Open AccessCorrelations of near‐infrared, optical and X‐ray luminosity for early‐type galaxies
Author(s) -
Ellis S. C.,
O'Sullivan Ewan
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09982.x
Subject(s) - physics , astrophysics , luminosity , galaxy , surface brightness , luminous infrared galaxy , star formation , infrared , astronomy , stellar mass
The relation between X‐ray luminosity and near‐infrared (NIR) luminosity for early‐type galaxies has been examined. NIR luminosities should provide a superior measure of stellar mass compared to optical luminosities used in previous studies, especially if there is significant star formation or dust present in the galaxies. However, we show that the X‐ray–NIR relations are remarkably consistent with the X‐ray–optical relations. This indicates that the large scatter of the relations is dominated by scatter in the X‐ray properties of early‐type galaxies, and is consistent with early‐types consisting of old, quiescent stellar populations. We have investigated scatter in terms of environment, surface brightness profile, Mg 2 , Hβ, Hγ line strength indices, spectroscopic age and nuclear Hα emission. We found that galaxies with high Mg 2 index, low Hβ and Hγ indices or a ‘core’ profile have a large scatter in L X , whereas galaxies with low Mg 2 , high Hβ and Hγ indices or ‘power‐law’ profiles generally have L X < 10 41 erg s −1 . There is no clear trend in the scatter with environment or nuclear Hα emission.