11 research outputs found
The spatial clustering of ultraluminous infrared galaxies over 1.5 < z < 3
We present measurements of the spatial clustering of galaxies with stellar masses 1011 M, infrared luminosities 1012 L, and star formation rates 200 M yr-1 in two redshift intervals: 1.5 < z < 2.0 and 2 < z < 3. Both samples cluster moderately strongly, with spatial correlation lengths of r0 = 6.14 B1 0.84 h-1 Mpc for the 2 < z < 3 sample and r0 = 5.36 B1 1.28 h-1 Mpc for the 1.5 < z < 2.0 sample. These clustering amplitudes are consistent with both populations residing in dark matter halos with masses of 7 C 1012 M, which is comparable to that seen for optical QSOs at the same epochs. We infer that a minimum dark matter halo mass is an important factor for all forms of luminous, obscured activity in galaxies at z > 1, both starbursts and active galactic nuclei. Adopting plausible models for the growth of dark matter halos with redshift, the halos hosting the 2 < z < 3 sample will likely host poor to rich clusters of galaxies at z = 0, whereas the halos hosting the 1.5 < z < 2.0 sample will likely host L* elliptical galaxies or poor clusters at z = 0. We conclude that ultraluminous infrared galaxies (ULIRGs) at z 2.5 likely signpost stellar buildup in galaxies that will reside in clusters at z = 0 and that ULIRGs at z 1.7 signpost stellar buildup in sources that will either become L* elliptical galaxies or reside in poor clusters at z = 0
A Deep 1.2 mm Map of the Lockman Hole North Field
We present deep 1.2 mm continuum mapping of a 566 arcmin^2 area within the
Lockman Hole North field, previously a target of the Spitzer Wide-area Infrared
Extragalactic (SWIRE) survey and extremely deep 20 cm mapping with the Very
Large Array, which we have obtained using the Max-Planck millimeter bolometer
(MAMBO) array on the IRAM 30 m telescope. After filtering, our full map has an
RMS sensitivity ranging from 0.45 to 1.5 mJy/beam, with an average of 0.75
mJy/beam. Using the pixel flux distribution in a map made from our best data,
we determine the shape, normalization, and approximate flux density cutoff for
1.2 mm number counts well below our nominal sensitivity and confusion limits.
After validating our full dataset through comparison with this map, we
successfully detect 41 1.2 mm sources with S/N > 4.0 and S(1.2 mm)\simeq 2-5
mJy. We use the most significant of these detections to directly determine the
integral number counts down to 1.8 mJy, which are consistent with the results
of the pixel flux distribution analysis. 93% of our 41 individual detections
have 20 cm counterparts, 49% have Spitzer/MIPS 24 micron counterparts, and one
may have a significant Chandra X-ray counterpart. We resolve \simeq 3% of the
cosmic infrared background (CIB) at 1.2 mm into significant detections, and
directly estimate a 0.05 mJy faint-end cutoff for the counts that is consistent
with the full intensity of the 1.2 mm CIB. The median redshift of our 17
detections with spectroscopic or robust photometric redshifts is z(median)=2.3,
and rises to z(median)=2.9 when we include redshifts estimated from the
radio/far-infrared spectral index. By using a nearest neighbor and angular
correlation function analysis, we find evidence that our S/N>4.0 detections are
clustered at the 95% confidence level.Comment: 40 pages, 25 figures, accepted for publication in Ap
Deep ATLAS radio observations of the CDFS-SWIRE field
We present the first results from the Australia Telescope Large Area Survey
(ATLAS), which consist of deep radio observations of a 3.7 square degree field
surrounding the Chandra Deep Field South, largely coincident with the infrared
Spitzer Wide-Area Extragalactic (SWIRE) Survey. We also list
cross-identifications to infrared and optical photometry data from SWIRE, and
ground-based optical spectroscopy. A total of 784 radio components are
identified, corresponding to 726 distinct radio sources, nearly all of which
are identified with SWIRE sources. Of the radio sources with measured
redshifts, most lie in the redshift range 0.5-2, and include both star-forming
galaxies and active galactic nuclei (AGN). We identify a rare population of
infrared-faint radio sources which are bright at radio wavelengths but are not
seen in the available optical, infrared, or X-ray data. Such rare classes of
sources can only be discovered in wide, deep surveys such as this.Comment: Accepted by A
Photometric redshifts in the SWIRE Survey
We present the SWIRE Photometric Redshift Catalogue, 1025119 redshifts of
unprecedented reliability and accuracy. Our method is based on fixed galaxy and
QSO templates applied to data at 0.36-4.5 mu, and on a set of 4 infrared
emission templates fitted to infrared excess data at 3.6-170 mu. The code
involves two passes through the data, to try to optimize recognition of AGN
dust tori. A few carefully justified priors are used and are the key to
supression of outliers. Extinction, A_V, is allowed as a free parameter. We use
a set of 5982 spectroscopic redshifts, taken from the literature and from our
own spectroscopic surveys, to analyze the performance of our method as a
function of the number of photometric bands used in the solution and the
reduced chi^2. For 7 photometric bands the rms value of
(z_{phot}-z_{spec})/(1+z_{spec}) is 3.5%, and the percentage of catastrophic
outliers is ~1%.
