1,062 research outputs found
High resolution near-infrared imaging of submillimeter galaxies
We present F110W (~J) and F160W (~H) observations of ten submillimeter
galaxies (SMGs) obtained with the Hubble Space Telescope's (HST's) NICMOS
camera. Our targets have optical redshifts in the range 2.20<z<2.81 confirmed
by millimeter CO or mid-IR spectroscopy, guaranteeing that the two bands sample
the rest-frame optical with the Balmer break falling between them. Eight of ten
are detected in both bands, while two are detected in F160W only. We study
their F160W morphologies, applying a maximum-deblending detection algorithm to
distinguish multiple- from single-component configurations, leading to
reassessments for several objects. Based on our NICMOS imaging and/or previous
dynamical evidence we identify five SMGs as multiple sources, which we
interpret as merging systems. Additionally, we calculate morphological
parameters asymmetry (A) and Gini coefficient (G); thanks to our sample's
limited redshift range we recover the trend that multiple-component,
merger-like morphologies are reflected in higher asymmetries. We analyze the
stellar populations of nine objects with F110W/F160W photometry, using archival
HST optical data when available. For multiple systems, we are able to model the
individual components that build up an SMG. With the available data we cannot
discriminate among star formation histories, but we constrain stellar masses
and mass ratios for merger-like SMG systems, obtaining a mean
log(M_*/M_sun)=10.9+/-0.2 for our full sample, with individual values
log(M_*/M_sun)~9.6-11.8. The morphologies and mass ratios of the least and most
massive systems match the predictions of the major-merger and cold accretion
SMG formation scenarios, respectively, suggesting that both channels may have a
role in the population's origin.Comment: 41 pages preprint, 3 figures, published in ApJ on 2013 May 1
Enamel proteins within two preferentially used animal models
Two different models have been used to study enamel proteins: rodent incisors and bovine or porcine tooth germs. In the present experiment proteins were sequentially extracted from forming enamel of rat incisors and bovine tooth germs and examined using SDS-PAGE.The Coomassie-blue staining of amelogenins from both species revealed very similar patterns, which indicates a rather common processing, although developed at different rates. Non-amelogenin proteins behave differently when Concanavalin-A probing was used. Bovine non-amelogenins contain amido-black stainable proteins which are not recognized by lectin, contrary to rat enamel.If those proteins are albumin or albumin derived, as recently suggested, the observed discrepancy might be explained by the non enzymatic glycation known to occur on circulating albumin. In that case it would be a consequence of the use of adult rats in which circulating albumin is partly glycated versus bovine foetuses in which albumin would not be significantly glycated. Finally both species contain glycoproteins within non-amelogenins, which remain to be more precisely defined.Deux modĂšles ont Ă©tĂ© utilisĂ©s pour lâĂ©tude des protĂ©ines de lâĂ©mail: les incisives des rongeurs et les germes dentaires de bovins ou de porcs. Dans cette expĂ©rimentation, nous avons extrait de façon sĂ©quentielle les protĂ©ines de lâĂ©mail en formation provenant dâincisives de rat et de germes dentaires bovins et nous les avons Ă©tudiĂ©es par Ă©lectrophorĂšse sur gel de polyacrylamide en prĂ©sence de SDS.La coloration des amĂ©logĂ©nines par le bleu de Coomassie rĂ©vĂšle dans les deux espĂšces des images Ă©lectrophorĂ©tiques semblables qui sont rĂ©vĂ©latrices dâun processus de transformation analogue bien que se dĂ©veloppant Ă des vitesses diffĂ©rentes.Les protĂ©ines non-amĂ©logĂ©nines se comportent de façon diffĂ©rente lorsque leur rĂ©vĂ©lation est effectuĂ©e par l'intermĂ©diaire dâun systĂšme Concanavaline-A et pĂ©roxydase. Les non amĂ©logĂ©nines dâorigine bovine contiennent des protĂ©ines colorĂ©es par lâamido-black qui ne sont pas reconnues par la lectine contrairement Ă ce qui se produit dans lâĂ©mail de rat. Si ces protĂ©ines sont de lâalbumine ou dĂ©rivĂ©es de lâalbumine comme cela a Ă©tĂ© rĂ©cemment suggĂ©rĂ©, la diffĂ©rence observĂ©e pourrait sâexpliquer par un processus de glycation non enzymatique de lâalbumine circulante. Dans ce cas, les rĂ©sultats obtenus seraient la consĂ©quence de lâutilisation dâun modĂšle adulte en ce qui concerne le rat dans lequel lâalbumine circulante est partiellement glycatĂ©e en opposition avec des foetus bovins ou la glycation de lâalbumine ne serait pas significative.Enfin, les deux espĂšces considĂ©rĂ©es contiennent des glycoprotĂ©ines dans la famille des non-amĂ©logĂ©nines qui restent Ă dĂ©finir de façon plus prĂ©cise
On the Continuous Formation of Field Spheroidal Galaxies in Hierarchical Models of Structure Formation
We re-examine the assembly history of field spheroidals as a potentially
powerful discriminant of galaxy formation models. Whereas monolithic collapse
and hierarchical, merger-driven, models suggest radically different histories
for these galaxies, neither the theoretical predictions nor the observational
data for field galaxies have been sufficiently reliable for precise conclusions
to be drawn. A major difficulty in interpreting the observations, reviewed
here, concerns the taxonomic definition of spheroidals in merger-based models.
