# Low-mass and High-mass Supermassive Blackholes In Radio-Loud AGNs Are Spun-up in Different Evolution Paths

## TL;DR

This study compares host galaxy properties of radio-selected Seyfert 2 galaxies to understand how supermassive black holes are spun-up, revealing that high-mass and low-mass SMBHs are spun-up through different evolutionary paths involving mergers and secular processes.

## Contribution

It demonstrates a dichotomy in host galaxy properties linked to SMBH mass, supporting different spin-up mechanisms for high-mass and low-mass SMBHs.

## Key findings

- High-mass SMBHs are associated with classical bulges.
- Low-mass SMBHs are associated with pseudo-bulges.
- Different SMBH spin-up processes are confirmed.

## Abstract

How Supermassive Blackholes (SMBHs) are spun-up is a key issue of modern astrophysics. As an extension of the study in Wang et al. (2016), we here address the issue by comparing the host galaxy properties of nearby ($z<0.05$) radio-selected Seyfert 2 galaxies. With the two-dimensional bulge+disk decompositions for the SDSS $r$-band images, we identify a dichotomy on various host galaxy properties for the radio-powerful SMBHs. By assuming the radio emission from the jet reflects a high SMBH spin, which stems from the well-known BZ mechanism of jet production, high-mass SMBHs (i.e., $M_{\mathrm{BH}}>10^{7.9}M_\odot$) have a preference for being spun-up in classical bulges, and low-mass SMBHs (i.e., $M_{\mathrm{BH}}=10^{6-7}M_\odot$) in pseudo-bulges. This dichotomy suggests and confirms that high-mass and low-mass SMBHs are spun-up in different ways, i.e., a major "dry" merger and a secular evolution.