Tuesday.
1304.7273
The M87 Black hole mass from gas-dynamical models of space telescope imaging spectrograph observations
Walsh et al
As the title says. Map out the complete kinematic structure of the emission-line disk within about 40 pc from the nucleus. The gas-dynmical BH mass continues to differ from the most recent stellar-dynamical mass by a factor of two.
1304.7276
High velocity outflows from young star-formin galaxies in the UKIDSS ultra-deep survey
Bradshaw et al
Galactic scale outflows for 0.71<z<1.63 using 413 K-band selected galaxies observed in spectro follow-up. Average M* of 1e9.5 Msun and span a wide range in rest-frame colors, representing typical SF galaxies at this epoch. Stack the spectra by various galaxy properties, including stellar mass, [OII] EW, SFR, sSFR and rest-frame spectral indicies. Find that out flows are present in virtually all spectral stacks, with velocities ranging from 100-1000 km/s, indicating that large-scale outflowing winds are a common property at these redshifts. [are there any red galaxies or non-SF galaxies in the sample?] The highest outflows (>500 km/s) are found in galaxies with the highest stellar masses and the youngest stellar populations. Findings suggest that high velocity galactic outflows are mostly driven by SF processes rather than AGN, with implied mass outflow rates comparable to the rates of SF. Such behaviour is consistent with models required to reproduce the high-z mass-metallicity relation.
1304.7317
Cosmic opacity: cosmological-model-independent tests and their impacts on cosmic acceleration
Li, et al
Assume distance-duality relation entirely arises from non-conservation of the photon number, and absorption is frequency independent in the observed frequency range; perform cosmological-model-independent tests for the cosmic opacity. ... analysis suggests that an accelerated cosmic expansion is still needed to account for the dimming of SNe.
1304.7681
Reconstructing the projected gravitational potential of galaxy clusters from galaxy kinematics
Sarli, ... Meneghetti, ... Bartelmann
Develop a method for reconstructing the 2d, projected gravitational potential of galaxy clusters from observed line-of-sight velocity dispersions of cluster galaxies. It is the third of an intended series of papers aiming at a unique reconstruction method for cluster potentials combining lensing, X-ray, SZ and kinematic data. The observed galaxy velocity dispersions are deprojected. The obtained radial velocity dispersions are then related to the gravitational potential by using the tested assumption of a polytropic relation between the effective galaxy pressure [?] and the density. Once the gravitational potential is obtained in 3d, projection along the LoS yields the 2d potential. For simplicity, adopt spherical symmetry and a known profile for the anisotropy parameter of the galaxy velocity dispersions. Test the method with a numerically simulated galaxy cluster and galaxies identified therein. Extract a projected velocity-dispersion profile from the simulated cluster and pass it through the algorithm, showing that the deviation between the true and the reconstructed potential is <10% within approximately 1.2 Mpc/h from the cluster center.
1304.7689
Accurate weak lensing of standard candles, Part 1: flexible cosmological fits
Amendola, Marra, Quartin
Magnitude scatter of SNIa will become a major issue, affecting parameter estimation. Current N-body simulations are too time consuming to be integrated in the likelihood analysis used for estimating the cosmo parameters. In this paper, show that in the WL regime a statistical numerical approximation produces accurate results orders of magnitude faster. Fits to lensing magnification probability distribution as a function of redshift, of the PS normalization and of the present-day matter density. Also improve upon existing models of lensing variance and show that a shifted lognormal distribution fits well the numerical one. These fits can be easily employed in cosmo likelihood analysis. Theoretical predictions make it possible to invert the problem and begin using SNe lensing to constrain the cosmo parameters.
Tuesday, April 30, 2013
Monday, April 29, 2013
Day 422
Sunday and Monday.
1306.0818
A new method for gravitational wave detection with atomic sensors
Graham, Hogan, Kasevich, Rajendran
Dominant noise background for detection of gravitational waves using long-baseline optical interferometry is "laser frequency noise"; amelioration of this noise requires near simultaneous strain measurements on more than one interferometer baseline, necessitating more than two satellites for a space-based detector, or two interferometer arms for a ground-based detector. Describe a new detection strategy based on recent advances in optical atomic clocks and atom interferometry which can operate at long-baselines and which is immune to laser frequency noise; suppressed because the signal arises strictly from the light propagation time between two ensembles of atoms. This new class of sensor allows sensitive gravitational wave detection with only a single baseline. This approach also has practical applications in the development of ultra-sensitive gravimeters and gravity gradiometers.
1304.7003
Molecular hydrogen in the damped Lyman-alpha system towards GRB 120815A at z=2.36
Krühler et al
As the title says. Molecular H2 hard to detect beyond z~0, but found one in the GRB host DLA system at z=2.36.
1304.7005
Ultraviolet extinction at high galactic latitudes
Peek, Schiminovich
Study GALEX WISE all-sky data of 373k galaxies; examine the variation in aggregate UV colors and number density of these galaxies, and measure the extinction curve at high latitude. Additionally consider SDSS spectra in optical. Find: dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is ~10% and 35% higher than expected, with significant variation across the sky. Find that no single R_V parameter fits both the optical and UV extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. Propose that the overall trends detected likely stem from an increase in very small silicate grains in the ISM.
1304.7015
Keck spectroscopy of gravitationally lensed z=4 galaxies: improved constraints on the escape fraction of ionizing photons
Jones, Ellis, Schenker, Stark
The fraction of photons that escape from young SF galaxies is one of the largest uncertainties in determining the role of galaxies in cosmic reionization. Yet traditional techniques for measuring this fraction are inapplicable at the redshifts of interest due to FG screening by Lya forest. Earlier, demonstrated a reduction in the EW of low-ioinization absorption lines in composite spectra of LBG at z=4 compared to similar measures at z=3. This might imply a lower covering fraction of neutral gas and hence an increase with redshift in the escape fraction of ionizing photons. However, spectral resolution was inadequate to differentiate between several alternative explanations, including changes with redshift int the outflow kinematics. Present higher quality spectra of 3 gravitationally lensed LBGs at z=4 with a spectral resolution sufficient to break this degeneracy of interpretation. Present a method for deriving the covering fraction lf low-ioinization gas as a function of outflow velocity and compare the results with similar quality data taken for galaxies at lower redshift. Find a significant trend of lower covering fractions of low-ioinization gas for galaxies with strong Lya emission. Present a method for deriving the covering fraction of low-ionization gas as a function of outflow velocity and compare the results with similar quality data taken for galaxies at lower redshift. Find a significant trend of lower covering fractions of low-ioinization gas for galaxies with strong Lya emission. In combination with the demographic trends of Lya emission with redshift from earlier work, results provide new evidence for a reduction in the average HI covering fraction, and hence an increase in the escape fraction of ionizing radiation from LBG, with redshift.
1304.7156
The M_BH - sigma relation for intermediate-mass black holes in globular clusters
Lützgendorf, et al
The total mass of the globular cluster correlates with the mass of the IMBH. While the slope of the M_BH - sigma correlation differs strongly from the one observed for SMBHs, the other scaling relations M_BH - M_TOT, and M_BH - L are similar to the correlations in galaxies. Significant correlations of BH mass with other cluster properties were not found in the present sample of 14.
1304.7175
The nature of obscuration in AGN: I. Insights from host galaxies
Shao, Kauffmann, et al
30k nearby obscured AGNs with SDSS spectra and MIR photometry from WISE. Investigate the host galaxy properties in AGNs where the nuclear activity level is indicated by L_MIR, and to compare the results to previous studies, which have used the [OIII] emission line as the main BH activity indicator. First carry out a systematic study of how the MIR colors of AGN hosts vary as a function of age-sensitive 4000A break strength and optical "Eddington parameter" (L[OIII]/M_BH). The MIR color has weak dependence on break strength, but strong dependence on L[OIII]/M_BH. Then use a "pari-matching" technique to subtract the 4.6 um stellar emission contributed by the host galaxy. Intrinsic 4.6 um AGN luminosities can be recovered for most Seyferts, but only statistically for LINERs. Combine sample of Seyferts with type 1 AGN and quasars at z<0.7 from SDSS; show that the [OIII] and 4.6 um luminosities correlate roughly linearly over 4 orders of magnitude, but with substantial scatter. ... supports the hypothesis that an abundant supply of gas is a prerequisite for the formation of an obscuring "torus".
1306.0818
A new method for gravitational wave detection with atomic sensors
Graham, Hogan, Kasevich, Rajendran
Dominant noise background for detection of gravitational waves using long-baseline optical interferometry is "laser frequency noise"; amelioration of this noise requires near simultaneous strain measurements on more than one interferometer baseline, necessitating more than two satellites for a space-based detector, or two interferometer arms for a ground-based detector. Describe a new detection strategy based on recent advances in optical atomic clocks and atom interferometry which can operate at long-baselines and which is immune to laser frequency noise; suppressed because the signal arises strictly from the light propagation time between two ensembles of atoms. This new class of sensor allows sensitive gravitational wave detection with only a single baseline. This approach also has practical applications in the development of ultra-sensitive gravimeters and gravity gradiometers.
1304.7003
Molecular hydrogen in the damped Lyman-alpha system towards GRB 120815A at z=2.36
Krühler et al
As the title says. Molecular H2 hard to detect beyond z~0, but found one in the GRB host DLA system at z=2.36.
1304.7005
Ultraviolet extinction at high galactic latitudes
Peek, Schiminovich
Study GALEX WISE all-sky data of 373k galaxies; examine the variation in aggregate UV colors and number density of these galaxies, and measure the extinction curve at high latitude. Additionally consider SDSS spectra in optical. Find: dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is ~10% and 35% higher than expected, with significant variation across the sky. Find that no single R_V parameter fits both the optical and UV extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. Propose that the overall trends detected likely stem from an increase in very small silicate grains in the ISM.
1304.7015
Keck spectroscopy of gravitationally lensed z=4 galaxies: improved constraints on the escape fraction of ionizing photons
Jones, Ellis, Schenker, Stark
The fraction of photons that escape from young SF galaxies is one of the largest uncertainties in determining the role of galaxies in cosmic reionization. Yet traditional techniques for measuring this fraction are inapplicable at the redshifts of interest due to FG screening by Lya forest. Earlier, demonstrated a reduction in the EW of low-ioinization absorption lines in composite spectra of LBG at z=4 compared to similar measures at z=3. This might imply a lower covering fraction of neutral gas and hence an increase with redshift in the escape fraction of ionizing photons. However, spectral resolution was inadequate to differentiate between several alternative explanations, including changes with redshift int the outflow kinematics. Present higher quality spectra of 3 gravitationally lensed LBGs at z=4 with a spectral resolution sufficient to break this degeneracy of interpretation. Present a method for deriving the covering fraction lf low-ioinization gas as a function of outflow velocity and compare the results with similar quality data taken for galaxies at lower redshift. Find a significant trend of lower covering fractions of low-ioinization gas for galaxies with strong Lya emission. Present a method for deriving the covering fraction of low-ionization gas as a function of outflow velocity and compare the results with similar quality data taken for galaxies at lower redshift. Find a significant trend of lower covering fractions of low-ioinization gas for galaxies with strong Lya emission. In combination with the demographic trends of Lya emission with redshift from earlier work, results provide new evidence for a reduction in the average HI covering fraction, and hence an increase in the escape fraction of ionizing radiation from LBG, with redshift.
1304.7156
The M_BH - sigma relation for intermediate-mass black holes in globular clusters
Lützgendorf, et al
The total mass of the globular cluster correlates with the mass of the IMBH. While the slope of the M_BH - sigma correlation differs strongly from the one observed for SMBHs, the other scaling relations M_BH - M_TOT, and M_BH - L are similar to the correlations in galaxies. Significant correlations of BH mass with other cluster properties were not found in the present sample of 14.
