1,105 research outputs found
The local FIR Galaxy Colour-Luminosity distribution: A reference for BLAST, and Herschel/SPIRE sub-mm surveys
We measure the local galaxy far-infrared (FIR) 60-to-100 um colour-luminosity
distribution using an all-sky IRAS survey. This distribution is an important
reference for the next generation of FIR--submillimetre surveys that have and
will conduct deep extra-galactic surveys at 250--500 um. With the peak in
dust-obscured star-forming activity leading to present-day giant ellipticals
now believed to occur in sub-mm galaxies near z~2.5, these new
FIR--submillimetre surveys will directly sample the SEDs of these distant
objects at rest-frame FIR wavelengths similar to those at which local galaxies
were observed by IRAS. We have taken care to correct for temperature bias and
evolution effects in our IRAS 60 um-selected sample. We verify that our
colour-luminosity distribution is consistent with measurements of the local FIR
luminosity function, before applying it to the higher-redshift Universe. We
compare our colour-luminosity correlation with recent dust-temperature
measurements of sub-mm galaxies and find evidence for pure luminosity evolution
of the form (1+z)^3. This distribution will be useful for the development of
evolutionary models for BLAST and SPIRE surveys as it provides a statistical
distribution of rest-frame dust temperatures for galaxies as a function of
luminosity.Comment: 12 pages, 7 figures. MNRAS in press. This revision matches final
published version. Fixes typos in footnote 1 and equation 8. Minor
modifications to text and references. Final results unchange
Origins of the extragalactic background at 1mm from a combined analysis of the AzTEC and MAMBO data in GOODS-N
We present a study of the cosmic infrared background, which is a measure of
the dust obscured activity in all galaxies in the Universe. We venture to
isolate the galaxies responsible for the background at 1mm; with spectroscopic
and photometric redshifts we constrain the redshift distribution of these
galaxies. We create a deep 1.16mm map (sigma ~ 0.5mJy) by combining the AzTEC
1.1mm and MAMBO 1.2mm datasets in GOODS-N. This combined map contains 41 secure
detections, 13 of which are new. By averaging the 1.16mm flux densities of
individually undetected galaxies with 24um flux densities > 25uJy, we resolve
31--45 per cent of the 1.16mm background. Repeating our analysis on the SCUBA
850um map, we resolve a higher percentage (40--64 per cent) of the 850um
background. A majority of the background resolved (attributed to individual
galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of
the resolved submillimeter to millimeter background is applied to a reasonable
scenario for the origins of the unresolved submillimeter background, 60--88 per
cent of the total 1.16mm background comes from galaxies at z > 1.3.Comment: 12 pages, 10 figures. Accepted by MNRAS. The combined map is publicly
available at http://www.astro.umass.edu/~pope/goodsn_mm
A CO emission line from the optical and near-IR undetected submillimeter galaxy GN10
We report the detection of a CO emission line from the submillimiter galaxy
(SMG) GN10 in the GOODS-N field. GN10 lacks any counterpart in extremely deep
optical and near-IR imaging obtained with the Hubble Space Telescope and
ground-based facilities. This is a prototypical case of a source that is
extremely obscured by dust, for which it is practically impossible to derive a
spectroscopic redshift in the optical/near-IR. Under the hypothesis that GN10
is part of a proto-cluster structure previously identified at z~4.05 in the
same field, we searched for CO[4-3] at 91.4 GHz with the IRAM Plateau de Bure
Interferometer, and successfully detected a line. We find that the most likely
redshift identification is z=4.0424+-0.0013, based on: 1) the very low chance
that the CO line is actually serendipitous from a different redshift; 2) a
radio-IR photometric redshift analysis; 3) the identical radio-IR SED, within a
scaling factor, of two other SMGs at the same redshift. The faintness at
optical/near-IR wavelengths requires an attenuation of A_V~5-7.5 mag. This
result supports the case that a substantial population of very high-z SMGs
exists that had been missed by previous spectroscopic surveys. This is the
first time that a CO emission line has been detected for a galaxy that is
invisible in the optical and near-IR. Our work demonstrates the power of
existing and planned facilities for completing the census of star formation and
stellar mass in the distant Universe by measuring redshifts of the most
obscured galaxies through millimeter spectroscopy.Comment: 5 pages, 4 figures. ApJ Letters in pres
Submillimeter galaxies behind the Bullet Cluster (1E 0657-56)
