420 research outputs found
The PEP Survey: Infrared Properties of Radio-Selected AGN
By exploiting the VLA-COSMOS and the Herschel-PEP surveys, we investigate the
Far Infrared (FIR) properties of radio-selected AGN. To this purpose, from
VLA-COSMOS we considered the 1537, F[1.4 GHz]>0.06 mJy sources with a reliable
redshift estimate, and sub-divided them into star-forming galaxies and AGN
solely on the basis of their radio luminosity. The AGN sample is complete with
respect to radio selection at all z<~3.5. 832 radio sources have a counterpart
in the PEP catalogue. 175 are AGN. Their redshift distribution closely
resembles that of the total radio-selected AGN population, and exhibits two
marked peaks at z~0.9 and z~2.5. We find that the probability for a
radio-selected AGN to be detected at FIR wavelengths is both a function of
radio power and redshift, whereby powerful sources are more likely to be FIR
emitters at earlier epochs. This is due to two distinct effects: 1) at all
radio luminosities, FIR activity monotonically increases with look-back time
and 2) radio activity of AGN origin is increasingly less effective at
inhibiting FIR emission. Radio-selected AGN with FIR emission are
preferentially located in galaxies which are smaller than those hosting
FIR-inactive sources. Furthermore, at all z<~2, there seems to be a
preferential (stellar) mass scale M ~[10^{10}-10^{11}] Msun which maximizes the
chances for FIR emission. We find such FIR (and MIR) emission to be due to
processes indistinguishable from those which power star-forming galaxies. It
follows that radio emission in at least 35% of the entire AGN population is the
sum of two contributions: AGN accretion and star-forming processes within the
host galaxy.Comment: 13 pages, 14 figures, to appear in MNRA
Molecular Gas, Dust and Star Formation in Galaxies: II. Dust properties and scalings in \sim\ 1600 nearby galaxies
We aim to characterize the relationship between dust properties. We also aim
to provide equations to estimate accurate dust properties from limited
observational datasets.
We assemble a sample of 1,630 nearby (z<0.1) galaxies-over a large range of
Mstar, SFR - with multi-wavelength observations available from wise, iras,
planck and/or SCUBA. The characterization of dust emission comes from SED
fitting using Draine & Li dust models, which we parametrize using two
components (warm and cold ). The subsample of these galaxies with global
measurements of CO and/or HI are used to explore the molecular and/or atomic
gas content of the galaxies.
The total Lir, Mdust and dust temperature of the cold component (Tc) form a
plane that we refer to as the dust plane. A galaxy's sSFR drives its position
on the dust plane: starburst galaxies show higher Lir, Mdust and Tc compared to
Main Sequence and passive galaxies. Starburst galaxies also show higher
specific Mdust (Mdust/Mstar) and specific Mgas (Mgas/Mstar). The Mdust is more
closely correlated with the total Mgas (atomic plus molecular) than with the
individual components. Our multi wavelength data allows us to define several
equations to estimate Lir, Mdust and Tc from one or two monochromatic
luminosities in the infrared and/or sub-millimeter.