Using quantitative measures of recent star formation activity drawn from the
internal properties of a sample of distant field galaxies in the Hubble Deep
Fields, we undertake a new analysis to assess the continuous formation of
spheroidal galaxies. Whereas abundances and redshift distributions of modelled
spheroidals are fairly insensitive to their formation path, we demonstrate that
the distribution and amount of blue light arising from recent mergers provides
a more sensitive approach. With the limited resolved data currently available,
the rate of mass assembly implied by the observed colour inhomogeneities is
compared to that expected in popular Lambda-dominated cold dark matter models
of structure formation. These models produce as many highly inhomogeneous
spheroidals as observed, but underpredict the proportion of homogeneous,
passive objects. We conclude that colour inhomogeneities, particularly when
combined with spectroscopic diagnostics for large, representative samples of
field spheroidals, will be a more valuable test of their physical assembly
history than basic source counts and redshift distributions. Securing such data
should be a high priority for the Advanced Camera for Surveys on Hubble Space
Telescope.Comment: 14 pages, 7 figures, submitted to MNRA
Quasars Clustering at z approx 3 on Scales less sim 10 h^{-1} Mpc
We test the hypothesis whether high redshift QSOs would preferentially appear
in small groups or pairs, and if they are associated with massive, young
clusters. We carried out a photometric search for \Ly emitters on scales
Mpc, in the fields of a sample of 47 known
QSOs. Wide and narrow band filter color-magnitude diagrams were generated for
each of the fields. A total of 13 non resolved objects with a
significant color excess were detected as QSO candidates at a redshift similar
to that of the target. All the candidates are significantly fainter than the
reference QSOs, with only 2 of them within 2 magnitudes of the central object.
Follow-up spectroscopic observations have shown that 5, i.e., about 40% of the
candidates, are QSOs at the same redshift of the target; 4 are QSOs at
different z (two of them probably being a lensed pair at z = 1.47); 2
candidates are unresolved HII galaxies at z0.3; one unclassified and one
candidate turned out to be a CCD flaw. These data indicate that at least 10% of
the QSOs at z3 do have companions.
We have also detected a number of resolved, rather bright \Ly Emitter
Candidates. Most probably a large fraction of them might be bright galaxies
with [OII] emission, at z 0.3. The fainter population of our
candidates corresponds to the current expectations. Thus, there are no strong
indication for the existence of an overdensity of \Ly galaxies brighter than m
25 around QSOs at 3.Comment: 29 pages, 8 figures, tar gzip LaTex file, accepted to appear in Ap
Southern Cosmology Survey II: Massive Optically-Selected Clusters from 70 square degrees of the SZE Common Survey Area
We present a catalog of 105 rich and massive (M>3\times10^{14}M_{\sun})
optically-selected clusters of galaxies extracted from 70 square-degrees of
public archival griz imaging from the Blanco 4-m telescope acquired over 45
nights between 2005 and 2007. We use the clusters' optically-derived properties
to estimate photometric redshifts, optical luminosities, richness, and masses.
We complement the optical measurements with archival XMM-Newton and ROSAT X-ray
data which provide additional luminosity and mass constraints on a modest
fraction of the cluster sample. Two of our clusters show clear evidence for
central lensing arcs; one of these has a spectacular large-diameter,
nearly-complete Einstein Ring surrounding the brightest cluster galaxy. A
strong motivation for this study is to identify the massive clusters that are
expected to display prominent signals from the Sunyaev-Zeldovich Effect (SZE)
and therefore be detected in the wide-area mm-band surveys being conducted by
both the Atacama Cosmology Telescope and the South Pole Telescope. The optical
sample presented here will be useful for verifying new SZE cluster candidates
from these surveys, for testing the cluster selection function, and for
stacking analyzes of the SZE data.Comment: 13 pages, 7 Figures. Accepted for publication to ApJSS. Full
resolution plots and additional material available at
http://peumo.rutgers.edu/~felipe/e-prints
The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics and Data Release
The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of 80
deg of the southern sky located in two fields: (,)= (5 hr,
) and (23 hr, ). The survey was carried out between
2005 and 2008 in bands with the Mosaic2 imager on the Blanco 4m
telescope. The primary aim of the BCS survey is to provide the data required to
optically confirm and measure photometric redshifts for Sunyaev-Zel'dovich
effect selected galaxy clusters from the South Pole Telescope and the Atacama
Cosmology Telescope. We process and calibrate the BCS data, carrying out PSF
corrected model fitting photometry for all detected objects. The median
10 galaxy (point source) depths over the survey in are
approximately 23.3 (23.9), 23.4 (24.0), 23.0 (23.6) and 21.3 (22.1),
respectively. The astrometric accuracy relative to the USNO-B survey is
milli-arcsec. We calibrate our absolute photometry using the stellar
locus in bands, and thus our absolute photometric scale derives from
2MASS which has % accuracy. The scatter of stars about the stellar locus
indicates a systematics floor in the relative stellar photometric scatter in
that is 1.9%, 2.2%, 2.7% and2.7%, respectively.
