6,544 research outputs found
Recombining Plasma & Gamma-ray Emission in the Mixed-morphology Supernova Remnant 3C 400.2
3C 400.2 belongs to the mixed morphology supernova remnant class, showing
center-filled X-ray and shell-like radio morphology. We present a study of 3C
400.2 with archival Suzaku and Fermi-LAT observations. We find recombining
plasma (RP) in the Suzaku spectra of north-east and south-east regions. The
spectra of these regions are well described by two-component thermal plasma
models: The hard component is in RP, while the soft component is in collisional
ionization equilibrium (CIE) conditions. The RP has enhanced abundances
indicating that the X-ray emission has an ejecta origin, while the CIE has
solar abundances associated with the interstellar material. The X-ray spectra
of north-west and south-west regions are best fitted by a two-component thermal
plasma model: an ionizing and a CIE plasma. We have detected GeV gamma-ray
emission from 3C 400.2 at the level of 5 assuming a point-like
source model with a power-law (PL) type spectrum. We have also detected a new
GeV source at the level of 13 assuming a Gaussian extension model
with a PL type spectrum in the neighborhood of the SNR. We report the analysis
results of 3C 400.2 and the new extended gamma-ray source and discuss the
nature of gamma-ray emission of 3C 400.2 in the context of existing NANTEN CO
data, DRAO HI data, and the Suzaku X-ray analysis results.Comment: Accepted to be published in the Astrophysical Journa
Catalogue of 12CO(J=1-0) and 13CO(J=1-0) Molecular Clouds in the Carina Flare Supershell
We present a catalogue of 12CO(J=1-0) and 13CO(J=1-0) molecular clouds in the
spatio-velocity range of the Carina Flare supershell, GSH 287+04-17. The data
cover a region of ~66 square degrees and were taken with the NANTEN 4m
telescope, at spatial and velocity resolutions of 2.6' and 0.1 km/s.
Decomposition of the emission results in the identification of 156 12CO clouds
and 60 13CO clouds, for which we provide observational and physical parameters.
Previous work suggests the majority of the detected mass forms part of a
comoving molecular cloud complex that is physically associated with the
expanding shell. The cloud internal velocity dispersions, degree of
virialization and size-linewidth relations are found to be consistent with
those of other Galactic samples. However, the vertical distribution is heavily
skewed towards high-altitudes. The robust association of high-z molecular
clouds with a known supershell provides some observational backing for the
theory that expanding shells contribute to the support of a high-altitude
molecular layer.Comment: To be published in PASJ Vol. 60, No. 6. (Issued on December 25th
2008). 35 pages (including 13 pages of tables), 7 figures. Please note that
formatting problems with the journal macro result in loss of rightmost data
columns in some long tables. These will be fixed in the final published
issue. In the meantime, please contact the authors for missing dat
Magneto-hydrodynamic Simulations of a Jet Drilling an HI Cloud: Shock Induced Formation of Molecular Clouds and Jet Breakup
The formation mechanism of the jet-aligned CO clouds found by NANTEN CO
observations is studied by magnetohydrodynamical (MHD) simulations taking into
account the cooling of the interstellar medium. Motivated by the association of
the CO clouds with the enhancement of HI gas density, we carried out MHD
simulations of the propagation of a supersonic jet injected into the dense HI
gas. We found that the HI gas compressed by the bow shock ahead of the jet is
cooled down by growth of the cooling instability triggered by the density
enhancement. As a result, cold dense sheath is formed around the interface
between the jet and the HI gas. The radial speed of the cold, dense gas in the
sheath is a few km/s almost independent of the jet speed. Molecular clouds can
be formed in this region. Since the dense sheath wrapping the jet reflects
waves generated in the cocoon, the jet is strongly perturbed by the vortices of
the warm gas in the cocoon, which breaks up the jet and forms a secondary shock
in the HI-cavity drilled by the jet. The particle acceleration at the shock can
be the origin of radio and X-ray filaments observed near the eastern edge of
W50 nebula surrounding the galactic jet source SS433.Comment: 30 pages, 16 figure
Arguments against a dominantly hadronic origin of the VHE radiation from the supernova remnant RX J1713-3946
The flux of photons with energies above 1 TeV from the direction of the
centre and a cloud in the western part of the nearby southern supernova remnant
(SNR) RX J1713.7-3946 is calculated in the ``hadronic scenario'' that aims to
explain the intense VHE radiation from this remnant with the decay of \pi_0
pions produced in nuclear collisions. The expected flux from its centre is
found to fall short by about factor 40 from the one observed by the HESS
collaboration. This discrepancy presents a serious obstacle to the ``hadronic
scenario''. The theoretically expected flux from the molecular cloud exceeds
the one observed by HESS by at least a factor 3. While the size of this
discrepancy might still seem acceptable in the face of various theoretical
uncertainties, the result strongly suggests a strict spatial correlation of the
cloud with an excess of TeV \gamma radiation. The observational lack of such
correlations in the remnant reported by HESS is another counter argument
against the hadronic scenario. In combination these arguments cannot be refuted
by choosing certain parameters for the total energy or acceleration efficiency
of the SNR.Comment: 8 pages, small clarification and one footnote added to the published
versio
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