A 3 mm Spectral Line Survey toward the Barred Spiral Galaxy NGC 3627
  We conduct spectral line survey observations in the 3 mm band toward a spiral
arm, a bar-end, and a nuclear region of the nearby barred spiral galaxy NGC
3627 with the IRAM 30 m telescope and the Nobeyama 45 m telescope. Additional
observations are performed toward the spiral arm and the bar-end in the 2 mm
band. We detect 8, 11, and 9 molecular species in the spiral arm, the bar-end,
and the nuclear region, respectively. Star-formation activities are different
among the three regions, and in particular, the nucleus of NGC 3627 is known as
a LINER/Seyfert 2 type nucleus. In spite of these physical differences, the
chemical composition shows impressive similarities among the three regions.
This result means that the characteristic chemical composition associated with
these regions is insensitive to the local physical conditions such as star
formation rate, because such local effects are smeared out by extended
quiescent molecular gas on scales of 1 kpc. Moreover, the observed chemical
compositions are also found to be similar to those of molecular clouds in our
Galaxy and the spiral arm of M51, whose elemental abundances are close to those
in NGC 3627. Therefore, this study provides us with a standard template of the
chemical composition of extended molecular clouds with the solar metalicity in
nearby galaxies.