1304.7175
The nature of obscuration in AGN: I. Insights from host galaxies
Shao, Kauffmann, et al
30k nearby obscured AGNs with SDSS spectra and MIR photometry from WISE. Investigate the host galaxy properties in AGNs where the nuclear activity level is indicated by L_MIR, and to compare the results to previous studies, which have used the [OIII] emission line as the main BH activity indicator. First carry out a systematic study of how the MIR colors of AGN hosts vary as a function of age-sensitive 4000A break strength and optical "Eddington parameter" (L[OIII]/M_BH). The MIR color has weak dependence on break strength, but strong dependence on L[OIII]/M_BH. Then use a "pari-matching" technique to subtract the 4.6 um stellar emission contributed by the host galaxy. Intrinsic 4.6 um AGN luminosities can be recovered for most Seyferts, but only statistically for LINERs. Combine sample of Seyferts with type 1 AGN and quasars at z<0.7 from SDSS; show that the [OIII] and 4.6 um luminosities correlate roughly linearly over 4 orders of magnitude, but with substantial scatter. ... supports the hypothesis that an abundant supply of gas is a prerequisite for the formation of an obscuring "torus".
Thursday, April 25, 2013
Day 421
Friday.
1304.6719
The column density distribution and continuum opacity of the intergalactic and circumgalactic medium at redshift <z>=2.4
Rudie, Steidel, Shapley, Pettini
As the title says. Use hyperluminous QSO, fit Voigt profile to full Lyman alpha and beta forests in 15 high-res high-S/N spectra; measure IGM, CGM. Find that the incidence of absorbers in the CGM is much higher than in the IGM. In agreement with Rudie+, find that there are fractionally more high-NHI absorbers than low-NHI absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution. Reproducing the opacity measured as well as the incidence of absorbers with log(NHI)>17.2 requires a broken power law parameterization of the frequency distribution with a break near log(NHI)~15. Compute new estimates of the MFP (mean free path) to H-ionizing photos at z=2.4; find MFP=147 pm 15 Mpc when considering only IGM opacity. If considering photos emanating from a high-z SF galaxies and account for the local excess opacity due to the surrounding CGM of the galaxy itself, the MFP is reduced to 121 pm 15 Mpc. These MPF measurements are smaller than recent estimates and should inform future studies of the metagalactic UV background and of ionizing sources at z~2-3.
1304.6780
Practices in source code sharing in astrophysics
Shamir et al
Suggest that a paper that involves a computer program not be accepted for publication unless the source code becomes publicly available.
1304.6719
The column density distribution and continuum opacity of the intergalactic and circumgalactic medium at redshift <z>=2.4
Rudie, Steidel, Shapley, Pettini
As the title says. Use hyperluminous QSO, fit Voigt profile to full Lyman alpha and beta forests in 15 high-res high-S/N spectra; measure IGM, CGM. Find that the incidence of absorbers in the CGM is much higher than in the IGM. In agreement with Rudie+, find that there are fractionally more high-NHI absorbers than low-NHI absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution. Reproducing the opacity measured as well as the incidence of absorbers with log(NHI)>17.2 requires a broken power law parameterization of the frequency distribution with a break near log(NHI)~15. Compute new estimates of the MFP (mean free path) to H-ionizing photos at z=2.4; find MFP=147 pm 15 Mpc when considering only IGM opacity. If considering photos emanating from a high-z SF galaxies and account for the local excess opacity due to the surrounding CGM of the galaxy itself, the MFP is reduced to 121 pm 15 Mpc. These MPF measurements are smaller than recent estimates and should inform future studies of the metagalactic UV background and of ionizing sources at z~2-3.
1304.6780
Practices in source code sharing in astrophysics
Shamir et al
Suggest that a paper that involves a computer program not be accepted for publication unless the source code becomes publicly available.
Day 420
Thursday.
1304.6087
The abundance of voids and the excursion set formalism
Jennings, Li, Hu
Measure number density of voids in N-body sims of LCDM. Define voids as spherical regions of rho_v=0.2 rho_m around density minima in order to relate results to the predicted abundances using the excursion set formalism. Using a linear under-density of delta_v = -2.7, from a spherical evolution model, find that a volume conserving model (which does not conserve number density in the mapping from the linear to the NL regime) matches the measured abundance to within 16% for a range of void radii 1<r<15. This model fixes the volume fraction of the universe which is in voids and assumes that voids of a similar size merge as they expand by a factor of 1.7 to achieve a NL density of rho_v = 0.2 rho_m today. Find that the model of Sheth & van de Weygaert for the number density of voids greatly over-predicts the abundances over the same range of scales. Find that the volume conserving model works well at matching the number density of voids measured from the simulations at higher redshifts, z=0.5 and 1, as well as correctly predicting the abundances to within 25% in a simulation of a matter dominated Omega_m = 1 universe. Examine the abundance of voids in the halo distribution and find fewer small, r<10 Mpc/h, voids and many more large, r>10 Mpc/h, voids compared to the DM. These results indicate that voids identified in the halo or galaxy distribution are related to the underlying void distribution in the DM in a complicated way which merits further study if voids are to be used as a precision probe of cosmology.
1304.6696
Studying Inter-cluster galaxy filaments through stacking GMBCG galaxy cluster pairs
Zhang, Dietrich, McKay, Sheldon, Nguyen
Present method to study the photometric properties of galaxies in filaments by stacking the galaxy populations between pairs of galaxy clusters. This method can detect the inter-cluster filament galaxy overdensity with a significance of ~5 sigma out to z=0.40. Using this approach, study the g-r color and luminosity distribution of filament galaxies as a function of redshift. Consistent with expectation, filament galaxies are bimodal in their color distribution and contain a larger blue galaxy population than cluster galaxies. More interestingly, the observed filament population shows redshift evolution at 0.12<z<0.40: the blue galaxy fraction increases at higher redshift: a filament "Butcher Oemler Effect". Test the dependence of the observed filament density on the richness of the cluster pair: richer clusters are connected by higher density filaments. Also test the spatial dependence of filament galaxy overdensity: This quantity decreases when moving away from the inter-cluster axis between a cluster pair. This method provides an economical way to probe the photometric properties of filament galaxies and should prove useful for upcoming projects like DES.
Day 419
Wednesday.
1304.6080
Segue 2: the least massive galaxy
Kirby, Boylan-Kolchin, Gohen, Geha, Bullock, Kaplinghat
A galaxy with only 900 Msun. Spectroscopy of 25 members. Velocity dispersion too small to be measured; upper limit is 2.2 km/s (90% CL). Mass within 3d HLR (46 pc) is m_1/2 < 1.5e5 Msun [I assume this includes DM, since it's based on velocity dispersion]. Identify Segue 2 as a galaxy rather than a star cluster, based on the wide dispersion in [Fe/H] (-2.8 to -1.4) among the member stars. The stars' [alpha/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained SNIa ejecta despite its presently small mass and that SF lasted for at least 100 Myr. The mean metallicity <[Fe/H]>=-2.26pm0.13 (about the same as Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the MW. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternative.y, Segue 2 could have been born in a very low-mass DM subhalo (v_max < 10km/s), below the atomic hydrogen cooling limit.
1304.6083
The impact of bars on disk breaks as probed by S4G imaging
Munoz-Mateos, et al
Spitzer Survey of Stellar Structure in Galaxies (S4G). Analyze radial distribution of old stars in a sample of 218 nearby face-on disks, in 3.6 um. Disks with a broken or down-bending profile; find that, on average, disks with a genuine single exponential profile have a scale-length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the case of barred galaxies, the ratio between the break and the bar radii (Rbr/Rbar) depends strongly on the total stellar mass of the galaxy. For galaxies more massive than 1e10 Msun, the distribution is bimodal, peakng at Rbr/Rbar~2 and ~3.5. THe first peak, which is the most populated one, is linked to the Outer LIndblad Resonance of the bar, whereas the second one is consistent with a dynamical coupling between the bar and the spiral pattern. For galaxies below 1e10 Msun, breaks are found up to ~10 Rbar, but we show that they could still be caused by resonatnces given the rising nature of rotation curves in these low-mass disks. While not ruling out star formation thresholds, results imply that radial stellar migration induced by non-axysummetric features can be responsible not only for those breaks at 2 Rbar, but also for many of those found at larger radii. [I didn't get it]
1304.6084
Asymmetric streaming motion in the galactic bulge X-shaped structure revealed by the OGLE-III proper motions
Poleski, .. Gould
As the title says.
1304.6080
Segue 2: the least massive galaxy
Kirby, Boylan-Kolchin, Gohen, Geha, Bullock, Kaplinghat
A galaxy with only 900 Msun. Spectroscopy of 25 members. Velocity dispersion too small to be measured; upper limit is 2.2 km/s (90% CL). Mass within 3d HLR (46 pc) is m_1/2 < 1.5e5 Msun [I assume this includes DM, since it's based on velocity dispersion]. Identify Segue 2 as a galaxy rather than a star cluster, based on the wide dispersion in [Fe/H] (-2.8 to -1.4) among the member stars. The stars' [alpha/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained SNIa ejecta despite its presently small mass and that SF lasted for at least 100 Myr. The mean metallicity <[Fe/H]>=-2.26pm0.13 (about the same as Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the MW. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternative.y, Segue 2 could have been born in a very low-mass DM subhalo (v_max < 10km/s), below the atomic hydrogen cooling limit.
1304.6083
The impact of bars on disk breaks as probed by S4G imaging
Munoz-Mateos, et al
Spitzer Survey of Stellar Structure in Galaxies (S4G). Analyze radial distribution of old stars in a sample of 218 nearby face-on disks, in 3.6 um. Disks with a broken or down-bending profile; find that, on average, disks with a genuine single exponential profile have a scale-length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the case of barred galaxies, the ratio between the break and the bar radii (Rbr/Rbar) depends strongly on the total stellar mass of the galaxy. For galaxies more massive than 1e10 Msun, the distribution is bimodal, peakng at Rbr/Rbar~2 and ~3.5. THe first peak, which is the most populated one, is linked to the Outer LIndblad Resonance of the bar, whereas the second one is consistent with a dynamical coupling between the bar and the spiral pattern. For galaxies below 1e10 Msun, breaks are found up to ~10 Rbar, but we show that they could still be caused by resonatnces given the rising nature of rotation curves in these low-mass disks. While not ruling out star formation thresholds, results imply that radial stellar migration induced by non-axysummetric features can be responsible not only for those breaks at 2 Rbar, but also for many of those found at larger radii. [I didn't get it]
1304.6084
Asymmetric streaming motion in the galactic bulge X-shaped structure revealed by the OGLE-III proper motions
Poleski, .. Gould
As the title says.
Monday, April 22, 2013
Day 418
Tuesday.
1304.5537
The HETDEX pilot survey. IV. The evolution of [O II] emitting galaxies frorm z~0.5 to z~0
Ciardullo et al
Emission-line flux, and de-reddened [O II] 3727 luminosity; calculate total SFR. Show that over the last ~5 Gyr of cosmic time there has been substantial evolution in the [OII] emission line luminosity function, with L* decreasing by ~0.6pm0.2 dex in the observed function, and by ~0.9pm0.2 dex in the de-reddened relation. Accompanying this decline is a significant shift in the distribution of [OII] equivalent widths, with the fraction of high equivalent-width emitters declining dramatically with time. Overall, the data imply that athe relative intensity of SF within galaxies has decreased over the past ~5 Gyr, and that the SFR density of the universe has declined by a factor of ~2.5 between z~0.5 and 0.
1304.5557
The dark side of galaxy color
Hearin, Watson
"Age distribution matching": a new theoretical formalism for predicting how galaxies of luminosity L and color C occupy dark matter haloes. Model supposes that there are just two fundamental properties of a halo that determine the color and brightness of the galaxy it hosts: the maximum circular velocity Vmax, and the redshift at which the galaxy will be starved of cold gas z_starve. The halo property z_starve is intended to encompass physical characteristics of a halo's mass assembly history (MAH) that may deprive the galaxy of its cold gas supply and, ultimately, quench its star formation. These include the epochs when: (a) a halo accretes onto a large halo, z_acc, (b) a halo reaches a characteristic mass (~1e12 Msun/h), z_char, and (c) a halo transitioned from the fast- to slow-accretion regime, z_form. A halo's z_starve value is determined by whichever of these events happens first in its MAH. The new, defining feature of the model is that, at fixed L, galaxy color is in monotonic correspondence with z_starve with the larger values of z_starve being assigned redder colors. Populate the Bolshoi N-body simulation with a mock galaxy catalog based on age distribution matching, and show that the resulting mock galaxy distribution accurately describes the luminosity- and color-binned two-point correlation function of galaxies in SDSS, as well as a variety of low-redshift galaxy group statistics. Study of the property z_starve has important implications for how halo MAH influences stellar mass assembly. For example, the significance of the epoch z_form suggests a new, independent channel for so-called "mass quenching" based on the rate of halo mass accretion. Make publicly available the low-z, SDSS Mr<-19 mock galaxy catalog, and main progenitor histories of all z=0 Bolshoi halos.
