Publications

2014
Tojeiro R, Ross AJ, Burden A, Samushia L, Manera M, Percival WJ, Beutler F, Cuesta AJ, Dawson K, Eisenstein DJ, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: galaxy clustering measurements in the low redshift sample of Data Release 11. ArXiv e-prints [Internet]. 2014;1401:1768. Publisher's VersionAbstract
We present the distance measurement to z = 0.32 using the 11th datarelease of the Sloan Digital Sky Survey-III Baryon Acoustic OscillationSurvey (BOSS). We use 313,780 galaxies of the low-redshift (LOWZ) sampleover 7,341 square-degrees to compute $D_V = (1264 \pm
Guo H, Zheng Z, Zehavi I, Xu H, Eisenstein DJ, Weinberg DH, Bahcall NA, Berlind AA, Comparat J, McBride CK, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: modeling of the luminosity and colour dependence in the Data Release 10. ArXiv e-prints [Internet]. 2014;1401:3009. Publisher's VersionAbstract
We investigate the luminosity and colour dependence of clustering ofCMASS galaxies in the Sloan Digital Sky Survey-III Baryon OscillationSpectroscopic Survey Tenth Data Release. The halo occupationdistribution framework is adopted to model the projected two-pointcorrelation function measurements on small and intermediate scales (from$0.02$ to $60\,h^{-1}{\rm {Mpc}}$) and to interpret the observed trendsand infer the connection of galaxies to dark matter halos. We find thatluminous red galaxies reside in massive halos of mass$M{\sim}10^{13}$--$10^{14}\,h^{-1}{\rm M_\odot}$ and more luminousgalaxies are more clustered and hosted by more massive halos. The strongsmall-scale clustering requires a fraction of these galaxies to besatellites in massive halos, with the fraction at the level of 5--8 percent and decreasing with luminosity. The characteristic mass of a halohosting on average one satellite galaxy above a luminosity threshold isabout a factor $8.7$ larger than that of a halo hosting a central galaxyabove the same threshold. At a fixed luminosity, progressively reddergalaxies are more strongly clustered on small scales, which can beexplained by having a larger fraction of these galaxies in the form ofsatellites in massive halos. Our clustering measurements on scales below$0.4\,h^{-1}{\rm {Mpc}}$ allow us to study the small-scale spatialdistribution of satellites inside halos. While the clustering ofluminosity-threshold samples can be well described by aNavarro-Frenk-White (NFW) profile, that of the reddest galaxies prefersa steeper or more concentrated profile. Finally, we also use galaxysamples of constant number density at different redshifts to study theevolution of luminous galaxies, and find the clustering to be consistentwith passive evolution in the redshift range of $0.5 \lesssim z \lesssim0.6$.
Anderson L, Aubourg E, Bailey S, Beutler F, Bolton AS, Brinkmann J, Brownstein JR, Chuang C-H, Cuesta AJ, Dawson KS, et al. 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. Monthly Notices of the Royal Astronomical Society [Internet]. 2014:156. Publisher's VersionAbstract
We present measurements of the angular diameter distance to and Hubbleparameter at z = 0.57 from the measurement of the baryon acoustic peakin the correlation of galaxies from the Sloan Digital Sky Survey IIIBaryon Oscillation Spectroscopic Survey. Our analysis is based on asample from Data Release 9 of 264 283 galaxies over 3275 square degreesin the redshift range 0.43 < z < 0.70. We use two differentmethods to provide robust measurement of the acoustic peak positionacross and along the line of sight in order to measure the cosmologicaldistance scale. We find DA(0.57) = 1408 ± 45 Mpc andH(0.57) = 92.9 ± 7.8 km s-1 Mpc-1 for ourfiducial value of the sound horizon. These results from the anisotropicfitting are fully consistent with the analysis of the sphericallyaveraged acoustic peak position presented in Anderson et al. Ourdistance measurements are a close match to the predictions of thestandard cosmological model featuring a cosmological constant and zerospatial curvature.
