112 research outputs found
The location and impact of jet-driven outflows of cold gas: the case of 3C293
The nearby radio galaxy 3C293 is one of a small group of objects where
extreme outflows of neutral hydrogen have been detected. However, due to the
limited spatial resolution of previous observations, the exact location of the
outflow was not able to be determined. In this letter, we present new higher
resolution VLA observations of the central regions of this radio source and
detect a fast outflow of HI with a FWZI velocity of \Delta v~1200 km/s
associated with the inner radio jet, approximately 0.5 kpc west of the central
core. We investigate possible mechanisms which could produce the observed HI
outflow and conclude that it is driven by the radio-jet. However, this outflow
of neutral hydrogen is located on the opposite side of the nucleus to the
outflow of ionised gas previously detected in this object. We calculate a mass
outflow rate in the range of 8-50 solar masses/yr corresponding to a kinetic
energy power injected back into the ISM of 1.38x10^{42} - 1.00x10^{43} erg/s or
0.01 - 0.08 percent of the Eddington luminosity. This places it just outside
the range required by some galaxy evolution simulations for negative feedback
from the AGN to be effective in halting star-formation within the galaxy.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter
New Associations of Gamma-Ray Sources from the Fermi Second Source Catalog
We present the results of an all-sky radio survey between 5 and 9 GHz of the
fields surrounding all unassociated gamma-ray objects listed in the Fermi Large
Area Telescope Second Source Catalog (2FGL). The goal of these observations is
to find all new gamma-ray AGN associations with radio sources >10 mJy at 8 GHz.
We observed with the Very Large Array and the Australia Telescope Compact Array
the areas around unassociated sources, providing localizations of weak radio
point sources found in 2FGL fields at arcmin scales. Then we followed-up a
subset of those with the Very Long Baseline and the Long Baseline Arrays to
confirm detections of radio emission on parsec-scales. We quantified
association probabilities based on known statistics of source counts and
assuming a uniform distribution of background sources. In total we found 865
radio sources at arcsec scales as candidates for association and detected 95 of
170 selected for follow-up observations at milliarcsecond resolution. Based on
this we obtained firm associations for 76 previously unknown gamma-ray AGN.
Comparison of these new AGN associations with the predictions from using the
WISE color-color diagram shows that half of the associations are missed. We
found that 129 out of 588 observed gamma-ray sources at arcmin scales not a
single radio continuum source was detected above our sensitivity limit within
the 3-sigma gamma-ray localization. These "empty" fields were found to be
particularly concentrated at low Galactic latitudes. The nature of these
Galactic gamma-ray emitters is not yet determined.Comment: accepted for publication by ApJS, 18 pages, 10 figures, 12 tables;
full electronic versions of tables 2-8 are available as ancillary file
Optical Properties of High-Frequency Radio Sources from the Australia Telescope 20 GHz (AT20G) Survey
Our current understanding of radio-loud AGN comes predominantly from studies
at frequencies of 5 GHz and below. With the recent completion of the Australia
Telescope 20 GHz (AT20G) survey, we can now gain insight into the
high-frequency radio properties of AGN. This paper presents supplementary
information on the AT20G sources in the form of optical counterparts and
redshifts. Optical counterparts were identified using the SuperCOSMOS database
and redshifts were found from either the 6dF Galaxy survey or the literature.
We also report 144 new redshifts. For AT20G sources outside the Galactic plane,
78.5% have optical identifications and 30.9% have redshift information. The
optical identification rate also increases with increasing flux density.
Targets which had optical spectra available were examined to obtain a spectral
classification.
There appear to be two distinct AT20G populations; the high luminosity
quasars that are generally associated with point-source optical counterparts
and exhibit strong emission lines in the optical spectrum, and the lower
luminosity radio galaxies that are generally associated with passive galaxies
in both the optical images and spectroscopic properties. It is suggested that
these different populations can be associated with different accretion modes
(cold-mode or hot-mode). We find that the cold-mode sources have a steeper
spectral index and produce more luminous radio lobes, but generally reside in
smaller host galaxies than their hot-mode counterparts. This can be attributed
to the fact that they are accreting material more efficiently. Lastly, we
compare the AT20G survey with the S-cubed semi-empirical (S3-SEX) models and
conclude that the S3-SEX models need refining to correctly model the compact
cores of AGN. The AT20G survey provides the ideal sample to do this.Comment: Accepted for publication in MNRA
An HI absorption distance to the black hole candidate X-ray binary MAXI J1535-571
With the Australian Square Kilometre Array Pathfinder (ASKAP) we monitored
the black hole candidate X-ray binary MAXI J1535--571 over seven epochs from 21
September to 2 October 2017. Using ASKAP observations, we studied the HI
absorption spectrum from gas clouds along the line-of-sight and thereby
constrained the distance to the source. The maximum negative radial velocities
measured from the HI absorption spectra for MAXI J1535--571 and an
extragalactic source in the same field of view are km s and
km s, respectively. This rules out the far kinematic distance
( kpc), giving a most likely distance of
kpc, with a strong upper limit of the tangent point at kpc.
At our preferred distance, the peak unabsorbed luminosity of MAXI J1535--571
was per cent of the Eddington luminosity, and shows that the soft-to-hard
spectral state transition occurred at the very low luminosity of 1.2 -- 3.4
10 times the Eddington luminosity. Finally, this study
highlights the capabilities of new wide-field radio telescopes to probe
Galactic transient outbursts, by allowing us to observe both a target source
and a background comparison source in a single telescope pointing.Comment: Revised after favorable referee report from MNRAS Letter
“Peas in a pod”: Oral History Reflections on Autistic Identity in Family and Community by Late-Diagnosed Adults
In this paper, we report on a participatory oral history study documenting the lives of late-diagnosed autistic adults in Australia. We interviewed 26 autistic adults about their life history and the impact of late diagnosis. All were diagnosed after the age of 35, growing up in an era when autism was not well known. Using reflexive thematic analysis, we uncovered a rich body of reflections on shared Autistic identity and identified three major themes within that data set: 'conceptualising the Autistic family', 'creating Autistic community', and 'contesting Autistic identity'. Overall, the study provides insights into the active creation of shared Autistic identity and the importance of Autistic community to these late-diagnosed autistic adults
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