RCW36: characterizing the outcome of massive star formation

Abstract

Context. Massive stars play a dominant role in the process of clustered star formation, with their feedback into the molecular cloud through ionizing radiation, stellar winds, and outflows. The formation process of massive stars is poorly constrained because of their scarcity, the short formation timescale, and obscuration. By obtaining a census of the newly formed stellar population, the star formation history of the young cluster and the role of the massive stars within it can be unraveled. Aims. We aim to reconstruct the formation history of the young stellar population of the massive star-forming region RCW 36. We study several dozen individual objects, both photometrically and spectroscopically, looking for signs of multiple generations of young stars and investigating the role of the massive stars in this process. Methods. We obtain a census of the physical parameters and evolutionary status of the young stellar population. Using a combination of near-infrared photometry and spectroscopy we estimate the ages and masses of individual objects. We identify the population of embedded young stellar objects (YSOs) by their infrared colors and emission line spectra. Results. RCW 36 harbors a stellar population of massive and intermediate-mass stars located around the center of the cluster. Class 0/I and II sources are found throughout the cluster. The central population has a median age of 1.1 ± 0.6 Myr. Of the stars that could be classified, the most massive ones are situated in the center of the cluster. The central cluster is surrounded by filamentary cloud structures; within these, some embedded and accreting YSOs are found. Conclusions. Our age determination is consistent with the filamentary structures having been shaped by the ionizing radiation and stellar winds of the central massive stars. The formation of a new generation of stars is ongoing, as demonstrated by the presence of embedded protostellar clumps and two exposed protostellar jets.

Ionization compression impact on dense gas distribution and star formation

“…This supports the previous study in Minier et al (2013) showing that, based on the morphology of the regions, the gravitational collapse of these condensations (Fig. 10) was likely to be triggered This is also confirmed by the recent age determination of the different stellar populations done by Ellerbroek et al (2013). Furthermore, the exponent α decreases to a value of 1.54 ± 0.02 in region 1+2+3+4.…”

Candidate X-Ray-emitting OB Stars in MYStIX Massive Star-forming Regions

“…Note that Gagné et al (2011) adopted an extinction law with reddening parameter R V = 4.0 for Carina, while Kiminki et al (2015) adopted R V = 3.6 for W3; in reality the reddening parameter can vary even among different stars in the same star-forming region. Ellerbroek et al (2012), (4) e If checked, star was among the 67 selected independently by our procedure for identifying OB candidates among IR SEDs that were counterparts to MYStIX X-ray sources.…”

Massive pre-main sequence stars in M17

“…H97 reported that their strength did not vary with A V (or E(B − V)) as seen in other Galactic sightlines. Massive star forming regions are known to exhibit anomalous extinction properties (Dahlstrom et al 2013;Oka et al 2013;Ellerbroek et al 2013a). We will report the DIB behaviour towards sightlines in M17 in a separate paper.…”

“…The overall conclusion is that the extinction is quite patchy, with substantial variation on a spatial scale of 50 arcsec (corresponding to a geometrical scale of 0.5 pc at the distance of M17), similar as to the findings of H97. A dust disk local to the star, for example, may dominate the line-of-sight extinction towards the sources (see Ellerbroek et al 2013a). Studies of individual sources therefore should not rely on average properties of the region, but should be based on a detailed investigation of the extinction in the line of sight.…”

“…Once the accretion rate diminishes, the "bloated" pre-main-sequence (PMS) star contracts to the main sequence on the Kelvin-Helmholtz timescale. Recently, candidates for such bloated, massive PMS stars have been spectroscopically confirmed (Ochsendorf et al 2011;Bik et al 2012;Ellerbroek et al 2013a;Chen et al 2015).…”