1304.5573
Mean spectral energy distributions and bolometric corrections for luminous quasars
Krawczyk, Richards, Mehta, Vogeley, ... Ross, Schneider
UV to MIR SEDs of 119k luminous broad-lined quasars with 0.064<z<5.46 from Spitzer and WISE (MIR), 2MASS and UKIDSS (NIR), SDSS (optical), and GalEx (UV). The mean SED requires a bolometric correction (relative to 2500A) of BC=2.75pm0.40 using the integrated light from 1um-2keV, and further explore the range of bolometric corrections for each object. Investigate the dependence of the mean SED on various parameters, particularly the UV luminosity for quasars with 0.5<z<3 and the properties of the UV emission lines for quasars with z>1.6; the latter is a possible indicator of the strength of the accretion disk wind, which is expected to be SED dependent. L-dependent mean SEDs show that, relative to the high-L SED, low-L SEDs exhibit a harder FUV spectral slope, a redder optical continuum, and less host dust. Mean SEDs constructed instead as a function of UV emission line properties reveal changes that are consistent with known PCA trends. A potentially important contribution to the bolometric correction is the unseen E-UV continuum. Lower-L quasars and/or quasars with disk-dominated broad emission lines may require an extra continuum component in the EUV that is not present in high-L quasars with strong accretion disk winds. Consider 4 possible models and explore the resulting bolometric corrections. Important to accurate determination of quasar accretion rates.
1304.5738
Microlensing in globular clusters: the first confirmed lens
Jetzer
As the title says.
1304.5537
The HETDEX pilot survey. IV. The evolution of [O II] emitting galaxies frorm z~0.5 to z~0
Ciardullo et al
Emission-line flux, and de-reddened [O II] 3727 luminosity; calculate total SFR. Show that over the last ~5 Gyr of cosmic time there has been substantial evolution in the [OII] emission line luminosity function, with L* decreasing by ~0.6pm0.2 dex in the observed function, and by ~0.9pm0.2 dex in the de-reddened relation. Accompanying this decline is a significant shift in the distribution of [OII] equivalent widths, with the fraction of high equivalent-width emitters declining dramatically with time. Overall, the data imply that athe relative intensity of SF within galaxies has decreased over the past ~5 Gyr, and that the SFR density of the universe has declined by a factor of ~2.5 between z~0.5 and 0.
1304.5557
The dark side of galaxy color
Hearin, Watson
"Age distribution matching": a new theoretical formalism for predicting how galaxies of luminosity L and color C occupy dark matter haloes. Model supposes that there are just two fundamental properties of a halo that determine the color and brightness of the galaxy it hosts: the maximum circular velocity Vmax, and the redshift at which the galaxy will be starved of cold gas z_starve. The halo property z_starve is intended to encompass physical characteristics of a halo's mass assembly history (MAH) that may deprive the galaxy of its cold gas supply and, ultimately, quench its star formation. These include the epochs when: (a) a halo accretes onto a large halo, z_acc, (b) a halo reaches a characteristic mass (~1e12 Msun/h), z_char, and (c) a halo transitioned from the fast- to slow-accretion regime, z_form. A halo's z_starve value is determined by whichever of these events happens first in its MAH. The new, defining feature of the model is that, at fixed L, galaxy color is in monotonic correspondence with z_starve with the larger values of z_starve being assigned redder colors. Populate the Bolshoi N-body simulation with a mock galaxy catalog based on age distribution matching, and show that the resulting mock galaxy distribution accurately describes the luminosity- and color-binned two-point correlation function of galaxies in SDSS, as well as a variety of low-redshift galaxy group statistics. Study of the property z_starve has important implications for how halo MAH influences stellar mass assembly. For example, the significance of the epoch z_form suggests a new, independent channel for so-called "mass quenching" based on the rate of halo mass accretion. Make publicly available the low-z, SDSS Mr<-19 mock galaxy catalog, and main progenitor histories of all z=0 Bolshoi halos.
1304.5573
Mean spectral energy distributions and bolometric corrections for luminous quasars
Krawczyk, Richards, Mehta, Vogeley, ... Ross, Schneider
UV to MIR SEDs of 119k luminous broad-lined quasars with 0.064<z<5.46 from Spitzer and WISE (MIR), 2MASS and UKIDSS (NIR), SDSS (optical), and GalEx (UV). The mean SED requires a bolometric correction (relative to 2500A) of BC=2.75pm0.40 using the integrated light from 1um-2keV, and further explore the range of bolometric corrections for each object. Investigate the dependence of the mean SED on various parameters, particularly the UV luminosity for quasars with 0.5<z<3 and the properties of the UV emission lines for quasars with z>1.6; the latter is a possible indicator of the strength of the accretion disk wind, which is expected to be SED dependent. L-dependent mean SEDs show that, relative to the high-L SED, low-L SEDs exhibit a harder FUV spectral slope, a redder optical continuum, and less host dust. Mean SEDs constructed instead as a function of UV emission line properties reveal changes that are consistent with known PCA trends. A potentially important contribution to the bolometric correction is the unseen E-UV continuum. Lower-L quasars and/or quasars with disk-dominated broad emission lines may require an extra continuum component in the EUV that is not present in high-L quasars with strong accretion disk winds. Consider 4 possible models and explore the resulting bolometric corrections. Important to accurate determination of quasar accretion rates.
1304.5738
Microlensing in globular clusters: the first confirmed lens
Jetzer
As the title says.
Day 417
Monday.
1304.5414
Limits on compact halo objects as dark matter from gravitational microlensing
Jetzer
Short review on this topic.
1304.5443
Joint reconstruction of galaxy clusters from gravitational lensing and tehrmal gas I. Outline of a non-parametric method
Konrad, Majer, Meyer, Sarli, Bartelmann
Method to estimate lensing potential from massive galaxy clusters, given observational X-ray data; can easily be combined with other techniques such as WL or kinematics. Test reconstruction method on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. Test the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. Statistical/systematic error below 2.0/1.0%.
1304.5489
Disturbances in the U.S. electric grid associated with geomagnetic activity
Schrijver, Mitchell
Data from 1992 to 2010: find that ~4% of the disturbances in the power grid reported to the DoE are attributable to strong geomagnetic activity and associated geomagnetically induced currents.
1304.5414
Limits on compact halo objects as dark matter from gravitational microlensing
Jetzer
Short review on this topic.
1304.5443
Joint reconstruction of galaxy clusters from gravitational lensing and tehrmal gas I. Outline of a non-parametric method
Konrad, Majer, Meyer, Sarli, Bartelmann
Method to estimate lensing potential from massive galaxy clusters, given observational X-ray data; can easily be combined with other techniques such as WL or kinematics. Test reconstruction method on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. Test the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. Statistical/systematic error below 2.0/1.0%.
1304.5489
Disturbances in the U.S. electric grid associated with geomagnetic activity
Schrijver, Mitchell
Data from 1992 to 2010: find that ~4% of the disturbances in the power grid reported to the DoE are attributable to strong geomagnetic activity and associated geomagnetically induced currents.
Sunday, April 21, 2013
Day 416
Sunday.
1304.4932
How realistic are solar model atmospheres?
Pereira et al
Conclude that the 3D hydrodynamical model is superior to any of the tested 1D models, which gives further confidence in the solar abundance analysis based on it.
1304.4933
Spatially unassociated galaxies contribute significantly to the blended submillimetre galaxy population: predictions for follow-up observations of ALMA sources
Hayward, Behroozi, Somerville, Primack, Moreno, Wechsler
From mock SMG catalogs, calculate submm number counts for different beam sizes and without blending. Model suggests that there are a sufficient number of blended SMGs to account for the observed number counts of submm sources with 850-um flux density S_850>~12 mJy. Furthermore, predict that 30-80% of blended SMGs have at least one spatially unassociated component. For a 15-arcsec beam, blends of >2 galaxies in which at least once component is spatially unassociated dominate the blended sources with total S_850>~3mJy. The distribution of the redshift separations amongst the components is strongly bimodal. The typical redshift separation of spatially unassociated blended sources is ~1. Predictions for the contributions of spatially unassociated components and the distribution of redshift separations are not testable with currently available data, but they will be easily tested once sufficiently accurate z for the individual subcomponents (by e.g., ALMA) of a sufficient number of single-dish-detected blended SMGs are available.
1304.4937
Further evidence for a supermassive black hole mass - pitch angle relation
Berrier, et al
New and stronger evidence for relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M_BH of a disk galaxy's nuclear SMBH. Find the relation log(M/Msun)=8.21-0.062*P. Can be used as a SMBH mass predictor.
1304.4940
A fundamental relation between the metallicity, gas content, and stellar mass of local galaxies
Bothwell et al
Mass-metallicity relation has a strong dependence on the SFR. Use a sample of 4253 local galaxies observed in atomic hydrogen from ALFALFA survey to demonstrate that a similar fundamental relation (the HI-FMR) also exists between stellar mass, gas-phase metallicity, and HI mass. The latter relation is likely more fundamental, driving the relation between metallicity, SFR and mass. At intermediate mass, gas metallicity and star metallicity relation similar, but find that the dependence of metallicity on HI content persists to the highest stellar masses, in contrast to the 'saturation' of metallicity with SFR. It is interesting to note that the dispersion of the relation is very low at intermediate stellar masses (1e9<M*<1e11), suggesting that in this range galaxies evolve smoothly, in an equilibrium between gas inflow, outflow and SF. At high and low stellar masses, the scatter of the relation is significantly higher, suggesting that merging events and/or stochastic accretion and SF may drive galaxies outside the relation. Also assemble a sample of galaxies observed in CO, but small sample, strong selection bias, and influence of metallicity-dependent CO/H2 conversion factor, the data are insufficient to test any influence of molecular gas on metallicity.
1304.4992
Toward understanding the anisotropic point spread function of Suprime-Cam and its impact on cosmic shear measurement
Hamana, Miyazaki, Okura, Okamura, Futamase
Decompose PSF into 3 components, the optical aberration, atmospheric turbulence and chip-misalignment in an empirical manner, and evaluate the amplitude of each component. Find that, for long-exposure data, the optical aberration has the largest contribution to the PSF ellipticities, which can be modeled well by a simple analytic function based on the lowest-order aberration theory. Statistical properties of PSF ellipticities originated from the atmospheric turbulence are investigated by using numerical simulation, and it is found that simulation results are in a reasonable agreement with the observed data. It is also found that the optical PSF can be well corrected by the standard correction method with polynomial fitting function. However, for the atmospheric PSF, its correction suffers from the common limitation arisen from sparse sampling of PSFs due to a limited number of stars. Also examine effects of the residual PSF anisotropies on Suprime-Cam cosmic shear data. Find that the shape and amplitude of B-mode shear variance are broadly consistent with those of the residual PSF ellipticities measured from the dense star field data. This indicates that most of the sources of residual systematic are understood, which is an important step for cosmic shear statistics to be a practical tool of the precision cosmology.
1304.5017
Small planetesimals in a massive disk formed Mars
Kobayashi, Dauphas
As the titles says.
