The ALMA Detection of Extraplanar 13CO in a Ram-pressure-stripped Galaxy
  and Its Implication
  NGC 4522 is a Virgo spiral that is currently undergoing active ram pressure
stripping. In previous single-dish observations, 12CO emission was detected
outside of the stellar disk, some of which coincides with the extraplanar HI
gas and H$\alpha$ patches. The extraplanar gas identified in multi-wavelength
data makes this galaxy an ideal case to study the impact of pressure due to the
cluster medium on the interstellar gas of various phases. In this Letter, we
present the high-resolution 12CO(1-0) and 13CO(1-0) data of NGC 4522 obtained
using the Atacama Large Millimeter/submillimeter Array (ALMA). In particular,
we report here the extraplanar 13CO detection that has never before been seen
in ram-pressure-stripped galaxies. As the main donor of 13C in the interstellar
medium is evolved stars, the presence of 13CO strongly suggests that heavy
elements likely originated from the galactic disk, not from the newly formed
stars in situ. Even though it is still inconclusive whether it is stripped in
atomic form or as molecules, this study provides evidence for the ram pressure
stripping of heavy elements, which can chemically enrich the halo gas, and
potentially the intracluster medium, in the case that they are pushed strongly
enough to escape the galaxy.
