Astrophysics, abstract
astro-ph/0605031

From: Miguel Angel Requena-Torres [view email]

Date: Mon, 1 May 2006 19:22:31 GMT (379kb)

Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores

Authors: M. A. Requena-Torres (1), J. Martín-Pintado (1), A. Rodríguez-Franco (1), S. Martín (2), N. J. Rodríguez-Fernández (3), P. de Vicente (4) ((1) Departamento de Astrofísica Molecular e Infrarroja-IEM-CSIC, Spain, (2) Instituto de Radioastronomía Milimétrica, Spain, (3) Observatoire de Bordeaux, france, (4) Observatorio Astronómico Nacional, Spain)

Comments: 21 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx, natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. To be publish in A&A 2006, in press

To study the origin of the large abundances of complex organic molecules in the Galactic center (GC), we have carried out a systematic study of the complex organic molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO and CS toward 40 GC molecular clouds. Using the LTE approximation, we have derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The CH3OH abundance between clouds varies by nearly two orders of magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex organic molecules relative to that of CH3OH is basically independent of the CH3OH abundance, with variations of only a factor of 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH3OH in hot cores are similar to that found in the GC clouds. However, hot corinos show different abundance ratios than the observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kind of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.

http://arxiv.org/abs/astro-ph/0605031