1997/12/01 by William G. Mathews, Fabrizio Brighenti · 21 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Correlation #Dimensionless quantity #Dispersion (optics) #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Mass-to-light ratio #Optical depth #astro-ph
paper · pdf · doi:10.1086/311126
published in The Astrophysical Journal 493(1), L9-L12 (IOP Publishing) · 5 pages, 3 figures. Accepted for publication in Astrophysical Journal Letters
arxiv created 1997/12/01 · openalex publication_date 1998/01/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Optical parameters of elliptical galaxies are tightly correlated, but their X-ray parameters vary widely. The X-ray luminosity L X ranges over more than 1 order of magnitude for ellipticals having similar optical luminosity L B . The source of this scatter has been elusive. We show here that the dispersion in L X for fixed optical luminosity L B correlates strongly with the dimensionless ratio of the sizes of the X-ray and optical images, r e X / r e . A distance-independent variant of this correlation is L X / L B ∝ ( r e X / r e ) 0.60±0.30 . This correlation may be a natural result of mergings and tidal truncations that occurred during the early formation of ellipticals in groups of galaxies. The shapes of the X-ray images also vary: some are compact (e.g., NGC 4649, 7626, 5044), others diffuse (e.g., NGC 4636, 1399).