Title: Herschel observations of the Galactic HII region RCW 79,
Abstract: Triggered star formation around HII regions could be an important process.
The Galactic HII region RCW 79 is a prototypical object for triggered high-mass
star formation. We take advantage of Herschel data from the surveys HOBYS,
"Evolution of Interstellar Dust", and Hi-Gal to extract compact sources in this
region, complemented with archival 2MASS, Spitzer, and WISE data to determine
the physical parameters of the sources (e.g., envelope mass, dust temperature,
and luminosity) by fitting the spectral energy distribution. We obtained a
sample of 50 compact sources, 96% of which are situated in the
ionization-compressed layer of cold and dense gas that is characterized by the
column density PDF with a double-peaked lognormal distribution. The 50 sources
have sizes of 0.1-0.4 pc with a typical value of 0.2 pc, temperatures of 11-26
K, envelope masses of 6-760 $M_\odot$, densities of 0.1-44 $\times$ $10^5$
cm$^{-3}$, and luminosities of 19-12712 $L_\odot$. The sources are classified
into 16 class 0, 19 intermediate, and 15 class I objects. Their distribution
follows the evolutionary tracks in the diagram of bolometric luminosity versus
envelope mass (Lbol-Menv) well. A mass threshold of 140 $M_\odot$, determined
from the Lbol-Menv diagram, yields 12 candidate massive dense cores that may
form high-mass stars. The core formation efficiency (CFE) for the 8 massive
condensations shows an increasing trend of the CFE with density. This suggests
that the denser the condensation, the higher the fraction of its mass
transformation into dense cores, as previously observed in other high-mass
star-forming regions.