Professor Andrew Bunker

Abstract:

The depth and coverage of the first years of James Webb Space Telescope observations have revealed low-luminosity active galactic nuclei (AGN) across a wide redshift range, shedding light on black hole (BH) assembly and feedback. We present our spectroscopic sample of 34 Type 1 AGN obtained from JADES survey data and spanning . Our sample of AGN probes a BH mass range of M at bolometric luminosities down to erg s. Most of these AGN are hosted in low-mass ( M) galaxies and are overmassive relative to the local relation, while remaining consistent with the local – relation. The wide redshift range provided by our sample allows us to trace the emergence of local – scaling relation across cosmic time. Additionally, we explore the capability of narrow-line diagnostics in identifying Type 2 AGN and find that a significant fraction of our AGN would be missed by them due to low metallicity or lack of high-energy ionizing photons. We explore the UV luminosity function of AGN and their hosts and find that it is subject to significant cosmic variance and is also dependent on the AGN bolometric luminosity. Finally, we show that the electron scattering scenario recently proposed to explain broad Balmer lines is untenable on multiple grounds showing that there is no evidence of significant BH mass overestimation.

Abstract:

We study the large-scale environments and clustering properties of 28 low-luminosity active galactic nuclei (AGNs) at z = 3.9–6 in the GOODS-N field. Our sample, identified from the JWST NIRCam Imaging and WFSS data in Complete NIRCam Grism Redshift Survey and First Reionization Epoch Spectroscopically Complete Observations surveys with either broad Hα emission lines or V-shaped continua, are compared to 782 Hα emitters (HAEs) selected from the same data. These AGNs are located in diverse large-scale environments and do not preferentially reside in denser environments compared to HAEs. Their overdensity field, δ, averaged over (15 h−1 cMpc)3, ranges from −0.56 to 10.56, and shows no clear correlation with broad-line luminosity, black hole (BH) masses, or the AGN fraction. It suggests that >10 cMpc structures do not significantly influence BH growth. We measure the two-point cross-correlation function of AGNs with HAEs, finding a comparable amplitude to that of the HAE autocorrelation. This indicates similar bias parameters and host dark matter halo masses for AGNs and HAEs. The correlation length of field AGNs is 4.26 h−1 cMpc and 7.66 h−1 cMpc at 3.9 < z < 5 and 5 < z < 6, respectively. We infer a median host dark matter halo mass of log(Mh/M⊙)≈11.0−11.2 and host stellar masses of log(M⋆/M⊙)≈8.4–8.6 by comparing with the UniverseMachine simulation. Our clustering analysis suggests that low-luminosity AGNs at high redshift reside in normal star-forming galaxies with overmassive BHs. They represent an intrinsically distinct population from luminous quasars and could be a common phase in galaxy evolution.

Abstract:

In Paper I, we exploited the unsurpassed resolution and depth of JWST/NIRCam imagery to investigate the relationship between active galactic nuclei (AGN) and host-galaxy properties in the JWST era, finding a correlation between the level of spatial disturbance (as measured by shape asymmetry, AS) and obscuration (NH). Here in Paper II, we report an expansion of our X-ray and infrared analysis of Seyfert-luminosity host galaxies with four additional metrics to the single-metric morphology analysis of Paper I, as well as new samples of inactive control galaxies. This expanded study of one of the largest and most complete, multiwavelength samples of AGN detected at 0.6 < z < 3.8 in the GOODS-South and -North fields, confirms that mergers surprisingly play a significant role in obscured, subquasar AGN host galaxies. Additionally, the pattern of morphological disturbances observed amongst the X-ray- and mid-IR-selected AGN suggests that these represent different phases of AGN evolution tied to a major-merger timeline, as opposed to distinct populations of AGN. These results indicate that mergers are important in triggering subquasar AGN at these redshifts.