On the scaling relations of bulges and early-type galaxies

TL;DR

This study analyzes the structural properties and scaling relations of bulges in nearby spiral and early-type galaxies, revealing differences influenced by dust and inclination effects, and examining black hole correlations.

Contribution

It provides a detailed structural analysis of galaxy bulges using advanced decomposition methods and investigates the relations between bulge parameters, morphology, and black hole mass.

Findings

Dust and inclination significantly affect the Kormendy relation for spirals.

Bulge Sersic index and B/T ratio can help distinguish galaxy types.

Black hole mass relations are similar across bulge types.

Abstract

Following from our recent work, we present here a detailed structural analysis of a representative sample of nearby spiral and early-type galaxies taken from the KINGFISH/ SINGS survey. The photometric parameters of bulges are obtained from bulge-disc decompositions using GALFIT data analysis algorithm. The method and corrections for projection and dust effects previously obtained are used to derive intrinsic photometric and structural bulge parameters. We show the main bulge scaling relations and the black hole relations, both observed and intrinsic ones, in B band. We find dust and inclination effects to produce more important changes in the parameters of the Kormendy relation for spiral galaxies, with the respective bulges of late-type galaxies residing on a steeper slope relation that the early-type galaxies. We observe that the Kormendy relation in combination with a bulge S\'{e}rsic index ($n_{b}$) threshold, does not produce a conclusive morphological separation of bulges. The $n_{b}$- bulge-to-total flux ratio ($B/T$) and $B/T$-stellar mass could be used to discriminate between late-type and early-type galaxies, while a further use of these parameters to divide bulges with different morphologies is problematic due to overlaps in the two distributions or large spread in values. We confirm the existence of two distinct intrinsic relations between the bulge luminosity (or absolute magnitude) and S\'{e}rsic index for late- and early-type galaxies, while the relations between the black-hole mass ($M_{BH}$) and bulge luminosity are not found to be statistically different at p<0.05. Within errors, we find statistically similar intrinsic $M_{BH}-n_{b}$ relations for all bulges.