The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-Mass Protostars. (arXiv:2006.06424v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Liu_M/0/1/0/all/0/1">Mengyao Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tan_J/0/1/0/all/0/1">Jonathan C. Tan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buizer_J/0/1/0/all/0/1">James M. De Buizer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_Y/0/1/0/all/0/1">Yichen Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moser_E/0/1/0/all/0/1">Emily Moser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beltran_M/0/1/0/all/0/1">Maria T. Beltrán</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Staff_J/0/1/0/all/0/1">Jan E. Staff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tanaka_K/0/1/0/all/0/1">Kei E. I. Tanaka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Whitney_B/0/1/0/all/0/1">Barbara Whitney</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosero_V/0/1/0/all/0/1">Viviana Rosero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_Y/0/1/0/all/0/1">Yao-Lun Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fedriani_R/0/1/0/all/0/1">Rubén Fedriani</a>
We present multi-wavelength images observed with SOFIA-FORCAST from ~10 to 40
$mu$m of 14 protostars, selected as intermediate-mass protostar candidates, as
part of the SOFIA Massive (SOMA) Star Formation Survey. We build protostellar
spectral energy distributions (SEDs) with the SOFIA observations, together with
archival data from Spitzer, Herschel and IRAS. We then fit the SEDs with
radiative transfer (RT) models of Zhang & Tan (2018), based on Turbulent Core
Accretion theory, to estimate key properties of the protostars. The SEDs
generally indicate the validity of these RT models down to intermediate-mass
and/or early-stage protostars. The protostars analyzed so far in the SOMA
survey span a range of luminosities from ~$10^{2}$ to ~$10^{6} L_{odot}$,
current protostellar masses from ~0.5 to ~30 $M_{odot}$, and ambient clump
mass surface densities, $Sigma_{rm cl}$ of 0.1 – 3 g cm$^{-2}$. A wide range
of evolutionary states of the individual protostars and of the protocluster
environments are also probed. The 19 to 37 $mu$m spectral index of the sources
correlates with outflow cavity opening angle, ratio of this angle to viewing
angle, and evolutionary stage. We have also added a sample of ~50 protostellar
sources identified from within Infrared Dark Clouds and expected to be at the
earliest stages of their evolution. With this global sample, most of the
evolutionary stages of high- and intermediate-mass protostars are probed. From
the best fitting models of the protostars, there is no evidence of a threshold
value of protocluster clump mass surface density being needed to form
protostars up to ~25 $M_odot$. However, to form more massive protostars, there
is tentative evidence that $Sigma_{rm cl}$ needs to be at least 1 g
cm$^{-2}$. We discuss how this is consistent with expectations from core
accretion models that include internal feedback from the forming massive star.
We present multi-wavelength images observed with SOFIA-FORCAST from ~10 to 40
$mu$m of 14 protostars, selected as intermediate-mass protostar candidates, as
part of the SOFIA Massive (SOMA) Star Formation Survey. We build protostellar
spectral energy distributions (SEDs) with the SOFIA observations, together with
archival data from Spitzer, Herschel and IRAS. We then fit the SEDs with
radiative transfer (RT) models of Zhang & Tan (2018), based on Turbulent Core
Accretion theory, to estimate key properties of the protostars. The SEDs
generally indicate the validity of these RT models down to intermediate-mass
and/or early-stage protostars. The protostars analyzed so far in the SOMA
survey span a range of luminosities from ~$10^{2}$ to ~$10^{6} L_{odot}$,
current protostellar masses from ~0.5 to ~30 $M_{odot}$, and ambient clump
mass surface densities, $Sigma_{rm cl}$ of 0.1 – 3 g cm$^{-2}$. A wide range
of evolutionary states of the individual protostars and of the protocluster
environments are also probed. The 19 to 37 $mu$m spectral index of the sources
correlates with outflow cavity opening angle, ratio of this angle to viewing
angle, and evolutionary stage. We have also added a sample of ~50 protostellar
sources identified from within Infrared Dark Clouds and expected to be at the
earliest stages of their evolution. With this global sample, most of the
evolutionary stages of high- and intermediate-mass protostars are probed. From
the best fitting models of the protostars, there is no evidence of a threshold
value of protocluster clump mass surface density being needed to form
protostars up to ~25 $M_odot$. However, to form more massive protostars, there
is tentative evidence that $Sigma_{rm cl}$ needs to be at least 1 g
cm$^{-2}$. We discuss how this is consistent with expectations from core
accretion models that include internal feedback from the forming massive star.
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