Clustering properties of far-infrared sources in Hi-Gal science demonstation phase fields

N. Billot, E. Schisano, Michele Pestalozzi, S. Molinari, A. Noriega-Crespo, J.C. Mottram, L.D. Anderson, D. Elia, G. S. Stringfellow, Mark Thompson, D. Polychroni, L. Testi

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12 Citations (Scopus)
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We use a minimum spanning tree (MST) algorithm to characterize the spatial distribution of Galactic far-IR sources and derive their clustering properties. We aim to reveal the spatial imprint of different types of star-forming processes, e. g., isolated spontaneous fragmentation of dense molecular clouds, or events of triggered star formation around H II regions, and highlight global properties of star formation in the Galaxy. We plan to exploit the entire Herschel infrared GALactic (Hi-GAL) survey of the inner Galactic plane to gather significant statistics on the clustering properties of star-forming regions and to look for possible correlations with source properties such as mass, temperature, or evolutionary stage. In this paper, we present a pilot study based on the two 2 degrees x 2 degrees fields centered at longitudes l = 30 degrees and l = 59 degrees obtained during the science demonstration phase of the Herschel mission. We find that over half of the clustered sources are associated with H II regions and infrared dark clouds. Our analysis also reveals a smooth chromatic evolution of the spatial distribution where sources detected at short wavelengths, likely protostars surrounded by warm circumstellar material emitting in the far-infrared, tend to be clustered in dense and compact groups around H II regions while sources detected at long wavelengths, presumably cold and dusty density enhancements of the ISM emitting in the submillimeter, are distributed in larger and looser groups.
Original languageEnglish
Article number28
JournalThe Astrophysical Journal
Issue number1
Publication statusPublished - 2011


  • H II regions
  • stars : formation
  • stars : protostars
  • submillimeter : ISM
  • submillimeter : stars


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