Journal Article

Do black hole masses scale with classical bulge luminosities only? The case of the two composite pseudo-bulge galaxies NGC 3368 and NGC 3489*

N. Nowak, J. Thomas, P. Erwin, R. P. Saglia, R. Bender and R. I. Davies

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 2, pages 646-672
Published in print April 2010 | ISSN: 0035-8711
Published online March 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.16167.x
Do black hole masses scale with classical bulge luminosities only? The case of the two composite pseudo-bulge galaxies NGC 3368 and NGC 3489*

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It is now well established that all galaxies with a massive bulge component harbour a central supermassive black hole (SMBH). The mass of the SMBH correlates with bulge properties such as the bulge mass and the velocity dispersion, which implies that the bulge and the central BH of a galaxy have grown together during the formation process. As part of an investigation of the dependence of the SMBH mass on bulge types and formation mechanisms, we present measurements of SMBH masses in two pseudo-bulge galaxies. The spiral galaxy NGC 3368 is double-barred and hosts a large pseudo-bulge with a tiny classical bulge component at the very centre. The S0 galaxy NGC 3489 has only a weak large-scale bar, a small pseudo-bulge and a small classical bulge. Both galaxies show weak nuclear activity in the optical, indicative of the presence of an SMBH. We present high-resolution, adaptive-optics-assisted, near-IR integral-field data of these two galaxies, taken with SINFONI at the Very Large Telescope, and use axisymmetric orbit models to determine the masses of the SMBHs. The SMBH mass of NGC 3368, averaged over the four quadrants, is 〈M〉= 7.5 × 106 M with an error of 1.5 × 106 M, which mostly comes from the non-axisymmetry in the data. For NGC 3489, a solution without a BH cannot be excluded when modelling the SINFONI data alone, but can be clearly ruled out when modelling a combination of SINFONI, OASIS and SAURON data, for which we obtain M= (6.00+0.56−0.54stat± 0.64∣sys) × 106 M. Although both galaxies seem to be consistent with the M–σ relation, at face value they do not agree with the relation between bulge magnitude and BH mass when the total bulge magnitude (i.e. including both classical bulge and pseudo-bulge) is considered; the agreement is better when only the small classical bulge components are considered. However, taking into account the ageing of the stellar population could change this conclusion.

Keywords: galaxies: bulges; galaxies: individual: NGC 3368; galaxies: individual: NGC 3489; galaxies: kinematics and dynamics

Journal Article.  17607 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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