126 research outputs found
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: RSD measurement from the power spectrum and bispectrum of the DR12 BOSS galaxies
We measure and analyse the bispectrum of the final, Data Release 12, galaxy
sample provided by the Baryon Oscillation Spectroscopic Survey, splitting by
selection algorithm into LOWZ and CMASS galaxies. The LOWZ sample contains
361\,762 galaxies with an effective redshift of , and the
CMASS sample 777\,202 galaxies with an effective redshift of . Combining the power spectrum, measured relative to the
line-of-sight, with the spherically averaged bispectrum, we are able to
constrain the product of the growth of structure parameter, , and the
amplitude of dark matter density fluctuations, , along with the
geometric Alcock-Paczynski parameters, the product of the Hubble constant and
the comoving sound horizon at the baryon drag epoch, , and the
angular distance parameter divided by the sound horizon, .
After combining pre-reconstruction RSD analyses of the power spectrum monopole,
quadrupole and bispectrum monopole; with post-reconstruction analysis of the
BAO power spectrum monopole and quadrupole, we find , , for
the LOWZ sample, and ,
, for the CMASS sample. We
find general agreement with previous BOSS DR11 and DR12 measurements. Combining
our dataset with {\it Planck15} we perform a null test of General Relativity
(GR) through the -parametrisation finding
, which is away from the GR
predictions.Comment: 34 pages, 22 figures, 8 tables. Accepted for publication in MNRAS.
Data available at https://sdss3.org//science/boss_publications.ph
The correlation between halo mass and stellar mass for the most massive galaxies in the universe
I.Z. is supported by NSF grant AST-1612085. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah.We present measurements of the clustering of galaxies as a function of their stellar mass in the Baryon Oscillation Spectroscopic Survey. We compare the clustering of samples using 12 different methods for estimating stellar mass, isolating the method that has the smallest scatter at fixed halo mass. In this test, the stellar mass estimate with the smallest errors yields the highest amplitude of clustering at fixed number density. We find that the PCA stellar masses of Chen et al. clearly have the tightest correlation with halo mass. The PCA masses use the full galaxy spectrum, differentiating them from other estimates that only use optical photometric information. Using the PCA masses, we measure the large-scale bias as a function of M∗ for galaxies with log M∗ ≥ 11.4, correcting for incompleteness at the low-mass end of our measurements. Using the abundance matching ansatz to connect dark matter halo mass to stellar mass, we construct theoretical models of b (M∗) that match the same stellar mass function but have different amounts of scatter in stellar mass at fixed halo mass, σlog M∗. Using this approach, we find σlogM∗ = 0.18 -0.02 +0.01. This value includes both intrinsic scatter as well as random errors in the stellar masses. To partially remove the latter, we use repeated spectra to estimate statistical errors on the stellar masses, yielding an upper limit to the intrinsic scatter of 0.16 dex.Publisher PDFPeer reviewe
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Angular clustering tomography and its cosmological implications
We investigate the cosmological implications of studying galaxy clustering
using a tomographic approach applied to the final BOSS DR12 galaxy sample,
including both auto- and cross-correlation functions between redshift shells.
