The strange mid-infrared spectrum of M 31: ISOCAM observations

Details The strange mid-infrared spectrum of M 31: ISOCAM observations The strange mid-infrared spectrum of M 31: ISOCAM observations

Sep 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998a%26a...337l..35c&link_type=abstract

Astronomy and Astrophysics, v.337, p.L35-L38 (1998)

Astronomy and Astrophysics

Astrophysics

21

Galaxies: M 31, Galaxies: Ism, Dust, Extinction, Infrared: Ism: Lines And Bands, Infrared: Stars, Stars: Carbon

Scientific paper

We present observations of the mid-IR spectrum of 4 small regions of M 31. The spectrum of the central 3\arcmin is characterized by a strong, broad unidentified emission band (UIB) at 11.3 mu m while the other usual UIBs at 6.2, 7.7 and 8.6 mu m are absent or very faint. We present a map of this area in the 11.3 mu m band and compare it with optical and H I images. The spectra of two other regions are similar; one of these regions is in the bulge, and the other one in a quiet region of the star-forming ring at 10 kpc radius. The spectrum of a more active region of this ring shows relatively stronger 6.2, 7.7 and 8.6 mu m bands. The profile of the 11.3 mu m band varies from field to field. We suggest that we see in M 31 the emission of hydrogenated amorphous carbon particles as synthetized in the atmospheres of carbon stars. These particles have mid-infrared emission or absorption bands at 3.3-3.4 mu m and 11.3 mu m only. They have to be graphitized by UV radiation to be able to emit the other UIBs. This can take place in planetary nebulae, but most particles escape this processing, and are only affected by the interstellar UV field. The interstellar radiation field in M 31 is exceptionally poor in UV, e.g. compared to that in the solar neighbourhood. It is insufficient to graphitize the particles, hence the faintness of the 6.2, 7.7 and 8.6 mu m UIBs. Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Affiliated with

Also associated with

No associations

Rating

The strange mid-infrared spectrum of M 31: ISOCAM observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The strange mid-infrared spectrum of M 31: ISOCAM observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The strange mid-infrared spectrum of M 31: ISOCAM observations will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-810290