and the faint-end slopes of blue and red satellite galaxies can be interpreted in terms of their formation history, with 2 distinct modes separated by some characteristic time.
1509.07917
The SDSS-III BOSS quasar lens survey: discovery of thirteen gravitationally lensed quasars
More, Oguri, Kayo, et al
Report the discovery of 13 confirmed 2 image quasar lenses from a systematic search for gravitationally lensed quasars in SDSS-III BOSS. Adopted a methodology similar to SQLS (SDSS Quasar Lens Search). In addition to the confirmed lenses, report 11 quasar pairs with small angular separations (<~2") confirmed from spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs~4.8 is the one of the highest z multiply imaged quasars found to date. Furthermore, there are over 50 good lens candidates yet to be followed up. Owing to the heterogenous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.
1509.08046
Quiescent luminous red galaxies (LRGs) as cocsmic chronometers: on the significance of the mass and environmental dependence
Liu, et al
The environmental effects may limit the use of the LRGs as cosmic chronometers. Find that there is no apparent dependence of the mean age and the SFH of quiescent LRGs on their environment, while the ages of those quiescent LRGs weakly depend on their mass. Compare the SFHs of the SDSS LRGs with those obtained from a semi-analytical galaxy formation model, and find that they are roughly consistent with each other if considering the errors in the STARLIGHT (an SPS code)-derived ages. Find that a small fraction of later SF in LRGs leads to a systematic overestimation (~28%) of the Hubble constant by the differential age method, and systematic errors in STARLIGHT-derived ages may lead to underestimation (~16%) of the Hubble constant. There errors can be corrected by a detailed study of the man SFH of those LRGs and by calibrating the STARLIGHT-derived ages with those obtained independently by other methods. The environmental effects are not significant on the age estimates of 'quiescent' LRGs, and the 'quiescent' LRGs as a population can be securely used as comic chronometers.
Monday.
1509.07498
Void alignment and density profile applied to measuring cosmological parameters
Dai
Study the orientation and density profiles of the cosmological voids with SDSS10 data. Using voids to test Alcock-Paczynski effect has been proposed and tested in both simulations and actual SDSS data. Previous observations imply that there exist an empirical stretching factor which plays an important role in the voids' orientation. Simulations indicate that this empirical stretching factor is caused by the void galaxies' peculiar velocities. Recently Hamaus et al. found that voids' density profiles are universal and their average velocities satisfy linear theory very well. In this article, first confirm that the stretching effect exists using independent analysis. Then apply the universal density profile to measure the cosmo parameters. Find that the void density profile can be a tool to measure the cosmo parameters.
1509.07501
Cosmological hints of modified gravity?
Di Valentino, Melchiorri, Silk
The recent measurements of CMB temperature and polarization anisotropies made by Planck have provided impressive confirmation of the LCDM cosmo model. However, interesting hints of slight deviations from LCDM have been found, including a 95% CL preference for a "modified gravity" structure formation scenario. IN this paper, confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called A_lens anomaly in the CMB angular spectrum, and constraints the amplitude of matter density fluctuations to sigma8=0.815±0.05, in better agreement with WL constraints. Moreover, find a lower value for the reionization optical depth of tau=0.059±0.020 (to be compared with the value of tau=0.079±0.017 obtained in the standard scenario), more consistent with recent optical and UV data. Check the stability of this result by considering possible degeneracies with other parameters, including the neutrino effective number, the running of the spectral index and the amount of primordial He. The indication for modified gravity is still present at ~95% CL, and could become more signifiant if lower values of tau were to be further confirmed by future cosmo and astrophysical data.
1509.07506
Density jumps near the viral radius of galaxy clusters
Patej, Loeb
Recent simulations have indicated that the DM haloes of galaxy clusters should feature steep density jumps near the viral radius. Since the member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show such a feature as well. Examine the potential of current datasets to test this prediction by selecting cluster members for a sample of 56 low-z (0.1<z<0.3) galaxy clusters, constructing their projected number density profiles, and fitting them with two profiles, one with a steep density jump and one without. Additionally, investigate the presence of a jump using a non-parmaeteric spline approach. Find that some of these clusters show strong evidence for a model with a density jump. Discuss avenues for further analysis of the density jump with future datasets.
1509.07585
Probing promordial non-Gaussianity consistency relation with galaxy surveys
Yamauchi, Takahashi
With a radio continuum galaxy survey by SKA, a photometric galaxy survey by Euclid and their combination, forecast future constraints on primordial non-Gaussianity. Focus on the potential impact of local-type higher-order nonlinear parameters on the parameter estimation and particularly the confirmation of the inflationary consistency inequality Non-standard inflationary models, such as multi-field models, introduce the scale-dependent stochastic clustering of galaxies on large scales, which is a unique probe of mechanism for generating primordial density fluctuations. The Fisher matrix analysis indicates that a deep and wide survey provided by SKA is more advantageous to constrain tau_NL, while Euclid has a strong constraining power for f_NL due to the redshift information, suggesting that the joint analysis between them are quite essential to break the degeneracy between f_NL and tau_NL. The combination of full SKA and Euclid will achieve the precision level needed to confirm the consistency inequality even for f_NL~0.9 and tau_NL~8, though it is still hard for a single survey to confirm it when f_NL<1.5.
1509.07649
Cosmology with strong lensing systems
Cao, et al
Assemble a catalog of 118 SL systems from SLACS, BELLS, LSD and SL2S surveys and use them to constrain the cosmic EoS. In particular, consider 2 cases of DE phenomenology: XCDM model where DE is modeled by a a fluid with constant w EoS parameter and in Chevalier-Polanski-Linder (CPL) parameterization where w is allowed to evolve with redshift: w(z)=w0+w1(z/(1+z)). Assume spherically symmetric mass distribution in lensing galaxies, but relax the rigid assumption of SIS model in favor to more general power-law index gamma, also allowing it to evolve with redshifts gamma(z). Results from the XCDM cosmology show the agreement with values (concerning both w and gamma parameters) obtained by other authors. Go further and constrain the CPL parameters jointly with gamma(z). The resulting confidence regions for the parameters are much better than those obtained with a similar method in the past. They are also showing a trend of being complementary to the SNIa data. Analysis demonstrate that SL systems can be used to probe cosmo parameters like the cosmic EoS for DE. Moreover, they have a potential to judge whether the cosmic EoS evolved with time or not.