We model the signal of the full shape of the angular correlation function,
, in redshift bins using state-of-the-art modelling of
non-linearities, bias and redshift-space distortions. We present results on the
redshift evolution of the linear bias of BOSS galaxies, which cannot be
obtained with traditional methods for galaxy-clustering analysis. We also
obtain constraints on cosmological parameters, combining this tomographic
analysis with measurements of the cosmic microwave background (CMB) and type Ia
supernova (SNIa). We explore a number of cosmological models, including the
standard CDM model and its most interesting extensions, such as
deviations from w_\rm{DE} = -1, non-minimal neutrino masses, spatial
curvature and deviations from general relativity using the growth-index
parametrisation. These results are, in general, comparable to the most
precise present-day constraints on cosmological parameters, and show very good
agreement with the standard model. In particular, combining CMB,
and SNIa, we find a value of w_\rm{DE} consistent with
to a precision better than 5\% when it is assumed to be constant in time, and
better than 6\% when we also allow for a spatially-curved Universe.Comment: 21 pages, 18 figures, accepted for publication MNRAS. The data used
in this analysis is publicly available at
https://sdss3.org/science/boss_publications.ph
Properties of Type Ia supernovae inside rich galaxy clusters
We used the Gaussian Mixture Brightest Cluster Galaxy catalogue and Sloan Digital Sky
Survey-II supernovae data with redshifts measured by the Baryon Oscillation Spectroscopic
Survey to identify 48 Type Ia supernovae (SNe Ia) residing in rich galaxy clusters and compare
their properties with 1015 SNe Ia in the field. Their light curves were parametrized by the
SALT2 model and the significance of the observed differences was assessed by a resampling
technique. To test our samples and methods, we first looked for known differences between
SNe Ia residing in active and passive galaxies. We confirm that passive galaxies host SNe
Ia with smaller stretch, weaker colour–luminosity relation [β of 2.54(22) against 3.35(14)],
and that are ∼0.1 mag more luminous after stretch and colour corrections. We show that
only 0.02 per cent of random samples drawn from our set of SNe Ia in active galaxies can
reach these values. Reported differences in the Hubble residuals scatter could not be detected,
possibly due to the exclusion of outliers. We then show that, while most field and cluster
SNe Ia properties are compatible at the current level, their stretch distributions are different
(∼3σ): besides having a higher concentration of passive galaxies than the field, the cluster’s
passive galaxies host SNe Ia with an average stretch even smaller than those in field passive
galaxies (at 95 per cent confidence).We argue that the older age of passive galaxies in clusters
is responsible for this effect since, as we show, old passive galaxies host SNe Ia with smaller
stretch than young passive galaxies (∼4σ).Web of Scienc
Baryon Acoustic Oscillations in the Ly{\alpha} forest of BOSS DR11 quasars
We report a detection of the baryon acoustic oscillation (BAO) feature in the
flux-correlation function of the Ly{\alpha} forest of high-redshift quasars
with a statistical significance of five standard deviations. The study uses
137,562 quasars in the redshift range from the Data Release
11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III.
This sample contains three times the number of quasars used in previous
studies. The measured position of the BAO peak determines the angular distance,
and expansion rate, , both on a scale set by the sound
horizon at the drag epoch, . We find
and
where . The optimal
combination, is determined with a precision of
. For the value , consistent with the CMB power
spectrum measured by Planck, we find
and . Tests with mock
catalogs and variations of our analysis procedure have revealed no systematic
uncertainties comparable to our statistical errors. Our results agree with the
previously reported BAO measurement at the same redshift using the
quasar-Ly{\alpha} forest cross-correlation. The auto-correlation and
cross-correlation approaches are complementary because of the quite different
impact of redshift-space distortion on the two measurements. The combined
constraints from the two correlation functions imply values of and
that are, respectively, 7% low and 7% high compared to the
predictions of a flat CDM cosmological model with the best-fit Planck
parameters. With our estimated statistical errors, the significance of this
discrepancy is .Comment: Accepted for publication in A&A. 17 pages, 18 figure
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements from CMASS anisotropic galaxy clustering
With the largest spectroscopic galaxy survey volume drawn from the SDSS-III
Baryon Oscillation Spectroscopic Survey (BOSS), we can extract cosmological
constraints from the measurements of redshift and geometric distortions at
quasi-linear scales (e.g. above 50 Mpc). We analyze the broad-range
