Emergence of an Ultra-Red Ultra-Massive Galaxy Cluster Core at $z=4$. (arXiv:2003.13694v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Long_A/0/1/0/all/0/1">Arianna S. Long</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cooray_A/0/1/0/all/0/1">Asantha Cooray</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_J/0/1/0/all/0/1">Jingzhe Ma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casey_C/0/1/0/all/0/1">Caitlin M. Casey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wardlow_J/0/1/0/all/0/1">Julie L. Wardlow</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nayyeri_H/0/1/0/all/0/1">Hooshang Nayyeri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ivison_R/0/1/0/all/0/1">R.J. Ivison</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farrah_D/0/1/0/all/0/1">Duncan Farrah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dannerbauer_H/0/1/0/all/0/1">Helmut Dannerbauer</a>

Recent simulations and observations of massive galaxy cluster evolution
predict that the majority of stellar mass build up happens within cluster
members by $z=2$, before cluster virialization. Protoclusters rich with dusty,
star-forming galaxies (DSFGs) at $z>3$ are the favored candidate progenitors
for these massive galaxy clusters at $zsim0$. We present here the first study
analyzing stellar emission along with cold dust and gas continuum emission in a
spectroscopically confirmed $z=4.002$ protocluster core rich with DSFGs, the
Distant Red Core (DRC). We combine new textit{HST} and textit{Spitzer} data
with existing Gemini, textit{Herschel}, and ALMA observations to derive
individual galaxy-level properties, and compare them to coeval field and other
protocluster galaxies. All of the protocluster members are massive ($>10^{10}$
M$_odot$), but not significantly more so than their coeval field counterparts.
Within uncertainty, all are nearly indistinguishable from galaxies on the
star-forming vs. stellar mass main-sequence relationship. However, when placed
on the star formation efficiency plane, DRC components exhibit starburst-like
characteristics with SFRs 10-100$times$ greater than the expected field value
at a given molecular gas mass. Assuming no future major influx of fresh gas, we
estimate that these gas poor (f$_mathrm{gas}<25%$) yet bursty DSFGs will
deplete their gas reservoirs in $<30$ Myr. Using various methodologies, we
derive a total $z=4$ halo mass of $sim10^{14}$ M$_odot$, and estimate that
the DRC will evolve to become an ultra-massive cluster core of mass
$gtrsim10^{15}$ M$_odot$ by $z=0$.

Recent simulations and observations of massive galaxy cluster evolution
predict that the majority of stellar mass build up happens within cluster
members by $z=2$, before cluster virialization. Protoclusters rich with dusty,
star-forming galaxies (DSFGs) at $z>3$ are the favored candidate progenitors
for these massive galaxy clusters at $zsim0$. We present here the first study
analyzing stellar emission along with cold dust and gas continuum emission in a
spectroscopically confirmed $z=4.002$ protocluster core rich with DSFGs, the
Distant Red Core (DRC). We combine new textit{HST} and textit{Spitzer} data
with existing Gemini, textit{Herschel}, and ALMA observations to derive
individual galaxy-level properties, and compare them to coeval field and other
protocluster galaxies. All of the protocluster members are massive ($>10^{10}$
M$_odot$), but not significantly more so than their coeval field counterparts.
Within uncertainty, all are nearly indistinguishable from galaxies on the
star-forming vs. stellar mass main-sequence relationship. However, when placed
on the star formation efficiency plane, DRC components exhibit starburst-like
characteristics with SFRs 10-100$times$ greater than the expected field value
at a given molecular gas mass. Assuming no future major influx of fresh gas, we
estimate that these gas poor (f$_mathrm{gas}<25%$) yet bursty DSFGs will
deplete their gas reservoirs in $<30$ Myr. Using various methodologies, we
derive a total $z=4$ halo mass of $sim10^{14}$ M$_odot$, and estimate that
the DRC will evolve to become an ultra-massive cluster core of mass
$gtrsim10^{15}$ M$_odot$ by $z=0$.

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