Kavli Affiliate: Luis C. Ho
| First 5 Authors: Jingbo Sun, Hengxiao Guo, Wenwen Zuo, Paulina Lira, Minfeng Gu
| Summary:
The search for robust evidence of intermediate-mass black holes (IMBHs) is
crucial for understanding black hole seeding process and the formation of
supermassive black holes in the early Universe. NGC 4395 and POX 52 are two
prototypical IMBH hosts, both exhibiting multi-line evidence of low-mass black
hole activity. Here, we report the first detection of mid-infrared (MIR) lags
in response to optical variability, with measurements of $3.0^{+2.4}_{-1.9}$
days for NGC 4395 and $35.2^{+14.2}_{-11.7}$ days for POX~52 at $3.4$ $mu$m,
respectively, using archival optical data and observations from the Wide-field
Infrared Survey Explorer (WISE). This detection provides the first
reverberation evidence of low-mass black hole activity in POX 52. The time lags
of these two low-mass, low-luminosity active galactic nuclei (AGNs) generally
follow the extent of the $R_{rm dust}-L_{rm 5100}$ relation found in
higher-mass AGNs. Based on an empirical relation between the broad-line region
and dusty torus size, we constrain the black hole mass of POX 52 to log($M_{rm
BH}$/$M_odot$) = 5.5 $pm$ 0.37 (systemic and statistical errors), confirming
its IMBH nature. Furthermore, long-term optical continuum monitoring of POX 52
reveals a mild inter-band lag of $lesssim$ 1 day. However, no significant
intranight variability was detected during its one-night, high-cadence
monitoring, which we attribute to the longer duty cycle of fast variability in
POX 52 compared to that in NGC 4395.
| Search Query: ArXiv Query: search_query=au:”Luis C. Ho”&id_list=&start=0&max_results=3