Temperature Variations of the Cold Dust in the Triangulum Galaxy M33

TL;DR

This study maps cold dust temperature variations across M33, revealing a radial decline and indicating non-OB stars as the main heating source for cold dust at large scales.

Contribution

It provides the first detailed 1.1 mm dust temperature map of M33, linking cold dust heating to non-OB stars rather than ionizing flux.

Findings

Dust temperature decreases from 20 K to 13 K with radius.

Cold dust correlates with Ks band brightness, not ionizing flux.

Non-OB stars are the dominant heating source for cold dust.

Abstract

We present wide-field 1.1 mm continuum imaging of the nearby spiral galaxy M 33, conducted with the AzTEC bolometer camera on ASTE. We show that the 1.1 mm flux traces the distribution of dust with T ~20 K. Combined with far-infrared imaging at 160um, we derive the dust temperature distribution out to a galactic radius of ~7 kpc with a spatial resolution of ~100 parsecs. Although the 1.1 mm flux is observed predominantly near star forming regions, we find a smooth radial temperature gradient declining from ~20 K to ~13 K, consistent with recent results from the Herschel satellite. Further comparison of individual regions show a strong correlation between the cold dust temperature and the Ks band brightness, but not with the ionizing flux. The observed results imply that the dominant heating source of cold dust at few hundred parsec scales are due to the non-OB stars, even when associated with star forming regions.