Sanchez AG, Montesano F, Kazin EA, Aubourg E, Beutler F, Brinkmann J, Brownstein JR, Cuesta AJ, Dawson KS, Eisenstein DJ, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the full shape of the clustering wedges in the data release 10 and 11 galaxy samples. ArXiv e-prints. 2013;1312 :4854. Publisher's VersionAbstract
We explore the cosmological implications of the angle-averagedcorrelation function, xi(s), and the clustering wedges, xi_perp(s) andxi_para(s), of the LOWZ and CMASS galaxy samples from Data Release 10and 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. Ourresults show no significant evidence for a deviation from the standardLCDM model. The combination of the information from our clusteringmeasurements with recent data from the cosmic microwave background issufficient to constrain the curvature of the Universe to Omega_k =
Anderson L, Aubourg E, Bailey S, Beutler F, Bhardwaj V, Blanton M, Bolton AS, Brinkmann J, Brownstein JR, Burden A, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samples. ArXiv e-prints. 2013;1312 :4877. Publisher's VersionAbstract
We present a one per cent measurement of the cosmic distance scale fromthe detections of the baryon acoustic oscillations in the clustering ofgalaxies from the Baryon Oscillation Spectroscopic Survey (BOSS), whichis part of the Sloan Digital Sky Survey III (SDSS-III). Our results comefrom the Data Release 11 (DR11) sample, containing nearly one milliongalaxies and covering approximately 8500 square degrees and the redshiftrange $0.2
Chuang C-H, Prada F, Beutler F, Eisenstein DJ, Escoffier S, Ho S, Kneib J-P, Manera M, Nuza SE, Schlegel DJ, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements from CMASS and LOWZ anisotropic galaxy clustering. ArXiv e-prints. 2013;1312 :4889. Publisher's VersionAbstract
With the largest spectroscopic galaxy survey volume drawn from theSDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), we can extractcosmological constraints from the measurements of redshift and geometricdistortions at quasi-linear scales (e.g. above 50 Mpc/h), which can bemodeled by perturbation theory. We analyze the broad-range shape of themonopole and quadrupole correlation functions of the BOSS Data Release11 (DR11) CMASS galaxy sample, at the effective redshift z=0.57, toobtain constraints on the Hubble expansion rate H(z), theangular-diameter distance D_A(z), the normalized growth ratef(z)\sigma_8(z), and the physical matter density \Omega_mh^2. We provideaccurate measurements on {H^{-1}R_{fid}^{-1.0}, D_A R_{fid}^{-0.96},f\sigma_8(\Omega_m h^2)^{0.45}}, where R_{fid}\equiv r_s/r_{s,fid}, r_sis the comoving sound horizon at the drag epoch, and r_{s,fid} is thesound scale of the fiducial cosmology used in this study. We alsoextract cosmological constraints from BOSS DR11 LOWZ sample, at theeffective redshift z=0.32, by including small scales (e.g., down to 30Mpc/h), and model small scales with Finger of God effect. The parameterswhich are not well constrained by our galaxy clustering analysis aremarginalized over with wide flat priors. Since no priors from other datasets, e.g., cosmic microwave background (CMB), are adopted and no darkenergy models are assumed, our results from BOSS CMASS and LOWZ galaxyclustering alone may be combined with other data sets, i.e., CMB, SNe,lensing or other galaxy clustering data to constrain the parameters of agiven cosmological model. We find the redshift distortion measurementsfrom most of the galaxy clustering analyses (including this study) favorWMAP9 than Planck and favor wCDM than \LambdaCDM or o\LambdaCDM. Theuncertainty on the dark energy equation of state parameter fromCMB+CMASS is about 8 per cent.
Samushia L, Reid BA, White M, Percival WJ, Cuesta AJ, Zhao G-bo, Ross AJ, Manera M, Aubourg É, Beutler F, et al. The Clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Measuring growth rate and geometry with anisotropic clustering. ArXiv e-prints. 2013;1312 :4899. Publisher's VersionAbstract
We use the observed anisotropic clustering of galaxies in the BaryonOscillation Spectroscopic Survey Data Release 11 CMASS sample to measurethe linear growth rate of structure, the Hubble expansion rate and thecomoving distance scale. Our sample covers 8498 ${\rm deg}^2$ andencloses an effective volume of 6.0 ${\rm Gpc}^3$ at an effectiveredshift of $\bar{z} = 0.57$. We find $f\sigma_8 = 0.441 \pm 0.044$, $H= 93.1 \pm 3.0\ {\mathrm{km}\ \mathrm{s}^{-1} \mathrm{Mpc}^{-1}}$ and$D_{\rm A} = 1380 \pm 23\ {\rm Mpc}$ when fitting the growth andexpansion rate simultaneously. When we fix the background expansion tothe one predicted by spatially-flat $\Lambda$CDM model in agreement withrecent Planck results, we find $f\sigma_8 = 0.447 \pm 0.028$ (6 per centaccuracy). While our measurements are generally consistent with thepredictions of $\Lambda$CDM and General Relativity, they mildly favormodels in which the strength of gravitational interactions is weakerthan what is predicted by General Relativity. Combining our measurementswith recent cosmic microwave background data results in tightconstraints on basic cosmological parameters and deviations from thestandard cosmological model. Separately varying these parameters, wefind $w = -0.983 \pm 0.075$ (8 per cent accuracy) and $\gamma = 0.69 \pm0.11$ (16 per cent accuracy) for the effective equation of state of darkenergy and the growth rate index, respectively. Both constraints are ingood agreement with the standard model values of $w=-1$ and $\gamma =0.554$.
