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Date and Time of the Query: 2019-03-19 T19:16:58 PDT
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For refcode 2009ApJ...696..411W:
Retrieve 143 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2009ApJ...696..411W Bulge n and B/T in High-Mass Galaxies: Constraints on the Origin of Bulges in Hierarchical Models Weinzirl, Tim; Jogee, Shardha; Khochfar, Sadegh; Burkert, Andreas; Kormendy, John Abstract. We use the bulge Sersic index n and bulge-to-total mass ratio (B/T) to explore the fundamental question of how bulges form. We perform two-dimensional bulge-disk-bar decomposition on H-band images of 143 bright, high-mass (M_sstarf_ >= 1.0 x 10^10^ M_sun_) low-to-moderately inclined (i < 70^degree^) spirals. Our results are as follows. (1) Our H-band bar fraction (~58%) is consistent with that from ellipse fits. (2) 70% of the stellar mass is in disks, 10% in bars, and 20% in bulges. (3) A large fraction (~69%) of bright spirals have B/T<= 0.2, and ~76% have low n <= 2 bulges. These bulges exist in barred and unbarred galaxies across a wide range of Hubble types. (4) About 65% (68%) of bright spirals with n <= 2 (B/T <= 0.2) bulges host bars, suggesting a possible link between bars and bulges. (5) We compare the results with predictions from a set of {LAMBDA}CDM models. In the models, a high-mass spiral can have a bulge with a present-day low B/T<= 0.2 only if it did not undergo a major merger since z <= 2. The predicted fraction (~ 1.6%) of high-mass spirals, which have undergone a major merger since z <= 4 and host a bulge with a present-day low B/T <= 0.2, is a factor of over 30 smaller than the observed fraction (~66%) of high-mass spirals with B/T <= 0.2. Thus, contrary to common perception, bulges built via major mergers since z <= 4 seriously fail to account for the bulges present in ~66% of high mass spirals. Most of these present-day low B/T <= 0.2 bulges are likely to have been built by a combination of minor mergers and/or secular processes since z <= 4. Key words: galaxies: bulges, galaxies: evolution, galaxies: formation, galaxies: fundamental parameters, galaxies: interactions, galaxies: structure
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