Approaching hell's kitchen: Molecular daredevil clouds in the vicinity of Sgr A*

Abstract

We report serendipitous detections of line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) in band 3, 6, and 7 in the central parsec down to within 1" around Sgr A* at an up to now highest resolution (<0.5") view of the Galactic Center (GC) in the sub-millimeter (sub-mm) domain. From the 100 GHz continuum and the H39αemission we obtain a uniform electron temperature around 6000 K for the minispiral. The spectral index of Sgr A* is ~ 0.5 at 100 - 250 GHz and ~ 0.0 at 230 - 340 GHz. The bright sources in the center show spectral indices around -0.1 implying Bremsstrahlung emission, while dust emission is emerging in the minispiral exterior. Apart from CS, which is most widespread in the center, H13CO+, HC3N, SiO, SO, C2H, CH3OH, 13CS and N2H+ are also detected. The bulk of the clumpy emission regions is at positive velocities and in a region confined by the minispiral northern arm, bar and the sources IRS 3 and 7. Although partly spatially overlapping with the radio recombination line (RRL) emission at same negative velocities, the relation to the minispiral remains unclear. A likely explanation is an infalling clump consisting of denser cloud cores embedded in diffuse gas. The central association of clouds (CA) shows three times higher CS/X (X: any other observed molecule) ratios than the circumnuclear disk (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. Hence, we conclude that this CA is closer to the center than the CND is to the center. Moreover, we find molecular emission at velocities up to 200 km s-1. ...

59 pages (mainbody 26, rest: appendix), 25 figures, accepted, in press, Table B.1 revised

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Cited by in corpus (27)

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• Near- and mid-infrared observations in the inner tenth of a parsec of the Galactic center -- Detection of proper motion of a filament very close to Sgr~A*
• Rotating Ionized Gas Ring around the Galactic Center IRS13E3
• Constraining the accretion flow density profile near Sgr A* using the $L^{\prime }$-band emission of the S2 star
• The apparent tail of the Galactic center object G2/DSO
• The "Red Radio Ring": Ionised and Molecular Gas in a Starburst/Active Galactic Nucleus at $z\sim 2.55$
• High-speed molecular cloudlets around the Galactic Center supermassive black hole
• Dusty plasma in active galactic nuclei
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• The X-ray footprint of the CircumNuclear Disk
• The Nuclear Filaments inside the Circumnuclear Disk in the Central 0.5 pc of the Galactic center
• How far actually is the Galactic Center IRS 13E3 from Sagittarius A${}^{\ast }$?
• The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure
• A common origin for the circumnuclear disc and the nearby molecular clouds in the Galactic Centre
• Sub-millimeter Detection of a Galactic Center Cool Star IRS 7 by ALMA
• Candidate Young Stellar Objects in the S-cluster: The Kinematic Analysis of a Sub-population of the Low-mass G-objects close to Sgr A*
• A stellar fly-by close to the Galactic centre: Can we detect stars on highly-relativistic orbits?
• High-spectral resolution M-band observations of CO Rot-Vib absorption lines towards the Galactic center
• Discovery of a Dense Association of Stars in the Vicinity of the Supermassive Black Hole Sgr A*
• The Discovery of an Active Wind from the Milky Way's Black Hole
• Parsec-scale SiO emission in the Galactic Center