2004/08/11 by John P. F. Osmond, J. P. F. Osmond, Trevor J. Ponman +1 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2004.08298.x
10 pages, 8 figures, to be published in MNRAS
arxiv created 2004/08/11 · openalex publication_date 2004/11/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present the results of a 24‐ks XMM–Newton observation of the NGC 5171 group of galaxies. NGC 5171 is unusual in that it is an X‐ray bright group (LX > 1042 erg s−1), with irregular contours which are not centred on a bright galaxy. The global spectrum is adequately described by a single‐temperature apec model with TX= 0.96 ± 0.04 keV and Z= 0.13 ± 0.02 Z⊙, in good agreement with previous ROSAT data. We find that the X‐ray contours are centred on a bright ridge of emission stretching from the brightest group galaxy to a nearby galaxy. Spectral mapping reveals this ridge to be both cool (TX≈ 1.1 keV) and metallic (Z≈ 0.4 Z⊙) in comparison to its surroundings, suggesting it is the result of a tidal interaction between the two galaxies. Optical data reveal the member galaxies to have a high velocity dispersion (σv= 494 ± 99 km s−1) and a significantly non‐Gaussian velocity distribution, suggesting that the group is in the process of merging. A region of hot gas with TX= 1.58 ± 0.36 keV is found to the west of the bright central ridge, and we interpret this as shock‐heating resulting from the merging. A further region of emission to the south‐east of the bright central ridge, with TX= 1.14 ± 0.13 keV, is probably associated with a background group, four times more distant.