We examine a sample of low-redshift (10 h super(-1) Mpc < d< 150 h super(-1) Mpc) field galaxies including galaxies with luminosities as low as M sub(r) - 5 log h 6 -12.5, selected from the Sloan ...Digital Sky Survey Data Release 2 (SDSS DR2). The sample is unique in containing galaxies of extremely low luminosities in a wide range of environments, selected with uniform and well-understood criteria. We present the luminosity function, as well as the broadband properties, of low-luminosity galaxies in this sample. A Schechter function is an insufficient parameterization of the r-band luminosity function; there is an upturn in the slope for M sub(r) - 5 log h > -18. The resulting slope at low luminosities in this sample is a sub(2) 6 -1.3. However, we almost certainly miss a large number of galaxies at very low luminosities due to low surface brightness selection effects, and we estimate that the true low-luminosity slope may be as steep as or steeper than a sub(2) 6 -1.5. The results here are consistent with previous SDSS results and, in the g band, roughly consistent with the results of the Two Degree Field Galaxy Redshift Survey. Extremely low luminosity galaxies are predominantly low surface brightness, exponential disks, the majority of which are red.
Abstract
We conducted a deep spectroscopic survey, named SSA22-HIT, in the SSA22 field with the DEep Imaging MultiObject Spectrograph (DEIMOS) on the Keck telescope, designed to tomographically map ...high-
z
H
i
gas through analysis of Ly
α
absorption in background galaxies’ spectra. In total, 198 galaxies were spectroscopically confirmed at 2.5 <
z
< 6 with a few low-
z
exceptions in the 26 × 15 arcmin
2
area, of which 148 were newly determined in this study. Our redshift measurements were merged with previously confirmed redshifts available in the 34 × 27 arcmin
2
area of the SSA22 field. This compiled catalog containing 730 galaxies of various types at
z
> 2 is useful for various applications, and it is made publicly available. Our SSA22-HIT survey has increased by approximately twice the number of spectroscopic redshifts of sources at
z
> 3.2 in the observed field. From a comparison with publicly available redshift catalogs, we show that our compiled redshift catalog in the SSA22 field is comparable to those among major extragalactic survey fields in terms of a combination of wide area and high surface number density of objects at
z
> 2. About 40% of the spectroscopically confirmed objects in SSA22-HIT show reasonable quality of spectra in the wavelengths shorter than Ly
α
when a sufficient amount of smoothing is adopted. Our data set enables us to make the H
i
tomographic map at
z
≳ 3, which we present in a parallel study.
We present a catalog of 25 definite and 11 probable strong galaxy-galaxy gravitational lens systems with lens redshifts 0.4 z 0.7, discovered spectroscopically by the presence of higher-redshift ...emission lines within the Baryon Oscillation Spectroscopic Survey (BOSS) of luminous galaxies, and confirmed with high-resolution Hubble Space Telescope (HST) images of 44 candidates. Our survey extends the methodology of the Sloan Lens Advanced Camera for Surveys survey (SLACS) to higher redshift. We describe the details of the BOSS spectroscopic candidate detections, our HST ACS image processing and analysis methods, and our strong gravitational lens modeling procedure. We report BOSS spectroscopic parameters and ACS photometric parameters for all candidates, and mass-distribution parameters for the best-fit singular isothermal ellipsoid models of definite lenses. Our sample to date was selected using only the first six months of BOSS survey-quality spectroscopic data. The full five-year BOSS database should produce a sample of several hundred strong galaxy-galaxy lenses and in combination with SLACS lenses at lower redshift, strongly constrain the redshift evolution of the structure of elliptical, bulge-dominated galaxies as a function of luminosity, stellar mass, and rest-frame color, thereby providing a powerful test for competing theories of galaxy formation and evolution.
