  Low-luminosity AGNs with low-mass black holes (BHs) in the early universe are
fundamental to understanding the BH growth and their co-evolution with the host
galaxies. Utilizing JWST NIRCam Wide Field Slitless Spectroscopy (WFSS), we
perform a systematic search for broad-line ${\rm H\alpha}$ emitters (BHAEs) at
$z\approx 4-5$ in 25 fields of the ASPIRE (A SPectroscopic survey of biased
halos In the Reionization Era) project, covering a total area of 275
arcmin$^2$. We identify 16 BHAEs with FWHM of the broad components spanning
from $\sim$ 1000 km s$^{-1}$ to 3000 km s$^{-1}$. Assuming the broad linewidths
arise due to Doppler broadening around BHs, the implied BH masses range from
$10^7$ to $10^{8}~M_\odot$, with broad ${\rm H\alpha}$-converted bolometric
luminosity of $10^{44.5}-10^{45.5}$ erg s$^{-1}$ and Eddington ratios of
$0.07-0.47$. The spatially extended structure of the F200W stacked image may
trace the stellar light from the host galaxies. The ${\rm H\alpha}$ luminosity
function indicates an increasing AGN fraction towards the higher ${\rm
H\alpha}$ luminosities. We find possible evidence for clustering of BHAEs: two
sources are at the same redshift with a projected separation of 519 kpc; one
BHAE appears as a composite system residing in an overdense region with three
close companion ${\rm H\alpha}$ emitters. Three BHAEs exhibit blueshifted
absorption troughs indicative of the presence of high-column-density gas. We
find the broad-line and photometrically selected BHAE samples exhibit different
distributions in the optical continuum slopes, which can be attributed to their
different selection methods. The ASPIRE broad-line ${\rm H\alpha}$ sample
provides a good database for future studies of faint AGN populations at high
redshift.
