Kavli Affiliate: John D. Silverman
| First 5 Authors: D. Kakkad, D. Kakkad, , ,
| Summary:
Active Galactic Nuclei (AGN) are believed to play a central role in quenching
star formation by removing or destroying molecular gas from host galaxies via
radiation-pressure driven outflows and/or radio jets. Some studies of cold
molecular gas in galaxies at Cosmic Noon ($zsim2$) show that AGN have less
cold gas ($<$100 K) compared to mass-matched star-forming galaxies. However,
cold gas could also be shock-heated to warmer phases, detectable via H$_2$
transitions in the rest-frame near- and mid-infrared spectra. The Medium
Resolution Spectrograph (MRS) of the Mid-infrared Instrument (MIRI) aboard JWST
has opened a unique window to observe these emission lines in galaxies at
Cosmic Noon. We present the first detection of hot molecular gas in cid_346, an
X-ray AGN at $zsim2.2$, via the H$_2$ ro-vibrational transition at 2.12
$mu$m. We measure a hot molecular gas mass of $sim 8.0 times 10^5$
M$_odot$, which is $sim 10^5-10^6$ times lower than the cold molecular
gas mass. cid_346 is located in an environment with extended gas structures and
satellite galaxies. This is supported by detection of hot and cold molecular
gas out to distances $>$10 kpc in MIRI/MRS and ALMA data, respectively and
ancillary NIRCam imaging that reveals two satellite galaxies at distances of
$sim$0.4 arcsec (3.3 kpc) and $sim$0.9 arcsec (7.4 kpc) from the AGN. Our
results tentatively indicate that while the CO(3-2)-based cold gas phase
dominates the molecular gas mass at Cosmic Noon, H$_2$ ro-vibrational
transitions are effective in tracing hot molecular gas locally in regions that
may lack CO emission.
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