Kinematics of Gas and Stars Along the Hubble Sequence |
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Authors: | JC Vega Beltrán E Pignatelli WW Zeilinger A Pizzella EM Corsini F Bertola JE Beckman |
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Institution: | 1. vicolo dell'Osservatorio 5, Osservatorio Astronomico di Padova, I 35122, Padova, Italy 2. Institut für Astronomie, Universit?t Wien, Wien, Austria 3. European Southern Observatory, Lasilla, 19001, Santiago 19, Chile 4. Dipartimento di Astronomia, Universitàdi Padova, vicolo dell'Osservatorio 5, I-35122, Padova, Italy; E-mail 5. Instituto de Astrofí sica de Canarias, La Laguna, Spain
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Abstract: | We present a comparison between the ionized gas and stellar kinematics for a sample of five early-to-intermediate disc galaxies.
We measured the major axis V and σ radial profiles for both gas and stars, and the h
3 and h
4 radial profiles of the stars. We also derived from the R-band surface photometry of each galaxy the light contribution of their bulges and discs. In order to investigate the differences
between the velocity fields of the sample galaxies we adopted the self-consistent dynamical model by Pignatelli and Galletta
(1999), which takes into account the asymmetric drift effects, the projection effects along the line of sight and the non-Gaussian
shape of the line profiles due to the presence of different components with distinct dynamical behaviour. We find for the
stellar component a sizeable asymmetric drift effect in the inner regions of all the sample galaxies, as results from comparing
their stellar rotation curves with the circular velocity predicted by the models. The galaxy sample is not wide enough to
draw general conclusions. However, we have found a possible correlation between the presence of slowly rising gas rotation
curves and the ratio of the bulge/disc half-luminosity radii, while there is no obvious correlation with the key parameter
represented by the morphological classification, namely the bulge/disc luminosity ratio. Systems with a diffuse, dynamically
hot component (bulge or lens) with a scale length comparable to that of the disc are characterized by slowly rising gas rotation
curves. On the other hand, in systems with a small bulge the gas follows almost circular motions, regardless of the luminosity
of the bulge itself. We noticed a similar behaviour also in the gas and stellar kinematics of the two early-type spiral galaxies
modelled by Corsini et al.(1998).
This revised version was published online in July 2006 with corrections to the Cover Date. |
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