We discuss the redshift distributions at 3.6 and 24 mu. In individual fields,
structure in the redshift distribution corresponds to clusters which can be
seen in the spectroscopic redshift distribution. 10% of sources in the SWIRE
photometric redshift catalogue have z >2, and 4% have z>3, so this catalogue is
a huge resource for high redshift galaxies.
A key parameter for understanding the evolutionary status of infrared
galaxies is L_{ir}/L_{opt}, which can be interpreted as the specific
star-formation rate for starbursts. For dust tori around Type 1 AGN,
L_{tor}/L_{opt} is a measure of the torus covering factor and we deduce a mean
covering factor of 40%.Comment: 22 pages, 23 figures. Accepted for publication in MNRAS. Revised
28/2/08. Version with figures at full resolution at
http://astro.ic.ac.uk/~mrr/swirephotzcat/swirephotz5.pdf.g
Paper 1: The JWST PEARLS View of the El Gordo Galaxy Cluster and of the Structure It Magnifies
The massive galaxy cluster El Gordo (z=0.87) imprints multitudes of
gravitationally lensed arcs onto James Webb Space Telescope (JWST)
Near-Infrared Camera (NIRCam) images. Eight bands of NIRCam imaging were
obtained in the ``Prime Extragalactic Areas for Reionization and Lensing
Science'' (``PEARLS'') program. PSF-matched photometry across Hubble Space
Telescope (HST) and NIRCam filters supplies new photometric redshifts. A new
light-traces-mass lens model based on 56 image multiplicities identifies the
two mass peaks and yields a mass estimate within 500 kpc of ~(7.0 +/- 0.30) x
10^14 Msun. A search for substructure in the 140 cluster members with
spectroscopic redshifts confirms the two main mass components. The southeastern
mass peak that contains the BCG is more tightly bound than the northwestern
one. The virial mass within 1.7 Mpc is (5.1 +/- 0.60) x 10^14 Msun, lower than
the lensing mass. A significant transverse velocity component could mean the
virial mass is underestimated. We contribute one new member to the previously
known z=4.32 galaxy group. Intrinsic (delensed) positions of the five secure
group members span a physical extent of ~60 kpc. Thirteen additional candidates
selected by spectroscopic/photometric constraints are small and faint with a
mean intrinsic luminosity ~2.2 mag fainter than L*. NIRCam imaging admits a
fairly wide range of brightnesses and morphologies for the group members,
suggesting a more diverse galaxy population in this galaxy overdensity.Comment: 24 pages, accepted by Ap
Synthesis, anti-Candida activity, and cytotoxicity of new (4-(4-iodophenyl)thiazol-2-yl)hydrazine derivatives
Novel (4-(4-iodophenyl)-thiazol-2-yl)hydrazine derivatives were assayed for their in vitro anti-Candida activity, compared to topical and systemic antifungal drugs, against twenty-seven clinical isolates. The presence of aliphatic chains or specific heteroaromatic rings on hydrazone moiety at position C2 and a 4-iodophenyl at C4 of the thiazole ring gave a promising inhibitory activity especially against Candida albicans and Candida krusei. The most active compounds have been also evaluated for their cytotoxicity and in association with clotrimazole for anti-Candida activity. (C) 2012 Elsevier Masson SAS. All rights reserved
Deep ATLAS radio observations of the CDFS-SWIRE field
We present the first results from the Australia Telescope Large Area Survey (ATLAS), which consist of deep radio observations of a 3.7 square degree field surrounding the Chandra Deep Field South, largely coincident with the infrared Spitzer Wide-Area Extragalactic (SWIRE) Survey. We also list cross-identifications to infrared and optical photometry data from SWIRE, and groundbased optical spectroscopy. A total of 784 radio components are identified, corresponding to 726 distinct radio sources, nearly all of which are identified with SWIRE sources. Of the radio sources with measured redshifts, most lie in the redshift range 0.5-2, and include both star-forming galaxies and active galactic nuclei (AGN). We identify a rare population of infrared-faint radio sources which are bright at radio wavelengths but are not seen in the available optical, infrared, or X-ray data. Such rare classes of sources can only be discovered in wide, deep surveys such as this. Subject headings: Catalogs--- surveys--- radio continuum: galaxies--- galaxies: evolution---galaxies: activ