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Jeffrey A. Newman,
Michael C. Cooper,
Marc Davis,
S. M. Faber,
Alison L. Coil,
Puragra Guhathakurta,
David C. Koo,
Andrew C. Phillips,
Charlie Conroy,
Aaron A. Dutton, [......],
Nick Kaiser,
Evan N. Kirby,
Brian C. Lemaux,
Lihwai Lin,
Jennifer M. Lotz,
Gerard A. Luppino,
Christian Marinoni,
Daniel J. Matthews,
Anne Metevier,
Ricardo P. Schiavon
[show abstract]
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ABSTRACT: 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]
03/2012;
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[show abstract]
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ABSTRACT: We present a sample of 407 z~3 Lyman break galaxies (LBGs) to a limiting isophotal u-band magnitude of 27.6 mag in the Hubble Ultra Deep Field (UDF). The LBGs are selected using a combination of photometric redshifts and the u-band drop-out technique enabled by the introduction of an extremely deep u-band image obtained with the Keck I telescope and the blue channel of the LRIS spectrometer. The Keck u-band image, totaling 9 hours of integration time, has a one sigma depth of 30.7 mag arcsec^-2, making it one of the most sensitive u-band images ever obtained. The u-band image also substantially improves the accuracy of photometric redshift measurements of ~50% of the z~3 Lyman break galaxies, significantly reducing the traditional degeneracy of colors between z~3 and z~0.2 galaxies. This sample provides the most sensitive, high-resolution multi-filter imaging of reliably identified z~3 LBGs for morphological studies of galaxy formation and evolution and the star formation efficiency of gas at high redshift. Comment: 18 pages, 13 figures, proof corrections included
08/2009;
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R. G. Carlberg,
Judith G. Cohen,
D. R. Patton,
Roger Blandford,
David W. Hogg,
H. K. C. Yee,
S. L. Morris,
H. Lin,
Patrick B. Hall,
M. Sawicki, Gregory D. Wirth,
Lennox L. Cowie,
Esther Hu,
and Antoinette Songaila
[show abstract]
[hide abstract]
ABSTRACT: The rate of mass accumulation due to galaxy merging depends on the mass, density, and velocity distribution of galaxies in the near neighborhood of a host galaxy. The fractional luminosity in kinematic pairs combines all of these effects in a single estimator that is relatively insensitive to population evolution. Here we use a k-corrected and evolution-compensated volume-limited sample having an R-band absolute magnitude of M ≤ -19.8 + 5 log h mag drawing about 300 redshifts from the Caltech Faint Galaxy Redshift Survey and 3000 from the Canadian Network for Observational Cosmology field galaxy survey to measure the rate and redshift evolution of merging. The combined sample has an approximately constant comoving number and luminosity density from redshift 0.1 to 1.1 (ΩM = 0.2, ΩΛ = 0.8); hence, any merger evolution will be dominated by correlation and velocity evolution, not density evolution. We identify kinematic pairs with projected separations less than either 50 or 100 h-1 kpc and rest-frame velocity differences of less than 1000 km s-1. The fractional luminosity in pairs is modeled as fL(Δv, rp, M)(1 + z), where [fL, mL] are [0.14 ± 0.07, 0 ± 1.4] and [0.37 ± 0.7, 0.1 ± 0.5] for rp ≤ 50 and 100 h-1 kpc, respectively (ΩM = 0.2, ΩΛ = 0.8). The value of mL is about 0.6 larger if Λ = 0. To convert these redshift-space statistics to a merger rate, we use the data to derive a conversion factor to a physical space pair density, a merger probability, and a mean in-spiral time. The resulting mass accretion rate per galaxy (M1, M2 ≥ 0.2M*) is 0.02 ± 0.01(1 + z)0.1±0.5M* Gyr-1. Present-day high-luminosity galaxies therefore have accreted approximately 0.15M* of their mass over the approximately 7 Gyr to redshift 1. Since merging is likely only weakly dependent on the host mass, the fractional effect, δM/M 0.15M*/M, is dramatic for lower mass galaxies but is, on the average, effectively perturbative for galaxies above 1M*.