We estimate the dust mass and infrared luminosity from a single monochromatic
luminosity within the R-J tail of the dust emission, with errors of 0.12 and
0.20dex, respectively. These errors are reduced to 0.05 and 0.10 dex,
respectively, if the Tc is used. The Mdust is correlated with the total Mism
(Mism \propto Mdust^0.7). For galaxies with Mstar 8.5<log(Mstar/Msun) < 11.9,
the conversion factor \alpha_850mum shows a large scatter (rms=0.29dex). The SF
mode of a galaxy shows a correlation with both the Mgass and Mdust: high
Mdust/Mstar galaxies are gas-rich and show the highest SFRs.Comment: 24 pages, 28 figures, 6 tables, Accepted for publication in A&
Automated mining of the ALMA archive in the COSMOS field (A3COSMOS): II. Cold molecular gas evolution out to Redshift 6
We present new measurements of the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the ALMA public archive in the COSMOS deep field (A3COSMOS). Our A3COSMOS dataset contains ~700 galaxies (0.3 < z < 6) with high-confidence ALMA detections in the (sub-)millimeter continuum and multi-wavelength spectral energy distributions (SEDs). Multiple gas mass calibration methods are compared and biases in band conversions (from observed ALMA wavelength to rest-frame Rayleigh-Jeans(RJ)-tail continuum) have been tested. Combining our A3COSMOS sample with ~1,000 CO-observed galaxies at 0 < z < 4 (75% at z < 0.1), we parameterize galaxies' molecular gas depletion time and molecular gas to stellar mass ratio (gas fraction) each as a function of the stellar mass, offset from the star-forming main sequence (Delta MS) and cosmic age (or redshift). Our proposed functional form provides a statistically better fit to current data (than functional forms in the literature), and implies a "downsizing" effect (i.e., more-massive galaxies evolve earlier than less-massive ones) and "mass-quenching" (gas consumption slows down with cosmic time for massive galaxies but speeds up for low-mass ones). Adopting galaxy stellar mass functions and applying our function for gas mass calculation, we for the first time infer the cosmic cold molecular gas density evolution out to redshift 6 and find agreement with CO blind surveys as well as semi-analytic modeling. These together provide a coherent picture of cold molecular gas, SFR and stellar mass evolution in galaxies across cosmic time
Insights into the effects of N-glycosylation on the characteristics of the VC1 domain of the human receptor for advanced glycation end products (RAGE) secreted by Pichia pastoris
Advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs), resulting from non-enzymatic modifications of proteins, are potentially harmful to human health. They directly act on proteins, affecting structure and function, or through receptor-mediated mechanisms. RAGE, a type I transmembrane glycoprotein, was identified as a receptor for AGEs. RAGE is involved in chronic inflammation, oxidative stress-based diseases and ageing. The majority of RAGE ligands bind to the VC1 domain. This domain was successfully expressed and secreted by Pichia pastoris. Out of two N-glycosylation sites, one (Asn25) was fully occupied while the other (Asn81) was under-glycosylated, generating two VC1 variants, named p36 and p34. Analysis of N-glycans and of their influence on VC1 properties were here investigated. The highly sensitive procainamide labeling method coupled to ES-MS was used for N-glycan profiling. N-glycans released from VC1 ranged from Man9GlcNAc2- to Man15GlcNAc2- with major Man10GlcNAc2- and Man11GlcNAc2- species for p36 and p34, respectively. Circular dichroism spectra indicated that VC1 maintains the same conformation also after removal of N-glycans. Thermal denaturation curves showed that the carbohydrate moiety has a small stabilizing effect on VC1 protein conformation. The removal of the glycan moiety did not affect the binding of VC1 to sugar-derived AGE- or malondialdehyde-derived ALE-human serum albumin. Given the crucial role of RAGE in human pathologies, the features of VC1 from P. pastoris will prove useful in designing strategies for the enrichment of AGEs/ALEs from plasma, urine or tissues, and in characterizing the nature of the interaction
The Far-Infrared, UV and Molecular Gas Relation in Galaxies up to z=2.5
We use the infrared excess (IRX) FIR/UV luminosity ratio to study the
relation between the effective UV attenuation (A_IRX) and the UV spectral slope
(beta) in a sample of 450 1<z<2.5 galaxies. The FIR data is from very deep
Herschel observations in the GOODS fields that allow us to detect galaxies with
SFRs typical of galaxies with log(M)>9.3. Thus, we are able to study galaxies
on and even below the main SFR-stellar mass relation (main sequence). We find
that main sequence galaxies form a tight sequence in the IRX--beta plane, which
has a flatter slope than commonly used relations. This slope favors a SMC-like
UV extinction curve, though the interpretation is model dependent. The scatter
in the IRX-beta plane, correlates with the position of the galaxies in the
SFR-M plane. Using a smaller sample of galaxies with CO gas masses, we study
the relation between the UV attenuation and the molecular gas content. We find
a very tight relation between the scatter in the IRX-beta plane and the
specific attenuation (S_A), a quantity that represents the attenuation
contributed by the molecular gas mass per young star. S_A is sensitive to both
the geometrical arrangement of stars and dust, and to the compactness of the
star forming regions. We use this empirical relation to derive a method for
