THE PROPER MOTION OF THE GALACTIC CENTER PULSAR RELATIVE TO SAGITTARIUS 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.

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

The Astrophysical Journal ◽

10.1086/588753 ◽

2008 ◽

Vol 681 (2) ◽

pp. 1287-1295 ◽

Cited By ~ 24

Author(s):

Loránt O. Sjouwerman ◽

Ylva M. Pihlström

Keyword(s):

Galactic Center ◽

Large Array ◽

Very Large Array ◽

Sagittarius A ◽

Circumnuclear Disk

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How maser observations unravel the gas motions in the Galactic Center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317010213 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 176-179

Author(s):

K. Immer ◽

M. Reid ◽

A. Brunthaler ◽

K. Menten ◽

Q. Zhang ◽

...

Keyword(s):

Spectral Line ◽

Proper Motion ◽

Galactic Center ◽

Galactic Plane ◽

Orbital Dynamics ◽

Line Of Sight ◽

Molecular Gas ◽

Kinematic Structure ◽

3D Motion ◽

Motion Measurements

AbstractThe Central Molecular Zone (CMZ), the inner 450 pc of our Galaxy, is an exceptional region where the volume and column densities, gas temperatures, velocity dispersions, etc. are much higher than in the Galactic plane. It has been suggested that the formation of stars and clusters in this area is related to the orbital dynamics of the gas. The complex kinematic structure of the molecular gas was revealed by spectral line observations. However, these results are limited to the line-of-sight-velocities. To fully understand the motions of the gas within the CMZ, we have to know its location in 6D space (3D location + 3D motion). Recent orbital models have tried to explain the inflow of gas towards and its kinematics within this region. With parallax and proper motion measurements of masers in the CMZ we can discriminate among these models and constrain how our Galactic Center is fed with gas.

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How far actually is the Galactic Center IRS 13E3 from Sagittarius A*?

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa016 ◽

2020 ◽

Vol 72 (3) ◽

Author(s):

Masato Tsuboi ◽

Yoshimi Kitamura ◽

Takahiro Tsutsumi ◽

Ryosuke Miyawaki ◽

Makoto Miyoshi ◽

...

Keyword(s):

Galactic Center ◽

Three Dimensional ◽

Line Of Sight ◽

Recombination Line ◽

Intermediate Mass ◽

Ionized Gas ◽

Sagittarius A ◽

Projection Distance ◽

Spectroscopic Information ◽

Sgr A

Abstract The Galactic Center IRS 13E cluster is a very intriguing infrared object located at ${\sim } 0.13$ pc from Sagittarius A$^\ast$ (Sgr A$^\ast$) in projection distance. There are arguments both for and against the hypothesis that a dark mass like an intermediate mass black hole (IMBH) exists in the cluster. We recently detected the rotating ionized gas ring around IRS 13E3, which belongs to the cluster, in the H30$\alpha$ recombination line using ALMA. The enclosed mass is derived to be $M_{\mathrm{encl.}}\simeq 2\times 10^{4}\, M_\odot$, which agrees with an IMBH and is barely less than the astrometric upper limit mass of an IMBH around Sgr A$^\ast$. Because the limit mass depends on the true three-dimensional (3D) distance from Sgr A$^\ast$, it is very important to determine it observationally. However, the 3D distance is indefinite because it is hard to determine the line-of-sight (LOS) distance by usual methods. We attempt here to estimate the LOS distance from spectroscopic information. The CH$_3$OH molecule is easily destroyed by the cosmic rays around Sgr A$^{\ast }$. However, we detected a highly excited CH$_3$OH emission line in the ionized gas stream associated with IRS 13E3. This indicates that IRS 13E3 is located at $r\gtrsim 0.4$ pc from Sgr A$^{\ast }$.

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Probing Sagittarius A* accretion with ALMA

Proceedings of the International Astronomical Union ◽

10.1017/s174392131601214x ◽

2016 ◽

Vol 11 (S322) ◽

pp. 21-24

Author(s):

Elena Murchikova

Keyword(s):

Galactic Center ◽

Accretion Rate ◽

Recombination Line ◽

Ionized Gas ◽

X Ray ◽

Sagittarius A ◽

Hydrogen Recombination ◽

Unique Probe ◽

Cool Gas

AbstractThe submm Hydrogen recombination line technique can be used as a probe of the Galactic Center. We present the results of our H30α observations of ionized gas from within 0.015 pc around SgrA*. The observations were obtained on ALMA in cycle 3. The line was not detected, but we were able to set a limit on the mass of the cool gas (T~ 104 K) at 2 × 10−3M⊙. This is the unique probe of gas cooler than T ~106 K traced by X-ray emission. The total amount of gas near SgrA* gives us clues to understanding the accretion rate of SgrA*.

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