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تسجيل مستخدم جديدUsing 3D Spectroscopy to Probe the Orbital Structure of Composite Bulges
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Detailed imaging and spectroscopic analysis of the centers of nearby S0 and spiral galaxies shows the existence of composite bulges, where both classical bulges and disky pseudobulges coexist in the same galaxy. As part of a search for supermassive black holes in nearby galaxy nuclei, we obtained VLT-SINFONI observations in adaptive-optics mode of several of these galaxies. Schwarzschild dynamical modeling enables us to disentangle the stellar orbital structure of the different central components, and to distinguish the differing contributions of kinematically hot (classical bulge) and kinematically cool (pseudobulge) components in the same galaxy.
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We study nine S0-Sb galaxies with (photometric) bulges consisting of two distinct components. The outer component is a flattened, kinematically cool, disklike structure: a disky pseudobulge. Embedded inside is a rounder, kinematically hot spheroid: a
classical bulge. This indicates that pseudobulges and classical bulges are not mutually exclusive: some galaxies have both. The disky pseudobulges almost always have an exponential disk (scale lengths = 125-870 pc, mean $sim 440$ pc) with disk-related subcomponents: nuclear rings, bars, and/or spiral arms. They constitute 11-59% of the galaxy stellar mass (mean PB/T = 0.33), with stellar masses $sim 7 times 10^{9}$-$9 times 10^{10} M_{odot}$. Classical-bulge components have Sersic indices of 0.9-2.2, effective radii of 25-430 pc and stellar masses of $5 times 10^{8}$-$3 times 10^{10} M_{odot}$ (usually < 10% of the galaxys stellar mass; mean B/T = 0.06). The classical bulges show rotation, but are kinematically hotter than the disky pseudobulges. Dynamical modeling of three systems indicates that velocity dispersions are isotropic in the classical bulges and equatorially biased in the disky pseudobulges. In the mass--radius and mass--stellar mass density planes, classical-bulge components follow sequences defined by ellipticals and (larger) classical bulges. Disky pseudobulges also fall on this sequence; they are more compact than similar-mass large-scale disks. Although some classical bulges are quite compact, they are distinct from nuclear star clusters in both size and mass, and coexist with nuclear clusters in at least two galaxies. Since almost all the galaxies in this study are barred, they probably also host boxy/peanut-shaped bulges (vertically thickened inner parts of bars). NGC 3368 shows evidence for such a zone outside its disky pseudobulge, making it a galaxy with all three types of bulge.
We present detailed morphological, photometric, and stellar-kinematic analyses of the central regions of two massive, early-type barred galaxies with nearly identical large-scale morphologies. Both have large, strong bars with prominent inner photome
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