The First Hi-GAL Observations of the Outer Galaxy: A Look at Star Formation in the Third Galactic Quadrant in the Longitude Range 216.°5 <~ l <~ 225.°5
Publication date: 21 July 2013
Authors: D. Elia et al.
Journal: Astrophysical Journal
Volume: 772
Issue: 1
Page: 45
Year: 2013
Copyright: The American Astronomical Society
We present the first Herschel PACS and SPIRE photometric observations in a portion of the outer Galaxy (216.°5 <~ l <~ 225.°5 and -2° <~ b <~ 0°) as a part of the Hi-GAL survey. The maps between 70 and 500 um, the derived column density and temperature maps, and the compact source catalog are presented. NANTEN CO(1-0) line observations are used to derive cloud kinematics and distances so that we can estimate distance-dependent physical parameters of the compact sources (cores and clumps) having a reliable spectral energy distribution that we separate into 255 proto-stellar and 688 starless sources. Both typologies are found in association with all the distance components observed in the field, up to ~5.8 kpc, testifying to the presence of star formation beyond the Perseus arm at these longitudes. Selecting the starless gravitationally bound sources, we identify 590 pre-stellar candidates. Several sources of both proto- and pre-stellar nature are found to exceed the minimum requirement for being compatible with 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 N(log M) ∝ 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 sources 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 yet started.
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