Journal Article

Infrared photometric study of the massive star-forming region S235 using <i>Spitzer</i>-Infrared Array Camera and <i>JHK</i> observations

L. K. Dewangan and B. G. Anandarao

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1526-1544
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18487.x
Infrared photometric study of the massive star-forming region S235 using Spitzer-Infrared Array Camera and JHK observations

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We present the Spitzer-Infrared Array Camera (IRAC) images of the S235 star-forming complex that includes the east 1, east 2, central, S235A and S235B regions. In addition, we present the near-infrared images of the S235A and S235B regions. The IRAC photometry reveals on-going star formation, with 86 Class 0/I and 144 Class II young stellar objects (YSOs) in the entire S235 complex. Nearly 73 per cent of these YSOs are present in clusters with a maximum surface density of 120 YSOs pc−2 (in the vicinity of S235A and S235B regions). A few YSOs, possibly in an arc-like formation, are identified towards the south of S235A region, which may be considered evidence for magnetically supercritical collapse. One of the sources in the arc-like formation, namely S235AB-MIR, seems to be a young, massive star that is still accreting matter. Spectral energy distribution (SED) modelling of some of the newly identified YSOs confirms the classification made on the basis of IRAC colours. The IRAC ratio map of Ch2/Ch4 traces clearly the Brα emission associated with the H ii region of S235A within the horseshoe envelope. Outside the horseshoe structure, the ratio map indicates shock-excited H2 emission. Brα emission is also seen around S235B (from the ratio map). The ratio map of Ch2/Ch4 reveals that the source ‘e2s3’ in the east 2 region may be associated with shock-excited H2 emission outflow or jet. The SED modelling of this new source indicates that it is a very young massive star that is not yet able to drive an H ii region.

Keywords: stars: formation; stars: pre-main-sequence; stars: winds, outflows; H ii regions; ISM: individual objects: S235; infrared: ISM

Journal Article.  11447 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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