168 research outputs found
The European Large Area ISO Survey: ELAIS
The European Large Area ISO Survey (ELAIS) has surveyed 12 square degrees of
the sky at 15 and 90 microns, and subsets of this area at 6.75 and 175 microns,
using the Infrared Space Observatory (ISO). This project was the largest single
open time programme executed by ISO, taking 375 hours of data. A preliminary
catalogue of more than 1000 galaxies has been produced. In this talk we
describe the goals of the project, describe the follow-up programmes that are
in progress, and present some first scientific results including a provisional
number count analysis at 15 and 90 microns.Comment: 5 pages, 3 figures, 4 tables, to appear in 'The universe as seen by
ISO', eds P.Cox and M.F.Kessler, 1998, UNESCO, Paris, ESA Special
Publications Series (SP-427
The HELLAS2XMM survey. X. The bolometric output of luminous obscured quasars: The Spitzer perspective
Aims: We aim at estimating the spectral energy distributions (SEDs) and the
physical parameters related to the black holes harbored in eight high
X-ray-to-optical (F_X/F_R>10) obscured quasars at z>0.9 selected in the 2--10
keV band from the HELLAS2XMM survey.
Methods: We use IRAC and MIPS 24 micron observations, along with optical and
Ks-band photometry, to obtain the SEDs of the sources. The observed SEDs are
modeled using a combination of an elliptical template and torus emission (using
the phenomenological templates of Silva et al. 2004) for six sources associated
with passive galaxies; for two point-like sources, the empirical SEDs of red
quasars are adopted. The bolometric luminosities and the M_BH-L_K relation are
used to provide an estimate of the masses and Eddington ratios of the black
holes residing in these AGN.
Results: All of our sources are detected in the IRAC and MIPS (at 24 micron)
bands. The SED modeling described above is in good agreement with the observed
near- and mid-infrared data. The derived bolometric luminosities are in the
range ~10^45-10^47 erg s^-1, and the median 2--10 keV bolometric correction is
~25, consistent with the widely adopted value derived by Elvis et al. (1994).
For the objects with elliptical-like profiles in the K_s band, we derive high
stellar masses (0.8-6.2)X10^11 Mo, black hole masses in the range
(0.2-2.5)X10^9 Mo, and Eddington ratios L/L_Edd<0.1, suggesting a low-accretion
phase.Comment: 12 pages, 6 figures, A&A accepted. Typo corrected in the titl
Interaction of alcohol intake and cofactors on the risk of cirrhosis.
OBJECTIVE: Evaluation of the interaction between alcohol intake and cofactors [hepatitis B virus (HBV), hepatitis C virus (HCV), body mass index] and coffee consumption on the risk of cirrhosis.
DESIGN: Seven hundred and forty-nine consecutive patients with chronic liver disease referring to units for liver or alcohol diseases in Italy during a 6-months period. Teetotalers were excluded. The odds ratios (OR) for cirrhosis were evaluated using chronic hepatitis cases as the control group.
RESULTS: An alcohol intake of more than 3 units/day resulted associated with the likelihood of cirrhosis both in males (OR 4.3; 95% CI=2.5-7.3) and in females (OR 5.7; 95% CI=2.3-14.5). A multiplicative interaction on the risk of cirrhosis between risky alcohol intake and HBsAg or HCV-Ab/HCV-RNA positivity was observed. A reduction of cirrhosis risk was observed in subjects consuming more than 3 alcohol units/day with increasing coffee intake. The OR for the association with cirrhosis decreased from 2.3 (95% CI=1.2-4.4) in subjects drinking 0-2 cups of coffee/day to 1.4 (95% CI=0.6-3.6) in those drinking more than 2 cups/day.
