2,710 research outputs found
The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups
We present a public catalog of galaxy groups constructed from the spectroscopic sample of galaxies in the fourth data release from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Galaxy Redshift Survey, including the Extended Groth Strip (EGS). The catalog contains 1165 groups with two or more members in the EGS over the redshift range 0 0.6 in the rest of DEEP2. Twenty-five percent of EGS galaxies and fourteen percent of high-z DEEP2 galaxies are assigned to galaxy groups. The groups were detected using the Voronoi-Delaunay method (VDM) after it has been optimized on mock DEEP2 catalogs following similar methods to those employed in Gerke et al. In the optimization effort, we have taken particular care to ensure that the mock catalogs resemble the data as closely as possible, and we have fine-tuned our methods separately on mocks constructed for the EGS and the rest of DEEP2. We have also probed the effect of the assumed cosmology on our inferred group-finding efficiency by performing our optimization on three different mock catalogs with different background cosmologies, finding large differences in the group-finding success we can achieve for these different mocks. Using the mock catalog whose background cosmology is most consistent with current data, we estimate that the DEEP2 group catalog is 72% complete and 61% pure (74% and 67% for the EGS) and that the group finder correctly classifies 70% of galaxies that truly belong to groups, with an additional 46% of interloper galaxies contaminating the catalog (66% and 43% for the EGS). We also confirm that the VDM catalog reconstructs the abundance of galaxy groups with velocity dispersions above ~300 km s^(–1) to an accuracy better than the sample variance, and this successful reconstruction is not strongly dependent on cosmology. This makes the DEEP2 group catalog a promising probe of the growth of cosmic structure that can potentially be used for cosmological tests
Optimal linear reconstruction of dark matter from halo catalogs
We derive the weight function w(M) to apply to dark-matter halos that
minimizes the stochasticity between the weighted halo distribution and its
underlying mass density field. The optimal w(M) depends on the range of masses
being used in the estimator. In N-body simulations, the Poisson estimator is up
to 15 times noisier than the optimal. Implementation of the optimal weight
yields significantly lower stochasticity than weighting halos by their mass,
bias or equal. Optimal weighting could make cosmological tests based on the
matter power spectrum or cross-correlations much more powerful and/or
cost-effective. A volume-limited measurement of the mass power spectrum at
k=0.2h/Mpc over the entire z<1 universe could ideally be done using only 6
million redshifts of halos with mass M>6\times10^{13}h^{-1}M_\odot
(1\times10^{13}) at z=0 (z=1); this is 5 times fewer than the Poisson model
predicts. Using halo occupancy distributions (HOD) we find that
uniformly-weighted catalogs of luminous red galaxies require >3 times more
redshifts than an optimally-weighted halo catalog to reconstruct the mass to
the same accuracy. While the mean HODs of galaxies above a threshold luminosity
are similar to the optimal w(M), the stochasticity of the halo occupation
degrades the mass estimator. Blue or emission-line galaxies are about 100 times
less efficient at reconstructing mass than an optimal weighting scheme. This
suggests an efficient observational approach of identifying and weighting halos
with a deep photo-z survey before conducting a spectroscopic survey. The
optimal w(M) and mass-estimator stochasticity predicted by the standard halo
model for M>10^{12}h^{-1}M_\odot are in reasonable agreement with our
measurements, with the important exceptions that the halos must be assumed to
be linearly biased samples of a "halo field" that is distinct from the mass
field. (Abridged)Comment: Added Figure 3 to show the scatter between the weighted halo field vs
the mass field, Accepted for publication in MNRA
Galaxy Cluster Mass Estimation from Stacked Spectroscopic Analysis
We use simulated galaxy surveys to study: i) how galaxy membership in
redMaPPer clusters maps to the underlying halo population, and ii) the accuracy
of a mean dynamical cluster mass, , derived from stacked
pairwise spectroscopy of clusters with richness . Using galaxy pairs patterned after the SDSS redMaPPer cluster sample study
of Rozo et al. (2015 RMIV), we show that the pairwise velocity PDF of
central--satellite pairs with in the simulation matches the form
seen in RMIV. Through joint membership matching, we deconstruct the main
Gaussian velocity component into its halo contributions, finding that the
top-ranked halo contributes of the stacked signal. The halo mass
scale inferred by applying the virial scaling of Evrard et al. (2008) to the
velocity normalization matches, to within a few percent, the log-mean halo mass
derived through galaxy membership matching. We apply this approach, along with
mis-centering and galaxy velocity bias corrections, to estimate the log-mean
matched halo mass at of SDSS redMaPPer clusters. Employing the velocity
bias constraints of Guo et al. (2015), we find with and .
