NGC 1275: an outlier of the black hole-host scaling relations

Abstract

The active galaxy NGC 1275 lies at the center of the Perseus cluster of galaxies, being an archetypal BH-galaxy system that is supposed to fit well with the M_BH-host scaling relations obtained for quiescent galaxies. Since it harbours an obscured AGN, only recently our group has been able to estimate its black hole mass. Here our aim is to pinpoint NGC 1275 on the less dispersed scaling relations, namely the M_BH-sigma_star and M_BH-L_bul planes. Starting from our previous work Ricci et al. 2017b, we estimate that NGC 1275 falls well outside the intrinsic dispersion of the M_BH-sigma_star plane being ~1.2 dex (in black hole mass) displaced with respect to the scaling relations. We then perform a 2D morphological decomposition analysis on Spitzer/IRAC images at 3.6 mic and find that, beyond the bright compact nucleus that dominates the central emission, NGC 1275 follows a de Vaucouleurs profile with no sign of significant star formation nor clear merger remnants. Nonetheless, its displacement on the M_BH-L_(3.6,bul) plane with respect to the scaling relation is as high as observed in the M_BH-sigma_star.