The line-of-sight distribution of the gas in the inner 60 pc of the Galaxy

Abstract

2MASS K_S band data of the inner 60 pc of the Galaxy are used to reconstruct the line-of-sight distances of the giant molecular clouds located in this region. Using the 2MASS H band image of the same region, two different populations of point sources are identified according to their flux ratio in the two bands. The population of blue point sources forms a homogeneous foreground that has to be subtracted before analyzing the K_S band image. The reconstruction is made using two basic assumptions: (i) an axis-symmetric stellar distribution in the region of interest and (ii) optically thick clouds with an area filling factor of ~1 that block all light of stars located behind them. Due to the reconstruction method, the relative distance between the different cloud complexes is a robust result, whereas it is not excluded that the absolute distance with respect to Sgr A* of structures located more than 10 pc in front of Sgr A* are understimated by up to a factor of 2. It is shown that all structures observed in the 1.2 mm continuum and in the CS(2-1) line are present in absorption. We place the 50 km s^-1 cloud complex close to, but in front of, Sgr A*. The 20 km s^-1 cloud complex is located in front of the 50 km s^-1 cloud complex and has a large LOS distance gradient along the direction of the galactic longitude. The bulk of the Circumnuclear Disk is not seen in absorption. This leads to an upper limit of the cloud sizes within the Circumnuclear Disk of ~0.06 pc.

arXiv comment12 pages with 17 figures. Accepted for publication in A&A

References in corpus (5)

• The Nuclear Bulge of the Galaxy. III. Large-Scale Physical Characteristics of Stars and Interstellar Matter
• The Dynamics of Molecular Material Within 15 pcs of the Galactic Center
• Molecular Tracers of the Central 12 pc of the Galactic Center
• Infalling Gas Towards the Galactic Center
• The stability of the Circumnuclear Disk clouds in the Galactic Centre

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• Discovery of a superluminal Fe K echo at the Galactic Center: The glorious past of Sgr A* preserved by molecular clouds
• The Nuclear Cluster of the Milky Way: Total Mass and Luminosity (long version)
• Characteristics of Diffuse X-Ray Line Emission within 20 pc of the Galactic Center
• Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk
• X-ray Scattering Halos from the Galactic Center: Implications for Diffuse Emission Around SgrA*
• A common origin for the circumnuclear disc and the nearby molecular clouds in the Galactic Centre
• Massive perturbers in the galactic center
• From the Circumnuclear Disk in the Galactic Center to thick, obscuring tori of AGNs -- Modelling the molecular emission of a parsec-scale torus as found in NGC1068