Abstract
- [*] Searching for Bulges at the Far End of the Hubble Sequence
- Boeker T., Stanek R., van der Marel R.P.
- AJ, 125, 1073-1086, 2002
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- [*]
Citations to
this paper in the ADS
We investigate the stellar disk properties of a sample of 19 nearby
spiral galaxies with low inclination and late Hubble type (Scd or
later). We combine our high-resolution HST I-band observations with
existing ground-based optical images to obtain surface brightness
profiles that cover a high dynamic range of galactic radius. Most of
these galaxies contain a nuclear star cluster, as discussed in a
separate paper. The main goal of the present work is to constrain the
properties of stellar bulges at these extremely late Hubble types. We
find that the surface brightness profiles of the latest-type spirals
are complex, with a wide range in shapes. We have sorted our sample in
a sequence, starting with ``pure'' disk galaxies (approximately 30% of
the sample). These galaxies have exponential stellar disks that extend
inwards to within a few tens of pc from the nucleus, where the light
from the nuclear cluster starts to dominate. They appear to be truly
bulge-less systems. Progressing along the sequence, the galaxies show
increasingly prominent deviations from a simple exponential disk model
on kpc scales. Traditionally, such deviations have prompted
``bulge-disk'' decompositions. Indeed, the surface brightness profiles
of these galaxies are generally well fit by adding a second
(exponential) bulge component. However, we find that most surface
brightness profiles can be fit equally well (or better) with a single
Sersic-type R^{1/n} profile over the entire radial range of the
galaxy, without requiring a separate ``bulge'' component. We warn in a
general sense against identification of bulges solely on the basis of
single-band surface brightness profiles. (abridged)
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Last modified March 16, 2003.
Roeland van der Marel,
marel@stsci.edu.
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