Stellar Masses of Giant Clumps in CANDELS and Simulated Galaxies Using Machine Learning. (arXiv:2006.14636v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Huertas_Company_M/0/1/0/all/0/1">M. Huertas-Company</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guo_Y/0/1/0/all/0/1">Y. Guo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ginzburg_O/0/1/0/all/0/1">O. Ginzburg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_C/0/1/0/all/0/1">C.T. Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mandelker_N/0/1/0/all/0/1">N. Mandelker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Metter_M/0/1/0/all/0/1">M. Metter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Primack_J/0/1/0/all/0/1">J.R. Primack</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dekel_A/0/1/0/all/0/1">A. Dekel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ceverino_D/0/1/0/all/0/1">D. Ceverino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Faber_S/0/1/0/all/0/1">S.M. Faber</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koo_D/0/1/0/all/0/1">D.C. Koo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koekemoer_A/0/1/0/all/0/1">A. Koekemoer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Snyder_G/0/1/0/all/0/1">G. Snyder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giavalisco_M/0/1/0/all/0/1">M. Giavalisco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_H/0/1/0/all/0/1">H. Zhang</a>
A significant fraction of high redshift star-forming disc galaxies are known
to host giant clumps, whose formation, nature and role in galaxy evolution are
yet to be understood. In this work we first present a new automated method
based on deep neural networks to detect clumps in galaxy images and show that
it is more sensitive and faster than previous proposed methods. We then use
this method to systematically detect clumps in the rest-frame optical and UV
images of a complete sample of $sim1500$ star forming galaxies at $1<z<3$ in
the CANDELS survey as well as in images from the VELA forward modeled zoom-in
cosmological simulations. We show that observational effects have a dramatic
impact on the derived clump properties leading to an overestimation of the
clump mass up to a factor of 10, which highlights the importance of fair and
direct comparisons between observations and simulations. After correcting for
these effects with a simple mixture density network, we estimate that the clump
stellar mass function follows a power-law down to the completeness limit
($10^{7}$ solar masses) with the majority of the clumps being less massive than
$10^9$ solar masses. We find that between $20-40%$ of $sim10^{10}$ solar mass
star-forming galaxies contain at least one massive ($M_c>10^{7}M_odot$)
off-centered clump but only $sim2-5%$ of the total galaxy stellar mass is in
those clumps. We also show indications that the contribution of clumps to the
stellar mass is more important in extended and low mass galaxies. The
simulations explored in this work overall reproduce the shape of the observed
clump stellar mass function when confronted under the same conditions although
tend to lie in the lower limit of the confidence intervals of the observations.
This agreement suggests that most of the observed clumps are formed in-situ
through violent disk instabilities.
A significant fraction of high redshift star-forming disc galaxies are known
to host giant clumps, whose formation, nature and role in galaxy evolution are
yet to be understood. In this work we first present a new automated method
based on deep neural networks to detect clumps in galaxy images and show that
it is more sensitive and faster than previous proposed methods. We then use
this method to systematically detect clumps in the rest-frame optical and UV
images of a complete sample of $sim1500$ star forming galaxies at $1<z<3$ in
the CANDELS survey as well as in images from the VELA forward modeled zoom-in
cosmological simulations. We show that observational effects have a dramatic
impact on the derived clump properties leading to an overestimation of the
clump mass up to a factor of 10, which highlights the importance of fair and
direct comparisons between observations and simulations. After correcting for
these effects with a simple mixture density network, we estimate that the clump
stellar mass function follows a power-law down to the completeness limit
($10^{7}$ solar masses) with the majority of the clumps being less massive than
$10^9$ solar masses. We find that between $20-40%$ of $sim10^{10}$ solar mass
star-forming galaxies contain at least one massive ($M_c>10^{7}M_odot$)
off-centered clump but only $sim2-5%$ of the total galaxy stellar mass is in
those clumps. We also show indications that the contribution of clumps to the
stellar mass is more important in extended and low mass galaxies. The
simulations explored in this work overall reproduce the shape of the observed
clump stellar mass function when confronted under the same conditions although
tend to lie in the lower limit of the confidence intervals of the observations.
This agreement suggests that most of the observed clumps are formed in-situ
through violent disk instabilities.
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