5,899 research outputs found
Detection of Extremely Broad Water Emission from the molecular cloud interacting Supernova Remnant G349.7+0.2
We performed Herschel HIFI, PACS and SPIRE observations towards the molecular
cloud interacting supernova remnant G349.7+0.2. An extremely broad emission
line was detected at 557 GHz from the ground state transition 1_{10}-1_{01} of
ortho-water. This water line can be separated into three velocity components
with widths of 144, 27 and 4 km/s. The 144 km/s component is the broadest water
line detected to date in the literature. This extremely broad line width shows
importance of probing shock dynamics. PACS observations revealed 3 additional
ortho-water lines, as well as numerous high-J carbon monoxide (CO) lines. No
para-water lines were detected. The extremely broad water line is indicative of
a high velocity shock, which is supported by the observed CO rotational diagram
that was reproduced with a J-shock model with a density of 10^4 cm^{-3} and a
shock velocity of 80 km/s. Two far-infrared fine-structure lines, [O~I] at 145
micron and [C~II] line at 157 micron, are also consistent with the high
velocity J-shock model. The extremely broad water line could be simply from
short-lived molecules that have not been destroyed in high velocity J-shocks;
however, it may be from more complicated geometry such as high-velocity water
bullets or a shell expanding in high velocity. We estimate the CO and H2O
densities, column densities, and temperatures by comparison with RADEX and
detailed shock models. Detection of Extremely Broad Water Emission from the
molecular cloud interacting Supernova Remnant G349.7+0.
Discovery of Broad Molecular lines and of Shocked Molecular Hydrogen from the Supernova Remnant G357.7+0.3: HHSMT, APEX, Spitzer and SOFIA Observations
We report a discovery of shocked gas from the supernova remnant (SNR)
G357.7+0.3. Our millimeter and submillimeter observations reveal broad
molecular lines of CO(2-1), CO(3-2), CO(4-3), 13CO (2-1) and 13CO (3-2), HCO^+
and HCN using HHSMT, Arizona 12-Meter Telescope, APEX and MOPRA Telescope. The
widths of the broad lines are 15-30 kms, and the detection of such broad lines
is unambiguous, dynamic evidence showing that the SNR G357.7+0.3 is interacting
with molecular clouds. The broad lines appear in extended regions (>4.5'x5').
We also present detection of shocked H2 emission in mid-infrared but lacking
ionic lines using the Spitzer IRS observations to map a few arcmin area. The H2
excitation diagram shows a best-fit with a two-temperature LTE model with the
temperatures of ~200 and 660 K. We observed [C II] at 158um and high-J
CO(11-10) with the GREAT on SOFIA. The GREAT spectrum of [C II], a 3 sigma
detection, shows a broad line profile with a width of 15.7 km/s that is similar
to those of broad CO molecular lines. The line width of [C~II] implies that
ionic lines can come from a low-velocity C-shock. Comparison of H2 emission
with shock models shows that a combination of two C-shock models is favored
over a combination of C- and J-shocks or a single shock. We estimate the CO
density, column density, and temperature using a RADEX model. The best-fit
model with n(H2) = 1.7x10^{4} cm^{-3}, N(CO) = 5.6x10^{16} cm^{-2}, and T = 75
K can reproduce the observed millimeter CO brightnesses.Comment: 19 pages, 22 figure
The First Fermi-LAT SNR Catalog SNR and Cosmic Ray Implications
Galactic cosmic ray (CRs) sources, classically proposed to be Supernova
Remnants (SNRs), must meet the energetic particle content required by direct
measurements of high energy CRs. Indirect gamma-ray measurements of SNRs with
the Fermi Large Area Telescope (LAT) have now shown directly that at least
three SNRs accelerate protons. With the first Fermi LAT SNR Catalog, we have
systematically characterized the GeV gamma-rays emitted by 279 SNRs known
primarily from radio surveys. We present these sources in a multiwavelength
context, including studies of correlations between GeV and radio size, flux,
and index, TeV index, and age and environment tracers, in order to better
understand effects of evolution and environment on the GeV emission. We show
that previously sufficient models of SNRs' GeV emission no longer adequately
describe the data. To address the question of CR origins, we also examine the
SNRs' maximal CR contribution assuming the GeV emission arises solely from
proton interactions. Improved breadth and quality of multiwavelength data,
including distances and local densities, and more, higher resolution gamma-ray
data with correspondingly improved Galactic diffuse models will strengthen this
constraint.Comment: 8 pages, 10 figures; in Proceedings of the 34th International Cosmic
Ray Conference (ICRC 2015), The Hague (The Netherlands
Extended OH(1720 MHz) Maser Emission from Supernova Remnants
Compact OH(1720 MHz) masers have proven to be excellent signposts for the
interaction of supernova remnants with adjacent molecular clouds. Less
appreciated has been the weak, extended OH(1720 MHz) emission which accompanies
strong compact maser sources. Recent single-dish and interferometric
observations reveal the majority of maser-emitting supernova remnants have
accompanying regions of extended maser emission. Enhanced OH abundance created
by the passing shock is observed both as maser emission and absorption against
the strong background of the remnant. Modeling the observed OH profiles gives
an estimate of the physical conditions in which weak, extended maser emission
arises. I will discuss how we can realize the utility of this extended maser
emission, particularly the potential to measure the strength of the post-shock
magnetic field via Zeeman splitting over these large-scales.Comment: 5 Pages, 2 Figures, To appear in IAU 242, Astrophysical Masers and
Their Environments, eds. J. Chapman & W. Baa
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