scholarly journals 4.14. Molecular shell formation by supernova remnants in the Galactic center—what we learn from the case of W44

1998 ◽  
Vol 184 ◽  
pp. 195-196
Author(s):  
Masumichi Seta ◽  
Gisbert Winnewisser ◽  
Tetsuo Hasegawa ◽  
Glenn J. White ◽  
Tomoharu Oka
Keyword(s):  
High Resolution ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Shell Structures ◽  
Shell Formation ◽  
Considerable Fraction ◽  
Good Place

Recent high resolution CO images of the Galactic center (GC) molecular clouds reveal many arc and/or shell structures (Oka et al. 1997). A considerable fraction of them may most probably be formed by an interaction between supernova remnants (SNRs) and molecular clouds. Studies of such cases in less confused areas are needed to clarify this picture. The SNR W44 is a good place for examining the SNR induced shell formation scenario.

High resolution IRAS images of large shells around Wolf-Rayet stars

1995 ◽  
Vol 163 ◽  
pp. 74-75
Author(s):  
Arturo Manchado ◽  
Guillermo García-Segura ◽  
You-Hua Chu
Keyword(s):  
High Resolution ◽  
Supernova Remnants ◽  
Main Sequence ◽  
Shell Structures ◽  
Ring Structures ◽  
Fossil Shell

High-resolution IRAS images, processed by HIRES, are ideal for the search of large, cold, fossil shell structures around Wolf-Rayet stars. In our preliminary effort, we have confirmed the large, 1.°5 — 2°, ring structures around NGC 6888 and RCW 58, which are clearly shown in the HIRES processed images. We interpret them as fossil bubbles blown by the main-sequence progenitors of the WR stars, although these large shells were previously suggested to be evolved supernova remnants.

scholarly journals Deep Radio Imaging with MERLIN of the Supernova Remnants in M82

2005 ◽  
Vol 192 ◽  
pp. 227-231
Author(s):  
T.W.B. Muxlow ◽  
A. Pedlar ◽  
J.D. Riley ◽  
A.R. McDonald ◽  
R.J. Beswick ◽  
...  
Keyword(s):  
High Resolution ◽  
Supernova Remnants ◽  
Shell Structures ◽  
Starburst Galaxy ◽  
Radio Structure ◽  
High Resolution Image ◽  
Radio Imaging ◽  
Wide Range ◽  
Deep Integration ◽  
First Time

SummaryAn 8 day MERLIN deep integration at 5GHz of the central region of the starburst galaxy M82 has been used to investigate the radio structure of a number of supernova remnants in unprecedented detail revealing new shells and partial shell structures for the first time. In addition, by comparing the new deep 2002 image with an astrometrically aligned image from 36 hours of data taken in 1992, it has been possible to directly measure the expansion velocities of 4 of the most compact remnants in M82. For the two most compact remnants, 41.95+575 and 43.31+592, expansion velocities of 2800 ± 300 km s-1 and 8750 ± 400kms-1have been derived. These confirm and refine the measured expansion velocities which have been derived from VLBI multi-epoch studies. For remnants 43.18+583 and 44.01+596, expansion velocities of 10500 ± 750km s-1 and 2400 ± 250 kms-1have been measured for the first time. In addition, the peak of the radio emission for SNR 45.17+612 has moved between the two epochs implying velocities around 7500km s-1. The relatively compact remnants in M82 are thus found to be expanding over a wide range of velocities which appear unrelated to their size. The new 2002 map is the most sensitive high-resolution image yet made of M82, achieving an rms noise level of 17μJy beam-1. This establishes a first epoch for subsequent deep studies of expansion velocities for many SNR within M82.

scholarly journals Supernova OH (1720 MHz) masers in Sgr A East, W28 and G359.1-0.5

2002 ◽  
Vol 206 ◽  
pp. 212-216
Author(s):  
F. Yusef-Zadeh ◽  
D.A. Roberts ◽  
Geoff Bower ◽  
M. Wardle ◽  
W.M. Goss
Keyword(s):  
Linear Polarization ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Main Line ◽  
Maser Emission ◽  
New Class ◽  
Sgr A ◽  
Maser Sources

A new class of OH (1720 MHz) masers unaccompanied by main-line transitions have recently been discovered (Frail, Goss and Slysh 1994). These masers lie at the interface between supernova remnants (SNRs) interacting with molecular clouds. We discuss three new aspects of SN masers found in the direction toward the Galactic center: (i) the detection of a new −130 kms−1 OH (1720 MHz) maser in the southern lobe of the molecular ring at the Galactic center: (ii) the detection of extended OH (1720 MHz) maser emission from W28 accompanying the compact maser sources and (iii) the detection of linear polarization of the brightest OH (1720 MHz) maser in SNR G359.1-0.5.

