380 research outputs found
Extended Photometry for the DEEP2 Galaxy Redshift Survey: A Testbed for Photometric Redshift Experiments
This paper describes a new catalog that supplements the existing DEEP2 Galaxy
Redshift Survey photometric and spectroscopic catalogs with ugriz photometry
from two other surveys; the Canada-France-Hawaii Legacy Survey (CFHTLS) and the
Sloan Digital Sky Survey (SDSS). Each catalog is cross-matched by position on
the sky in order to assign ugriz photometry to objects in the DEEP2 catalogs.
We have recalibrated the CFHTLS photometry where it overlaps DEEP2 in order to
provide a more uniform dataset. We have also used this improved photometry to
predict DEEP2 BRI photometry in regions where only poorer measurements were
available previously. In addition, we have included improved astrometry tied to
SDSS rather than USNO-A2.0 for all DEEP2 objects. In total this catalog
contains ~27,000 objects with full ugriz photometry as well as robust
spectroscopic redshift measurements, 64% of which have r > 23. By combining the
secure and accurate redshifts of the DEEP2 Galaxy Redshift Survey with ugriz
photometry, we have created a catalog that can be used as an excellent testbed
for future photo-z studies, including tests of algorithms for surveys such as
LSST and DES.Comment: 12 pages, 6 figures and 5 tables. Accepted to The Astrophysical
Journal Supplement. Catalogs are publicly available at
http://deep.ps.uci.edu/DR4/photo.extended.htm
Observations of Ultracool White Dwarfs
We present new spectroscopic and photometric measurements of the white dwarfs LHS 3250 and WD 0346+246. Along with F351-50, these white dwarfs are the coolest ones known, all with effective temperatures below 4000 K. Their membership in the Galactic halo population is discussed, and detailed comparisons of all three objects with new atmosphere models are presented. The new models consider the effects of mixed H/He atmospheres and indicate that WD 0346+246 and F351-50 have predominantly helium atmospheres with only traces of hydrogen. LHS 3250 may be a double degenerate whose average radiative temperature is between 2000 and 4000 K, but the new models fail to explain this object
The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts
We describe the design and data sample from the DEEP2 Galaxy Redshift Survey,
the densest and largest precision-redshift survey of galaxies at z ~ 1
completed to date. The survey has conducted a comprehensive census of massive
galaxies, their properties, environments, and large-scale structure down to
absolute magnitude M_B = -20 at z ~ 1 via ~90 nights of observation on the
DEIMOS spectrograph at Keck Observatory. DEEP2 covers an area of 2.8 deg^2
divided into four separate fields, observed to a limiting apparent magnitude of
R_AB=24.1. Objects with z < 0.7 are rejected based on BRI photometry in three
of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5
times more efficiently than in a purely magnitude-limited sample. Approximately
sixty percent of eligible targets are chosen for spectroscopy, yielding nearly
53,000 spectra and more than 38,000 reliable redshift measurements. Most of the
targets which fail to yield secure redshifts are blue objects that lie beyond z
~ 1.45. The DEIMOS 1200-line/mm grating used for the survey delivers high
spectral resolution (R~6000), accurate and secure redshifts, and unique
internal kinematic information. Extensive ancillary data are available in the
DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into
one of the richest multiwavelength regions on the sky. DEEP2 surpasses other
deep precision-redshift surveys at z ~ 1 in terms of galaxy numbers, redshift
accuracy, sample number density, and amount of spectral information. We also
provide an overview of the scientific highlights of the DEEP2 survey thus far.
