A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE): Broad-line AGN at $z=4-5$ revealed by JWST/NIRCam WFSS

Xiaojing Lin, Feige Wang, Xiaohui Fan, Zheng Cai, Jaclyn B. Champagne, Fengwu Sun, Marta Volonteri, Jinyi Yang, Joseph F. Hennawi, Eduardo Bañados, Aaron Barth, Anna-Christina Eilers, Emanuele Paolo Farina, Weizhe Liu, Xiangyu Jin, Hyunsung D. Jun, Alessandro Lupi, Koki Kakiichi, Chiara Mazzucchelli, Masafusa Onoue, Zhiwei Pan, Elia Pizzati, Sofía Rojas-Ruiz, Jan-Torge Schindler, Benny Trakhtenbrot, Yue Shen, Maxime Trebitsch, Ming-Yang Zhuang, Ryan Endsley, Romain A. Meyer, Zihao Li, Mingyu Li, Maria Pudoka, Wei Leong Tee, Yunjing Wu, Haowen Zhang

Published 2024-07-24Version 1

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.