2006/09/30 by Mariangela Bernardi, M. Bernardi · 4 citations
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Space Technology and Applications #astro-ph
paper · pdf · doi:10.1086/512611
published as Astron.J.133:1954-1961,2007 · 9 pages, 9 figures. Accepted by AJ. A new appendix describes systematics effects we found in the SDSS velocity dispersion measurements (sigmas < 150 km/s are biased towards larger values; this bias was not present in the Bernardi et al. 2003 sample) and luminosity measurements
arxiv created 2007/01/03 · openalex publication_date 2007/03/22 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/31
Early-type galaxy velocity dispersions and luminosities are correlated. The correlation estimated in local samples (≤100 Mpc) differs from that measured more recently in the Sloan Digital Sky Survey (SDSS). This is true even when systematics in the SDSS photometric and spectroscopic parameters have been accounted for. We show that this is also true for the Nearby Early-Type Galaxies (ENEAR) sample if galaxy luminosities are estimated using distances that have been corrected for peculiar motions. We then show that, because the estimate of the "true" distance is derived from a correlation with velocity dispersion, in this case the D n -σ relation, using it in the σ- L relation leads to an artificially tight relation with a biased slope. Making no correction for peculiar velocities results in a σ- L relation that is very similar to that of the SDSS, although with larger scatter. We also measure the σ- L correlation in a mock ENEAR catalog, in which the underlying galaxy sample has the same σ- L correlation as seen in the SDSS. The mock catalog produces the same D n -σ relation as the data, the same biased slope when D n -σ distances are used to estimate luminosities, and good agreement with the input σ- L relation when redshift is used as the distance indicator. This provides further evidence that the true σ- L relation of ENEAR galaxies is indeed very similar to that of SDSS early types. Our results suggest that the local σ- L relations based on fundamental plane distances should also be reevaluated. Our findings also have important implications for black hole demographics; the best direct estimates of the masses of supermassive black holes come from local galaxies, so estimates of the black hole mass function are more safely made by working with the M • -σ correlation than with the M • - L correlation.