Systematic uncertainty in the velocity bias of satellite galaxies
overwhelmingly dominates the error budget.Comment: 14 pages, 7 figure
The Baryon Oscillation Spectroscopic Survey of SDSS-III
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the
scale of baryon acoustic oscillations (BAO) in the clustering of matter over a
larger volume than the combined efforts of all previous spectroscopic surveys
of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as
i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7.
Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000
quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5.
Early results from BOSS include the first detection of the large-scale
three-dimensional clustering of the Lyman alpha forest and a strong detection
from the Data Release 9 data set of the BAO in the clustering of massive
galaxies at an effective redshift z = 0.57. We project that BOSS will yield
measurements of the angular diameter distance D_A to an accuracy of 1.0% at
redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the
same redshifts. Forecasts for Lyman alpha forest constraints predict a
measurement of an overall dilation factor that scales the highly degenerate
D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey
is complete. Here, we provide an overview of the selection of spectroscopic
targets, planning of observations, and analysis of data and data quality of
BOSS.Comment: 49 pages, 16 figures, accepted by A
The FMOS-COSMOS survey of star-forming galaxies at z~1.6 III. Survey design, performance, and sample characteristics
We present a spectroscopic survey of galaxies in the COSMOS field using the
Fiber Multi-Object Spectrograph (FMOS), a near-infrared instrument on the
Subaru Telescope. Our survey is specifically designed to detect the Halpha
emission line that falls within the H-band (1.6-1.8 um) spectroscopic window
from star-forming galaxies with 1.4 ~10^10 Msolar. With
the high multiplex capability of FMOS, it is now feasible to construct samples
of over one thousand galaxies having spectroscopic redshifts at epochs that
were previously challenging. The high-resolution mode (R~2600) effectively
separates Halpha and [NII]6585 thus enabling studies of the gas-phase
metallicity and photoionization state of the interstellar medium. The primary
aim of our program is to establish how star formation depends on stellar mass
and environment, both recognized as drivers of galaxy evolution at lower
redshifts. In addition to the main galaxy sample, our target selection places
priority on those detected in the far-infrared by Herschel/PACS to assess the
level of obscured star formation and investigate, in detail, outliers from the
star formation rate - stellar mass relation. Galaxies with Halpha detections
are followed up with FMOS observations at shorter wavelengths using the J-long
(1.11-1.35 um) grating to detect Hbeta and [OIII]5008 that provides an
assessment of extinction required to measure star formation rates not hampered
by dust, and an indication of embedded Active Galactic Nuclei. With 460
redshifts measured from 1153 spectra, we assess the performance of the
instrument with respect to achieving our goals, discuss inherent biases in the
sample, and detail the emission-line properties. Our higher-level data
products, including catalogs and spectra, are available to the community.Comment: 26 pages, Updated version resubmitted to ApJSS; Data products and
catalogs are now available at http://member.ipmu.jp/fmos-cosmos
The MOSFIRE Deep Evolution Field (MOSDEF) Survey: Rest-Frame Optical Spectroscopy for ~1500 H-Selected Galaxies at 1.37 < z < 3.8
In this paper we present the MOSFIRE Deep Evolution Field (MOSDEF) survey.
