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 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 Hot stars in the Galactic Center

1999 ◽  
Vol 193 ◽  
pp. 449-458
Author(s):  
Andreas Eckart ◽  
Thomas Ott ◽  
Reinhard Genzel ◽  
Dieter Lutz
Keyword(s):  
Black Hole ◽  
Near Infrared ◽  
Milky Way ◽  
Infrared Imaging ◽  
Galactic Center ◽  
Hot Stars ◽  
Massive Black Hole ◽  
Central Cluster ◽  
Short Period ◽  
Sgr A

The central parsec of our Galaxy is powered by a cluster of young massive hot stars which formed a few million years ago. Within that cluster the seven most luminous (L >105.75 L⊙) and moderately hot (T < 104.5 K) blue supergiants contribute half of the ionizing luminosity of that region. These stars probably formed when a dense cloud fell into the center < 107 years ago, was highly compressed there, and became gravitationally unstable. Over six years of high spatial resolution, near-infrared imaging and spectroscopy have made it possible to carry out a detailed investigation of the stars in the central cluster and its enclosed mass. As one result of a detailed variability study of the central cluster stars we found that the bright He I star IRS 16SW is a short-period variable with a period of ∼9.72 days. It is most likely an eclipsing binary with a lower mass limit of 100 solar masses. Line of sight velocities and proper motions have been measured for these hot stars (as well as ∼200 other stars) down to separations of less than five light days from the compact radio source Sgr A* at the dynamic center of the Milky Way. These confirmed measurements imply the presence of a central dark mass of 2.6 × 106 solar masses. The dark mass at the center of the Milky Way is currently the most compelling case for a massive black hole. Simple physical considerations show that this dark mass cannot consist of a stable cluster of stars, stellar remnants, substellar condensations or a degenerate gas of elementary particles but that at least 103 to 105 solar masses must be in the form of a massive black hole associated with Sgr A* itself.

scholarly journals MONITORING STELLAR ORBITS AROUND THE MASSIVE BLACK HOLE IN THE GALACTIC CENTER

2009 ◽  
Vol 692 (2) ◽  
pp. 1075-1109 ◽  
Author(s):  
S. Gillessen ◽  
F. Eisenhauer ◽  
S. Trippe ◽  
T. Alexander ◽  
R. Genzel ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Massive Black Hole ◽  
Stellar Orbits

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 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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