8 research outputs found
The role of molecular gas in the nuclear regions of IRAS 00183-7111. ALMA and X-ray investigations of an ultraluminous infrared galaxy
We present a multi-frequency study of the ultraluminous infrared galaxy
(ULIRG) IRAS 00183-7111 (z=0.327), selected from the Spoon diagnostic diagram
as a highly obscured active galactic nucleus (AGN) candidate. ALMA Cycle 0
millimetre and X-ray observations are used; the main aim is to verify at what
level the molecular gas, traced by the CO, may be responsible for the
obscuration observed at X-ray energies. Theory and observations both suggest
that galaxy-scale absorption may play a role in the AGN obscuration at
intermediate (i.e. Compton-thin) column densities. We derived a molecular gas
column density of cm from the ALMA
CO detection, while the best-fit column density of cold gas obtained
from X-ray spectral fitting is cm. The
two quantities suggest that the molecular gas may contribute only a fraction of
the AGN obscuration; however, the link between them is not straightforward. The
nuclear regions of IRAS 00183-7111 are likely stratified into different layers
of matter: one inner and highly ionized by the strong radiation field of the
AGN (as inferred from the high-ionization iron line found in the X-ray
spectra), and one outer and colder, extending more than 5~kpc from the nucleus
(as traced by the molecular gas observed with ALMA). The molecular gas regions
also give rise to a vigorous starburst with SFR M
yr. The complexity of this nuclear environment makes it difficult to
identify the origin of the AGN obscuration given the quality of the data
currently available. Higher resolution observations in the millimetre regime
are needed to deeply investigate this issue.Comment: 15 pages, 7 figures, 5 tables. Accepted for publication in A&
The AGN fuelling/feedback cycle in nearby radio galaxies - I. ALMA observations and early results
This is the first paper of a series exploring the multi-frequency properties
of a sample of eleven nearby low excitation radio galaxies (LERGs) in the
southern sky. We are conducting an extensive study of different galaxy
components (stars, warm and cold gas, radio jets) with the aim of improving our
understanding of the AGN fuelling/feedback cycle in LERGs. We present ALMA Band
6 CO(2-1) and continuum observations of nine sources. Continuum emission
from the radio cores was detected in all objects. Six sources also show mm
emission from jets on kpc/sub-kpc scales. The jet structures are very similar
at mm and cm wavelengths. We conclude that synchrotron emission associated with
the radio jets dominates the continuum spectra up to 230 GHz. The
CO(2-1) line was detected in emission in six out of nine objects, with
molecular gas masses ranging from to
M. The CO detections show disc-like structures on scales from
0.2 to 10 kpc. In one case (NGC 3100) the CO disc presents
some asymmetries and is disrupted in the direction of the northern radio jet,
indicating a possible jet/disc interaction. In IC 4296, CO is detected in
absorption against the radio core, as well as in emission. In four of the six
galaxies with CO detections, the gas rotation axes are roughly parallel to the
radio jets in projection; the remaining two cases show large misalignments. In
those objects where optical imaging is available, dust and CO appear to be
co-spatial.Comment: Accepted for publication in MNRAS. The Appendix is provided as
on-line only supplementary materia
PRISM (Polarized Radiation Imaging and Spectroscopy Mission): A White Paper on the Ultimate Polarimetric Spectro-Imaging of the Microwave and Far-Infrared Sky
PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to
ESA in response to the Call for White Papers for the definition of the L2 and
L3 Missions in the ESA Science Programme. PRISM would have two instruments: (1)
an imager with a 3.5m mirror (cooled to 4K for high performance in the
far-infrared---that is, in the Wien part of the CMB blackbody spectrum), and
(2) an Fourier Transform Spectrometer (FTS) somewhat like the COBE FIRAS
instrument but over three orders of magnitude more sensitive. Highlights of the
new science (beyond the obvious target of B-modes from gravity waves generated
during inflation) made possible by these two instruments working in tandem
include: (1) the ultimate galaxy cluster survey gathering 10e6 clusters
extending to large redshift and measuring their peculiar velocities and
temperatures (through the kSZ effect and relativistic corrections to the
classic y-distortion spectrum, respectively) (2) a detailed investigation into
the nature of the cosmic infrared background (CIB) consisting of at present
unresolved dusty high-z galaxies, where most of the star formation in the
universe took place, (3) searching for distortions from the perfect CMB
blackbody spectrum, which will probe a large number of otherwise inaccessible
effects (e.g., energy release through decaying dark matter, the primordial
power spectrum on very small scales where measurements today are impossible due
to erasure from Silk damping and contamination from non-linear cascading of
power from larger length scales). These are but a few of the highlights of the
new science that will be made possible with PRISM.Comment: 20 pages Late
The ATESP 5 GHz Radio Survey I. Source Counts and spectral index properties of the faint radio population
Context: .The nature and evolutionary properties of the faint radio population, responsible for the steepening observed in the 1.4 GHz source counts below 1 milliJy, are not yet entirely clear. Radio spectral indices may help to constrain the origin of the radio emission in such faint radio sources and may be fundamental in understanding eventual links to the optical light.
