7,780 research outputs found
Morphological studies of the Spitzer Wide-Area Infrared Extragalactic survey galaxy population in the UGC 10214 Hubble space telescope/advanced camera for surveys field
We present the results of a morphological analysis of a small subset of the Spitzer Wide-Area Infrared Extragalactic survey (SWIRE) galaxy population. The analysis is based on public Advanced Camera for Surveys (ACS) data taken inside the SWIRE N1 field, which are the deepest optical high-resolution imaging available within the SWIRE fields as of today. Our reference sample includes 156 galaxies detected by both ACS and SWIRE. Among the various galaxy morphologies, we disentangle two main classes, spheroids (or bulge-dominated galaxies) and disc-dominated ones, for which we compute the number counts as a function of flux. We then limit our sample to objects with Infrared Array Camera (IRAC) fluxes brighter than 10 ÎŒJy, estimated ~90 per cent completeness limit of the SWIRE catalogues, and compare the observed counts to model predictions. We find that the observed counts of the spheroidal population agree with the expectations of a hierarchical model while a monolithic scenario predicts steeper counts. Both scenarios, however, underpredict the number of late-type galaxies. These observations show that the large majority (close to 80 per cent) of the 3.6- and 4.5-ÎŒm galaxy population, even at these moderately faint fluxes, is dominated by spiral and irregular galaxies or mergers
The dynamics of the ionized and molecular ISM in powerful obscured quasars at z>=3.5
We present an analysis of the kinematics and excitation of the warm ionized
gas in two obscured, powerful quasars at z>=3.5 from the SWIRE survey, SWIRE
J022513.90-043419.9 and SWIRE J022550.67-042142, based on imaging spectroscopy
on the VLT. Line ratios in both targets are consistent with luminous
narrow-line regions of AGN. SWIRE J022550.67-042142 has very broad (FWHM=2000
km/s), spatially compact [OIII] line emission. SWIRE J022513.90-043419.9 is
spatially resolved, has complex line profiles of H-beta and [OIII], including
broad wings with blueshifts of up to -1500 km/s relative to the narrow
[OIII]5007 component, and widths of up to FWHM=5000 km/s. Estimating the
systemic redshift from the narrow H-beta line, as is standard for AGN host
galaxies, implies that a significant fraction of the molecular gas is
blueshifted by up to ~ -1000 km/s relative to the systemic velocity. Thus the
molecular gas could be participating in the outflow. Significant fractions of
the ionized and molecular gas reach velocities greater than the escape
velocity. We compare empirical and modeling constraints for different energy
injection mechanisms, such as merging, star formation, and momentum-driven AGN
winds. We argue that the radio source is the most likely culprit, in spite of
the sources rather modest radio power of 10^25 W/Hz. Such a radio power is not
uncommon for intense starburst galaxies at z~2. We discuss these results in
light of the co-evolution of AGN and their host galaxy.Comment: Accepted by MNRA
The SWIRE SIRTF Legacy Program: Studying the Evolutionary Mass Function and Clustering of Galaxies
The SIRTF Wide-area Infrared Extragalactic (SWIRE) survey is a "Legacy
Program" using 851 hours of SIRTF observing time to conduct a set of large-area
(67 sq. deg. split into 7 fields) high Galactic latitude imaging surveys,
achieving 5-sigma sensitivities of 0.45/2.75/17.5 mJy at 24/70/160 micron with
MIPS and of 7.3/9.7/27.5/32.5 microJy at 3.6/4.5/5.8/8.0 micron with IRAC.
