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X-Ray Scaling Relations of Early-type Galaxies

Babyk, Iu. V.; McNamara, B.R.; Nulsen, P.E.J.; Hogan, M.T.; Vantyghem, A.N.; Russell, H.R.; Pulido, F.A.; Edge, A.C.

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Iu. V. Babyk

B.R. McNamara

P.E.J. Nulsen

M.T. Hogan

A.N. Vantyghem

H.R. Russell

F.A. Pulido


X-ray luminosity, temperature, gas mass, total mass, and their scaling relations are derived for 94 early-type galaxies (ETGs) using archival Chandra X-ray Observatory observations. Consistent with earlier studies, the scaling relations, L X ∝ T 4.5±0.2, M ∝ T 2.4±0.2, and L X ∝ M 2.8±0.3, are significantly steeper than expected from self-similarity. This steepening indicates that their atmospheres are heated above the level expected from gravitational infall alone. Energetic feedback from nuclear black holes and supernova explosions are likely heating agents. The tight L X –T correlation for low-luminosity systems (i.e., below 1040 erg s−1) are at variance with hydrodynamical simulations, which generally predict higher temperatures for low-luminosity galaxies. We also investigate the relationship between total mass and pressure, Y X = M g × T, finding $M\propto {Y}_{X}^{0.45\pm 0.04}$. We explore the gas mass to total mass fraction in ETGs and find a range of 0.1%–1.0%. We find no correlation between the gas-to-total mass fraction with temperature or total mass. Higher stellar velocity dispersions and higher metallicities are found in hotter, brighter, and more massive atmospheres. X-ray core radii derived from β-model fitting are used to characterize the degree of core and cuspiness of hot atmospheres.


Babyk, I. V., McNamara, B., Nulsen, P., Hogan, M., Vantyghem, A., Russell, H., …Edge, A. (2018). X-Ray Scaling Relations of Early-type Galaxies. Astrophysical Journal, 857(1), Article 32.

Journal Article Type Article
Acceptance Date Feb 28, 2018
Online Publication Date Apr 10, 2018
Publication Date Apr 10, 2018
Deposit Date Apr 26, 2018
Publicly Available Date Apr 26, 2018
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 857
Issue 1
Article Number 32


Published Journal Article (2.2 Mb)

Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.

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