We explore the requirements for a Lyman-α forest survey designedto measure the angular diameter distance and Hubble parameter at2≲z≲4 using the standard ruler provided by baryonic acousticoscillations (BAO). The goal would be to obtain a high enough density ofsources to probe the three-dimensional density field on the scale of theBAO feature. A percent-level measurement in this redshift range canalmost double the Dark Energy Task Force figure of merit, relative tothe case with only a similar precision measurement at z˜1, if theUniverse is not assumed to be flat. This improvement is greater than theone obtained by doubling the size of the z˜1 survey, with Planckand a weak Sloan Digital Sky Survey-like z=0.3 BAO measurement assumedin each case. Galaxy BAO surveys at z˜1 may be able to make aneffective Lyα forest measurement simultaneously at minimal addedcost, because the required number density of quasars is relativelysmall. We discuss the constraining power as a function of area,magnitude limit (density of quasars), resolution, and signal-to-noise ofthe spectra. For example, a survey covering 2000 sq. deg. and achievingS/N=1.8 per Å at g=23 (˜40quasars per sq. deg.) with anR≳250 spectrograph is sufficient to measure both the radial and
This paper describes the Fifth Data Release (DR5) of the Sloan DigitalSky Survey (SDSS). DR5 includes all survey quality data taken through2005 June and represents the completion of the SDSS-I project (whosesuccessor, SDSS-II, will continue through mid-2008). It includesfive-band photometric data for 217 million objects selected over 8000deg2 and 1,048,960 spectra of galaxies, quasars, and starsselected from 5713 deg2 of that imaging data. These numbers
We have combined optical data from the 2dF-SDSS (Sloan Digital SkySurvey) LRG (Luminous Red Galaxy) and QSO (quasi-stellar object) (2SLAQ)redshift survey with radio measurements from the 1.4GHz VLA (Very LargeArray) FIRST (Faint Images of the Radio Sky at Twenty-cm) and NVSS (NRAOVLA Sky Survey) surveys to identify a volume-limited sample of 391 radiogalaxies at redshift 0.4 < z < 0.7. By determining an accurateradio luminosity function for luminous early-type galaxies in thisredshift range, we can investigate the cosmic evolution of theradio-galaxy population over a wide range in radio luminosity.The low-power radio galaxies in our LRG sample (those with 1.4GHz radioluminosities in the range 1024 to1025WHz-1, corresponding to Fanaroff-Riley I (FRI)radio galaxies in the local Universe) undergo significant cosmicevolution over the redshift range 0 < z < 0.7, consistent withpure luminosity evolution of the form (1 + z)k, where k = 2.0+/- 0.3. Our results appear to rule out (at the 6-7σ level) modelsin which low-power radio galaxies undergo no cosmic evolution. The mostpowerful radio galaxies in our sample (with radio luminosities above1026WHz-1) may undergo more rapid evolution overthe same redshift range.The evolution seen in the low-power radio-galaxy population implies thatthe total energy input into massive early-type galaxies from activegalactic nucleus (AGN) heating increases with redshift, and was at least50 per cent higher at z ~ 0.55 (the median redshift of the 2SLAQ LRGsample) than in the local universe.
We present a clustering analysis of luminous red galaxies (LRGs) usingnearly 9000 objects from the final, three-year catalogue of the 2dF-SDSSLRG and QSO (2SLAQ) Survey. We measure the redshift-space two-pointcorrelation function, ξ(s) and find that, at the mean LRG redshift ofshows the characteristic downturn at small scales(<~1h-1Mpc) expected from line-of-sight velocitydispersion. We fit a double power law to ξ(s) and measure anamplitude and slope of s0 =17.3+2.5-2.0h-1Mpc,γ = 1.03 +/-0.07 at small scales (s < 4.5h-1Mpc) and s0 =9.40 +/- 0.19h-1Mpc,γ = 2.02 +/- 0.07 at large scales(s > 4.5h-1Mpc). In the semiprojected correlationfunction, wp(σ), we find a simple power law withγ = 1.83 +/- 0.05 and r0 = 7.30 +/-0.34h-1Mpc fits the data in the range 0.4 < σ <50h-1Mpc, although there is evidence of a steeper power lawat smaller scales. A single power law also fits the deprojectedcorrelation function ξ(r), with a correlation length of r0= 7.45 +/- 0.35h-1Mpc and a power-law slope of γ = 1.72+/- 0.06 in the 0.4 < r < 50h-1Mpc range. But it is inthe LRG angular correlation function that the strongest evidence fornon-power-law features is found where a slope of γ = -2.17 +/-0.07 is seen at 1 < r < 10h-1Mpc with a flatter γ= -1.67 +/- 0.07 slope apparent at r <~ 1h-1Mpc scales.We use the simple power-law fit to the galaxy ξ(r), under theassumption of linear bias, to model the redshift-space distortions inthe 2D redshift-space correlation function, ξ(σ, π). We fitfor the LRG velocity dispersion, wz, the