Optical detection of the Pictor A jet and tidal tail: Evidence against an IC/CMB JET

Journal Article · Mon Jul 20 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/808/1/92· OSTI ID:22882810

Gentry, Eric S. ^[1]; Marshall, Herman L. ^[2]; Hardcastle, Martin J. ^[3]; Perlman, Eric S. ^[4]; Birkinshaw, Mark; Worrall, Diana M. ^[5]; Lenc, Emil ^[6]; Siemiginowska, Aneta ^[7]

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1. Department of Astronomy and Astrophysics, University of California at Santa Cruz, 1156 High St., Santa Cruz, CA, 95064 (United States)
2. Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States)
3. School of Physics, Astronomy, and Mathematics, University of Hertfordshire, College Lane, Hatfield, Hertfordshire UK AL10 9AB (United Kingdom)
4. Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL, 32901 (United States)
5. Department of Physics, University of Bristol, Tyndall Ave., Bristol BS8 1TL (United Kingdom)
6. Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia)
7. Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

New images of the FR II radio galaxy Pictor A from the Hubble Space Telescope reveal a previously undiscovered tidal tail, as well as a number of jet knots coinciding with a known X-ray and radio jet. The tidal tail is approximately 5″ wide (3 kpc projected), starting 18″ (12 kpc) from the center of Pictor A, and extends more than 90″ (60 kpc). The knots are part of a jet observed to be about 4′ (160 kpc) long, extending to a bright hotspot. These images are the first optical detections of this jet, and by extracting knot flux densities through three filters, we set constraints on emission models. While the radio and optical flux densities are usually explained by synchrotron emission, there are several emission mechanisms that might be used to explain the X-ray flux densities. Our data rule out Doppler-boosted inverse Compton scattering as a source of the high-energy emission. Instead, we find that the observed emission can be well described by synchrotron emission from electrons with a low-energy index (p∼2) that dominates the radio band, while a high-energy index (p∼3) is needed for the X-ray band and the transition occurs in the optical/infrared band. This model is consistent with a continuous electron injection scenario.

• OSTI ID: 22882810
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 808; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COMPTON EFFECT
DETECTION
ELECTRONS
EMISSION
FLUX DENSITY
RADIO GALAXIES
SPACE
SYNCHROTRON RADIATION
TELESCOPES
X-RAY GALAXIES