SPIRE imaging of M82: cool dust in the wind and tidal streams

TL;DR

This study uses Herschel SPIRE imaging to map cool dust in M82's wind and tidal streams, revealing extensive dust distribution and physical properties affected by galaxy interactions and starburst activity.

Contribution

It provides the first detailed far-infrared characterization of dust in M82's wind and halo, highlighting the impact of tidal interactions over starburst winds.

Findings

Over two thirds of extraplanar dust removed by tidal interactions

Dust emission more extended than PAH emission in the halo

Variation in dust properties with distance from galaxy center

Abstract

M82 is a unique representative of a whole class of galaxies, starbursts with superwinds, in the Very Nearby Galaxy Survey with Herschel. In addition, its interaction with the M81 group has stripped a significant portion of its interstellar medium from its disk. SPIRE maps now afford better characterization of the far-infrared emission from cool dust outside the disk, and sketch a far more complete picture of its mass distribution and energetics than previously possible. They show emission coincident in projection with the starburst wind and in a large halo, much more extended than the PAH band emission seen with Spitzer. Some complex substructures coincide with the brightest PAH filaments, and others with tidal streams seen in atomic hydrogen. We subtract the far-infrared emission of the starburst and underlying disk from the maps, and derive spatially-resolved far-infrared colors for the wind and halo. We interpret the results in terms of dust mass, dust temperature, and global physical conditions. In particular, we examine variations in the dust physical properties as a function of distance from the center and the wind polar axis, and conclude that more than two thirds of the extraplanar dust has been removed by tidal interaction, and not entrained by the starburst wind.