CONCLUSIONS: In subjects with an alcohol intake >3 units/day the coexistence of HBV or HCV multiplies the risk of cirrhosis. Coffee represents a modulator of alcoholic cirrhosis risk
Diabetes and endometrial cancer: an Italian case-control study
We considered the association between diabetes and risk of endometrial cancer using data from a large case-control study conducted in Italy. Cases were 752 women with incident, histologically confirmed endometrial cancer or = 40 years. The OR of endometrial cancer in women with history of diabetes was 3.0 for women with a body mass index (BMI) (QI) kg/m2 or = 30. No consistent interaction or modifying effect was observed for any other covariate. Our results confirm that non-insulin-dependent diabetes is associated with the risk of endometrial cancer. The association may be mediated through elevated oestrogen levels in diabetic women, hyperinsulinemia or insulin-like growth factor-I (IGF-I)
The Contribution of AGN and Star-Forming Galaxies to the Mid-Infrared as Revealed by their Spectral Energy Distributions
We present the broad-band Spectral Energy Distributions (SEDs) of the largest
available highly (72%) complete spectroscopic sample of mid-infrared (MIR)
selected galaxies and AGN at intermediate redshift. The sample contains 203
extragalactic sources from the 15-micron survey in the ELAIS-SWIRE field S1,
all with measured spectroscopic redshift. Most of these sources have full
multi-wavelength coverage from the far-UV to the far-infrared and lie in the
redshift range 0.1<z<1.3. Due to its size, this sample allows us for the first
time to characterise the spectral properties of the sources responsible for the
strong evolution observed in the MIR. Based on SED-fitting technique we have
classified the MIR sources, identifying AGN signatures in about 50% of them.
This fraction is significantly higher than that derived from optical
spectroscopy (~29%) and is due in particular to the identification of AGN
activity in objects spectroscopically classified as galaxies. It is likely that
in most of our objects, the AGN is either obscured or of low-luminosity, and
thus it does not dominate the energetic output at any wavelength, except in the
MIR, showing up just in the range where the host galaxy SED has a minimum. The
fraction of AGN strongly depends on the flux density, with that derived through
the SED-fitting being about 20% at S(15)~0.5-1 mJy and gradually increasing up
to 100% at S(15)>10 mJy, while that obtained from optical spectroscopy never
being >30%, even at the higher flux densities. The results of this work will be
very useful for updating all the models aimed at interpreting the deep infrared
survey data and, in particular, for constraining the nature and the role of
dust-obscured systems in the intermediate/high-redshift Universe.Comment: Accepted for publication in The Astrophysical Journal. Scheduled for
the ApJ August 20, 2008, v683 n 2 issue. 33 pages: 22 pages of main text + 2
tables + 6 postscript figures, use aaste
The European Large Area ISO Survey IX: the 90 micron luminosity function from the Final Analysis sample
We present the 90 micron luminosity function of the Final Analysis of the
European Large Area ISO Survey (ELAIS), extending the sample size of our
previous analysis (paper IV) by about a factor of 4. Our sample extends to
z=1.1, around 50 times the comoving volume of paper IV, and 10^{7.7} <
h^{-2}L/Lsun < 10^{12.5}. From our optical spectroscopy campaigns of the
northern ELAIS 90 mircon survey (7.4 deg^2 in total, to S(90um)>70mJy), we
obtained redshifts for 61% of the sample (151 redshifts) to B<21 identified at
7 microns, 15 microns, 20cm or with bright (B<18.5) optical identifications.
The selection function is well-defined, permitting the construction of the 90
micron luminosity function of the Final Analysis catalogue in the ELAIS
northern fields, which is in excellent agreement with our Preliminary Analysis
luminosity function in the ELAIS S1 field from paper IV. The luminosity
function is also in good agreement with the IRAS-based prediction of Serjeant &
Harrison (2004), which if correct requires luminosity evolution of (1+z)^{3.4
+/- 1.0} for consistency with the source counts. This implies an evolution in
comoving volume averaged star formation rate at z<~1 consistent with that
derived from rest-frame optical and ultraviolet surveys.Comment: MNRAS accepted. 7 pages, 5 figures. Uses BoxedEPS (included
Mid- and Far-infrared Luminosity Functions and Galaxy Evolution from Multiwavelength Spitzer Observations up to z~2.5
[Abridged]We exploit a large homogeneous dataset to derive a self-consistent
picture of IR emission based on the time-dependent 24, 15, 12 and 8micron
monochromatic and bolometric IR luminosity functions (LF) over the 0<z<2.5
redshift range. Our analysis is based on the combination of data from deep
Spitzer surveys in the VVDS-SWIRE and GOODS areas. To our limiting flux of
S(24)=400microJy our derived sample in VVDS-SWIRE includes 1494 sources, and
666 and 904 sources brighter than S(24)=80microJy are catalogued in GOODS-S and