Ross AJ, Samushia L, Burden A, Percival WJ, Tojeiro R, Manera M, Beutler F, Brinkmann J, Brownstein JR, Carnero A, et al. The clustering of galaxies in the SDSS-III DR10 Baryon Oscillation Spectroscopic Survey: no detectable colour dependence of distance scale or growth rate measurements. Monthly Notices of the Royal Astronomical Society [Internet]. 2014;437:1109-1126. Publisher's VersionAbstract
We study the clustering of galaxies, as a function of their colour, fromData Release Ten (DR10) of the Sloan Digital Sky Survey III (SDSS-III)Baryon Oscillation Spectroscopic Survey. DR10 contains 540 505 galaxieswith 0.43 < z < 0.7; from these we select 122 967 for a `Blue'sample and 131 969 for a `Red' sample based on k + e corrected (to z =0.55) r - i colours and i-band magnitudes. The samples are chosen suchthat both contain more than 100 000 galaxies, have similar redshiftdistributions and maximize the difference in clustering amplitude. TheRed sample has a 40 per cent larger bias than the Blue(bRed/bBlue = 1.39 ± 0.04), implying thatthe Red galaxies occupy dark matter haloes with an average mass that is0.5 log10 M⊙ greater. Spherically averagedmeasurements of the correlation function, ξ0, and thepower spectrum are used to locate the position of the baryon acousticoscillation (BAO) feature of both samples. Using ξ0, weobtain distance scales, relative to the distance of our referenceΛ cold dark matter cosmology, of 1.010 ± 0.027 for the Redsample and 1.005 ± 0.031 for the Blue. After applyingreconstruction, these measurements improve to 1.013 ± 0.020 forthe Red sample and 1.008 ± 0.026 for the Blue. For each sample,measurements of ξ0 and the second multipole moment,ξ2, of the anisotropic correlation function are used todetermine the rate of structure growth, parametrized byfσ8. We find fσ8, Red = 0.511 ±0.083, fσ8, Blue = 0.509 ± 0.085 andfσ8, Cross = 0.423 ± 0.061 (from thecross-correlation between the Red and Blue samples). We use thecovariance between the bias and growth measurements obtained from eachsample and their cross-correlation to produce an optimally combinedmeasurement of fσ8, comb = 0.443 ± 0.055. Thisresult compares favourably to that of the full 0.43 < z < 0.7sample (fσ8, full = 0.422 ± 0.051) despite thefact that, in total, we use less than half of the number of galaxiesanalysed in the full sample measurement. In no instance do we detectsignificant differences in distance scale or structure growthmeasurements obtained from the Blue and Red samples. Our results areconsistent with theoretical predictions and our tests on mock samples,which predict that any colour-dependent systematic uncertainty on themeasured BAO position is less than 0.5 per cent.
Percival WJ, Ross AJ, Sánchez AG, Samushia L, Burden A, Crittenden R, Cuesta AJ, Magana MV, Manera M, Beutler F, et al. The clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: including covariance matrix errors. Monthly Notices of the Royal Astronomical Society [Internet]. 2014:244. Publisher's VersionAbstract
We present improved methodology for including covariance matrices in theerror budget of Baryon Oscillation Spectroscopic Survey (BOSS) galaxyclustering measurements, revisiting Data Release 9 (DR9) analyses, anddescribing a method that is used in DR10/11 analyses presented incompanion papers. The precise analysis method adopted is becomingincreasingly important, due to the precision that BOSS can now reach:even using as many as 600 mock catalogues to estimate covariance oftwo-point clustering measurements can still lead to an increase in theerrors of ˜20 per cent, depending on how the cosmologicalparameters of interest are measured. In this paper, we extend previouswork on this contribution to the error budget, deriving formulae forerrors measured by integrating over the likelihood, and to thedistribution of recovered best-fitting parameters fitting thesimulations also used to estimate the covariance matrix. Both aresituations that previous analyses of BOSS have considered. We apply theformulae derived to baryon acoustic oscillation (BAO) and redshift-spacedistortion (RSD) measurements from BOSS in our companion papers. Tofurther aid these analyses, we consider the optimum number of bins touse for two-point measurements using the monopole power spectrum orcorrelation function for BAO, and the monopole and quadrupole moments ofthe correlation function for anisotropic-BAO and RSD measurements.
