The visible and infrared extinction law and the gas-to-dust ratio in the Small Magellanic Cloud.
Abstract
Photometric observations in the UBVJHK bands have been made for 23 O-B3 stars in the Small Magellanic Cloud, for which the MK spectral type and luminosity class have been determined. Also derived from these data are the extinction curve in the visible and the near-infrared. This curve is very close to the curves in the Galaxy and the Large Magellanic Cloud; in particular, R = A(V)/E(B-V) = 2.7 + or - 0.2 in the SMC, only slightly smaller than the galactic value of about 3.1. Also determined is the column density N(H) of atomic hydrogen in front of most of these stars, from IUE observations of the Lyman alpha interstellar line. It is found that the SMC gas-to-dust ratio N(H)/E(B-V) is in the range 3.7 to 5.2 x 10 to the 22nd atoms/sq cm per magnitude, about 8 times the Galactic value. This is probably correlated with the large underabundance of the SMC in heavy elements. One star, Sk 143, has a gas-to-dust ratio close to the Galactic one.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1985
- Bibcode:
- 1985A&A...149..330B
- Keywords:
-
- Cosmic Dust;
- Infrared Astronomy;
- Interstellar Extinction;
- Interstellar Gas;
- Magellanic Clouds;
- Visible Spectrum;
- Gas Density;
- Hydrogen Clouds;
- Lyman Alpha Radiation;
- Near Infrared Radiation;
- Stellar Color;
- Astrophysics