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Date and Time of the Query: 2019-03-19 T17:59:21 PDT
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For refcode 2013A&A...555L...4C:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2013A&A...555L...4C Inner rings in disc galaxies: dead or alive Comeron, S. Abstract. In this Letter, I distinguish "passive" inner rings as those with no current star formation as distinct from "active" inner rings that have undergone recent star formation. I built a sample of nearby galaxies with inner rings observed in the near- and mid-infrared from the NIRS0S and the S^4^G surveys. I used archival far-ultraviolet (FUV) and Halpha imaging of 319 galaxies to diagnose whether their inner rings are passive or active. I found that passive rings are found only in early-type disc galaxies (-3 <= T <= 2). In this range of stages, 21 +/- 3% and 28 +/- 5% of the rings are passive according to the FUV and Halpha indicators, respectively. A ring that is passive according to the FUV is always passive according to Halpha, but the reverse is not always true. Ring-lenses form 30-40% of passive rings, which is four times more than the fraction of ring-lenses found in active rings in the stage range - 3 <= T <= 2. This is consistent with both a resonance and a manifold origin for the rings because both models predict purely stellar rings to be wider than their star-forming counterparts. In the case of resonance rings, the widening may be at least partly due to the dissolution of rings. If most inner rings have a resonance origin, I estimate 200 Myr to be a lower bound for their dissolution time-scale. This time-scale is of the order of one orbital period at the radius of inner rings. Appendix A is available in electronic form at http://www.aanda.orgTable A.1 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/L4 Key words: galaxies: evolution, galaxies: kinematics and dynamics, galaxies: spiral, galaxies: statistics
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