These data will yield highly uniform source catalogs and high-resolution
calibrated images, providing an unprecedented view of the universe on co-moving
scales up to several hundreds Mpc and to substantial cosmological depths
(z\simeq 2.5 for luminous sources). SWIRE will, for the first time, study
evolved stellar systems (from IRAC data) versus active star-forming systems and
AGNs (from MIPS data) in the same volume, generating catalogues with of order
of 2 million infrared-selected galaxies. These fields will have extensive data
at other wavebands, particularly in the optical, near-IR and X-rays. SWIRE will
provide a complement to smaller and deeper observations in the SIRTF Guaranteed
Time and the Legacy Program GOODS, by allowing the investigation of the effect
of environment on galaxy evolution. We expand here on capabilities of SWIRE to
study with IRAC the evolution of the bright end of the galaxy mass function as
a function of cosmic time.Comment: 6 pages, Latex, special macros. To appear in the Proceedings of the
ESO Workshop "The Mass of Galaxies at Low and High Redshift", R. Bender and
A. Renzini Eds., Springer-Verlag Series "ESO Astrophysics Symposia
Galaxy clusters at high redshift and evolution of brightest cluster galaxies
Identification of high redshift clusters is important for studies of
cosmology and cluster evolution. Using photometric redshifts of galaxies, we
identify 631 clusters from the Canada-France-Hawaii Telescope (CFHT) Wide
field, 202 clusters from the CHFT Deep field, 187 clusters from the Cosmic
Evolution Survey (COSMOS) and 737 clusters from the Spitzer Wide-area InfraRed
Extragalactic survey (SWIRE) field. The redshifts of these clusters are in the
range of 0.1<z<1.6. Merging these cluster samples gives 1644 clusters in the
four survey fields, of which 1088 are newly identified and more than half are
from the large SWIRE field. Among 228 clusters of z>1, 191 clusters are newly
identified, and most of them from the SWIRE field. With this large sample of
high redshift clusters, we study the color evolution of the brightest cluster
galaxies (BCGs). The colors r'-z' and r^+-m_{3.6\mu m} of the BCGs are
consistent with a stellar population synthesis model in which the BCGs are
formed at redshift z_f>2 and evolved passively. The colors g'-z' and
B-m_{3.6\mu m} of the BCGs at redshifts z>0.8 are systematically bluer than the
passive evolution model for galaxy formed at z_f~2, indicating star formation
in high redshift BCGs.Comment: 10 pages, 14 figures, 2 tables; added reference, corrected typos;
Table 2 is available at http://zmtt.bao.ac.cn/wzl/CV_wen.ht
Distant ULIRGs in the SWIRE Survey
Covering ~49 square degrees in 6 separate fields, the Spitzer Wide-area InfraRed Extragalactic (SWIRE) Legacy survey has the largest area among Spitzerâs âwedding cakeâ suite of extragalactic surveys. SWIRE is thus optimized for studies of large scale structure, population studies requiring excellent statistics, and searches for rare objects. We discuss the search for high redshift ultraluminous infrared galaxies (ULIRGs) with SWIRE. We have selected complete samples of F_(24ÎŒm) > 200 ÎŒJy, optically faint, candidate high redshift (z>1) ULIRGs, based on their mid-infrared spectral energy distributions (SEDs). These can be broadly categorized as star formation (SF)-dominated, based on the presence of a clear stellar peak at rest frame 1.6ÎŒm redshifted into the IRAC bands, or AGN-dominated if the SED rises featureless into the mid-infrared. AGN-dominated galaxies strongly dominate at the brightest 24ÎŒm fluxes, while SF-dominated objects rise rapidly in frequency as F_(24) drops, dominating the sample below 0.5 mJy. We derive photometric redshifts and luminosities for SFdominated objects sampling the z~1.2-3 range. Luminosity functions are being derived and compared with submm-selected samples at similar redshifts. The clustering, millimeter and IR spectral properties of the samples have also been investigated
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
MAMBO 1.2mm observations of luminous starbursts at z~2 in the SWIRE fields
We report on--off pointed MAMBO observations at 1.2 mm of 61 Spitzer-selected
star-forming galaxies from the SWIRE survey. The sources are selected on the
basis of bright 24um fluxes (f_24um>0.4mJy) and of stellar dominated