The Astrophysical Journal 12/2008; 532(1):L1. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present a sample of 47 confirmed and 14 candidate active galactic nuclei (AGNs) discovered in the Canadian Network for Observational Cosmology field galaxy redshift survey (CNOC2). The sample consists of 38 objects identified from broad emission lines, eight from narrow [Ne V] emission, and 15 candidates from Fe II or Mg II absorption lines, one of which has been confirmed as a broad-line AGN via infrared spectroscopy. Redshifts of these AGNs range from z = 0.27 to z = 4.67, and the average absolute magnitude is MB -22.25, below the quasar/Seyfert division at MB = -23. Only two of the AGNs are detected at radio wavelengths. We find that only 0.3%±0.1% of galaxies brighter than ~M* + 1 at 0.281 < z < 0.685 contain broad-line or [Ne V] AGNs. We find a total surface density of 270–400 AGNs deg-2 to R = 22.09, comparable to previously published estimates. About 20% of these AGNs are classified as resolved or probably resolved in CFHT seeing and might be missed in surveys that target unresolved objects only. The sample includes several unusual objects: one with a very strong double-peaked Mg II emission line, several with unusual emission-line properties, one with an O III λ3133 broad absorption line, at least one with an optical absorption-line spectrum but broad Hα emission in the near-IR. No color selection criteria were involved in selecting this spectroscopically discovered sample. The sample is also unbiased against objects with luminous host galaxies, since the spectroscopy preferentially targeted extended objects. Simple color-color diagram selection criteria can recover ~81% ± 6% of the CNOC2 AGNs, but several of the most unusual objects would be missing from such a color-selected sample. In the subsample of broad emission line–selected AGNs, the average equivalent widths for Mg II and C III] agree with the predictions of previous studies of the Baldwin effect. However, the average equivalent widths for C IV and Lyα are smaller than predicted by previous studies of the Baldwin effect at lower redshift. This may imply that the slopes of the C IV and Lyα Baldwin effects evolve with redshift, steepening with cosmic time. The broad emission line subsample also shows a higher incidence of associated Mg II λ2798 absorption than in most previous surveys and an incidence of associated C IV λ1549 absorption that may be more similar to that of radio-selected quasar samples than optically selected ones. This may arise from strong absorption being anticorrelated with optical luminosity or becoming less frequent with cosmic time or possibly because our selection method is not biased against objects with resolved spatial structure or reddened by dust associated with the absorbing gas.
The Astronomical Journal 12/2007; 120(5):2220. · 4.03 Impact Factor
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Gregory D. Wirth,
Christopher N. A. Willmer,
Paola Amico,
Frederic H. Chaffee,
Robert W. Goodrich,
Shui Kwok,
James E. Lyke,
Jeff A. Mader,
Hien D. Tran,
Amy J. Barger, [......],
Alison L. Coil,
Michael C. Cooper,
Al Conrad,
Marc Davis,
S. M. Faber,
Esther M. Hu,
David C. Koo,
David Le Mignant,
Jeffrey A. Newman,
and Antoinette Songaila
[show abstract]
[hide abstract]
ABSTRACT: We report the results of an extensive imaging and spectroscopic survey in the Great Observatories Origins Deep Survey (GOODS)-North field completed using DEIMOS on the Keck II telescope. Observations of 2018 targets in a magnitude-limited sample of 2911 objects to RAB = 24.4 yield secure redshifts for a sample of 1440 galaxies and active galactic nuclei (AGNs) plus 96 stars. In addition to redshifts and associated quality assessments, our catalog also includes photometric and astrometric measurements for all targets detected in our R-band imaging survey of the GOODS-North region. We investigate various sources of incompleteness and find the redshift catalog to be 53% complete at its limiting magnitude. The median redshift of z = 0.65 is lower than in similar deep surveys because we did not select against low-redshift targets. Comparison with other redshift surveys in the same field, including a complementary Hawaii-led DEIMOS survey, establishes that our velocity uncertainties are as low as σ ≈ 40 km s-1 for red galaxies and that our redshift confidence assessments are accurate. The distributions of rest-frame magnitudes and colors among the sample agree well with model predictions out to and beyond z = 1. We will release all survey data, including extracted one-dimensional and sky-subtracted two-dimensional spectra, thus providing a sizable and homogeneous database for the GOODS-North field, which will enable studies of large-scale structure, spectral indices, internal galaxy kinematics, and the predictive capabilities of photometric redshifts.
The Astronomical Journal 12/2007; 127(6):3121. · 4.03 Impact Factor
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[show abstract]
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ABSTRACT: We have undertaken a Keck spectral survey of galaxies to R~24 near the central region of Cl0024+1654 at z=0.4. The spectral resolution and slits have been selected to yield kinematics such as the velocity dispersions of early-type systems and rotation curves of disks. The spectra also provide a suite of lines that yield star formation, age, and metallicity information.
