DETECTING RELATIVISTIC X-RAY JETS IN HIGH-REDSHIFT QUASARS
- Department of Statistics, Harvard University, Cambridge, MA 02138 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)
- Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244, Kraków (Poland)
- Department of Statistics, The Wharton School, University of Pennsylvania, 400 Jon M. Huntsman Hall, 3730 Walnut Street, Philadelphia, PA 19104-6340 (United States)
- Statistics Section, Imperial College London, Huxley Building, South Kensington Campus, London SW7 (United Kingdom)
- Department of Physics, MS 057, Brandeis University, Waltham, MA 02454 (United States)
- CRESST and Astroparticle Physics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States)
- INAF Osservatorio Astronomico di Brera, via Brera 28, I-20124, Milano (Italy)
We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift ( z ≥ 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 < z < 2.9) quasars. The data set includes four sources with integrated steep radio spectra and seven with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet, and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p -value upper bounds on the significance that an X-ray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional six marginally. We also find residual emission in the cores of three quasars and in the background of one quasar that suggest the existence of unresolved X-ray jets. The dependence of the X-ray to radio luminosity ratio on redshift is a potential diagnostic of the emission mechanism, since the inverse Compton scattering of cosmic microwave background photons (IC/CMB) is thought to be redshift dependent, whereas in synchrotron models no clear redshift dependence is expected. We find that the high-redshift jets have X-ray to radio flux ratios that are marginally inconsistent with those from lower redshifts, suggesting that either the X-ray emissions are due to the IC/CMB rather than the synchrotron process, or that high-redshift jets are qualitatively different.
- OSTI ID:
- 22660915
- Journal Information:
- Astrophysical Journal, Vol. 833, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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