The Physical Environment of the Massive Star-Forming Region W42

Abstract

We present an analysis of multi-wavelength observations from various datasets and Galactic plane surveys to study the star formation process in the W42 complex. A bipolar appearance of W42 complex is evident due to the ionizing feedback from the O5-O6 type star in a medium that is highly inhomogeneous. The VLT/NACO adaptive-optics K and L images (resolutions ∼0. 2-0. 1) resolved this ionizing source into multiple point-like sources below ∼5000 AU scale. The position angle ∼15 • of W42 molecular cloud is consistent with the H-band starlight mean polarization angle which in turn is close to the Galactic magnetic field, suggesting the influence of Galactic field on the evolution of the W42 molecular cloud. Herschel sub-millimeter data analysis reveals three clumps located along the waist axis of the bipolar nebula, with the peak column densities of ∼3-5 × 10 22 cm −2 corresponding to visual extinctions of A V ∼32-53.5 mag. The Herschel temperature map traces a temperature gradient in W42, revealing regions of 20 K, 25 K, and 30-36 K. Herschel maps reveal embedded filaments (length ∼1-3 pc) which appear to be radially pointed to the denser clump associated with the O5-O6 star, forming a hub-filament system. 512 candidate young stellar objects (YSOs) are identified in the complex, ∼40% of which are present in clusters distributed mainly within the molecular cloud including the Herschel filaments. Our datasets suggest that the YSO clusters including the massive stars are located at the junction of the filaments, similar to those seen in Rosette Molecular Cloud.

The Molecular Cloud S242: Physical Environment and Star-formation Activities

“…In this work, Herschel temperature and column density maps are produced using the Herschel continuum images, following the methods described in Mallick et al (2015). The Herschel temperature and column density maps are obtained from a pixel-by-pixel spectral energy distribution (SED) fit with a modified blackbody to the cold dust emission at Herschel 160-500 µm (also see Dewangan et al 2015). The Herschel 70 µm data are not included in the analysis, because the 70 µm emission is dominated by the ultraviolet (UV) heated warm dust.…”

Unveiling Molecular Clouds toward Bipolar H ii Region G8.14+0.23

“…To examine the sources with infrared-excess emission, we have used the NIR colormagnitude plot (H−K/K), as adopted in Paper II. The reliable NIR HK photometric magnitudes of point-like sources in our selected target region were obtained from the UKIRT Infrared Deep Sky Survey (UKIDSS) 6 th archival data release (UKIDSSDR6plus) of the Galactic Plane Survey (GPS) and 2MASS catalog (see Paper II for more details and also Dewangan et al 2015b). In Paper II, a color condition (i.e., H−K > 2.2 mag (or A V = 35.5 mag); Indebetouw et al 2005) was selected to identify a population of sources with infrared-excess emission.…”

Evidence of Interacting Elongated Filaments in the Star-forming Site AFGL 5142

“…Using the nearest-neighbour (NN) technique (e.g., Gutermuth et al 2009) and following the procedures described in Dewangan et al (2015), the surface density map of YSOs is also computed in this paper (also see equation in Dewangan et al 2015). Figure 11d shows the surface density contours of YSOs overlaid on the Herschel column density map, indicating the presence of groups of YSOs in the northern and southern parts of the inverted Y-like structure.…”