Friday.
1509.07121
Photometric redshifts and clustering of emission line galaxies selected jointly by DES and eBOSS
Jouvel, et al
Present the results of the first test plates of eBOSS. This paper focuses on the emission line galaxies (ELG) population targeted from DES photometry. Analyze the success rate, efficiency, redshift distribution, and clustering properties of the targets. From the 9000 spectroscopic redshifts targeted, 4600 have been selected from the DES photometry. The total success rate for redshifts between 0.6 and 1.2 is 71% and 68% respectively for a bright and faint, on average more distant, samples including redshifts measured from a single strong emission line. Find a mean redshift of 0.8 and 0.87, with 15 and 13% of unknown redshifts respectively for the bright and faint samples. In the redshift range 0.6<z<1.2, for the most secure spectroscopic redshifts, the mean redshift for the bright and faint sample is 0.85 and 0.9 respectively. Star contamination is lower than 2%. Measure a galaxy bias averaged on scales of 1 and 10 Mpc/h of 1.72±0.1 for the bright sample end of 1.78±0.12 for the faint sample. The error on the galaxy bias have been obtained propagating the errors in the correlation function to the fitted parameters. This redshift evolution for the galaxy bias is in agreement with theoretical expectations for a galaxy population with MB-5logh<-21.0. Note that biasing is derived from the galaxy clustering relative to a model for the mass fluctuations. Investigate the quality of the DES photometric redshifts and find that the outlier fraction can be reduced using a comparison between template fitting and neural network, or using a random forest algorithm.
1509.07124
The spectral SN-GRB connrection: systematic spectral comparisons between type Ic supernovae, broad-lined Type Ic supernovae with and without Gamma-ray bursts
Modjaz, Liu, Bianco, Graur
Present the first systematic investigation of spectral properties of 17 SNe Ic, 10 broad-lined SNe Ic (SNe Ic-bl) without observed GRBs and 10 SNe Ic-bl with GRBs (SN-GRBs) as a function of time in order to probe their explosion conditions and progenitors. Analyze a total of 396 spectra, which were drawn from published spectra of individual SNe as well as from the densely time-sampled spectra data of Modjaz+2014. In order to quantify the diversity of the SN spectra as a function of SN subtype, construct average spectra of SNe Ic, SNe Ic-bl without GRBs, and SNe Ic-bl with GRBs, along with standard deviation and maximum deviation contours. Find that SN1994I is not a typical SN Ic, in contrast to common belief, while the spectra of SN 1998bw/GRB 980425 are representative of mean spectra of SNe Ic-bl. Measure the ejecta absorption and width and find that SNe Ic-bl with GRBs, on average, have quantifiably higher absorption velocities, as well as broader line widths than SNe without observed GRBs. Interpret this to indicate that SNe Ic-bl without observed GRBs may have had lower energy, chocked jets that imparted lower velocities to the SN ejecta. Moreover, address the He-problem in SNe Ic-bl, namely whether the puzzling lack of He lines in SN Ic-bl spectra could be due to their He lines being too broadened by the high velocities present, and thus smeared out. Show that the absence of clear He lines in optical spectra of all SNe Ic-bl, and in particular of SN-GRBs, is not due to them being too smeared out. This implies that the progenitor stars of SN-GRBs are probably He-free, in addition to being H-free, which puts strong constraints on the stellar evolutionary paths needed to produce such SN-GRB progenitor stars at the observed low metallicities.
Thursday.
1509.06750
3D weak lensing with spin wavelets on the ball
Leistedt, McEwen, Kitching, Peiris
Construct the spin flaglet transform, a wavelet transform to analyse spin signals in 3D. Spin flaglets can probe signal content localised simultaneously in space and frequency and are separable so that their angular and radial properties can be controlled independently. They are particularly suited to analyzing of cosmo observations such as WL. Such observations have a unique 3D geometrical setting since they are natively made on the sky, have spin angular symmetries, and are extended in the radial direction by additional distance or redshift information. Flaglets are constructed in the harmonic space defined by the Fourier-Laguerre transform, previously defined for scalar functions and extended here to signals with spin symmetries. Thanks to various sampling theorems, both the Fourier-Laguerre and flageolet transforms are theoretically exact when applied to band-limited signals. In other words, in numerical computations, the only loss of information is due to the finite representation of floating point numbers. Develop a 3D framework relating the WL PS to covariances of flaglet coefficients. Suggest that the resulting novel flaglet WL estimator offers a powerful alternative to common 2D and 3D approaches to accurately capture cosmological information. While standard WL analyses focus on either real or harmonic space representations (i.e., correlation functions of Fourier-Bessel power spectra, respectively), a wavelet approach inherits the advantages of both techniques, where both complicated sky coverage and uncertainties associated with the physical modeling of small scales can be handled effectively. The codes to compute the Fourier-Laguerre and flaglet transforms are made publicly available.
