474 research outputs found
The WFC3 Infrared Spectroscopic Parallel (WISP) Survey
We present the WFC3 Infrared Spectroscopic Parallel (WISP) Survey. WISP is
obtaining slitless, near-infrared grism spectroscopy of ~ 90 independent,
high-latitude fields by observing in the pure parallel mode with Wide Field
Camera-3 on the Hubble Space Telescope for a total of ~ 250 orbits. Spectra are
obtained with the G102 (lambda=0.8-1.17 microns, R ~ 210) and G141 grisms
(lambda=1.11-1.67 microns, R ~ 130), together with direct imaging in the J- and
H-bands (F110W and F140W, respectively). In the present paper, we present the
first results from 19 WISP fields, covering approximately 63 square arc
minutes. For typical exposure times (~ 6400 sec in G102 and ~ 2700 sec in
G141), we reach 5-sigma detection limits for emission lines of 5 x 10^(-17)
ergs s^(-1) cm^(-2) for compact objects. Typical direct imaging 5sigma-limits
are 26.8 and 25.0 magnitudes (AB) in F110W and F140W, respectively. Restricting
ourselves to the lines measured with highest confidence, we present a list of
328 emission lines, in 229 objects, in a redshift range 0.3 < z < 3. The
single-line emitters are likely to be a mix of Halpha and [OIII]5007,4959 A,
with Halpha predominating. The overall surface density of high-confidence
emission-line objects in our sample is approximately 4 per arcmin^(2).These
first fields show high equivalent width sources, AGN, and post starburst
galaxies. The median observed star formation rate of our Halpha selected sample
is 4 Msol/year. At intermediate redshifts, we detect emission lines in galaxies
as faint as H_140 ~ 25, or M_R < -19, and are sensitive to star formation rates
down to less than 1 Msol/year. The slitless grisms on WFC3 provide a unique
opportunity to study the spectral properties of galaxies much fainter than L*
at the peak of the galaxy assembly epoch.Comment: 15 pages, 12 figures, submitted to Ap
The Hubble Space Telescope GOODS NICMOS Survey: overview and the evolution of massive galaxies at 1.5 < z < 3
We present the details and early results from a deep near-infrared survey utilizing the NICMOS instrument on the Hubble Space Telescope centred around massive M_* > 10^(11) M_⊙ galaxies at 1.7 10^(11) M_⊙, whereby we find an increase of a factor of 8 between z= 3 and 1.5, demonstrating that this is an epoch when massive galaxies establish most of their stellar mass. We also provide an overview of the evolutionary properties of these galaxies, such as their merger histories, and size evolution
Strange Quarks Nuggets in Space: Charges in Seven Settings
We have computed the charge that develops on an SQN in space as a result of
balance between the rates of ionization by ambient gammas and capture of
ambient electrons. We have also computed the times for achieving that
equilibrium and binding energy of the least bound SQN electrons. We have done
this for seven different settings. We sketch the calculations here and give
their results in the Figure and Table II; details are in the Physical Review
D.79.023513 (2009).Comment: Six pages, one figure. To appear in proceedings of the 2008 UCLA
coference on dark matter and dark energ
Star Formation in Emission-Line Galaxies Between Redshifts of 0.8 and 1.6
Optical spectra of 14 emission-line galaxies representative of the 1999
NICMOS parallel grism Ha survey of McCarthy et al. are presented. Of the 14, 9
have emission lines confirming the redshifts found in the grism survey. The
higher resolution of our optical spectra improves the redshift accuracy by a
factor of 5. The [O II]/Ha values of our sample are found to be more than two
times lower than expected from Jansen et al. This [O II]/Ha ratio discrepancy
is most likely explained by additional reddening in our Ha-selected sample [on
average, as much as an extra E(B-V) = 0.6], as well as to a possible stronger
dependence of the [O II]/Ha ratio on galaxy luminosity than is found in local
galaxies. The result is that star formation rates (SFRs) calculated from [O
II]3727 emission, uncorrected for extinction, are found to be on average 4 +/-
2 times lower than the SFRs calculated from Ha emission. Classification of
emission-line galaxies as starburst or Seyfert galaxies based on comparison of
the ratios [O II]/Hb and [Ne III]3869/Hb is discussed. New Seyfert 1
diagnostics using the Ha line luminosity, H-band absolute magnitude, and Ha
equivalent widths are also presented. One galaxy is classified as a Seyfert 1
based on its broad emission lines, implying a comoving number density for
Seyfert 1s of 2.5{+5.9, -2.1} times 10^{-5} Mpc^{-3}. This commoving number
density is a factor of 2.4{+5.5,-2.0} times higher than estimated by other
surveys.Comment: 51 pages, 18 figures; Accepted for publication in the Astrophysical
Journal; Revised version with minor changes and an additional reference which
gives further support to our conclusion
IRAC Excess in Distant Star-Forming Galaxies: Tentative Evidence for the 3.3m Polycyclic Aromatic Hydrocarbon Feature ?
