Kavli Affiliate: Luis C. Ho
| First 5 Authors: Chang-Hao Chen, Luis C. Ho, Ruancun Li, Ming-Yang Zhuang,
| Summary:
We investigate the host galaxy properties of eight little red dots (LRDs)
selected from the JWST UNCOVER survey, applying a new technique ({ttstring
GalfitS}) to simultaneously fit the morphology and spectral energy distribution
using multi-band NIRCam images covering $sim 1-4,mu {rm m}$. We detect the
host galaxy in only one LRD, MSAID38108 at $z = 4.96$, which has a stellar mass
of $log (M_*/M_{odot}) = 8.66^{+0.24}_{-0.23}$, an effective radius
$R_e=0.66^{+0.08}_{-0.05}$ kpc, and a S’ersic index $n=0.71^{+0.07}_{-0.08}$.
No host emission centered on the central point source is found in the other
seven LRDs. We derive stringent upper limits for the stellar mass of a
hypothetical host galaxy by conducting realistic mock simulations that place
high-redshift galaxy images under the LRDs. Based on the black hole masses
estimated from the broad H$alpha$ emission line, the derived stellar mass
limits are at least a factor of 10 lower than expected from the $z approx 0$
scaling relation between black hole mass and host galaxy stellar mass.
Intriguingly, four of the LRDs (50% of the sample) show extended, off-centered
emission, which is particularly prominent in the bluer bands. The asymmetric
emission of two sources can be modeled as stellar emission, but the nature of
the other two is unclear.
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