187 research outputs found
The PEP Survey: evidence for intense star-forming activity in the majority of radio-selected AGN at z>~1
In order to investigate the FIR properties of radio-active AGN, we have
considered three different fields where both radio and FIR observations are the
deepest to-date: GOODS-South, GOODS-North and the Lockman Hole. Out of a total
of 92 radio-selected AGN, ~64% are found to have a counterpart in Herschel
maps. The percentage is maximum in the GOODS-North (72%) and minimum (~50%) in
the Lockman Hole, where FIR observations are shallower. Our study shows that in
all cases FIR emission is associated to star-forming activity within the host
galaxy. Such an activity can even be extremely intense, with star-forming rates
as high as ~10^3-10^4 Msun/yr. AGN activity does not inhibit star formation in
the host galaxy, just as on-site star-formation does not seem to affect AGN
properties, at least those detected at radio wavelengths and for z>~1.
Furthermore, physical properties such as the mass and age distributions of the
galaxies hosting a radio-active AGN do not seem to be affected by the presence
of an ongoing star-forming event. Given the very high rate of FIR detections,
we stress that this refers to the majority of the sample: most radio-active AGN
are associated with intense episodes of star-formation. However, the two
processes proceed independently within the same galaxy, at all redshifts but in
the local universe, where powerful enough radio activity reaches the necessary
strength to switch off the on-site star formation. Our data also show that for
z>~1 the hosts of radio-selected star-forming galaxies and AGN are
indistinguishable from each other both in terms of mass and IR luminosity
distributions. The two populations only differentiate in the very local
universe, whereby the few AGN which are still FIR-active are found in galaxies
with much higher masses and luminosities.Comment: 20 pages, 22 figures, to appear in MNRA
Star formation and quenching among the most massive galaxies at z~1.7
We have conducted a detailed object-by-object study of a mass-complete
(M*>10^11 M_sun) sample of 56 galaxies at 1.4 < z < 2 in the GOODS-South field,
showing that an accurate de-blending in MIPS/24um images is essential to
properly assign to each galaxy its own star formation rate (SFR), whereas an
automatic procedure often fails. This applies especially to galaxies with SFRs
below the Main Sequence (MS) value, which may be in their quenching phase.
After that, the sample splits evenly between galaxies forming stars within a
factor of 4 of the MS rate (~45%), and sub-MS galaxies with SFRs ~10-1000 times
smaller (~55%). We did not find a well defined class of intermediate, transient
objects below the MS, suggesting that the conversion of a massive MS galaxy
into a quenched remnant may take a relatively short time (<1 Gyr), though a
larger sample should be analyzed in the same way to set precise limits on the
quenching timescale. X-ray detected AGNs represent a ~30% fraction of the
sample, and are found among both star-forming and quenched galaxies. The
morphological analysis revealed that ~50% of our massive objects are
bulge-dominated, and almost all MS galaxies with a relevant bulge component
host an AGN. We also found sub-MS SFRs in many bulge-dominated systems,
providing support to the notion that bulge growth, AGN activity and quenching
of star formation are closely related to each other.Comment: 27 pages, 19 figures, accepted for publication by MNRA
Long-term survival in high-grade axial osteosarcoma with bone and lung metastases treated with chemotherapy only
NIR Spectroscopy of Luminous Infrared Galaxies and the Hydrogen Recombination Photon Deficit
We report on near-infrared medium-resolution spectroscopy of a sample of
luminous and ultra luminous infrared galaxies (LIRGs-ULIRGs), carried out with
SOFI at the ESO 3.5m New Technology Telescope. Because of wavelength dependence
of the attenuation, the detection of the Pa_alfa or Br_gamma line in the Ks
band should provide relevant constraints on SFR and the contribution of an AGN.
We find, however, that the intensities of the Pa_alfa and Br_gamma lines, even
corrected for slit losses, are on average only 10% and 40%, respectively, of
that expected from a normal starburst of similar bolometric luminosity. The
corresponding star formation rates, after correcting for the attenuation
derived from the NIR-optical emission line ratios, are 14% and 60% of that
expected if the far infrared luminosity were entirely powered by the starburst.