1509.06756
Galaxy and mass assembly (GAMA): the wavelength dependence of galaxy structure versus redshift and luminosity
Kennedy et al
Study how the sizes and radial profiles of galaxies vary with wavelength, by fitting Sersic functions simultaneously to imaging in 9 optical and NIR bands. To quantify the wavelength dependence of effective radius, use the ratio R of measurements in two restframe bands. The dependence of service index on wavelength N is computed correspondingly. Vulcani+2014 have demonstrated that different galaxy populations present sharply contrasting behavior in terms of R and N. Study the luminosity dependence of this result. Find that at higher luminosities, early-type galaxies display a more substantial decrease in effective radius with wavelength, whereas late-types present a more pronounced increase in Sersic index. The structural contrast between types thus increases with luminosity. By considering samples at different redshifts, demonstrate that lower data quality reduces the apparent difference between the main galaxy populations. However, the conclusions remain robust to this effect. Show that accounting for different redshift and luminosity selections partly reconciles the size variation measured by Vulcani+ with the weaker trends found by other recent studies. Dividing galaxies by visual morphology confirms the behavior inferred using morphological proxies, although the sample size is greatly reduced. Finally, demonstrate that varying dust opacity and disc inclination can account for features of the joint distribution of R and N for late-type galaxies. However, dust does not appear to explain the highest values of R and N. The Bulge-disc nature of galaxies must also contribute to the wavelength-dependence of their structure.
1509.06758
Mapping stellar content to dark matter haloes. II. Halo mass is the main driver of galaxy quenching
Zu, Mandelbaum
Develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and gg lensing of red and blue galaxies in SDSS. Building on the iHOD framework, consider two quenching scenarios: 1) a halo quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellite; and 2) a hybrid quenching model in which the quenched fraction of galaxies depends on their stellar mass while the satellite quenching has an extra dependence on halo mass. The two best-fit models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above 1e11 Msun/h^2. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct WL measurements of locally births galaxies. Models in which quenching is not tied to halo mass, including an age-matching model in which galaxy color depends on halo age at fixed M*, fail to reproduce the observed halo mass for massive blue centrals. Find similar critical halo masses responsible for the quenching of centrals and satellites (~1.5e12 Msun/h^2), hinting at a uniform quenching mechanism for both, e.g., the viral shock-heating of infalling gas. The success of the iHOD halo quenching model provides strong evidence that the physical mechanism that quenches star formation in galaxies is tied principally to the masses of their dark matter halos rather than the properties of their stellar components.
1509.06762
Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing
Mandelbaum, Wang, Zu, White, Henriques, More
Use gg lensing to study the DM haloes surrounding a sample of locally bright galaxies (LBGs) selected from SDSS. Measure mean halo mass as a function of the stellar mass and color of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their halos, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, 10.3<log(M*/Msun)<11.6, find that passive central galaxies have haloes that are at least twice as massive as those of star-forming objects of the same stellar mass. The significance of this effect exceeds 3 sigma for log(M*/Msun)>10.7. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG color. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying the mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type-dependence.
1509.06877
The distribution function of the Galaxy's dark halo
Binney, Piffl
Starting from the hypothesis that the Galaxy's dark halo responded adiabatically to the infall of baryons, construct a self-consistent dynamical model of the Galaxy that satisfies a large number of observations, including measurements of gas terminal velocities and masers, the kinematics of a 180k giant stars from the RAVE survey, and star count data from the SDSS. The stellar disc and the dark halo are both specified by distribution functions (DFs) of the action integrals. The model is obtained by extending the work of Piffle Penoyre + Binney (2015) from the construction of a single model to a systematic search of model space. Whereas the model of PIffl+ violated constraints on the terminal-velocity curve, the model respects these constraints by adopting a long scale length R_d=3.6 kpc for the thin and thick discs. The models is, however, inconsistent with the measured optical depth for microlensing of bulge stars because it attributes too large a fraction of the density at R<~3 kpc to dark matter rather than stars. Moreover, it now seems likely that the thick disc's sale-length is significantly shorter than the model implies. Shortening this scale-length would cause the constraints from the rotation curve to be violated anew. Conclude that adiabatic compression of our Galaxy's dark halo can be ruled out.
Wednesday.
1509.06371
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the correlation function of LOWZ and CMASS galaxies in Data Release 12
Cuesta et al
BAO signal in CMASS and LOWZ samples from DR12 of BOSS: total volume probed is 14.5 Gpc^3, a 10% increment from DR11. Analysis of the spherically averaged correlation function, infer a distance to z=0.57 of D_V(z)r^fid_d/r_d = 2028±19 Mpc and a distance to z=0.32 of D_V(z)r^fid_d/r_d = 1263±21 Mpc assuming a cosmology in which r^fid_d = 147.10 Mpc. From the anisotropic analysis, find an angular diameter distance to z=0.57 of D_A(z)r^fid_d/r_d = 1401±19 Mpc and a distance to z=0.32 of 981±20 Mpc, a 1.4% and 2.0% measurement respectively. These cosmic distance scale constraints are in excellent agreement with a LCDM model with cosmo params released by Planck 2015.
1509.06373
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: BAO measurement from the LOS-dependent power spectrum of DR12 BOSS galaxies
Gil-Marín, Percival, Cuesta, et al
Present an anisotropic analysis of the BAO scale in the final DR12 BOSS data release. Independently analyse the LOWZ and CMASS galaxy samples: the LOWZ sample contains 361k galaxies with an effective z of z_LOWZ=0.32, and the CMASS sample consists of 777k galaxies with an effective redshift of z_CMASS=0.57. Extract the BAO peak position from the monopole power spectrum amount, alpha_0, and from the mu^2 moment, alpha^2. Report H(z_LOWZ)r_s(z_d)=(11.64±0.62)e3 km/s, and D_A(z_LOWZ)/r_s(z_d)=0.85±0.17 with a cross-correlation coefficient of r_HD_A=0.42, for the LOWZ sample; and H(z_CMASS)r_s(z_d)=)14.56±0.38)e3 km/s and D_A(z_CMASS)/r_s(z_d)=9.42±0.13 with a cross-correlation coefficient of r_HD_A=0.51, for the CMASS sample. Combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same dataset [see above] and report the consensus values: H(z_LOWZ)r_s(z_d)=(11.64±0.70)e3 km/s and D_A(z_LOWZ)/r_s(z_d)=6.76±0.15 with r_HD_A=0.35 for the LOWZ sample; and H(z_CMASS)r_s(z_d)=(14.66±0.42)e3 km/s and D_A(z_CMASS)/r_s(z_d)=9.47±0.13 with r_HD_A=0.54 for the CMASS sample.
