A Census of Star Formation in the Outer Galaxy II: The GLIMPSE360 Field. (arXiv:2006.03080v1 [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:+Tolls_V/0/1/0/all/0/1">Volker Tolls</a>
We have conducted a study of star formation in the outer Galaxy from
65degr$< l <$265degr~in the region observed by the GLIMPSE360 program. This
{it Spitzer} warm mission program mapped the plane of the outer Milky Way with
IRAC at 3.6 and 4.5~$mu$m. We combine the IRAC, {it WISE}, and 2MASS catalogs
and our previous results from another outer Galaxy survey and identify a total
of 47,338 Young Stellar Objects (YSOs) across the field spanning $>$180degr
in Galactic longitude. Using the $DBSCAN$ method on the combined catalog, we
identify 618 clusters or aggregations of YSOs having 5 or more members. We
identify 10,476 Class I, 29,604 Class II, and 7,325 anemic Class II/Class III
YSOs. The ratio of YSOs identified as members of clusters was 25,528/47,338, or
54%. We found 100 of the clusters identified have previously measured
distances in the {it WISE} ion{H}{2} survey. We used these distances in our
spectral energy distribution (SED) fitting of the YSOs in these clusters, of
which 96 had YSOs with $<3sigma$ fits. We used the derived masses from the SED
model fits to estimate the initial mass function (IMF) in the inner and outer
Galaxy clusters: dividing the clusters by Galactocentric distances, the slopes
were $Gamma = 1.87 pm 0.31$ above 3~M$_{odot}$ for $R_{Gal} < 11.5$~kpc and
$Gamma = 1.15 pm 0.24$ above 3~M$_{odot}$ for $R_{Gal} > 11.5$~kpc. The
slope of the combined IMF was found to be $Gamma = 1.92 pm 0.42$ above
3~M$_{odot}$. These values are consistent with each other within the
uncertainties, and with literature values in the inner Galaxy high-mass star
formation regions. The slopes are likely also consistent with a universal
Salpeter IMF.
We have conducted a study of star formation in the outer Galaxy from
65degr$< l <$265degr~in the region observed by the GLIMPSE360 program. This
{it Spitzer} warm mission program mapped the plane of the outer Milky Way with
IRAC at 3.6 and 4.5~$mu$m. We combine the IRAC, {it WISE}, and 2MASS catalogs
and our previous results from another outer Galaxy survey and identify a total
of 47,338 Young Stellar Objects (YSOs) across the field spanning $>$180degr
in Galactic longitude. Using the $DBSCAN$ method on the combined catalog, we
identify 618 clusters or aggregations of YSOs having 5 or more members. We
identify 10,476 Class I, 29,604 Class II, and 7,325 anemic Class II/Class III
YSOs. The ratio of YSOs identified as members of clusters was 25,528/47,338, or
54%. We found 100 of the clusters identified have previously measured
distances in the {it WISE} ion{H}{2} survey. We used these distances in our
spectral energy distribution (SED) fitting of the YSOs in these clusters, of
which 96 had YSOs with $<3sigma$ fits. We used the derived masses from the SED
model fits to estimate the initial mass function (IMF) in the inner and outer
Galaxy clusters: dividing the clusters by Galactocentric distances, the slopes
were $Gamma = 1.87 pm 0.31$ above 3~M$_{odot}$ for $R_{Gal} < 11.5$~kpc and
$Gamma = 1.15 pm 0.24$ above 3~M$_{odot}$ for $R_{Gal} > 11.5$~kpc. The
slope of the combined IMF was found to be $Gamma = 1.92 pm 0.42$ above
3~M$_{odot}$. These values are consistent with each other within the
uncertainties, and with literature values in the inner Galaxy high-mass star
formation regions. The slopes are likely also consistent with a universal
Salpeter IMF.
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