shape of the monopole and quadrupole correlation functions of the BOSS Data
Release 12 (DR12) CMASS galaxy sample, at the effective redshift , to
obtain constraints on the Hubble expansion rate , the angular-diameter
distance , the normalized growth rate , and the
physical matter density . We obtain robust measurements by
including a polynomial as the model for the systematic errors, and find it
works very well against the systematic effects, e.g., ones induced by stars and
seeing. We provide accurate measurements ,
, , = , , , ,
where is the comoving sound horizon at the drag epoch and
Mpc is the sound scale of the fiducial cosmology used in
this study. The parameters which are not well constrained by our galaxy
clustering analysis are marginalized over with wide flat priors. Since no
priors from other data sets, e.g., cosmic microwave background (CMB), are
adopted and no dark energy models are assumed, our results from BOSS CMASS
galaxy clustering alone may be combined with other data sets, i.e., CMB, SNe,
lensing or other galaxy clustering data to constrain the parameters of a given
cosmological model. The uncertainty on the dark energy equation of state
parameter, , from CMB+CMASS is about 8 per cent. The uncertainty on the
curvature fraction, , is 0.3 per cent. We do not find deviation from
flat CDM.Comment: 15 pages, 11 figures. The latest version matches and the accepted
version by MNRAS. A bug in the first version has been identified and fixed in
the new version. We have redone the analysis with newest data (BOSS DR12
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : measuring DA and H at z = 0.57 from the baryon acoustic peak in the Data Release 9 spectroscopic Galaxy sample
We present measurements of the angular diameter distance to and Hubble parameter at z = 0.57 from the measurement of the baryon acoustic peak in the correlation of galaxies from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. Our analysis is based on a sample from Data Release 9 of 264 283 galaxies over 3275 square degrees in the redshift range 0.43 < z < 0.70. We use two different methods to provide robust measurement of the acoustic peak position across and along the line of sight in order to measure the cosmological distance scale. We find DA(0.57) = 1408 ± 45 Mpc and H(0.57) = 92.9 ± 7.8 km s−1 Mpc−1 for our fiducial value of the sound horizon. These results from the anisotropic fitting are fully consistent with the analysis of the spherically averaged acoustic peak position presented in Anderson et al. Our distance measurements are a close match to the predictions of the standard cosmological model featuring a cosmological constant and zero spatial curvature.Publisher PDFPeer reviewe
SDSS-III Baryon Oscillation Spectroscopic Survey data release 12 : galaxy target selection and large-scale structure catalogues
The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets for which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large-scale structure catalogues for the final Data Release (DR12) samples and the associated random catalogues that quantify the survey mask. The algorithms are an evolution of those used by the BOSS team to construct catalogues from earlier data, and have been designed to accurately quantify the galaxy sample. The code used, designated mksample, is released with this paper.Publisher PDFPeer reviewe
Type Ia Supernova Properties as a Function of the Distance to the Host Galaxy in the SDSS-II SN Survey
We use type-Ia supernovae (SNe Ia) discovered by the SDSS-II SN Survey to
search for dependencies between SN Ia properties and the projected distance to
the host galaxy center, using the distance as a proxy for local galaxy
properties (local star-formation rate, local metallicity, etc.). The sample
consists of almost 200 spectroscopically or photometrically confirmed SNe Ia at
redshifts below 0.25. The sample is split into two groups depending on the
morphology of the host galaxy. We fit light-curves using both MLCS2k2 and
SALT2, and determine color (AV, c) and light-curve shape (delta, x1) parameters
for each SN Ia, as well as its residual in the Hubble diagram. We then
correlate these parameters with both the physical and the normalized distances
to the center of the host galaxy and look for trends in the mean values and
scatters of these parameters with increasing distance. The most significant (at
the 4-sigma level) finding is that the average fitted AV from MLCS2k2 and c
from SALT2 decrease with the projected distance for SNe Ia in spiral galaxies.
We also find indications that SNe in elliptical galaxies tend to have narrower
light-curves if they explode at larger distances, although this may be due to
selection effects in our sample. We do not find strong correlations between the
residuals of the distance moduli with respect to the Hubble flow and the
galactocentric distances, which indicates a limited correlation between SN
magnitudes after standardization and local host metallicity.Comment: Accepted for publication in The Astrophysical Journal (33 pages, 5
figures, 8 tables
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