Multiwavelength Imaging of Kiloparsec-scale Jets

The Multiwavelength Jet Team is led by Prof. Rita Sambruna at GMU, and includes graduate student Jessica (Reitz) Gambill, who is working on this project as part of her PhD Thesis. Using multiwavelength observations taken with ground as well as space-based observatories, we aim at addressing fundamental questions about the energetic and physical properties of extragalactic jets in Active Galactic Nuclei (AGN): How common is X-ray and optical emission from jets? By which mechanism(s) do jets shine at these wavelengths? What are the most important physical parameters governing jet phenomenology? and how does all this relate to the ultimate question - the origin of relativistic jets?

We are using NASA's Chandra and HST to perform a large survey of 17 radio jets at X-rays and optical wavelengths. The targets were selected from a radio sample, and they were not known X-ray and/or optical emitters at the time of our survey. Thus, our survey represents a truly unbiased search for the X-ray and optical counterparts of radio jets. We are discovering that X-ray and optical emission from the kiloparsec scales of radio jets is very common, with complex and widely different morphologies from jet to jet and at given wavelengths. An example of four newly detected X-ray jets is shown above (Sambruna et al. 2001). Our new X-ray detections imply the presence of relativistic bulk motion on very large scales, at tens to hundreds of kpc from the central black hole, setting new challenges for theoretical models. X-ray emission is produced in localized regions, likely shocks associated with the deceleration of the jet. Furthermore, our data show that different emission processes for the X-rays may dominate in the same jet at different locations, depending on the local physical conditions.

In addition, we are also studying the X-ray properties of the cores of the radio-loud quasars hosting the jets. Our results show that the X-ray spectra of the cores can be described generally by simple power law models with photon indices around 1.5, flatter than for radio-quiet quasars. We also discovered Fe Kalpha emission lines in two sources and excess absorption in a high-z quasar (Gambill et al. 2002).

This work is supported by NFS' CAREER award and several Chandra and HST grants from NASA.

Recent Publications of the Group:

• Sambruna, R.M. et al. 2001, "A survey of extended radio jets in AGN with Chandra and HST: First Results" , ApJ, 571, 206
  
• Pesce, J.E., Sambruna, R.M., et al. 2001, "Detection of an X-ray Jet in 3C371 with Chandra", ApJ, 556, L79
  
• Sambruna, R.M. et al. 2001, "Chandra Observations of the X-ray Jet of 3C273", ApJ, 549, L161
  
• Tavecchio, F. et al. 2000, "The X-Ray Jet of PKS 0637-752: Inverse Compton Radiation from the Cosmic Microwave Background?", ApJ, 544, L23