Modeling the spectral energy distribution of galaxies

II. Disk opacity and star formation in 5 edge-on spirals

¹ University of Crete, Physics Department, PO Box 2208, 710 03 Heraklion, Crete, Greece
² Observatoire de Marseille, 2 place Le Verrier 13248 Marseille Cedex 4, France
³ Max Planck Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
⁴ The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, California 91101, USA
⁵ Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ Foundation for Research and Technology-Hellas, PO Box 1527, 711 10 Heraklion, Crete, Greece

Corresponding author: A. Misiriotis, angmis@physics.uoc.gr

Received: 27 March 2001
Accepted: 19 April 2001

Abstract

Using tools previously described and applied to the prototype galaxy NGC 891, we model the optical to far-infrared spectral energy distributions (SED) of four additional edge-on spiral galaxies, namely NGC 5907, NGC 4013, UGC 1082 and UGC 2048. Comparing the model predictions with IRAS and, where available, sub-millimeter and millimeter observations, we determine the respective roles of the old and young stellar populations in grain heating. In all cases, the young population dominates, with the contribution of the old stellar population being at most 40% , as previously found for NGC 891. After normalization to the disk area, the massive star-formation rate (SFR) derived using our SED modeling technique, which is primarily sensitive to the non-ionizing ultraviolet output from the young stellar population, lies in the range . This is consistent with normalized SFRs derived for face-on galaxies of comparable surface gas densities from H_α observations. Though the most active star-forming galaxy of the five in absolute terms, NGC 891 is not an exceptional system in terms of its surface density in SFR.