scholarly journals Molecular gas in the immediate vicinity of Sgr A* seen with ALMA

2016 ◽  
Vol 11 (S322) ◽  
pp. 129-132
Author(s):  
Lydia Moser ◽  
Álvaro Sánchez-Monge ◽  
Andreas Eckart ◽  
Miguel A. Requena-Torres ◽  
Macarena García-Marin ◽  
...  
Keyword(s):  
Galactic Center ◽  
Line Emission ◽  
Molecular Gas ◽  
Future Studies ◽  
X Ray ◽  
Circumnuclear Disk ◽  
Sgr A ◽  
Central Parsec ◽  
Cloud Cores ◽  
Cold Core

AbstractWe report serendipitous detections of line emission with ALMA in band 3, 6, and 7 in the central parsec of the Galactic center at an up to now highest resolution (<0.7″). Among the highlights are the very first and highly resolved images of sub-mm molecular emission of CS, H13CO+, HC3N, SiO, SO, C2H, and CH3OH in the immediate vicinity (~1″ in projection) of Sgr A* and in the circumnuclear disk (CND). The central association (CA) of molecular clouds shows three times higher CS/X (X: any other observed molecule) luminosity ratios than the CND suggesting a combination of higher excitation - by a temperature gradient and/or IR-pumping - and abundance enhancement due to UV- and/or X-ray emission. We conclude that the CA is closer to the center than the CND is and could be an infalling clump consisting of denser cloud cores embedded in diffuse gas. Moreover, we identified further regions in and outside the CND that are ideally suited for future studies in the scope of hot/cold core and extreme PDR/XDR chemistry and consequent star formation in the central few parsecs.

scholarly journals OH in the Environment of Sgr A

1989 ◽  
Vol 136 ◽  
pp. 421-422
Author(s):  
Aa. Sandqvist ◽  
R. Karlsson ◽  
J. B. Whiteoak
Keyword(s):  
Radial Velocity ◽  
Shell Structure ◽  
Spiral Structure ◽  
Angular Resolution ◽  
Galactic Center ◽  
Absorption Lines ◽  
Molecular Gas ◽  
Center Region ◽  
Circumnuclear Disk ◽  
Sgr A

The 18-cm distribution of OH in the Galactic Center region near Sgr A has been mapped in all four of the 1612, 1665, 1667 and 1720 MHz OH absorption lines using the VLA with 4 arcsec angular resolution and 9 kms-1 velocity resolution. The OH gas at +50 and +20 kms-l is seen clearly in absorption against the shell structure of Sgr A East but not against the spiral structure of Sgr A West, possibly implying that this molecular gas lies between the two continuum components - behind Sgr A West and in front of Sgr A East. Inside the Circumnuclear Disk, there is a new neutral streamer which sweeps from the disk in towards Sgr A∗ as the observed radial velocity decreases from +78 to +16 kms-1. The streamer may have a negative-velocity counterpart on the opposite side of Sgr A∗.

scholarly journals Galactic Center: Implications of Recent Chandra Observations for Spherical Accretion Models of Sgr A*

2001 ◽  
Vol 205 ◽  
pp. 32-35 ◽  
Author(s):  
Robert F. Coker ◽  
Sera Markoff
Keyword(s):  
Galactic Center ◽  
Stellar Winds ◽  
Early Type ◽  
Solar Mass ◽  
X Ray ◽  
Nonthermal Radio ◽  
Accretion Model ◽  
Early Type Stars ◽  
Sgr A ◽  
Central Parsec

At the center of the Milky Way lurks a unique compact nonthermal radio source, Sgr A*. It is thought to be powered by a 2.6 × 106 solar mass black hole that is accreting the stellar winds from the numerous early-type stars that exist in the central parsec. However, until recent high resolution Chandra observations, Sgr A* had never been unequivocably detected at wavelengths shorter than the sub-millimeter. We present a spherical accretion model which is consistent with both the flux and steep spectral shape of the X-ray emission from Sgr A*.

scholarly journals Mini-Spiral at the Galactic Center: A Link between its Structure and the Value of a Central Point Mass