density parameter,Ωm and β(z), where β(z) =Ω0.6m/b and b is the linear bias parameter.We find values of wz =330kms-1,Ωm =0.10+0.35-0.10 and β = 0.40 +/- 0.05. The lowvalues for wz and β reflect the high bias of the LRGsample. These high-redshift results, which incorporate theAlcock-Paczynski effect and the effects of dynamical infall, start tobreak the degeneracy between Ωm and β found inlow-redshift galaxy surveys such as 2dFGRS. This degeneracy is furtherbroken by introducing an additional external constraint, which is thevalue β(z = 0.1) = 0.45 from 2dFGRS, and then considering theevolution of clustering from z ~ 0 to zLRG ~ 0.55. With thesecombined methods we find Ωm(z = 0) = 0.30 +/- 0.15 andβ(z = 0.55) = 0.45 +/- 0.05. Assuming these values, we find a valuefor b(z = 0.55) = 1.66 +/- 0.35. We show that this is consistent with asimple `high-peak' bias prescription which assumes that LRGs have aconstant comoving density and their clustering evolves purely undergravity.
We introduce a method to constrain general cosmological models usingBaryon Acoustic Oscillation (BAO) distance measurements from galaxysamples covering different redshift ranges, and apply this method toanalyse samples drawn from the Sloan Digital Sky Survey (SDSS) and 2dFGalaxy Redshift Survey (2dFGRS). BAOs are detected in the clustering ofthe combined 2dFGRS and SDSS main galaxy samples, and measure thedistance-redshift relation at z = 0.2. BAOs in the clustering of theSDSS luminous red galaxies measure the distance-redshift relation at z =0.35. The observed scales of the BAOs calculated from these samples andfrom the combined sample are jointly analysed using estimates of thecorrelated errors, to constrain the form of the distance measureDV(z) ≡ [(1 +z)2D2Acz/H(z)]1/3. HereDA is the angular diameter distance, and H(z) is the Hubbleparameter. This gives rs/DV(0.2) = 0.1980 +/-0.0058 and rs/DV(0.35) = 0.1094 +/- 0.0033(1σ errors), with a correlation coefficient of 0.39, wherers is the comoving sound horizon scale at recombination.Matching the BAOs to have the same measured scale at all redshifts thengives DV(0.35)/DV(0.2) = 1.812 +/- 0.060. Therecovered ratio is roughly consistent with that predicted by the higherredshift Supernova Legacy Survey (SNLS) supernova data for Λ colddark matter cosmologies, but does require slightly stronger cosmologicalacceleration at a low redshift. If we force the cosmological model to beflat with constant w, then we find Ωm = 0.249 +/- 0.018and w = -1.004 +/- 0.089 after combining with the SNLS data, andincluding the WMAP measurement of the apparent acoustic horizon angle inthe cosmic microwave background.
We identify a population of 640 obscured and 839 unobscured AGNs atredshifts 0.72 NOAO Deep Wide-Field Survey (NDWFS) region inBoötes. We select AGNs on the basis of Spitzer IRAC colors obtainedby the IRAC Shallow Survey. Redshifts are obtained from opticalspectroscopy or photometric redshift estimators. We classify theIR-selected AGNs as IRAGN 1 (unobscured) and IRAGN 2 (obscured) using asimple criterion based on the observed optical to mid-IR color, with aselection boundary of R-[4.5]=6.1, where R and [4.5] are the Vegamagnitudes in the R and IRAC 4.5 μm bands, respectively. We verifythis selection using X-ray stacking analyses with data from the ChandraXBoötes survey, as well as optical photometry from NDWFS andspectroscopy from MMT/AGES. We show that (1) these sources are indeedAGNs, and (2) the optical/IR color selection separates obscured sources(with average NH~3×1022 cm-2obtained from X-ray hardness ratios, and optical colors and morphologiestypical of galaxies) and unobscured sources (with no X-ray absorption,
We report follow-up observations of two gravitational lens candidatesidentified in the Sloan Digital Sky Survey (SDSS) data set. We haveconfirmed that SDSS J102111.02+491330.4 is a previously unknowngravitationally lensed quasar. This lens system exhibits two images of az=1.72 quasar, with an image separation of 1.14"+/-0.04". Optical andnear-IR imaging of the system reveals the presence of the lensing galaxybetween the two quasar images. Observations of SDSS J112012.12+671116.0indicate that it is more likely a binary quasar than a gravitationallens. This system has two quasars at a redshift of z=1.49, with anangular separation of 1.49"+/-0.02". However, the two quasars havemarkedly different spectral energy distributions, and no lens galaxy isapparent in optical and near-IR images of this system. We also present alist of 31 SDSS lens candidates that follow-up observations haveconfirmed are not gravitational lenses.Observations reported here were obtained at the MMT Observatory, a jointfacility of the University of Arizona and the Smithsonian Institution.
