A Census Star Formation in the Outer Galaxy: the SMOG field. (arXiv:1906.03267v1 [astro-ph.GA])

A Census Star Formation in the Outer Galaxy: the SMOG field. (arXiv:1906.03267v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Winston_E/0/1/0/all/0/1">Elaine Winston</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hora_J/0/1/0/all/0/1">Joseph Hora</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gutermuth_R/0/1/0/all/0/1">Robert Gutermuth</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tolls_V/0/1/0/all/0/1">Volker Tolls</a>

In this paper we undertake a study of the 21 square degree SMOG field, a
Spitzer cryogenic mission Legacy program to map a region of the outer Milky Way
towards the Perseus and Outer spiral arms with the IRAC and MIPS instruments.
We identify 4648 YSOs across the field. Using the DBSCAN method we identify 68
clusters or aggregations of YSOs in the region, having 8 or more members. We
identify 1197 class Is, 2632 class IIs, 819 class IIIs, of which 45 are
candidate transition disk objects, utilizing the MIPS 24 photometry. The ratio
of YSOs identified as members of clusters was 2872/4648, or 62%. The ratios of
class I to class II YSOs in the clusters are broadly consistent with those
found in the inner galactic and nearby Gould’s Belt young star formation
regions. The clustering properties indicate that the protostars may be more
tightly bound to their natal sites than the class IIs, and the class IIIs are
generally widely distributed. We further perform an analysis of the WISE data
of the SMOG field to determine how the lower resolution and sensitivity of WISE
affects the identification of YSOs as compared to Spitzer: we identify 931 YSOs
using combined WISE and 2MASS photometry, 931/4648 or 20% of the total number
identified with Spitzer. Performing the same clustering analysis finds 31
clusters which reliably trace the larger associations identified with the
Spitzer data. Twelve of the clusters identified have previously measured
distances from the WISE HII survey. SEDFitter modeling of these YSOs is
reported, leading to an estimation of the IMF in the aggregate of these
clusters which approximates that found in the inner galaxy, implying that the
processes behind stellar mass distribution during star formation are not widely
affected by the lower density and metallicity of the outer galaxy.

In this paper we undertake a study of the 21 square degree SMOG field, a
Spitzer cryogenic mission Legacy program to map a region of the outer Milky Way
towards the Perseus and Outer spiral arms with the IRAC and MIPS instruments.
We identify 4648 YSOs across the field. Using the DBSCAN method we identify 68
clusters or aggregations of YSOs in the region, having 8 or more members. We
identify 1197 class Is, 2632 class IIs, 819 class IIIs, of which 45 are
candidate transition disk objects, utilizing the MIPS 24 photometry. The ratio
of YSOs identified as members of clusters was 2872/4648, or 62%. The ratios of
class I to class II YSOs in the clusters are broadly consistent with those
found in the inner galactic and nearby Gould’s Belt young star formation
regions. The clustering properties indicate that the protostars may be more
tightly bound to their natal sites than the class IIs, and the class IIIs are
generally widely distributed. We further perform an analysis of the WISE data
of the SMOG field to determine how the lower resolution and sensitivity of WISE
affects the identification of YSOs as compared to Spitzer: we identify 931 YSOs
using combined WISE and 2MASS photometry, 931/4648 or 20% of the total number
identified with Spitzer. Performing the same clustering analysis finds 31
clusters which reliably trace the larger associations identified with the
Spitzer data. Twelve of the clusters identified have previously measured
distances from the WISE HII survey. SEDFitter modeling of these YSOs is
reported, leading to an estimation of the IMF in the aggregate of these
clusters which approximates that found in the inner galaxy, implying that the
processes behind stellar mass distribution during star formation are not widely
affected by the lower density and metallicity of the outer galaxy.

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