1509.06376
Detection effects of filaments on galaxy properties in the Sloan Digital Sky Survey III
Chen, Ho, Mandelbaum, Bahcall, et al
Study the effects of filaments on galaxy properties on SDSS DR12 using filaments from the 'Cosmic Web Reconstruction' catalogue (Chen+2015), a publicly available filament catalogue for SDSS. Since filaments are tracers of medium-to-high density regions, expect that galaxy properties associated with the environment are dependent on the distance to the nearest filament. Analysis demonstrates a red galaxy or a high-mass galaxy tend to reside closer to filaments than a blue or low-mass galaxy. After adjusting the effect from stellar mass, on average, late-forming galaxies or large galaxies have a shorter distance to filaments than early-forming galaxies or small galaxies. For the Main galaxy sample, all signals are very significant (>5 sigma). For the LOWZ and CMASS samples, most of the signals are significant (with >3 sigma). The filament effects observed persist until z=0.7 (the edge of the CMASS sample). Comparing the results to those using the galaxy distances from redMaPPer galaxy clusters as a reference, find a similar result between filaments and clusters. Findings illustrate the strong correlation of galaxy properties with proximity to density ridges, strongly supporting the claim that density ridges are good tracers of filaments.
1509.06384
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Effect of smoothing of density field on reconstruction and anisotropic BAO analysis
Vargas-Magaña, Ho, Fromeneteau, Cuesta
The reconstruction algorithm introduced by Eisenstein+2007, which is widely used in clustering analysis, is based on the inference of the displacement using the Zeldovich approximation from the Gaussian-smooth density field in redshift space. The smoothing-scale applied to the density field affects the inferred displacement field that is used to move the particles, and partially erase their nonlinear evolution. In this article, explore this crucial step on the reconstruction algorithm. Study the performance of the reconstruction technique from two different aspects: the first one, the anisotropic clustering going beyond previous studies, which focus on isotropic clustering, the second is its effect on displacement field. Find that smoothing has a strong effect in the quadrupole of the correlation function and affects the accuracy and precision at which we can measure D_A(z) and H(z). find that the best smoothing scale for BOSS-CMASS galaxies is between 5-10Mpc/h. Varying from the "usual" 15Mpc/h to 5Mpc/h show ~0.5% variations in D_A(z) and H(z) and uncertainties are reduced by 40 and 30%, respectively. Also find that the accuracy of velocity field reconstruction depends strongly on the smoothing scale used for the density field. Measure the bias and uncertainties associated with different choices of smoothing length.
1509.06400
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Mock galaxy catalogues for the final BOSS data release
Kitaura et al
Reproduce the galaxy clustering catalog from BOSS DR12 with high fidelity on all relevant scales in order to allow a robust analysis of BAOs and z-space distortions. Generated 12k MultiDark patchy light-cones corresponding to an effective volume of ~192k [Gpc/h]^3 (the largest ever simulated volume), including cosmic evolution in the range form 0.15 to 0.75. The mocks have been calibrated using a reference galaxy catalogue based on the Halo Abundance Matching modeling of the BOSS DR12 galaxy clustering at a and on the data themselves. The production of the MultiDark PATCHY BOSS DR12 mocks follows 3 steps. (1) apply the PATCHY-code to generate a DM field and an object distribution including nonlinear stochastic galaxy bias. (2) run the halo/stellar distribution reconstruction HADRON-code to assign masses to the various objects. This step uses the mass distribution as a function of local density and nonlocal indicators (i.e., tidal-field tensor eigenvalues and relative halo-exclusion separation for massive objects) from the reference simulation applied to the corresponding PATCHY dark matter and galaxy distribution. (3) in consistency with the observed catalogues, apply the SUGAR-code to build the light-cones. This reproduces the number density, clustering bias, selection function, and survey geometry of the different BOSS galaxy samples. The resulting MultiDark PATCHY mock light-cones reproduce, in general within 1-sigma, the power spectrum and two-point correlation functions up to k=0.3 h/Mpc and down to a few Mpc scales, respectively, and the 3PT statistics of the BOSS DR12 galaxy samples, for arbitrary stellar mass bins.
1509.06404
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: modeling the clustering and halo occupation distribution of BOSS-CMASS galaxies in the Final Data Release
Rodríguez-Torres, et al
Present a study of the clustering and HOD of BOSS CMASS galaxies in 0.43<z<0.7 drawn from the final SDSS-III data release. Compare the BOSS results with the predictions of a halo abundance matching (HAM) clustering model that assigns galaxies to dark matter haloes selected from the large BigMultiDark N-body sims of a flat LCDM Planck cosmology. Compare the observational data with the simulated ones on a light-cone constructed from 20 subsequent outputs of the simulation. Observational effects such as incompleteness, geometry, veto masks and fiber collisions are included in the model, which reproduces within 1-sigma errors the observed monopole of the 2PCF at all relevant scales from the smallest scales 0.5 Mpc/h, up to scale beyond the BAO feature. This model also agrees remarkable well with the BOSS galaxy power spectrum (up to k~1 h/Mpc), and the 3PCF. The quadrupole of the correlation function presents some tensions with observations. Discuss possible causes that can explain this disagreement, including target selection effects. Overall, the standard HAM model describes remarkably well the clustering statistics of the CMASS sample. Compare the stellar to halo mass relation for the CMASS sample measured using weak lensing in the CFHT Stripe 82 survey with the prediction of the clustering model, and find a good agreement within 1-sigma. The BigMD-BOSS light-cone catalogue including properties of BOSS galaxies such as stellar masses, M/L ratios, luminosities, velocity dispersion and halo properties is made publicly available.