2013
Weinberg DH, Mortonson MJ, Eisenstein DJ, Hirata C, Riess AG, Rozo E. Observational probes of cosmic acceleration. Physics Reports [Internet]. 2013;530:87-255. Publisher's VersionAbstract
The accelerating expansion of the universe is the most surprisingcosmological discovery in many decades, implying that the universe isdominated by some form of "dark energy" with exotic physical properties,or that Einstein's theory of gravity breaks down on cosmological scales.The profound implications of cosmic acceleration have inspired ambitiousefforts to understand its origin, with experiments that aim to measurethe history of expansion and growth of structure with percent-levelprecision or higher. We review in detail the four most well establishedmethods for making such measurements: Type Ia supernovae, baryonacoustic oscillations (BAO), weak gravitational lensing, and theabundance of galaxy clusters. We pay particular attention to thesystematic uncertainties in these techniques and to strategies forcontrolling them at the level needed to exploit "Stage IV" dark energyfacilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly reviewa number of other approaches including redshift-space distortions, theAlcock-Paczynski effect, and direct measurements of the Hubble constantH0. We present extensive forecasts for constraints on thedark energy equation of state and parameterized deviations from GeneralRelativity, achievable with Stage III and Stage IV experimental programsthat incorporate supernovae, BAO, weak lensing, and cosmic microwavebackground data. We also show the level of precision required forclusters or other methods to provide constraints competitive with thoseof these fiducial programs. We emphasize the value of a balanced programthat employs several of the most powerful methods in combination, bothto cross-check systematic uncertainties and to take advantage ofcomplementary information. Surveys to probe cosmic acceleration producedata sets that support a wide range of scientific investigations, andthey continue the longstanding astronomical tradition of mapping theuniverse in ever greater detail over ever larger scales.
Agarwal N, Ho S, Myers AD, Seo H-J, Ross AJ, Bahcall N, Brinkmann J, Eisenstein DJ, Muna D, Palanque-Delabrouille N, et al. Characterizing unknown systematics in large scale structure surveys. ArXiv e-prints [Internet]. 2013;1309:2954. Publisher's VersionAbstract
Photometric large scale structure (LSS) surveys probe the largestvolumes in the Universe, but are inevitably limited by systematicuncertainties. Imperfect photometric calibration leads to biases in ourmeasurements of the density fields of LSS tracers such as galaxies andquasars, and as a result in cosmological parameter estimation. Earlierstudies have proposed using cross-correlations between differentredshift slices or cross-correlations between different surveys toreduce the effects of such systematics. In this paper we develop amethod to characterize unknown systematics. We demonstrate that while wedo not have sufficient information to correct for unknown systematics inthe data, we can obtain an estimate of their magnitude. We define aparameter to estimate contamination from unknown systematics usingcross-correlations between different redshift slices and proposediscarding bins in the angular power spectrum that lie outside a certaincontamination tolerance level. We show that this method improvesestimates of the bias using simulated data and further apply it tophotometric luminous red galaxies in the Sloan Digital Sky Survey as acase study.
Kim A, Padmanabhan N, Aldering G, Allen S, Baltay C, Cahn R, D'Andrea C, Dalal N, Dawson K, Denney K, et al. Distance Probes of Dark Energy. ArXiv e-prints [Internet]. 2013;1309:5382. Publisher's VersionAbstract
This document presents the results from the Distances subgroup of theCosmic Frontier Community Planning Study (Snowmass 2013). We summarizethe current state of the field as well as future prospects andchallenges. In addition to the established probes using Type IAsupernovae and baryon acoustic oscillations, we also considerprospective methods based on clusters, active galactic nuclei,gravitational wave sirens and strong lensing time delays.
