809 research outputs found
Optical Morphology Evolution of Infrared Luminous Galaxies in GOODS-N
We combine optical morphologies and photometry from HST, redshifts from Keck,
and mid-infrared luminosities from Spitzer for an optically selected sample
of~800 galaxies in GOODS-N to track morphology evolution of infrared luminous
galaxies (LIRGs) since redshift z=1. We find a 50% decline in the number of
LIRGs from z~1 to lower redshift, in agreement with previous studies. In
addition, there is evidence for a morphological evolution of the populations of
LIRGs. Above z=0.5, roughly half of all LIRGs are spiral, the
peculiar/irregular to spiral ratio is ~0.7, and both classes span a similar
range of L_{IR} and M_B. At low-z, spirals account for one-third of LIRGs, the
peculiar to spiral fraction rises to 1.3, and for a given M_B spirals tend to
have lower IR luminosity than peculiars. Only a few percent of LIRGs at any
redshift are red early-type galaxies. For blue galaxies (U-B < 0.2), M_B is
well correlated with log(L_{IR}) with an RMS scatter (about a bivariate linear
fit) of ~0.25 dex in IR luminosity. Among blue galaxies that are brighter than
M_B = -21, 75% are LIRGs, regardless of redshift. These results can be
explained by a scenario in which at high-z, most large spirals experience an
elevated star formation rate as LIRGs. Gas consumption results in a decline of
LIRGs, especially in spirals, to lower redshifts.Comment: 6 pages, 2 figures, accepted ApJ
NGC6240: extended CO structures and their association with shocked gas
We present deep CO observations of NGC6240 performed with the IRAM Plateau de
Bure Interferometer (PdBI). NGC6240 is the prototypical example of a major
galaxy merger in progress, caught at an early stage, with an extended,
strongly-disturbed butterfly-like morphology and the presence of a heavily
obscured active nucleus in the core of each progenitor galaxy. The CO line
shows a skewed profile with very broad and asymmetric wings detected out to
velocities of -600 km/s and +800 km/s with respect to the systemic velocity.
The PdBI maps reveal the existence of two prominent structures of blueshifted
CO emission. One extends eastward, i.e. approximately perpendicular to the line
connecting the galactic nuclei, over scales of ~7 kpc and shows velocities up
to -400 km/s. The other extends southwestward out to ~7 kpc from the nuclear
region, and has a velocity of -100 km/s with respect to the systemic one.
Interestingly, redshifted emission with velocities 400 to 800 km/s is detected
around the two nuclei, extending in the east-west direction, and partly
overlapping with the eastern blue-shifted structure, although tracing a more
compact region of size ~1.7 kpc. The overlap between the southwestern CO blob
and the dust lanes seen in HST images, which are interpreted as tidal tails,
indicates that the molecular gas is deeply affected by galaxy interactions. The
eastern blueshifted CO emission is co-spatial with an Halpha filament that is
associated with strong H2 and soft X-ray emission. The analysis of Chandra
X-ray data provides strong evidence for shocked gas at the position of the
Halpha emission. Its association with outflowing molecular gas supports a
scenario where the molecular gas is compressed into a shock wave that
propagates eastward from the nuclei. If this is an outflow, the AGN are likely
the driving force.Comment: Accepted for publication in A&
A New Method for ISOCAM Data Reduction - I. Application to the European Large Area ISO Survey Southern Field: Method and Results
We have developed a new data reduction technique for ISOCAM LW data and have
applied it to the European Large Area ISO Survey (ELAIS) LW3 (15 micron)
observations in the southern hemisphere (S1). This method, known as LARI
technique and based on the assumption of the existence of two different time
scales in ISOCAM transients (accounting either for fast or slow detector
response), was particularly designed for the detection of faint sources. In the
ELAIS S1 field we obtained a catalogue of 462 15 micron sources with
signal-to-noise ratio >= 5 and flux densities in the range 0.45 - 150 mJy
(filling the whole flux range between the Deep ISOCAM Surveys and the IRAS
Faint Source Survey). The completeness at different flux levels and the
photometric accuracy of this catalogue have been tested with simulations. Here
we present a detailed description of the method and discuss the results
obtained by its application to the S1 LW3 data.Comment: 20 pages, LaTeX, MNRAS style, 20 postscript figures, full catalogue
not yet available at http://boas5.bo.astro.it/~elais/catalogues/. Accepted
for publication in MNRA
NIR Spectroscopy with the VLT of a sample of ISO selected Hubble Deep Field South Galaxies
A new population of faint galaxies characterized by an extremely high rate of
evolution with redshift up to z~1.5 has recently been discovered by ISO. These
sources are likely to contribute significantly to the cosmic far-IR
extragalactic background. We have carried out near-infrared VLT-ISAAC
spectroscopy of a sample of ISOCAM galaxies from the Hubble Deep Field South.
The rest-frame R-band spectral properties of the ISO population resembles that
of powerful dust-enshrouded active starburst galaxies.Comment: 8 pages, 3 figures, to appear in "ISO Surveys of a Dusty Universe",
eds. D. Lemke, M. Stickel, K. Wilke, typos correcte
CEA Bolometer Arrays: the First Year in Space
The CEA/LETI and CEA/SAp started the development of far-infrared filled bolometer arrays for space applications
over a decade ago. The unique design of these detectors makes possible the assembling of large focal planes
comprising thousands of bolometers running at 300 mK with very low power dissipation. Ten arrays of 16x16
pixels were thoroughly tested on the ground, and integrated in the Herschel/PACS instrument before launch in
May 2009. These detectors have been successfully commissioned and are now operating in their nominal environment
at the second Lagrangian point of the Earth-Sun system. In this paper we briefly explain the functioning
of CEA bolometer arrays, and we present the properties of the detectors focusing on their noise characteristics,
the effect of cosmic rays on the signal, the repeatability of the measurements, and the stability of the system
The VLA-COSMOS Survey. II. Source Catalog of the Large Project
The VLA-COSMOS Large Project is described and its scientific objective is discussed. We present a catalog of ~3600 radio sources found in the 2 deg^2 COSMOS field at 1.4 GHz. The observations in the VLA A and C configuration resulted in a resolution of 1.5" Ă 1.4" and a mean rms noise of ~10.5 (15) ÎŒJy beam^(-1) in the central 1 (2) deg^2. Eighty radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested, and the uncertainty in the relative and absolute astrometry are 130 and <55 mas, respectively
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