Clusters of galaxies are effective gravitational lenses able to magnify
background galaxies and making it possible to probe the fainter part of the
galaxy population. Submillimeter galaxies, which are believed to be
star-forming galaxies at typical redshifts of 2 to 3, are a major contaminant
to the extended Sunyaev-Zeldovich (SZ) signal of galaxy clusters. For a proper
quantification of the SZ signal the contribution of submillimeter galaxies
needs to be quantified. The aims of this study are to identify submillimeter
sources in the field of the Bullet Cluster (1E 0657-56), a massive cluster of
galaxies at z~0.3, measure their flux densities at 870 micron, and search for
counterparts at other wavelengths to constrain their properties. We carried out
deep observations of the submillimeter continuum emission at 870 micron using
the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment
(APEX) telescope. Several numerical techniques were used to quantify the noise
properties of the data and extract sources. In total, seventeen sources were
found. Thirteen of them lie in the central 10 arcminutes of the map, which has
a pixel sensitivity of 1.2 mJy per 22 arcsec beam. After correction for flux
boosting and gravitational lensing, the number counts are consistent with
published submm measurements. Nine of the sources have infrared counterparts in
Spitzer maps. The strongest submm detection coincides with a source previously
reported at other wavelengths, at an estimated redshift z~2.7. If the submm
flux arises from two images of a galaxy magnified by a total factor of 75, as
models have suggested, its intrinsic flux would be around 0.6 mJy, consistent
with an intrinsic luminosity below 10^12 L_sun.Comment: Accepted by A&A, 15 pages, 11 figure
The faint counterparts of MAMBO mm sources near the NTT Deep Field
We discuss identifications for 18 sources from our MAMBO 1.2mm survey of the
region surrounding the NTT Deep Field. We have obtained accurate positions from
Very Large Array 1.4GHz interferometry and in a few cases IRAM mm
interferometry, and have also made deep BVRIzJK imaging at ESO. We find
thirteen 1.2mm sources associated with optical/near-infrared objects in the
magnitude range K=19.0 to 22.5, while five are blank fields at K>22. The median
redshift of the radio-identified mm sources is ~2.6 from the radio/mm
estimator, and the median optical/near-infrared photometric redshifts for the
objects with counterparts ~2.1. This suggests that those radio-identified mm
sources without optical/near-infrared counterparts tend to lie at higher
redshifts than those with optical/near-infrared counterparts. Compared to
published identifications of objects from 850micron surveys of similar depth,
the median K and I magnitudes of our counterparts are roughly two magnitudes
fainter and the dispersion of I-K colors is less. Real differences in the
median redshifts, residual mis-identifications with bright objects, cosmic
variance, and small number statistics are likely to contribute to this
significant difference, which also affects redshift measurement strategies. We
discuss basic properties of the near-infrared/(sub)mm/radio spectral energy
distributions of our galaxies and of interferometrically identified submm
sources from the literature. From a comparison with submm objects with
CO-confirmed spectroscopic redshifts we argue that roughly two thirds of the
(sub)mm galaxies are at z>~2.5. This fraction is probably larger when including
sources without radio counterparts. (abridged)Comment: 45 pages, 9 figures. Accepted by ApJ. The resolution of figures 2 and
3 has been degraded. A higher quality pdf version of this paper is available
at http://www.mpe.mpg.de/~dannerb
Spectroscopic Confirmation of a z=2.79 Multiply Imaged Luminous Infrared Galaxy Behind the Bullet Cluster
We report spectroscopic confirmation and high-resolution infrared imaging of
a z=2.79 triply-imaged galaxy behind the Bullet Cluster. This source, a
Spitzer-selected luminous infrared galaxy (LIRG), is confirmed via polycyclic
aromatic hydrocarbon (PAH) features using the Spitzer Infrared Spectrograph
(IRS) and resolved with HST WFC3 imaging. In this galaxy, which with a stellar
mass of M*=4e9 Msun is one of the two least massive ones studied with IRS at
z>2, we also detect H_2 S(4) and H_2 S(5) pure rotational lines (at 3.1 sigma
and 2.1 sigma) - the first detection of these molecular hydrogen lines in a
high-redshift galaxy. From the molecular hydrogen lines we infer an excitation
temperature T=377+68-84 K. The detection of these lines indicates that the warm
molecular gas mass is 6(+36-4)% of the stellar mass and implies the likely
existence of a substantial reservoir of cold molecular gas in the galaxy.