Iršič V, Slosar A, Bailey S, Eisenstein DJ, Font-Ribera A, Le Goff J-M, Lundgren B, McDonald P, O'Connell R, Palanque-Delabrouille N, et al. Detection of Lyβ auto-correlations and Lyα-Lyβ cross-correlations in BOSS Data Release 9. Journal of Cosmology and Astro-Particle Physics [Internet]. 2013;09:016. Publisher's VersionAbstract
The Lyman-β forest refers to a region in the spectra of distantquasars that lies between the rest-frame Lyman-β and Lyman-γemissions. The forest in this region is dominated by a combination ofabsorption due to resonant Lyα and Lyβ scattering. Whenconsidering the 1D Lyβ forest in addition to the 1D Lyαforest, the full statistical description of the data requires four 1Dpower spectra: Lyα and Lyβ auto-power spectra and theLyα-Lyβ real and imaginary cross-power spectra. We describehow these can be measured using an optimal quadratic estimator thatnaturally disentangles Lyα and Lyβ contributions. Using asample of approximately 60,000 quasar sight-lines from the BOSS DataRelease 9, we make the measurement of the one-dimensional power spectrumof fluctuations due to the Lyβ resonant scattering. While we havenot corrected our measurements for resolution damping of the power andother systematic effects carefully enough to use them for cosmologicalconstraints, we can robustly conclude the following: i) Lyβ powerspectrum and Lyα-Lyβ cross spectra are detected with highstatistical significance; ii) the cross-correlation coefficient is ≈1 on large scales; iii) the Lyβ measurements are contaminated bythe associated OVI absorption, which is analogous to the SiIIIcontamination of the Lyα forest. Measurements of the Lyβforest will allow extension of the usable path-length for the Lyαmeasurements while allowing a better understanding of the physics ofintergalactic medium and thus more robust cosmological constraints.
Aird J, Coil AL, Moustakas J, Diamond-Stanic AM, Blanton MR, Cool RJ, Eisenstein DJ, Wong KC, Zhu G. PRIMUS: An Observationally Motivated Model to Connect the Evolution of the Active Galactic Nucleus and Galaxy Populations out to z ~ 1. The Astrophysical Journal [Internet]. 2013;775:41. Publisher's VersionAbstract
We present an observationally motivated model to connect the activegalactic nucleus (AGN) and galaxy populations at 0.2 < z < 1.0 andpredict the AGN X-ray luminosity function (XLF). We start withmeasurements of the stellar mass function of galaxies (from the PrismMulti-object Survey) and populate galaxies with AGNs using models forthe probability of a galaxy hosting an AGN as a function of specificaccretion rate. Our model is based on measurements indicating that thespecific accretion rate distribution is a universal function across awide range of host stellar masses with slope γ1 ≈-0.65 and an overall normalization that evolves with redshift. Wetest several simple assumptions to extend this model to high specificaccretion rates (beyond the measurements) and compare the predictionsfor the XLF with the observed data. We find good agreement with a modelthat allows for a break in the specific accretion rate distribution at apoint corresponding to the Eddington limit, a steep power-law tail tosuper-Eddington ratios with slope \gamma _2=-2.1^{+0.3}_{-0.5}, and ascatter of 0.38 dex in the scaling between black hole and host stellarmass. Our results show that samples of low luminosity AGNs are dominatedby moderately massive galaxies ( {M_*}\sim 10^{10}{--}10^{11} {M}_\odot)growing with a wide range of accretion rates due to the shape of thegalaxy stellar mass function rather than a preference for AGN activityat a particular stellar mass. Luminous AGNs may be a severely skewedpopulation with elevated black hole masses relative to their hostgalaxies and in rare phases of rapid accretion.
