Stellar Systems Group

Maíz Apellániz, J.
Memorie della Societa Astronomica Italiana, v.86, p.553 (2015).
12/2015

ABSTRACT

I present results on the interstellar medium towards the O stars observed in five optical spectroscopic surveys: GOSSS, OWN, IACOB, NoMaDS, and CAFÉ-BEANS. I have measured both the amount [E(4405-5495)] and type [R₅₄₉₅] of extinction towards several hundreds of Galactic O stars and verified that the \citet{Maizetal14a} family of extinction laws provides a significantly better fit to optical+NIR Galactic extinction than either the \citet{Cardetal89} or the \citet{Fitz99} families. R₅₄₉₅ values are concentrated between 3.0 and 3.5 but for low values of E(4405-5495) there is a significant population with larger R₅₄₉₅ associated with H II regions. I have also measured different DIBs and I have found that EW{5797}/EW{5780} is anticorrelated with R₅₄₉₅, a sign that extreme zeta clouds are characterized not only by low ionization environments (as opposed to sigma clouds) but also by having a larger fraction of small dust grains. The equivalent width of the ``Gaia DIB'' (8621 Å) is strongly correlated with E(4405-5495), as expected, and its behavior appears to be more sigma -like than zeta -like. We have also started analyzing some individual sightlines in detail.