1304.5062
Exact general relativistic lensing versus thin lens approximation: the crucial role of the void
Mood, Firouzjaee, Mansouri
Study exact GR model structure of gravitational lensing of cosmological structure within a FRW cosmological BG based on LTB metric. Integration of geodesic equation: Some ranks of Runge-Kutta numerical integrators leads to numerical effects, and is therefore unreliable. The semi-implicit Rosenbrock method is a viable integration method. Compare with thin lens approximation. Show: independent of the NFW truncation details, the thin lens approximation differ substantially from the exact relativistic calculation; the difference in the deflection angle for different impact parameters may be up to about 30 percent. However, using the modified NFW density profile with a void before going over the FRW background, the thin lens approximation coincides almost exactly with the GR calculation. [so... FG structure affects halo mass estimates?]
1304.4932
How realistic are solar model atmospheres?
Pereira et al
Conclude that the 3D hydrodynamical model is superior to any of the tested 1D models, which gives further confidence in the solar abundance analysis based on it.
1304.4933
Spatially unassociated galaxies contribute significantly to the blended submillimetre galaxy population: predictions for follow-up observations of ALMA sources
Hayward, Behroozi, Somerville, Primack, Moreno, Wechsler
From mock SMG catalogs, calculate submm number counts for different beam sizes and without blending. Model suggests that there are a sufficient number of blended SMGs to account for the observed number counts of submm sources with 850-um flux density S_850>~12 mJy. Furthermore, predict that 30-80% of blended SMGs have at least one spatially unassociated component. For a 15-arcsec beam, blends of >2 galaxies in which at least once component is spatially unassociated dominate the blended sources with total S_850>~3mJy. The distribution of the redshift separations amongst the components is strongly bimodal. The typical redshift separation of spatially unassociated blended sources is ~1. Predictions for the contributions of spatially unassociated components and the distribution of redshift separations are not testable with currently available data, but they will be easily tested once sufficiently accurate z for the individual subcomponents (by e.g., ALMA) of a sufficient number of single-dish-detected blended SMGs are available.
1304.4937
Further evidence for a supermassive black hole mass - pitch angle relation
Berrier, et al
New and stronger evidence for relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M_BH of a disk galaxy's nuclear SMBH. Find the relation log(M/Msun)=8.21-0.062*P. Can be used as a SMBH mass predictor.
1304.4940
A fundamental relation between the metallicity, gas content, and stellar mass of local galaxies
Bothwell et al
Mass-metallicity relation has a strong dependence on the SFR. Use a sample of 4253 local galaxies observed in atomic hydrogen from ALFALFA survey to demonstrate that a similar fundamental relation (the HI-FMR) also exists between stellar mass, gas-phase metallicity, and HI mass. The latter relation is likely more fundamental, driving the relation between metallicity, SFR and mass. At intermediate mass, gas metallicity and star metallicity relation similar, but find that the dependence of metallicity on HI content persists to the highest stellar masses, in contrast to the 'saturation' of metallicity with SFR. It is interesting to note that the dispersion of the relation is very low at intermediate stellar masses (1e9<M*<1e11), suggesting that in this range galaxies evolve smoothly, in an equilibrium between gas inflow, outflow and SF. At high and low stellar masses, the scatter of the relation is significantly higher, suggesting that merging events and/or stochastic accretion and SF may drive galaxies outside the relation. Also assemble a sample of galaxies observed in CO, but small sample, strong selection bias, and influence of metallicity-dependent CO/H2 conversion factor, the data are insufficient to test any influence of molecular gas on metallicity.
1304.4992
Toward understanding the anisotropic point spread function of Suprime-Cam and its impact on cosmic shear measurement
Hamana, Miyazaki, Okura, Okamura, Futamase
Decompose PSF into 3 components, the optical aberration, atmospheric turbulence and chip-misalignment in an empirical manner, and evaluate the amplitude of each component. Find that, for long-exposure data, the optical aberration has the largest contribution to the PSF ellipticities, which can be modeled well by a simple analytic function based on the lowest-order aberration theory. Statistical properties of PSF ellipticities originated from the atmospheric turbulence are investigated by using numerical simulation, and it is found that simulation results are in a reasonable agreement with the observed data. It is also found that the optical PSF can be well corrected by the standard correction method with polynomial fitting function. However, for the atmospheric PSF, its correction suffers from the common limitation arisen from sparse sampling of PSFs due to a limited number of stars. Also examine effects of the residual PSF anisotropies on Suprime-Cam cosmic shear data. Find that the shape and amplitude of B-mode shear variance are broadly consistent with those of the residual PSF ellipticities measured from the dense star field data. This indicates that most of the sources of residual systematic are understood, which is an important step for cosmic shear statistics to be a practical tool of the precision cosmology.
1304.5017
Small planetesimals in a massive disk formed Mars
Kobayashi, Dauphas
As the titles says.
1304.5062
Exact general relativistic lensing versus thin lens approximation: the crucial role of the void
Mood, Firouzjaee, Mansouri
Study exact GR model structure of gravitational lensing of cosmological structure within a FRW cosmological BG based on LTB metric. Integration of geodesic equation: Some ranks of Runge-Kutta numerical integrators leads to numerical effects, and is therefore unreliable. The semi-implicit Rosenbrock method is a viable integration method. Compare with thin lens approximation. Show: independent of the NFW truncation details, the thin lens approximation differ substantially from the exact relativistic calculation; the difference in the deflection angle for different impact parameters may be up to about 30 percent. However, using the modified NFW density profile with a void before going over the FRW background, the thin lens approximation coincides almost exactly with the GR calculation. [so... FG structure affects halo mass estimates?]
Thursday, April 18, 2013
Day 415
Thursday.
1304.4594
Real or Interloper? The redshift likelihoods of galaxies in the HUDF12
Pirzkal, ... Coe, ... et al
SED fitting has become the workhorse for identifying high-z galaxies. Present analysis of the most recent and possibly most distant galaxies discovered in HUDF using a more robust method of z estimation based on MCMC, rather than relying on "best fit" models obtained using common chi^2 minimization techniques. Advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift, as well as any other input model parameters, allowing us to derive accurate credible intervals by properly marginalizing over all other input model parameters. Apply method to 13 recently identified sources and show that, despite claims based on chi^2 minimization, none of these sources can be securely ruled out as low z interlopers given the low signal-to-noise of currently available observations. Estimate that there is an average probability of 21% that these sources are low z interlopers.
1304.4601
The biggest explosions in the universe
Johnson, et al
SM primordial stars expected to form in small fraction of massive protogalaxies in early universe; generally concieved as the progenitors of the seeds of SMBHs at high z. SM stars with masses of 55k Msun have been found [in simulations?] to explode and completely disrupt in a SN with an energy of up to 1e55 erg, instead of collapsing to a BH. Such events, roughly 10k times more energetic than a typical SNe today, would be among the biggest explosions in the history of the universe. Carry out a simulation of such a SM star SN in 2 stages. Using the RAGE radiation hydrodynamics code, first evolve the explosion from the earliest stages, through the breakout of the shock from the surface of the star until the blast wave has propagated out to several parsecs from the explosion site, which lies deep within an atomic cooling DM halo at z~15. Then, using the GADGET cosmological hydrodynamics code, evolve the explosion out to several kpcs from the explosion site, far into the low-density IGM. The host DM halo, with a total mass of 4e7 Msun, much more massive than typical primordial star forming haloes, is completely evacuated of high density gas after < 10 Myr, although dense metal-enriched gas re-collapses into the halo, where it will likely form second-generation stars after > 70 Myr. The 20k Msun in metals that are released in the explosion are widely distributed, and enrich the dense re-collapsing gas to an average metallicity of ~0.05 Z_sun. Such a high level of enrichment suggests that the chemical signature of these SM star explosions may have been missed in previous surveys of metal-poor stars.
1304.4622
Serendipitous discovery of a massive cD galaxy at z=1.096: Implications for the early formation and late evolution of cD galaxies
Liu, ... Grogin, et al
As the title says. ... Such increases in size and stellar mass without being accompanied by significant increases in velocity dispersion are consistent with evolutionary scenarios driven by both major and minor dry mergers. Such high-z cDs may be more common that expected.
1304.4646
Constraints on the shape of the Milky Way dark matter halo from the Sagittarius stream
Vera-Ciro, Helmi
New model for the DM halo of MW that fits the properties of the stellar stream associated with the Sagittarius dwarf galaxy. It is oblate with q=0.9 for r<10kpc. The outer halo can be made mildly triaxial, with minor-to-major axis ratio (c/a)_\Phi=0.8 and (b/a)_Phi=0.9, if the effect of LMC is taken into account. Therefore this new model takes into account the flattening induced by the presence of the Galactic disk and is also more consistent with cosmological expectations.
1304.4656
Reducing systematic error in cluster scale weak lensing
Utsumi et al
2 procedures efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. Provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the WL kappa-SN maps as a function of the detection threshold. Based on this analysis, select a threshold S/N=4.56 for identifying an uncontaminated set of WL peaks in two test fields covering a total area of ~3 deg^2. Taken together these fields contain 7 peaks above the threshold. Among these, 6 are probably systems of galaxies and one is a superposition. Confirm the reliability of these peaks with dense redshift surveys, x-ray and imaging observations. The systematic error reduction procedures applied are general and can be applied to future large-area W surveys. The high peak analysis suggests that with a S/N threshold of 4.5, there should be only 2.7 spurious WL peaks even in an area of 1000 deg^2 where ~2000 peaks are expected.
1304.4719
Host galaxies of Type Ia Supernovae from the Nearby Supernova Factory
Childress, et al
Analysis (M*, SFRs, dust reddening) indicates that SNIa host galaxies are on average, typical representatives of normal field galaxies.
1304.4720
Host galaxy properties and Hubble residuals of tyep Ia supernovae from the nearby supernova factory
Childress, et al
Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, illustrate here how dust in SF galaxies and mean SNIa progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SNIa host bias.
1304.4781
A quasi-Gaussian approximation for the probability distribution of correlation functions
Wilking, Schneider
Likelihood function of correlation functions must be known, to infer cosmological parameters in the context of Bayesian analysis from correlation functions. Show how to calculate a better approximation for the probability distribution of correlation functions---dubbed "quasi-Gaussian". Use the exact univariate PDF and constraints on correlation functions previously derived, transform the correlation functions to an unconstrained variable for which the Gaussian approximation is well justified. From this Gaussian in the transformed space, obtain the quasi-Gaussian PDF. The two approximations for the probability distributions are compared to the "true" distribution as obtained from simulations. Test how the new approximation performs when used as likelihood in a toy-model Bayesian analysis. The quasi-Gaussian PDF agrees very well with the PDF obtained from simulations; in particular, it provides a significantly better description than a straightforward coupla approach. In a simple toy-model likelihood analysis, it yields noticeably different results than the Gaussian likelihood, indicating its possible impact on cosmological parameter estimation.
1304.4594
Real or Interloper? The redshift likelihoods of galaxies in the HUDF12
Pirzkal, ... Coe, ... et al
SED fitting has become the workhorse for identifying high-z galaxies. Present analysis of the most recent and possibly most distant galaxies discovered in HUDF using a more robust method of z estimation based on MCMC, rather than relying on "best fit" models obtained using common chi^2 minimization techniques. Advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift, as well as any other input model parameters, allowing us to derive accurate credible intervals by properly marginalizing over all other input model parameters. Apply method to 13 recently identified sources and show that, despite claims based on chi^2 minimization, none of these sources can be securely ruled out as low z interlopers given the low signal-to-noise of currently available observations. Estimate that there is an average probability of 21% that these sources are low z interlopers.
1304.4601
The biggest explosions in the universe
Johnson, et al
SM primordial stars expected to form in small fraction of massive protogalaxies in early universe; generally concieved as the progenitors of the seeds of SMBHs at high z. SM stars with masses of 55k Msun have been found [in simulations?] to explode and completely disrupt in a SN with an energy of up to 1e55 erg, instead of collapsing to a BH. Such events, roughly 10k times more energetic than a typical SNe today, would be among the biggest explosions in the history of the universe. Carry out a simulation of such a SM star SN in 2 stages. Using the RAGE radiation hydrodynamics code, first evolve the explosion from the earliest stages, through the breakout of the shock from the surface of the star until the blast wave has propagated out to several parsecs from the explosion site, which lies deep within an atomic cooling DM halo at z~15. Then, using the GADGET cosmological hydrodynamics code, evolve the explosion out to several kpcs from the explosion site, far into the low-density IGM. The host DM halo, with a total mass of 4e7 Msun, much more massive than typical primordial star forming haloes, is completely evacuated of high density gas after < 10 Myr, although dense metal-enriched gas re-collapses into the halo, where it will likely form second-generation stars after > 70 Myr. The 20k Msun in metals that are released in the explosion are widely distributed, and enrich the dense re-collapsing gas to an average metallicity of ~0.05 Z_sun. Such a high level of enrichment suggests that the chemical signature of these SM star explosions may have been missed in previous surveys of metal-poor stars.
