Kavli Affiliate: Luis C. Ho
| First 5 Authors: Wen-Juan Liu, Wen-Juan Liu, , ,
| Summary:
We present a sample of 930 intermediate-mass black hole active galactic
nuclei (AGNs) with black hole masses of $M_mathrmBH leqslant 2 times
10^6$ M$_odot$, uniformly selected from the Seventeenth Data Release of
the Sloan Digital Sky Survey, based on the detection of broad H$alpha$ or
H$beta$ emission lines. Taking advantage of the wide wavelength coverage of
BOSS/eBOSS spectroscopy, our sample extends the redshift coverage of low-$z$
intermediate-mass black hole AGNs to $zleqslant0.57$, significantly improving
upon previous studies that where generally limited to $zleqslant0.35$. This
sample encompasses black hole masses from $10^4.0$ to $10^6.3$ M$_odot$,
with Eddington ratios ranging from 0.01 to 1.9. Among the $z>0.3$ subset, 24
sources exhibit detectable broad Mg II $lambdalambda2796,2803$ emission
lines, including eight confirmed by independent DESI spectra. A preliminary
analysis reveals a marked decline in both the maximum accretion rate
($L/L_mathrmEdd$) and broad-H$alpha$ luminosity with decreasing redshift,
possibly reflecting a cosmic evolution of accretion activity at the low-mass
end, akin to the “downsizing” evolutionary trend seen in high-mass AGNs.
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