Volume 367, Number 2, February IV 2001
|Page(s)||428 - 442|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 February 2001|
Growth of galactic bulges by mergers
I. Dense satellites
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Canary Islands, Spain
2 Astronomisches Institut der Universitat Basel, 4102 Binningen, Switzerland
3 School of Physics and Astronomy, University of Nottingham, NG7 2RD, UK e-mail: email@example.com; firstname.lastname@example.org; Reynier.Peletier@nottingham.ac.uk
Corresponding author: J. A. L. Aguerri, email@example.com
Accepted: 1 December 2000
Andredakis et al. ([CITE]) fit Sersic's law to the bulges of the Balcells & Peletier ([CITE]) galaxy sample, and infer that n drops with morphological type T from 4-6 for S0 to (exponential) for Sc's. We use collisionless N body simulations to test the assumption that initially the surface brightness profiles of all bulges were exponential, and that the steepening of the profiles toward the early-types is due to satellite accretion. The results are positive. After the accretion of a satellite, bulge-disk fits show that the bulge grows and that the bulge profile index n increases proportional to the satellite mass. For a satellite as massive as the bulge, n rises from 1 to 4. We present kinematic diagnostics on the remnants and disk thickening. The latter suggests that the bulge growth must have occurred before the last formation of a thin disk in the galaxy. The thick disks created by the merger are reminiscent of thick disks seen in early-type edge-on galaxies. The efficiency of the process suggests that present day bulges of late-type spirals showing exponential profiles cannot have grown significantly by collisionless mergers.
Key words: galaxies: evolution / galaxies: interactions / galaxies: kinematics and dynamics / galaxies: nuclei / galaxies: spiral / galaxies: structure
© ESO, 2001
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