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Constraining the Physical Conditions in the Jets of γ-Ray Flaring Blazars Using Centimeter-band Polarimetry and Radiative Transfer Simulations. I. Data and Models for 0420–014, OJ 287, and 1156+295

Aller, M. F. and Hughes, P. A. and Aller, H. D. and Latimer, G. E. and Hovatta, T. (2014) Constraining the Physical Conditions in the Jets of γ-Ray Flaring Blazars Using Centimeter-band Polarimetry and Radiative Transfer Simulations. I. Data and Models for 0420–014, OJ 287, and 1156+295. Astrophysical Journal, 791 (1). Art. No. 53. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20140828-140116990

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Abstract

To investigate parsec-scale jet flow conditions during GeV γ-ray flares detected by the Fermi Large Angle Telescope, we obtained centimeter-band total flux density and linear polarization monitoring observations from 2009.5 through 2012.5 with the 26 m Michigan radio telescope for a sample of core-dominated blazars. We use these data to constrain radiative transfer simulations incorporating propagating shocks oriented at an arbitrary angle to the flow direction in order to set limits on the jet flow and shock parameters during flares temporally associated with γ-ray flares in 0420−014, OJ 287, and 1156+295; these active galactic nuclei exhibited the expected signature of shocks in the linear polarization data. Both the number of shocks comprising an individual radio outburst (3 and 4) and the range of the compression ratios of the individual shocks (0.5–0.8) are similar in all three sources; the shocks are found to be forward-moving with respect to the flow. While simulations incorporating transverse shocks provide good fits for 0420−014 and 1156+295, oblique shocks are required for modeling the OJ 287 outburst, and an unusually low value of the low-energy cutoff of the radiating particles' energy distribution is also identified. Our derived viewing angles and shock speeds are consistent with independent Very Long Baseline Array results. While a random component dominates the jet magnetic field, as evidenced by the low fractional linear polarization, to reproduce the observed spectral character requires that a significant fraction of the magnetic field energy is in an ordered axial component. Both straight and low pitch angle helical field lines are viable scenarios.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/791/1/53DOIArticle
http://iopscience.iop.org/0004-637X/791/1/53PublisherArticle
Additional Information:© 2014 The American Astronomical Society. Received 2014 February 14; accepted 2014 July 1; published 2014 July 25. We gratefully thank I. Troitskiy and S. Jorstad for sharing data for 0420−014 prior to publication. We thank the referee for comments that sharpened the presentation and improved the clarity of the paper. This research was supported in part by NASA Fermi Guest Investigator awards NNX09AU16G, NNX10AP16G, NNX11AO13G, and NNX13AP18G, and by a series of grants from the NSF, most recently AST-0607523, which made the long-term UMRAO program possible. Additional support for the operation of UMRAO was provided by the University of Michigan. T. Hovatta was supported in part by a grant from the Jenny and Antti Wihuri foundation and by the Academy of Finland project number 267324. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2009). Facilities: UMRAO - University of Michigan Radio Astronomy Observatory 26m telescope at Peach Mountain, NRAO:12m - National Radio Astronomy Observatory 12 meter telescope, Fermi - Fermi Gamma-Ray Space Telescope (formerly GLAST)
Funders:
Funding AgencyGrant Number
NASANNX09AU16G
NASANNX10AP16G
NASANNX11AO13G
NASANNX13AP18G
NSFAST-0607523
University of MichiganUNSPECIFIED
Jenny and Antti Wihuri FoundationUNSPECIFIED
Academy of Finland267324
Subject Keywords:magnetic fields; polarization; radiative transfer
Record Number:CaltechAUTHORS:20140828-140116990
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140828-140116990
Official Citation:Constraining the Physical Conditions in the Jets of γ-Ray Flaring Blazars Using Centimeter-band Polarimetry and Radiative Transfer Simulations. I. Data and Models for 0420–014, OJ 287, and 1156+295 M. F. Aller et al. 2014 ApJ 791 53
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49026
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:29 Aug 2014 21:38
Last Modified:29 Aug 2014 21:38

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