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Chemical features i...
Chemical features in the circumnuclear disk of the Galactic center
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- Harada, N. (author)
- Academia Sinica Taiwan,Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Riquelme, D. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Viti, S. (author)
- University College London (UCL)
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- Jimenez-Serra, I. (author)
- European Southern Observatory (ESO),University College London (UCL)
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- Requena-Torres, M. A. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Menten, K. M. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Martin, S. (author)
- Institut de Radioastronomie Millimétrique (IRAM),European Southern Observatory Santiago
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- Aladro, Rebeca, 1979 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Martin-Pintado, J. (author)
- Centro de Astrobiologia (CAB)
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- Hochgurtel, S. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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Academia Sinica Taiwan Max Planck Gesellschaft zur Förderung der Wissenschaften eV. (MPG) (creator_code:org_t)
- 2015-11-27
- 2015
- English.
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 584
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Abstract
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- Aims. The circumnuclear disk (CND) of the Galactic center is exposed to many energetic phenomena coming from the supermassive black hole Sgr A* and from stellar activities. These energetic activities can affect the chemical composition in the CND through interaction with UV photons, cosmic rays, X-rays, and shock waves. We aim to constrain the physical conditions present in the CND through chemical modeling of observed molecular species detected toward it. Methods. We analyzed a selected set of molecular line data taken toward a position in the southwest lobe of the CND with the IRAM 30m and APEX 12-m telescopes and derived the column density of each molecule via a large velocity gradient (LVG) analysis. The determined chemical composition is compared with a time-dependent, gas-grain chemical model based on the UCL_CHEM code, which includes the effects of shock waves with varying physical parameters. Results. We detect molecules, such as CO, HCN, HCO+, HNC, CS, SO, SiO, NO, CN, H2CO, HC3N, N2H+, and H3O+, and obtain their column densities. Total hydrogen densities obtained from LVG analysis range between 2x10(4) and 1x10(6) cm(-3) and most species indicate values around several x10(5) cm(-3). These values are lower than those corresponding to the Roche limit, which shows that the CND is tidally unstable. The chemical models show good agreement with the observations in cases where the density is similar to 10(4) cm(-3), the cosmic-ray ionization rate is high, > 10(-15) s(-1), or shocks with velocities > 40 km s(-)1 have occurred. Conclusions. Comparison of models and observations favors a scenario where the cosmic-ray ionization rate in the CND is high, but precise effects of other factors, such as shocks, density structures, UV photons, and X-rays from the Sgr A*, must be examined with higher spatial resolution data.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Keyword
- ISM: molecules
- Galaxy: center
Publication and Content Type
- art (subject category)
- ref (subject category)
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Harada, N.
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Riquelme, D.
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Viti, S.
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Jimenez-Serra, I ...
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Requena-Torres, ...
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Menten, K. M.
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show more...
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Martin, S.
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Aladro, Rebeca, ...
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Martin-Pintado, ...
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Hochgurtel, S.
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Physical Science ...
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and Astronomy Astrop ...
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Chalmers University of Technology