Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation

E. Kankare (1) , M. Hanski (1) , Gilles Theureau (2, 3) , Pekka Teerikorpi

1 University of Turku
2 LPCE - Laboratoire de physique et chimie de l'environnement
3 GEPI - Galaxies, Etoiles, Physique, Instrumentation

Aims. We attempt to determine the optical depth of spiral galaxy disks by a statistical study of new Tully-Fisher data from the ongoing KLUN+survey, and to clarify the difference between the true and apparent behavior of optical depth. Methods. By utilizing so-called normalized distances, a subsample of the data is identified to be as free from selection effects as possible. For these galaxies, a set of apparent quantities are calculated for face-on positions using the Tully-Fisher diameter and magnitude relations. These values are compared with direct observations to determine the mean value of the parameter C describing the optical depth. Results. The present study suggests that spiral galaxy disks are relatively optically thin tau(B) approximate to 0.1, at least in the outermost regions, while they appear in general to be optically thick tau(B) > 1 when the apparent magnitude and average surface brightness are studied statistically.

Mots clés: galaxies: spiral; galaxies: photometry; galaxies: ISM; galaxies: fundamental parameters

Domaines: Planète et Univers [physics]

E. Kankare, M. Hanski, Gilles Theureau, Pekka Teerikorpi. Revisiting the optical depth of spiral galaxies using the Tully-Fisher B relation. Astronomy and Astrophysics - A&A, 2009, 493 (1), pp.23-31. ⟨10.1051/0004-6361:200809892⟩. ⟨insu-02519537⟩