Decelerating Flows in TeV Blazars: A Resolution to the BL Lacertae-FR I Unification Problem

By M. Georganopoulos, Demosthenes Kazanas. 2003

194 citations recorded by the source corpus.

TeV emission from BL Lacertae (BL) objects is commonly modeled as synchrotron self-Compton radiation from relativistically moving homogeneous plasma blobs. In the context of these models, the blob Lorentz factors needed to reproduce the TeV emission corrected for absorption by the diffuse infrared background are large (δ ≳ 50). The main reason for this is that stronger beaming eases the problem of the lack of ~IR-UV synchrotron seed photons needed to produce the deabsorbed ~few TeV peak of the spectral energy distribution. However, such high Doppler factors are in strong disagreement with the unified scheme, according to which BLs are FR I radio galaxies with their jets closely aligned to the line of sight. Here, motivated by the detection of subluminal velocities in the subparsec-scale jets of the best studied TeV blazars, Mrk 421 and Mrk 501, we examine the possibility that the relativistic flows in the TeV BLs decelerate. In this case, the problem of the missing seed photons is solved because of upstream Compton scattering, a process in which the upstream energetic electrons from the fast base of the flow "see" the synchrotron seed photons produced in the slow part of the flow relativistically beamed. Modest Lorentz factors (Γ ~ 15), decelerating down to values compatible with the recent radio interferometric observations, reproduce the ~few TeV peak energy of these sources. Furthermore, such decelerating flows are shown to be in agreement with the BL-FR I unification, naturally reproducing the observed BL/FR I broadband luminosity ratios.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/20872e8c0bc29dbf096e33f9de3321bda1fdf0e9

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Citations in the corpus

FROM THE BLAZAR SEQUENCE TO THE BLAZAR ENVELOPE: REVISITING THE RELATIVISTIC JET DICHOTOMY IN RADIO-LOUD ACTIVE GALACTIC NUCLEI (2011, background): “…axisymmetric model explored by Swain et al. (1998), Chiaberge et al. (2000), and Ghisellini et al. (2005), and the decelerating model of Georganopoulos & Kazanas (2003), all of which imply a high-speed spine or base which dominates the flux when the source is aligned, and a slower…”
FERMI LARGE AREA TELESCOPE VIEW OF THE CORE OF THE RADIO GALAXY CENTAURUS A (2010, methodology): “…by a faster flow428 closer to the black hole, and the off-axis γ-rays seen in radio galaxies are produced by the slower429 flow farther out along the jet (Georganopoulos & Kazanas 2003).430 As an example, we provide a fit to the Cen A SED using this decelerating flow, as the blue431 curve in…”
Variable Very High Energy γ-Ray Emission from Markarian 501 (2007, methodology): “…the high δ’s derived from VHE data with the much lower δ’s derived from VLBI radio measurements, the jets of TeV blazars must either undergo severe deceleration (Georganopoulos & Kazanas 2003) or be structured radially as a two-velocity, inner spine plus outer layer, flow (Ghisellini et al. 2005).”
Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays (2005, methodology): “…then been used to determine intrinsic (unabsorbed) source spectra of well-observed TeV blazars which can be shown to be consistent with synchrotron self-Compton emission models (De Jager & Stecker 2002; Konopelko et al. 2003; Georganopoulos & Kazanas 2003; Konopelko, Mastichiadas & Stecker 2005).”
Rapid variability in TeV blazars: the case of PKS 2155—304 (2008, background): “Smallerδ andΓ factors are however possible in alternative models, where two or more emission regions have differentΓ, as in the decelerating jet model of Georganopoulos & Kazanas (2003) and in the “spine–layer” model proposed by Ghisellini, Tavecchio & Chiaberge (2005; hereafter G05).”
LEPTONIC AND HADRONIC MODELING OF FERMI-DETECTED BLAZARS (2013, unknown): “…of multi-zone models have been proposed, including the spine-sheath model of Tavecchio & Ghisellini (2008) or the decelerating jet model of Georganopoulos & Kazanas (2003), as well as internal shock models (e.g., Marscher & Gear 1985; Spada et al. 2001; Sokolov et al. 2004; Graff et al.…”
TeV BL Lac objects at the dawn of the Fermi era (2009, methodology): “Multizone emission models, such as those discussed in the framework of structured jet models (Georganopoulos & Kazanas 2003; Ghisellini, Tavecchio & Chiaberge 2005), could be required for the detailed modelling of the SED even at γ -ray energies (e.g. Anderhub et al. 2009).”
FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM NGC 1275 (2009, methodology): “A fit to the NGC 1275 data using the decelerating flow model of Georganopoulos and Kazanas (2003b), which was developed to overcome these problems, isalso shown in Fig.”
The power of blazar jets (2007, methodology): “And indeed models accounting for the deceleration via radiative dissipation have been proposed, by e.g. Georganopoulos & Kazanas (2003) and Ghisellini, Tavecchio& Chiaberge (2005).”
General physical properties of bright Fermi blazars (2009, background): “Moreover, thisissue of jet deceleration of BL Lac jets has been debated recently on the theoretical point of view (Georganopoulos & Kazanas 2003; Ghisellini, Tavecchio & Chiaberge 2005).”
Synchrotron Self-Compton Analysis of TeV X-Ray-Selected BL Lacertae Objects (2008, background): “These photons could originate from a slower-moving sheath surrounding a faster jet spine (Ghisellini et al. 2005; Tavecchio & Ghisellini 2008), or from an advanced portion of the jet moving at a slower speed (Georganopoulos & Kazanas 2003).”