WIDE-FIELD INFRARED SURVEY EXPLOREROBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS

Abstract

We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1-3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.

Discovering protostars and their host clusters via WISE

“…A detailed characterization of individual YSOs (SED modelling, Robitaille et al 2007) and protoclusters shall await additional observations (e.g., ALMA), and will be pursued elsewhere. Ultimately, the results will bolster the statistics linked to supporting new theories of star-formation (e.g., the 'fireworks hypothesis', Koenig et al 2012), and constraining parameters such as the star formation rate and local starburst history (e.g., Bonatto & Bica 2011 A JHK s color-color diagram ( Fig. 1) is compiled for the YSO candidates highlighted by Doppmann et al (2005), Robitaille et al (2008), Gutermuth et al (2010), Straižys & Kazlauskas (2010), Majaess et al (2012), andRosvick et al (2012, in prep) 3 .…”

“…3 (e.g., ℓ, b ∼ 19, 2 • ). A subsample of the embedded clusters identified, with an emphasis on smaller overlooked subclusters (see also Koenig et al 2012), are highlighted in Table 1 and Fig. 2.…”

“…The bulk of the targets deviate from spherical symmetry and are typically associated with larger complexes (hierarchical clustering). Constituent stars are observed to emerge from dusty filamentary structure and at the periphery of bubbles (see also Koenig et al 2012). The objects were identified while visually inspecting the distribution of YSO candidates (Fig.…”

“…2, 3, see also Liu et al 2011;Rebull et al 2011;Koenig et al 2012). However, significant work remains and subsequent refinement to the selection scheme ( §2.1) pending the identification of biases is inevitable, especially given the relative youth of the published WISE data.…”

The Young Stellar Population of Lynds 1340. An Infrared View

“…We included these associations in the analysis, taking into account that, owing to the different angular resolutions, a few 2MASS/ WISE sources are associated with more than one IRAC source. Furthermore, we searched the AllWISE Source Catalog (Wright et al 2010) for YSOs, using the color and flux criteria established by Koenig et al (2012) and Koenig & Leisawitz (2014). We identified eight new candidate YSOs, seven of which are located outside of the field of view of the Spitzer observations.…”