estimating molecular gas masses using only widely available integrated
rest-frame UV and FIR photometry. The method produces gas masses with an
accuracy between 0.12-0.16 dex in samples of normal galaxies between z~0 and
z~1.5. Major mergers and sub-millimeter galaxies follow a different S_A
relation.Comment: 11 pages, 6 pages appendix, 11 figures, accepted to Ap
A Multiwavelength Consensus on the Main Sequence of Star-Forming Galaxies at z~2
We compare various star formation rate (SFR) indicators for star-forming
galaxies at in the COSMOS field. The main focus is on the SFRs from
the far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies
selected according to the BzK criterion. FIR-selected samples lead to a vastly
different slope of the SFR-stellar mass () relation, compared to that of
the dominant main sequence population as measured from the UV, since the FIR
selection picks predominantly only a minority of outliers. However, there is
overall agreement between the main sequences derived with the two SFR
indicators, when stacking on the PACS maps the BzK-selected galaxies. The
resulting logarithmic slope of the SFR-{} relation is , in
agreement with that derived from the dust-corrected UV-luminosity. Exploiting
deeper 24m-Spitzer data we have characterized a sub-sample of galaxies
with reddening and SFRs poorly constrained, as they are very faint in the
band. The combination of Herschel with Spitzer data have allowed us to largely
break the age/reddening degeneracy for these intriguing sources, by
distinguishing whether a galaxy is very red in B-z because of being heavily
dust reddened, or whether because star formation has been (or is being)
quenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking
the radio data and to those derived from the H luminosity of a sample
of star-forming galaxies at . The two sets of SFRs are broadly
consistent as they are with the SFRs derived from the UV and by stacking the
corresponding PACS data in various mass bins.Comment: Accepted for publication in MNRA
Dust temperature and CO-to-H2 conversion factor variations in the SFR-M* plane
Deep Herschel imaging and 12CO(2-1) line luminosities from the IRAM PdBI are
combined for a sample of 17 galaxies at z>1 from the GOODS-N field. The sample
includes galaxies both on and above the main sequence (MS) traced by
star-forming galaxies in the SFR-M* plane. The far-infrared data are used to
derive dust masses, Mdust. Combined with an empirical prescription for the
dependence of the gas-to-dust ratio on metallicity (GDR), the CO luminosities
and Mdust values are used to derive for each galaxy the CO-to-H2 conversion
factor, alpha_co. Like in the local Universe, the value of alpha_co is a factor
of ~5 smaller in starbursts compared to normal star-forming galaxies (SFGs). We
also uncover a relation between alpha_co and dust temperature (Tdust; alpha_co
decreasing with increasing Tdust) as obtained from modified blackbody fits to
the far-infrared data. While the absolute normalization of the alpha_co(Tdust)
relation is uncertain, the global trend is robust against possible systematic
biases in the determination of Mdust, GDR or metallicity. Although we cannot
formally distinguish between a step and a smooth evolution of alpha_co with the
dust temperature, we can conclude that in galaxies of near-solar metallicity, a
critical value of Tdust=30K can be used to determine whether the appropriate
alpha_co is closer to the starburst value (1.0 Msun(K kms pc^2)^-1, if
Tdust>30K) or closer to the Galactic value (4.35 Msun (K kms pc^2)^-1, if
Tdust<30K). This indicator has the great advantage of being less subjective
than visual morphological classifications of mergers/SFGs, which can be
difficult at high z because of the clumpy nature of SFGs. In the absence of
far-infrared data, the offset of a galaxy from the main sequence (i.e.,
log[SSFR(galaxy)/SSFR_MS(M*,z)]) can be used to identify galaxies requiring the
use of an alpha_co conversion factor lower than the Galactic value.Comment: Accepted for publication in Astronomy and Astrophysics (A&A); 15
pages, 6 figures; V2: updated reference lis
The AGN content in luminous IR galaxies at z\sim2 from a global SED analysis including Herschel data
We use Herschel-PACS far-infrared data, combined with previous multi-band
information and mid-IR spectra, to properly account for the presence of an
active nucleus and constrain its energetic contribution in luminous infrared
(IR) sources at z\sim2. The sample is composed of 24 sources in the GOODS-South
field, with typical IR luminosity of 10^{12} Lo. Data from the 4 Ms Chandra
X-ray imaging in this field are also used to identify and characterize AGN
emission. We reproduce the observed spectral energy distribution (SED),
decomposed into a host-galaxy and an AGN component. A smooth-torus model for
circum-nuclear dust is used to account for the direct and re-processed
contribution from the AGN. We confirm that galaxies with typical
L_{8-1000um}\sim10^{12}Lo at z\sim2 are powered predominantly by
star-formation. An AGN component is present in nine objects (\sim35% of the
sample) at the 3sigma confidence level, but its contribution to the 8-1000 um
emission accounts for only \sim5% of the energy budget. The AGN contribution
rises to \sim23% over the 5-30 um range (in agreement with Spitzer IRS results)
and to \sim60% over the narrow 2-6 um range. The presence of an AGN is
confirmed by X-ray data for 3 (out of nine) sources, with X-ray spectral
analysis indicating the presence of significant absorption, i.e.