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. 2013;1310 :1093. Publisher's VersionAbstract
We present measurements of the luminosity and color-dependence of galaxyclustering at 0.2
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. 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.
Vargas Magaña M, Ho S, Xu X, Sánchez AG, O'Connell R, Eisenstein DJ, Cuesta AJ, Percival WJ, Ross AJ, Aubourg E, et al. SDSS-III Baryon Oscillation Spectroscopic Survey: Analysis of Potential Systematics in Fitting of Baryon Acoustic Feature. ArXiv e-prints. 2013;1312 :4996. Publisher's VersionAbstract
Extraction of the Baryon Acoustic Oscillations (BAO) to percent levelaccuracy is challenging and demands an understanding of many potentialsystematic to an accuracy well below 1 per cent, in order ensure thatthey do not combine significantly when compared to statistical error ofthe BAO measurement. Sloan Digital Sky Survey (SDSS)-III BaryonOscillation Spectroscopic Survey (BOSS) SDSS Data Release Eleven (DR11)
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. 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
Kleinman SJ, Kepler SO, Koester D, Pelisoli I, Peçanha V, Nitta A, Costa JES, Krzesinski J, Dufour P, Lachapelle F-R, et al. SDSS DR7 White Dwarf Catalog. The Astrophysical Journal Supplement Series. 2013;204 :5. Publisher's VersionAbstract
We present a new catalog of spectroscopically confirmed white dwarfstars from the Sloan Digital Sky Survey (SDSS) Data Release 7spectroscopic catalog. We find 20,407 white dwarf spectra, representing19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011DB white dwarf spectra from 12,843 and 923 stars, respectively. Thesenumbers represent more than a factor of two increase in the total numberof white dwarf stars from the previous SDSS white dwarf catalogs basedon DR4 data. Our distribution of subtypes varies from previous catalogsdue to our more conservative, manual classifications of each star in ourcatalog, supplementing our automatic fits. In particular, we find alarge number of magnetic white dwarf stars whose small Zeeman splittingsmimic increased Stark broadening that would otherwise result in anoverestimated log g if fit as a non-magnetic white dwarf. We calculatemean DA and DB masses for our clean, non-magnetic sample and find the DBmean mass is statistically larger than that for the DAs.
Busca NG, Delubac T, Rich J, Bailey S, Font-Ribera A, Kirkby D, Le Goff J-M, Pieri MM, Slosar A, Aubourg É, et al. Baryon acoustic oscillations in the Lyα forest of BOSS quasars. Astronomy and Astrophysics. 2013;552 :96. Publisher's VersionAbstract
We report a detection of the baryon acoustic oscillation (BAO) featurein the three-dimensional correlation function of the transmitted fluxfraction in the Lyα forest of high-redshift quasars. The studyuses 48 640 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from theBaryon Oscillation Spectroscopic Survey (BOSS) of the third generationof the Sloan Digital Sky Survey (SDSS-III). At a mean redshift z = 2.3,we measure the monopole and quadrupole components of the correlationfunction for separations in the range 20 h-1 Mpc < r <200 h-1 Mpc. A peak in the correlation function is seen at aseparation equal to (1.01 ± 0.03) times the distance expected forthe BAO peak within a concordance ΛCDM cosmology. This firstdetection of the BAO peak at high redshift, when the universe wasstrongly matter dominated, results in constraints on the angulardiameter distance DA and the expansion rate H at z = 2.3that, combined with priors on H0 and the baryon density,require the existence of dark energy. Combined with constraints derivedfrom cosmic microwave background observations, this result implies H(z =2.3) = (224 ± 8) km s-1 Mpc-1, indicatingthat the time derivative of the cosmological scale parameter ȧ =H(z = 2.3)/(1 + z) is significantly greater than that measured with BAOat z ~ 0.5. This demonstrates that the expansion was decelerating in therange 0.7 < z < 2.3, as expected from the matter domination duringthis epoch. Combined with measurements of H0, one sees thepattern of deceleration followed by acceleration characteristic of adark-energy dominated universe.Appendices are available in electronic form at
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. 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
Parejko JK, Sunayama T, Padmanabhan N, Wake DA, Berlind AA, Bizyaev D, Blanton M, Bolton AS, van den Bosch F, Brinkmann J, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: the low-redshift sample. Monthly Notices of the Royal Astronomical Society. 2013;429 :98-112. Publisher's VersionAbstract