Here we present the New York University Value-Added Galaxy Catalog (NYU-VAGC), a catalog of local galaxies (mostly below z 0.3) based on a set of publicly released surveys matched to the Sloan ...Digital Sky Survey (SDSS) Data Release 2. The photometric catalog consists of 693,319 galaxies, QSOs, and stars; 343,568 of these have redshift determinations, mostly from the SDSS. Excluding areas masked by bright stars, the photometric sample covers 3514 deg2, and the spectroscopic sample covers 2627 deg2 (with about 85% completeness). Earlier, proprietary versions of this catalog have formed the basis of many SDSS investigations of the power spectrum, correlation function, and luminosity function of galaxies. Future releases will follow future public releases of the SDSS. The catalog includes matches to the Two Micron All Sky Survey Point Source Catalog and Extended Source Catalog, the IRAS Point Source Catalog Redshift Survey, the Two-Degree Field Galaxy Redshift Survey, the Third Reference Catalogue of Bright Galaxies, and the Faint Images of the Radio Sky at Twenty cm survey. We calculate and compile derived quantities from the images and spectra of the galaxies in the catalogs (for example, K-corrections and structural parameters for the galaxies). The SDSS catalog presented here is photometrically calibrated in a more consistent way than that distributed by the SDSS Data Release 2 Archive Servers and is thus more appropriate for large-scale structure statistics, reducing systematic calibration errors across the sky from ~2% to ~1%. We include an explicit description of the geometry of the catalog, including all imaging and targeting information as a function of sky position. Finally, we have performed eyeball quality checks on a large number of objects in the catalog in order to flag errors (such as errors in deblending). This catalog is complementary to the SDSS Archive Servers in that NYU-VAGC's calibration, geometric description, and conveniently small size are specifically designed for studying galaxy properties and large-scale structure statistics using the SDSS spectroscopic catalog.
We present a measurement of baryon acoustic oscillations (BAO) in the cross-correlation of quasars with the Lyα-forest flux transmission at a mean redshift of z = 2.40. The measurement uses the ...complete Sloan Digital Sky Survey (SDSS-III) data sample: 168 889 forests and 234 367 quasars from the SDSS data release DR12. In addition to the statistical improvement on our previous study using DR11, we have implemented numerous improvements at the analysis level enabling a more accurate measurement of this cross-correlation. We have also developed the first simulations of the cross-correlation that allow us to test different aspects of our data analysis and to search for potential systematic errors in the determination of the BAO peak position. We measure the two ratios DH(z = 2.40) /rd = 9.01 ± 0.36 and DM(z = 2.40) /rd = 35.7 ± 1.7, where the errors include marginalization over the non-linear velocity of quasars and the cross-correlation of metals and quasars, among other effects. These results are within 1.8σ of the prediction of the flat-ΛCDM model describing the observed cosmic microwave background anisotropies. We combine this study with the Lyα-forest auto-correlation function, yielding DH(z = 2.40) /rd = 8.94 ± 0.22 and DM(z = 2.40) /rd = 36.6 ± 1.2, within 2.3σ of the same flat-ΛCDM model.
We explore the cosmological implications of the clustering wedges, ξ⊥(s) and ξ(s), of the CMASS Data Release 9 sample of the Sloan Digital Sky Survey III (SDSS-III) Baryon Oscillation Spectroscopic ...Survey. These clustering wedges are defined by averaging the full two-dimensional correlation function, ξ(μ, s), over the ranges 0 < μ < 0.5 and 0.5 < μ < 1, respectively. These measurements allow us to constrain the parameter combinations D
A(z)/r
s(z
d) = 9.03 ± 0.21 and cz/(r
s(z
d)H(z)) = 12.14 ± 0.43 at the mean redshift of the sample, z = 0.57. We combine the information from the clustering wedges with recent measurements of cosmic microwave background (CMB), baryon acoustic oscillations and Type Ia supernovae to obtain constraints on the cosmological parameters of the standard Λ cold dark matter (ΛCDM) model and a number of potential extensions. The information encoded in the clustering wedges is most useful when the dark energy equation of state is allowed to deviate from its standard ΛCDM value. The combination of all data sets shows no evidence of a deviation from a constant dark energy equation of state, in which case we find w
DE = −1.013 ± 0.064, in complete agreement with a cosmological constant. We explore potential deviations from general relativity (GR) by constraining the growth rate f(z) = d ln D(a)/d ln a, in which case the combination of the CMASS clustering wedges with CMB data implies f(z = 0.57) = 0.719−0.096
+0.092, in accordance with the predictions of GR. Our results clearly illustrate the additional constraining power of anisotropic clustering measurements with respect to that of angle-averaged quantities.