11/2001;
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[show abstract]
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ABSTRACT: We present five candidate gravitational lenses discovered spectroscopically in the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2), along with one found in followup observations. Each has a secure redshift based on several features, plus a discrepant emission line which does not match any known or plausible feature and is visible in multiple direct spectral images. We identify these lines as Lyman-alpha or [OII] emission from galaxies lensed by, or projected onto, the CNOC2 target galaxies. Einstein radii estimated from the candidate deflector galaxy luminosities indicate that for two candidates the lines are probably [OII] from projected z<1 galaxies (consistent with the detection of H-beta as well as [OII] in one of them), but that in the remaining four cases the lines could be Ly-alpha from lensed z>3 galaxies. We estimate that only 1.9+-0.7 [OII]-emitting galaxies are expected to project onto target galaxies in the original CNOC2 sample, consistent with three or four of the six candidates being true gravitational lenses. Comment: 15 pages, 4 figures, AJ in press
06/2000;
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[show abstract]
[hide abstract]
ABSTRACT: The rich galaxy cluster Cl0016+16 at z=0.55 initially achieved
visibility (Koo 1981) for being the original ``anti Butcher-Oemler
effect'' cluster: its galaxy population was found to be almost entirely
red, indistinguishable in rest-frame color from local E/S0 galaxies,
despite the expectation that higher redshift clusters should have a
greater proportion of blue galaxies (Butcher & Oemler 1978, 1984).
Interest in this cluster has heightened over the last decade as: X-ray
observations found it to be among the most luminous clusters known
(Henry et al. 1992); radio observations showed it to be among only a
handful of clusters exhibiting a Sunyaev-Zel'dovich microwave decrement,
useful for measuring the Hubble Constant (Lasenby 1992); optical
spectroscopy revealed a significant population of ``E+A'' galaxies,
enigmatic objects with spectra suggesting a recently-concluded episode
of star formation (Dressler & Gunn 1992). Further observations by
ROSAT, ASCA, and HST have established Cl0016+16 as among the
best-studied clusters beyond Coma. The red nature of its galaxy
population makes Cl0016+16 a prime candidate for the study of cluster
galaxy evolution. As part of an ongoing effort to study the early-type
galaxies in this cluster, we recently used the Keck Telescope and
Low-Resolution Imaging Spectrograph to obtain high quality spectra of 19
cluster members at 6 Angstroms (FWHM) resolution. This poster describes
the preliminary results from these data, which will allow us to
investigate galaxy age and metallicity at lookback times nearly halfway
to the Big Bang, probe the internal kinematics of galaxies at z=0.55,
and thus perhaps trace the evolution of the ``fundamental plane'' for
E/S0 galaxies.
11/1994; 26:1403.
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ABSTRACT: We present Hubble Space Telescope (HST) images of 24 confirmed members
of the distant galaxy cluster Cl 0016+16 at redshift 0.55. The
Balmer-strong ('E + A') and emission-line galaxies frequently show
unusual visual morphology, implying that galaxian interactions produce
'active' galaxies in moderate-redshift clusters. We use an image
concentration index as a quantitative measure of morphology to show that
these unusual galaxies appear disklike, while the normal red galaxies
resemble E/S0 galaxies. Although consistent with HST observations by
Dressler et al. in Cl 0939+4713 (z = 0.41), our results differ from the
Couch et al. finding that most Balmer-strong galaxies in AC 114 (z =
0.31) resemble ellipticals. The entire 'E + A' sample is small, but if
future studies confirm their diversity, it will suggest that they have
different origins.
The Astrophysical Journal 10/1994; 435:L105-L108. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present HST images of 24 confirmed members of the distant galaxy cluster Cl0016+16 at redshift 0.55. The Balmer-strong (``E+A'') and emission- line galaxies frequently show unusual visual morphology, implying that galaxian interactions produce ``active'' galaxies in moderate-redshift clusters. We use the image concentration index as a quantitative measure of morphology to show that these unusual galaxies appear disklike, while the normal red galaxies resemble E/S0s. Although consistent with HST observations by Dressler et al. in Cl0939+4713 ($z=0.41$), our results differ from the Couch et al. finding that most Balmer-strong galaxies in AC114 ($z=0.31$) resemble ellipticals. The entire ``E+A'' sample is small, but if future studies confirm their diversity, it will suggest that they have different origins. Comment: 11 pages, uuencoded compressed PostScript, accepted to ApJ Letters, LICK-32
09/1994;
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[show abstract]
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ABSTRACT: We present the results of Hubble Space Telescope (HST) Wide-Field Camera (WFC) imaging of seven very compact, very blue galaxies with B less than or equal to 21 and redshifts z approximately 0.1 to 0.35. Based on deconvolved images, we estimate typical half-light diameters of approximately 0.65 sec, corresponding to approximately 1.4 h(exp -1) kpc at redshifts z approximately 0.2. The average rest frame surface brightness within this diameter is mu(sub v) approximately 20.5 mag arcsec(exp -2), approximately 1 mag brighter than that of typical late-type blue galaxies. Ground-based spectra show strong, narrow emission lines indicating high ionization; their very blue colors suggest recent bursts of star-formation; their typical luminosities are approximately 4 times fainter than that of field galaxies. These characteristics suggest H II galaxies as likely local counterparts of our sample, though our most luminous targets appear to be unusually compact for their luminosities.
