BULGES OF NEARBY GALAXIES WITH SPITZER: SCALING RELATIONS IN PSEUDOBULGES AND CLASSICAL BULGES
- Department of Astronomy, The University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States)
- Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)
We investigate scaling relations of bulges using bulge-disk decompositions at 3.6 {mu}m and present bulge classifications for 173 E-Sd galaxies within 20 Mpc. Pseudobulges and classical bulges are identified using Sersic index, Hubble Space Telescope morphology, and star formation activity (traced by 8 {mu}m emission). In the near-IR pseudobulges have n{sub b} < 2 and classical bulges have n{sub b} >2, as found in the optical. Sersic index and morphology are essentially equivalent properties for bulge classification purposes. We confirm, using a much more robust sample, that the Sersic index of pseudobulges is uncorrelated with other bulge structural properties, unlike for classical bulges and elliptical galaxies. Also, the half-light radius of pseudobulges is not correlated with any other bulge property. We also find a new correlation between surface brightness and pseudobulge luminosity; pseudobulges become more luminous as they become more dense. Classical bulges follow the well-known scaling relations between surface brightness, luminosity, and half-light radius that are established by elliptical galaxies. We show that those pseudobulges (as indicated by Sersic index and nuclear morphology) that have low specific star formation rates are very similar to models of galaxies in which both a pseudobulge and classical bulge exist. Therefore, pseudobulge identification that relies only on structural indicators is incomplete. Our results, especially those on scaling relations, imply that pseudobulges are very different types of objects than elliptical galaxies.
- OSTI ID:
- 21452950
- Journal Information:
- Astrophysical Journal, Vol. 716, Issue 2; Other Information: DOI: 10.1088/0004-637X/716/2/942; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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