near-infrared spectral energy distributions in order to favor z~2 starburst
galaxies. The average 1.2mm flux for the whole sample is 1.5+/-0.2 mJy. Our
analysis focuses on 29 sources in the Lockman Hole field where the average
1.2mm flux (1.9+/-0.3 mJy) is higher than in other fields (1.1+/-0.2 mJy). The
analysis of the sources multi-wavelength spectral energy distributions
indicates that they are starburst galaxies with far-infrared luminosities
~10^12-10^13.3 Lsun, and stellar masses of ~0.2-6 x10^11 M_sun. Compared to
sub-millimeter selected galaxies (SMGs), the SWIRE-MAMBO sources are among
those with the largest 24um/millimeter flux ratios. The origin of such large
ratios is investigated by comparing the average mid-infrared spectra and the
stacked far-infrared spectral energy distributions of the SWIRE-MAMBO sources
and of SMGs. The mid-infrared spectra exhibit strong PAH features, and a warm
dust continuum. The warm dust continuum contributes to ~34% of the mid-infrared
emission, and is likely associated with an AGN component. This constribution is
consistent with what is found in SMGs. The large 24um/1.2mm flux ratios are
thus not due to AGN emission, but rather to enhanced PAH emission compared to
SMGs. The analysis of the stacked far-infrared fluxes yields warmer dust
temperatures than typically observed in SMGs. Our selection favors warm
ultra-luminous infrared sources at high-z, a class of objects that is rarely
found in SMG samples. Our sample is the largest Spitzer-selected sample
detected at millimeter wavelengths currently available.Comment: Accepted for publication in ApJ (51 pages; 16 figures). The quality
of some figures has been degraded for arXiv purposes. Full resolution version
available at this
http://www.iasf-milano.inaf.it/~polletta/mambo_swire/lonsdale08_ApJ_accepted.pd
Spitzer data at the NASA/IPAC Infrared Science Archive (IRSA)
The NASA/IPAC Infrared Science Archive (IRSA) curates and serves science
data sets from NASAâs infrared and submillimeter projects and missions,
including IRAS, 2MASS, MSX, SWAS, ISO, IRTS and from the Spitzer Space
Telescope. All Spitzer data can be accessed from IRSAâs Spitzer mission page
at: http://irsa.ipac.caltech.edu/Missions/spitzer.html
Spitzer Legacy Enhanced Products along with ancillary data are delivered
in six month intervals starting from Fall 2004, until Fall 2006. IRSA continually
ingests the Spitzer data and the ancillary data, and these data are made
accessible through IRSAâs query engines. Legacy products for the C2D, FEPS,
GLIMPSE, GOODS, SINGS and SWIRE projects are accessible through a common
interface http://irsa.ipac.caltech.edu/applications/Atlas. This
engine returns the spatial footprints of observations and provides access to all
flavors of released data sets, including, where appropriate, previews of image
mosaics, 3-color image mosaics and spectra
Understanding Infrared Galaxy Populations: the SWIRE Legacy Survey
We discuss spectral energy distributions, photometric redshifts, redshift
distributions, luminosity functions, source-counts and the far infrared to
optical luminosity ratio for sources in the SWIRE Legacy Survey. The spectral
energy distributions of selected SWIRE sources are modelled in terms of a
simple set of galaxy and quasar templates in the optical and near infrared, and
with a set of dust emission templates (cirrus, M82 starburst, Arp 220
starburst, and AGN dust torus) in the mid infrared. The optical data, together
with the IRAC 3.6 and 4.5 mu data, have been used to determine photometric
redshifts. For galaxies with known spectroscopic redshifts there is a notable
improvement in the photometric redshift when the IRAC data are used, with a
reduction in the rms scatter from 10% in (1+z) to 5%. While further
spectroscopic data are needed to confirm this result, the prospect of
determining good photometric redshifts for the 2 million extragalactic objects
in SWIRE is excellent. The distribution of the different infrared sed types in
the L{ir}/L{opt} versus L{ir} plane, where L{ir} and L{opt} are the infrared
and optical bolometric luminosities, is discussed. Source-counts at 24, 70 and
160 mu are discussed, and luminosity functions at 3.6 and 24 mu are presented.Comment: 8 pages, 14 figures, to appear in proceedings of 'Spitzer IR
Diagnostics Conference, Nov 14-16, 2005
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