Kenneth Pounds#


Ken Pounds is one of the pioneers of Space Science in the UK, playing a key role in establishing the international status of the Leicester X-ray Astronomy Group since 1960, serving as President of the Royal Astronomical Society in 1991-92 and as the first Chief Executive of the Particle Physics and Astronomy Research Council in 1994-98. Since returning to the University he has resumed an active interest in the physics of Active Galaxies, playing a leading role over the past decade in establishing the existence of powerful ionised winds ejected from close to the nuclear super-massive black hole, with the potential to control the growth of the host galaxy. Professor Pounds' career in space science has been recognised by the RAS Gold Medal, the COSPAR Space Science award, and the Planetary Award of the Association of Space Explorers. He has also received honorary degrees from the universities of York, Loughborough, Sheffield-Hallam, Warwick and Leicester, and is an Honorary Fellow of UCL and Leicester.


One of the most important new results emerging over the past decade from X-ray observations of AGN is the evidence for sub-relativistic outflows of highly-ionised gas, apparently carrying sufficient mechanical energy to disrupt star formation in the host galaxy. The prototype of these luminous AGN is the narrow line Seyfert galaxy PG1211+143, for which a short XMM-Newton observation in 2001 provided the first evidence for a highly- ionised outflow in a non-BAL AGN, with a velocity of ~0.09c (Pounds et al. 2003, MNRAS, 346, 1025). Although a much lower velocity was claimed from a separate analysis, principally based on the relatively low signal-to-noise RGS data (Kaspi & Behar 2006, ApJ, 636, 674), the high velocity was supported - and refined to 0.14±0.01c - in a re-analysis of the 2001 data, making use of the higher energy resolution of the MOS cameras (Pounds & Page 2006, MNRAS, 372, 1275).

Further short observations with XMM-Newton (in 2004 and 2007), Chandra and Suzaku have shown the high velocity outflow to be persistent, but of variable strength (e.g. Reeves et al. 2008, MNRAS, 385, 108), while confirmation that the highly-ionised wind in PG 1211 + 143 is massive and energetic was obtained by interpretation of PCygni and other broad emission features from stacking of the 2001, 2004 and 2007 EPIC spectra (Pounds & Reeves 2007, MNRAS, 374, 823; Pounds & Reeves 2009, MNRAS,397,249).

More recently, the examination of archival data from XMM-Newton has shown similar ultra-fast highly-ionised outflows (now named UFOs) to be surprisingly common in nearby, bright type-1 AGN (Tombesi et al. 2010, A&A, 521, 57; Tombesi et al. 2011, ApJ, 742, 44; Tombesi et al. 2012, MNRAS, 422, 1), a finding supported by a similar analysis ofthe Suzaku archive (Gofford et al. 2013, MNRAS, 430,60).

The frequency of UFO detections confirms a typically large covering factor and hence significant mass and kinetic energy in such winds. Indeed, their mechanical energy may be an order of magnitude greater than required to disrupt the bulge gas in the host galaxy, suggesting much of the flow energy is lost before reaching the star forming region in galaxies that are still growing. In that context, King (2010a, MNRAS, 402, 1516) has argued that the outflows in such galaxies, lying below M-sigma, must be momentum-driven, while the first evidence for a fast wind shocking with the ISM or slower moving ejecta, with much of the mechanical energy being lost, has recently been found in an extended XMM-Newton study of the narrow-line Seyfert 1 NGC4051 (Pounds & Vaughan 2011, MNRAS, 413, 1251; Pounds & King 2013, MNRAS, 433, 1369).

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