Skibba RA, Smith SMM, Coil AL, Moustakas J, Aird J, Blanton MR, Bray AD, Cool RJ, Eisenstein DJ, Mendez AJ, et al. PRIMUS: Galaxy Clustering as a Function of Luminosity and Color at 0.2. ArXiv e-prints [Internet]. 2013;1310:1093. Publisher's VersionAbstract
We present measurements of the luminosity and color-dependence of galaxyclustering at 0.2
Kazin EA, Sánchez AG, Cuesta AJ, Beutler F, Chuang C-H, Eisenstein DJ, Manera M, Padmanabhan N, Percival WJ, Prada F, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measuring H(z) and DA(z) at z = 0.57 with clustering wedges. Monthly Notices of the Royal Astronomical Society [Internet]. 2013;435:64-86. Publisher's VersionAbstract
We analyse the 2D correlation function of the Sloan Digital SkySurvey-III Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sampleof massive galaxies of the ninth data release to measure cosmicexpansion H and the angular diameter distance DA at a meanredshift of = 0.57. We apply, for the first time, a newcorrelation function technique called clustering wedgesξΔμ(s). Using a physically motivated model, theanisotropic baryonic acoustic feature in the galaxy sample is detectedat a significance level of 4.7σ compared to a featureless model.The baryonic acoustic feature is used to obtain model-independentconstraints cz/H/rs = 12.28 ± 0.82 (6.7 percentaccuracy) and DA/rs = 9.05 ± 0.27 (3.0 percent) with a correlation coefficient of -0.5, where rs is thesound horizon scale at the end of the baryonic drag era. We conductthorough tests on the data and 600 simulated realizations, findingrobustness of the results regardless of the details of the analysismethod. Combining this with rs constraints from the cosmicmicrowave background, we obtain H(0.57) = 90.8 ± 6.2 kms-1 Mpc-1 and DA(0.57) = 1386 ±45 Mpc. We use simulations to forecast results of the final BOSS CMASSdata set. We apply the reconstruction technique on the simulationsdemonstrating that the sharpening of the anisotropic baryonic acousticfeature should improve the detection as well as tighten constraints of Hand DA by ˜30 per cent on average.
Font-Ribera A, Kirkby D, Busca N, Miralda-Escudé J, Ross NP, Slosar A, Aubourg É, Bailey S, Bhardwaj V, Bautista J, et al. Quasar-Lyman $\alpha$ Forest Cross-Correlation from BOSS DR11 : Baryon Acoustic Oscillations. ArXiv e-prints [Internet]. 2013;1311:1767. Publisher's VersionAbstract
We measure the large-scale cross-correlation of quasars with the Lymanalpha forest absorption, using over 164,000 quasars from Data Release 11of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend theprevious study of roughly 60,000 quasars from Data Release 9 to largerseparations, allowing a measurement of the Baryonic Acoustic Oscillation(BAO) scale along the line of sight $c/(H(z=2.36) ~ r_s) = 9.0 \pm 0.3$and across the line of sight $D_A(z=2.36)~ / ~ r_s = 10.8 \pm 0.4$,consistent with CMB and other BAO data. Using the best fit value of thesound horizon from Planck data ($r_s=147.49 Mpc$), we can translatethese results to a measurement of the Hubble parameter of $H(z=2.36) =226 \pm 8 km/s$ and of the angular diameter distance of $D_A(z=2.36) =1590 \pm 60 Mpc$. The measured cross-correlation function and an updateof the code to fit the BAO scale (baofit) are made publicly available.
Majewski SR, Hasselquist S, Łokas EL, Nidever DL, Frinchaboy PM, García Pérez AE, Johnston KV, Mészáros S, Shetrone M, Allende Prieto C, et al. Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project. The Astrophysical Journal Letters [Internet]. 2013;777:L13. Publisher's VersionAbstract
The dynamics of the core of the Sagittarius (Sgr) dwarf spheroidal(dSph) galaxy are explored using high-resolution (R ~ 22, 500), H-band,near-infrared spectra of over 1000 giant stars in the central 3deg2 of the system, of which 328 are identified as Sgrmembers. These data, among some of the earliest observations from theSloan Digital Sky Survey III/Apache Point Observatory Galactic EvolutionExperiment (APOGEE) and the largest published sample of high resolutionSgr dSph spectra to date, reveal a distinct gradient in the velocitydispersion of Sgr from 11 to 14 km s–1 for radii>0.°8 from center to a dynamical cold point of 8 kms–1 in the Sgr center—a trend differing from thatfound in previous kinematical analyses of Sgr over larger scales thatsuggests a more or less flat dispersion profile at these radii.Well-fitting mass models with either cored and cusped dark matterdistributions can be found to match the kinematical results, althoughthe cored profile succeeds with significantly more isotropic stellarorbits than required for a cusped profile. It is unlikely that the coldpoint reflects an unusual mass distribution. The dispersion gradient mayarise from variations in the mixture of populations with distinctkinematics within the dSph; this explanation is suggested (e.g., bydetection of a metallicity gradient across similar radii), but notconfirmed, by the present data. Despite these remaining uncertaintiesabout their interpretation, these early test data (including some frominstrument commissioning) demonstrate APOGEE's usefulness for precisiondynamical studies, even for fields observed at extreme airmasses.
