Chandra detection of hotspot and knots of 3C 303

J. Kataoka*, P. Edwards, M. Georganopoulos, F. Takahara, S. Wagner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


We report the detection at X-rays of the radio/optical hotspot and knots of 3C 303 from a short (15 ksec) Chandra exposure in 2001 March. The X-ray morphology is similar to that of the radio/optical emission with peaks in the X-ray emission found at 5.5 inches (knot B), 9 inches (knot C) and 17 inches (hotspot) from the core of 3C 303. Despite the limited signal-to-noise ratio of the short Chandra exposure, the X-ray photon spectrum was measured for the hotspot. We construct the spectral energy distribution (SED) and find that the X-ray flux is well below the extrapolation of the radio-to-optical continuum, which we interpret as resulting from the production of X-rays via inverse Compton scattering of both synchrotron photons (SSC) and cosmic microwave background photons (EC/CMB). The magnetic field strength, region size, and the maximum energy of electrons are self-consistently determined for the hotspot to be B ≃ 4.3 μG, R ≃ 6.5 × 1021 cm, and γmax ≃ 1.4 × 107. This implies a magnetic field strength a factor of ∼30 below the equipartition value; Beq ≃ 150 μG. The origin of this large departure from equipartition is still uncertain, but the discrepancy is reduced if the plasma in the hotspot is moving with mildly relativistic speeds. Our observation of 3C 303, as well as recent Chandra detections of large scale jets and hotspots in a number of radio galaxies, confirm that particles are accelerated very efficiently in radio galaxies.

Original languageEnglish
Pages (from-to)91-97
Number of pages7
JournalAstronomy and Astrophysics
Issue number1
Publication statusPublished - 2003
Externally publishedYes


  • Galaxies: active
  • Galaxies: individual: 3C 303
  • Galaxies: jets
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Chandra detection of hotspot and knots of 3C 303'. Together they form a unique fingerprint.

Cite this