GOODS-N, respectively, for a total area of ~0.9 square degs. We obtain reliable
optical identifications and redshifts, providing us a rich and robust dataset
for our luminosity function determination. Based on the multi-wavelength
information available, we constrain the LFs at 8, 12, 15 and 24micron. We also
extrapolate total IR luminosities from our best-fit to the observed SEDs of
each source, and use this to derive the bolometric LF and comoving volume
emissivity up to z~2.5. In the 0<z<1 interval, the bolometric IR luminosity
density evolves as (1+z)^3.8+/-0.4. Although more uncertain at higher-z, our
results show a flattening of the IR luminosity density at z>1. The mean
redshift of the peak in the source number density shifts with luminosity: the
brighest IR galaxies appear to be forming stars earlier in cosmic time (z>1.5),
while the less luminous ones keep doing it at more recent epochs (z~1 for
L(IR)<10^11L_sun). Our results suggest a rapid increase of the galaxy IR
comoving volume emissivity back to z~1 and a constant average emissivity at
z>1. We also seem to find a difference in the evolution rate of the source
number densities as a function of luminosity, a downsizing evolutionary pattern
similar to that reported from other samples of cosmic sources.Comment: Accepted for pubblicantion in Astronomy and Astrophysic
The VVDS type-1 AGN sample: The faint end of the luminosity function
In a previous paper (Gavignaud et al. 2006), we presented the type-1 Active
Galactic Nuclei (AGN) sample obtained from the first epoch data of the
VIMOS-VLT Deep Survey (VVDS). The sample consists of 130 faint, broad-line AGN
with redshift up to z=5 and 17.5< I <24.0, selected on the basis of their
spectra. In this paper we present the measurement of the Optical Luminosity
Function up to z=3.6 derived from this sample, we compare our results with
previous results from brighter samples both at low and at high redshift. Our
data, more than one magnitude fainter than previous optical surveys, allow us
to constrain the faint part of the luminosity function up to high redshift. By
combining our faint VVDS sample with the large sample of bright AGN extracted
from the SDSS DR3 (Richards et al., 2006b) and testing a number of different
evolutionary models, we find that the model which better represents the
combined luminosity functions, over a wide range of redshift and luminosity, is
a luminosity dependent density evolution (LDDE) model, similar to those derived
from the major X-surveys. Such a parameterization allows the redshift of the
AGN space density peak to change as a function of luminosity and explains the
excess of faint AGN that we find at 1.0< z <1.5. On the basis of this model we
find, for the first time from the analysis of optically selected samples, that
the peak of the AGN space density shifts significantly towards lower redshift
going to lower luminosity objects. This result, already found in a number of
X-ray selected samples of AGN, is consistent with a scenario of "AGN cosmic
downsizing", in which the density of more luminous AGN, possibly associated to
more massive black holes, peaks earlier in the history of the Universe, than
that of low luminosity ones.Comment: 13 pages, 10 figures, submitted to A&
Optical and Infrared Diagnostics of SDSS galaxies in the SWIRE Survey
We present the rest-frame optical and infrared colours of a complete sample
of 1114 z<0.3 galaxies from the Spitzer Wide-area InfraRed Extragalactic Legacy
Survey (SWIRE) and the Sloan Digital Sky Survey (SDSS). We discuss the optical
and infrared colours of our sample and analyse in detail the contribution of
dusty star-forming galaxies and AGN to optically selected red sequence
galaxies.
We propose that the optical (g-r) colour and infrared log(L_{24}/L_{3.6})
colour of galaxies in our sample are determined primarily by a bulge-to-disk
ratio. The (g-r) colour is found to be sensitive to the bulge-to-disk ratio for
disk-dominated galaxies, whereas the log(L_{24}/L_{3.6}) colour is more
sensitive for bulge-dominated systems.
We identify ~18% (195 sources) of our sample as having red optical colours
and infrared excess. Typically, the infrared luminosities of these galaxies are
found to be at the high end of star-forming galaxies with blue optical colours.
Using emission line diagnostic diagrams, 78 are found to have an AGN
contribution, and 117 are identified as star-forming systems. The red (g-r)
colour of the star-forming galaxies could be explained by extinction. However,
their high optical luminosities cannot. We conclude that they have a
significant bulge component.
The number densities of optically red star-forming galaxies are found to
correspond to ~13% of the total number density of our sample. In addition,
these systems contribute ~13% of the total optical luminosity density, and 28%
of the total infrared luminosity density of our SWIRE/SDSS sample. These
objects may reduce the need for "dry-mergers".Comment: 14 pages, 8 figures, 4 tables. Accepted for publication in MNRA
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