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X-Ray Jets Aneta Siemiginowska Chandra News Issue 21 Spring 2014 Published by the Chandra X-ray Center (CXC) X-ray Jets Aneta Siemiginowska The Active Galaxy 4C+29.30 Credit: X-ray: NASA/CXC/SAO/A.Siemiginowska et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA Contents X-ray Jets HETG 3 Aneta Siemiginowska 18 David Huenemoerder (for the HETG team) 10 Project Scientist’s Report 20 LETG Martin Weisskopf Jeremy Drake 11 Project Manager’s Report 23 Chandra Calibration Roger Brissenden Larry David Message of Thanks to Useful Web Addresses 12 Harvey Tananbaum 23 The Chandra Team Belinda Wilkes Appointed as CIAO 4.6 13 Director of the CXC 24 Antonella Fruscione, for the CIAO Team Of Programs and Papers: Einstein Postdoctoral Fellowship 13 Making the Chandra Connection 29 Program Sherry Winkelman & Arnold Rots Andrea Prestwich Chandra Related Meetings Cycle 14 Peer Review Results 14 and Important Dates 30 Belinda Wilkes ACIS Chandra Users’ Committee 14 Paul Plucinsky, Royce Buehler, 34 Membership List Gregg Germain, & Richard Edgar HRC CXC 2013 Science Press 15 Ralph Kraft, Hans Moritz Guenther 35 Releases (SAO), and Wolfgang Pietsch (MPE) Megan Watzke The Chandra Newsletter appears once a year and is edited by Paul J. Green, with editorial assistance and layout by Evan Tingle. We welcome contributions from readers. Comments on the newsletter, or corrections and additions to the hardcopy mailing list should be sent to: [email protected]. Spring, 2014 3 X-ray Jets many unanswered questions, including the nature of relativistic jets, jet energetics, particle content, parti- Aneta Siemiginowska cle acceleration and emission processes. Both statis- tical studies of large samples of jets across the entire The first recorded observation of an extragalac- electromagnetic spectrum and deep broad-band imag- tic jet was made almost a century ago. In 1918 He- es of individual jets are necessary to tackle some of ber Curtis, an astronomer in the Lick Observatory, these questions. published “Descriptions of 762 nebulae and clusters In the Chandra Newsletter #13 (2006) Schwartz photographed with the Crossley Reflector.” He wrote and Harris introduced the studies of X-ray jets which a note by the entry for NGC 4486 (M87): “A curious became possible with the high angular resolution X-ray straight ray lies in a gap in the nebulosity in p.a. 20 mirrors provided by Chandra. Most of the X-ray jets deg apparently connected with the nucleus by a thin remain unresolved in XMM-Newton or Suzaku obser- line of matter. The ray is brightest at its inner end, vations and Chandra is critical to all the high angular which is 11 arcsec from the nucleus.” resolution observations revealing the X-ray structures A few decades later Baade & Minkowski (1954) on sub-arcsec scales. In this letter I highlight some re- published an optical image of M87 showing 20 arcsec cent results of extragalactic jet studies with Chandra long and 2 arcsec wide jet with clear condensations and direct the readers to more detailed reviews of the along the jet. It is surprising to read their statement: field given by Harris & Krawczynski (2006), Worrall “No possibility exists at this time of forming any hy- (2009), and Pudritz et al. (2012). pothesis on the formation of the jet, the physical state of its material, and the mechanism which connects the Chandra Observations existence of the jet with the observed radio emission.” The many discoveries of X-ray jets thrilled sci- This was 1954, the era of pre-digital astrono- entists in the early days of Chandra. They included my, when image analysis was based on photographic the discovery of the PKS 0637-752 (Tavecchio et al. plates and performed by eye, with a ruler and a pen- 2000, Cellotti et al. 2001, Schwartz et al. 2000) jet cil. Only a few radio sources had been identified at in the first calibration observation designed to test the that time, quasars had yet to be discovered, and a few focus of the mirrors on orbit. The initial discoveries more decades had to lapse before the first X-ray obser- were followed by a few systematic surveys to find vations of jets. The Einstein High Resolution Imager X-ray jets and also by detailed studies of a few jets. (HRI) provided the first X-ray data of M87 jet (Fei- The X-ray jets are seen as diffuse linear and bend- gelson 1980; Schreier et al. 1982). The first jet dis- ing structures with enhancements due to knots or hot covered in X-rays was the jet of a radio galaxy Cen- spots. The jet is often located close to the strong core taurus A which was later studied in radio wavelengths emission, or embedded in the diffuse emission of a (Schreier et al. 1979). The Einstein HRI image of