1509.06417
The scale-dependence of halo assembly bias
Sunayama, Hearin, Padmanabhan, Leauthaud
The 2PT clustering of MD haloes is influenced by halo properties besides mass, a phenomenon referred to as halo assembly bias. Using the depth of the gravitational potential well, V_max, as the secondary halo property, present the first study of the scale-dependence assembly bias. In the large-scale linear regime, r>10Mpc/h, the findings are in keeping with previous results: at the low-mass end (M_vir<M_coll~1e12.5 Msun), haloes with high-V_max show stronger large-scale clustering relative to halos with low-V_max of the same mass, this trend weakens and reverses for M_vir>M_coll. In the nonlinear regime, assembly bias in low-mass haloes exhibits a pronounced scale-dependent "bump" at 500 kpc/h - 5Mpc/h, a new result. This feature weakens and eventually vanishes for haloes of higher mass. Show that this scale-dependent signature can primarily be attributed to a special subpopulation of ejected halos, defined as present-day host haloes that were previously members of higher-mass halo at some point in their past history. A corollary of the results is that galaxy clustering on scales of r~1-2Mpc/h can be impacted by up to ~15% by the choice of the halo property used in the halo model, even for stellar mass-limited samples.
Tuesday.
1509.05784
A weak gravitational lensing recalibration of the scaling relations linking the gas properties of dark haloes to their mass
Wang, White, Mandelbaum, Henriques, Anderson, Han
Use WL to measure mean mass profiles around Locally Bright Galaxies. These are selected from SDSS DR7 spec and photo catalogs to be brighter than any neighbor projected within 1.0 Mpc and differing in z by <1000 km/s. Most (>83%) are expected to be the central galaxies of their DM haloes. Previous stacking analyses have used this LBG sample to measure mean SZ flux and mean X-ray luminosity as a function of LBG stellar mass. In both cases, a simulation of the formation of the galaxy population was used to estimate effective halo mass for LBGs of given stellar mass, allowing the derivation of scaling relations between the gas properties of haloes and their mass. By comparing results form a variety of sims to the lensing data, show that this procedure has signifiant model dependence reflecting: (i) the failure of any given sim to reproduce observed galaxy abundances exactly; (ii) a dependent on the cosmo underlying the simulations; and (iii) a dependence on the details of how galaxies populate haloes. Use the lensing results to recalibrate the scaling relations, eliminating most of this model dependence and explicitly accounting both for residual modeling uncertainties and for observational uncertainties in the lensing results. The resulting scaling relations link the mean gas properties of dark haloes to their mass over an unprecedentedly wide range, 12.5 < log(M500/Msun) < 14.5, and should fairly and robustly represent the full halo population.
1509.06096
Direct shear mapping: prospects for weak lensing studies of individual galaxy-galaxy lensing systems
de Burge-Day, Taylor, Webster, Hopkins
Investigate (using both theoretical and empirical approach) the frequency of low redshift gg-lensing systems in which the signature of WL might be directly detectable. Find good agreement between these two approaches. In order to make a theoretical estimate of the WL shear, gamma, for each galaxy in a catalogue, made an estimate of the asymptotic circular velocity from the stellar mass using 3 different approaches: from a simulation based relation, from an empirically-derived relation, and using the baryonic Tully-Fisher relation. Using data from the Galaxy and Mass Assembly redshift survey, estimate the frequency of detectable WL at low redshift. Find that to z~0.6, the probability of a galaxy being weakly lensed by at least gamma=0.02 is ~0.01. A scatter in the M*-Mh relation results in a shift towards higher measured shears for a given population of galaxies. Given this, and the good probability of WL at low redshifts, investigate the feasibility of measuring the scatter in the M*-Mh relation using shear statistics. This is a novel measurement, and is made possible because DSM is able to make individual shape direct shape [?] shear measurements, in contrast to traditional WL techniques which can only make statistical measurements. Estimate that for a shear measurement error of Delta gamma =0.02 (consistent with the sensitivity of DSM), a sample of ~50k spatially and spectrally resolved galaxies would allow a measurement of the scatter in the M*-Mh relation to be made. While there are no currently existing IFU surveys of this size, there are upcoming surveys which will provide this data (HETDEX, SKA).
Monday.
1509.05406
The imprint of the cosmic supermassive black hole growth history on the 21 cm background radiation
Tanaka, O'Leary, Perna
The redshifted 21 cm transition line of H tracks the thermal evolution of the neutral IGM at "cosmic dawn," during the emergence of the first luminous astrophysical objects (~100 Myr after the Big Bang) but before these objects ionized the IGM (~400-800Myr after the BB). Because X-rays, in particular, are likely to be the chief energy courier for heating the IGM, measurements of the 21 cm signature can be used to infer knowledge about the first astrophysical X-ray sources. Using analytic arguments and a numerical population synthesis algorithm, argue that the progenitors of SMBHs should be the dominant source of hard astrophysical X-rays --- and thus the primary driver of IGM heating and the 21 cm signature --- at redshifts z<20, if (i) they grow readily from the remnants of Pop III stars and (ii) produce X-rays in quantities comparable to what is observed from AGN and high-mass X-ray binaries. Show that models satisfying these assumptions dominate over contributions to IGM heating from stellar populations, and cause the 21 cm brightness temperature to rise at z>20. An absence of such a signature in the forthcoming observational data would imply that SMBH formation occurred later (e.g. via absence of such a signature in the forthcoming observational data would imply that SMBH formation occurred later (e.g. via so-called direct collapse scenarios), that it was not a common occurrence in early galaxies and protogalaxies, or that it produced far fewer X-rays than empirical trends at lower redshifts, either due to intrinsic dimness (radiative inefficiency) or Compton-think obscuration close to the source.
1509.05420
The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
Majewski, et al
APOGEE, on of the SDSS-III programs, has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the MW. After a 3 year observing campaign on the Sloan 2.5m telescope, APOGEE has collected a half million high res (R~22,500), high S/N (>100), infrared (1.51-1.70 microns) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design --- hardware, field placement, target selection, operations --- and gives an observer of these aspects as well as the data reduction, analysis and products. An index is also given to the complement of technical papers that describe various critical survey opponents in detail. Finally, discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstration, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity and abundance patterns across the Galaxy and as a function of gas, to new views of the ISM, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III DR12, all of the APOGEE data projects are now publicly available.
