1,220 research outputs found
The FRII Broad Line Seyfert 1 Galaxy: PKSJ 1037-2705
In this article, we demonstrate that PKSJ 1037-2705 has a weak accretion flow
luminosity, well below the Seyfert1/QSO dividing line, weak broad emission
lines (BELs) and moderately powerful FRII extended radio emission. It is one of
the few documented examples of a broad-line object in which the time averaged
jet kinetic luminosity, , is larger than the total thermal luminosity
(IR to X-ray) of the accretion flow, . The blazar nucleus dominates
the optical and near ultraviolet emission and is a strong source of hard
X-rays. The strong blazar emission indicates that the relativistic radio jet is
presently active. The implication is that even weakly accreting AGN can create
powerful jets. Kinetically dominated () broad-line objects
provide important constraints on the relationship between the accretion flow
and the jet production mechanism.Comment: To appear in ApJ November 1, 2008, v687n1 issu
The role of quenching time in the evolution of the mass-size relation of passive galaxies from the WISP survey
We analyze how passive galaxies at z 1.5 populate the mass-size plane
as a function of their stellar age, to understand if the observed size growth
with time can be explained with the appearance of larger quenched galaxies at
lower redshift. We use a sample of 32 passive galaxies extracted from the Wide
Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic
redshift 1.3 z 2.05, specific star-formation rates lower
than 0.01 Gyr, and stellar masses above 4.5 10
M. All galaxies have spectrally determined stellar ages from fitting of
their rest-frame optical spectra and photometry with stellar population models.
When dividing our sample into young (age 2.1 Gyr) and old (age 2.1
Gyr) galaxies we do not find a significant trend in the distributions of the
difference between the observed radius and the one predicted by the mass-size
relation. This result indicates that the relation between the galaxy age and
its distance from the mass-size relation, if it exists, is rather shallow, with
a slope alpha -0.6. At face value, this finding suggests that
multiple dry and/or wet minor mergers, rather than the appearance of newly
quenched galaxies, are mainly responsible for the observed time evolution of
the mass-size relation in passive galaxies.Comment: Accepted for publication in ApJ Letters; 6 pages, 3 figures, 1 tabl
A Catalog of Candidate Intermediate-luminosity X-ray Objects
ROSAT, and now Chandra, X-ray images allow studies of extranuclear X-ray
point sources in galaxies other than our own. X-ray observations of normal
galaxies with ROSAT and Chandra have revealed that off-nuclear, compact,
Intermediate-luminosity (Lx[2-10 keV] >= 1e39 erg/s) X-ray Objects (IXOs,
a.k.a. ULXs [Ultraluminous X-ray sources]) are quite common. Here we present a
catalog and finding charts for 87 IXOs in 54 galaxies, derived from all of the
ROSAT HRI imaging data for galaxies with cz <= 5000 km/s from the Third
Reference Catalog of Bright Galaxies (RC3). We have defined the cutoff Lx for
IXOs so that it is well above the Eddington luminosity of a 1.4 Msun black hole
(10^38.3 erg/s), so as not to confuse IXOs with ``normal'' black hole X-ray
binaries. This catalog is intended to provide a baseline for follow-up work
with Chandra and XMM, and with space- and ground-based survey work at
wavelengths other than X-ray. We demonstrate that elliptical galaxies with IXOs
have a larger number of IXOs per galaxy than non-elliptical galaxies with IXOs,
and note that they are not likely to be merely high-mass X-ray binaries with
beamed X-ray emission, as may be the case for IXOs in starburst galaxies.
Approximately half of the IXOs with multiple observations show X-ray
variability, and many (19) of the IXOs have faint optical counterparts in DSS
optical B-band images. Follow-up observations of these objects should be
helpful in identifying their nature.Comment: 29 pages, ApJS, accepted (catalog v2.0) (full resolution version of
paper and future releases of catalog at http://www.xassist.org/ixocat_hri
The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System
We describe the layout and unique features of the focal plane system for
MIRI. We begin with the detector array and its readout integrated circuit
(combining the amplifier unit cells and the multiplexer), the electronics, and
the steps by which the data collection is controlled and the output signals are
digitized and delivered to the JWST spacecraft electronics system. We then
discuss the operation of this MIRI data system, including detector readout
patterns, operation of subarrays, and data formats. Finally, we summarize the
performance of the system, including remaining anomalies that need to be
corrected in the data pipeline
A Radio Monitoring Survey of Ultra-Luminous X-Ray Sources
We present the results of a radio monitoring campaign to search for radio
emission from nearby ultra-luminous X-ray sources (ULXs). These sources are
bright off-nuclear X-ray point sources with luminosities exceeding L_X > 10^39
erg/sec. A well-defined sample of the 9 nearest ULXs has been monitored eight
times during 5 months with the Very Large Array in A and B configuration. Our
limiting sensitivity is approximately 0.15 mJy (4 sigma) for radio flares and
around 60 uJy for continuous emission. In M82 two ULXs seem to have coincident
compact radio sources, which are probably supernova remnants. No continuous or
flaring radio emission has been detected from any other ULX. Thus, ULXs do not
generally emit steady-state radio emission above radio powers of 1.5 10^17
W/Hz. The non-detections of the continuous emission are consistent with beamed
or unbeamed radio emission from accreting black holes of <= 10^3 Msol based on
the radio/X-ray correlation. Other published radio detections (M82, NGC 5408)
are also discussed in this context. Both detections are significantly above our
detection limit. If ULXs have flaring radio emission above 4 10^17 W/Hz we can
give an upper limit on the duty circle of the flares of 6%. This upper limit is
in agreement with the observed number of flares in Galactic radio transients.
Additionally we present a yet unreported radio double structure in the nearby
low-luminosity AGN NGC 4736.Comment: Accepted for publication in A&A, 11 pages, 4 figure
Investigation of unusual mortalities of bottlenose dolphins along the mid-Texas coastal bay ecosystem during 1992
An investigation was conducted into the deaths of more than 220 bottlenose dolphins (Tursiops truncatus) that occurred within the coastal bay ecosystem of mid-Texas between January and May 1992. The high mortality rate was unusual in that it was limited to a relatively small geographical area, occurred primarily within an inshore bay system separated from the Gulf of Mexico by barrier islands, and coincided with deaths of other taxa including birds and fish. Factors examined to determine the potential causes of the dolphin mortalities included microbial pathogens, natural biotoxins, industrial pollutants, other environmental contaminants, and direct human interactions. Emphasis was placed on nonpoint source pesticide runoff from agricultural areas, which had resulted from record rainfall that occurred during the period of increased mortality.
Analytical results from sediment, water, and biota indicated that biotoxins, trace metals, and industrial chemical contamination were not likely causative factors in this mortality event. Elevated concentrations of pesticides (atrazine and aldicarb) were detected in surface water samples from bays within the region, and bay salinities were reduced to <10 ppt from December 1991 through April 1992 due to record rainfall and freshwater runoff exceeding any levels since 1939. Prolonged exposure to low salinity could have played a significant role in the unusual mortalities because low salinity exposure may cause disruption of the permeability barrier in dolphin skin. The lack of established toxicity data for marine mammals, particularly dermal absorption and bioaccumulation, precludes accurate toxicological interpretation of results beyond a simple comparison to terrestrial mammalian models. Results clearly indicated that significant periods of agricultural runoff and accompanying low salinities co-occurred with the unusual mortality event in Texas, but no definitive cause of the mortalities was determined. (PDF file contains 25 pages.
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 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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