The supermassive black hole mass–Sérsic index relations for bulges and elliptical galaxies

Abstract

Scaling relations between supermassive black hole mass, M BH , and host galaxy properties are a powerful instrument for studying their coevolution. A complete picture involving all of the black hole scaling relations, in which each relation is consistent with the others, is necessary to fully understand the black hole-galaxy connection. The relation between M BH and the central light concentration of the surrounding bulge, quantified by the Sérsic index n, may be one of the simplest and strongest such relations, requiring only uncalibrated galaxy images. We have conducted a census of literature Sérsic index measurements for a sample of 54 local galaxies with directly measured M BH values. We find a clear M BH − n relation, despite an appreciable level of scatter due to the heterogeneity of the data. Given the current M BH − L sph and the L sph − n relations, we have additionally derived the expected M BH − n relations, which are marginally consistent at the 2σ level with the observed relations. Elliptical galaxies and the bulges of disc galaxies are each expected to follow two distinct bent M BH − n relations due to the Sérsic/core-Sérsic divide. For the same central light concentration, we predict that M BH in the Sérsic bulges of disc galaxies are an order magnitude higher than in Sérsic elliptical galaxies if they follow the same M BH − L sph relation.

THE LOCAL BLACK HOLE MASS FUNCTION DERIVED FROM THE MBH–P AND THE MBH–n RELATIONS

“…Indeed, one migh expect that a Sérsic index measured using a onedimensional fit (as performed in this paper) to be ∼10% smaller than that measured using a two-dimensional fit (Ferrari et al 2004). Furthermore, when measuring Sérsic index in multiple wavebands for the same galaxies, Savorgnan et al (2013) found that wavelength bias was completely dominated by these other biases, which could be as large as 50%. Given, the result of Kelvin et al (2012), we would expect the Sérsic index measured at 3.6µmto be less than 10% higher than that measured in the R-band, which is signifantly smaller than the 50% number given by Savorgnan et al (2013).…”

“…Recently, Sani et al (2011), Vika et al (2012 and Beifiori et al (2012) failed to recover a strong M bhn relation. Savorgnan et al (2013) re-investigated and recovered the relation using a large collection of literature Sérsic index measurements using R-band , I-band (Beifiori et al 2012), K-band (Vika et al 2012), and 3.6µm (Sani et al 2011) imaging data. Savorgnan et al (2013) discussed the systematic effects associated with measuring Sérsic index in different optical and infrared wavebands.…”

“…Savorgnan et al (2013) re-investigated and recovered the relation using a large collection of literature Sérsic index measurements using R-band , I-band (Beifiori et al 2012), K-band (Vika et al 2012), and 3.6µm (Sani et al 2011) imaging data. Savorgnan et al (2013) discussed the systematic effects associated with measuring Sérsic index in different optical and infrared wavebands. They concluded that the differences expected from measuring Sérsic index in different wavebands are smaller than the differences expected due to other systematic biases such as one-dimensional decomposition versus twodimensional decomposition, or the differences between measuring the Sérsic index along a minor axis versus measuring it along a major axis.…”

The effects of dust on the photometric parameters of decomposed disks and bulges

“…Sérsic indices of bulges are also important, as they provide a link to their supermassive black hole. Following on the work of Graham et al (2001) and Graham & Driver (2007a), recent work by Savorgnan et al (2013) found a clear supermassive black-hole mass − Sérsic index relation. Thus, if accurate Sérsic indices can be derived (corrected for the effect of dust and for projection effects), then these can be used to predict black hole masses in large samples of galaxies to derive the local black hole mass function (e.g.…”

A low-luminosity type-1 QSO sample

“…Tight correlations between the mass of the central supermassive black hole (SMBH) and properties of the hosting galaxy, particularly its central bulge component, have been found (Magorrian et al 1998;Ferrarese & Merritt 2000;Marconi & Hunt 2003;Häring & Rix 2004;Graham & Driver 2007;Savorgnan et al 2013) and are seen as evidence of a co-evolution of black holes and their host galaxies. More recent studies have revealed galaxies that do not follow these relations: Kormendy et al (2011) discuss that only "classical bulges" that formed from galaxy mergers show correlations with the SMBH, while disklike "pseudobulges" that are forming by secular evolution do not.…”