114 research outputs found
Evolution of the Most Luminous Dusty Galaxies
A summary of mid-infrared continuum luminosities arising from dust is given
for very luminous galaxies, Lir > 10^12 solar luminosities, with 0.005 < z <
3.2 containing active galactic nuclei (AGN), including 115 obscured AGN and 60
unobscured (type 1) AGN. All sources have been observed with the Spitzer
Infrared Spectrograph. Obscured AGN are defined as having optical depth > 0.7
in the 9.7 um silicate absorption feature and unobscured AGN show silicate in
emission. Luminosity vLv(8 um) is found to scale as (1+z)^2.6 to z = 2.8, and
luminosities vLv(8 um) are approximately 3 times greater for the most luminous
unobscured AGN. Total infrared luminosities for the most luminous obscured AGN,
Lir(AGN_obscured) in solar luminosities, scale as log Lir(AGN_obscured) =
12.3+-0.25 + 2.6(+-0.3)log(1+z), and for the most luminous unobscured AGN,
scale as log Lir(AGN1) = 12.6+-0.15 + 2.6(+-0.3)log(1+z), indicating that the
most luminous AGN are about 10 times more luminous than the most luminous
starbursts. Results are consistent with obscured and unobscured AGN having the
same total luminosities with differences arising only from orientation, such
that the obscured AGN are observed through very dusty clouds which extinct
about 50% of the intrinsic luminosity at 8 um. Both obscured and unobscured AGN
should be detected to z ~ 6 by Spitzer surveys with fv(24 um) > 0.3 mJy, even
without luminosity evolution for z > 2.5. By contrast, the most luminous
starbursts cannot be detected for z > 3, even if luminosity evolution continues
beyond z = 2.5.Comment: Includes corrected Figure 3, as publishe
Spectral Energy Distributions of type 2 QSOs: obscured star formation at high redshifts
We present new mid-infrared and submillimetre observations for a sample of
eight high redshift type-2 QSOs located in the Chandra Deep Field South. The
sources are X-ray absorbed with luminosities in excess of 10^44 erg/s. Two of
the targets have robust detections, S/N > 4, while a further three targets are
marginally detected with S/N > =2.5. All sources are detected in multiple
mid-infrared bands with the Spitzer Space Telescope. The multiwavelength
spectral energy distributions (SEDs) of the type-2 QSOs are compared to those
of two local ultraluminous galaxies (Arp220 and IR22491) in order to assess
contributions from a star-forming component in various parts of the SED. We
suggest that their submillimetre emission is possibly due to a starburst while
a large fraction of the mid-infrared energy is likely to originate in the
obscured central quasar. Using the mid-infrared and submm observations we
derive infrared luminosities which are found to be in excess of L>10^12Lsun.
The submillimetre (850micron) to X-ray (2 keV) spectral indices (alpha_SX) span
a wide range. About half of the type-2 QSOs have values typical for a
Compton-thick AGN with only 1 per cent of the nuclear emission seen through
scattering and, the remaining with values typical of submm-bright galaxies.
Combining the available observational evidence we outline a possible scenario
for the early stages of evolution of these sources.Comment: Accepted for publication in MNRA
An ISOCAM survey through gravitationally lensing galaxy clusters
ISOCAM was used to perform a deep survey through three gravitationally
lensing clusters of galaxies. Nearly seventy sq. arcmin were covered over the
clusters A370, A2218 and A2390. We present maps and photometry at 6.7 & 14.3
microns, showing a total of 145 mid-IR sources and the associated source
counts. The 15 micron counts reach the faintest level yet recorded. All sources
have counterparts in the optical or near-IR. Models of the clusters were used
to correct for the effects of lensing, which increases the sensitivity of the
survey. Seven of fifteen SCUBA sources were detected at 15 microns. Five have
redshift between 0.23 & 2.8, with a median of 0.9. The field sources were
counted to a lensing-corrected sensitivity of 30 microJy at 15 microns, and 14
microJy at 7 microns. The counts, corrected for completeness, contamination by
cluster sources and lensing, confirm and extend findings of an excess by a
factor of ten in the 15 micron population with respect to source models with no
evolution. Source redshifts are mostly between 0.4 and 1.5. For the counts at 7
microns, integrating from 14 microJy to 460 microJy, we resolve 0.49+/-0.2
nW.m^(-2).sr^(-1) of the infrared background light (IBL) into discrete sources.