06/1994;
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[show abstract]
[hide abstract]
ABSTRACT: Several previous studies of distant clusters have suggested that
significant evolution of cluster galaxies, either photometric or
spectroscopic, occurs over lookback times of only a few Gyr (e.g.,
Butcher & Oemler 1984, Dressler & Gunn 1992). One cluster has
proven particularly interesting by appearing to be simultaneously old
and young: Cl0016+16 at z=0.54 is photometrically unevolved, with
galaxies similar in colors to present-day ellipticals (Koo 1981) despite
a lookback time of half the age of universe. On the other hand, galaxy
spectra indicate 0016+16 has a significant population of ``E+A''
galaxies, leading Dressler to state that ``the population of this
extremely rich cluster...is the most unusual we have found.'' We have
recently obtained 3 hours of WF/PC 785LP (I) band imaging in the core of
Cl0016+16, making this the most distant bona fide cluster studied with
HST. The images contain nearly 100 galaxies down to I~24, reaching
M(*+3) (for h=0.5, q_0=0.05). This poster describes the preliminary
results from these images, which will allow us to probe the size and
surface brightness of early-type galaxies at moderate redshift,
determine the morphology of the ``E+A'' population, and search for
evidence of arclets produced by gravitationally-lensed background
galaxies.
04/1993; 25:838.
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ABSTRACT: For over a decade, the W. M. Keck Observatory's two 10-meter telescopes have been operated remotely from its Waimea headquarters. Over the last 9 years, WMKO remote observing has expanded to allow observing teams at dedicated sites located across California to observe via the Internet either in collaboration with colleagues in Waimea or entirely from California; this capability was extended to Swinburne University in Melbourne, Australia in 2010 and to Yale University in New Haven, Connecticut in early 2011. All Keck facility science instruments are currently supported. Observers distributed between as many as four sites can collaborate in the interactive operation of each instrument by means of shared VNC desktops and multipoint video and/or telephone conferencing. Automated routers at primary remote observing sites ensure continued connectivity during Internet outages. Each Keck remote observing facility is similarly equipped and configured so observers have the same operating envi-ronment. This architecture provides observers the flexibility to conduct observations from the location best suited to their needs and to adapt to last-minute changes. It also enhances the ability of off-site technical staff to provide remote support.
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ABSTRACT: For over a decade, the W. M. Keck Observatory's two 10-meter telescopes have been operated remotely from its Waimea headquarters. Over the last 6 years, WMKO remote observing has expanded to allow teams at dedicated sites in California to observe either in collaboration with colleagues in Waimea or entirely from the U.S. mainland. Once an experimental effort, the Observatory's mainland observing capability is now fully operational, supported on all science instruments (except the interferometer) and regularly used by astronomers at eight mainland sites. Establishing a convenient and secure observing capability from those sites required careful planning to ensure that they are properly equipped and configured. It also entailed a significant investment in hardware and software, including both custom scripts to simplify launching the instrument interface at remote sites and automated routers employing ISDN backup lines to ensure continuation of observing during Internet outages. Observers often wait until shortly before their runs to request use of the mainland facilities. Scheduling these requests and ensuring proper system operation prior to observing requires close coordination between personnel at WMKO and the mainland sites. An established protocol for approving requests and carrying out pre-run checkout has proven useful in ensuring success. The Observatory anticipates enhancing and expanding its remote observing system. Future plans include deploying dedicated summit computers for running VNC server software, implementing a web-based tracking system for mainland-based observing requests, expanding the system to additional mainland sites, and converting to full-time VNC operation for all instruments.
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ABSTRACT: Remote observing is the dominant mode of operation for both Keck Telescopes and their associated instruments. Over 90% of all Keck observations are carried out remotely from the Keck Headquarters in Waimea, Hawaii (located 40 kilometers from the telescopes on the summit of Mauna Kea). In addition, an increasing number of observations are now conducted by geographically-dispersed observing teams, with some team members working from Waimea while others collaborate from Keck remote observing facilities located in California. Such facilities are now operational on the Santa Cruz and San Diego campuses of the University of California, and at the California Institute of Technology in Pasadena. This report describes our use of the X 1 and VNC 2 protocols for providing remote and shared graphical displays to distributed teams of observers and observing assistants located at multiple sites. We describe the results of tests involving both protocols, and explore the limitations and performance of each under different regimes of network bandwidth and latency. We also examine other constraints imposed by differences in the processing performance and bit depth of the various frame buffers used to generate these graphical displays. Other topics covered include the use of ssh 3 tunnels for securely encapsulating both X and VNC protocol streams and the results of tests of ssh compression to improve performance under conditions of limited network bandwidth. We also examine trade-offs between different topologies for locating VNC servers and clients when sharing displays between multiple sites.
