Speaker
Description
Dust in the ISM plays a crucial role in various astrophysical processes: it acts as a coolant in star-forming regions, facilitates molecular hydrogen formation, and influences star formation. Additionally, dust traces ISM content and chemical evolution of galaxies. We have recently discovered that dust properties vary significantly within galaxies, exhibiting radial gradients, highlighting the need for refined models to interpret extragalactic observations.
I will present the first results from the DOWSING survey, which obtains deep sub‑mm observations at 450 and 850 µm for 21 nearby galaxies. These observations offer two significant advantages: first, they provide approximately five times better spatial resolution compared to Herschel (7" at 450 µm versus 36" with SPIRE at 500 µm); second, the longer wavelengths help constrain the dust emissivity index more accurately. My analysis focuses on M81, a well-studied spiral galaxy with extensive archival data. By combining the new DOWSING observations with Herschel data, I investigate M81’s dust properties using both standard SED fitting and PPMAP, a probabilistic method that works on raw maps to preserve full spatial detail.
We find that the dust-emissivity index varies from 1.8 to 2.6, with temperatures between 15 and 30 K. We also detect differences between arm and inter-arm regions, indicating that environmental factors significantly influence dust properties. Additionally, dust is known to extend into galaxies’ outer regions, potentially residing in tidal debris. We also investigate the possible cold clumps in the outskirts of M81, extending to 1.2$\times$D$_\text{25}$, using our 850 µm observations.
