14 research outputs found
Far-Ultraviolet Number Counts on Field Galaxies
The far-ultraviolet (FUV) number counts of galaxies constrain the evolution of the star formation rate density of the universe. We report the FUV number counts computed from FUV imaging of several fields including the Hubble Ultra Deep Field, the Hubble Deep Field North, and small areas within the GOODS-North and South fields. These data were obtained with the Hubble Space Telescope (HST) Solar Blind Channel of the Advance Camera for Surveys. The number counts sample an FUV AB magnitude range from 21 to 29 and cover a total area of 15.9 arcmin^2, ~4 times larger than the most recent HST FUV study. Our FUV counts intersect bright FUV Galaxy Evolution Explorer counts at 22.5 mag and they show good agreement with recent semi-analytic models based on dark matter "merger trees" by R. S. Somerville et al. We show that the number counts are ~35% lower than in previous HST studies that use smaller areas. The differences between these studies are likely the result of cosmic variance; our new data cover more lines of sight and more area than previous HST FUV studies. The integrated light from field galaxies is found to contribute between 65.9^(+8)_(–8) and 82.6^(+12)_(–)12 photons s^(–1) cm^(–2) sr^(–1) Å^(–1) to the FUV extragalactic background. These measurements set a lower limit for the total FUV background light
Far-Ultraviolet Number Counts of Field Galaxies
The far-ultraviolet (FUV) number counts of galaxies constrain the evolution
of the star-formation rate density of the universe. We report the FUV number
counts computed from FUV imaging of several fields including the Hubble Ultra
Deep Field, the Hubble Deep Field North, and small areas within the GOODS-North
and -South fields. These data were obtained with the Hubble Space Telescope
Solar Blind Channel of the Advance Camera for Surveys. The number counts sample
a FUV AB magnitude range from 21-29 and cover a total area of 15.9 arcmin^2, ~4
times larger than the most recent HST FUV study. Our FUV counts intersect
bright FUV GALEX counts at 22.5 mag and they show good agreement with recent
semi-analytic models based on dark matter "merger trees" by Somerville et al.
(2011). We show that the number counts are ~35% lower than in previous HST
studies that use smaller areas. The differences between these studies are
likely the result of cosmic variance; our new data cover more lines of sight
and more area than previous HST FUV studies. The integrated light from field
galaxies is found to contribute between 65.9 +/-8 - 82.6 +/-12
photons/s/cm^2/sr/angstrom to the FUV extragalactic background. These
measurements set a lower limit for the total FUV background light.Comment: Accepted for publication in ApJ, including 34 pages, 6 figures, and 2
table
Near-Ultraviolet Sources in the Hubble Ultra Deep Field: The Catalog
The catalog from the first high-resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble's Wide-Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained far-ultraviolet (FUV, 1614 Ã…) data with Hubble's Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with GALEX. We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented
The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) III. The Ultraviolet Source Catalogs
In this paper we introduce the deepest and most extensive ultraviolet
extragalactic source catalogs of the Virgo Cluster area to date. Archival and
targeted GALEX imaging is compiled and combined to provide the deepest possible
coverage over ~120 deg^2 in the NUV (lambda_eff=2316 angstroms) and ~40 deg^2
in the FUV (lambda_eff=1539 angstroms) between 180 deg <= R.A. <= 195 deg and 0
deg <= Decl. <= 20 deg. We measure the integrated photometry of 1770 extended
UV sources of all galaxy types and use GALEX pipeline photometry for 1,230,855
point-like sources in the foreground, within, and behind the cluster. Extended
source magnitudes are reliable to m_UV ~22, showing ~0.01 sigma difference from
their asymptotic magnitudes. Point-like source magnitudes have a 1 sigma
standard deviation within ~0.2 mag down to m_uv ~23. The point-like source
catalog is cross-matched with large optical databases and surveys including the
SDSS DR9 (> 1 million Virgo Cluster sources), the Next Generation Virgo Cluster
Survey (NGVS; >13 million Virgo Cluster sources), and the NED (~30,000 sources
in the Virgo Cluster). We find 69% of the entire UV point-like source catalog
has a unique optical counterpart, 11% of which are stars and 129 are Virgo
cluster members neither in the VCC nor part of the bright CGCG galaxy catalog
(i.e., m_pg < 14.5). These data are collected in four catalogs containing the
UV extended sources, the UV point-like sources, and two catalogs each
containing the most relevant optical parameters of UV-optically matched
point-like sources for further studies from SDSS and NGVS. The GUViCS catalogs
provide a unique set of data for future works on UV and multiwavelength studies
in the cluster and background environments.Comment: 35 pages, 24 figures, 15 tables, Accepted for publication in A&
An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst
We present a synthetic spectral analysis of nearly the entire far ultraviolet
International Ultraviolet Explorer (IUE) archive of spectra of dwarf novae in
or near outburst. The study includes 46 systems of all dwarf nova subtypes both
above and below the period gap. The spectra were uniformly analyzed using
synthetic spectral codes for optically thick accretion disks and stellar
photospheres along with the best-available distance measurements or estimates.
We present newly estimated accretion rates and discuss the implications of our
study for disk accretion physics and CV evolution.Comment: Accepted for publication in the ApJ, Part
UVUDF: Ultraviolet Imaging of the Hubble Ultradeep Field with Wide-field Camera 3
We present an overview of a 90-orbit Hubble Space Telescope treasury program
to obtain near ultraviolet imaging of the Hubble Ultra Deep Field using the
Wide Field Camera 3 UVIS detector with the F225W, F275W, and F336W filters.
This survey is designed to: (i) Investigate the episode of peak star formation
activity in galaxies at 1<z<2.5; (ii) Probe the evolution of massive galaxies
by resolving sub-galactic units (clumps); (iii) Examine the escape fraction of
ionizing radiation from galaxies at z~2-3; (iv) Greatly improve the reliability
of photometric redshift estimates; and (v) Measure the star formation rate
efficiency of neutral atomic-dominated hydrogen gas at z~1-3. In this overview
paper, we describe the survey details and data reduction challenges, including
both the necessity of specialized calibrations and the effects of charge
transfer inefficiency. We provide a stark demonstration of the effects of
charge transfer inefficiency on resultant data products, which when
uncorrected, result in uncertain photometry, elongation of morphology in the
readout direction, and loss of faint sources far from the readout. We agree
with the STScI recommendation that future UVIS observations that require very
sensitive measurements use the instrument's capability to add background light
through a "post-flash". Preliminary results on number counts of UV-selected
galaxies and morphology of galaxies at z~1 are presented. We find that the
number density of UV dropouts at redshifts 1.7, 2.1, and 2.7 is largely
consistent with the number predicted by published luminosity functions. We also
confirm that the image mosaics have sufficient sensitivity and resolution to
support the analysis of the evolution of star-forming clumps, reaching 28-29th
magnitude depth at 5 sigma in a 0.2 arcsecond radius aperture depending on
filter and observing epoch.Comment: Accepted A