X-ray luminosity function of clusters of galaxies: Predictions from a thermal bremsstrahlung model

Journal Article · Sat Sep 01 04:00:00 EDT 1979 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/183041· OSTI ID:5894392

Bahcall, N A

The X-ray luminosity function (LF) of clusters of galaxies is calculated, using the general LF of optical clusters recently determined by Bahcall and a relation between X-ray and optical luminosity based on a thermal bremsstrahlung model. The derived X-ray LF applies to clusters whose X-ray emission is mostly due to thermal bremsstrahlung from a smooth, hot intracluster gas. The main features predicted by the LF are a change of slope in the (log eta/sub x/, log L/sub x/) -plane at L/sub x/approx.10/sup 44/ ergs s/sup -1/, a moderately steep slope of approx.-2.5 at high luminosities (approx.10/sup 44/--10/sup 46/ ergs s/sup -1/), and a flatter slope of approx.-1.3 below 10/sup 44/ ergs s/sup -1/ (down to approx.10/sup 42/ or 10/sup 43/ ergs s/sup -1/, where the smooth thermal bremsstrahlung may not dominate the total X-ray emission). Simple analytic expressions of the LF are given for various X-ray energy bands. X-ray data from Uhuru and Ariel 5, available for the 10/sup 44/--10/sup 46/ ergs s/sup -1/ luminosity range (including upper limits in the 10/sup 45/--10/sup 46/ range), agree well with the LF calculated here. The present calculations suggest that at least to L/sub x/approx.10/sup 46/ ergs s/sup -1/ the X-ray LF does not decay faster than approx.L/sub x//sup -2.5/ (for a wide enough energy band). It is also suggested that fewer faint X-ray clusters than previously expected may exist (and be detected by the Einstein satellite).

• Research Organization: Princeton University Observatory
• OSTI ID: 5894392
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 232:2; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BREMSSTRAHLUNG
COSMIC GASES
ELECTROMAGNETIC RADIATION
FLUIDS
GALAXY CLUSTERS
GASES
IONIZING RADIATIONS
LUMINOSITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SATELLITES
X RADIATION