Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/18842
 Title: High-resolution X-ray spectroscopy and imaging of the nuclear outflow of the starburst galaxy NGC 253 Authors: Bauer, M.Pietsch, W.Trinchieri, G.Breitschwerdt, D.Ehle, M.Read, A. First Published: Jun-2007 Publisher: EDP Sciences for European Southern Observatory (ESO) Citation: Astronomy & Astrophysics, 2007, 467 (3), pp. 979-989 Abstract: Aims.Using XMM-Newton data, we have studied the nuclear outflow of the nearby starburst galaxy NGC 253 in X-rays with respect to its morphology and to spectral variations along the outflow. Methods.We analysed XMM-Newton RGS spectra, RGS brightness profiles in cross-dispersion direction, narrow-band RGS and EPIC images, and EPIC PN brightness profiles of the nuclear region and of the outflow from NGC 253. Results.We detect a diversity of emission lines along the outflow of NGC 253. This includes the He-like ions of Si, Mg, Ne, and O and their corresponding ions in the next higher ionisation state. Additionally transitions from $\ion{Fe}{xvii}$ and $\ion{Fe}{xviii}$ are prominent. The derived temperatures from line ratios along the outflow range from 0.21$\pm$0.01 to 0.79$\pm$0.06 keV, and the ratio of $\ion{Fe}{xvii}$ lines indicates a predominantly collisionally ionised plasma. Additionally, we see indications of either a recombining or an underionised plasma in the $\ion{Fe}{xvii}$ line ratio. Derived electron densities are 0.106$\pm$0.018 cm-3 for the nuclear region and 0.025$\pm$0.003 cm-3 for the outflow region closest to the centre. The RGS image in the $\ion{O}{viii}$ line energy clearly shows the morphology of an outflow extending out to ~750 pc along the southeast minor axis, while the northwest part of the outflow is not seen in $\ion{O}{viii}$ due to the heavy absorption by the galactic disc. This is the first time that the hot wind fluid has been detected directly. The limb brightening in Chandra and XMM-Newton EPIC observations is only seen in the energy range that contains the $\ion{Fe}{xvii}$ lines (550-750 eV). In all other energy ranges between 400 and 2000 eV, no clear evidence of limb brightening could be detected. DOI Link: 10.1051/0004-6361:20066340 ISSN: 0004-6361 eISSN: 1432-0746 Links: http://hdl.handle.net/2381/18842http://www.aanda.org/articles/aa/abs/2007/21/aa6340-06/aa6340-06.html Version: Publisher Version Status: Peer-reviewed Type: Journal Article Rights: Copyright © 2007 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO. Appears in Collections: Published Articles, Dept. of Physics and Astronomy

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