2001/10/03 by H. Xu, S. M. Kahn, J. R. Peterson +6 · 177 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Grating #Interstellar medium #Reflection (computer programming) #Spectral line #Spectral resolution #Spectrometer #astro-ph
paper · pdf · doi:10.1086/342828
published in The Astrophysical Journal 579(2), 600-606 (IOP Publishing) · 8 pages, 2 figures; submitted to ApJ
arxiv created 2001/10/03 · openalex publication_date 2002/11/04 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/08
We present the first high spectral resolution X-ray observation of the giant elliptical galaxy NGC 4636, obtained with the reflection grating spectrometer on board the XMM-Newton Observatory . The resulting spectrum contains a wealth of emission lines from various charge states of oxygen, neon, magnesium, and iron. Examination of the cross-dispersion profiles of several of these lines provides clear, unambiguous evidence of resonance scattering by the highest oscillator strength lines, as well as a weak temperature gradient in the inner regions of the interstellar medium. We invoke a sophisticated new Monte Carlo technique that allows us to properly account for these effects in performing quantitative fits to the spectrum. Our spectral fits are not subject to many of the systematics that have plagued earlier investigations. The derived metal abundances are higher than have usually been inferred from prior, lower spectral resolution observations of this source, but are still incompatible with conventional chemical-enrichment models of elliptical galaxies. In addition, our data are incompatible with standard cooling-flow models for this system; our derived upper limit to the mass deposition rate is below the predicted value by a factor of 3-5.