arXiv subjects

Ashley Ross

Publications and source records attributed to Ashley Ross.

24 records · Page 2Linked to original sources

arXiv2016

The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: mock galaxy catalogues for the BOSS Final Data Release

We reproduce the galaxy clustering catalogue from the SDSS-III Baryon Oscillation Spectroscopic Survey Final Data Release (BOSS DR11&DR12) with high fidelity on all relevant scales in order to allow a robust analysis of baryon acoustic oscillations and redshift space distortions. We have generated (6,000) 12,288 MultiDark PATCHY BOSS (DR11) DR12 light-cones corresponding to an effective volume of $\sim192,000\,[h^{-1}\,{\rm Gpc}]^3$ (the largest ever simulated volume), including cosmic evolution in the redshift range from 0.15 to 0.75. The mocks have been calibrated using a reference galaxy catalogue based on the halo abundance matching modelling of the BOSS DR11&DR12 galaxy clustering data and on the data themselves. The production follows three steps. First, we apply the PATCHY code to generate a dark matter field and an object distribution including nonlinear stochastic galaxy bias. Secondly, we run the halo/stellar distribution reconstruction HADRON code to assign masses to the various objects. This step uses the mass distribution as a function of local density and non-local indicators (i.e., tidal field tensor eigenvalues and relative halo exclusion separation for massive objects) from the reference simulation applied to the corresponding PATCHY dark matter and galaxy distribution. Finally, we apply the SUGAR code to build the light cones. The resulting MultiDark PATCHY mock light cones reproduce the number density, selection function, survey geometry, and in general within 1 $σ$, for arbitrary stellar mass bins, the power spectrum up to $k=0.3\,h\,{\rm Mpc}^{-1}$, the two-point correlation functions down to a few Mpc scales, and the three-point statistics of the BOSS DR11&DR12 galaxy samples.

astro-ph.CO↗

arXiv2015

Sloan Digital Sky Survey III Photometric Quasar Clustering: Probing the Initial Conditions of the Universe using the Largest Volume

The Sloan Digital Sky Survey has surveyed 14,555 square degrees of the sky, and delivered over a trillion pixels of imaging data. We present the large-scale clustering of 1.6 million quasars between z = 0.5 and z = 2.5 that have been classified from this imaging, representing the highest density of quasars ever studied for clustering measurements. This data set spans ~11,000 square degrees and probes a volume of 80(Gpc/h)^3. In principle, such a large volume and medium density of tracers should facilitate high-precision cosmological constraints. We measure the angular clustering of photometrically classified quasars using an optimal quadratic estimator in four redshift slices with an accuracy of ~25% over a bin width of l ~10 - 15 on scales corresponding to matter-radiation equality and larger (l ~ 2 - 30). Observational systematics can strongly bias clustering measurements on large scales, which can mimic cosmologically relevant signals such as deviations from Gaussianity in the spectrum of primordial perturbations. We account for systematics by employing a new method recently proposed by Agarwal et al. (2014) to the clustering of photometrically classified quasars. We carefully apply our methodology to mitigate known observational systematics and further remove angular bins that are contaminated by unknown systematics. Combining quasar data with the photometric luminous red galaxy (LRG) sample of Ross et al. (2011) and Ho et al. (2012), and marginalizing over all bias and shot noise-like parameters, we obtain a constraint on local primordial non-Gaussianity of fNL = -113+/-154 (1σerror). [Abridged]

astro-ph.CO↗

arXiv2014

The SDSS-III Baryonic Oscillation Spectroscopic Survey: Constraints on the Integrated Sachs Wolfe effect

