We present measurements of the angular diameter distance D_A(z) and theHubble parameter H(z) at z=0.35 using the anisotropy of the baryonacoustic oscillation (BAO) signal measured in the galaxy clusteringdistribution of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7)Luminous Red Galaxies (LRG) sample. Our work is the first to applydensity-field reconstruction to an anisotropic analysis of the acousticpeak. Reconstruction partially removes the effects of non-linearevolution and redshift-space distortions in order to sharpen theacoustic signal. We present the theoretical framework behind theanisotropic BAO signal and give a detailed account of the fitting modelwe use to extract this signal from the data. Our method focuses only onthe acoustic peak anisotropy, rather than the more model-dependentanisotropic information from the broadband power. We test the robustnessof our analysis methods on 160 LasDamas DR7 mock catalogues and find
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 ambitiousexperimental efforts to measure the history of expansion and growth ofstructure with percent-level precision or higher. We review in detailthe four most well established methods for making such measurements:Type Ia supernovae, baryon acoustic oscillations (BAO), weakgravitational lensing, and galaxy clusters. We pay particular attentionto the systematic uncertainties in these techniques and to strategiesfor controlling them at the level needed to exploit "Stage IV" darkenergy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We brieflyreview a number of other approaches including redshift-spacedistortions, the Alcock-Paczynski test, and direct measurements of H_0.We present extensive forecasts for constraints on the dark energyequation of state and parameterized deviations from GR, achievable withStage III and Stage IV experimental programs that incorporatesupernovae, BAO, weak lensing, and CMB data. We also show the level ofprecision required for other methods to provide constraints competitivewith those of these fiducial programs. We emphasize the value of abalanced program that employs several of the most powerful methods incombination, both to cross-check systematic uncertainties and to takeadvantage of complementary information. Surveys to probe cosmicacceleration produce data sets with broad applications, and theycontinue the longstanding astronomical tradition of mapping the universein ever greater detail over ever larger scales.
We present evidence that the incidence of active galactic nuclei (AGNs)and the distribution of their accretion rates do not depend on thestellar masses of their host galaxies, contrary to previous studies. Weuse hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS,COSMOS, and ELAIS-S1) with redshifts from the Prism Multi-object Surveyto identify 242 AGNs with L 2-10 keV = 1042-44 ergs-1 within a parent sample of ~25,000 galaxies at 0.2 < z< 1.0 over ~3.4 deg2 and to i ~ 23. We find that althoughthe fraction of galaxies hosting an AGN at fixed X-ray luminosity risesstrongly with stellar mass, the distribution of X-ray luminosities isindependent of mass. Furthermore, we show that the probability that agalaxy will host an AGN can be defined by a universal Eddington ratiodistribution that is independent of the host galaxy stellar mass and hasa power-law shape with slope -0.65. These results demonstrate that AGNsare prevalent at all stellar masses in the range 9.5 and that the samephysical processes regulate AGN activity in all galaxies in this stellarmass range. While a higher AGN fraction may be observed in massivegalaxies, this is a selection effect related to the underlying Eddingtonratio distribution. We also find that the AGN fraction drops rapidlybetween z ~ 1 and the present day and is moderately enhanced (factor ~2)in galaxies with blue or green optical colors. Consequently, while AGNactivity and star formation appear to be globally correlated, we do notfind evidence that the presence of an AGN is related to the quenching ofstar formation or the color transformation of galaxies.
The Sloan Digital Sky Survey is now in its third phase (SDSS-III;Eisenstein et al. 2011AJ....142...72E) and is carrying out a combinationof four interleaved surveys that will continue until the summer of 2014.One of those surveys, the Baryon Oscillation Spectroscopic Survey(BOSS), commenced operations in late 2009 and is using essentially allthe dark time for SDSS-III. BOSS uses the same 2.5m Sloan Foundationtelescope that was used in SDSS-I/II, but since BOSS will observefainter targets, the fiber-fed spectrographs have been significantlyupgraded. These upgrades include: new CCDs with improved blue and redresponse; 1000 2" instead of 640 3" optical diameter fibers; higherthroughput gratings over a spectral range of 3600-10000Å at aresolution of about 2000, and improved optics.Prior to the commencement of BOSS spectroscopy, we carried outspectroscopy of quasar candidates selected from co-added photometry inSDSS Stripe 82. Observations of these candidates were carried out inqueue mode between 2008 September and 2009 January using the Hectospecmulti-fiber spectrograph on the 6.5m Multiple Mirror Telescope (MMT). InTables 14 and 15, we provide positions, PSF photometry (as observed,uncorrected for Galactic extinction), and redshifts for confirmedquasars from the MMT survey. Objects that are not flagged Primary in theCAS are listed separately (table 15).(2 data files).
