The Resolved Distributions of Dust Mass and Temperature in Local Group Galaxies. (arXiv:1902.08629v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Utomo_D/0/1/0/all/0/1">Dyas Utomo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiang_I/0/1/0/all/0/1">I-Da Chiang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leroy_A/0/1/0/all/0/1">Adam K. Leroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sandstrom_K/0/1/0/all/0/1">Karin M. Sandstrom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chastenet_J/0/1/0/all/0/1">Jeremy Chastenet</a>
We utilize archival far-infrared maps from the Herschel Space Observatory in
four Local Group galaxies (Small and Large Magellanic Clouds, M31, and M33). We
model their Spectral Energy Distribution (SED) from 100 to 500 $mu$m using a
single-temperature modified blackbody emission with a fixed emissivity index of
$beta = 1.8$. From the best-fit model, we derive the dust temperature, $T_{rm
d}$, and the dust mass surface density, $Sigma_{rm d}$, at 13 parsec
resolution for SMC and LMC, and at 167 parsec resolution for all targets. This
measurement allows us to build the distribution of dust mass and luminosity as
functions of dust temperature and mass surface density. We compare those
distribution functions among galaxies and between regions in a galaxy. We find
that LMC has the highest mass-weighted average $T_{rm d}$, while M31 and M33
have the lowest mass-weighted average $T_{rm d}$. Within a galaxy, star
forming regions have higher $T_{rm d}$ and $Sigma_{rm d}$ relative to the
overall distribution function, due to more intense heating by young stars and
higher gas mass surface density. When we degrade the resolutions to mimic
distant galaxies, the mass-weighted mean temperature gets warmer as the
resolution gets coarser, meaning the temperature derived from unresolved
observation is systematically higher than that in highly resolved observation.
As an implication, the total dust mass is lower (underestimated) in coarser
resolutions. This resolution-dependent effect is more prominent in clumpy
star-forming galaxies (SMC, LMC, and M33), and less prominent in more quiescent
massive spiral (M31).
We utilize archival far-infrared maps from the Herschel Space Observatory in
four Local Group galaxies (Small and Large Magellanic Clouds, M31, and M33). We
model their Spectral Energy Distribution (SED) from 100 to 500 $mu$m using a
single-temperature modified blackbody emission with a fixed emissivity index of
$beta = 1.8$. From the best-fit model, we derive the dust temperature, $T_{rm
d}$, and the dust mass surface density, $Sigma_{rm d}$, at 13 parsec
resolution for SMC and LMC, and at 167 parsec resolution for all targets. This
measurement allows us to build the distribution of dust mass and luminosity as
functions of dust temperature and mass surface density. We compare those
distribution functions among galaxies and between regions in a galaxy. We find
that LMC has the highest mass-weighted average $T_{rm d}$, while M31 and M33
have the lowest mass-weighted average $T_{rm d}$. Within a galaxy, star
forming regions have higher $T_{rm d}$ and $Sigma_{rm d}$ relative to the
overall distribution function, due to more intense heating by young stars and
higher gas mass surface density. When we degrade the resolutions to mimic
distant galaxies, the mass-weighted mean temperature gets warmer as the
resolution gets coarser, meaning the temperature derived from unresolved
observation is systematically higher than that in highly resolved observation.
As an implication, the total dust mass is lower (underestimated) in coarser
resolutions. This resolution-dependent effect is more prominent in clumpy
star-forming galaxies (SMC, LMC, and M33), and less prominent in more quiescent
massive spiral (M31).
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