In the context of the study of the Integrated Sachs Wolfe effect (ISW), we construct a template of the projected density distribution up to $z\simeq 0.7$ by using the Luminous Galaxies (LGs) from the Sloan Digital Sky Survey DR8. We use a photo-z catalogue trained with more than a hundred thousand galaxies from BOSS in the SDSS DR8 imaging area. We consider two different LG samples whose selection matches that of SDSS-III/BOSS: the LOWZ sample ($z\in [0.15,0.5]$) and the CMASS sample ($z\in[0.4,0.7]$). When building the LG density maps we use the information from star density, survey footprint, seeing conditions, sky emission, dust extinction and airmass to explore the impact of these artifacts on the two LG samples. In agreement with previous studies, we find that the CMASS sample is particularly sensitive to Galactic stars, which dominate the contribution to the auto-angular power spectrum below $\ell=7$. Other potential systematics affect mostly the low multipole range ($\ell\in[2,7]$), but leave fluctuations on smaller scales practically unchanged. The resulting power spectra in the multipole range $\ell\in[2,100]$ for the LOWZ, CMASS and LOWZ+CMASS samples are compatible with linear $Λ$CDM expectations and constant bias values of $b=1.98 \pm 0.11$, $2.08\pm0.14$ and $1.88\pm 0.11$, respectively, with no traces of non-Gaussianity: $f_{\rm NL}^{\rm local}=59\pm 75$ at 95% confidence level for the full LOWZ+CMASS sample in the range $\ell\in[4,100]$. After cross-correlating WMAP-9yr data with the LOWZ+CMASS LG density field, the ISW signal is detected at the level of 1.62--1.69$\,σ$. While this result is in close agreement with predictions from Monte Carlo simulations in the concordance $Λ$CDM model, it cannot rule out by itself an Einstein-de Sitter scenario, and has a moderately low signal compared to previous studies conducted on subsets of this LG sample.

astro-ph.CO↗

arXiv2012

Acoustic scale from the angular power spectra of SDSS-III DR8 photometric luminous galaxies

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 ~ 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.

astro-ph.CO↗

arXiv2012

New Neutrino Mass Bounds from Sloan Digital Sky Survey III Data Release 8 Photometric Luminous Galaxies

We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release Eight (SDSS DR8). The galaxies have photometric redshifts between $z = 0.45$ and $z = 0.65$, and cover 10,000 square degrees and thus probe a volume of 3$h^{-3}$Gpc$^3$, enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses $\sum m_ν< 0.26$ eV, at 95% confidence level (CL), is obtained after combining our sample of galaxies, which we call "CMASS", with WMAP 7 year Cosmic Microwave Background (CMB) data and the most recent measurement of the Hubble parameter from the Hubble Space Telescope (HST). This constraint is obtained with a conservative multipole range choice of $30 < \ell < 200$ in order to minimize non-linearities, and a free bias parameter in each of the four redshift bins. We study the impact of assuming this linear galaxy bias model using mock catalogs, and find that this model causes a small ($\sim 1-1.5 σ$) bias in $Ω_{\rm DM} h^2$. For this reason, we also quote neutrino bounds based on a conservative galaxy bias model containing additional, shot noise-like free parameters. In this conservative case, the bounds are significantly weakened, e.g. $\sum m_ν< 0.36$ eV (95% confidence level) for WMAP+HST+CMASS ($\ell_{\rm max}=200$). We also study the dependence of the neutrino bound on multipole range ($\ell_{\rm max}=150$ vs $\ell_{\rm max}=200$) and on which combination of data sets is included as a prior. The addition of supernova and/or Baryon Acoustic Oscillation data does not significantly improve the neutrino mass bound once the HST prior is included. [abridged]

astro-ph.CO↗

arXiv2011

The SDSS DR7 Galaxy Angular Power Spectrum

We calculate the angular power spectrum of galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) by using a quadratic estimation method with KL-compression. The primary data sample includes over 18 million galaxies covering more than 5,700 square degrees after masking areas with bright objects, reddening greater than 0.2 magnitudes, and seeing of more than 1.5 arcseconds. We test for systematic effects by calculating the angular power spectrum by SDSS stripe and find that these measurements are minimally affected by seeing and reddening. We calculate the angular power spectrum for l \leq 200 multipoles by using 40 bandpowers for the full sample, and l \leq 1000 multipoles using 50 bandpowers for individual stripes. We also calculate the angular power spectrum for this sample separated into 3 magnitude bins with mean redshifts of z = 0.171, z = 0.217, and z = 0.261 to examine the evolution of the angular power spectrum. We determine the theoretical linear angular power spectrum by projecting the 3D power spectrum to two dimensions for a basic comparison to our observational results. By minimizing the χ^2 fit between these data and the theoretical linear angular power spectrum we measure a loosely-constrained fit of Ω_m = 0.31^{+0.18}_{-0.11} with a linear bias of b = 0.94 \pm 0.04.

astro-ph.CO↗