Not-so-little Red Dots: Two massive and dusty starbursts at z~5-7 pushing the limits of star formation discovered by JWST in the COSMOS-Web survey

Fuente: arXiv

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Main Authors:	Gentile, Fabrizio, Casey, Caitlin M., Akins, Hollis B., Franco, Maximilien, McKinney, Jed, Berman, Edward, Cooper, Olivia R., Drakos, Nicole E., Hirschmann, Michaela, Long, Arianna S., Magdis, Georgios, Koekemoer, Anton M., Kokorev, Vasily, Shuntov, Marko, Talia, Margherita, Allen, Natalie, Harish, Santosh, Ilbert, Olivier, McCracken, Henry J., Kartaltepe, Jeyhan S., Liu, Daizhong, Paquereau, Louise, Rhodes, Jason, Rich, Michael R., Robertson, Brant, Toft, Sune, Gozaliasl, Ghassem
Format:	Preprint
Published:	2024
Subjects:	Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics
Online Access:	Acceder al recurso
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_version_	1866910588950544384
author	Gentile, Fabrizio Casey, Caitlin M. Akins, Hollis B. Franco, Maximilien McKinney, Jed Berman, Edward Cooper, Olivia R. Drakos, Nicole E. Hirschmann, Michaela Long, Arianna S. Magdis, Georgios Koekemoer, Anton M. Kokorev, Vasily Shuntov, Marko Talia, Margherita Allen, Natalie Harish, Santosh Ilbert, Olivier McCracken, Henry J. Kartaltepe, Jeyhan S. Liu, Daizhong Paquereau, Louise Rhodes, Jason Rich, Michael R. Robertson, Brant Toft, Sune Gozaliasl, Ghassem
author_facet	Gentile, Fabrizio Casey, Caitlin M. Akins, Hollis B. Franco, Maximilien McKinney, Jed Berman, Edward Cooper, Olivia R. Drakos, Nicole E. Hirschmann, Michaela Long, Arianna S. Magdis, Georgios Koekemoer, Anton M. Kokorev, Vasily Shuntov, Marko Talia, Margherita Allen, Natalie Harish, Santosh Ilbert, Olivier McCracken, Henry J. Kartaltepe, Jeyhan S. Liu, Daizhong Paquereau, Louise Rhodes, Jason Rich, Michael R. Robertson, Brant Toft, Sune Gozaliasl, Ghassem
contents	We present the properties of two candidate massive ($M_\star\sim10^{11}M_\odot$) and dusty ($A_{\rm v}>2.5$ mag) galaxies at $z=5-7$ in the first 0.28 deg$^2$ of the COSMOS-Web survey. One object is spectroscopically confirmed at $z_{\rm spec}=5.051$, while the other has a robust $z_{\rm phot}=6.7\pm0.3$. Thanks to their extremely red colors ($F277W-F444W\sim1.7$ mag), these galaxies satisfy the nominal color-selection for the widely-studied ``little red dot" (LRD) population with the exception of their spatially-resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of SED-fitting tools and star formation histories, we estimate the stellar masses to be $\log(M_\star)=11.32^{+0.07}_{-0.15}$ $M_\odot$ and $\log(M_\star)=11.2^{+0.1}_{-0.2}$ $M_\odot$, respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of $ε_\star\sim0.25$ and $ε_\star\sim0.5$. Both are significantly higher than what is commonly observed in lower-z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high-z Lyman-Break Galaxies and some non-AGN dominated LRDs, such ``extended" LRDs represent another population that may require very efficient star formation at early times.
format	Preprint
id	arxiv_https___arxiv_org_abs_2408_10305
institution	arXiv
publishDate	2024
record_format	arxiv
spellingShingle	Not-so-little Red Dots: Two massive and dusty starbursts at z~5-7 pushing the limits of star formation discovered by JWST in the COSMOS-Web survey Gentile, Fabrizio Casey, Caitlin M. Akins, Hollis B. Franco, Maximilien McKinney, Jed Berman, Edward Cooper, Olivia R. Drakos, Nicole E. Hirschmann, Michaela Long, Arianna S. Magdis, Georgios Koekemoer, Anton M. Kokorev, Vasily Shuntov, Marko Talia, Margherita Allen, Natalie Harish, Santosh Ilbert, Olivier McCracken, Henry J. Kartaltepe, Jeyhan S. Liu, Daizhong Paquereau, Louise Rhodes, Jason Rich, Michael R. Robertson, Brant Toft, Sune Gozaliasl, Ghassem Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics We present the properties of two candidate massive ($M_\star\sim10^{11}M_\odot$) and dusty ($A_{\rm v}>2.5$ mag) galaxies at $z=5-7$ in the first 0.28 deg$^2$ of the COSMOS-Web survey. One object is spectroscopically confirmed at $z_{\rm spec}=5.051$, while the other has a robust $z_{\rm phot}=6.7\pm0.3$. Thanks to their extremely red colors ($F277W-F444W\sim1.7$ mag), these galaxies satisfy the nominal color-selection for the widely-studied ``little red dot" (LRD) population with the exception of their spatially-resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of SED-fitting tools and star formation histories, we estimate the stellar masses to be $\log(M_\star)=11.32^{+0.07}_{-0.15}$ $M_\odot$ and $\log(M_\star)=11.2^{+0.1}_{-0.2}$ $M_\odot$, respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of $ε_\star\sim0.25$ and $ε_\star\sim0.5$. Both are significantly higher than what is commonly observed in lower-z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high-z Lyman-Break Galaxies and some non-AGN dominated LRDs, such ``extended" LRDs represent another population that may require very efficient star formation at early times.
title	Not-so-little Red Dots: Two massive and dusty starbursts at z~5-7 pushing the limits of star formation discovered by JWST in the COSMOS-Web survey
topic	Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics
url	https://arxiv.org/abs/2408.10305