We report on the small-scale (0.5 < r < 40 h-1 Mpc)clustering of 78 895 massive (M* ˜ 1011.3M) galaxies at 0.2 < z < 0.4 from the first twoyears of data from the Baryon Oscillation Spectroscopic Survey (BOSS),to be released as part of Sloan Digital Sky Survey (SDSS) Data Release 9(DR9). We describe the sample selection, basic properties of thegalaxies and caveats for working with the data. We calculate the real-and redshift-space two-point correlation functions of these galaxies,fit these measurements using halo occupation distribution (HOD)modelling within dark matter cosmological simulations, and estimate theerrors using mock catalogues. These galaxies lie in massive haloes, witha mean halo mass of 5.2 × 1013 h-1M, a large-scale bias of ˜2.0 and a satellitefraction of 12 ± 2 per cent. Thus, these galaxies occupy haloeswith average masses in between those of the higher redshift BOSS CMASSsample and the original SDSS I/II luminous red galaxy sample.
Guo H, Zehavi I, Zheng Z, Weinberg DH, Berlind AA, Blanton M, Chen Y, Eisenstein DJ, Ho S, Kazin E, et al. The Clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Luminosity and Color Dependence and Redshift Evolution. The Astrophysical Journal. 2013;767 :122. Publisher's VersionAbstract
We measure the luminosity and color dependence and the redshiftevolution of galaxy clustering in the Sloan Digital Sky Survey-IIIBaryon Oscillation Spectroscopic Survey Ninth Data Release. We focus onthe projected two-point correlation function (2PCF) of subsets of itsCMASS sample, which includes about 260,000 galaxies over ~3300deg2 in the redshift range 0.43 < z < 0.7. To minimizethe selection effect on galaxy clustering, we construct well-definedluminosity and color subsamples by carefully accounting for the CMASSgalaxy selection cuts. The 2PCF of the whole CMASS sample, ifapproximated by a power-law, has a correlation length of r 0= 7.93 ± 0.06 h -1 Mpc and an index of γ =1.85 ± 0.01. Clear dependences on galaxy luminosity and color arefound for the projected 2PCF in all redshift bins, with more luminousand redder galaxies generally exhibiting stronger clustering and steeper2PCF. The color dependence is also clearly seen for galaxies within thered sequence, consistent with the behavior of SDSS-II main samplegalaxies at lower redshifts. At a given luminosity (k + e corrected), nosignificant evolution of the projected 2PCFs with redshift is detectedfor red sequence galaxies. We also construct galaxy samples of fixednumber density at different redshifts, using redshift-dependentmagnitude thresholds. The clustering of these galaxies in the CMASSredshift range is found to be consistent with that predicted by passiveevolution. Our measurements of the luminosity and color dependence andredshift evolution of galaxy clustering will allow for detailed modelingof the relation between galaxies and dark matter halos and newconstraints on galaxy formation and evolution.
Ross AJ, Percival WJ, Carnero A, Zhao G-bo, Manera M, Raccanelli A, Aubourg E, Bizyaev D, Brewington H, Brinkmann J, et al. The clustering of galaxies in the SDSS-III DR9 Baryon Oscillation Spectroscopic Survey: constraints on primordial non-Gaussianity. Monthly Notices of the Royal Astronomical Society. 2013;428 :1116-1127. Publisher's VersionAbstract
We analyse the density field of 264 283 galaxies observed by the SloanDigital Sky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey(BOSS) and included in the SDSS Data Release 9 (DR9). In total, the SDSSDR9 BOSS data include spectroscopic redshifts for over 400 000 galaxiesspread over a footprint of more than 3000 deg2. We measurethe power spectrum of these galaxies with redshifts 0.43 < z < 0.7in order to constrain the amount of local non-Gaussianity,f{_N_L^local}, in the primordial density field, paying particularattention to the impact of systematic uncertainties. The BOSS galaxydensity field is systematically affected by the local stellar densityand this influences the ability to accurately measure f{_N_L^local}. Inthe absence of any correction, we find (erroneously) that theprobability that f{_N_L^local} is greater than zero, P(f{_N_L^local}> 0), is 99.5 per cent. After quantifying and correcting for thesystematic bias and including the added uncertainty, we find - 45 0) = 91.0 per cent. A more conservative approach assumes that wehave only learnt the k dependence of the systematic bias and allows anyamplitude for the systematic correction; we find that the systematiceffect is not fully degenerate with that of f{_N_L^local}, and wedetermine that -82 < f{_N_L^local} < 178 (at 95 per centconfidence) and P(f{_N_L^local} > 0) = 68 per cent. This analysisdemonstrates the importance of accounting for the impact of Galacticforegrounds on f{_N_L^local} measurements. We outline the methods thataccount for these systematic biases and uncertainties. We expect ourmethods to yield robust constraints on f{_N_L^local} for both our ownand future large-scale structure investigations.
