Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21711204c&link_type=abstract
American Astronomical Society, AAS Meeting #217, #112.04; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We report the first detections of diffuse interstellar bands (DIBs) in absorption towards early-type supergiant stars in the Local Group spiral galaxies M 31 and M 33. The λλ4430, 5705, 5780, 5797, 6203, 6269, 6283, 6379 and 6613 DIBs are detected at radial velocities matching the blue-shifted M 31 and M 33 Na I absorption lines. The overall spectrum of DIBs and the ratios of strengths between the different M 31 and M 33 DIBs are found to be similar to those typically observed in the Milky Way. These results are discussed in the context of the different interstellar physical and chemical conditions of these galaxies compared with the Milky Way, including the metallicity, the interstellar radiation field, the dust extinction properties and the PAH abundances. Some of the M 31 and M 33 DIB equivalent widths are found to be exceptionally large per unit reddening (E(B-V)) compared with those typically observed in the Galaxy. These results indicate that conditions in M 31 and M 33 are favourable for the production of the large organic molecules that are believed to be the carriers of at least some of the DIBs. A negative correlation is found in M 31 between the DIB strengths and the strength of the interstellar NUV radiation field, which suggests that the DIB carriers and/or their chemical precursors are destroyed by NUV radiation.
This work has been funded by the NASA Institute for Astrobiology, the Faculty of the European Space Astronomy Centre (ESAC), Queen's University Belfast, and the UK Engineering and Physical Sciences Research Council (EPSRC).
Cordiner Martin
Cox Nick L. J.
Evans John C. Jr.
Smith Keith T.
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