1,506 research outputs found
Modeling the evolution of infrared luminous galaxies: the influence of the Luminosity-Temperature distribution
The evolution of the luminous infrared galaxy population is explored using a
pure luminosity evolution model which incorporates the locally observed
luminosity-temperature distribution for IRAS galaxies. Pure luminosity
evolution models in a fixed CDM cosmology are fitted to submillimeter
(submm) and infrared counts, and backgrounds. It is found that the differences
between the locally determined bivariate model and the single variable
luminosity function (LF) do not manifest themselves in the observed counts, but
rather are primarily apparent in the dust temperatures of sources in flux
limited surveys. Statistically significant differences in the redshift
distributions are also observed. The bivariate model is used to predict the
counts, redshifts and temperature distributions of galaxies detectable by {\it
Spitzer}. The best fitting model is compared to the high-redshift submm galaxy
population, revealing a median redshift for the total submm population of
, in good agreement with recent spectroscopic studies of
submillimeter galaxies. The temperature distribution for the submm galaxies is
modeled to predict the radio/submm indices of the submm galaxies, revealing
that submm galaxies exhibit a broader spread in spectral energy distributions
than seen in the local IRAS galaxies.Comment: Accepted for publication in ApJ. Quality of several figures reduced
due to size restriction
Hubble Space Telescope images of submillimeter sources: large, irregular galaxies at high redshift
We present new Hubble Space Telescope STIS, high-resolution optical imaging
of a sample of 13 submillimeter (submm) luminous galaxies, for which the
optical emission has been pinpointed either through radio-1.4 GHz or millimeter
interferometry. We find a predominance of irregular and complex morphologies in
the sample, suggesting that mergers are likely common for submm galaxies. The
component separation in these objects are on average a factor two larger than
local galaxies with similarly high bolometric luminosities. The sizes and star
formation rates of the submm galaxies are consistent with the maximal star
formation rate densities of 20 Msun kpc^{-2} in local starburst galaxies
(Lehnert & Heckman 1996). We derive quantitative morphological information for
the optical galaxies hosting the submm emission; total and isophotal
magnitudes, Petrosian radius, effective radius, concentration, aspect ratio,
surface brightness, and asymmetry. We compare these morphological indices with
those of other galaxies lying within the same STIS images. Most strikingly, we
find ~70% of the submm galaxies to be extraordinarily large and elongated
relative to the field population, regardless of optical magnitude. Comparison
of the submm galaxy morphologies with those of optically selected galaxies at
z~2-3 reveal the submm galaxies to be a morphologically distinct population,
with generally larger sizes, higher concentrations and more prevalent
major-merger configurations.Comment: 16 pages, 6 figures, scheduled for ApJ, v599, Dec10, 2003. Minor
edits. For version with higher resolution figures, see
http://www.submm.caltech.edu/~schapman/ms_v3.ps.g
AKARI-CAS --- Online Service for AKARI All-Sky Catalogues
The AKARI All-Sky Catalogues are an important infrared astronomical database
for next-generation astronomy that take over the IRAS catalog. We have
developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for
astronomers. The service includes useful and attractive search tools and visual
tools.
One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can
match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow
advanced queries to the databases, direct input of SQL is also supported. In
those queries, fast dynamic cross-identification between registered catalogs is
a remarkable feature. In addition, multiwavelength quick-look images are
displayed in the visualization tools, which will increase the value of the
service.
In the construction of our service, we considered a wide variety of
astronomers' requirements. As a result of our discussion, we concluded that
supporting users' SQL submissions is the best solution for the requirements.
