Books Reviewed

Ross, Rodger J.; Matthews, Glenn E.; Mertz, Pierre; Lomas, I. B. M.

doi:10.5594/j16699

Cited by 21 publications

(46 citation statements)

References 0 publications

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“…In order to estimate the covariance matrix for our w(θ) measurements we combine two different approaches: a modeling of the off-diagonal elements and the jackknife (JK) method for the variance. The jackknife technique, which has been widely applied to angular galaxy clustering measurements at small scales (e.g., Scranton et al 2002;Myers et al 2006;Ross & Brunner 2009;Coupon et al 2012) works by splitting the footprint into NJK small equal-area sections and recomputing w(θ) with each section removed. The covariance matrix between w(θ) measurements at two angular separations between two redshift bins, A and B, is estimated by,…”

Section: Covariance Matrixmentioning

confidence: 99%

Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

Crocce¹,

Carretero²,

Bauer³

et al. 2015

Mon. Not. R. Astron. Soc.

103

171

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We study the clustering of galaxies detected at i < 22.5 in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using 2.3 × 10 6 galaxies over a contiguous 116 deg 2 region in five bins of photometric redshift width ∆z = 0.2 in the range 0.2 < z < 1.2. The impact of photometric redshift errors are assessed by comparing results using a template-based photo-z algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper (Leistedt et al 2015) presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck ΛCDM model, finding agreement with CFHTLS measurements with χ 2 of 4.0 (8.7) with 5 degrees of freedom for the TPZ (BPZ) redshifts. We test a "linear bias" model, in which the galaxy clustering is a fixed multiple of the predicted non-linear dark-matter clustering. The precision of the data allow us to determine that the linear bias model describes the observed galaxy clustering to 2.5% accuracy down to scales at least 4 to 10 times smaller than those on which linear theory is expected to be sufficient.

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Section: Covariance Matrixmentioning

confidence: 99%

Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

Crocce¹,

Carretero²,

Bauer³

et al. 2015

Mon. Not. R. Astron. Soc.

103

171

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“…Kravtsov et al 2004;Conroy et al 2006;Cooray 2006) allow one to easily model halo abundance and galaxy populations in haloes in terms of centrals and satellites (e.g. Zehavi et al 2005;Zheng et al 2007;Ross & Brunner 2009;Skibba et al 2009;Wake et al 2011). This type of analysis is powerful and versatile, yielding for example measurements of quenched fractions as a function of redshift and luminosity (Tinker et al 2010) or merger rates as a function of redshift (e.g.…”

Section: Introductionmentioning

confidence: 99%

Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

Tojeiro

Eardley

Peacock

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present evidence for halo assembly bias as a function of geometric environment. By classifying GAMA galaxy groups as residing in voids, sheets, filaments or knots using a tidal tensor method, we find that low-mass haloes that reside in knots are older than haloes of the same mass that reside in voids. This result provides direct support to theories that link strong halo tidal interactions with halo assembly times. The trend with geometric environment is reversed at large halo mass, with haloes in knots being younger than haloes of the same mass in voids. We find a clear signal of halo downsizing -more massive haloes host galaxies that assembled their stars earlier. This overall trend holds independently of geometric environment. We support our analysis with an in-depth exploration of the L-Galaxies semi-analytic model, used here to correlate several galaxy properties with three different definitions of halo formation time. We find a complex relationship between halo formation time and galaxy properties, with significant scatter. We confirm that stellar mass to halo mass ratio, specific star-formation rate and mass-weighed age are reasonable proxies of halo formation time, especially at low halo masses. Instantaneous star-formation rate is a poor indicator at all halo masses. Using the same semi-analytic model, we create mock spectral observations using complex star-formation and chemical enrichment histories, that approximately mimic GAMA's typical signal-to-noise and wavelength range. We use these mocks to assert how well potential proxies of halo formation time may be recovered from GAMA-like spectroscopic data.

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“…This strategy has been utilized to explore the formation and evolution of galaxies (see e.g. Blake, Collister & Lahav 2008;McCracken et al 2008;Ross & Brunner 2009;Ross, Percival & Brunner 2010;Ross, Tojeiro & Percival 2011a;Wake et al 2011) and quasars (e.g. Myers et al 2006), and also to measure cosmological parameters (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Ameliorating systematic uncertainties in the angular clustering of galaxies: a study using the SDSS-III

Ross

Cuesta

et al. 2011

Monthly Notices of the Royal Astronomical Society

190

279

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We investigate the effects of potential sources of systematic error on the angular and photometric redshift, zphot, distributions of a sample of redshift 0.4 < z < 0.7 massive galaxies whose selection matches that of the Baryon Oscillation Spectroscopic Survey (BOSS) constant‐mass sample. Utilizing over 112 778 BOSS spectra as a training sample, we produce a photometric redshift catalogue for the galaxies in the Sloan Digital Sky Survey eight data release imaging area that, after masking, covers nearly one quarter of the sky (9913 deg2). We investigate fluctuations in the number density of objects in this sample as a function of Galactic extinction, seeing, stellar density, sky background, airmass, photometric offset and North/South Galactic hemisphere. We find that the presence of stars of comparable magnitudes to our galaxies (which are not traditionally masked) effectively removes area. Failing to correct for such stars can produce systematic errors on the measured angular autocorrelation function, w(θ), that are larger than its statistical uncertainty. We describe how one can effectively mask for the presence of the stars, without removing any galaxies from the sample, and minimize the systematic error. Additionally, we apply two separate methods that can be used to correct for the systematic errors imparted by any parameter that can be turned into a map on the sky. We find that failing to properly account for varying sky background introduces a systematic error on w(θ). We measure w(θ), in four zphot slices of width 0.05 between 0.45 < zphot < 0.65, and find that the measurements, after correcting for the systematic effects of stars and sky background, are generally consistent with a generic Λ cold dark matter model, at scales up to 60°. At scales greater than 3° and zphot > 0.5, the magnitude of the corrections we apply is greater than the statistical uncertainty in w(θ). The photometric redshift catalogue we produce will be made publicly available at http://portal.nersc.gov/project/boss/galaxy/photoz/.

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Books Reviewed

Cited by 21 publications

References 0 publications

Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data

Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

Ameliorating systematic uncertainties in the angular clustering of galaxies: a study using the SDSS-III

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