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 Class I methanol masers in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 147-149
Author(s):  
L. O. Sjouwerman ◽  
Y. M. Pihlström
Keyword(s):  
Galactic Center ◽  
Class I ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Sagittarius A ◽  
Current Location ◽  
Theoretical Predictions ◽  
Methanol Masers ◽  
Sgr A

AbstractWe report on the detection of 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) complex with the Karl G. Jansky Very Large Array (VLA). These VLA observations show that the Sgr A complex harbors at least three different maser tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH3OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

scholarly journals Class I Methanol Masers in the Galactic Center

2012 ◽  
Vol 8 (S287) ◽  
pp. 449-454
Author(s):  
Loránt O. Sjouwerman ◽  
Ylva M. Pihlström
Keyword(s):  
Galactic Center ◽  
Class I ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Sagittarius A ◽  
Wave Radio ◽  
Theoretical Predictions ◽  
Methanol Masers ◽  
Sgr A

AbstractWe report on 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) region with the Expanded Very Large Array (EVLA). At least three different maser transitions tracing shocked regions in the cm-wave radio regime can be found in Sgr A. 44 GHz masers correlate with the positions and velocities of 36 GHz CH3OH masers, but the methanol masers correlate less with 1720 MHz OH masers. Our results agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under cooler or denser conditions. We speculate that the geometry of the bright 36 GHz masers in Sgr A East outlines the location of a SNR shock front.

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 Gas Feeding Toward the Galactic Center

1994 ◽  
Vol 140 ◽  
pp. 161-165
Author(s):  
P. T. P. Ho
Keyword(s):  
Black Hole ◽  
Gravitational Field ◽  
Molecular Clouds ◽  
Milky Way ◽  
Galactic Center ◽  
Large Array ◽  
Massive Black Hole ◽  
Very Large Array ◽  
Central Gravitational Field

The previous two talks in this session have shown the importance of the nucleus of the Milky Way as the host to a possible massive black hole. SgrA* is apparently surrounded by a circumnuclear ring first seen in the HCN J = l-0 emission (Gusten et al. 1987). Infall from the circumnuclear ring could explain the ionized streamers which appear to orbit SgrA* (Lo and Claussen 1983; Serabyn and Lacy 1985). Recent studies in the NH3 emission using the Nobeyama Millimeter Array (Okumura et al. 1989; 1991) and the Very Large Array (Ho et al. 1991) have suggested that a streamer may feed the Galactic center from the southern cloud M-0.13-0.08. Here we show a second streamer originating from the eastern cloud M-0.02-0.07 as well. In both cases, interactions between the molecular clouds and supernovae seem to be important, and can be seen in position-velocity diagrams. This may be the mechanism by which gas is pushed toward the central gravitational field.

scholarly journals Masers as probes of massive star formation in the nuclear disk

2007 ◽  
Vol 3 (S242) ◽  
pp. 366-373 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
R. G. Arendt ◽  
C. O. Heinke ◽  
J. L. Hinz ◽  
J. W. Hewitt ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Massive Star ◽  
Cosmic Ray ◽  
Gas Temperature ◽  
Massive Star Formation ◽  
The Galaxy ◽  
Methanol Masers ◽  
Low Efficiency

AbstractOH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared “green sources”. These highly embedded YSOs show enhanced 4.5μm emission due to excited molecular lines.The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature.

scholarly journals NH3 Observations of the Sgr A Complex Region with the Nobeyama Millimeter Array

1989 ◽  
Vol 136 ◽  
pp. 371-377 ◽  
Author(s):  
S. K. Okumura ◽  
M. Ishiguro ◽  
E. B. Fomalont ◽  
Y. Chikada ◽  
T. Kasuga ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Complex Region ◽  
Physical Conditions ◽  
Center Region ◽  
Sgr A ◽  
The Continuum

We report NH3 observations of the Sgr A complex region including Sgr A West and the 20 km/s and 50 km/s molecular clouds (M–0.13–0.08 and M–0.02–0.07) using the Nobeyama Millimeter Array and the 45m telescope. NH3(1,1) and (2,2) lines were simultaneously observed to estimate the kinetic temperature. Our results suggest strong interaction between the molecular clouds and the continuum sources in the Sgr A complex. The interaction with continuum sources might be an important factor in determining the physical conditions of molecular gas in the galactic center region.

scholarly journals X-RAY DIAGNOSTICS OF GIANT MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION AND PAST ACTIVITY OF Sgr A*

2011 ◽  
Vol 740 (2) ◽  
pp. 103 ◽  
Author(s):  
Hirokazu Odaka ◽  
Felix Aharonian ◽  
Shin Watanabe ◽  
Yasuyuki Tanaka ◽  
Dmitry Khangulyan ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
Center Region ◽  
Sgr A ◽  
Past Activity

Supernova Remnants: An Introductory Review

2004 ◽  
Vol 218 ◽  
pp. 57-64
Author(s):  
Jacco Vink
Keyword(s):  
Cosmic Rays ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Cosmic Ray ◽  
Recent Advances ◽  
Cosmic Ray Acceleration ◽  
Introductory Review

The two main aspects of supernova remnant research addressed in this review are: I. What is our understanding of the progenitors of the observed remnants, and what have we learned from these remnants about supernova nucleosynthesis? II. Supernova remnants are probably the major source of cosmic rays. What are the recent advances in the observational aspects of cosmic ray acceleration in supernova remnants?

scholarly journals OH main line masers in the M 82 starburst

2007 ◽  
Vol 3 (S242) ◽  
pp. 427-431
Author(s):  
M. K. Argo ◽  
A. Pedlar ◽  
T. W. B. Muxlow ◽  
R. J. Beswick
Keyword(s):  
Central Region ◽  
Supernova Remnants ◽  
Main Line ◽  
Line Of Sight ◽  
Starburst Galaxy ◽  
Large Array ◽  
Satellite Line ◽  
Very Large Array

AbstractA study of the distribution of OH gas in the central region of the nearby active starburst galaxy M82 has confirmed two previously known bright masers and revealed several new main line masers. Three of these are seen only at 1665 MHz, one is detected only at 1667 MHz, while the rest are detected in both lines. Observations covering both the 1665 and 1667 MHz lines, conducted with both the Very Large Array (VLA) and the Multi-Element Radio Linked Interferometer Network (MERLIN), have been used to accurately measure the positions and velocities of these features. This has allowed a comparison with catalogued continuum features in the starburst such as HII regions and supernova remnants, as well as known water and satellite line OH masers. Most of the main line masers appear to be associated with known HII regions although the two detected only at 1665 MHz are seen along the same line of sight as known supernova remnants.

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.

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