Volume 485, Number 3, July III 2008
|Page(s)||695 - 705|
|Published online||06 May 2008|
On the morphology of sigma-drop galaxies*
Instituto de Astrofísica de Canarias, 38200 La Laguna, Spain e-mail: firstname.lastname@example.org
2 Consejo Superior de Investigaciones Científicas, Spain
Accepted: 28 April 2008
Context. Local reductions of the stellar velocity dispersion in the central regions of galaxies are known as sigma-drops (σ-drops). Knowing the origin of these features can lead to better understanding of inner galactic dynamics.
Aims. We present a sample of 20 σ-drop galaxies matched with a control sample of galaxies without σ-drop in order to search for correlations between σ-drops and the properties, primarily morphological, of the nuclear zones and discs of their host galaxies.
Methods. We study the dust and Hα distribution at 0.1 arcsec scale, using Hubble Space Telescope imaging, in the circumnuclear zones of the two samples of galaxies, searching for differences and trying to establish a link between the nuclear kinematics and the host morphology. We have also considered the CO and H i emission of the galaxies and their luminosity profiles.
Results. We classify the two samples following both morphological parameters and the luminosity profiles. We find a larger fraction of nuclear dust spirals and Hα rings in the σ-drop sample. We also find that the fraction of Seyfert galaxies in the σ-drop sample is bigger than that of LINERs and that the reverse is true for the control sample.
Conclusions. Our findings are evidence that a σ-drop is very probably due to inflow-induced star formation in a dynamically cool disc, or in a gas ring, shock focused by an inner Lindblad resonance above a certain critical density level. The same mechanism that feeds the nuclear ring or the nuclear disc is probably reponsible for the higher rate of Seyfert galaxies among the σ-drop hosts.
Key words: Galaxy: kinematics and dynamics / galaxies: nuclei / galaxies: statistics
© ESO, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.