A simple cut in the AstrOmatic star-galaxy classifier {\tt spread\_model}
produces a star sample with good spatial uniformity. We use the resulting
photometric catalogs to calibrate photometric redshifts for the survey and
demonstrate scatter with an outlier fraction %
to . We highlight some selected science results to date and provide a
full description of the released data products.Comment: 23 pages, 23 figures . Response to referee comments. Paper accepted
for publication. BCS catalogs and images available for download from
http://www.usm.uni-muenchen.de/BC
A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. II. Quantifying morphological k-correction in the COSMOS field at 1<z<2: Ks band vs. I band
We quantify the effects of \emph{morphological k-correction} at by
comparing morphologies measured in the K and I-bands in the COSMOS area.
Ks-band data have indeed the advantage of probing old stellar populations for
, enabling a determination of galaxy morphological types unaffected by
recent star formation. In paper I we presented a new non-parametric method to
quantify morphologies of galaxies on seeing limited images based on support
vector machines. Here we use this method to classify
selected galaxies in the COSMOS area observed with WIRCam at CFHT. The obtained
classification is used to investigate the redshift distributions and number
counts per morphological type up to and to compare to the results
obtained with HST/ACS in the I-band on the same objects from other works. We
associate to every galaxy with and a probability between 0 and
1 of being late-type or early-type. The classification is found to be reliable
up to . The mean probability is . It decreases with redshift
and with size, especially for the early-type population but remains above
. The classification is globally in good agreement with the one
obtained using HST/ACS for . Above , the I-band classification
tends to find less early-type galaxies than the Ks-band one by a factor
1.5 which might be a consequence of morphological k-correction effects.
We argue therefore that studies based on I-band HST/ACS classifications at
could be underestimating the elliptical population. [abridged]Comment: accepted for publication in A&A, updated with referee comments, 12
pages, 10 figure
Far-ultraviolet imaging of the Hubble Deep Field-North: Star formation in normal galaxies at z < 1
We present far-ultraviolet (FUV) imaging of the Hubble Deep Field-North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Ă
. We detect 134 galaxies and one star down to a limit of FUV_(AB) ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0 < z < 1. We find that the FUV galaxy number counts are higher than those reported by GALEX, which we attribute at least in part to cosmic variance in the small HDF-N field of view. Six of the 13 Chandra sources at z < 0.85 in the HDF-N are detected in the FUV, and those are consistent with starbursts rather than active galactic nuclei. Cross-correlating with Spitzer sources in the field, we find that the FUV detections show general agreement with the expected L_(IR)/L_(UV) versus ÎČ relationship. We infer star formation rates (SFRs), corrected for extinction using the UV slope, and find a median value of 0.3 M_â yr^(-1) for FUV-detected galaxies, with 75% of detected sources having SFR < 1 M_â yr^(-1). Examining the morphological distribution of sources, we find that about half of all FUV-detected sources are identified as spiral galaxies. Half of morphologically selected spheroid galaxies at z < 0.85 are detected in the FUV, suggesting that such sources have had significant ongoing star formation in the epoch since z ~ 1
New XMM-Newton observation of the Phoenix cluster: properties of the cool core
(Abridged) We present a spectral analysis of a deep (220 ks) XMM-Newton
observation of the Phoenix cluster (SPT-CL J2344-4243), which we also combine
with Chandra archival ACIS-I data. We extract CCD and RGS X-ray spectra from
the core region to search for the signature of cold gas, and constrain the mass
deposition rate in the cooling flow which is thought to be responsible of the
massive star formation episode observed in the BCG. We find an average mass
deposition rate of /yr in the temperature range 0.3-3.0 keV from MOS data. A
temperature-resolved analysis shows that a significant amount of gas is
deposited only above 1.8 keV, while upper limits of the order of hundreds of
/yr can be put in the 0.3-1.8 keV temperature range. From pn data we
obtain /yr, and the
upper limits from the temperature-resolved analysis are typically a factor of 3
lower than MOS data. In the RGS spectrum, no line emission from ionization
states below Fe XXIII is seen above , and the amount of gas cooling
below keV has a best-fit value
/yr. In addition, our analysis of the FIR SED of the BCG based on
Herschel data provides /yr, significantly lower
than previous estimates by a factor 1.5. Current data are able to firmly
identify substantial amount of cooling gas only above 1.8 keV in the core of
the Phoenix cluster. While MOS data analysis is consistent with values as high
as within , pn data provide
yr at c.l. at temperature below 1.8 keV. At present, this
discrepancy cannot be explained on the basis of known calibration uncertainties
or other sources of statistical noise.Comment: A&A in press, typos corrected, revised text according to published
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