Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation

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Main Authors: Baxter, Devontae C., Coil, Alison L., Nadler, Ethan O., Nelson, Dylan, Pillepich, Annalisa, Forrest, Ben, Giddings, Finn, Golden-Marx, Emmet, Lemaux, Brian C., Sikorski, Derek
Format: Preprint
Published: 2025
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author Baxter, Devontae C.
Coil, Alison L.
Nadler, Ethan O.
Nelson, Dylan
Pillepich, Annalisa
Forrest, Ben
Giddings, Finn
Golden-Marx, Emmet
Lemaux, Brian C.
Sikorski, Derek
author_facet Baxter, Devontae C.
Coil, Alison L.
Nadler, Ethan O.
Nelson, Dylan
Pillepich, Annalisa
Forrest, Ben
Giddings, Finn
Golden-Marx, Emmet
Lemaux, Brian C.
Sikorski, Derek
contents We use the TNG-Cluster simulation to investigate how stellar mass and star formation rate (SFR) incompleteness affect the identification of density peaks within galaxy protoclusters at different redshifts. Our analysis focuses on a sample of $352$ protoclusters, defined as the progenitor populations of galaxies that reside within the virialized region of $z=0$ clusters with $M_{\rm{200}}^{z=0}\sim10^{14.3-15.5}~{\rm M}_{\odot}$. For comparison, we define our "baseline" protocluster population as galaxies with ${M}_{\star}> 10^{8.5}~{\rm M}_{\odot}$ at any redshift. We find that ${M}_{\star}$-limited (${M}_{\star} > 10^{9.5}~{\rm M}_{\odot}$) and SFR-limited ($\rm{SFR} > 10~{\rm M}_{\odot} \mathrm{yr}^{-1}$) subpopulations recover the baseline highest galaxy density peak in roughly $\sim60\%$ of cases within an accuracy of $1.0$ pMpc (corresponding to an angular scale of $\sim 2-2.5$ arcmin) at $z > 2$. This recovery fraction drops to $\sim40-50\%$ when restricting to galaxies with ${M}_{\star} > 10^{10.0}~{\rm M}_{\odot}$. We find that the baseline highest galaxy density peaks typically coincide with the highest dark matter and stellar mass density peaks, with separations less than $0.5$ pMpc in $\sim60-75\%$ of cases at $z>2$. This agreement drops to $\sim45-50\%$ when restricting to galaxies with ${M}_{\star} > 10^{10.0}~{\rm M}_{\odot}$. These results indicate that identifying the densest regions of protoclusters -- i.e., the core -- is highly sensitive to stellar mass and SFR completeness limits. Nevertheless, at $z>2$ we find that the baseline highest galaxy density peaks are generally sites of enhanced star formation and accelerated mass growth relative to the remainder of the protocluster, consistent with some observational studies.
format Preprint
id arxiv_https___arxiv_org_abs_2504_03836
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation
Baxter, Devontae C.
Coil, Alison L.
Nadler, Ethan O.
Nelson, Dylan
Pillepich, Annalisa
Forrest, Ben
Giddings, Finn
Golden-Marx, Emmet
Lemaux, Brian C.
Sikorski, Derek
Astrophysics of Galaxies
We use the TNG-Cluster simulation to investigate how stellar mass and star formation rate (SFR) incompleteness affect the identification of density peaks within galaxy protoclusters at different redshifts. Our analysis focuses on a sample of $352$ protoclusters, defined as the progenitor populations of galaxies that reside within the virialized region of $z=0$ clusters with $M_{\rm{200}}^{z=0}\sim10^{14.3-15.5}~{\rm M}_{\odot}$. For comparison, we define our "baseline" protocluster population as galaxies with ${M}_{\star}> 10^{8.5}~{\rm M}_{\odot}$ at any redshift. We find that ${M}_{\star}$-limited (${M}_{\star} > 10^{9.5}~{\rm M}_{\odot}$) and SFR-limited ($\rm{SFR} > 10~{\rm M}_{\odot} \mathrm{yr}^{-1}$) subpopulations recover the baseline highest galaxy density peak in roughly $\sim60\%$ of cases within an accuracy of $1.0$ pMpc (corresponding to an angular scale of $\sim 2-2.5$ arcmin) at $z > 2$. This recovery fraction drops to $\sim40-50\%$ when restricting to galaxies with ${M}_{\star} > 10^{10.0}~{\rm M}_{\odot}$. We find that the baseline highest galaxy density peaks typically coincide with the highest dark matter and stellar mass density peaks, with separations less than $0.5$ pMpc in $\sim60-75\%$ of cases at $z>2$. This agreement drops to $\sim45-50\%$ when restricting to galaxies with ${M}_{\star} > 10^{10.0}~{\rm M}_{\odot}$. These results indicate that identifying the densest regions of protoclusters -- i.e., the core -- is highly sensitive to stellar mass and SFR completeness limits. Nevertheless, at $z>2$ we find that the baseline highest galaxy density peaks are generally sites of enhanced star formation and accelerated mass growth relative to the remainder of the protocluster, consistent with some observational studies.
title Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2504.03836