1509.05504
Detection of signals from a possible extrasolar technological civilization is one of the challenging effort of sciences. Propose using natural telescopes made of single or binary gravitational lensings systems to magnify leakage of EM signs from a remote planet harbors Extra Terrestrial Intelligent (ETI) technology. The gravitational microlensing surveys are monitoring a large area of Galactic bulge for searching microlensing events and each year they find more than 2000 events. These lenses are capable of playing the role of natural telescopes and in some occasions they can magnify signals from planets orbiting around the source stars in the gravitational microlensing systems. Assuming that frequency of EM waves used for telecommunication in ETIs is similar to ours, propose follow-up observation of microlensing events with radio telescopes such as SKA, LFD, and MWA. Amplifying signals from leakage of broadcasting of Earth-like civilizations will allow detection up to the centre of MW galaxy. Analysis show that in binary microlensing systems, the probability of amplification of signals from ETIs is more likely than that n the single microlensing events. Finally, propose a practical observational strategy with the follow-up observation of binary microlensing events with the SKA as a new program for searching ETIs. The probability of detection in the opimisitc values for the factors of Drake equation is around one event per year.
1509.05619
Prediction of galaxy ellipticities and reduction of shape noise in cosmic shear measurements
Croft, Freement, Schuster, Schafer
The intrinsic scatter in the ellipticities of galaxies about the mean shape, known as "shape noise," is the most important source of noise in WL shear measurements. Several approaches to reducing shape noise have recently been put forward. Using information beyond photometry, such as radio polarization and optical spectroscopy. Investigate how well the intrinsic ellipticities of galaxies can be predicted using other, exclusively photometric parameters. These parameters (such as galaxy colors) are already available in the data and do not necessitate additional, often expensive observations, Apply two regression techniques, generalized additive models (GAM) and projection pursuit regression (PPR) to the publicly released data catalog of CHFTLenS. In the simple analysis, find that the individual galaxy ellipticities can indeed be predicted from other photometric parameters to better precision than the scatter about the mean ellipticity. This means that without additional observations beyond photometry the ellipticity contribution to the shear can be measured to higher precision, comparable to using a large sample of galaxies. The best-fit model, achieved using PPR, yields a gain equivalent to having 114.3% more galaxies. Using only parameters unaffected by lensing (e.g.~surface brightness, color) the gain is only ~12%.
Friday.
Icarus, 2015 08 037
Enceladus's measured physical liberation requires a global subsurface ocean
Thomas, et al
Several planetary satellites apparently have subsurface seas that are of great interest for, among other reasons, their possible habitability. The geologically diverse Saturnian satellite Enceladus vigorously vents liquid water and vapor from fractures within a south polar depression and thus must have a liquid reservoir or active melting. However, the extent and location of any subsurface liquid region is not directly observable. Use measurements of control points across the surface of Enceladus accumulated over seven years of spacecraft observations to determine the satellite's precise rotation state, finding a forced physical libration of 0.120±0.014 deg (2sigma). This value is too large to be consistent with Enceladus's core being rigidly connected to its surface, and thus implies the presence of a global ocean rather than a localized polar sea. The maintenance of a global ocean within Enceladus is problematic according to many thermal models and so may constrain satellite properties or require a surprisingly dissipative Saturn.
Nature 525, 351-353
Relativistic boost as the cause of periodicity in a massive black-hole binary candidate
D'Orazio, Haiman, Schiminovich
Because most large galaxies contain a central BH, and galaxies often merge, BH binaries are expected to be common in galactic nuclei. Although they cannot be imaged, periodicities in the light curves of quasars have been interpreted as evidence for binaries, most recently in PG 1302-102, which has a short rest-frame optical period of four years. If the orbital period of the BH binary matches this value, then for the range of estimated BH masses, the components would be separated by 0.007-0.017 parsecs, implying relativistic orbital speeds. There has been much debate over whether BH orbits could be smaller than one parsec. Report that the amplitude and the sinusoid-like shape of the variability of the light curve of PG 1302-102 can be fitted by relativistic Doppler boosting of emission from a compact, steadily accreting, unequal-mass binary. Predict that brightness variations in the UV light curve track those in the optical, but with a two to three times larger amplitude. This prediction is relatively insensitive to the details of the emission process, and is consistent with archival UV data. Follow-up UV and optical observations in the next few years can further test this prediction and confirm the existence of a binary BH in the relativistic regime.
1509.05034
Testing deviations from $/Lambda$CDM with growth rate measurements form 6 Large Scale Surveys at $/mathbf{z=0.06}$ to 1
Alam, Ho, Silvestri
Use measurements from Planck and galaxy redshift surveys over the last decade to test 3 of the basic assumptions of the standard model of cosmology, LCDM: the spatial curvature of the universe, the nature of DE and the laws of gravity on large scales. Obtain improved constraints on several scenarios that violate one or more of these assumptions. Measure w0=-0.94±0.17 (18% measurement) and 1+wa = 1.16±0.36 (31% measurement) for models with a time-dependent EoS, which is an improvement over current best constraints. In the context of modified gravity, consider popular scalar tensor models as well as a parameterization of the growth factor. In the case of one-parameter f(R) gravity models with a LCDM background, constrain B_0<1.36e-5 (1 sigma CL), which is an improvement by a factor of 4 on the current best. Provide the very first constrain on the coupling parameters of general scalar-tensor theory and stringent constraint on the only free coupling parameter of Chameleon models. Also derive constraints on extended Chameleon models, improving the constraint on the coupling by a factor of 6 on the current best. Also measure gamma=0.612±0.072 (11.7% measurement) for growth index parameterization which is an improvement over the current best measurement of gamma=0.699±0.110 (16%). Improve all the current constraints by combining results from various galaxy redshift surveys in a coherent way, which include a careful treatment of scale-dependence introduced by modified gravity.