1996 ◽  
Vol 169 ◽  
pp. 241-246
Author(s):  
A.M. Fridman ◽  
O.V. Khoruzhii ◽  
V.V. Lyakhovich ◽  
L. Ozernoy ◽  
L. Blitz
Keyword(s):  
Galactic Center ◽  
Density Wave ◽  
Neutral Hydrogen ◽  
Wave Model ◽  
Molecular Gas ◽  
Stellar Cluster ◽  
Nonthermal Radio ◽  
H Ii Region ◽  
Circumnuclear Disk ◽  
Sgr A

The innermost 2 pc contain a rotating ring (“circumnuclear disk”) of molecular gas, neutral hydrogen, and dust with an embedded H II region called Sgr A West; a dense stellar cluster; and a compact nonthermal radio source Sgr A∗ (for a recent review, see Blitz et al. 1993). The clumped, spiral-shaped morphology of Sgr A West, sometimes called lthe mini-spiral”, has been a subject of numerous speculations concerning its origin (for a review, see Genzel & Townes 1987). Lacy et al. (1991) demonstrated that both the kinematics and shape of a part of Sgr A West can be fairly well approximated using an one-armed density-wave model.

scholarly journals FIR Spectroscopy of the Galactic Center: Hot and Warm Molecular Gas

2016 ◽  
Vol 11 (S322) ◽  
pp. 168-169
Author(s):  
Javier R. Goicoechea ◽  
Mireya Etxaluze ◽  
José Cernicharo ◽  
Maryvonne Gerin ◽  
Jerome Pety ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Galactic Center ◽  
Rotational Line ◽  
Molecular Gas ◽  
Central Cavity ◽  
Stellar Cluster ◽  
Line Intensities ◽  
The Galaxy ◽  
Circumnuclear Disk ◽  
Sgr A

AbstractThe angular resolution (~10″) achieved by the Herschel Space Observatory ~3.5 m telescope at FIR wavelengths allowed us to roughly separate the emission toward the inner parsec of the galaxy (the central cavity) from that of the surrounding circumnuclear disk (the CND). The FIR spectrum toward Sgr A* is dominated by intense [O iii], [O i], [C ii], [N iii], [N ii], and [C i] fine-structure lines (in decreasing order of luminosity) arising in gas irradiated by the strong UV field from the central stellar cluster. The high-J CO rotational line intensities observed at the interface between the inner CND and the central cavity are consistent with a hot isothermal component at Tk ≈ 103.1 K and n(H2)≈ 104 cm−3. They are also consistent with a distribution of lower temperatures at higher gas density, with most CO at Tk≈300 K. The hot CO component (either the bulk of the CO column density or just a small fraction depending on the above scenario) likely results from a combination of UV and shock-driven heating. If UV-irradiated and heated dense clumps do not exist, shocks likely dominate the heating of the hot molecular gas component. Although this component is beam diluted in our FIR observations, it may be resolved at much higher angular resolution. An ALMA project using different molecular tracers to characterize UV-irradiated shocks in the innermost layers of the CND is ongoing.

scholarly journals Mid-Infrared (4.8–12.4 and 20.0 μm) Imaging of the Galactic Center: Modeling the Dust Emission and Energetics of the Central Parsec

1996 ◽  
Vol 169 ◽  
pp. 231-240 ◽  
Author(s):  
Dan Gezari ◽  
Eli Dwek ◽  
Frank Varosi
Keyword(s):  
Galactic Center ◽  
Dust Emission ◽  
Infrared Emission ◽  
Mid Infrared ◽  
New Model ◽  
Central Engine ◽  
Direct Indication ◽  
Sgr A ◽  
Central Parsec ◽  
Array Camera

We have modeled the mid-infrared emission from the Galactic Center using our array camera images at eight wavelengths. The results suggest that the high infrared luminosity of the region is provided by a cluster of luminous stars. There is no direct indication in the new model results of a very luminous object or “central engine” near Sgr A∗.

scholarly journals Detailed distributions of the CO J = (2 − 1)/J = (1 − 0) intensity ratios toward a large area of the central molecular zone

