scholarly journals Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk

2008 ◽  
Vol 681 (2) ◽  
pp. 1287-1295 ◽  
Author(s):  
Loránt O. Sjouwerman ◽  
Ylva M. Pihlström
Keyword(s):  
Galactic Center ◽  
Large Array ◽  
Very Large Array ◽  
Sagittarius A ◽  
Circumnuclear Disk

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 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 TRANSIENT EVENTS IN ARCHIVAL VERY LARGE ARRAY OBSERVATIONS OF THE GALACTIC CENTER

2016 ◽  
Vol 833 (1) ◽  
pp. 11 ◽  
Author(s):  
Anirudh Chiti ◽  
Shami Chatterjee ◽  
Robert Wharton ◽  
James Cordes ◽  
T. Joseph W. Lazio ◽  
...  
Keyword(s):  
Galactic Center ◽  
Large Array ◽  
Very Large Array ◽  
Transient Events

scholarly journals GBT and VLA investigation of the ionized gas towards the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 92-93 ◽  
Author(s):  
M. J. Royster ◽  
F. Yusef-Zadeh
Keyword(s):  
Galactic Center ◽  
Thermal Flux ◽  
Global Scale ◽  
Large Array ◽  
Ionized Gas ◽  
Very Large Array ◽  
Preliminary Results ◽  
Radio Recombination Lines ◽  
Green Bank Telescope

AbstractWe report results of a study of the ionized gas towards the Galactic center with radio recombination lines at cm wavelengths. Both the Green Bank Telescope and the Very Large Array were utilized to probe the kinematics of the ionized gas on a global scale for both diffuse and discrete sources within the inner 2.0° × 0.5° (l × b). A diffuse ∼0 km s−1 gas, a thermal flux continuum fraction exceeding 40%, and an asymmetry where ∼70% of the ionized gas is found at positive Galactic longitudes are the preliminary results briefly discussed here.

Spatially Resolved Very Large Array 74 MHz Observations Toward the Galactic Center

2003 ◽  
Vol 324 (S1) ◽  
pp. 17-24 ◽  
Author(s):  
C. L. Brogan ◽  
M. Nord ◽  
N. Kassim ◽  
J. Lazio ◽  
K. Anantharamaiah
Keyword(s):  
Galactic Center ◽  
Large Array ◽  
Very Large Array ◽  
Spatially Resolved

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 8.5. Radio polarimetric study of the Galactic center threads

1998 ◽  
Vol 184 ◽  
pp. 353-354
Author(s):  
Cornelia C. Lang ◽  
Mark Morris
Keyword(s):  
High Resolution ◽  
Galactic Center ◽  
Large Array ◽  
Very Large Array ◽  
Polarimetric Study ◽  
Thermal Radio

The Very Large Array (VLA) has been used to carry out a high resolution, polarimetric study of the isolated non-thermal radio filaments, G0.08+0.15, and G359.96+0.09, also known as the Northern and Southern Threads, found near the Galactic Center (GC).

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