New ALMA and Fermi/LAT Observations of the Large-scale Jet of PKS 0637-752 Strengthen the Case Against the IC/CMB Model

Eileen T. Meyer, Peter Breiding, Markos Georganopoulos, Iv�n Oteo, Martin A. Zwaan, Robert Laing, Leith Godfrey, R. J. Ivison

Research output: Contribution to journalArticlepeer-review

Abstract

The Chandra X-ray observatory has discovered several dozen anomalously X-ray-bright jets associated with powerful quasars. A popular explanation for the X-ray flux from the knots in these jets is that relativistic synchrotron-emitting electrons inverse-Compton scatter cosmic microwave background (CMB) photons to X-ray energies (the IC/CMB model). This model predicts a high gamma-ray flux that should be detectable by the Fermi/Large Area Telescope (LAT) for many sources. GeV-band upper limits from Fermi/LAT for the well-known anomalous X-ray jet in PKS 0637-752 were previously shown in Meyer et al. to violate the predictions of the IC/CMB model. Previously, measurements of the jet synchrotron spectrum, important for accurately predicting the gamma-ray flux level, were lacking between radio and infrared wavelengths. Here, we present new Atacama Large Millimeter/submillimeter Array (ALMA) observations of the large-scale jet at 100, 233, and 319 GHz, which further constrain the synchrotron spectrum, supporting the previously published empirical model. We also present updated limits from the Fermi/LAT using the new "Pass 8" calibration and approximately 30% more time on source. With these deeper limits, we rule out the IC/CMB model at the 8.7σ level. Finally, we demonstrate that complete knowledge of the synchrotron SED is critical in evaluating the IC/CMB model.

Original languageEnglish
Article numberL35
JournalAstrophysical Journal Letters
Volume835
Issue number2
DOIs
Publication statusPublished - 1 Feb 2017

Keywords

  • galaxies: active
  • galaxies: jets
  • quasars: individual (PKS 0637,752)

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