• DOI:10.1086/501341
• Corpus ID: 17356315

Pseudobulges in the Disk Galaxies NGC 7690 and NGC 4593

@article{Kormendy2006PseudobulgesIT,
  title={Pseudobulges in the Disk Galaxies NGC 7690 and NGC 4593},
  author={John Kormendy and Mark Edward Cornell and David L. Block and Johan H. Knapen and Emma L. Allard},
  journal={The Astrophysical Journal},
  year={2006},
  volume={642},
  pages={765-774}
}

• J. Kormendy, M. Cornell, +2 authors E. L. Allard
• Published 18 January 2006
• Physics
• The Astrophysical Journal

We present Ks-band surface photometry of NGC 7690 (Hubble type Sab) and NGC 4593 (SBb). We find that, in both galaxies, a major part of the bulge is as flat as the disk and has approximately the same color as the inner disk. In other words, the bulges of these galaxies have disklike properties. We conclude that these are examples of pseudobulges, that is, products of secular dynamical evolution. Nonaxisymmetries such as bars and oval disks transport disk gas toward the center. There star formation builds dense stellar components that look like?and often are mistaken for?merger-built bulges, but that were constructed slowly out of disk material. These pseudobulges can most easily be recognized when, as in the present galaxies, they retain disklike properties. NGC 7690 and NGC 4593 therefore contribute to the growing evidence that secular processes help to shape galaxies. NGC 4593 contains a nuclear ring of dust that is morphologically similar to nuclear rings of star formation that are seen in many barred and oval galaxies. The nuclear dust ring is connected to nearly radial dust lanes in the galaxy's bar. Such dust lanes are a signature of gas inflow. We suggest that gas is currently accumulating in the dust ring and hypothesize that the gas ring will starburst in the future. The observations of NGC 4593 therefore suggest that major starburst events that contribute to pseudobulge growth can be episodic.