1,801 research outputs found
Far-infrared photometric observations of the outer planets and satellites with Herschel-PACS
We present all Herschel PACS photometer observations of Mars, Saturn, Uranus,
Neptune, Callisto, Ganymede, and Titan. All measurements were carefully
inspected for quality problems, were reduced in a (semi-)standard way, and were
calibrated. The derived flux densities are tied to the standard PACS photometer
response calibration, which is based on repeated measurements of five fiducial
stars. The overall absolute flux uncertainty is dominated by the estimated 5%
model uncertainty of the stellar models in the PACS wavelength range between 60
and 210 micron. A comparison with the corresponding planet and satellite models
shows excellent agreement for Uranus, Neptune, and Titan, well within the
specified 5%. Callisto is brighter than our model predictions by about 4-8%,
Ganymede by about 14-21%. We discuss possible reasons for the model offsets.
The measurements of these very bright point-like sources, together with
observations of stars and asteroids, show the high reliability of the PACS
photometer observations and the linear behavior of the PACS bolometer source
fluxes over more than four orders of magnitude (from mJy levels up to more than
1000 Jy). Our results show the great potential of using the observed solar
system targets for cross-calibration purposes with other ground-based,
airborne, and space-based instruments and projects. At the same time, the PACS
results will lead to improved model solutions for future calibration
applications.Comment: 25 pages, 11 figures, 11 table
Spitzer Power-law AGN Candidates in the Chandra Deep Field-North
We define a sample of 62 galaxies in the Chandra Deep Field-North whose
Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of
luminous AGN. We study the multiwavelength properties of this sample, and
compare the AGN selected in this way to those selected via other Spitzer
color-color criteria. Only 55% of the power-law galaxies are detected in the
X-ray catalog at exposures of >0.5 Ms, although a search for faint emission
results in the detection of 85% of the power-law galaxies at the > 2.5 sigma
detection level. Most of the remaining galaxies are likely to host AGN that are
heavily obscured in the X-ray. Because the power-law selection requires the AGN
to be energetically dominant in the near- and mid-infrared, the power-law
galaxies comprise a significant fraction of the Spitzer-detected AGN population
at high luminosities and redshifts. The high 24 micron detection fraction also
points to a luminous population. The power-law galaxies comprise a subset of
color-selected AGN candidates. A comparison with various mid-infrared color
selection criteria demonstrates that while the color-selected samples contain a
larger fraction of the X-ray luminous AGN, there is evidence that these
selection techniques also suffer from a higher degree of contamination by
star-forming galaxies in the deepest exposures. Considering only those
power-law galaxies detected in the X-ray catalog, we derive an obscured
fraction of 68% (2:1). Including all of the power-law galaxies suggests an
obscured fraction of < 81% (4:1).Comment: Accepted for publication in the Astrophysical Journal, 27 pages, 20
figures, 5 tables, version with high-resolution figures and online-only
tables available at: http://frodo.as.arizona.edu/~jdonley/powerlaw
The far-infrared energy distributions of Seyfert and starburst galaxies in the Local Universe: ISO photometry of the 12 micron active galaxy sample
New far-infrared photometry with ISOPHOT, onboard the Infrared Space
Observatory, is presented for 58 galaxies with homogeneous published data for
another 32 galaxies all belonging to the 12 micron galaxy sample. In total 29
Seyfert 1's, 35 Seyfert 2's and 12 starburst galaxies, about half of the 12
micron active galaxy sample, plus 14 normal galaxies for comparison. The ISO
and the IRAS data are used to define color-color diagrams and spectral energy
distributions (SED). Thermal dust emission at two temperatures (one cold at
15-30K and one warm at 50-70K) can fit the 60-200 micron SED, with a dust
emissivity law proportional to the inverse square of the wavelength. Seyfert
1's and Seyfert 2's are indistinguishable longward of 100 micron, while, as
already seen by IRAS, the former have flatter SEDs shortward of 60 micron. A
mild anti-correlation is found between the [200 - 100] color and the "60 micron
excess". We infer that this is due to the fact that galaxies with a strong
starburst component, and thus a strong 60 micron flux, have a steeper
far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity
corresponds to increasing the star formation rate, that enhances the 25 and 60
micron emission. This shifts the peak emission from around 150 micron in the
most quiescent spirals to shorter than 60 micron in the strongest starburst
galaxies.Comment: Accepted for publication in The Astrophysical Journal AASTeX preprint
with 49 pages and 20 figures Also available at
http://orion.ifsi.rm.cnr.it/publ.htm
Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies
New high resolution interferometer data of 10 IR ultraluminous galaxies shows
the molecular gas is in rotating nuclear rings or disks with radii 300 to 800
pc. Most of the CO flux comes from a moderate-density, warm, intercloud medium
rather than self-gravitating clouds. Gas masses of ~ 5 x 10^9 Msun, 5 times
lower than the standard method are derived from a model of the molecular disks.
The ratio of molecular gas to dynamical mass, is M_gas/M_dyn ~ 1/6 with a
maximum ratio of gas to total mass surface density of 1/3. For the galaxies
VIIZw31, Arp193, and IRAS 10565+24, there is good evidence for rotating
molecular rings with a central gap. In addition to the rotating rings a new
class of star formation region is identified which we call an Extreme
Starburst. They have a characteristic size of only 100 pc., about 10^9 Msun of
gas and an IR luminosity of ~3 x 10^11 Lsun. Four extreme starbursts are
identified in the 3 closest galaxies in the sample Arp220, Arp193 and Mrk273.
They are the most prodigious star formation events in the local universe, each
representing about 1000 times as many OB stars as 30 Doradus. In Arp220, the CO
and 1.3 mm continuum maps show the two ``nuclei'' embedded in a central ring or
disk and a fainter structure extending 3 kpc to the east, normal to the nuclear
disk. There is no evidence that these sources really are the pre-merger nuclei.
