Correlations of near-infrared, optical and X-ray luminosity for early-type galaxies

S. C. Ellis, Ewan O'Sullivan

Research output: Contribution to journalArticleResearchpeer-review

Abstract

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, Mg2, Hβ, Hγ line strength indices, spectroscopic age and nuclear Hα emission. We found that galaxies with high Mg2 index, low Hβ and Hγ indices or a 'core' profile have a large scatter in LX, whereas galaxies with low Mg2, high Hβ and Hγ indices or 'power-law' profiles generally have LX < 1w041 erg s-1. There is no clear trend in the scatter with environment or nuclear Hα emission.

LanguageEnglish
Pages627-645
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume367
Issue number2
DOIs
Publication statusPublished - 1 Apr 2006
Externally publishedYes

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near infrared
luminosity
galaxies
x rays
profiles
erg
power law
stellar mass
star formation
dust
brightness
index
trends

Keywords

  • Galaxies:fundamental parameters
  • Galaxies:general

Cite this

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title = "Correlations of near-infrared, optical and X-ray luminosity for early-type galaxies",
abstract = "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, Mg2, Hβ, Hγ line strength indices, spectroscopic age and nuclear Hα emission. We found that galaxies with high Mg2 index, low Hβ and Hγ indices or a 'core' profile have a large scatter in LX, whereas galaxies with low Mg2, high Hβ and Hγ indices or 'power-law' profiles generally have LX < 1w041 erg s-1. There is no clear trend in the scatter with environment or nuclear Hα emission.",
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Correlations of near-infrared, optical and X-ray luminosity for early-type galaxies. / Ellis, S. C.; O'Sullivan, Ewan.

In: Monthly Notices of the Royal Astronomical Society, Vol. 367, No. 2, 01.04.2006, p. 627-645.

Research output: Contribution to journalArticleResearchpeer-review

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