1304.4622
Serendipitous discovery of a massive cD galaxy at z=1.096: Implications for the early formation and late evolution of cD galaxies
Liu, ... Grogin, et al
As the title says. ... Such increases in size and stellar mass without being accompanied by significant increases in velocity dispersion are consistent with evolutionary scenarios driven by both major and minor dry mergers. Such high-z cDs may be more common that expected.
1304.4646
Constraints on the shape of the Milky Way dark matter halo from the Sagittarius stream
Vera-Ciro, Helmi
New model for the DM halo of MW that fits the properties of the stellar stream associated with the Sagittarius dwarf galaxy. It is oblate with q=0.9 for r<10kpc. The outer halo can be made mildly triaxial, with minor-to-major axis ratio (c/a)_\Phi=0.8 and (b/a)_Phi=0.9, if the effect of LMC is taken into account. Therefore this new model takes into account the flattening induced by the presence of the Galactic disk and is also more consistent with cosmological expectations.
1304.4656
Reducing systematic error in cluster scale weak lensing
Utsumi et al
2 procedures efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. Provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the WL kappa-SN maps as a function of the detection threshold. Based on this analysis, select a threshold S/N=4.56 for identifying an uncontaminated set of WL peaks in two test fields covering a total area of ~3 deg^2. Taken together these fields contain 7 peaks above the threshold. Among these, 6 are probably systems of galaxies and one is a superposition. Confirm the reliability of these peaks with dense redshift surveys, x-ray and imaging observations. The systematic error reduction procedures applied are general and can be applied to future large-area W surveys. The high peak analysis suggests that with a S/N threshold of 4.5, there should be only 2.7 spurious WL peaks even in an area of 1000 deg^2 where ~2000 peaks are expected.
1304.4719
Host galaxies of Type Ia Supernovae from the Nearby Supernova Factory
Childress, et al
Analysis (M*, SFRs, dust reddening) indicates that SNIa host galaxies are on average, typical representatives of normal field galaxies.
1304.4720
Host galaxy properties and Hubble residuals of tyep Ia supernovae from the nearby supernova factory
Childress, et al
Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, illustrate here how dust in SF galaxies and mean SNIa progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SNIa host bias.
1304.4781
A quasi-Gaussian approximation for the probability distribution of correlation functions
Wilking, Schneider
Likelihood function of correlation functions must be known, to infer cosmological parameters in the context of Bayesian analysis from correlation functions. Show how to calculate a better approximation for the probability distribution of correlation functions---dubbed "quasi-Gaussian". Use the exact univariate PDF and constraints on correlation functions previously derived, transform the correlation functions to an unconstrained variable for which the Gaussian approximation is well justified. From this Gaussian in the transformed space, obtain the quasi-Gaussian PDF. The two approximations for the probability distributions are compared to the "true" distribution as obtained from simulations. Test how the new approximation performs when used as likelihood in a toy-model Bayesian analysis. The quasi-Gaussian PDF agrees very well with the PDF obtained from simulations; in particular, it provides a significantly better description than a straightforward coupla approach. In a simple toy-model likelihood analysis, it yields noticeably different results than the Gaussian likelihood, indicating its possible impact on cosmological parameter estimation.
Wednesday, April 17, 2013
Day 414
Wednesday.
1304.3726
Are z~5 QSOs found in the most massive high redshift over-densities?
Husband, et al
High-z QSOs likely markers for biased, over-dense regions where early galaxies cluster, regions that eventually grow into the groups and clusters seen in the lower z universe. Explore the clustering of galaxies around z~5 as traced by LBGs (Lyman break galaxies). Target fields of 3 QSOs using optical imaging and spectroscopy techniques used in ESO remote galaxy survey, which was successful in identifying individual clustering structures of LBGs. Use the statistics of the redshift clustering in ERGS to show that two of the 3 fields show significant clustering of LBGs at the QSO redshifts. Neither of these fields is obviously over-dense in LBGs from the imaging alone; a possible reason why previous imaging-only studies of high-z QSO environments have given ambiguous results. This result shows that luminous QSOs at z~5 are typically found in over-dense regions. The richest QSO field contains at least 9 spectroscopically confirmed objects at the same z including the QSO itself, 7 LBGs and a second fainter QSO. While this is a very strong observational signal of clustering at z~5, it is of similar strength to that seen in two structures identified in the 'blank sky' ERGS fields. This indicates that, while over-dense, the QSO environments are not more extreme than other structures that can be identified at these redshifts. The three richest structures discovered in this work and in ERGS have properties consistent with that expected for proto-clusters and likely represent the early stages in the build-up of massive current-day groups and clusters.
1304.3735
Kronoseismology: using density waves in Saturn's C ring to probe the planet's interior
Hedman, Nicholson
Investigate origin of 6 unidentified C-ring waves. Measure differences in the wave's phases among the different occultations, determine both the number of arms in each spiral pattern and the speeds at which these patterns rotate around the planet. Find all 6 waves have between 2 and 4 arms, and pattern speeds between 1660 deg/day and 1861 deg/day. Speeds too large to be attributed to any satellite resonance; insteand they are comparable to the predicted pattern speeds of waves generated by low-order normal-mode oscillations within the planet. Precise pattern speeds associated with these waves should therefore provide strong constraints on Saturn's internal structure. Identify multiple waves with the same number of arms and very similar pattern speeds, indicating that multiple m=3 and 2 sectoral (l=m) modes may exist within the planet.
1304.4043
Constraints on early Mars atmospheric pressure inferred from small ancient craters
Kite, Williams, Luas, Aharonson
Thinner past atmosphere will yield smaller minimum-sized craters that form. If Mars did not have a stable multibar atmosphere at the time that the rivers were flowing, it rules out warm-wet CO2 greenhouse model; long-term average temperatures were probably below freezing. Implies exoplanet habitable-zone calculations using Mars as a reference point may need to be reconsidered.
1304.4227
Discovery of Lyman break galaxies at z~7 from the ZFOURGE survey
Tilvi, ... van Dokkum, ... Glazebrook, ... Koekemoer, et al
Present 3 candidates for z~7 LBGs from 155 arcmin^2 area in the CANDELS/COSMOS field imaged by the zFourGE survey. The FourStar medium-band filters provide the equivalent of R~10 spectroscopy, which cleanly distinguishes between z~7 LBGs and brown dwarf stars. The distinction between stars and galaxies based on an object's angular size can become unreliable even when using HST imaging; there exists at least one very compact z~7 candidate that is indistinguishable from a point source. The medium-band filters provide narrower redshift distributions compared with borad-band-derived redshifts. The UV luminosity function derived using the three z~7 candidates is consistent with previous studies, suggesting an evolution at the bright end (MUV -21.6 mag) from z~7 to 5. Fitting the galaxies' SED, predict Lyman-alpha equivalent widths for the two brightest LBGs, and find that the presence of a Lyman-alpha line affects the medium-band flux thereby changing the constraints on stellar masses and UV spectral slopes. This illustrates the limitations of deriving LBG properties using only broad-band photometry. The derived specific star-formation rates for the bright LBGs are ~13 per Gyr, slightly higher than the lower-luminosity LBGs, implying that the star-formation rate increases with stellar mass for these galaxies.
1304.4228
Nonlinear stochastic biasing of haloes: analysis of cosmological N-body simulations and perturbation theories
Sato, Matsubara
Use 40 large cosmo N-body sims for standard LCDM, study the X-correlation coefficient between matter and halo density field, which is an indicator of stochasticity of bias, over a wide redshift range 0<z<3. The cross-correlation coefficient is important to extract information on the matter density field, by e.g. combining galaxy clustering and gg-lensing measurements. Compare the simulation results with integrated perturbation theory (iPT) and standard perturbation theory (SPT) combined with a phenomenological model of local bias. The X-correlation coefficient derived from the iPT agrees with N-body sims results down to r~15(10) Mpc/h within 0.5%(1.0%) for all redshifts, while roughly reproduces general behavior of the X-correlation coefficient on fully NL scales. The iPT is powerful to predict the X-correlation coefficient down to quasi-linear regimes with a high precision.
1304.4256
A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34
Riechers, ... Aguirre, ... Cooray, et al
As the title says.
1304.4265
CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing
Valender, Uitert, Hoekstra, ... et al
G-g lensing halo model, constrain halo mass and satellite fraction; analysis is limited to lenses at redshifts between 0.2 and 0.4. Express relationship between halo mass and baryonic observable as a power law. Luminosity-halo mass relation, find a slope and normalization for red and blue galaxies. Do it also for stellar mass -halo mass relation. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity of stellar mass. Blue galaxies reside in less clustered environments than red galaxies. Also find that the halo model, while matching the lensing signal around red lenses, is prone to over-predicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.
1304.4399
Testing the local-void alternative to dark energy using galaxy pairs
Wang, Dai
The distribution of orientations of galaxy pairs can be used to test the Copernican principle that we are not in a central or special region of Universe. The popular void models can not fit both the latest type Ia SNe, CMB data and the distribution of orientations of galaxy pairs simultaneously. Results rule out the void models at the 4 sigma confidence level as the origin of cosmic acceleration and favor the Copernican principle.
1304.4446
What have we learned from observational cosmology?
Hamilton
Review observational foundations of LCDM model; Cosmological Principle is shown to be verified with increasing accuracy. Hot BB supported by many probes. Measurement of cosmological parameters. within FLRW cosmologies, leading to LCDM model: an apparently flat Universe, dominated by a cosmological constant, whose matter component is dominantly dark. Describe and discuss the various observational probes that lead to this conclusion and conclude that the LCDM model, although leaving a number of open questions concerning the deep nature of the constituents of the Universe, provides the best theoretical framework to explain the observations.
1304.4474
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XII. Time delays of the doubly lensed quasars SDSS J1206+4332 and HS 2209+1914
Eulaers et al
4 different techniques used to determine time delay of light curves: dispersion method, spline fit, a regression difference technique, and a numerical model fit; minimizes bias. 111.3 days and 20.0 days for the two multiply lensed quasars.
1304.4493
The Tully-Fisher relations for Hickson Compact Group galaxies
Torres-Flores et al
Most of Hickson compact group [merging, with complex morphologies] galaxies lie on the K-band Tully-Fisher relation defined by field galaxies with a few low-mass outliers, which appear to have had strong recent burst of SF. Strong burst of SF can affect B and K-band luminosities (also AGN activity) without affecting their total mass.
Tuesday, April 16, 2013
Day 413
Tuesday.
1304.3465
Turbulence driven by structure formation in the circum-galactic medium
Iapichino, Viel, Borgani
Use mesh-based hydro code Enzo with sub-grid-scale (SGS) model for unresolved turbulence, to investigate injection of turbulence in circum-galactic medium at z=2. Include radiative cooling and heating by uniform UV BG; compared with the effect of turbulence modeling. Mechanisms of gas exchange between galaxies and the surrounding medium, as well as metal enrichment, are not taken into account, and turbulence is here driven solely by structure formation (mergers and shocks). Find that turbulence, both at resolved and SGS scales, impacts mostly the WHIM, with 1e5<T<1e7 K, mainly located around collapsed and shock heated structures, and in filaments. Typical values of the ratio of turbulent to thermal pressure is 0.1 in the WHIM, corresponding to a volume-weighted average of the SGS turbulent to thermal Doppler broadening b_t/b_therm = 0.26, on length scales below the grid resolution of 25 kpc/h. In the diffuse IGM, defined in a range of baryon over density /delta/ between 1 and 50, the importance of turbulence is smaller, but grows as a function of gas density, and the Doppler broadening ratio is fitted by the function b_t/ b_therm = 0.023 /delta^0.58.