Future spectral observations at longer wavelengths with facilities like the
Herschel Space Observatory, the Large Millimeter Telescope, and the Atacama
Pathfinder EXperiment (APEX) thus hold the promise of precisely determining the
total molecular gas mass. Given the redshift, and using refined astrometric
positions from the high resolution imaging, we also update the magnification
estimate and derived fundamental physical properties of this system. The
previously published values for total infrared luminosity, star formation rate,
and dust temperature are confirmed modulo the revised magnification; however we
find that PAH emission is roughly a factor of five stronger than would be
predicted by the relations between the total infrared and PAH luminosity
reported for SMGs and starbursts in Pope et al. (2008).Comment: 8 pages, 4 figures, accepted to Ap
Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts
[Abridged] We present the first results from a 1.1 mm confusion-limited map
of the GOODS-S field taken with AzTEC on the ASTE telescope. We imaged a 270
sq. arcmin field to a 1\sigma depth of 0.48 - 0.73 mJy/beam, making this one of
the deepest blank-field surveys at mm-wavelengths ever achieved. Although our
GOODS-S map is extremely confused, we demonstrate that our source
identification and number counts analyses are robust, and the techniques
discussed in this paper are relevant for other deeply confused surveys. We find
a total of 41 dusty starburst galaxies with S/N >= 3.5 within this uniformly
covered region, where only two are expected to be false detections. We derive
the 1.1mm number counts from this field using both a "P(d)" analysis and a
semi-Bayesian technique, and find that both methods give consistent results.
Our data are well-fit by a Schechter function model with (S', N(3mJy), \alpha)
= (1.30+0.19 mJy, 160+27 (mJy/deg^2)^(-1), -2.0). Given the depth of this
survey, we put the first tight constraints on the 1.1 mm number counts at
S(1.1mm) = 0.5 mJy, and we find evidence that the faint-end of the number
counts at S(850\mu m) < 2.0 mJy from various SCUBA surveys towards lensing
clusters are biased high. In contrast to the 870 \mu m survey of this field
with the LABOCA camera, we find no apparent under-density of sources compared
to previous surveys at 1.1 mm. Additionally, we find a significant number of
SMGs not identified in the LABOCA catalogue. We find that in contrast to
observations at wavelengths < 500 \mu m, MIPS 24 \mu m sources do not resolve
the total energy density in the cosmic infrared background at 1.1 mm,
demonstrating that a population of z > 3 dust-obscured galaxies that are
unaccounted for at these shorter wavelengths potentially contribute to a large
fraction (~2/3) of the infrared background at 1.1 mm.Comment: 21 pages, 9 figures. Accepted to MNRAS
AzTEC Millimetre Survey of the COSMOS Field - II. Source Count Overdensity and Correlations with Large-Scale Structure
We report an over-density of bright sub-millimetre galaxies (SMGs) in the
0.15 sq. deg. AzTEC/COSMOS survey and a spatial correlation between the SMGs
and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field
shows a ~ 3-sigma over-density of robust SMG detections when compared to a
background, or "blankfield", population model that is consistent with SMG
surveys of fields with no extragalactic bias. The SMG over-density is most
significant in the number of very bright detections (14 sources with measured
fluxes S(1.1mm) > 6 mJy), which is entirely incompatible with sample variance
within our adopted blank-field number densities and infers an over-density
significance of >> 4. We find that the over-density and spatial correlation to
optical-IR galaxy density are most consistent with lensing of a background SMG
population by foreground mass structures along the line of sight, rather than
physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG
positions are only weakly correlated with weak-lensing maps, suggesting that
the dominant sources of correlation are individual galaxies and the more
tenuous structures in the region and not the massive and compact clusters.
These results highlight the important roles cosmic variance and large-scale
structure can play in the study of SMGs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in MNRA
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