scholarly journals Methanol masers in Galactic center region supernova remnants

2013 ◽  
Vol 9 (S303) ◽  
pp. 156-158
Author(s):  
Y. M. Pihlström ◽  
B. C. McEwen ◽  
L. O. Sjouwerman
Keyword(s):  
Molecular Clouds ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Cosmic Ray ◽  
Large Array ◽  
Very Large Array ◽  
Center Region ◽  
Cosmic Ray Acceleration ◽  
Methanol Masers ◽  
Sgr A

AbstractMethanol masers can be used to constrain densities and estimate kinematical distances to supernova remnants (SNRs), important parameters in cosmic ray acceleration models. With the goal of testing those models both for SNRs inside and outside the Galactic center (GC) region, we have used the Very Large Array to search for 36 GHz and 44 GHz methanol lines in Galactic SNRs. We report on the overall results of the maser search, and in particular the results of the GC SNR G1.4–0.1 in which more than 40 masers were found. They may be due to interactions between the SNR and at least two separate molecular clouds. Methanol masers were also detected in W28 and in Sgr A East.

scholarly journals Are Supernovae Responsible for the Gamma Ray Spectrum from the Galactic Center?

2014 ◽  
Vol 1 (1) ◽  
pp. 189-193
Author(s):  
Todor Stanev
Keyword(s):  
Molecular Clouds ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Center ◽  
Large Fraction ◽  
Giant Molecular Clouds ◽  
Galactic Longitude

We discuss the supernova remnants distribution as a function of the galactic longitude and compare their positions to that of the detected TeV gamma ray sources. A large fraction of these sources either coincide or a close by known supernova remnants. If we look within 10<sup>o</sup> of the Galactic center most identied sources are combinations of supernova remnants with giant molecular clouds. The diffuse gamma ray flux from the direction of the Galactic center is much smaller.

scholarly journals Molecules in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 415-420 ◽  
Author(s):  
R. S. Booth ◽  
Th. De Graauw
Keyword(s):  
High Resolution ◽  
Molecular Clouds ◽  
Short Review ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Giant Molecular Clouds ◽  
Interstellar Molecules ◽  
First Time ◽  
Excitation Conditions

In this short review we describe recent new observations of millimetre transitions of molecules in selected regions of the Magellanic Clouds. The observations were made using the Swedish-ESO Submillimetre Telescope, SEST, (Booth et al. 1989), the relatively high resolution of which facilitates, for the first time, observations of individual giant molecular clouds in the Magellanic Clouds. We have mapped the distribution of the emission from the two lowest rotational transitions of 12CO and 13CO and hence have derived excitation conditions for the molecule. In addition, we have observed several well-known interstellar molecules in the same regions, thus doubling the number of known molecules in the Large Magellanic Cloud (LMC). The fact that all the observations have been made under controlled conditions with the same telescope enables a reasonable intercomparison of the molecular column densities. In particular, we are able to observe the relative abundances among the different isotopically substituted species of CO.

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

scholarly journals Low frequency (74 MHz) radio continuum observations of the inner 13° × 7° of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 464-466
Author(s):  
M. Rickert ◽  
F. Yusef-Zadeh ◽  
C. Brogan
Keyword(s):  
High Resolution ◽  
Molecular Cloud ◽  
Supernova Remnant ◽  
Galactic Center ◽  
Low Frequency ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
Image Displays ◽  
Western Side

AbstractWe analyze a high resolution (114″ × 60″) 74 MHz image of the Galactic center taken with the Very Large Array (VLA). We have identified several absorption and emission features in this region, and we discuss preliminary results of two Galactic center sources: the Sgr D complex (G1.1–0.1) and the Galactic center lobe (GCL).The 74 MHz image displays the thermal and nonthermal components of Sgr D and we argue the Sgr D supernova remnant (SNR) is consistent with an interaction with a nearby molecular cloud and the location of the Sgr D Hii region on the near side of the Galactic center. The image also suggests that the emission from the eastern side of the GCL contains a mixture of both thermal and nonthermal sources, whereas the western side is primarily thermal.

scholarly journals ALMA view of the circumnuclear disk of the Galactic Center: tidally disrupted molecular clouds falling to the Galactic Center

2018 ◽  
Vol 70 (5) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Takahiro Tsutsumi ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Circumnuclear Disk
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