They are compact, extreme starburst regions containing 10^9 Msun of dense
molecular gas and new stars, but no old stars. Most of the dust emission and
HCN emission arises in the two extreme starbursts. The entire bolometric
luminosity of Arp~220 comes from starbursts, not an AGN. In Mrk231, the disk
geometry shows that the molecular disk cannot be heated by the AGN; the far IR
luminosity of Mrk~231 is powered by a starburst, not the AGN. (Abridged)Comment: 97 pages Latex with aasms.sty, including 29 encapsulated Postscript
figures. Figs 18 and 23 are GIFs. 31 figures total. Text and higher quality
versions of figures available at
http://sbastk.ess.sunysb.edu/www/RINGS_ESB_PREPRINT.html To be published in
Ap. J., 10 Nov. 199
The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: IV. Cosmological Implications
In this paper we examine the cosmological constraints of the recent DIRBE and
FIRAS detection of the extragalactic background light between 125-5000 microns
on the metal and star formation histories of the universe.Comment: 38 pages and 9 figures. Accepted for publications in The
Astrophysical Journa
Dust in Spiral Galaxies: Comparing Emission and Absorption to Constrain Small-Scale and Very Cold Structures
The detailed distribution of dust in the disks of spiral galaxies is
important to understanding the radiative transfer within disks, and to
measuring overall dust masses if significant quantities of dust are either very
opaque or very cold. We address this issue by comparing measures of dust
absorption, using the galaxy-overlap technique in the optical, with measures of
the dust grains' thermal emission from 50-2000 micron using ISOPHOT on board
ISO and SCUBA at the JCMT. We examine three spiral galaxies projected partially
in front of E/S0 galaxies --- AM1316-241, NGC 5545, and NGC 5091 (for NGC 5091
we have only optical and ISO data). Adopting an empirical exponential model for
the dust distribution, we compare column densities and dust masses derived from
the absorption and emission techniques. This comparison is sensitive to the
amount of dust mass in small, opaque structures, which would not contribute
strongly to area-weighted absorption measures, and to very cold dust, which
would contribute to optical absorption but provide only a small fraction of the
sub-mm emission. In AM1316-241, we find global dust masses of 2-5 x 10^7
M_solar, both techniques agreeing at the 50% level. NGC 5545 has about half
this dust mass. The concordance of dust masses is well within the errors
expected from our knowledge of the radial distribution of dust, and argues
against any dominant part of the dust mass being so cold or opaque. The 50-2000
micron data are well fitted by modified Planck functions with an emissivity law
beta=-2, at 21 +/- 2 K. We also present 12 micron ISOCAM observations of these
pairs.Comparison of H-alpha and 12 micron images of NGC 5545 indicate that
ISOCAM images are reliable tracers of star formation.Comment: 16 pages, 4 tables, 8 figures, in press for October Astronomical
Journa
Pregnancy Outcomes:Effects of Metformin (POEM) study: a protocol for a long-term, multicentre, open-label, randomised controlled trial in gestational diabetes mellitus
INTRODUCTION: Gestational diabetes mellitus (GDM) is a common disorder of pregnancy with health risks for mother and child during pregnancy, delivery and further lifetime, possibly leading to type 2 diabetes mellitus (T2DM). Current treatment is focused on reducing hyperglycaemia, by dietary and lifestyle intervention and, if glycaemic targets are not reached, insulin. Metformin is an oral blood glucose lowering drug and considered safe during pregnancy. It improves insulin sensitivity and has shown advantages, specifically regarding pregnancy-related outcomes and patient satisfaction, compared with insulin therapy. However, the role of metformin in addition to usual care is inconclusive and long-term outcome of metformin exposure in utero are lacking. The primary aim of this study is to investigate the early addition of metformin on pregnancy and long-term outcomes in GDM. METHODS AND ANALYSIS: The Pregnancy Outcomes: Effects of Metformin study is a multicentre, open-label, randomised, controlled trial. Participants include women with GDM, between 16 and 32 weeks of gestation, who are randomised to either usual care or metformin added to usual care, with insulin rescue in both groups. Metformin is given up to 1âyear after delivery. The study consists of three phases (A-C): A-until 6 weeks after delivery; B-until 1âyear after delivery; C-observational study until 20 years after delivery. During phase A, the primary outcome is a composite score consisting of: (1) pregnancy-related hypertension, (2) large for gestational age neonate, (3) preterm delivery, (4) instrumental delivery, (5) caesarean delivery, (6) birth trauma, (7) neonatal hypoglycaemia, (8) neonatal intensive care admission. During phase B and C the primary outcome is the incidence of T2DM and (weight) development in mother and child. ETHICS AND DISSEMINATION: The study was approved by the Central Committee on Research Involving Human Subjects in the Netherlands. Results will be submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT02947503
Dust and gas in luminous infrared galaxies - results from SCUBA observations
We present new data taken at 850 m with SCUBA at the JCMT for a sample
of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used
these data, together with fluxes at 25, 60 and 100 m from IRAS, to model
the dust emission. We find that the emission from most galaxies can be
described by an optically thin, single temperature dust model with an exponent
of the dust extinction coefficient () of
. A lower is required to model the dust
emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various
possibilities for this difference and conclude that the most likely is a high
dust opacity. In addition, we compare the molecular gas mass derived from the
dust emission, , with the molecular gas mass derived from the CO
emission, , and find that is on average a factor 3 higher than
.Comment: 10 pages, 6 figures, latex, with MN-macros, accepted by MNRAS -
revised version (changed flux values for some galaxies
- âŠ