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-yearspectroscopic survey of 10,000 deg2, achieved first light inlate 2009. One of the key goals of BOSS is to measure the signature ofbaryon acoustic oscillations (BAOs) in the distribution of Lyαabsorption from the spectra of a sample of ~150,000 z > 2.2 quasars.Along with measuring the angular diameter distance at z ≈ 2.5, BOSSwill provide the first direct measurement of the expansion rate of theuniverse at z > 2. One of the biggest challenges in achieving thisgoal is an efficient target selection algorithm for quasars in theredshift range 2.2 < z < 3.5, where their colors tend to overlapthose of the far more numerous stars. During the first year of the BOSSsurvey, quasar target selection (QTS) methods were developed and testedto meet the requirement of delivering at least 15 quasarsdeg-2 in this redshift range, with a goal of 20 out of 40targets deg-2 allocated to the quasar survey. To achievethese surface densities, the magnitude limit of the quasar targets wasset at g <= 22.0 or r <= 21.85. While detection of the BAOsignature in the distribution of Lyα absorption in quasar spectradoes not require a uniform target selection algorithm, many otherastrophysical studies do. We have therefore defined a uniformly selectedsubsample of 20 targets deg-2, for which the selection
Commissioning observations with the Apache Point Observatory GalacticEvolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III,have produced radial velocities (RVs) for ~4700 K/M-giant stars in theMilky Way (MW) bulge. These high-resolution (R ~ 22, 500), high-S/N(>100 per resolution element), near-infrared (NIR; 1.51-1.70 μm)spectra provide accurate RVs (epsilonV ~ 0.2 kms-1) for the sample of stars in 18 Galactic bulge fieldsspanning -1° -32°. This represents the largest NIR high-resolution spectroscopicsample of giant stars ever assembled in this region of the Galaxy. Acold (σV ~ 30 km s-1), high-velocity peak (VGSR ≈ +200 km s-1) is found to comprise a
We report a detection of the baryon acoustic oscillation (BAO) featurein the three-dimensional correlation function of the transmitted fluxfraction in the \Lya forest of high-redshift quasars. The study uses48,640 quasars in the redshift range $2.1\le z \le 3.5$ from the BaryonOscillation Spectroscopic Survey (BOSS) of the third generation of theSloan Digital Sky Survey (SDSS-III). At a mean redshift $z=2.3$, wemeasure the monopole and quadrupole components of the correlationfunction for separations in the range $20\hMpc
We present an analysis of the evolution of the central mass-densityprofile of massive elliptical galaxies from the SLACS and BELLS stronggravitational lens samples over the redshift interval z ≈ 0.1-0.6,based on the combination of strong-lensing aperture mass and stellarvelocity-dispersion constraints. We find a significant trend towardsteeper mass profiles (parameterized by the power-law density model withρvpropr -γ) at later cosmic times, with magnitude d< γ > /dz = -0.60 ± 0.15. We show that the combinedlens-galaxy sample is consistent with a non-evolving distribution ofstellar velocity dispersions. Considering possible additional dependenceof <γ > on lens-galaxy stellar mass, effective radius, andSérsic index, we find marginal evidence for shallower massprofiles at higher masses and larger sizes, but with a significance thatis subdominant to the redshift dependence. Using the results ofpublished Monte Carlo simulations of spectroscopic lens surveys, weverify that our mass-profile evolution result cannot be explained bylensing selection biases as a function of redshift. Interpreted as atrue evolutionary signal, our result suggests that major dry mergersinvolving off-axis trajectories play a significant role in the evolutionof the average mass-density structure of massive early-type galaxiesover the past 6 Gyr. We also consider an alternative non-evolutionaryhypothesis based on variations in the strong-lensing measurementaperture with redshift, which would imply the detection of an"inflection zone" marking the transition between the baryon-dominatedand dark-matter halo-dominated regions of the lens galaxies. Furtherobservations of the combined SLACS+BELLS sample can constrain thispicture more precisely, and enable a more detailed investigation of themultivariate dependences of galaxy mass structure across cosmic time.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555. These observations are associated withprograms 10174, 10494, 10587, 10798, 10886, and 12209.
