Abstract:
In this talk, I will present analysis of a spectroscopic
sample of 23 broad-line AGNs (BLAGNs) at 3≲z≲6 selected using
F322W2+F444W NIRCam/WFSS grism spectroscopy of the central 100 arcmin2
area of the NEXUS survey. Among these BLAGNs, 15 are classified as
Little Red Dots (LRDs) based on their rest-frame UV-optical spectral
slopes and compact morphology. The number density of LRDs is ∼1e-5
cMpc−3, with a hint of declining towards the lower end of the probed
redshift range. These BLAGNs and LRDs span broad Hα luminosities of
∼10^{42.2−43.7} erg s^−1, black hole masses of ∼1e6.3−1e8.4 M⊙, and
Eddington ratios of ∼0.1−1 (median value 0.4), though the black hole
mass and Eddington ratio estimates carry large systematic uncertainties.
Half of the LRDs show strong Balmer absorption, suggesting high-density
gas surrounding the line-emitting region. We detect extended (hundreds
of parsecs) rest-frame UV-optical emission from the host galaxy in the
majority of these LRDs, which contributes significantly or even
dominantly to their total UV emission. This host emission largely
accounts for the peculiar UV upturn of the LRD spectral energy
distribution. We also measure the small-scale (≲1cMpc) clustering of
these BLAGNs and LRDs by cross-correlating with a photometric galaxy
sample. Extrapolating the power-law two-point correlation function model
to large linear scales, we infer a linear bias of 3.30^{+2.88}_{−2.04}
and typical halo masses of a few ×1e11 h−1M⊙ for BLAGNs at the sample
median redshift of z∼4.5. However, the inferred linear bias and halo
masses of LRDs, while formally consistent with those for BLAGNs at
∼1.5σ, appear too large to be compatible with their space density,
suggesting LRDs may have strong excess clustering on small scales.
