Exploring the Dust Content of Galactic Halos with Herschel. IV. NGC 3079

TL;DR

This study uses Herschel far-infrared observations to analyze dust structures and their interactions with galactic winds in the edge-on galaxy NGC 3079, revealing dust lifted by nuclear outflows and associated multi-wavelength features.

Contribution

It provides new insights into the distribution and dynamics of dust in galactic halos and the impact of nuclear outflows on dust transport.

Findings

Detection of a 25 kpc X-shaped dust structure aligned with other outflow features.

Evidence of dust being lifted out of the disk by galactic winds.

Broad [C II] and OH features indicating interaction between cool dust and nuclear outflows.

Abstract

We present the results from an analysis of deep Herschel far-infrared observations of the edge-on disk galaxy NGC 3079. The PSF-cleaned PACS images at 100 and 160 um display a 25 kpc x 25 kpc X-shape structure centered on the nucleus that is similar in extent and orientation to that seen in Halpha, X-rays, and the far-ultraviolet. One of the dusty filaments making up this structure is detected in the SPIRE 250 um map out to ~25 kpc from the nucleus. The match between the far-infrared filaments and those detected at other wavelengths suggests that the dusty material has been lifted out of the disk by the same large-scale galactic wind that has produced the other structures in this object. A closer look at the central 10 kpc x 10 kpc region provides additional support for this scenario. The dust temperatures traced by the 100-to-160 um flux ratios in this region are enhanced within a biconical region centered on the active galactic nucleus, aligned along the minor axis of the galaxy, and coincident with the well-known double-lobed cm-wave radio structure and Halpha-X-ray nuclear superbubbles. PACS imaging spectroscopy of the inner 6-kpc region reveals broad [C II] 158 um emission line profiles and OH 79 um absorption features along the minor axis of the galaxy with widths well in excess of those expected from beam smearing of the disk rotational motion. This provides compelling evidence that the cool material traced by the [C II] and OH features directly interacts with the nuclear ionized and relativistic outflows traced by the Halpha, X-ray, and radio emission.