1304.3466
Composition of low redshift halo gas
Cen
Halo gas in z<0.5, >0.1L* galaxies in high-res, large-scale cosmo hydro sims is examined with respect to 3 components: (cold, warm, hot) with temperatures equal to <1e5, 1e5-6, >1e6K, respectively. Warm component agree to observations wrt galaxy-O VI line correlation, etc. Detailed account of sources of warm halo gas (stellar feedback heating, gravitational shock heating and accretion from IGM), inflowing and outflowing warm halo gas metallicity disparities and their dependencies on galaxy types and environment is also presented. Predict: (1) cold gas is the primary component in inner regions, with its mass comprising 50% of all gas within galacto-centric radius r=(30,150) kpc in (red, blue) galaxies. (2) at r>(30,200)kpc in (red, blue) galaxies, the hot component becomes the majority. (3) the warm component is a perpetual minority, with its contribution peaking at ~30% at r=100-300kpc in blue galaxies, and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies found in simulations, in agreement with recent observations (Thom et al.), is intriguing, so is the dominance of hot gas at large radii in blue galaxies.
1304.3474
The synergy between the Dark Energy Survey and the South Pole Telescope
Vallinotto
DES has 150 sq. deg in Science Verification phase. Forecast for DES-SV and full survey of 5000 sq. deg. DES-SV and SPT-SZ allow a ~8% measurement of the linear galaxy bias in 4 redshift bins. Further show that a joint analysis of cosmic shear, galaxy density and CMB lensing data allows to self calibrate the shear multiplicative bias and the linear galaxy bias to the percent or sub-percent level, depending on the quality of available data, fraction of overlap of the footprints and priors included in the analysis.
1304.3492
Estimating gas masses and dust-to-gas ratios from optical spectroscopy
Brinchmann, Charlot, Kauffmann, Heckman, White, Tremonti
Exploit the sensitivity of certain optical lines to changes in depletion of metals onto dust grains and uses photo-ionization models to constrain these physical ratios along with Z and dust column density. Technique independent of conversion factor of CO to H2; show Z-dependent XCO is required to achieve good agreement between measurements and those provided by CO and HI. This method cannot be reliably aperture corrected to total gas mass. Compare results to SDSS DR7 galaxies, Z dependence agrees well with FIR data [FIR presumably from heated dust]. ...
1304.3665
The cosmic X-ray background: abundance and evolution of hidden black holes
Gilli
Review paper of XRB. XRB spectral shape suggests a large population of distant, hidden nuclei must exist, now being revealed at higher and higher z by Chandra and XMM.
1304.3715
A resolution of the cosmic Lithium problem
Ouyed
A quark-novae (QNe) occurring in the wake of Pop III stars.
1304.3717
Linking X-ray AGN with DM haloes: a model compatible with AGN luminosity function and large-scale clustering properties
Hütsi, Gilfanov, Sunyaev
Assume a simple population-averaged scaling relation between AGN X-ray Luminosity L_X and the host dark matter halo mass M_h exists: then L_X LF can be computed from halo mass function. Find M_h-L_X relation required to match the z-dependent AGN X-ray luminosity function known from X-ray observations. Find that with the simple power law scaling M_h propto L_X^Gamma(z), model can successfully reproduce the observed X-ray luminosity function. .... Suggest that the typical X-ray AGN are dominantly fueled via relatively inefficient 'hot-halo' accretion mode.
1304.3724
New constraints on the early expansion history
Hojjati, Linder, Samsing
Test early universe's expansion rate and constituents such as effective number of relativistic degrees of freedom and DE with the most recent data from Planck and WMAP9. Constraint expansion history in a model independent manner from z=0 to 1e5. Hubble parameter mapped to a few precent precision, limiting early DE and extra relativistic degrees of freedom within a model independent approach to 2-16% and 0.71 equivalent neutrino species respectively (95% CL). Within dark radiation, barotropic aether, and Doran-Robbers models, the early DE constraints are 3.3%, 1.9%, and 1.2% respectively.
1304.4124
Gravitational redshifts from large-scale structure
Croft
Use halo model of clustering to predict the distortion due to gravitational redshifts of the cross-correlation function on scales from 1-100 Mpc/h. Compare predictions to simulations and use the simulations to make mock catalogues relevant to current and future galaxy redshift surveys. Without formulating an optimal estimator, find that the full BOSS survey would be able to detect gravitational redshifts from large-scale structure at the 4 sigma level. Upcoming z surveys will greatly increase the number of galaxies; BigBOSS and Euclid should be capable of measurements with precision at the few percent level. Other interesting effects including relativistic beaming and transverse Doppler shift can add additional asymmetric distortions to the correlation function. While these contributions are subdominant to the gravitational redshift on large scales, they represent additional opportunities to probe gravitational physics and indicate that many qualitatively new measurements should be possible using large z surveys.
1304.4172
Quasar lensing
Jackson
REview observations of gravitationally lensed quasars. Systems important because they allow us to probe the properties of lensing galaxies at various scales, and also allow insights into the structures of the quasars themselves. Samples of quasar lenses also have the potential to act as cosmographic probes. These areas are described, together with observational and scientific prospects for the future.
Day 412
Monday.
1304.3455
LSST's DC bias against planets and galactic-plane science
Gould
LSST-like survey of Galactic plane (deep images every 3-4 days) could probe the Galactic distribution of planets by two distinct methods: gravitational microlensing of planets beyond the snow line and transits by planets very close to their hosts. Survey would identify over 250 disk-lens/disk-source microlensng events per year that peak at r<19, including 10% reaching the high magnification A>100 that makes them especially sensitive to planets. Intensive followup of these events would be required to find planets, similar to what is done presently for Galactic bulge microlensing. The same data would enable a wealth of other science, including detection of isolated BHs, systematic study of brown-dwarf binaries, a pre-explosion lightcurve of the next Galactic SNe, pre-explosion lightcurves of stellar mergers, early nova lightcurves, proper motions of many more stars than can be reached by GAIA, and probably much more. As usual, the most exciting discoveries from probing the huge parameter space encompassed by Galactic-plane stellar populations might well be serendipitous. Unfortunately, the LSST collaboration plans to exclude the first and fourth quadrants of the Galactic plane from their "synoptic" observations because the DC image that resulted from repeated observations would be limited by crowding. I demonstrate that the majority of the science can be recovered by employing well-developed image subtraction analysis methods, and that the cost to other (high Galactic latitude) science would be negligible.
1304.3456
Convergence of AMR and SPH simulations - I. Hydrodynamical resolution and convergence tests
Hubber, Falle, Goodwin
Compare AMR finite volume code MG and SPH code SEREN. Test suite includes shock tube tests, with and without cooling, the NL thin-shell instability, and the Kelvin-Helmholtz instability. The main conclusions are: (i) the two methods converge in the limit of high resolution and accuracy in most cases. All tests show good agreement when numerical effects (e.g. discontinuities in SPH) are properly treated. (ii) Both methods can capture adiabatic shocks and well-resolved cooling shocks perfectly well with standard prescriptions. However, they both have problems when dealing with under-resolved cooling shocks, or strictly isothermal shocks, at high Mach numbers. The finite volume code only works well at 1st order and even then requires some additional artificial viscosity. SPH requires either a larger value of the artificial viscosity parameter, alpha-AV, or a modified form of the standard artificial viscosity term using the harmonic mean of the density, rather than the arithmetic mean. (iii) Some SPH simulations require larger kernels to increase neighbor number and reduce particle noise in order to achieve agreement with finite volume simulations. However, this is partly due to the need to reduce noise that can corrupt the growth of small-scale perturbations. In contrast, instabilities seeded from large-scale perturbations do not require more neighbors and hence work well with standard SPH formulations and converge with the finite volume simulations. (iv) For purely hydrodynamical problems, SPH simulations take an order of magnitude longer to run than finite volume simulations when running at equivalent resolutions, i.e., when they both resolve the underlying physics to the same degree. This requires about 2-3 times as many particles as the number of cells.
1304.3455
LSST's DC bias against planets and galactic-plane science
Gould
LSST-like survey of Galactic plane (deep images every 3-4 days) could probe the Galactic distribution of planets by two distinct methods: gravitational microlensing of planets beyond the snow line and transits by planets very close to their hosts. Survey would identify over 250 disk-lens/disk-source microlensng events per year that peak at r<19, including 10% reaching the high magnification A>100 that makes them especially sensitive to planets. Intensive followup of these events would be required to find planets, similar to what is done presently for Galactic bulge microlensing. The same data would enable a wealth of other science, including detection of isolated BHs, systematic study of brown-dwarf binaries, a pre-explosion lightcurve of the next Galactic SNe, pre-explosion lightcurves of stellar mergers, early nova lightcurves, proper motions of many more stars than can be reached by GAIA, and probably much more. As usual, the most exciting discoveries from probing the huge parameter space encompassed by Galactic-plane stellar populations might well be serendipitous. Unfortunately, the LSST collaboration plans to exclude the first and fourth quadrants of the Galactic plane from their "synoptic" observations because the DC image that resulted from repeated observations would be limited by crowding. I demonstrate that the majority of the science can be recovered by employing well-developed image subtraction analysis methods, and that the cost to other (high Galactic latitude) science would be negligible.
1304.3456
Convergence of AMR and SPH simulations - I. Hydrodynamical resolution and convergence tests
Hubber, Falle, Goodwin
Compare AMR finite volume code MG and SPH code SEREN. Test suite includes shock tube tests, with and without cooling, the NL thin-shell instability, and the Kelvin-Helmholtz instability. The main conclusions are: (i) the two methods converge in the limit of high resolution and accuracy in most cases. All tests show good agreement when numerical effects (e.g. discontinuities in SPH) are properly treated. (ii) Both methods can capture adiabatic shocks and well-resolved cooling shocks perfectly well with standard prescriptions. However, they both have problems when dealing with under-resolved cooling shocks, or strictly isothermal shocks, at high Mach numbers. The finite volume code only works well at 1st order and even then requires some additional artificial viscosity. SPH requires either a larger value of the artificial viscosity parameter, alpha-AV, or a modified form of the standard artificial viscosity term using the harmonic mean of the density, rather than the arithmetic mean. (iii) Some SPH simulations require larger kernels to increase neighbor number and reduce particle noise in order to achieve agreement with finite volume simulations. However, this is partly due to the need to reduce noise that can corrupt the growth of small-scale perturbations. In contrast, instabilities seeded from large-scale perturbations do not require more neighbors and hence work well with standard SPH formulations and converge with the finite volume simulations. (iv) For purely hydrodynamical problems, SPH simulations take an order of magnitude longer to run than finite volume simulations when running at equivalent resolutions, i.e., when they both resolve the underlying physics to the same degree. This requires about 2-3 times as many particles as the number of cells.
Saturday, April 13, 2013
Day 411
Saturday.
1304.2939
The two regimes of the cosmic sSFR evolution are due to spheroids and discs
Pipino, Calura, Matteucci
Aim to explain the two phases in the observed sSFR, namely the high (>3/Gyr) values at z>2 and the smooth decrease since z=2. In order to do this, compare to observations the sSFR evolution predicted by well calibrated models of chemical evolution for elliptical and spiral galaxies, using the additional constraints on the mean stellar ages of these galaxies (at a given mass). Conclude that the two phases of the sSFR evolution across cosmic time are due to different populations of galaxies. At z>2 the contribution comes from spheroids: the progenitors of present-day massive ellipticals (which feature the highest sSFR) as well as haloes and bulges in spirals (which contribute with average and lower-than-average sSFR). In each single galaxy the sSFR decreases rapidly and the SF stops in <1Gyr. However the combination of different generations of ellipticals in formation might result in an apparent lack of strong evolution of the sSFR (averaged over a population) at high redshift. The z<2 decrease is due to the slow evolution of the gas fraction in discs, modulated by the gas accretion history and regulated by the Schmidt law. The MW makes no exception to this behavior.
