Clustered and Triggered Star Formation in W5: Observations with Spitzer

By X. Koenig, L. Allen, R. Gutermuth, J. Hora, C. Brunt, J. Muzerolle. 2008

132 citations recorded by the source corpus.

We present images and initial results from our extensive Spitzer Space Telescope imaging survey of the W5 H II region with the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). We detect dense clusters of stars, centered on the O stars HD 18326, BD +60 586, HD 17505, and HD 17520. At 24 μm, substantial extended emission is visible, presumably from heated dust grains that survive in the strongly ionizing environment of the H II region. With photometry of more than 18,000 point sources, we analyze the clustering properties of objects classified as young stars by their IR spectral energy distributions (a total of 2064 sources) across the region using a minimal-spanning-tree algorithm. We find ~40%-70% of infrared excess sources belong to clusters with ≥10 members. We find that within the evacuated cavities of the H II regions that make up W5, the ratio of Class II to Class I sources is ~7 times higher than for objects coincident with molecular gas as traced by 12CO emission and near-IR extinction maps. We attribute this contrast to an age difference between the two locations and postulate that at least two distinct generations of star formation are visible across W5. Our preliminary analysis shows that triggering is a plausible mechanism to explain the multiple generations of star formation in W5 and merits further investigation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/14cce6a53a3f412b865781352a5c02d686176842

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Citations in the corpus

ON THE STAR FORMATION EFFICIENCY OF TURBULENT MAGNETIZED CLOUDS (2012, background): “In contrast, when looking at regions of dense core and cluster formation, observers find higher SFEs (e.g., Wilking & Lada 1983; Beuther et al. 2002; Koenig et al. 2008), eventually approaching the local efficiency on scales of individual protostellar cores.”
A CORRELATION BETWEEN SURFACE DENSITIES OF YOUNG STELLAR OBJECTS AND GAS IN EIGHT NEARBY MOLECULAR CLOUDS (2011, background): “…W5 molecular cloud, where a recent generation of star formation is proceeding on the peripheries of the evacuated cavities of adjacent HII regions, Koenig et al. (2008) found star-formation efficiencies of >10-17% for high surface density clusterings and 3% for lower density distributed regions,…”
Dispersal of molecular clouds by ionizing radiation (2012, unknown): “G A ] 2 tures (Koenig et al. 2008).”
WIDE-FIELD INFRARED SURVEY EXPLORER OBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS (2012, methodology): “We also tested the results of our classification scheme by comparing the YSO catalog of Koenig et al. (2008) for the W 5 region from Spitzer with that produced by our WISE algorithm.”
The relation between the most-massive star and its parental star cluster mass (2009, unknown): “…Mayne et al. (2007); Chen et al. (2007), 35: Froebrich et al. (2008), 36: Massey et al. (1995); Vallenari et al. (1999), 37: Hasan et al. (2008), 38: Koenig et al. (2008), 39: Turner (1985); Pandey et al. (1989), 40: Hillenbrand & Hartmann (1998); Hillenbrand et al. (1998); Menten et al. (2007);…”