We report on i-band snapshot observations of 157 Sloan Digital SkySurvey quasars at 4.0-3.8 (3 σ), assuming a break in the quasar luminosityfunction at M*1450~-24.5. This constraint isconsiderably stronger than the limit of β>-4.63 obtained fromthe absence of lensing in four z>5.7 quasars. Such constraints areimportant to our understanding of the true space density ofhigh-redshift quasars and the ionization state of the early universe.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 NAS5-26555. These observations are associated with program9472.
A sample of white dwarfs is selected from the Sloan Digital Sky Survey(SDSS) Data Release 3 using their reduced proper motions, based onimproved proper motions from combined SDSS and USNO-B data. NumerousSDSS and follow-up spectra (Kilic and coworkers) are used to quantifycompleteness and contamination of the sample; kinematics models are usedto understand and correct for velocity-dependent selection biases. Aluminosity function is constructed covering the range7bol<16, and its sensitivity to various assumptionsand selection limits is discussed. The white dwarf luminosity functionbased on 6000 stars is remarkably smooth and rises nearly monotonicallyto Mbol=15.3. It then drops abruptly, although the smallnumber of low-luminosity stars in the sample and their unknownatmospheric composition prevent quantitative conclusions about thisdecline. Stars are identified that may have high tangential velocities,and a preliminary luminosity function is constructed for them.
This paper describes the Fourth Data Release of the Sloan Digital SkySurvey (SDSS), including all survey-quality data taken through 2004June. The data release includes five-band photometric data for 180million objects selected over 6670 deg2 and 673,280 spectraof galaxies, quasars, and stars selected from 4783 deg2 ofthose imaging data using the standard SDSS target selection algorithms.
Using a sample of nearly 20,000 massive early-type galaxies selectedfrom the Sloan Digital Sky Survey, we study the color-magnitude relationfor the most luminous (L>~2.2L*) field galaxies in theredshift range 0.1
We describe the serendipitous discovery in the spectroscopic data of theSloan Digital Sky Survey of a starlike object, SDSS J103913.70+533029.7,at a heliocentric radial velocity of +1012 km s-1. Itsproximity in position and velocity to the spiral galaxy NGC 3310suggests an association with the galaxy. At this distance, SDSSJ103913.70+533029.7 has the luminosity of a super star cluster and aprojected distance of 17 kpc from NGC 3310. Its spectroscopic andphotometric properties imply a mass of >106Msolar and an age close to that of the tidal shells seenaround NGC 3310, suggesting that it formed in the event that formed theshells.
We present a spectroscopic sample of 747 detached close binary systemsfrom the Sloan Digital Sky Survey (SDSS) Fourth Data Release. Themajority of these binaries consist of a white dwarf primary and alow-mass secondary (typically M dwarf) companion. We have determined thetemperature and gravity for 496 of the white dwarf primaries and thespectral type and magnetic activity properties for 661 of the low-masssecondaries. We have estimated the distances for each of the whitedwarf-main-sequence star binaries and use white dwarf evolutionary gridsto establish the age of each binary system from the white dwarf coolingtimes. With respect to a spectroscopically identified sample of ~8000isolated M dwarf stars in the SDSS, the M dwarf secondaries showenhanced activity with a higher active fraction at a given spectraltype. The white dwarf temperatures and gravities are similar to thedistribution of ~1900 DA white dwarfs from the SDSS. The ages of thebinaries in this study range from ~0.5 Myr to nearly 3 Gyr (average age~0.20 Gyr).
