Modeling the spectral energy distribution of galaxies. II. Disk opacity and star formation in 5 edge-on spirals

TL;DR

This study models the spectral energy distributions of five edge-on spiral galaxies to understand the roles of stellar populations in dust heating and star formation rates, confirming the dominance of young stars in these processes.

Contribution

It extends previous modeling to four additional galaxies, quantifies the contribution of stellar populations to dust heating, and derives star formation rates consistent with other observational methods.

Findings

Young stellar populations dominate dust heating in all studied galaxies.

Star formation rates are consistent with those derived from H_alpha observations.

NGC 891's star formation surface density is typical among similar galaxies.

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 7e-4 - 2e-2 M_sun * yr^-1 * kpc^-2. This is consistent with normalized SFRs derived for face-on galaxies of comparable surface gas densities from H_alpha 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.