1304.2963
Observational evidence that massive cluster galaxies were forming stars at z~2.5 and did not grow in mass at later times
Andreon
As the title says. Related to subject above. Data from Spitzer and LF, MF of galaxies in five z>1.4 clusters. L* does not evolve between z=1 and 1.8. z>1.8 as the remaining epoch for the mass build up.
1304.3124
The impact of global environment of galaxy mass functions at low redshift
Calvi, Poggianti, Vulcani, Fasano
Study the galaxy stellar mass function in different environments in the local Universe, considering both the total mass function and that of individual galaxy morphological types. Compare the MF of galaxies with M*>1e10.25 in the general field and in galaxy groups, binary and single galaxy systems from Padova-Millennium Galaxy and Group Catalog at z=0.04-0.1 with the MF of galaxy clusters of the Wide Field NEarby Galaxy-Cluster Survey at z=0.04-0.07. The variations of the MF with global environment overall are small and subtle. The shapes of the MF of the general field and clusters are indistinguishable (some variation in groups). On the MF of single galaxies, representing the least massive haloes and comprising less than a third of the general field population, is proportionally richer in low-mass galaxies than other environments. The most notable environmental effect is a progressive change in the upper galaxy mass, with very massive galaxies found only in the most massive environments. This environment-dependent mass cut-off is unable to affect the Schechter parameters and the K-S test, and can only be revealed by an ad-hoc analysis. Show how in each given environment, the MF changes with morphological type, and that galaxies of the same morphological type can have different MF in different environments.
1304.3127
A new approach to identifying the most powerful gravitational lensing telescopes
Wong, Zabludoff, Ammons, Keeton, Hogg, Gonzalez
Best GL's for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the LoS. New method for finding such GL telescopes uses optical data to identify projected concentrations of LRGs. LRGs are biased tracers of the underlying mass distribution, so LoS with the highest total luminosity in LRGs are likely to contain the largest total mass. Apply this selection technique to the SDSS and identify the 200 fields with the highest total LRG luminosities projected within a 3.5' radius over 0.1<z<0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56% contain multiple known clusters previously identified in the literature. Thus, results confirm that these LRGs trace massive structures and that selection technique identifies fields with large total masses. These fields contain 2-3 times higher total LRG luminosities than most known SL clusters and will be among the best GL fields for the purpose of detetcing the highest z galaxies.
1304.3171
Exploring the interstellar media of optically compact dwarf galaxies
Most, Cannon, Salzer, Rosenberg, Engstrom, Fliss
Present 8 SF blue compact dwarf galaxies selected to be optically compact (<1 kpc optical radii), with HI spectral data, with archival SDSS and Spizter data. These systems have faint blue absolute magnitudes (M_B>=-17), ongoing SF (based on emission-line selection by the Ha or [OIII] lines), and are nearby (45 Mpc). One sample found to have an HI halo that extends 58 r-band scale lengths from its stellar body. In contrast, the rest of the sample galaxies have HI radii to optical-scale-length ratios ranging from 9.3 to 26. The size of the HI disk in the "giant disk" dwarf galaxy ADBS113845+2008 appears to be unusual as compared to similarly compact stellar populations.
1304.3174
The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the commissioning observations and the pilot surveys
Huo et al
Present 509 new quasars discovered during the 2010 and 2011 observational seasons in ~135 sq. deg, and 17 new in ~100 sq. deg. These bright quasars provide an opportunity to probe the kinematics and chemistry of the ISM/IGM in the Local Group of galaxies, providing a perfect astrometric reference frame to measure the proper motions of M31 and M33, as well as substructures of LG.
1304.3230
FIR-detected Lyman break galaxies at z~3: dust attenuation and dust correction factors at high redshift
Oteo et al
LBGs are SF galaxies in high-z; detection of LBGs in FIR provide clues on their dust attenuation and total SFR. Explore the FIR emission of a sample of 16 LBGs at z~3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100um or PACS-160um. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. Find that PACS-detected LBGs at z~3 are highly obscured galaxies which belong to the ULIRG or HLIRG class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope of their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results [SFR results?] for most of the galaxies. Comparing with a sample of PACS-detected LBGs at z~1, find evidences that the FIR emission of LBGs might have changed with redshift in the sense that the dustiest LBGs found at z~3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z~1.
1304.3335
The evolution of dusty star formation in galaxy clusters to z=1: Spitzer IR observations of the first red-sequence cluster survey
Webb,.. Yee, ... Gladders, et al
From 42 clusters of 1e14-15 Msun in 0.3<z<1.0 from RCS-1, show number of IR luminous galaxies in clusters per unit cluster mass evolves as (1+z)^(5 pm 2); these results assume a single SF galaxy template; the presence of AGN, and an evolution in their relative contribution to the MIR galaxy emission, will alter the overall number counts per cluster and their rate of evolution. Evolution of total SFR per unit cluster mass can be attributed entirely to the change in the in-falling field galaxy population. The SFR per unit cluster mass (binned over all redshift) decreases with increasing cluster mass, consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred SF seen here could produce 5-10% of the total stellar mass in massive clusters at z=0. Finally, show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming SF continues to avoid the highest density regions of the universe at z~0.75 (the avg. z of the high-z clusters). While several previous studies appear to show enhanced SF in high-redshift clusters relative to the field, note that these papers have not accounted for the overall increase in galaxy or DM density at the location of clusters. Once this is done, clusters at z~0.75 have the same or less SF per unit mass or galaxy as the field.
1304.2939
The two regimes of the cosmic sSFR evolution are due to spheroids and discs
Pipino, Calura, Matteucci
Aim to explain the two phases in the observed sSFR, namely the high (>3/Gyr) values at z>2 and the smooth decrease since z=2. In order to do this, compare to observations the sSFR evolution predicted by well calibrated models of chemical evolution for elliptical and spiral galaxies, using the additional constraints on the mean stellar ages of these galaxies (at a given mass). Conclude that the two phases of the sSFR evolution across cosmic time are due to different populations of galaxies. At z>2 the contribution comes from spheroids: the progenitors of present-day massive ellipticals (which feature the highest sSFR) as well as haloes and bulges in spirals (which contribute with average and lower-than-average sSFR). In each single galaxy the sSFR decreases rapidly and the SF stops in <1Gyr. However the combination of different generations of ellipticals in formation might result in an apparent lack of strong evolution of the sSFR (averaged over a population) at high redshift. The z<2 decrease is due to the slow evolution of the gas fraction in discs, modulated by the gas accretion history and regulated by the Schmidt law. The MW makes no exception to this behavior.
1304.2963
Observational evidence that massive cluster galaxies were forming stars at z~2.5 and did not grow in mass at later times
Andreon
As the title says. Related to subject above. Data from Spitzer and LF, MF of galaxies in five z>1.4 clusters. L* does not evolve between z=1 and 1.8. z>1.8 as the remaining epoch for the mass build up.
1304.3124
The impact of global environment of galaxy mass functions at low redshift
Calvi, Poggianti, Vulcani, Fasano
Study the galaxy stellar mass function in different environments in the local Universe, considering both the total mass function and that of individual galaxy morphological types. Compare the MF of galaxies with M*>1e10.25 in the general field and in galaxy groups, binary and single galaxy systems from Padova-Millennium Galaxy and Group Catalog at z=0.04-0.1 with the MF of galaxy clusters of the Wide Field NEarby Galaxy-Cluster Survey at z=0.04-0.07. The variations of the MF with global environment overall are small and subtle. The shapes of the MF of the general field and clusters are indistinguishable (some variation in groups). On the MF of single galaxies, representing the least massive haloes and comprising less than a third of the general field population, is proportionally richer in low-mass galaxies than other environments. The most notable environmental effect is a progressive change in the upper galaxy mass, with very massive galaxies found only in the most massive environments. This environment-dependent mass cut-off is unable to affect the Schechter parameters and the K-S test, and can only be revealed by an ad-hoc analysis. Show how in each given environment, the MF changes with morphological type, and that galaxies of the same morphological type can have different MF in different environments.
1304.3127
A new approach to identifying the most powerful gravitational lensing telescopes
Wong, Zabludoff, Ammons, Keeton, Hogg, Gonzalez
Best GL's for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the LoS. New method for finding such GL telescopes uses optical data to identify projected concentrations of LRGs. LRGs are biased tracers of the underlying mass distribution, so LoS with the highest total luminosity in LRGs are likely to contain the largest total mass. Apply this selection technique to the SDSS and identify the 200 fields with the highest total LRG luminosities projected within a 3.5' radius over 0.1<z<0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56% contain multiple known clusters previously identified in the literature. Thus, results confirm that these LRGs trace massive structures and that selection technique identifies fields with large total masses. These fields contain 2-3 times higher total LRG luminosities than most known SL clusters and will be among the best GL fields for the purpose of detetcing the highest z galaxies.
1304.3171
Exploring the interstellar media of optically compact dwarf galaxies
Most, Cannon, Salzer, Rosenberg, Engstrom, Fliss
Present 8 SF blue compact dwarf galaxies selected to be optically compact (<1 kpc optical radii), with HI spectral data, with archival SDSS and Spizter data. These systems have faint blue absolute magnitudes (M_B>=-17), ongoing SF (based on emission-line selection by the Ha or [OIII] lines), and are nearby (45 Mpc). One sample found to have an HI halo that extends 58 r-band scale lengths from its stellar body. In contrast, the rest of the sample galaxies have HI radii to optical-scale-length ratios ranging from 9.3 to 26. The size of the HI disk in the "giant disk" dwarf galaxy ADBS113845+2008 appears to be unusual as compared to similarly compact stellar populations.
1304.3174
The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the commissioning observations and the pilot surveys
Huo et al
Present 509 new quasars discovered during the 2010 and 2011 observational seasons in ~135 sq. deg, and 17 new in ~100 sq. deg. These bright quasars provide an opportunity to probe the kinematics and chemistry of the ISM/IGM in the Local Group of galaxies, providing a perfect astrometric reference frame to measure the proper motions of M31 and M33, as well as substructures of LG.
1304.3230
FIR-detected Lyman break galaxies at z~3: dust attenuation and dust correction factors at high redshift
Oteo et al
LBGs are SF galaxies in high-z; detection of LBGs in FIR provide clues on their dust attenuation and total SFR. Explore the FIR emission of a sample of 16 LBGs at z~3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100um or PACS-160um. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. Find that PACS-detected LBGs at z~3 are highly obscured galaxies which belong to the ULIRG or HLIRG class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope of their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results [SFR results?] for most of the galaxies. Comparing with a sample of PACS-detected LBGs at z~1, find evidences that the FIR emission of LBGs might have changed with redshift in the sense that the dustiest LBGs found at z~3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z~1.
1304.3335
The evolution of dusty star formation in galaxy clusters to z=1: Spitzer IR observations of the first red-sequence cluster survey
Webb,.. Yee, ... Gladders, et al
From 42 clusters of 1e14-15 Msun in 0.3<z<1.0 from RCS-1, show number of IR luminous galaxies in clusters per unit cluster mass evolves as (1+z)^(5 pm 2); these results assume a single SF galaxy template; the presence of AGN, and an evolution in their relative contribution to the MIR galaxy emission, will alter the overall number counts per cluster and their rate of evolution. Evolution of total SFR per unit cluster mass can be attributed entirely to the change in the in-falling field galaxy population. The SFR per unit cluster mass (binned over all redshift) decreases with increasing cluster mass, consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally. The inferred SF seen here could produce 5-10% of the total stellar mass in massive clusters at z=0. Finally, show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores, confirming SF continues to avoid the highest density regions of the universe at z~0.75 (the avg. z of the high-z clusters). While several previous studies appear to show enhanced SF in high-redshift clusters relative to the field, note that these papers have not accounted for the overall increase in galaxy or DM density at the location of clusters. Once this is done, clusters at z~0.75 have the same or less SF per unit mass or galaxy as the field.
Day 410
Friday.