We report the discovery of eleven new ZZ Cetis using telescopes at OPD(Observatório do Pico dos Dias/LNA) in Brazil, the 4.1 m SOAR(Southern Astrophysical Research) telescope at Cerro Pachon, Chile, andthe 2.1 m Otto Struve telescope at McDonald observatory. The candidateswere selected from the SDSS (Sloan Digital Sky Survey) and SPY (ESO SNIa progenitor survey), based on their Teff obtained fromoptical spectra fitting. This selection criterion yields the highest
Using high-resolution cosmological simulations, we study hydrogen andhelium gravitational cooling radiation from gas accretion by younggalaxies. We focus on the He II cooling lines, which arise from gas witha different temperature history (Tmax~105 K) thanH I line-emitting gas. We examine whether three major atomic coolinglines, H I λ1216, He II λ1640, and He II λ304, areobservable, finding that Lyα and He II λ1640 coolingemission at z=2-3 are potentially detectable with deep narrowband(R>100) imaging and/or spectroscopy from the ground. While theexpected strength of H I λ1216 cooling emission depends stronglyon the treatment of the self-shielded phase of the IGM in thesimulations, our predictions for the He II λ1640 line are morerobust, because the He II emissivity is negligible belowT~104.5 K and less sensitive to the UV background. AlthoughHe II λ1640 cooling emission is fainter than Lyα by atleast a factor of 10 and, unlike Lyα, might not be resolvedspatially with current observational facilities, it is more suitable tostudy gas accretion in the galaxy formation process because it isoptically thin and less contaminated by the recombination lines fromstar-forming galaxies. The He II λ1640 line can be used todistinguish among mechanisms for powering the so-called Lyαblobs-including gravitational cooling radiation, photoionization bystellar populations, and starburst-driven superwinds-because (1) He IIλ1640 emission is limited to very low metallicity[log(Z/Zsolar)<~-5.3] and Population III stars and (2) theblob's kinematics are probed unambiguously through the He II line width,which for cooling radiation is narrower (σ<400 kms-1) than typical wind speeds.
We present Sloan Digital Sky Survey (SDSS) photometry and spectroscopyin the fields of 27 gamma-ray bursts observed by Swift, including burstslocalized by Swift, HETE-2, and INTEGRAL, after 2004 December. Afterthis bulk release, we plan to provide individual releases of similardata shortly after the localization of future bursts falling in the SDSSsurvey area. These data provide a solid basis for the astrometric andphotometric calibration of follow-up afterglow searches and monitoring.Furthermore, the images provided with this release will allow observersto find transient objects up to a magnitude fainter than is possiblewith Digitized Sky Survey images.
In this paper we present the first results of a deep spectroscopicsurvey of faint quasars in the Sloan Digital Sky Survey (SDSS) SouthernSurvey, a deep survey carried out by repeatedly imaging a 270deg2 area. Quasar candidates were selected from the deep datawith good completeness over 02, contains 414 quasars, and
We present the small-scale (0.01 Mpc-1 Mpc)projected correlation function wp(rp) andreal-space correlation function ξ(r) of 24,520 luminous early-typegalaxies from the Sloan Digital Sky Survey (SDSS) Luminous Red Galaxy(LRG) sample (0.16-2 power law over more than 4 orders of magnitudein separation r. This result is too steep at small scales to beexplained in current versions of the halo model for galaxy clustering.We infer an LRG-LRG merger rate of <~0.6×104Gyr-1 Gpc-3 for this sample. This result suggeststhat the LRG-LRG mergers are not the main mode of mass growth for LRGsat z<0.36.
We present a spectroscopic survey using the MMT Hectospec fiberspectrograph of 24 μm sources selected with the Spitzer SpaceTelescope in the Spitzer First Look Survey. We report 1296 new redshiftsfor 24 μm sources, including 599 with fν(24μm)>=1 mJy. Combined with 291 additional redshifts for sourcesfrom the Sloan Digital Sky Survey (SDSS), our observing program was
We investigate the relationship between the colors, luminosities, andenvironments of galaxies in the Sloan Digital Sky Survey spectroscopicsample, using environmental measurements on scales ranging from 0.2 to 6h-1 Mpc. We find that (1) the relationship between color andenvironment persists even to the lowest luminosities we probe(Mr-5log10h~-14) (2) at luminosities and colors for which thegalaxy correlation function has a large amplitude, it also has a steepslope; and (3) in regions of a given overdensity on small scales (1h-1 Mpc), the overdensity on large scales (6 h-1Mpc) does not appear to relate to the recent star formation history ofthe galaxies. Of these results, the last has the most immediateapplication to galaxy formation theory. In particular, it lends supportto the notion that a galaxy's properties are related only to the mass ofits host dark matter halo, and not to the larger scale environment.Based on observations obtained with the Sloan Digital Sky Survey.