The Displaced Dusty ISM of NGC 3077: Tidal Stripping in the M 81 Triplet

TL;DR

This study detects and analyzes extended dust emission in the tidal arm near NGC 3077, revealing that galaxy interactions can strip enriched material, including dust and gas, into the intergalactic medium, impacting galaxy evolution and enrichment processes.

Contribution

First detection of extended dust emission in NGC 3077's tidal arm, showing interaction-driven stripping of enriched ISM into the intergalactic medium.

Findings

Dust in the tidal arm is colder (~13 K) than in NGC 3077 (~31 K).

Total dust mass in the tidal arm is ~1.8 million solar masses.

Dust-to-gas ratio is consistent with Galactic metallicities.

Abstract

We present the detection of extended (~30 kpc^2) dust emission in the tidal \hi\ arm near NGC 3077 (member of the M\,81 triplet) using SPIRE on board Herschel. Dust emission in the tidal arm is typically detected where the \hi\ column densities are >10^21 cm^-2. The SPIRE band ratios show that the dust in the tidal arm is significantly colder (~13 K) than in NGC 3077 itself (~31 K), consistent with the lower radiation field in the tidal arm. The total dust mass in the tidal arm is ~1.8 x 10^6 M_sun (assuming beta=2), i.e. substantially larger than the dust mass associated with NGC 3077 (~2 x 10^5 M_sun). Where dust is detected, the dust-to-gas ratio is 6+/-3 x 10^-3, consistent within the uncertainties with what is found in NGC 3077 and nearby spiral galaxies with Galactic metallicities. The faint HII regions in the tidal arm can not be responsible for the detected enriched material and are not the main source of the dust heating in the tidal arm. We conclude that the interstellar medium (atomic HI, molecules and dust) in this tidal feature was pre-enriched and stripped off NGC 3077 during its recent interaction (~3 x 10^8 yr ago) with M 82 and M 81. This implies that interaction can efficiently remove heavy elements and enriched material (dust, molecular gas) from galaxies. As interactions were more frequent at large lookback times, it is conceivable that they could substantially contribute (along with galactic outflows) to the enrichment of the intergalactic medium.