C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST02:05:50

2018A&A...616L...1G - Astronomy and Astrophysics, volume 616, L1-1 (2018/8-1)

High-velocity hot CO emission close to Sgr A*. Herschel/HIFI submillimeter spectral survey toward Sgr A*.


Abstract (from CDS):

The properties of molecular gas, the fuel that forms stars, inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter scan (∼480-1250GHz) and [CII] 158µm line observations carried out with Herschel/HIFI toward Sgr A*; these results are complemented by a ∼2'x2' 12CO (J=3-2) map taken with theIRAM 30 m telescope at ∼7'' resolution. We report the presence of high positive-velocity emission (up to about +300km/s) detected in the wings of 12CO J=5-4 to 10-9 lines. This wing component is also seen in H2O (11,0-10,1), a tracer of hot molecular gas; in [CII] 158µm, an unambiguous tracer of UV radiation; but not in [CI] 492, 806GHz. This first measurement of the high-velocity 12CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the supermassive black hole (<1pc). Observed by ALMA, this velocity range appears as a collection of 12CO (J=3-2) cloudlets lying in a very harsh environment that is pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high positive-velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer Tk~=400K-2000K for nH~=(0.2-1.0)x105cm–3. These results point toward the important role of stellar UV radiation, but we show that radiative heating alone cannot explain the excitation of this ∼10-60M component of hot molecular gas inside the central cavity.Instead, strongly irradiated shocks are promising candidates.

Abstract Copyright: © ESO 2018

Journal keyword(s): ISM: clouds - ISM: kinematics and dynamics - ISM: molecules - Galaxy: center

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 NAME Galactic Circumnuclear Disk PoG 17 45 40.0 -29 00 28           ~ 111 0
2 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3451 3
3 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11540 0

    Equat.    Gal    SGal    Ecl

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