An optically-dark merging system at z~6 detected by JWST
Near- to mid-Infrared observations (from Spitzer and JWST) have revealed a hidden population of galaxies at redshift z=3-6, called optically-dark objects, which are believed to be massive and dusty star-formers. While optically-dark sources are widely recognized as a significant component of the ste...
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Main Authors | , , , , , , , , , , , , , , , , , , |
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Format | Journal Article |
Language | English |
Published |
07.05.2024
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Subjects | |
Online Access | Get full text |
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Summary: | Near- to mid-Infrared observations (from Spitzer and JWST) have revealed a
hidden population of galaxies at redshift z=3-6, called optically-dark objects,
which are believed to be massive and dusty star-formers. While optically-dark
sources are widely recognized as a significant component of the stellar mass
function, the history of their stellar mass assembly remains unexplored.
However, they are thought to be the progenitors of the more massive early-type
galaxies found in present-day groups and clusters. It is thus important to
examine the possible connection between dark sources and merging events, in
order to understand the environment in which they live. Here, we report our
search for close companions in a sample of 19 optically-dark objects identified
in the SMACS0723 JWST deep field. They were selected in the NIRCam F444W band
and undetected below 2mu. We restrict our analysis to the reddest (i.e.
F277W-F444W> 1.3) and brightest (F444W< 26 mag) objects. We have identified an
optically-dark source showing a very close companion (<0.5"). The spatially
resolved SED fitting procedure indicates that all components lying within 1.5"
from the dark source are indeed at z~5.7. Tidal features (leading to a whale
shaped morphology) corroborate the hypothesis that the dark source is the most
massive (log(M/Msun)>10.3) and dusty (Av~3 at the core) system of an ongoing
merger with a mass ratio of ~10. Similar merging systems are identified in the
SERRA simulations, allowing us to reconstruct their stellar mass assembly
history and predict their molecular gas properties The discovery of mergers
within dark galaxies at the end of the Epoch of Reionization underscores the
importance of conducting a statistical search for additional candidates in deep
NIRCam fields. Such research will aid in understanding the role of merging
processes during the obscured phase of stellar mass accumulation. |
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DOI: | 10.48550/arxiv.2405.04572 |