Astronomy and Astrophysics, volume 613A, 9-9 (2018/5-1)
Optical-NIR dust extinction towards Galactic O stars.
MAIZ-APELLANIZ J. and BARBA R.H.
Abstract (from CDS):
Context. O stars are excellent tracers of the intervening ISM because of their high luminosity, blue intrinsic SED, and relatively featureless spectra. We are currently conducting the Galactic O-Star Spectroscopic Survey (GOSSS), which is generating a large sample of O stars with accurate spectral types within several kpc of the Sun. Aims. We aim to obtain a global picture of the properties of dust extinction in the solar neighborhood based on optical-NIR photometry of O stars with accurate spectral types. Methods. We have processed a carefully selected photometric set with the CHORIZOS code to measure the amount [E(4405 - 5495)] and type [R5495
] of extinction towards 562 O-type stellar systems. We have tested three different families of extinction laws and analyzed our results with the help of additional archival data. Results. The Maiz Apellaniz et al. (2014A&A...564A..63M
) family of extinction laws provides a better description of Galactic dust that either the Cardelli et al. (1989ApJ...345..245C
) or Fitzpatrick (1999PASP..111...63F
) families, so it should be preferentially used when analysing samples similar to the one in this paper. In many cases O stars and late-type stars experience similar amounts of extinction at similar distances but some O stars are located close to the molecular clouds left over from their births and have larger extinctions than the average for nearby late-type populations. In qualitative terms, O stars experience a more diverse extinction than late-type stars, as some are affected by the small-grain-size, low-R5495
effect of molecular clouds and others by the large-grain-size, high-R5495
effect of HII regions. Late-type stars experience a narrower range of grain sizes or R5495
, as their extinction is predominantly caused by the average, diffuse ISM. We propose that the reason for the existence of large-grain-size, high-R5495
regions in the ISM in the form of HII regions and hot-gas bubbles is the selective destruction of small dust grains by EUV photons and possibly by thermal sputtering by atoms or ions.
© ESO 2018
dust, extinction - Galaxy: structure - methods: data analysis - methods: observational - stars: early-type
VizieR on-line data:
<Available at CDS (J/A+A/613/A9): table1.dat>
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