The Bok Globule BHR 160: structure and star formation
  BHR 160 is a virtually unstudied cometary globule within the Sco OB4
association in Scorpius at a distance of 1600pc. It is part of a system of
cometary clouds which face the luminous O star HD155806. BHR 160 is special
because it has an intense bright rim. We attempt to derive physical parameters
for BHR 160 and to understand its structure and the origin of its peculiar
bright rim. BHR 160 was mapped in the $^{12}$CO, $^{13}$CO and C$^{18}$O (2-1)
and (1-0) and CS (3-2) and (2-1) lines. These data, augmented with stellar
photometry derived from the ESO VVV survey, were used to derive the mass and
distribution of molecular material in BHR 160 and its surroundings. Archival
mid-infrared data from the WISE satellite was used to find IR excess stars in
the globule and its neighbourhood. An elongated 1' by 0.6' core lies adjacent
to the globule bright rim. $^{12}$CO emission covers the whole globule, but the
$^{13}$CO, C$^{18}$O and CS emission is more concentrated to the core. The
$^{12}$CO line profiles indicate the presence of outflowing material near the
core, but the spatial resolution of the mm data is not sufficient for a
detailed spatial analysis. The BHR 160 mass estimated from the C$^{18}$O
mapping is 100$\pm$50Msun(d/1.6kpc)$^2$ where d is the distance to the globule.
Approximately 70 percent of the mass lies in the dense core. The total mass of
molecular gas in the direction of BHR 160 is 210$\pm$(d/1.6kpc)$^2$ Msun when
estimated from the more extended VVV NIR photometry. We argue that the bright
rim of BHR 160 is produced by a close-by early B-type star, HD 319648, that was
likely recently born in the globule. This star is likely to have triggered the
formation of a source, IRS 1, that is embedded within the core of the globule
and detected only in Ks and by WISE and IRAS.
