We present optical spectroscopy of galaxies in clusters detected through the Sunyaev-Zel'dovich (SZ) effect with the South Pole Telescope (SPT). We report our own measurements of 61 spectroscopic ...cluster redshifts, and 48 velocity dispersions each calculated with more than 15 member galaxies. This catalog also includes 19 dispersions of SPT-observed clusters previously reported in the literature. The majority of the clusters in this paper are SPT-discovered; of these, most have been previously reported in other SPT cluster catalogs, and five are reported here as SPT discoveries for the first time. By performing a resampling analysis of galaxy velocities, we find that unbiased velocity dispersions can be obtained from a relatively small number of member galaxies (lap30), but with increased systematic scatter. We use this analysis to determine statistical confidence intervals that include the effect of membership selection.We fit scaling relations between the observed cluster velocity dispersions and mass estimates from SZ and X-ray observables. In both cases, the results are consistent with the scaling relation between velocity dispersion and mass expected from dark-matter simulations. We measure a ~30% log-normal scatter in dispersion at fixed mass, and a ~10% offset in the normalization of the dispersion-mass relation when compared to the expectation from simulations, which is within the expected level of systematic uncertainty.
We extend previous measurements of cosmic infrared background (CIB) fluctuations to <, ~1degrees using new data from the Spitzer Extended Deep Survey. Two fields with depths of Asymptotically = to12 ...hr pixel super(-1) over three epochs are analyzed at 3.6 and 4.5 mu m. Maps of the fields were assembled using a self-calibration method uniquely suitable for probing faint diffuse backgrounds. Resolved sources were removed from the maps to a magnitude limit of mag sub(AB) Asymptotically = to 25, as indicated by the level of the remaining shot noise. The maps were then Fourier transformed and their power spectra were evaluated. Instrumental noise was estimated from the time-differenced data, and subtracting this isolates the spatial fluctuations of the actual sky. The power spectra of the source-subtracted fields remain identical (within the observational uncertainties) for the three epochs indicating that zodiacal light contributes negligibly to the fluctuations. Comparing to 8 mu m power spectra shows that Galactic cirrus cannot account for the fluctuations. The signal appears isotropically distributed on the sky as required for an extragalactic origin. The CIB fluctuations continue to diverge to > 10 times those of known galaxy populations on angular scales out to <, ~ 10degrees. The low shot-noise levels remaining in the diffuse maps indicate that the large-scale fluctuations arise from the spatial clustering of faint sources well below the confusion noise. The spatial spectrum of these fluctuations is in reasonable agreement with an origin in populations clustered according to the standard cosmological model ( Delta CDM) at epochs coinciding with the first stars era.
ABSTRACT We present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, ...utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster-based on the UV and IR continuum luminosity, as well as the O iiλλ3726,3729 emission line luminosity in cases where spectroscopy is available-and find seven systems with SFR > 100 M yr−1. We find that the BCG SFR exceeds 10 M yr−1 in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ∼1%-5% at z ∼ 0 from the literature. At z 1, this fraction increases to %, implying a steady decrease in the BCG SFR over the past ∼9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z 0.6, the correlation between the cluster central entropy and BCG star formation-which is well established at z ∼ 0-is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ∼50-60 kpc. The high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy-galaxy interactions to ICM cooling.
We present the multiwavelength--ultraviolet to mid-infrared-catalog of the UKIRT Infrared Deep Sky Survey (UKIDSS) Ultra-Deep Survey field observed as part of the Cosmic Assembly Near-infrared Deep ...Extragalactic Legacy Survey (CANDELS). Based on publicly available data, the catalog includes the CANDELS data from the Hubble Space Telescope (near-infrared WFC3 F125W and F160W data and visible ACS F606W and F814W data); u-band data from CFHT/Megacam; B, V, R sub(c), i', and z' band data from Subaru/Suprime-Cam; Y and K sub(s) band data from VLT/HAWK-I; J, H, and K band data from UKIDSS (Data Release 8); and Spitzer/IRAC data (3.6, 4.5 mu m from SEDS; 5.8 and 8.0 mu m from SpUDS). The present catalog is F160W-selected and contains 35, 932 sources over an area of 201.7 arcmin super(2) and includes radio- and X-ray-detected sources and spectroscopic redshifts available for 210 sources.
