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Date and Time of the Query: 2019-06-17 T18:36:51 PDT
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For refcode 2002AJ....123..184S:
Retrieve 44 NED objects in this reference.
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2002AJ....123..184S SPIRAL GALAXIES WITH HST/NICMOS. II. ISOPHOTAL FITS AND NUCLEAR CUSP SLOPES MARC SEIGAR Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent, Belgium; and Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 C. MARCELLA CAROLLO Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027 MASSIMO STIAVELLI Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 P. TIM DE ZEEUW Sterrewacht Leiden, Postbus 9513, NL-2300 RA Leiden, Netherlands AND HERWIG DEJONGHE Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent, Belgium Received 2001 June 5; accepted 2001 October 4 ABSTRACT We present surface brightness profiles for 56 of the 78 spiral galaxies observed in the HST/NICMOS2 F160W snapshot survey introduced in Paper I of this series, as well as surface brightness profiles for 23 objects out of the 41 that were also observed in the F110W filter. We fit these surface brightness profiles with the Nuker law of Lauer et al. and use the smooth analytical descriptions of the data to compute the average nuclear stellar cusp slopes <{gamma}> in the 0.1"-0.5" radial range. Our main result is the startling similarity between the nuclear stellar cusp slopes <{gamma}> in the near-infrared compared with those derived in the visual passband. This similarity has several implications: (1) Despite the significant local color variations that are found in the nuclear regions of spirals and that are documented in Paper I, there are typically little or no optical-NIR global color gradients, and thus no global stellar population variations, inside ~50-100 pc from the nucleus in nearby spirals. (2) The large observed range of the strength of the nuclear stellar cusps seen in the HST optical study of spiral galaxies reflects a physical difference between galaxies and is not an artifact caused by nuclear dust and/or recent star formation. (3) The dichotomy between R^1/4^ bulges, with steep nuclear stellar cusps <{gamma}> ~ 1, and exponential bulges, with shallow nuclear stellar cusps <{gamma}> < 0.3, is also not an artifact of the effects of dust or recent star formation. (4) The presence of a surrounding massive disk appears to have no effect on the rise of the stellar density distribution within the innermost hundred parsecs of the R^1/4^ spheroids. These results imply a breakdown within the family of exponential bulges of the nuclear versus global relationships that have been found for the R^1/4^ spheroids. Such a breakdown is likely to have significant implications concerning the formation of exponential bulges and their connection with the R^1/4^ spheroids. Key words: galaxies: bulges - galaxies: nuclei - galaxies: spiral - galaxies: structure
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