We obtain constraints on cosmological parameters from the sphericallyaveraged redshift-space correlation function of the CMASS Data Release 9(DR9) sample of the Baryonic Oscillation Spectroscopic Survey (BOSS). Wecombine this information with additional data from recent cosmicmicrowave background (CMB), supernova and baryon acoustic oscillationmeasurements. Our results show no significant evidence of deviationsfrom the standard flat Λ cold dark matter model, whose basicparameters can be specified by Ωm = 0.285 ±0.009, 100 Ωb = 4.59 ± 0.09, ns =0.961 ± 0.009, H0 = 69.4 ± 0.8 kms-1 Mpc-1 and σ8 = 0.80 ±0.02. The CMB+CMASS combination sets tight constraints on the curvatureof the Universe, with Ωk = -0.0043 ± 0.0049, andthe tensor-to-scalar amplitude ratio, for which we find r < 0.16 atthe 95 per cent confidence level (CL). These data show a clear signatureof a deviation from scale invariance also in the presence of tensormodes, with ns < 1 at the 99.7 per cent CL. We deriveconstraints on the fraction of massive neutrinos of fν< 0.049 (95 per cent CL), implying a limit of ∑mν< 0.51 eV. We find no signature of a deviation from a cosmologicalconstant from the combination of all data sets, with a constraint ofwDE = -1.033 ± 0.073 when this parameter is assumedtime-independent, and no evidence of a departure from this value when itis allowed to evolve as wDE(a) = w0 +wa(1 - a). The achieved accuracy on our cosmologicalconstraints is a clear demonstration of the constraining power ofcurrent cosmological observations.
We explore the benefits of using a passively evolving population ofgalaxies to measure the evolution of the rate of structure growthbetween z = 0.25 and 0.65 by combining data from the Sloan Digital SkySurvey (SDSS) I/II and SDSS-III surveys. The large-scale linear bias ofa population of dynamically passive galaxies, which we select from bothsurveys, is easily modelled. Knowing the bias evolution breaksdegeneracies inherent to other methodologies, and decreases theuncertainty in measurements of the rate of structure growth and thenormalization of the galaxy power spectrum by up to a factor of 2. If wetranslate our measurements into a constraint on σ8(z =0) assuming a concordance cosmological model and general relativity(GR), we find that using a bias model improves our uncertainty by afactor of nearly 1.5. Our results are consistent with a flat Λcold dark matter model and with GR.
We measure the Milky Way's rotation curve over the Galactocentric range4 kpc <~ R <~ 14 kpc from the first year of data from the ApachePoint Observatory Galactic Evolution Experiment. We model theline-of-sight velocities of 3365 stars in 14 fields with b = 0°between 30° <= l <= 210° out to distances of 10 kpc usingan axisymmetric kinematical model that includes a correction for theasymmetric drift of the warm tracer population (σ R ≈ 35 km s-1). We determine the local value of thecircular velocity to be Vc (R 0) = 218 ± 6km s-1 and find that the rotation curve isapproximately flat with a local derivative between -3.0 kms-1 kpc-1 and 0.4 kms-1 kpc-1. We also measure the Sun'sposition and velocity in the Galactocentric rest frame, finding thedistance to the Galactic center to be 8 kpc < R 0 < 9kpc, radial velocity V R, &sun; = -10 ± 1 kms-1, and rotational velocity V phi, &sun;= 242+10- 3 km s-1, ingood agreement with local measurements of the Sun's radial velocity andwith the observed proper motion of Sgr A*. We investigate varioussystematic uncertainties and find that these are limited to offsets atthe percent level, ~2 km s-1 in Vc .Marginalizing over all the systematics that we consider, we find thatVc (R 0) < 235 km s-1 at
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) usesa dedicated 300-fiber, narrow-band near-infrared (1.51-1.7 μm), highresolution (R~22,500) spectrograph to survey approximately 100,000 giantstars across the Milky Way. This three-year survey, in operation sincelate-summer 2011 as part of the Sloan Digital Sky Survey III (SDSS III),will revolutionize our understanding of the kinematical and chemicalenrichment histories of all Galactic stellar populations. We present theperformance of the instrument from its first year in operation. Theinstrument is housed in a separate building adjacent to the 2.5-m SDSStelescope and fed light via approximately 45-meter fiber runs from thetelescope. The instrument design includes numerous innovations includinga gang connector that allows simultaneous connection of all fibers witha single plug to a telescope cartridge that positions the fibers on thesky, numerous places in the fiber train in which focal ratio degradationhad to be minimized, a large mosaic-VPH (290 mm x 475 mmelliptically-shaped recorded area), an f/1.4 six-element refractivecamera featuring silicon and fused silica elements with diameters aslarge as 393 mm, three near-infrared detectors mounted in a 1 x 3 mosaicwith sub-pixel translation capability, and all of these componentshoused within a custom, LN2-cooled, stainless steel vacuum cryostat withdimensions 1.4-m x 2.3-m x 1.3-m.