We present a 0.4-8 m multi-wavelength photometric catalog in the Extended Groth Strip (EGS) field. This catalog is built on the Hubble Space Telescope (HST) WFC3 and ACS data from the Cosmic Assembly ...Near-infrared Deep Extragalactic Legacy Survey (CANDELS), and it incorporates the existing HST data from the All-wavelength Extended Groth strip International Survey (AEGIS) and the 3D-HST program. The catalog is based on detections in the F160W band reaching a depth of F160W = 26.62 AB (90% completeness, point sources). It includes the photometry for 41,457 objects over an area of arcmin2 in the following bands: HST/ACS F606W and F814W; HST WFC3 F125W, F140W, and F160W; Canada-France-Hawaii Telescope (CFHT)/Megacam u*, , , and CFHT/WIRCAM J, H, and KS; Mayall/NEWFIRM J1, J2, J3, H1, H2, and K; Spitzer IRAC 3.6, 4.5, 5.8, and 8.0 m. We are also releasing value-added catalogs that provide robust photometric redshifts and stellar mass measurements. The catalogs are publicly available through the CANDELS repository.
We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 mu m imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and ...are not seen in existing radio to far-infrared catalogs. At 1".5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by l"-3", consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 x 10 super(13) L sub(middot in circle) and star formation surface density of 4200 M sub(middot in circle) yr super(-1) kpc super(-2). We find magnification factors of 5 to 22, with lens Einstein radii of 1".1-2".0 and Einstein enclosed masses of 1.6-7.2 x 10 super(11) M sub(middot in circle). These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources.
We report deep ALMA observations complemented by associated Hubble Space Telescope (HST) imaging for a luminous (m sub(UV) = 25) galaxy, "Himiko," at a redshift of z = 6.595. Our ALMA observations ...probe an order of magnitude deeper than previous IRAM observations, yet fail to detect a 1.2 mm dust continuum, indicating a flux of <52 mu Jy, which is comparable to or weaker than that of local dwarf irregulars with much lower star formation rates. Our HST images provide unique insight into the morphology of this remarkable source, highlighting an extremely blue core of activity and two less extreme associated clumps. Himiko is undergoing a triple major merger event whose extensive ionized nebula of Ly alpha emitting gas, discovered in our earlier work with Subaru, is powered by star formation and the dense circumgalactic gas. We are likely witnessing an early massive galaxy during a key period of its mass assembly close to the end of the reionization era.
We present the results of the ground- and space-based optical and near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with the Sunyaev-Zel'dovich (SZ) effect in the 720 deg ...super(2) of the South Pole Telescope (SPT) survey completed in the 2008 and 2009 observing seasons. We use the optical/NIR data to establish whether each candidate is associated with an overdensity of galaxies and to estimate the cluster redshift. Most photometric redshifts are derived through a combination of three different cluster redshift estimators using red-sequence galaxies, resulting in an accuracy of Deltaz/(1 + z) - 0.017, determined through comparison with a subsample of 57 clusters for which we have spectroscopic redshifts. We successfully measure redshifts for 158 systems and present redshift lower limits for the remaining candidates. The redshift distribution of the confirmed clusters extends to z = 1.35 with a median of z sub(med) = 0.57. Approximately 18% of the sample with measured redshifts lies at z > 0.8. We estimate a lower limit to the purity of this SPT SZ-selected sample by assuming that all unconfirmed clusters are noise fluctuations in the SPT data. We show that the cumulative purity at detection significance xi > 5(xi > 4.5) is > or =, slanted95% (> or =, slanted70%). We present the red brightest cluster galaxy (rBCG) positions for the sample and examine the offsets between the SPT candidate position and the rBCG. The radial distribution of offsets is similar to that seen in X-ray-selected cluster samples, providing no evidence that SZ-selected cluster samples include a different fraction of recent mergers from X-ray-selected cluster samples.
The Extended Groth Strip (EGS) is one of the premier fields for extragalactic deep surveys. Deep observations of the EGS with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope cover an ...area of 0.38 deg super(2) to a 50% completeness limit of 1.5 muJy at 3.6 mum. The catalog comprises 57,434 objects detected at 3.6 mum, with 84%, 28%, and 24% also detected at 4.5, 5.8, and 8.0 mum, respectively. Number counts are consistent with results from other Spitzer surveys. Color distributions show that the EGS IRAC sources comprise a mixture of populations: low- redshift star-forming galaxies, quiescent galaxies dominated by stellar emission at a range of redshifts, and high-redshift galaxies and AGNs.
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