The MOSDEF survey aims to obtain moderate-resolution (R=3000-3650) rest-frame
optical spectra (~3700-7000 Angstrom) for ~1500 galaxies at 1.37<z<3.80 in
three well-studied CANDELS fields: AEGIS, COSMOS, and GOODS-N. Targets are
selected in three redshift intervals: 1.37<z<1.70, 2.09<z<2.61, and
2.95<z<3.80, down to fixed H_AB (F160W) magnitudes of 24.0, 24.5 and 25.0,
respectively, using the photometric and spectroscopic catalogs from the 3D-HST
survey. We target both strong nebular emission lines (e.g., [OII], Hbeta,
[OIII], 5008, Halpha, [NII], and [SII]) and stellar continuum and absorption
features (e.g., Balmer lines, Ca-II H and K, Mgb, 4000 Angstrom break). Here we
present an overview of our survey, the observational strategy, the data
reduction and analysis, and the sample characteristics based on spectra
obtained during the first 24 nights. To date, we have completed 21 masks,
obtaining spectra for 591 galaxies. For ~80% of the targets we derive a robust
redshift from either emission or absorption lines. In addition, we confirm 55
additional galaxies, which were serendipitously detected. The MOSDEF galaxy
sample includes unobscured star-forming, dusty star-forming, and quiescent
galaxies and spans a wide range in stellar mass (~10^9-10^11.5 Msol) and star
formation rate (~10^0-10^3 Msol/yr). The spectroscopically confirmed sample is
roughly representative of an H-band limited galaxy sample at these redshifts.
With its large sample size, broad diversity in galaxy properties, and wealth of
available ancillary data, MOSDEF will transform our understanding of the
stellar, gaseous, metal, dust, and black hole content of galaxies during the
time when the universe was most active.Comment: Accepted for publication in ApJS; 28 pages, 19 figures; MOSDEF
spectroscopic redshifts available at
http://mosdef.astro.berkeley.edu/Downloads.htm
A spectroscopic survey of thick disc stars outside the solar neighbourhood
We performed a spectroscopic survey of nearly 700 stars probing the galactic
thick disc far from the solar neighbourhood towards the galactic coordinates
(l~277, b~47). The derived effective temperatures, surface gravities and
overall metallicities were then combined with stellar evolution isochrones,
radial velocities and proper motions to derive the distances, kinematics and
orbital parameters of the sample stars. The targets belonging to each galactic
component (thin disc, thick disc, halo) were selected either on their
kinematics or according to their position above the galactic plane, and the
vertical gradients were also estimated. We present here atmospheric parameters,
distances and kinematics for this sample, and a comparison of our kinematic and
metallicity distributions with the Besancon model of the Milky Way. The thick
disc far from the solar neighbourhood is found to differ only slightly from the
thick disc properties as derived in the solar vicinity. For regions where the
thick disc dominates, we measured vertical velocity and metallicity trends of
d(V_phi)/dZ = 19 +/- 8 km/s/kpc and d[M/H]/dZ = -0.14 +/- 0.05 dex/kpc,
respectively. These trends can be explained as a smooth transition between the
different galactic components, although intrinsic gradients could not be
excluded. In addition, a correlation d(V_phi)/d[M/H] = -45 +/- 12 km/s/dex
between the orbital velocity and the metallicity of the thick disc is detected.
This gradient is inconsistent with the SDSS photometric survey analysis, which
did not detect any such trend, and challenges radial migration models of thick
disc formation. Estimations of the scale heights and scale lengths for
different metallicity bins of the thick disc result in consistent values, with
hR~3.4 \pm 0.7 kpc, and hZ~694 \pm 45 pc, showing no evidence of relics of
destroyed massive satellites.Comment: 19 pages, 15 figures, accepted for publication in A&
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