269 research outputs found
Interstellar Gas and X-rays toward the Young Supernova Remnant RCW 86; Pursuit of the Origin of the Thermal and Non-Thermal X-ray
We have analyzed the atomic and molecular gas using the 21 cm HI and 2.6/1.3
mm CO emissions toward the young supernova remnant (SNR) RCW 86 in order to
identify the interstellar medium with which the shock waves of the SNR
interact. We have found an HI intensity depression in the velocity range
between and km s toward the SNR, suggesting a cavity in the
interstellar medium. The HI cavity coincides with the thermal and non-thermal
emitting X-ray shell. The thermal X-rays are coincident with the edge of the HI
distribution, which indicates a strong density gradient, while the non-thermal
X-rays are found toward the less dense, inner part of the HI cavity. The most
significant non-thermal X-rays are seen toward the southwestern part of the
shell where the HI gas traces the dense and cold component. We also identified
CO clouds which are likely interacting with the SNR shock waves in the same
velocity range as the HI, although the CO clouds are distributed only in a
limited part of the SNR shell. The most massive cloud is located in the
southeastern part of the shell, showing detailed correspondence with the
thermal X-rays. These CO clouds show an enhanced CO = 2-1/1-0 intensity
ratio, suggesting heating/compression by the shock front. We interpret that the
shock-cloud interaction enhances non-thermal X-rays in the southwest and the
thermal X-rays are emitted by the shock-heated gas of density 10-100 cm.
Moreover, we can clearly see an HI envelope around the CO cloud, suggesting
that the progenitor had a weaker wind than the massive progenitor of the
core-collapse SNR RX J1713.73949. It seems likely that the progenitor of RCW
86 was a system consisting of a white dwarf and a low-mass star with
low-velocity accretion winds.Comment: 19 pages, 15 figures, 4 tables, accepted for publication in Journal
of High Energy Astrophysics (JHEAp
Discovery of a low-luminosity spiral DRAGN
Standard galaxy formation models predict that large-scale double-lobed radio
sources, known as DRAGNs, will always be hosted by elliptical galaxies. In
spite of this, in recent years a small number of spiral galaxies have also been
found to host such sources. These so-called spiral DRAGNs are still extremely
rare, with only cases being widely accepted. Here we report on the
serendipitous discovery of a new spiral DRAGN in data from the Giant Metrewave
Radio Telescope (GMRT) at 322 MHz. The host galaxy, MCG+07-47-10, is a face-on
late-type Sbc galaxy with distinctive spiral arms and prominent bulge
suggesting a high black hole mass. Using WISE infra-red and GALEX UV data we
show that this galaxy has a star formation rate of 0.16-0.75
Myr, and that the radio luminosity is dominated by
star-formation. We demonstrate that this spiral DRAGN has similar environmental
properties to others of this class, but has a comparatively low radio
luminosity of = 1.1210 W Hz, two orders
of magnitude smaller than other known spiral DRAGNs. We suggest that this may
indicate the existence of a previously unknown low-luminosity population of
spiral DRAGNS.Comment: 4 pages, Accepted for publication in Astronomy and Astrophysic
Inorbit Performance of the Hard X-ray Telescope (HXT) on board the Hitomi (ASTRO-H) satellite
Hitomi (ASTRO-H) carries two Hard X-ray Telescopes (HXTs) that can focus
X-rays up to 80 keV. Combined with the Hard X-ray Imagers (HXIs) that detect
the focused X-rays, imaging spectroscopy in the high-energy band from 5 keV to
80 keV is made possible. We studied characteristics of HXTs after the launch
such as the encircled energy function (EEF) and the effective area using the
data of a Crab observation. The half power diameters (HPDs) in the 5--80 keV
band evaluated from the EEFs are 1.59 arcmin for HXT-1 and 1.65 arcmin for
HXT-2. Those are consistent with the HPDs measured with ground experiments when
uncertainties are taken into account. We can conclude that there is no
significant change in the characteristics of the HXTs before and after the
launch. The off-axis angle of the aim point from the optical axis is evaluated
to be less than 0.5 arcmin for both HXT-1 and HXT-2. The best-fit parameters
for the Crab spectrum obtained with the HXT-HXI system are consistent with the
canonical values.Comment: 13 pages, 5 figures; the acknowledgment was modifie
The eROSITA Final Equatorial-Depth Survey (eFEDS): X-ray properties of Subaru optically-selected clusters
We present the results of a systematic X-ray analysis of optically rich
galaxy clusters detected by the Subaru HSC survey in the eROSITA eFEDS field.
Through a joint analysis of SRG/eROSITA and Subaru/HSC surveys, we aim to study
the dynamical status of the optically selected clusters and derive the cluster
scaling relations. The sample consists of 43 optically selected galaxy clusters
with a richness in . We systematically analyzed the X-ray
images and spectra using the eROSITA data. We identified the BCG using the
optical and far-infrared databases. We evaluated the cluster's dynamical status
by measuring the offset between the X-ray peak and BCG position, the gas
concentration, and the number of galaxy-density peaks. We studied the
luminosity-temperature and mass-luminosity relations based on eROSITA X-ray
spectra and HSC weak-lensing data analyses. Based on the these measurements,
the fraction of relaxed clusters is %, which is smaller than that of
the X-ray-selected cluster samples. After correcting for a selection bias due
to the richness cut, we obtained a shallow slope of , which is
consistent with the predictions of the self-similar model and the baseline
model incorporating a mass-concentration relation. The slope of
agrees with the above theoretical models and that of the
shear-selected clusters in the eFEDs field. Our analysis of high-richness
optical clusters yields a small fraction of relaxed clusters and a shallow
slope for the luminosity-temperature relation. This suggests that the average
X-ray properties of the optical clusters are likely to be different from those
observed in the X-ray samples. Thus, the joint eROSITA and HSC observations are
a powerful tool in extending the analysis to a larger sample and understanding
the selection effect with a view to establish cluster scaling relations.Comment: 12 pages, 4 figures, A&A accepted, minor correctio
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