2013 ◽  
Vol 9 (S303) ◽  
pp. 106-108
Author(s):  
Kazufumi Torii ◽  
Rei Enokiya ◽  
Yasuo Fukui ◽  
Hiroaki Yamamoto ◽  
Akiko Kawamura ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Galactic Center ◽  
Galactic Plane ◽  
Area Coverage ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Large Area ◽  
First Results ◽  
Intensity Ratios ◽  
Sgr A

AbstractWe present the first results of the new CO J = (2 − 1) observations toward the central molecular zone (CMZ) using the NANTEN2 telescope at an angular resolution of 100″. Large area coverage of 4° × 2° in l and b and a high angular resolution of 100″ enable us to investigate detailed structures of the molecular gas in the CMZ including peculiar molecular filaments perpendicularly to the Galactic plane to b > |0.5°|. The major components of the CMZ, e.g., Sgr A, Sgr B and Sgr C cloud complexes, show high CO J = (2 − 1)/J = (1 − 0) ratios around 0.9, indicating highly excited conditions of the molecular gas, while the local foreground components show less than 0.4. The molecular filaments show the typical ratios of 0.6–0.7 indicate that they are indeed located in the Galactic center.

scholarly journals A Survey of Radio Recombination Line Emission From the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 159-166 ◽  
Author(s):  
K. R. Anantharamaiah ◽  
Farhad Yusef-Zadeh
Keyword(s):  
Galactic Center ◽  
Line Emission ◽  
Radio Continuum ◽  
Strong Line ◽  
Line Profiles ◽  
Ionized Gas ◽  
Center Region ◽  
Radio Recombination Line ◽  
Nonthermal Emission ◽  
Sgr A

Preliminary results of a systematic survey of H78α, H91α and H98β emission from the inner 40′ of the Galactic center region are presented. This region consists of two prominent continuum features, the Sgr A complex and the radio continuum Arc. In spite of much nonthermal emission arising from these two features, we detected strong line emission with large line widths in more than half of the observed 130 positions. Many of the detections are new, in particular −50 km s−1 ionized gas linking the Sgr A complex and the Arc, β line emission from GO.1+0.08 (the arched filaments), and α line emission from the loop-like structures which surround the non-thermal filaments near G0.2−0.05. We find that much of the detected lines are probably associated with the −50 km s−1 and the 20 km s−1 molecular clouds, known to lie near the Galactic center. We present line profiles of a number of Galactic center sources including Sgr B1, Sgr C and Sgr D.

scholarly journals Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

2017 ◽  
Vol 847 (1) ◽  
pp. 3 ◽  
Author(s):  
Pei-Ying Hsieh ◽  
Patrick M. Koch ◽  
Paul T. P. Ho ◽  
Woong-Tae Kim ◽  
Ya-Wen Tang ◽  
...  
Keyword(s):  
Galactic Center ◽  
Molecular Gas ◽  
Circumnuclear Disk

The Sgr B2 X‐Ray Echo of the Galactic Center Supernova Explosion that Produced Sgr A East

2006 ◽  
Vol 638 (2) ◽  
pp. 786-796 ◽  
Author(s):  
Christopher L. Fryer ◽  
Gabriel Rockefeller ◽  
Aimee Hungerford ◽  
Fulvio Melia
Keyword(s):  
Galactic Center ◽  
Supernova Explosion ◽  
X Ray ◽  
Sgr A

scholarly journals A new MIR bow shock source in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 150-152 ◽  
Author(s):  
N. Sabha ◽  
M. Zamaninasab ◽  
A. Eckart ◽  
L. Moser
Keyword(s):  
Black Hole ◽  
Symmetry Axis ◽  
Galactic Center ◽  
Bow Shock ◽  
Shock Source ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Sgr A ◽  
Central Parsec

AbstractWe find a convex-like feature at a distance of 0.68 pc (17″) from the position of the supermassive black hole, Sgr A*, at the center of the nuclear stellar cluster. This feature resembles a stellar bow shock with a symmetry axis pointing to the center. We discuss the possible nature of the feature and the implications of its alignment with other dusty comet-like objects inside the central parsec.

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