941 research outputs found
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
ALMA reveals a chemically evolved submillimeter galaxy at z=4.76
The chemical properties of high-z galaxies provide important information to
constrain galaxy evolutionary scenarios. However, widely-used metallicity
diagnostics based on rest-frame optical emission lines are not usable for
heavily dust-enshrouded galaxies (such as Sub-Millimeter Galaxies; SMGs),
especially at z>3. Here we focus on the flux ratio of the far-infrared
fine-structure emission lines [NII]205um and [CII]158um to assess the
metallicity of high-z SMGs. Through ALMA cycle 0 observations, we have detected
the [NII]205um emission in a strongly [CII]-emitting SMG, LESS J033229.4-275619
at z=4.76. The velocity-integrated [NII]/[CII] flux ratio is 0.043 +/- 0.008.
This is the first measurement of the [NII]/[CII] flux ratio in high-z galaxies,
and the inferred flux ratio is similar to the ratio observed in the nearby
universe (~0.02-0.07). The velocity-integrated flux ratio and photoionization
models suggest that the metallicity in this SMG is consistent with solar,
implying the chemical evolution has progressed very rapidly in this system at
z=4.76. We also obtain a tight upper limit on the CO(12-11) transition, which
translates into CO(12-11)/CO(2-1) <3.8 (3 sigma). This suggests that the
molecular gas clouds in LESS J033229.4-275619 are not affected significantly by
the radiation field emitted by the AGN in this system.Comment: 5 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics Letter
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
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Life in the Atacama — Year 2: Geologic reconnaissance through long-range roving and implications on the search for life
The Life in the Atacama-2004 project, which included geological, morphological, and mineralogical mapping through combined satellite, field-based, and microscopic perspectives and long-range roving, led to the localization of potential habitats
Polarized thermal emission from dust in a galaxy at redshift 2.6
Magnetic fields are fundamental to the evolution of galaxies, playing a key
role in the astrophysics of the interstellar medium and star formation.
Large-scale ordered magnetic fields have been mapped in the Milky Way and
nearby galaxies, but it is not known how early in the Universe such structures
form. Here we report the detection of linearly polarized thermal emission from
dust grains in a strongly lensed, intrinsically luminous galaxy that is forming
stars at a rate more than a thousand times that of the Milky Way at redshift
2.6, within 2.5 Gyr of the Big Bang. The polarized emission arises from the
alignment of dust grains with the local magnetic field. The median polarization
fraction is of order one per cent, similar to nearby spiral galaxies. Our
observations support the presence of a 5 kiloparsec-scale ordered magnetic
field with a strength of around 500uG or lower, orientated parallel to the
molecular gas disk. This confirms that such structures can be rapidly formed in
galaxies, early in cosmic history.Comment: Published in Nature. Online version available at
https://www.nature.com/articles/s41586-023-06346-
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