Aims: .We study the spectral index behaviour of sources that were found in the 1.4 GHz ATESP survey (Prandoni et al. 2000a, A&AS, 146, 31; 2000b, A&AS, 146, 41), considering that the ATESP is one of the most extensive sub-mJy surveys existing at present.
Methods: .Using the Australia Telescope Compact Array we observed at 5 GHz part of the region covered by the sub-mJy ATESP survey. In particular we imaged a one square degree area for which deep optical imaging in UBVRIJK is available. In this paper we present the 5 GHz survey and source catalogue, we derive the 5 GHz source counts and we discuss the 1.4-5 GHz spectral index properties of the ATESP sources. The analysis of the optical properties of the sample will be the subject of a following paper.
Results: .The 5 GHz survey has produced a catalogue of 111 radio sources, complete down to a (6σ) limit S_lim(5 GHz) ~ 0.4 mJy. We take advantage of the better spatial resolution at 5 GHz (~2 arcsec compared to ~8 arcsec at 1.4 GHz) to infer radio source structures and sizes. The 5 GHz source counts derived by the present sample are consistent with those reported in the literature, but improve significantly the statistics in the flux range 0.4< S5 GHz<1 mJy. The ATESP sources show a flattening of the 1.4-5 GHz spectral index with decreasing flux density, which is particularly significant for the 5 GHz selected sample. Such a flattening confirm previous results coming from smaller samples and is consistent with a flattening of the 5 GHz source counts occurring at fluxes <0.5 mJy
PRISM (Polarized Radiation Imaging and Spectroscopy Mission): an extended white paper
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PRISM (Polarized Radiation Imaging and Spectroscopy Mission): an extended white paper
PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of the ESA Cosmic Vision program a set of important scientific questions that require high resolution, high sensitivity, full-sky observations of the sky emission at wavelengths ranging from millimeter-wave to the far-infrared. PRISM's main objective is to explore the distant universe, probing cosmic history from very early times until now as well as the structures, distribution of matter, and velocity flows throughout our Hubble volume. PRISM will survey the full sky in a large number of frequency bands in both intensity and polarization and will measure the absolute spectrum of sky emission more than three orders of magnitude better than COBE FIRAS. The data obtained will allow us to precisely measure the absolute sky brightness and polarization of all the components of the sky emission in the observed frequency range, separating the primordial and extragalactic components cleanly from the galactic and zodiacal light emissions. The aim of this Extended White Paper is to provide a more detailed overview of the highlights of the new science that will be made possible by PRISM, which include: (1) the ultimate galaxy cluster survey using the Sunyaev-Zeldovich (SZ) effect, detecting approximately 10 6 clusters extending to large redshift, including a characterization of the gas temperature of the brightest ones (through the relativistic corrections to the classic SZ template) as well as a peculiar velocity survey using the kinetic SZ effect that comprises our entire Hubble volume; (2) a detailed characterization of the properties and evolution of dusty galaxies, where the most of the star formation in the universe took place, the faintest population of which constitute the diffuse CIB (Cosmic Infrared Background); (3) a characterization of the B modes from primordial gravity waves generated during inflation and from gravitational lensing, as well as the ultimate search for primordial non-Gaussianity using CMB polarization, which is less contaminated by foregrounds on small scales than the temperature anisotropies; (4) a search for distortions from a perfect blackbody spectrum, which include some nearly certain signals and others that are more speculative but more informative; and (5) a study of the role of the magnetic field in star formation and its interaction with other components of the interstellar medium of our Galaxy. These are but a few of the highlights presented here along with a description of the proposed instrument