1509.05058
On weak lensing shape noise
Niemi, Kitching, Cropper
One of the most powerful techniques to study the dark sector of the universe is weak gravitation lensing. In practice, to infer the reduced shear, WL measures galaxy shapes, which are the consequence of both the intrinsic ellipticity of the sources and of the integrated gravitational lensing effect along the LoS. Hence, a very large number of galaxies is required in order to average over their individual properties and to isolate the WL cosmic shear signal. If this 'shape noise' can be reduced, significant advances in the power of a WL surveys can be expected. This paper describes a general method for extracting the probability distributions of parameters from catalogues of data using Voronoi cells, which has several applications, and has synergies with Bayesian hierarchical modeling approaches. This allows us to construct a probability distribution for the variance of the intrinsic ellipticity as a function of galaxy property using only photometric data, allowing a reduction of shape noise. As a proof of concept the method is applied to the CFHTLenS survey data. Use this approach to investigate trends of galaxy properties in the data and apply this to the case of WL power spectra.
Thursday.
1509.04822
Serendipitous discovery of an extended X-ray jet without a radio counterpart i a high-redshift quasar
Simionescu, et al
A recent Chandra observation of the nearby galaxy cluster Abell 585 has led to the discovery of an extended X-ray jet associated with the high-z background quasar B3 0727+409, a luminous radio source at z=2.5. This is one of only few examples of high-z X-ray jets known to date. It has a clear extension of about 10-12", corresponding to a projected length of 80-100 kpc, which a possible hot spot as far as 35" from the quasar. The archival high resolution VLA maps surprisingly reveal no extended jet emission, except for one knot about 1.4" away from the quasar. The high X-ray to radio luminosity ratio for this source appears consistent with the ~(1+z)^4 amplification expected from the inverse Compton radiative model. This serendipitous discovery may signal the existence of an entire population of similar systems with bright X-ray and faint radio jets at high z, a selection bias which must be accounted for when drawing any conclusions about the z evolution of jet properties and indeed a out the cosmo evolution of SMBHs and AGN in general.
1509.02938
Probing dark matter substructure with pulsar timing: I. constraints on ultracompact minihalos
Clark, Lewis, Scott
Small-scale DM structure within the MW is expected to affect pulsar timing. The change in gravitational potential induced by a DM halo passing near the LoS to a pulsar would produce a varying delay in the light travel time of photons for the pulsar. Individual transits produce an effect that would either be too rare or too weak to be detected in 30-year pulsar observations. However, a population of DM sub haloes would be expected to produce a detectable effect on the measured properties of pulsars if the subclass constitute a significant fraction of the total halo mass. The effect is to increase the dispersion of measured period derivatives across the pulsar population. By statistical analysis of the ATNF pulsar catalogue, place an upper limit on this dispersion of log sigma_P<=17.05. Use this to place strong upper limits on the number density of ultracompact mini halos within the MW. These limits are completely independent of the particle nature of DM.
Wednesday.
1509.04275
Investigating the cores of fossil systems with Chandra
Bharadwaj, Reiprich, Sanders, Schellenberger
Investigate the cores of fossil galaxy groups and clusters ('fossil systems') using archival Chandra data for a sample of 17 fossil systems. Determined the cool-core fraction for fossils via three observable diagnostics, the central cooling time, cuspiness and concentration parameter. Quantified the dynamical state of the fossils by the X-ray peak/BCG, and the X-ray peak/emission weighted centre separations. Studied the X-ray emission coincident with the BCG to detect the presence of potential thermal coronae. A deprojection analysis was performed for z<0.05 fossils to obtain cooling time and entropy profiles, and to resolve subtle temperature structures. Investigated the Lx-T relation for fossils from the 400d catalogue to see if the scaling relation deviates form that of other groups. Most fossils are identified as cool-core objects via at least two cool-core diagnostics. All fossils have their dominant elliptical galaxy within 50 kpc of the X-ray peak, and most also have the emission weighted center within that distance. Do not see clear indications of a X-ray corona associated with the BCG unlike that has been observed for some other objects. Fossils do not have universal temperature profiles, with some low-temperature objects lacking features that are expected for ostensibly relaxed objects with a cool-core. The entropy profiles of the z<0.05 fossil systems can be well-described by a power law model, albeit with indices smaller than 1. The 400d fossils Lx-T relation shows indications of an elevated normalization with respect to other groups, which seems to persist even after factoring in selection effects.
1509.04290
Mitigating systematic errors in angular correlation function measurements from wide field surveys
Morrison, Hildebrandt
Present an investigation into the effects of survey systematics such as varying depth, PSF size, and extinction on the galaxy selection and correlation in photometric, multi-epoch, wide area surveys. Take the CFHTLenS as an example. Variations in galaxy selection due to systematics are found to cause density fluctuations of up to 10% for some small fraction of the area for most galaxy redshift slices and as much as 50% for some extreme cases of faint high-redshift samples. This results in correlations of galaxies against survey systematics of order ~1% when averaged over the survey area. Present an empirical method for mitigating these systematics correlations from measurements of angular correlation functions using weighted random points. These weighted random catalogs are estimated from the observed galaxy over-densities by mapping these to survey parameters. Able to model and mitigate the effect of systematic correlations allowing for non-linear dependences of density on systematics. Applied to CFHTLenS, find that the method reduces spurious correlations in the data by a factor of two for most galaxy samples and as much as an order of magnitude in others. Such a treatment is particularly important for an unbiased estimation of very small correlation signals, as e.g. from weak gravitational lensing magnification bias. Impose a criterion for using a galaxy sample in a magnification measurement of the majority of the systematic correlations show improvement and are less than 10% of the expected magnification signal when combined in the galaxy cross correlation. After correction the galaxy samples in CFHTLenS satisfy this criterion for z_phot<0.9 and will be used in a future analysis of magnification.
