a Herschel Look to Star Formation in the Third Galactic Quadrant
Résumé
The first Hi-GAL observations of the outer Galaxy consist of five dust continuum maps, between 70 and 500 μm, of the area delimited by 216.5° < ℓ < 225.5° and -2° < b < 0°). NANTEN CO(1-0) line observations are used to derive cloud kinematics and distances, making it possible to estimate physical parameters of the compact sources (cores and clumps) detected in the region, namely 255 proto-stellar and 590 pre-stellar sources, respectively. Both source typologies are found in all the distance components observed in the field, up to - 5.8 kpc, testifying the presence of star formation beyond the Perseus arm at these longitudes. Furthermore, several sources of both protoand pre-stellar nature are compatible with requirements for massive star formation, based on the mass-radius relation. For the pre-stellar sources belonging to the Local arm (d < 1.5 kpc) we study the mass function, whose high-mass end shows a power-law behavior N(logM) ˜ M^(-1.0±0.2). Finally, we use a luminosity versus mass diagram to infer the evolutionary status of the sources, finding that most of the proto-stellar are in the early accretion phase (with some cases compatible with a Class-I stage), while for pre-stellar sources, in general, accretion has not started yet.