NH\sim10^{23}-10^{24} cm^{-2}. An additional source shows indications of
obscured AGN emission from X-ray data. The comparison between the
mid-IR--derived X-ray luminosities and those obtained from X-ray data suggests
that obscuration is likely present also in the remaining six sources that
harbour an AGN according to the SED-fitting analysis.Comment: 12 pages, including 5 figures. Accepted for publication in MNRA
GOODS-: identification of the individual galaxies responsible for the 80-290m cosmic infrared background
We propose a new method of pushing to its faintest detection
limits using universal trends in the redshift evolution of the far infrared
over 24m colours in the well-sampled GOODS-North field. An extension to
other fields with less multi-wavelength information is presented. This method
is applied here to raise the contribution of individually detected
sources to the cosmic infrared background (CIRB) by a factor 5 close to its
peak at 250m and more than 3 in the 350m and 500m bands. We
produce realistic mock images of the deep PACS and SPIRE images of
the GOODS-North field from the GOODS- Key Program and use them to
quantify the confusion noise at the position of individual sources, i.e.,
estimate a "local confusion noise". Two methods are used to identify sources
with reliable photometric accuracy extracted using 24m prior positions.
The clean index (CI), previously defined but validated here with simulations,
which measures the presence of bright 24m neighbours and the photometric
accuracy index (PAI) directly extracted from the mock images. After
correction for completeness, thanks to our mock images, individually
detected sources make up as much as 54% and 60% of the CIRB in the PACS bands
down to 1.1 mJy at 100m and 2.2 mJy at 160m and 55, 33, and 13% of
the CIRB in the SPIRE bands down to 2.5, 5, and 9 mJy at 250m, 350m,
and 500m, respectively. The latter depths improve the detection limits of
by factors of 5 at 250m, and 3 at 350m and 500m as
compared to the standard confusion limit. Interestingly, the dominant
contributors to the CIRB in all bands appear to be distant siblings
of the Milky Way (0.96 for 300m) with a stellar mass
of 910M.Comment: 22 pages, 16 figures. Accepted for publication by Astronomy and
Astrophysic
PACS Evolutionary Probe (PEP) - A Herschel Key Program
Deep far-infrared photometric surveys studying galaxy evolution and the
nature of the cosmic infrared background are a key strength of the Herschel
mission. We describe the scientific motivation for the PACS Evolutionary Probe
(PEP) guaranteed time key program and its role in the complement of Herschel
surveys, and the field selection which includes popular multiwavelength fields
such as GOODS, COSMOS, Lockman Hole, ECDFS, EGS. We provide an account of the
observing strategies and data reduction methods used. An overview of first
science results illustrates the potential of PEP in providing calorimetric star
formation rates for high redshift galaxy populations, thus testing and
superseeding previous extrapolations from other wavelengths, and enabling a
wide range of galaxy evolution studies.Comment: 13 pages, 12 figures, accepted for publication in A&
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