the host galaxy with a total length rarely exceeding ∼ 30′′. famous quasar 3C273 needed careful analyses to dis- Most X-ray jets are rather faint and their emission is cern X-rays emitted by the relativistic jet (Willingale only a small (< 3%) fraction of a strong core, the main 1981). Later on ROSAT provided a few more detec- reason why only a few jets were detected in earlier tions of jets, but only with Chandra did X-ray studies X-ray missions. Chandra opened a new window to the of large scale jets become routine. studies of relativistic extragalactic jets. During the past 15 years the Chandra X-ray Ob- Several surveys of X-ray jets have been complet- servatory has performed many observations of jets in ed to date. They differ in their selection criteria, but a variety of objects, from stellar types in our galaxy to all originated from samples of known radio jets. Sam- quasars in the high redshift universe. Understanding bruna et al. (2004) selected 17 radio jets from a list of jets might bring us closer to understanding the phys- known AGN jets. These radio jets were longer than −2 ics of accreting systems across many different scales. 3′′ and bright (S1.4GHz > 5mJy arcsec ), with at least While the observational data gathered over these past one knot located at a large distance from the nucleus. years underlined the significance of jets in the evolu- The sample of Marshall et al. (2011) contained 56 flat tion of galaxies and clusters of galaxies, there are still spectrum radio quasars compiled from VLA and ATCA 4 CXC Newsletter imaging radio surveys and selected targets based on resulting in the X-ray emission. The source of the the flux density in the extended emission and the ra- photon field could be internal to the jet (synchro- dio jet morphology. This sample was divided into two tron-self-Compton, SSC) or external to the jet. In the sub-classes: A – purely jet flux limited and B – based large scale jets associated with quasars, the Cosmic on radio morphology and biased toward one-sided and Microwave Background was considered as the likely linear structure. In both surveys the Chandra observa- primary source of the photon field (IC/CMB). tions were short (< 10 ksec), but about 60% of these Current observations indicate that synchrotron radio jets were detected in X-rays. A higher fraction emission is the primary process producing X- rays in of resolved X-ray jets, 78%, in similar Chandra ex- jets associated with low power radio galaxies classi- posures was found by Hogan et al. (2011) in a sample fied as FRI. M87 and Centaurus A are examples of of 13 blazars selected from the flux-limited MOJAVE nearby FRI galaxies where the jets were studied in sample of relativistic jets associated with quasars and great detail. Both jets exhibit a correlated morphology FR II radio galaxies. (see M87 Fig. 1). The simple “one-zone” model where Most of the survey studies focused on under- the radio and X-ray emission are produced by the same standing the X-ray emission process in large scale population of relativistic particles is supported by the extragalactic jets. The possible mechanisms include observations. However, some evolution of the electron synchrotron emission from highly relativistic particles energy spectrum along the jet is required for these two in the jet or the emission resulting from the inverse cases. Recent studies of the archival Chandra data of Compton process where such particles transfer ener- FRI jets by Harwood & Hardcastle (2012) indicate no gy to lower frequency photons (radio-IR-optical-UV) statistically significant correlations between the prop- erties of the host galaxy and the jet, but show that the luminosity of X-ray jets scales linearly with the jet radio luminosity and that the X-ray spectral slope is relat- ed to both X-ray and radio lumi- nosity of the jet. Since the X-ray emission in these jets is due to synchrotron processes, the par- ticle acceleration mechanisms could be tested, but the sample of the suitable FRI jets is still limited. Harris, Massaro and Cheung compiled a list of all X-ray jets detected with Chan- dra and made the radio and X-ray data available on the web page: http://hea-www.harvard. edu/XJET/. They (Massaro et al. 2011) used these data to de- scribe statistical properties of Fig. 1 — M87 jet in three bands, rotated to be horizontal (from Marshall et al. all the detected X-ray jet fea- (2002)). Top: VLA image at 14.435 GHz with spatial resolution ~ 0.2′′. Second tures, knots, hot spots, diffuse panel: The HST Planetary Camera image in the F814W filter from Perlman et al. (2001). Third panel: Adaptively smoothed Chandra X-ray image. Lower panel: jet emission.
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