Introducing the Search for Intermediate-mass Black Holes in Nearby Galaxies (SIBLING) Survey

Abstract

Intermediate mass black holes (IMBHs) have masses between the 10 2 −10 6 M and are key to our understanding of the formation of massive black holes. The known population of IMBH remains small, with a few hundred candidates and only a handful of them confirmed as bona-fide IMBHs. Until now, the most widely used selection method is based on spectral analysis. Here we present a methodology to select IMBH candidates via optical variability analysis of the nuclear region of local galaxies (z 0.35). Active IMBH accreting at low rates show small amplitude variability with time scales of hours, as it is seen in one of the known IMBH NGC4395. We found a sample of ∼ 500 galaxies evidencing fast and small amplitude variation in their weekly based light curves. We estimate an average occupancy fraction of 4% and a surface density of ∼ 3 deg −2 , which represent an increase by a factor of ∼ 40 compared to previous searches. A large fraction (78%) of the candidates are in spiral galaxies. We preliminary confirm the AGN nature of 22 sources via BPT diagrams using SDSS legacy spectra. Further confirmation of these candidates will require multiwavelength observations, especially in X-ray and radio bands.

Search of Intermediate Mass Black Holes at Low Redshift with Intra-night Variability

“…However, by detecting variability, these targets can be confirmed as mass accreting IMBHs. While various studies performed variability analysis over a relatively long time scale for identifying IMBH candidates (e.g., Baldassare et al 2018;Martínez-Palomera et al 2020), Short-time scale, i.e., intra-night variability studies are rare. We compare our results with the intra-night variability analysis conducted by Kim et al (2018), who monitored AGN candidates in the SMBH regime.…”

“…For example, detection of the high-luminosity of X-ray emission can provide a constraint to confirm whether they are mass-accreting BHs since AGNs are sources of strong Xray radiation (e.g., Elvis et al 1978;Nucita et al 2017;Chilingarian et al 2018;Liu et al 2018). Variability also provides strong constraints as the AGN continuum and emission line flux changes over time (e.g., Rodríguez-Pascual et al 1997;Walsh et al 2009;Rakshit & Stalin 2017;Baldassare et al 2018;Martínez-Palomera et al 2020). In the case of IMBH, variability test over intranight or several day time scale is a crucial tool for identification of these candidates (e.g., Mushotzky et al 2011;Aranzana et al 2018;Kim et al 2018).…”

Optical Variability of the Dwarf AGN NGC 4395 from the Transiting Exoplanet Survey Satellite

“…Discovering low-mass SMBHs (e.g., 10 6 M ) and furthermore, measuring their occupation fraction among low-mass galaxies, are of critical importance to understanding the seeding scenarios of SMBHs (e.g., Greene et al 2019) and the co-evolution between central BHs and host galaxies (e.g., Kormendy & Ho 2013). Motivated by the increasing availability of light curves from optical surveys, several recent stud-arXiv:2005.04491v2 [astro-ph.GA] 24 Aug 2020 ies have identified dwarf AGNs using optical variability (e.g., Baldassare et al 2018;Martínez-Palomera et al 2020;Secrest & Satyapal 2020). However, due in part to the limited cadence of these surveys and the signalto-noise ratio of the intrinsic variability, the selection rates are generally low (a few percent) and the sampling is insufficient to study the variability properties of dwarf AGNs at days to hours timescales.…”

Feeding and feedback from little monsters: AGN in dwarf galaxies

“…A few more tens have been recently identified based on optical variability (e.g. Baldassare et al 2018;Martínez-Palomera et al 2020).…”