At 15 microns we include the counts from other ISOCAM surveys to integrate from
30 microJy to 50 mJy, two to three times deeper than unlensed surveys, to
resolve 2.7+/-0.62 nW.m^(-2).sr^(-1) of the IBL. These values are 10% and 55%,
respectively, of the upper limit to the IBL, derived from photon-photon pair
production of the TeV gamma rays from BL-Lac sources on the IBL photons.
However, recent detections of TeV gamma rays from the z=0.129 BL Lac H1426+428
suggest that the 15 micron background reported implies substantial absorption
of TeV photons from that source.Comment: 35 pages, 17 figures, to appear in Astronomy and Astrophysics, full
paper with high-resolution figures available at
http://www.iso.vilspa.esa.es/science/pub/2003
Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources
We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples
Galaxy evolution from deep multi-wavelength Infrared surveys: a prelude to Herschel
[abridged] At the end of the Spitzer cryogenic mission and the onset of the
Herschel era, we review our current knowledge on galaxy evolution at IR
wavelengths. We also develop new tools for the analysis of background
fluctuations to constrain source counts in regimes of high confusion. We
analyse a large variety of new data on galaxy evolution and high-z source
populations from Spitzer surveys, as well as complementary data from sub-mm
(BLAST) and millimetric ground-based observations. These data confirm earlier
indications about a very rapid increase of galaxy volume emissivity up to z~1.
This is the fastest evolution rate observed for galaxies at any wavelengths.
The observed Spitzer counts at 24 micron require a combination of fast
evolution for the dominant population and a bumpy spectrum with substantial PAH
emission at z~1 to 2. Confusion-limited number counts at longer wavelengths
confirm these results. All the present data require that the fast observed
evolution from z=0 to 1 flattens around redshift 1 and then keeps approximately
constant up to z~2.5 at least. The present-day IR data provide clear evidence
for the existence of a distinct population of very luminous galaxies becoming
dominant at z > 1. Their cosmological evolution, peaking around z~2, shows a
faster decay with cosmic time than lower luminosity systems, whose maximal
activity is set around z~1, then supporting an earlier phase of formation for
the most luminous and massive galaxies. From a comparison of our results on the
comoving IR emissivity with recent estimates of the redshift-dependent stellar
mass functions of galaxies, we infer that a large fraction (>=50%) of the IR
activity at z > 1 should be due to obscured AGN accretion and that concomitant
SF in high-z luminous sources should follow a top-heavy IMF.Comment: Accepted for publication by Astronomy and Astrophysic
Correction to: Rapid, Full-Scale Change to Virtual PCIT During the COVID-19 Pandemic: Implementation and Clinical Implications
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic
Glutathione Is a Key Player in Metal-Induced Oxidative Stress Defenses
Since the industrial revolution, the production, and consequently the emission of metals, has increased exponentially, overwhelming the natural cycles of metals in many ecosystems. Metals display a diverse array of physico-chemical properties such as essential versus non-essential and redox-active versus non-redox-active. In general, all metals can lead to toxicity and oxidative stress when taken up in excessive amounts, imposing a serious threat to the environment and human health. In order to cope with different kinds of metals, plants possess defense strategies in which glutathione (GSH; γ-glu-cys-gly) plays a central role as chelating agent, antioxidant and signaling component. Therefore, this review highlights the role of GSH in: (1) metal homeostasis; (2) antioxidative defense; and (3) signal transduction under metal stress. The diverse functions of GSH originate from the sulfhydryl group in cysteine, enabling GSH to chelate metals and participate in redox cycling
Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust polarization fraction and polarization angle at 1° resolution, taking into account noise bias and possible systematic effects. The sensitivity of the Planck HFI polarization measurements allows for the first time a mapping of Galactic dust polarized emission on large scales, including low column density regions. We find that the maximum observed dust polarization fraction is high (pmax = 19.8%), in particular in some regions of moderate hydrogen column density (NH < 2 × 1021 cm-2). The polarization fraction displays a large scatter at NH below a few 1021 cm-2. There is a general decrease in the dust polarization fraction with increasing column density above NH ≃ 1 × 1021 cm-2 and in particular a sharp drop above NH ≃ 1.5 × 1022 cm-2. We characterize the spatial structure of the polarization angle using the angle dispersion function. We find that the polarization angle is ordered over extended areas of several square degrees, separated by filamentary structures of high angle dispersion function. These appear as interfaces where the sky projection of the magnetic field changes abruptly without variations in the column density. The polarization fraction is found to be anti-correlated with the dispersion of polarization angles. These results suggest that, at the resolution of 1°, depolarization is due mainly to fluctuations in the magnetic field orientation along the line of sight, rather than to the loss of grain alignment in shielded regions. We also compare the polarization of thermal dust emission with that of synchrotron measured with Planck, low-frequency radio data, and Faraday rotation measurements toward extragalactic sources. These components bear resemblance along the Galactic plane and in some regions such as the Fan and North Polar Spur regions. The poor match observed in other regions shows, however, that dust, cosmic-ray electrons, and thermal electrons generally sample different parts of the line of sight.
Reproduced with permission, © ESO, 201
The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a shallow and wide submillimeter imaging survey with SPIRE
A large sub-mm survey with Herschel will enable many exciting science opportunities, especially in an era of wide-field optical and radio surveys and high resolution cosmic microwave background experiments. The Herschel-SPIRE Legacy Survey (HSLS), will lead to imaging data over 4000 sq. degrees at 250, 350, and 500 micron. Major Goals of HSLS are: (a) produce a catalog of 2.5 to 3 million galaxies down to 26, 27 and 33 mJy (50% completeness; 5 sigma confusion noise) at 250, 350 and 500 micron, respectively, in the southern hemisphere (3000 sq. degrees) and in an equatorial strip (1000 sq. degrees), areas which have extensive multi-wavelength coverage and are easily accessible from ALMA. Two thirds of the of the sources are expected to be at z > 1, one third at z > 2 and about a 1000 at z > 5. (b) Remove point source confusion in secondary anisotropy studies with Planck and ground-based CMB data. (c) Find at least 1200 strongly lensed bright sub-mm sources leading to a 2% test of general relativity. (d) Identify 200 proto-cluster regions at z of 2 and perform an unbiased study of the environmental dependence of star formation. (e) Perform an unbiased survey for star formation and dust at high Galactic latitude and make a census of debris disks and dust around AGB stars and white dwarfs
Planck early results. XIII. Statistical properties of extragalactic radio sources in the Planck Early Release Compact Source Catalogue
The data reported in Planck’s Early Release Compact Source Catalogue (ERCSC) are exploited to measure the number counts (dN/dS) of
extragalactic radio sources at 30, 44, 70, 100, 143 and 217 GHz. Due to the full-sky nature of the catalogue, this measurement extends to the
rarest and brightest sources in the sky. At lower frequencies (30, 44, and 70 GHz) our counts are in very good agreement with estimates based on
WMAP data, being somewhat deeper at 30 and 70 GHz, and somewhat shallower at 44 GHz. Planck’s source counts at 143 and 217 GHz join
smoothly with the fainter ones provided by the SPT and ACT surveys over small fractions of the sky. An analysis of source spectra, exploiting
Planck’s uniquely broad spectral coverage, finds clear evidence of a steepening of the mean spectral index above about 70 GHz. This implies
that, at these frequencies, the contamination of the CMB power spectrum by radio sources below the detection limit is significantly lower than
previously estimated
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