Xu X, Cuesta AJ, Padmanabhan N, Eisenstein DJ, McBride CK. Measuring DA and H at z=0.35 from the SDSS DR7 LRGs using baryon acoustic oscillations. Monthly Notices of the Royal Astronomical Society [Internet]. 2013;431:2834-2860. Publisher's VersionAbstract
We present measurements of the angular diameter distanceDA(z) and the Hubble parameter H(z) at z = 0.35 using theanisotropy of the baryon acoustic oscillation (BAO) signal measured inthe galaxy clustering distribution of the Sloan Digital Sky Survey(SDSS) Data Release 7 (DR7) luminous red galaxy (LRG) sample. Our workis the first to apply density-field reconstruction to an anisotropicanalysis of the acoustic peak. Reconstruction partially removes theeffects of non-linear evolution and redshift-space distortions in orderto sharpen the acoustic signal. We present the theoretical frameworkbehind the anisotropic BAO signal and give a detailed account of thefitting model we use to extract this signal from the data. Our methodfocuses only on the acoustic peak anisotropy, rather than the moremodel-dependent anisotropic information from the broad-band power. Wetest the robustness of our analysis methods on 160 Large Suite of DarkMatter Simulation DR7 mock catalogues and find that our models areunbiased at the ˜0.2 per cent level in measuring the BAOanisotropy. After reconstruction we measure DA(z = 0.35) =1050 ± 38 Mpc and H(z = 0.35) = 84.4 ± 7.0 kms-1 Mpc-1 assuming a sound horizon ofrs = 152.76 Mpc. Note that these measurements are correlatedwith a correlation coefficient of 0.57. This represents a factor of 1.4improvement in the error on DA relative to thepre-reconstruction case; a factor of 1.2 improvement is seen for H.
Lee K-G, Bailey S, Bartsch LE, Carithers W, Dawson KS, Kirkby D, Lundgren B, Margala D, Palanque-Delabrouille N, Pieri MM, et al. The BOSS Lyα Forest Sample from SDSS Data Release 9. The Astronomical Journal [Internet]. 2013;145:69. Publisher's VersionAbstract
We present the BOSS Lyman-α (Lyα) Forest Sample from SDSSData Release 9, comprising 54,468 quasar spectra with z qso> 2.15 suitable for Lyα forest analysis. This data set probesthe intergalactic medium with absorption redshifts 2.0 < zα < 5.7 over an area of 3275 deg2, andencompasses an approximate comoving volume of 20 h -3Gpc3. With each spectrum, we have included several productsdesigned to aid in Lyα forest analysis: improved sky masks thatflag pixels where data may be unreliable, corrections for known biasesin the pipeline estimated noise, masks for the cores of damped Lyαsystems and corrections for their wings, and estimates of the unabsorbedcontinua so that the observed flux can be converted to a fractionaltransmission. The continua are derived using a principal component fitto the quasar spectrum redward of rest-frame Lyα (λ >1216 Å), extrapolated into the forest region and normalized by alinear function to fit the expected evolution of the Lyα forest
Mendez AJ, Coil AL, Aird J, Diamond-Stanic AM, Moustakas J, Blanton MR, Cool RJ, Eisenstein DJ, Wong KC, Zhu G. PRIMUS: Infrared and X-Ray AGN Selection Techniques at 0.2 < z < 1.2. The Astrophysical Journal [Internet]. 2013;770:40. Publisher's VersionAbstract
We present a study of Spitzer/IRAC and X-ray active galactic nucleus(AGN) selection techniques in order to quantify the overlap, uniqueness,contamination, and completeness of each. We investigate how the overlapand possible contamination of the samples depend on the depth of boththe IR and X-ray data. We use Spitzer/IRAC imaging, Chandra andXMM-Newton X-ray imaging, and spectroscopic redshifts from the PRismMUlti-object Survey to construct galaxy and AGN samples at 0.2 < z< 1.2 over 8 deg2. We construct samples over a wide rangeof IRAC flux limits (SWIRE to GOODS depth) and X-ray flux limits (10 ksto 2 Ms). We compare IR-AGN samples defined using both the IRAC colorselection of Stern et al. and Donley et al. with X-ray-detected AGNsamples. For roughly similar depth IR and X-ray surveys, we find that
