NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-20 T22:12:37 PDT
Help | Comment | NED Home

For refcode 1997AJ....114.2366C:
Retrieve 35 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
1997AJ....114.2366C SPIRAL GALAXIES WITH WFPC2. I. NUCLEAR MORPHOLOGY, BULGES, STAR CLUSTERS, AND SURFACE BRIGHTNESS PROFILES C. M. CAROLLO Johns Hopkins University, 3701 San Martin Drive, Baltimore, Maryland 21218 Electronic mail: marci@pha.jhu.edu M. STIAVELLI Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 Electronic mail: mstiavel@stsci.edu P. T. DE ZEEUW Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands Electronic mail: tim@strw.leiden.univ.nl J. MACK Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 Electronic mail: mack@stsci.edu Received 1997 July 14; revised 1997 August 18, accepted 1997 August 20 ABSTRACT We report the analysis of HST WFPC2 F606W images of a sample of 35 spiral galaxies. We describe the optical morphological properties of the galaxies on scales of a few tens of parsecs, derive the surface brightness profiles for 18 of them, and present the results of analytical fits to these profiles. We find that: (I) Several galaxies, despite their classification as relatively early spirals, show little or no morphological evidence for a smooth, featureless (i.e., classical) bulge. Furthermore, even in the classical bulges, nuclear dust lanes are detected, similar to what is observed in early-type galaxies. (II) In several cases spiral structure reaches down to the innermost accessible scales. (III) A central, bright component is often identified. However, this does not resemble a classical bulge but has instead a highly irregular morphology. (IV) Bright knots, very likely star forming regions, are often present within the inner galactic regions in these irregular bulges. In several other cases, nuclear star formation is observed, but it is unclear whether this is associated with a small irregular bulge or with the inner disk. (V) Resolved, central compact sources are found in 18 of the 35 galaxies, including several early-type spirals. In two objects, NGC 1483 and NGC 3259, the central source is unresolved. Within the errors and the limited statistics, the central compact source luminosity seems independent of Hubble type, but correlates with the luminosity, of the disk galaxy. (VI) The central compact sources in star forming galaxies are typically brighter, for similar radii, than those in non star forming galaxies. (VII) The brightest compact sources have properties similar to those of young star clusters in the absolute magnitude (M_V_) versus half-light radius (R_e_) plane. The faintest compact sources are bracketed, in the M_V_-R_e_ plane, between Kormendy's fit to elliptical galaxies and the correlation defined by classical R'14 bulges and Galactic globular clusters. The latter implies a roughly constant mean surface brightness within the effective radius. Therefore, the luminosity sequence of the compact sources might represent an age sequence of superluminous star clusters in the centers of disk galaxies. The widespread presence of star formation in the irregular bulges, the irregular bulges themselves, and the presence of superluminous star clusters in the nuclei of spirals, support scenarios in which a fraction of bulges forms relatively late, in dissipative accretion events driven by the disk.
Retrieve 35 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home