The Near-Infrared Camera (NIRCam) on the James Webb Space Telescope(JWST) offers revolutionary gains in sensitivity throughout the 1-5μm region. NIRCam will enable great advances in all areas ofastrophysics, from the composition of objects in our own Kuiper Belt andthe physical properties of planets orbiting nearby stars to theformation of stars and the detection of the youngest galaxies in theUniverse. NIRCam also plays an important role in initial alignment ofJWST and the long term maintenance of its image quality. NIRCam ispresently undergoing instrument Integration and Test in preparation fordelivery to the JWST project. Key near-term milestones include thecompletion of cryogenic testing of the entire instrument; demonstrationof scientific and wavefront sensing performance requirements; testing ofreplacement H2RG detectors arrays; and an analysis of coronagraphicperformance in light of measured telescope wavefront characteristics.This paper summarizes the performance of NIRCam, the scientific andeducation/outreach goals of the science team, and some results of theon-going testing program.
The SDSS-DR9 Quasar Catalog presents photometric and spectroscopicproperties of 87,822 quasars observed by the SDSS-III/BOSS survey. Weprovide the catalog in the form of a fits file but also an ascii file.We also provide a supplemental list containing 949 quasars with exactlythe same format as the main catalog.(4 data files).
We describe the automated spectral classification, redshiftdetermination, and parameter measurement pipeline in use for the BaryonOscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky SurveyIII (SDSS-III) as of the survey's ninth data release (DR9), encompassing831,000 moderate-resolution optical spectra. We give a review of thealgorithms employed, and describe the changes to the pipeline that havebeen implemented for BOSS relative to previous SDSS-I/II versions,including new sets of stellar, galaxy, and quasar redshift templates.For the color-selected "CMASS" sample of massive galaxies at redshift0.4 <~ z <~ 0.8 targeted by BOSS for the purposes of large-scalecosmological measurements, the pipeline achieves an automated
We present the first application to density field reconstruction to agalaxy survey to undo the smoothing of the baryon acoustic oscillation(BAO) feature due to non-linear gravitational evolution and therebyimprove the precision of the distance measurements possible. We applythe reconstruction technique to the clustering of galaxies from theSloan Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy(LRG) sample, sharpening the BAO feature and achieving a 1.9 per centmeasurement of the distance to z = 0.35. We update the reconstructionalgorithm of Eisenstein et al. to account for the effects of surveygeometry as well as redshift-space distortions and validate it on 160LasDamas simulations. We demonstrate that reconstruction sharpens theBAO feature in the angle averaged galaxy correlation function, reducingthe non-linear smoothing scale Σnl from 8.1 to 4.4 Mpch-1. Reconstruction also significantly reduces the effects ofredshift-space distortions at the BAO scale, isotropizing thecorrelation function. This sharpened BAO feature yields an unbiaseddistance estimate (<0.2 per cent) and reduces the scatter from 3.3 to2.1 per cent. We demonstrate the robustness of these results to thevarious reconstruction parameters, including the smoothing scale, thegalaxy bias and the linear growth rate. Applying this reconstructionalgorithm to the SDSS LRG DR7 sample improves the significance of theBAO feature in these data from 3.3σ for the unreconstructedcorrelation function to 4.2σ after reconstruction. We estimate arelative distance scale DV/rs to z = 0.35 of 8.88± 0.17, where rs is the sound horizon andDV≡(DA2H-1)1/3 is a combination of the angular diameter distanceDA and Hubble parameter H. Assuming a sound horizon of 154.25Mpc, this translates into a distance measurement DV(z = 0.35)= 1.356 ± 0.025 Gpc. We find that reconstruction reduces thedistance error in the DR7 sample from 3.5 to 1.9 per cent, equivalent toa survey with three times the volume of SDSS.