Tassev S, Zaldarriaga M, Eisenstein DJ. Solving large scale structure in ten easy steps with COLA. Journal of Cosmology and Astro-Particle Physics [Internet]. 2013;06:036. Publisher's VersionAbstract
We present the COmoving Lagrangian Acceleration (COLA) method: an N-bodymethod for solving for Large Scale Structure (LSS) in a frame that iscomoving with observers following trajectories calculated in LagrangianPerturbation Theory (LPT). Unlike standard N-body methods, the COLAmethod can straightforwardly trade accuracy at small-scales in order togain computational speed without sacrificing accuracy at large scales.This is especially useful for cheaply generating large ensembles ofaccurate mock halo catalogs required to study galaxy clustering and weaklensing, as those catalogs are essential for performing detailed erroranalysis for ongoing and future surveys of LSS. As an illustration, weran a COLA-based N-body code on a box of size 100 Mpc/h with particlesof mass ≈ 5 × 109Msolar/h. Running thecode with only 10 timesteps was sufficient to obtain an accuratedescription of halo statistics down to halo masses of at least1011Msolar/h. This is only at a modest speedpenalty when compared to mocks obtained with LPT. A standard detailedN-body run is orders of magnitude slower than our COLA-based code. Thespeed-up we obtain with COLA is due to the fact that we calculate thelarge-scale dynamics exactly using LPT, while letting the N-body codesolve for the small scales, without requiring it to capture exactly theinternal dynamics of halos. Achieving a similar level of accuracy inhalo statistics without the COLA method requires at least 3 times moretimesteps than when COLA is employed.
Ahn CP, Alexandroff R, Allende Prieto C, Anders F, Anderson SF, Anderton T, Andrews BH, Aubourg É, Bailey S, Bastien FA, et al. The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment. ArXiv e-prints [Internet]. 2013;1307:7735. Publisher's VersionAbstract
The Sloan Digital Sky Survey (SDSS) has been in operation since 2000April. This paper presents the tenth public data release (DR10) from itscurrent incarnation, SDSS-III. This data release includes the firstspectroscopic data from the Apache Point Observatory Galaxy EvolutionExperiment (APOGEE), along with spectroscopic data from the BaryonOscillation Spectroscopic Survey (BOSS) taken through 2012 July. TheAPOGEE instrument is a near-infrared R~22,500 300-fiber spectrographcovering 1.514--1.696 microns. The APOGEE survey is studying thechemical abundances and radial velocities of roughly 100,000 red giantstar candidates in the bulge, bar, disk, and halo of the Milky Way. DR10includes 178,397 spectra of 57,454 stars, each typically observed threeor more times, from APOGEE. Derived quantities from these spectra(radial velocities, effective temperatures, surface gravities, andmetallicities) are also included.DR10 also roughly doubles the number ofBOSS spectra over those included in the ninth data release. DR10includes a total of 1,507,954 BOSS spectra, comprising 927,844 galaxyspectra; 182,009 quasar spectra; and 159,327 stellar spectra, selectedover 6373.2 square degrees.
Dawson KS, Schlegel DJ, Ahn CP, Anderson SF, Aubourg É, Bailey S, Barkhouser RH, Bautista JE, Beifiori A, Berlind AA, et al. The Baryon Oscillation Spectroscopic Survey of SDSS-III. The Astronomical Journal [Internet]. 2013;145:10. Publisher's VersionAbstract
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed tomeasure the scale of baryon acoustic oscillations (BAO) in theclustering of matter over a larger volume than the combined efforts ofall previous spectroscopic surveys of large-scale structure. BOSS uses1.5 million luminous galaxies as faint as i = 19.9 over 10,000deg2 to measure BAO to redshifts z < 0.7. Observations ofneutral hydrogen in the Lyα forest in more than 150,000 quasarspectra (g < 22) will constrain BAO over the redshift range 2.15