Therefore, we implemented an RDBMS layer so that it covered important
facilities including the whole processing of tables. We found that PostgreSQL
is the best open-source RDBMS products for such purpose, and we wrote codes for
both simple and advanced searches into the SQL stored functions. To implement
such stored functions for fast radial search and cross-identification with
minimum cost, we applied a simple technique that is not based on dividing
celestial sphere such as HTM or HEALPix. In contrast, the Web application layer
became compact, and was written in simple procedural PHP codes. In total, our
system realizes cost-effective maintenance and enhancements.Comment: Yamauchi, C. et al. 2011, PASP..123..852
A Deep WSRT 1.4 GHz Radio Survey of the Spitzer Space Telescope FLSv Region
The First Look Survey (FLS) is the first scientific product to emerge from
the Spitzer Space Telescope. A small region of this field (the verification
strip) has been imaged very deeply, permitting the detection of cosmologically
distant sources. We present Westerbork Synthesis Radio Telescope (WSRT)
observations of this region, encompassing a ~1 sq. deg field, centred on the
verification strip (J2000 RA=17:17:00.00, DEC=59:45:00.000). The radio images
reach a noise level of ~ 8.5 microJy/beam - the deepest WSRT image made to
date. We summarise here the first results from the project, and present the
final mosaic image, together with a list of detected sources. The effect of
source confusion on the position, size and flux density of the faintest sources
in the source catalogue are also addressed. The results of a serendipitous
search for HI emission in the field are also presented. Using a subset of the
data, we clearly detect HI emission associated with four galaxies in the
central region of the FLSv. These are identified with nearby, massive galaxies.Comment: 9 pages, 6 figures (fig.3 in a separate gif file). Accepted for
publication in A&A. The full paper and the related material can be downloaded
from http://www.astron.nl/wsrt/WSRTsurveys/WFLS
Benchmark between antenna code TOPICA, RAPLICASOL and Petra-M for the ICRH ITER antenna
ITER will be equipped with three plasma heating systems: neutral beam (NB), electron cyclotron (EC), and ion cy-clotron resonance heating (ICRH). The latter consists of two identical ICRH antennas to deliver 20 MW to the plasma (baseline, upgradable to 40 MW). ICRH will play a crucial role in the ignition and sustainment of burning plasmas in ITER. A high fidelity and robust modeling effort to understand the interaction of the IC waves with the scrape-off-layer (SOL) plasma is a very important aspect. Among the main important research topics, we have the assessment of the antenna loading for different plasma scenarios, the role of the lower hybrid resonance in front of the antenna and how to include it in our models, and the RF sheath boundary conditions to evaluate the antenna impurity generation. In this work, we tackle the first of these by reporting on ICRF simulations employing the Petra-M code, which is an electromagnetic simulation tool for modeling RF wave propagation based on MFEM [http://mfem.org] for the ITER ICRH antenna. Moreover, a benchmark between the well tested antenna codes TOPICA, RAPLI-CASOL, which is based on COMSOL [www.comsol.com], and the Petra-M code is also presented. S- and Z-matrices and wave electric field are compared showing an excellent agreement among these codes
Microwave Continuum Emission and Dense Gas Tracers in NGC 3627: Combining Jansky VLA and ALMA Observations
We present Karl G. Jansky Very Large Array (VLA) Ka band (33 GHz) and Atacama
Large Millimeter Array (ALMA) Band 3 (94.5 GHz) continuum images covering the
nucleus and two extranuclear star-forming regions within the nearby galaxy NGC
3627 (M 66), observed as part of the Star Formation in Radio Survey (SFRS).
Both images achieve an angular resolution of 2\arcsec, allowing us to
map the radio spectral indices and estimate thermal radio fractions at a linear
resolution of 90 pc at the distance of NGC 3627. The thermal fraction
at 33 GHz reaches unity at and around the peaks of each HII region; we
additionally observed the spectral index between 33 and 94.5 GHz to become both
increasingly negative and positive away from the peaks of the HII regions,
indicating an increase of non-thermal extended emission from diffusing
cosmic-ray electrons and the possible presence of cold dust, respectively.
While the ALMA observations were optimized for collecting continuum data, they
also detected line emission from the transitions of HCN and
HCO. The peaks of dense molecular gas traced by these two spectral lines
are spatially offset from the peaks of the 33 and 94.5 GHz continuum emission
for the case of the extranuclear star-forming regions, indicating that our data
reach an angular resolution at which one can spatially distinguish sites of
recent star formation from the sites of future star formation. Finally, we find
trends of decreasing dense gas fraction and velocity dispersion with increasing
star formation efficiency among the three regions observed, indicating that the
dynamical state of the dense gas, rather than its abundance, plays a more
significant role in the star formation process.Comment: 9 pages, 5 figures, accepted for publication in Ap
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