We present evidence for the existence of an IRAC excess in the spectral
energy distribution (SED) of 5 galaxies at 0.6<z<0.9 and 1 galaxy at z=1.7.
These 6 galaxies, located in the Great Observatories Origins Deep Survey field
(GOODS-N), are star forming since they present strong 6.2, 7.7, and 11.3 um
polycyclic aromatic hydrocarbon (PAH) lines in their Spitzer IRS mid-infrared
spectra. We use a library of templates computed with PEGASE.2 to fit their
multiwavelength photometry and derive their stellar continuum. Subtraction of
the stellar continuum enables us to detect in 5 galaxies a significant excess
in the IRAC band pass where the 3.3 um PAH is expected. We then assess if the
physical origin of the IRAC excess is due to an obscured active galactic
nucleus (AGN) or warm dust emission. For one galaxy evidence of an obscured AGN
is found, while the remaining four do not exhibit any significant AGN activity.
Possible contamination by warm dust continuum of unknown origin as found in the
Galactic diffuse emission is discussed. The properties of such a continuum
would have to be different from the local Universe to explain the measured IRAC
excess, but we cannot definitively rule out this possibility until its origin
is understood. Assuming that the IRAC excess is dominated by the 3.3 um PAH
feature, we find good agreement with the observed 11.3 um PAH line flux arising
from the same C-H bending and stretching modes, consistent with model
expectations. Finally, the IRAC excess appears to be correlated with the
star-formation rate in the galaxies. Hence it could provide a powerful
diagnostic for measuring dusty star formation in z>3 galaxies once the
mid-infrared spectroscopic capabilities of the James Webb Space Telescope
become available.Comment: 25 pages, 4 figures, accepted by Ap
Far-ultraviolet imaging of the Hubble Deep Field-North: Star formation in normal galaxies at z < 1
We present far-ultraviolet (FUV) imaging of the Hubble Deep Field-North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Å. We detect 134 galaxies and one star down to a limit of FUV_(AB) ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0 < z < 1. We find that the FUV galaxy number counts are higher than those reported by GALEX, which we attribute at least in part to cosmic variance in the small HDF-N field of view. Six of the 13 Chandra sources at z < 0.85 in the HDF-N are detected in the FUV, and those are consistent with starbursts rather than active galactic nuclei. Cross-correlating with Spitzer sources in the field, we find that the FUV detections show general agreement with the expected L_(IR)/L_(UV) versus β relationship. We infer star formation rates (SFRs), corrected for extinction using the UV slope, and find a median value of 0.3 M_☉ yr^(-1) for FUV-detected galaxies, with 75% of detected sources having SFR < 1 M_☉ yr^(-1). Examining the morphological distribution of sources, we find that about half of all FUV-detected sources are identified as spiral galaxies. Half of morphologically selected spheroid galaxies at z < 0.85 are detected in the FUV, suggesting that such sources have had significant ongoing star formation in the epoch since z ~ 1
Spitzer infrared spectrometer 16μm observations of the GOODS fields
We present Spitzer 16μm imaging of the Great Observatories Origins Deep Survey (GOODS) fields. We survey
150 arcmin^2 in each of the two GOODS fields (North and South), to an average 3σ depth of 40 and 65 μJy,
respectively. We detect ~1300 sources in both fields combined. We validate the photometry using the 3–24μm
spectral energy distribution of stars in the fields compared to Spitzer spectroscopic templates. Comparison with
ISOCAM and AKARI observations in the same fields shows reasonable agreement, though the uncertainties are
large. We provide a catalog of photometry, with sources cross-correlated with available Spitzer, Chandra, and
Hubble Space Telescope data. Galaxy number counts show good agreement with previous results from ISOCAM
and AKARI with improved uncertainties. We examine the 16–24μm flux ratio and find that for most sources it
lies within the expected locus for starbursts and infrared luminous galaxies. A color cut of S_(16)/S_(24) > 1.4 selects
mostly sources which lie at 1.1 < z < 1.6, where the 24μm passband contains both the redshifted 9.7 μm silicate
absorption and the minimum between polycyclic aromatic hydrocarbon emission peaks. We measure the integrated
galaxy light of 16μm sources and find a lower limit on the galaxy contribution to the extragalactic background
light at this wavelength to be 2.2 ± 0.2 nW m^(−2) sr^(−1)
The Spitzer Archival Far-InfraRed Extragalactic Survey
We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES).
This program produces refined mosaics and source lists for all far-infrared
extragalactic data taken during the more than six years of the cryogenic
operation of the Spitzer Space Telescope. The SAFIRES products consist of
far-infrared data in two wavelength bands (70 um and 160 um) across
approximately 180 square degrees of sky, with source lists containing
far-infrared fluxes for almost 40,000 extragalactic point sources. Thus,
SAFIRES provides a large, robust archival far-infrared data set suitable for
many scientific goals.Comment: 7 pages, 6 figures, published in ApJ
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