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. 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.
Moustakas J, Coil AL, Aird J, Blanton MR, Cool RJ, Eisenstein DJ, Mendez AJ, Wong KC, Zhu G, Arnouts S. PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function from z = 0-1. The Astrophysical Journal. 2013;767 :50. Publisher's VersionAbstract
We measure the evolution of the stellar mass function (SMF) from z = 0-1using multi-wavelength imaging and spectroscopic redshifts from thePRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey(SDSS). From PRIMUS we construct an i < 23 flux-limited sample of~40, 000 galaxies at z = 0.2-1.0 over five fields totaling ≈5.5deg2, and from the SDSS we select ~170, 000 galaxies at z =0.01-0.2 that we analyze consistently with respect to PRIMUS to minimizesystematic errors in our evolutionary measurements. We find that the SMFof all galaxies evolves relatively little since z = 1, although we do
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. 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
Cool RJ, Moustakas J, Blanton MR, Burles SM, Coil AL, Eisenstein DJ, Wong KC, Zhu G, Aird J, Bernstein RA, et al. The PRIsm MUlti-object Survey (PRIMUS). II. Data Reduction and Redshift Fitting. The Astrophysical Journal. 2013;767 :118. Publisher's VersionAbstract
The PRIsm MUlti-object Survey (PRIMUS) is a spectroscopic galaxyredshift survey to z ~ 1 completed with a low-dispersion prism andslitmasks allowing for simultaneous observations of ~2500 objects over0.18 deg2. The final PRIMUS catalog includes ~130,000 robustredshifts over 9.1 deg2. In this paper, we summarize thePRIMUS observational strategy and present the data reduction detailsused to measure redshifts, redshift precision, and survey completeness.The survey motivation, observational techniques, fields, targetselection, slitmask design, and observations are presented in Coil etal. Comparisons to existing higher-resolution spectroscopic measurementsshow a typical precision of σ z /(1 + z) = 0.005.PRIMUS, both in area and number of redshifts, is the largest faintgalaxy redshift survey completed to date and is allowing for precisemeasurements of the relationship between active galactic nuclei andtheir hosts, the effects of environment on galaxy evolution, and thebuild up of galactic systems over the latter half of cosmic history.
García Pérez AE, Cunha K, Shetrone M, Majewski SR, Johnson JA, Smith VV, Schiavon RP, Holtzman J, Nidever D, Zasowski G, et al. Very Metal-poor Stars in the Outer Galactic Bulge Found by the APOGEE Survey. The Astrophysical Journal Letters. 2013;767 :L9. Publisher's VersionAbstract
Despite its importance for understanding the nature of early stellargenerations and for constraining Galactic bulge formation models, atpresent little is known about the metal-poor stellar content of thecentral Milky Way. This is a consequence of the great distances involvedand intervening dust obscuration, which challenge optical studies.However, the Apache Point Observatory Galactic Evolution Experiment(APOGEE), a wide-area, multifiber, high-resolution spectroscopic surveywithin Sloan Digital Sky Survey III, is exploring the chemistry of allGalactic stellar populations at infrared wavelengths, with particularemphasis on the disk and the bulge. An automated spectral analysis ofdata on 2403 giant stars in 12 fields in the bulge obtained duringAPOGEE commissioning yielded five stars with low metallicity ([Fe/H]<= -1.7), including two that are very metal-poor [Fe/H] ~-2.1 by bulge standards. Luminosity-based distance estimates placethe 5 stars within the outer bulge, where 1246 of the other analyzedstars may reside. A manual reanalysis of the spectra verifies the lowmetallicities, and finds these stars to be enhanced in theα-elements O, Mg, and Si without significant α-patterndifferences with other local halo or metal-weak thick-disk stars ofsimilar metallicity, or even with other more metal-rich bulge stars.While neither the kinematics nor chemistry of these stars can yetdefinitively determine which, if any, are truly bulge members, ratherthan denizens of other populations co-located with the bulge, the newlyidentified stars reveal that the chemistry of metal-poor stars in thecentral Galaxy resembles that of metal-weak thick-disk stars at similarmetallicity.
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. 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.