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Advances in Astronomy
Volume 2011, Article ID 516739, 17 pages
Review Article

Overview of the Near-IR S0 Galaxy Survey (NIRS0S)

1Astronomy Division, Department of Physics, University of Oulu, 90014 Oulu, Finland
2Finnish Centre of Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
3Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487, USA
4Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
5Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain

Received 3 October 2011; Accepted 28 November 2011

Academic Editor: Valentina Klochkova

Copyright © 2011 E. Laurikainen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


An overview of the results of the near-IR S0 galaxy survey (NIRS0S) is presented. NIRS0S is a magnitude- (  mag) and inclination- (<65) limited sample of ̃200 nearby galaxies, mainly S0s, but includes also Sa and E galaxies. It uses deep -band images, typically reaching a surface brightness of 23.5 mag arcsec−2. Detailed visual and photometric classifications were made, for the first time coding also the lenses in a systematic manner. As a comparison sample, a similar sized spiral galaxy sample with similar image quality was used. Based on our analysis, the Hubble sequence was revisited: following the early idea by van den Bergh we suggested that the S0s are spread throughout the Hubble sequence in parallel tuning forks as spirals (S0a, S0b, S0c, etc.). This is evidenced by our improved bulge-to-total ( ) flux ratios in the S0s, reaching small values typical to late-type spirals. The properties of bulges and disks in S0s were found to be similar to those in spirals and, also, the masses and scale parameters of the bulges and disks to be coupled. It was estimated that the spiral bulges brighter than −20 mag in -band are massive enough to be converted into the bulges of S0s merely by star formation. Bars were found to be fairly robust both in S0s and spirals, but, inspite of that, bars might evolve significantly within the Hubble sequence.