We present results from fitting the baryon acoustic oscillation (BAO)signal in the correlation function obtained from the first applicationof density-field reconstruction to a galaxy redshift survey, namely theSloan Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy(LRG) catalogue. Reconstruction works to partially remove the effects ofnon-linear structure growth on the BAO by reconstructing the linearmatter density field from the observed galaxy density field using thecontinuity equation. We also introduce more careful approaches forderiving a suitable covariance matrix and fitting model for galaxycorrelation functions. Our covariance matrix technique guarantees smoothdiagonal and off-diagonal terms by fitting a modified Gaussiancovariance matrix to that calculated from mock catalogues. Our proposedfitting model is effective at removing broad-band effects such asredshift-space distortions, scale-dependent bias and any artefactsintroduced by assuming the wrong model cosmology. These all aid inobtaining a more accurate measurement of the acoustic scale and itserror. We validate these techniques on 160 mock catalogues derived fromthe LasDamas simulations in real and redshift space. We then apply thesetechniques to the DR7 LRG sample and find that the error on the acousticscale decreases from ˜3.5 per cent before reconstruction to˜1.9 per cent after reconstruction. We also see an increase in ourBAO detection confidence from ˜3σ to ˜4σ afterreconstruction with our confidence level in measuring the correctacoustic scale increasing from ˜3σ to ˜5σ. Usingthe mean of the acoustic scale probability distributions produced fromour fits, we find Dv/rs = 8.89 ± 0.31before reconstruction and 8.88 ± 0.17 after reconstruction.
We use the 2 per cent distance measurement from our reconstructed baryonacoustic oscillations (BAOs) signature using the Sloan Digital SkySurvey (SDSS) Data Release 7 (DR7) luminous red galaxies fromPadmanabhan et al. and Xu et al. combined with cosmic microwavebackground data from Wilkinson Microwave Anisotropy Probe (WMAP7) tomeasure parameters for various cosmological models. We find a 1.7 percent measurement of H0 = 69.8 ± 1.2 km s-1Mpc-1 and a 5.0 per cent measurement ofΩm=0.280±0.014 for a flat universe with a cosmologicalconstant. These measurements of H0 and Ωmare robust against a range of underlying models for the expansionhistory. We measure the dark energy equation of state parameter w =-0.97 ± 0.17, which is consistent with a cosmological constant.If curvature is allowed to vary, we find that the Universe is consistentwith a flat geometry (ΩK = -0.004 ± 0.005). Wealso use a combination of the 6 Degree Field Galaxy Survey BAO data,WiggleZ Dark Energy Survey data, Type Ia supernovae data and a localmeasurement of the Hubble constant to explore cosmological models withmore parameters. Finally, we explore the effect of varying the energydensity of relativistic particles on the measurement of H0.
We measure the acoustic scale from the angular power spectra of theSloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalogthat includes 872, 921 galaxies over ~10,000 deg2 between0.45 < z < 0.65. The extensive spectroscopic training set of theBaryon Oscillation Spectroscopic Survey luminous galaxies allows preciseestimates of the true redshift distributions of galaxies in our imagingcatalog. Utilizing the redshift distribution information, we buildtemplates and fit to the power spectra of the data, which are measuredin our companion paper, to derive the location of Baryon acousticoscillations (BAOs) while marginalizing over many free parameters toexclude nearly all of the non-BAO signal. We derive the ratio of theangular diameter distance to the sound horizon scale DA(z)/rs = 9.212+0.416- 0.404 at z= 0.54, and therefore DA (z) = 1411 ± 65 Mpc at z =0.54; the result is fairly independent of assumptions on the underlyingcosmology. Our measurement of angular diameter distance DA(z) is 1.4σ higher than what is expected for the concordanceΛCDM, in accordance to the trend of other spectroscopic BAOmeasurements for z >~ 0.35. We report constraints on cosmologicalparameters from our measurement in combination with the WMAP7 data andthe previous spectroscopic BAO measurements of SDSS and WiggleZ. Werefer to our companion papers (Ho et al. de Putter et al.) forinvestigations on information of the full power spectrum.
We present the BOSS Lyman-alpha (Lya) Forest Sample from SDSS DataRelease 9, comprising 54,468 quasar spectra with zqso > 2.15 suitablefor Lya forest analysis. This data set probes the intergalactic mediumwith absorption redshifts 2.0 < z_alpha < 5.7 over an area of 3275square degrees, and encompasses an approximate comoving volume of 20h^-3 Gpc^3. With each spectrum, we have included several productsdesigned to aid in Lya forest analysis: improved sky masks that flagpixels where data may be unreliable, corrections for known biases in thepipeline estimated noise, masks for the cores of damped Lya systems andcorrections for their wings, and estimates of the unabsorbed continua sothat the observed flux can be converted to a fractional transmission.The continua are derived using a principal component fit to the quasarspectrum redwards of restframe Lya (lambda > 1216 Ang), extrapolatedinto the forest region and normalized by a linear function to fit theexpected evolution of the Lya forest mean-flux. The estimated continuum