1509.04293
Gaussian covariance matrices for anisotropic galaxy clustering meausrements
Grieb, Sánchez, Salazar-Albornoz, dalla Veccia
Measurement of the redshift-space galaxy clustering have bee na prolific source of cosmological information in recent years. In the era of precision cosmology, accurate covariance estimates are an essential step for the validation of galaxy clustering models of the redshift-space two-point statistics. For cases where only a limited set of simulations is available, assessing the data covariance is not possible or only leads to a noisy estimate. Relying on simulated realizations of the survey data means that tests of the cosmo dependence of the covariance are expensive. With these two points in mind, this work aims at presenting a simple theoretical model for the linear covariance of anisotropic galaxy clustering observations with synthetic catalogues. Considering the Legendre moments ('multipoles') of the 2PT statistics and projections into wide bins of the line-of-sight parameter ('clustering wedges'), describe the modeling of the covariance for these anisotropic clustering measurements for galaxy samples with a trivial geometry in the case of a Gaussian approximation of the clustering likelihood. The explicit formulas are presented for Fourier space and for configuration space covariance matrices. To validate the model, create synthetic HOD galaxy catalogues by populating the haloes of an ensemble of large-volume N-body simulations. Using linear and non-linear input power spectra, find excellent agreement between the model predictions and the measurements on the synthetic catalogues.
1509.04345
Discovery of a strongly-lensed massive quiescent galaxy a z=2.636: spatially-resolved spectroscopy and indications of rotation
Newman, Belli, Ellis
As the title says. Velocity dispersion with the effective radius is sigma_e=271±41 km/s.
1509.04430
Spectral properties of galaxies in void regions
Liu, Pan, Hao, Hoyle, Constantin, Vogeley
Present a study of spectral properties of galaxies in underdense large-scale structures, voids. The void galaxy sample (75939 galaxies) is selected from SDSS DR7 with z<0.107. Find that there are no significant differences in the luminosities, stellar masses, stellar populations, and sSFRs between void galaxies of specific spectral types and their wall counterparts. However, the fraction of SF galaxies in voids is significantly higher (>9%) than that in walls. Void galaxies, when considering all spectral types, are slightly fainter, less massive, have younger stellar populations and of higher sSFRs than wall galaxies. These minor differences are totally caused by the higher fraction of SF galaxies in voids. Confirm that AGNs exist in voids, already found by CO08, with similar abundance as in walls. Type I AGNs contribute ~1-2% of void galaxies, similar to their fraction in walls. The intrinsic [OIII] luminosities, spanning over 1e6 Lsun~ 1e9 Lsun, and Eddington ratios are similar comparing the void AGNs versus wall AGNs. Small scale statistics show that all spectral types of void galaxies are less clustered than their counterparts in walls. major merger may not be the dominant trigger of BH accretion in the luminosity range probed. Study implies that the growth of BHs relies weakly on LSS.
Tuesday.
1509.03632
Quenching star formation: insights from the local main sequence
Leslie, Kewley, Sanders, Lee
The so called "star forming main sequence" of galaxies is the apparent tight relationship between the star formation rate and stellar mass of a galaxy. Previous studies exclude galaxies which are not strictly "star forming" from the main sequence, because they do not lie on the same tight relation. Using local galaxies in SDS, classify galaxies according to their emission in ratios, and study their location on the SFR - stellar mass plane. Find that galaxies form a sequence from the "blue cloud" galaxies which are actively forming stars, through a combination of composite, Seifert, and LINER (Low-ionization nuclear emission-line region) galaxies, ending as "read-and-dead" galaxies. The sequence supports an evolutionary pathway for galaxies in which SF quenching by AGN plays a key role.
1509.03947
Formation of emission line dots and extremely metal-deficient dwarfs from almost dark galaxies
Bekki
Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-res DM haloes. Investigate SFHs of these gas-rich dwarf ("almost dark") galaxies both for isolated and interacting/merging cases. Find that although SFRs are very low (1e-5 Msun/yr) in the simulated dwarfs in isolation for the total halo masses (M_h) of 1e8-9 Msun, they can be dramatically increased to be ~1e-4 Msun/yr when they interact omega with other dwarfs. These interacting faint dwarfs with central compact HII regions can be identified as isolated emission dots ("ELdots") owing to their very low surface brightness envelopes of old stars. The remnant of these interacting and merging dwarf can finally develop central compact stellar systems with very low metallicities (Z/Zsun<0.1), which can be identified as extremely metal-deficient ("XMD") dwarfs. These results imply that although there would exist many faint dwarfs that can be hardly detected n the current optical observations, they can be detected as isolated ELdots or XMD dwarfs, when they interact with other galaxies and their host environments. Predict that owing to the very low surface brightness stellar envelopes, if they are distant objects.
1509.04071
A direct measurement of tomographic lensing power spectra from CFHTLenS
Köhlinger, Viola, Valkenburg, Joachimi, Hoekstra, Kuijken
Measure the WL shear power spectra and their cross-power in 2 photo-z bins from the CFHTLenS. The measurements are performed directly in multipole space in terms of adjustable band powers. For the extraction of the band powers from the data, implemented and extended a quadratic estimator, a maximum likelihood method that allows to readily take into account irregular survey geometries, masks, and varying sampling densities. Find the 68% credible intervals in the sigma8-Omega_m-plane to be marginally consistent with results from Planck for a single five parameter LCDM model. For the projected parameter S8==sigma8(Omega_m/0.3)^0.5, obtain a best-fitting value of S8=0.768+0.045=0.039. This constraint is consistent with results from other CFHTLenS studies as well as the DES. The most conservative model, including modifications to the power spectrum due to baryon feedback and marginalization over photo-z errors, yields an upper limit on the total mass of 3 degenerate massive neutrinos of Sigma m_nu<4.53 eV at 95 % credibility, while a Bayesian model comparison does not favor any model extension beyond a simple 5 parameter LCDM model. Combining the shear likelihood with Planck breaks the sigma8-Omega_m degeneracy and yields sigma8=0.817+0.013-0.014 and Omega_m=0.298±0.011 which is fully consistent with results from Planck alone.