This confirms the existence of a recombination photon deficit, particularly in
the case of the Pa_alfa line, already found in the Br_gamma line in other
infrared galaxies of similar luminosity. In discussing the possible causes of
the discrepancy, we find unlikely that it is due to the presence of an AGN,
though two objects show evidence of broadening of the Pa_alfa line and of the
presence of coronal line emission. In fact, from our own observations and data
collected from the literature we argue that the studied galaxies appear to be
predominantly powered by a nuclear starburst. Two scenarios compatible with the
present data are that either there exists a highly attenuated nuclear star
forming region, and/or that a significant fraction of the ionizing photons are
absorbed by dust within the HII regions. We suggest that observations in the
Br_alpha spectral region could constitute a powerful tool to disentangle these
two possibilities.Comment: 14 pages, accepted by A&
Photometric Redshifts of Submillimeter Galaxies
We use the photometric redshift method of Chakrabarti & McKee (2008) to infer
photometric redshifts of submillimeter galaxies with far-IR (FIR)
data obtained as part of the PACS Evolutionary Probe (PEP)
program. For the sample with spectroscopic redshifts, we demonstrate the
validity of this method over a large range of redshifts ( 4 \ga z \ga 0.3)
and luminosities, finding an average accuracy in of 10%. Thus, this method is more accurate than other FIR photometric
redshift methods. This method is different from typical FIR photometric methods
in deriving redshifts from the light-to-gas mass () ratio of
infrared-bright galaxies inferred from the FIR spectral energy distribution
(SED), rather than dust temperatures. Once the redshift is derived, we can
determine physical properties of infrared bright galaxies, including the
temperature variation within the dust envelope, luminosity, mass, and surface
density. We use data from the GOODS-S field to calculate the star formation
rate density (SFRD) of sub-mm bright sources detected by AzTEC and PACS. The
AzTEC-PACS sources, which have a threshold 850 \micron flux \ga 5 \rm mJy,
contribute 15% of the SFRD from all ULIRGs (L_{\rm IR} \ga 10^{12}
L_{\odot}), and 3% of the total SFRD at .Comment: 7 pages, 2 figures, submitted to Ap
A serious game architecture for green mobility
Good driving behavior is a significant factor for road safety and green mobility. A countermeasure to overcome the coarse driving behavior and a methodology to captivate optimal driving traits are discussed in this work. For which, the serious games concept was exploited to improvise the driver performance by deploying diversified game logics (scores, incentives and live game for performance evolution) on a smartphone-based user interface. The application was tested in ASTA ZERO (Active Safety Test Area) in Sweden. The tests comprised of variations (good and bad driving behavior) in driving pattern for analyzing the impact of the application on the driver performance
The spectral energy distribution of quiescent black hole X-ray binaries: new constraints from Spitze
Among the various issues that remain open in the field of accretion onto black hole X-ray binaries (BHBs) is the question of how gas accretes at very low Eddington ratios, in the so-called quiescent regime. While there is general agreement that X-rays are produced by a population of high-energy electrons near the BH, there is controversy concerning the modeling of the contributions of inflowing versus outflowing particles and their relative energy budget. Recent Spitzer observations of three quiescent BHBs have shown evidence for excess emission with respect to the Rayleigh-Jeans tail of the companion star between 8-24 μm. We suggest that synchrotron emission from a partially self-absorbed outflow might be responsible for the observed mid-IR excess, in place of, or in addition to, thermal emission from circumbinary material. If so, then the jet synchrotron luminosity, integrated from radio to near-IR frequencies, exceeds the measured 2-10 keV luminosity by a factor of a few in these systems. In turn, the mechanical power stored in the jet exceeds the bolometric X-ray luminosity by at least 4 orders of magnitude. We compile the broadband spectral energy distribution (SED) of A0620-00, the lowest Eddington-ratio stellar mass BH with a known radio counterpart, by means of simultaneous radio, optical, and X-ray observations, and the archival Spitzer data. We are able to fit the SED of A0620-00 with a maximally jet-dominated model, in which the radio through the soft X-rays are dominated by synchrotron emission, while the hard X-rays are dominated by inverse Compton at the jet base. The fitted parameters land in a range of values reminiscent of the Galactic center supermassive black hole Sgr A*. Most notably, the inferred ratio of the jet acceleration rate to local cooling rates is 2 orders of magnitude weaker than higher luminosity, hard-state sources
SXDF-ALMA 1.5 arcmin^2 deep survey. A compact dusty star-forming galaxy at z=2.5
We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1
mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth
of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19
or z=2.53. We have detected continuum emission from three of our
Halpha-selected sample, including one compact star-forming galaxy with high
stellar surface density, NB2315-07. They are all red in the rest-frame optical
and have stellar masses of log (M*/Msun)>10.9 whereas the other blue,
main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290
uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02,
to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming
component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high
star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the
concentrated starburst can within less than 50^{+12}_{-11} Myr build up a
stellar surface density matching that of massive compact galaxies at z~2,
provided at least 19+-3% of the total gas is converted into stars in the galaxy
centre. On the other hand, NB2315-07, which already has such a high stellar
surface density core, shows a gas fraction (23+-8%) and is located in the lower
envelope of the star formation main-sequence. This compact less star-forming
galaxy is likely to be in an intermediate phase between compact dusty
star-forming and quiescent galaxies.Comment: 6 pages, 4 figures, 1 table, accepted for publication in ApJ
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