This paper is intended as a handbook for users of the DEEP2 Data Release 4,
which includes all DEEP2 spectra and redshifts, as well as for the
publicly-available DEEP2 DEIMOS data reduction pipelines. [Abridged]Comment: submitted to ApJS; data products available for download at
http://deep.berkeley.edu/DR4
A Strong-Lens Survey in AEGIS: the influence of large scale structure
We report on the results of a visual search for galaxy-scale strong
gravitational lenses over 650 arcmin^2 of HST/ACS imaging in the DEEP2-EGS
field. In addition to a previously-known Einstein Cross (the "Cross," HST
J141735+52264, with z_lens=0.8106 and a published z_source=3.40), we identify
two new strong galaxy-galaxy lenses with multiple extended arcs. The first, HST
J141820+52361 (the ``Dewdrop''; z_lens=0.5798, lenses two distinct extended
sources into two pairs of arcs z_source=0.while), 9818 the second, HST
J141833+52435 (the ``Anchor''; z_lens=0.4625), produces a single pair of arcs
(source redshift not yet known). All three definite lenses are fit well by
simple singular isothermal ellipsoid models including external shear. Using the
three-dimensional line-of-sight (LOS) information on galaxies from the DEEP2
data, we calculate the convergence and shear contributions, assuming singular
isothermal sphere halos truncated at 200 h^-1 kpc. These are also compared
against three-dimensional local-density estimates. We find that even strong
lenses in demonstrably underdense local environments may be considerably
affected by LOS contributions, which in turn, may be underestimates of the
effect of large scale structure.Comment: ApJ Letters, submitted. Part of the AEGIS ApJL Special Issue. 4
Figures, 1 Table. For a version with full-resolution figures, please see
http://www.slac.stanford.edu/~pjm/HAGGLeS/astroph/legs.pd
Mid-infrared Identification of 6 cm Radio Source Counterparts in the Extended Groth Strip
A new 6-cm survey of almost 0.6 square degrees to a limit of 0.55-mJy/beam
(10-sigma) finds 37 isolated radio sources and 7 radio source pairs (not
necessarily physical companions). IRAC counterparts are identified for at least
92% of the radio sources within the area of deep IRAC coverage, which includes
31 isolated sources and 6 pairs. This contrasts with an identification rate of
<74% to R<23.95 in visible light. Eight of the IRAC galaxies have power law
spectral energy distributions, implying that the mid-infrared emission comes
from a powerful AGN. The remaining 26 IRAC galaxies show stellar emission in
the mid-infrared, probably in most of these galaxies because the stellar
emission is bright enough to outshine an underlying AGN. The infrared colors
suggest that the majority of these galaxies are bulge-dominated and have
redshifts between approximately 0.5 and 1.0. Visible spectra from the DEEP2
redshift survey, available for 11 galaxies, are consistent with this
suggestion. The IRAC galaxies fall into two distinct groups in a
color-magnitude diagram, one group (the "stripe") includes all the AGN. The
other group (the "blue clump") has blue 3.6 to 8 micron colors and a small
range of 8 micron magnitudes. This separation should be useful in classifying
galaxies found in other radio surveys.Comment: Accepted by A
Science Objectives and Early Results of the DEEP2 Redshift Survey
The DEIMOS spectrograph has now been installed on the Keck-II telescope and
commissioning is nearly complete. The DEEP2 Redshift Survey, which will take
approximately 120 nights at the Keck Observatory over a three year period and
has been designed to utilize the power of DEIMOS, began in the summer of 2002.
The multiplexing power and high efficiency of DEIMOS enables us to target 1000
faint galaxies per clear night. Our goal is to gather high-quality spectra of
\~60,000 galaxies with z>0.75 in order to study the properties and large scale
clustering of galaxies at z ~ 1. The survey will be executed at high spectral
resolution, , allowing us to work
between the bright OH sky emission lines and to infer linewidths for many of
the target galaxies (for several thousand objects, we will obtain rotation
curves as well). The linewidth data will facilitate the execution of the
classical redshift-volume cosmological test, which can provide a precision
measurement of the equation of state of the Universe. This talk reviews the
project, summarizes our science goals and presents some early DEIMOS data.Comment: 12 pages, 5 figures, talk presented at SPIE conference, Aug. 200
AEGIS-X: The Chandra Deep Survey of the Extended Groth Strip
We present the AEGIS-X survey, a series of deep Chandra ACIS-I observations
of the Extended Groth Strip. The survey comprises pointings at 8 separate
positions, each with nominal exposure 200ks, covering a total area of
approximately 0.67 deg2 in a strip of length 2 degrees. We describe in detail
an updated version of our data reduction and point source detection algorithms
used to analyze these data. A total of 1325 band-merged sources have been found
to a Poisson probability limit of 4e-6, with limiting fluxes of 5.3e-17
erg/cm2/s in the soft (0.5-2 keV) band and 3.8e-16 erg/cm2/s in the hard (2-10
keV) band. We present simulations verifying the validity of our source
detection procedure and showing a very small, <1.5%, contamination rate from
spurious sources. Optical/NIR counterparts have been identified from the DEEP2,
CFHTLS, and Spitzer/IRAC surveys of the same region. Using a likelihood ratio
method, we find optical counterparts for 76% of our sources, complete to
R(AB)=24.1, and, of the 66% of the sources that have IRAC coverage, 94% have a
counterpart to a limit of 0.9 microJy at 3.6 microns (m(AB)=23.8). After
accounting for (small) positional offsets in the 8 Chandra fields, the
astrometric accuracy of the Chandra positions is found to be 0.8 arcsec RMS,
however this number depends both on the off-axis angle and the number of
detected counts for a given source. All the data products described in this
paper are made available via a public website.Comment: 17 pages, 9 figures. Accepted for publication in ApJS. Data products
are available at http://astro.imperial.ac.uk/research/aegis
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Contains reports on seven research projects.Lincoln Laboratory (Purchase Order DDL-B222
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