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