Constraints on the location of $\gamma$-ray emitting region for a sample of blazars with radio core-shift measurements

Abstract

We model simultaneous or quasi-simultaneous multi-band spectral energy distributions (SEDs) for a sample of 25 blazars that have radio core-shift measurements, where a one-zone leptonic model and Markov chain Monte Carlo technique are adopted. In the SED fitting for 23 low-synchrotron-peaked (LSP) blazars, the seed photons from broad line region (BLR) and molecular torus are considered respectively in the external Compton process. We find that the SED fitting with the seed photons from the torus are better than those utilizing BLR photons, which suggests that the $\gamma$-ray emitting region may be located outside the BLR. Assuming the magnetic field strength in the $\gamma$-ray emitting region as constrained from the SED fitting follows the magnetic field distribution as derived from the radio core-shift measurements (i.e., $B(R)\simeq B_{1pc}(R/1pc{)}^{-1}$, $R$ is the distance from the central engine and $B_{1pc}$ is the magnetic field strength at 1 pc), we further calculate the location of the $\gamma$-ray emitting region, $R_{\gamma }$, for these blazars. We find that $R_{\gamma }\sim 2\times 10^4{R}_{\mathrm{S}}\simeq 10R_{\mathrm{BLR}}$ ($R_{\mathrm{S}}$ is the Schwarzschild radius and $R_{\mathrm{BLR}}$ is the BLR size), where $R_{\mathrm{BLR}}$ is estimated from the broad line luminosities using the empirical correlations obtained using the reverberation mapping methods.

20 pages, 10 Figures, ApJ, in press

References in corpus (21)

• Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
• Modeling the Emission Processes in Blazars
• The blazar sequence: a new perspective
• GeV breaks in blazars as a result of gamma-ray absorption within the broad-line region
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• The Spectral Energy Distributions of Fermi Blazars
• Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
• Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission
• Fermi/LAT broad emission line blazars
• Results of WEBT, VLBA and RXTE monitoring of 3C 279 during 2006-2007
• Radio/gamma-ray time delay in the parsec-scale cores of active galactic nuclei
• Constraints on minimum electron Lorentz factor and matter content of jets for a sample of bright Fermi blazars
• Ruling out IC/CMB X-rays in PKS 0637-752 and the Implications for TeV Emission from Large-Scale Quasar Jets
• Temporal Correlations Between Optical and Gamma-ray Activity in Blazars
• Intrinsic absorption in 3C 279 at GeV-TeV energies and consequences for estimates of the EBL
• Intrinsic Correlations for Flaring Blazars Detected by Fermi
• Discerning the $\gamma$-ray emitting region in the flat spectrum radio quasars
• Test of the Formation mechanism of the Broad Line Region in Active Galactic Nuclei
• A test on external Compton models for $\gamma$-ray active galactic nuclei
• Multi-wavelength Temporal Variability of the Blazar 3C 454.3 during 2014 Activity Phase
• Testing one-zone synchrotron-self-Compton models with spectral energy distributions of Mrk 421

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