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Register a new userThe clustering of LRGs in the DECaLS DR8 footprint: distance constraints from baryon acoustic oscillations using photometric redshifts
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A photometric redshift sample of Luminous Red Galaxies (hereafter LRGs) obtained from The DECam Legacy Survey (DECaLS) is analysed to probe cosmic distances by exploiting the wedge approach of the two-point correlation function. Although the cosmological information is highly contaminated by the uncertainties existing in the photometric redshifts from the galaxy map, an angular diameter distance can be probed at the perpendicular configuration in which the measured correlation function is minimally contaminated. An ensemble of wedged correlation functions selected up to a given threshold based on having the least contamination was studied in the previous work (arXiv:1903.09651v2 [astro-ph.CO]) using simulations, and the extracted cosmological information was unbiased within this threshold. We apply the same methodology for analysing the LRG sample from DECaLS which will provide the optical imaging for targeting two-thirds of the DESI footprint and measure the angular diameter distances at $z=0.69$ and $z=0.87$ to be $D_{A}(0.697)=(1499 pm 77,mathrm{Mpc})(r_{d}/r_{d,fid})$ and $D_{A}(0.874)=(1680 pm 109,mathrm{Mpc})(r_{d}/r_{d,fid})$ with a fractional error of 5.14% and 6.48% respectively. We obtain a value of $H_{0}=67.59pm5.52$ km/s/Mpc which supports the $H_0$ measured by all other BAO results and is consistent with $Lambda$CDM model.
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A new determination of the sound horizon scale in angular coordinates is presented. It makes use of ~ 0.6 x 10^6 Luminous Red Galaxies, selected from the Sloan Digital Sky Survey imaging data, with photometric redshifts. The analysis covers a redshift interval that goes from z=0.5 to z=0.6. We find evidence of the Baryon Acoustic Oscillations (BAO) signal at the ~ 2.3 sigma confidence level, with a value of theta_{BAO} (z=0.55) = (3.90 pm 0.38) degrees, including systematic errors. To our understanding, this is the first direct measurement of the angular BAO scale in the galaxy distribution, and it is in agreement with previous BAO measurements. We also show how radial determinations of the BAO scale can break the degeneracy in the measurement of cosmological parameters when they are combined with BAO angular measurements. The result is also in good agreement with the WMAP7 best-fit cosmology. We obtain a value of w_0 = -1.03 pm 0.16 for the equation of state parameter of the dark energy, Omega_M = 0.26 pm 0.04 for the matter density, when the other parameters are fixed. We have also tested the sensitivity of current BAO measurements to a time varying dark energy equation of state, finding w_a = 0.06 pm 0.22 if we fix all the other parameters to the WMAP7 best-fit cosmology.
We analyse the largest spectroscopic samples of galaxy clusters to date, and provide observational constraints on the distance-redshift relation from baryon acoustic oscillations. The cluster samples considered in this work have been extracted from the Sloan Digital Sky Survey at three median redshifts, $z=0.2$, $z=0.3$, and $z=0.5$. The number of objects is $12910$, $42215$, and $11816$, respectively. We detect the peak of baryon acoustic oscillations for all the three samples. The derived distance constraints are: $r_s/D_V(z=0.2)=0.18 pm 0.01$, $r_s/D_V(z=0.3)=0.124 pm 0.004$ and $r_s/D_V(z=0.5)=0.080 pm 0.002$. Combining these measurements, we obtain robust constraints on cosmological parameters. Our results are in agreement with the standard $Lambda$ cold dark matter model. Specifically, we constrain the Hubble constant in a $Lambda$CDM model, $H_0 = 64_{-9}^{+14} , mathrm{km} , mathrm{s}^{-1}mathrm{Mpc}^{-1}$, the density of curvature energy, in the $oLambda$CDM context, $Omega_K = -0.015_{-0.36}^{+0.34}$, and finally the parameter of the dark energy equation of state in the $ow$CDM case, $w = -1.01_{-0.44}^{+0.44}$. This is the first time the distance-redshift relation has been constrained using only the peak of baryon acoustic oscillations of galaxy clusters.
Baryon Acoustic Oscillations (BAO) are frozen relics left over from the pre-decoupling universe. They are the standard rulers of choice for 21st century cosmology, providing distance estimates that are, for the first time, firmly rooted in well-understood, linear physics. This review synthesises current understanding regarding all aspects of BAO cosmology, from the theoretical and statistical to the observational, and includes a map of the future landscape of BAO surveys, both spectroscopic and photometric.
We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872,921 galaxies over ~ 10,000 deg^2 between 0.45<z<0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey (BOSS) luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, Ho et al. 2011, to derive the location of Baryon acoustic oscillations (BAO) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D_A/r_s= 9.212 + 0.416 -0.404 at z=0.54, and therefore, D_A= 1411+- 65 Mpc at z=0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D_A is 1.4 sigma higher than what is expected for the concordance LCDM (Komatsu et al. 2011), in accordance to the trend of other spectroscopic BAO measurements for z >~ 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS (Percival et al. 2010) and WiggleZ (Blake et al. 2011). We refer to our companion papers (Ho et al. 2011; de Putter et al. 2011) for investigations on information of the full power spectrum.
We use the DECaLS DR3 survey photometry matched to the SDSS-III/BOSS DR12 spectroscopic catalog to investigate the morphology and stellar mass-size relation of luminous red galaxies (LRGs) within the CMASS and LOWZ galaxy samples in the redshift range $0.2<z<0.7$. The large majority of both samples is composed of early-type galaxies with De Vaucouleurs profiles, while only less than 20% are late-type exponentials. We calibrate DECaLS effective radii using the higher resolution CFHT/MegaCam observations and optimise the correction for each morphological type. By cross-matching the photometric properties of the early-type population with the Portsmouth stellar mass catalog, we are able to explore the high-mass end of the distribution using a large sample of 313,026 galaxies over 4380 deg$^{2}$. We find a clear correlation between the sizes and the stellar masses of these galaxies, which appears flatter than previous estimates at lower masses. The sizes of these early-type galaxies do not exhibit significant evolution within the BOSS redshift range, but a slightly declining redshift trend is found when these results are combined with $zsim0.1$ SDSS measurements at the high-mass end. The synergy between BOSS and DECaLS has important applications in other fields, including galaxy clustering and weak lensing.
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