Dust heating sources in galaxies: the case of M33 (HERM33ES)

TL;DR

This study uses Herschel and Spitzer data to analyze dust heating sources in the galaxy M33, revealing how different stellar populations influence warm and cold dust temperatures at high spatial resolution.

Contribution

It provides new, inclination-corrected estimators for infrared brightness and star formation rate using combined Spitzer and Herschel data.

Findings

Warm dust temperature is dominated by young stars at high brightness.

Cold dust temperature is primarily driven by evolved stellar populations.

Dust heating mechanisms vary with brightness and dust temperature.

Abstract

Dust emission is one of the main windows to the physics of galaxies and to star formation as the radiation from young, hot stars is absorbed by the dust and reemitted at longer wavelengths. The recently launched Herschel satellite now provides a view of dust emission in the far-infrared at an unequaled resolution and quality up to 500 \mu m. In the context of the Herschel HERM33ES open time key project, we are studying the moderately inclined Scd local group galaxy M33 which is located only 840 kpc away. In this article, using Spitzer and Herschel data ranging from 3.6 \mu m to 500 \mu m, along with HI, H\alpha\ maps, and GALEX ultraviolet data we have studied the emission of the dust at the high spatial resolution of 150 pc. Combining Spitzer and Herschel bands, we have provided new, inclination corrected, resolved estimators of the total infrared brightness and of the star formation rate from any combination of these bands. The study of the colors of the warm and cold dust populations shows that the temperature of the former is, at high brightness, dictated by young massive stars but, at lower brightness, heating is taken over by the evolved populations. Conversely, the temperature of the cold dust is tightly driven by the evolved stellar populations.