Abstract
The introduction of deep wide-field surveys in recent years and the adoption of machine-learning techniques have led to the discoveries of
(
10
4
)
strong gravitational lensing systems and ...candidates. However, the discovery of multiply-lensed transients remains a rarity. Lensed transients and especially lensed supernovae are invaluable tools to cosmology because they allow us to constrain cosmological parameters via lens modeling and the measurements of their time delays. In this paper, we develop a pipeline to perform a targeted lensed transient search. We apply this pipeline to 5807 strong lenses and candidates, which were identified in the literature, in the DESI Legacy Imaging Surveys Data Release 9 (DR9) footprint. For each system, we analyze every exposure in all of the observed bands (DECam
g
,
r
, and
z
). Our pipeline finds, groups, and ranks detections that are in sufficient proximity temporally and spatially. After the first round of inspection, for promising candidate systems, we further examine the newly available DR10 data (with additional
i
and
Y
bands). Here we present our targeted lensed supernova search pipeline and seven new lensed supernova candidates, including a very likely lensed supernova—probably a Type Ia—in a system with an Einstein radius of ∼1.″5.
Abstract
We measure the quasar two-point correlation function over the redshift range 2.2 < z < 2.8 using data from the Baryon Oscillation Spectroscopic Survey. We use a homogeneous subset of the ...data consisting of 27 129 quasars with spectroscopic redshifts - by far the largest such sample used for clustering measurements at these redshifts to date. The sample covers 3600 deg2, corresponding to a comoving volume of 9.7 (h
−1 Gpc)3 assuming a fiducial Λ cold dark matter cosmology, and it has a median absolute i-band magnitude of −26, k-corrected to z= 2. After accounting for redshift errors we find that the redshift-space correlation function is fitted well by a power law of slope −2 and amplitude s
0 = (9.7 ± 0.5) h
−1 Mpc over the range 3 < s < 25 h
−1 Mpc. The projected correlation function, which integrates out the effects of peculiar velocities and redshift errors, is fitted well by a power law of slope −1 and r
0 = (8.4 ± 0.6) h
−1 Mpc over the range 4 < R < 16 h
−1 Mpc. There is no evidence for strong luminosity or redshift dependence to the clustering amplitude, in part because of the limited dynamic range in our sample. Our results are consistent with, but more precise than, previous measurements at similar redshifts. Our measurement of the quasar clustering amplitude implies a bias factor of b ≃ 3.5 for our quasar sample. We compare the data to models to constrain the manner in which quasars occupy dark matter haloes at z∼ 2.4 and infer that such quasars inhabit haloes with a characteristic mass of 〈M〉≃ 1012
h
−1 M⊙ with a duty cycle for the quasar activity of 1 per cent.
We report on the small-scale (0.5 < r < 40 h
−1 Mpc) clustering of 78 895 massive (M
* ∼ 1011.3 M) galaxies at 0.2 < z < 0.4 from the first two years 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 the galaxies 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 the errors using mock catalogues. These galaxies lie in massive haloes, with a mean halo mass of 5.2 × 1013 h
−1 M, a large-scale bias of ∼2.0 and a satellite fraction of 12 ± 2 per cent. Thus, these galaxies occupy haloes with average masses in between those of the higher redshift BOSS CMASS sample and the original SDSS I/II luminous red galaxy sample.
Stars that escape globular clusters form tidal tails that are predominantly shaped by the global distribution of mass in the Galaxy, but also preserve a historical record of small-scale ...perturbations. Using deep grz photometry from DECaLS, we present highly probable members of the tidal tails associated with the evaporating globular cluster Palomar 5. These data yield the cleanest view of a stellar stream beyond 20 kpc and reveal: (1) a wide, low surface-brightness extension of the leading tail; (2) significant density variations along the stream; and (3) sharp changes in the direction of both the leading and the trailing tail. In the fiducial Milky Way model, a rotating bar perturbs the Palomar 5 tails and can produce streams with similar width and density profiles to those observed. However, the deviations of the stream track in this simple model do not match those observed in the Palomar 5 trailing tail, indicating the need for an additional source of perturbation. These discoveries open up the possibility of measuring the population of perturbers in the Milky Way, including dark-matter subhalos, with an ensemble of stellar streams and deep photometry alone.
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