1304.2884
Evidence for a ~300 Mpc scale Local under-density in the distribution of galaxies
Keenan, Barger, Cowie
Galaxy counts and recent measurements of the luminosity density in the NIR have indicated the possibility that the local universe may be under-dense on scales of several 100 Mpc's. The presence of a large-scale under-density in the local universe could introduce significant biases into the interpretation of the cosmological observables, and into the inferred effects of DE on the expansion rate. Measure the K-band luminosity density as a function of z to test for such a local under-density. Find that the overall shape of the z=0 rest-frame K-band luminosity function (M*= -21.6 pm 0.04 and alpha=0.99 pm 0.03) appears to be relatively constant as a function of environment and redshift out to z~0.2. Find a local (z<0.07) luminosity density that is in good agreement with previous studies. At z>0.07, detect a rising L density, and at z>0.1, it is roughly 1.5x higher than local. Suggests that the stellar mass distribution as a function of redshift follows a similar trend. Assuming that luminous matter traces the underlying DM distribution, this implies that the local mass density of the universe may be lower than the global value on a scale and amplitude sufficient to introduce significant biases into the determination of basic cosmological observables, such as the expansion rate. An under-density on this scale and amplitude, for example. would be more than sufficient to resolve the apparent tension between direct measurements of the Hubble constant and those inferred by Planck.
1304.2884
Evidence for a ~300 Mpc scale Local under-density in the distribution of galaxies
Keenan, Barger, Cowie
Galaxy counts and recent measurements of the luminosity density in the NIR have indicated the possibility that the local universe may be under-dense on scales of several 100 Mpc's. The presence of a large-scale under-density in the local universe could introduce significant biases into the interpretation of the cosmological observables, and into the inferred effects of DE on the expansion rate. Measure the K-band luminosity density as a function of z to test for such a local under-density. Find that the overall shape of the z=0 rest-frame K-band luminosity function (M*= -21.6 pm 0.04 and alpha=0.99 pm 0.03) appears to be relatively constant as a function of environment and redshift out to z~0.2. Find a local (z<0.07) luminosity density that is in good agreement with previous studies. At z>0.07, detect a rising L density, and at z>0.1, it is roughly 1.5x higher than local. Suggests that the stellar mass distribution as a function of redshift follows a similar trend. Assuming that luminous matter traces the underlying DM distribution, this implies that the local mass density of the universe may be lower than the global value on a scale and amplitude sufficient to introduce significant biases into the determination of basic cosmological observables, such as the expansion rate. An under-density on this scale and amplitude, for example. would be more than sufficient to resolve the apparent tension between direct measurements of the Hubble constant and those inferred by Planck.
Friday, April 12, 2013
Day 409
Thursday.
1304.2764
Neutron-capture element deficiency of the Hercules dwarf spheroidal galaxy
Koch et al
Study low Ba abundances in this dSph galaxy, in contrast with the high dispersions in Fe and Ca in this galaxy. The latter spreads are typical of the very low luminosity, DM-dominated dSphs, a high level of depletion in heavy elements suggests that chemical enrichment in Hercules was governed by very massive stars, coupled with a very low star formation efficiency. While very low abundances of some heavy elements are also found in individual stars of other dwarf galaxies, this is the first time that a very low Ba abundance is found within an entire dSph over a broad metallicity range.
1304.2765
Rotational signature of the Milky Way stellar halo
Fermani, Schönrich
Measure the rotation of MW stellar halo that reach out to ~50 kpc in galactocentric distance; on two samples of blue horizontal branch (BHB) field halo stars from SDSS, with 4 different methods. Find: all 4 methods agree on a weakly prograde or non-rotating halo. Further, observe no duality in the rotation of sub-samples with different metallicities or at different radii. Trace the rotation gradient across metallicity measured by Deason+ on a similar sample of BHB stars back to the inclusion of regions in the apparent magnitude-surface gravity plane [that are] known to be contaminated. In the spectroscopically selected sample of Xue+, flag ~500 hot metal-poor stars for their peculiar kinematics wrt to both their cooler metal-ppor counterparts and o the metal-rich stars in the same sample. They show a seemingly retrograde behavior in LoS velocities, which is not cofirmed by the 3d estimators. THeir anomalous vertical motion hints at either a pipeline problem or a stream-like component rather than a smooth retrograde population.
13034.2774
The simplest model of galaxy formation I: a formation history model of galaxy stellar mass growth
Mutch, Croton, Poole
Introduce a simple model to self-consistently connect the growth of galaxies to the formation history of their host DM haloes. Model defined by 2 simple functions: "baryonic growth function" which controls the rate at which new baryonic material is made available for SF, and the "physics function" which controls the efficiency with which this material is converted into stars. Using simple, phenomenologically motivated forms for both functions that depend only on a single halo property, demonstrate the model's ability to reproduce the z=0 red and blue stellar mass functions. Add redshift as a 2nd input variable to the physics function, show that the reproduction of the global stellar mass function out to z=3 is improved. Conclude by discussing the general utility of new model, highlighting its usefulness for creating mock galaxy samples which have a number of key advantages over those generated by other techniques.
1304.2776
Investigating the relationship between AGN acidity and stellar mass in zCOSMOS galaxies at 0<z<1 using emission line diagnostic diagrams
Vitale, ... Lilly, et al
Stacked spectra show AGN signatures above log (M*/M_sun) > 10.2 threshold; stellar populations of AGN hosts are found to be older with respect to SF and composite galaxies. Could be due to the tendency of AGN to reside in massive hosts. The dependence of the AGN classification on the stellar mass is in agreement with previous studies. Consistent with the downsizing scenario: an evolutionary scenario where the AGN-feedback is capable of quenching the SF in the most massive galaxies. AGN-feedback is the best candidate for initiating the passive evolutionary phase of galaxies.
1304.2785
Inflationary paradigm in trouble after Planck2013
Ijjas, Steinhardt, Loeb
Results favor models with a single scale field; while all the simplest inflation models are disfavored by the data while the surviving models (those with plateau-like potentials) are problematic. Restriction to plateau-like models leads to 3 independent problems: exacerbates both the initial conditions problem and the multiverse-unpredictability problem, and it creates a new difficulty dubbed the inflationary "unlikeliness problem". Comment on problems reconciling inflation with a standard model Higgs, as suggested by recent LHC results. Find that recent experimental data disfavors all the best-motivated inflationary scenarios and introduces new, serious difficulties that cut to the core of the inflationary paradigm. Forthcoming searches for B-modes, non Gaussianity and new particles should be decisive [?].
1304.2873
Mask effects on cosmological studies with weak lensing peak statistics
Liu, Fan
Find: high peak fractions systematically enhanced due to masks---the larger the masked area, the higher the enhancement. For 13% masked fraction, fraction of peaks with SNR > 3 is ~13, in comparison with ~9 of the mask-free case. Induces large bias on cosmological studies with WL peak statistics. For survey area of 9 deg sq, the bias is ~3sigma. Most affected peaks are close to the masked regions. Excluding peaks in those regions can reduce the bias, but at the expense of losing usable survey areas. Enhancement of high peak number can be largely attributed to higher noise led by the fewer number of galaxies usable in the reconstruction. Develop a 2-noise-level model that treats the areas close to and away from the masked regions separately. Shown that the model can account for the mask effect very well, and the parameter bias is significantly reduced. Analyze the systematic effects on peak statistics resulting from NL convergence reconstruction, including the smoothing order problem and the mass-sheet degeneracy.
1304.2764
Neutron-capture element deficiency of the Hercules dwarf spheroidal galaxy
Koch et al
Study low Ba abundances in this dSph galaxy, in contrast with the high dispersions in Fe and Ca in this galaxy. The latter spreads are typical of the very low luminosity, DM-dominated dSphs, a high level of depletion in heavy elements suggests that chemical enrichment in Hercules was governed by very massive stars, coupled with a very low star formation efficiency. While very low abundances of some heavy elements are also found in individual stars of other dwarf galaxies, this is the first time that a very low Ba abundance is found within an entire dSph over a broad metallicity range.
1304.2765
Rotational signature of the Milky Way stellar halo
Fermani, Schönrich
Measure the rotation of MW stellar halo that reach out to ~50 kpc in galactocentric distance; on two samples of blue horizontal branch (BHB) field halo stars from SDSS, with 4 different methods. Find: all 4 methods agree on a weakly prograde or non-rotating halo. Further, observe no duality in the rotation of sub-samples with different metallicities or at different radii. Trace the rotation gradient across metallicity measured by Deason+ on a similar sample of BHB stars back to the inclusion of regions in the apparent magnitude-surface gravity plane [that are] known to be contaminated. In the spectroscopically selected sample of Xue+, flag ~500 hot metal-poor stars for their peculiar kinematics wrt to both their cooler metal-ppor counterparts and o the metal-rich stars in the same sample. They show a seemingly retrograde behavior in LoS velocities, which is not cofirmed by the 3d estimators. THeir anomalous vertical motion hints at either a pipeline problem or a stream-like component rather than a smooth retrograde population.
13034.2774
The simplest model of galaxy formation I: a formation history model of galaxy stellar mass growth
Mutch, Croton, Poole
Introduce a simple model to self-consistently connect the growth of galaxies to the formation history of their host DM haloes. Model defined by 2 simple functions: "baryonic growth function" which controls the rate at which new baryonic material is made available for SF, and the "physics function" which controls the efficiency with which this material is converted into stars. Using simple, phenomenologically motivated forms for both functions that depend only on a single halo property, demonstrate the model's ability to reproduce the z=0 red and blue stellar mass functions. Add redshift as a 2nd input variable to the physics function, show that the reproduction of the global stellar mass function out to z=3 is improved. Conclude by discussing the general utility of new model, highlighting its usefulness for creating mock galaxy samples which have a number of key advantages over those generated by other techniques.
1304.2776
Investigating the relationship between AGN acidity and stellar mass in zCOSMOS galaxies at 0<z<1 using emission line diagnostic diagrams
Vitale, ... Lilly, et al
Stacked spectra show AGN signatures above log (M*/M_sun) > 10.2 threshold; stellar populations of AGN hosts are found to be older with respect to SF and composite galaxies. Could be due to the tendency of AGN to reside in massive hosts. The dependence of the AGN classification on the stellar mass is in agreement with previous studies. Consistent with the downsizing scenario: an evolutionary scenario where the AGN-feedback is capable of quenching the SF in the most massive galaxies. AGN-feedback is the best candidate for initiating the passive evolutionary phase of galaxies.
1304.2785
Inflationary paradigm in trouble after Planck2013
Ijjas, Steinhardt, Loeb
Results favor models with a single scale field; while all the simplest inflation models are disfavored by the data while the surviving models (those with plateau-like potentials) are problematic. Restriction to plateau-like models leads to 3 independent problems: exacerbates both the initial conditions problem and the multiverse-unpredictability problem, and it creates a new difficulty dubbed the inflationary "unlikeliness problem". Comment on problems reconciling inflation with a standard model Higgs, as suggested by recent LHC results. Find that recent experimental data disfavors all the best-motivated inflationary scenarios and introduces new, serious difficulties that cut to the core of the inflationary paradigm. Forthcoming searches for B-modes, non Gaussianity and new particles should be decisive [?].
1304.2873
Mask effects on cosmological studies with weak lensing peak statistics
Liu, Fan
Find: high peak fractions systematically enhanced due to masks---the larger the masked area, the higher the enhancement. For 13% masked fraction, fraction of peaks with SNR > 3 is ~13, in comparison with ~9 of the mask-free case. Induces large bias on cosmological studies with WL peak statistics. For survey area of 9 deg sq, the bias is ~3sigma. Most affected peaks are close to the masked regions. Excluding peaks in those regions can reduce the bias, but at the expense of losing usable survey areas. Enhancement of high peak number can be largely attributed to higher noise led by the fewer number of galaxies usable in the reconstruction. Develop a 2-noise-level model that treats the areas close to and away from the masked regions separately. Shown that the model can account for the mask effect very well, and the parameter bias is significantly reduced. Analyze the systematic effects on peak statistics resulting from NL convergence reconstruction, including the smoothing order problem and the mass-sheet degeneracy.
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