The jet collimation profile at high resolution in BL Lacertae

Abstract

Controversial studies on the jet collimation profile of BL Lacertae (BL Lac), the eponymous blazar of BL Lac objects class, complicate the scenario in this already puzzling class of objects. Understanding the jet geometry, in connection with the jet kinematics and the physical conditions in the surrounding medium, is fundamental to better constrain the formation, acceleration and collimation mechanisms in extragalactic jets. With the aim of investigating the jet geometry in the innermost regions of the jet of BL Lac, and solving the controversy, we explore the radio jet in this source, using high resolution millimeter-wave VLBI data. We collect 86GHz GMVA and 43GHz VLBA data to obtain stacked images that we use to infer the jet collimation profile by means of two comparable methods. We analyze the kinematics at 86GHz, and we discuss it in the context of the jet expansion. Finally we consider a possible implication of the Bondi sphere in shaping the different expanding region observed along the jet. We found that the jet in BL Lac expands with an overall conical geometry. A higher expanding rate region is observed between ~5 and 10 pc (de-projected) from the black hole. Such a region is associated with the decrease in brightness usually observed in high-frequency VLBI images of BL Lac. The jet retrieves the original jet expansion around 17 pc, where the presence of a recollimation shock is supported by both the jet profile and the 15GHz kinematics (MOJAVE survey). The change in the jet expansion profile occurring at ~5 pc could be associated with a change in the external pressure profile in correspondence of the Bondi radius (~3.3X10${}^5$$R_s$).

arXiv comment10 pages, 12 figures. Accepted for publication in Astronomy & Astrophysics

References in corpus (41)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• AGN Black Hole Masses and Bolometric Luminosities
• General Relativistic Magnetohydrodynamic Simulations of Jet Formation and Large-Scale Propagation from Black Hole Accretion Systems
• The relation between accretion rate and jet power in X-ray luminous elliptical galaxies
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• The Structure of the M87 Jet: A Transition from Parabolic to Conical Streamlines
• Simulations of Ultrarelativistic Magnetodynamic Jets from Gamma-ray Burst Engines
• Magnetic Driving of Relativistic Outflows in Active Galactic Nuclei. I. Interpretation of Parsec-Scale Accelerations
• Parsec Scale Properties of Markarian 501
• Magnetic field strength and spectral distribution of six parsec-scale active galactic nuclei jets
• Asymptotic structure of Poynting dominated jets
• MOJAVE - XIV. Shapes and opening angles of AGN jets
• The limb-brightened jet of M87 down to 7 Schwarzschild radii scale
• Inside the Bondi radius of M87
• Innermost collimation structure of the M87 jet down to ~ten Schwarzschild radii
• Jet stability and the generation of superluminal and stationary components
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. I. Imaging BL Lacertae at 21 microarcsecond resolution
• The accretion mechanism in low-power radio galaxies
• A transition from parabolic to conical shape as a common effect in nearby AGN jets
• Catching the Radio Flare in CTA 102 III. Core-Shift and Spectral Analysis
• Recollimation Shocks in Magnetized Relativistic Jets
• Significant core shift variability in parsec-scale jets of active galactic nuclei
• The stratified two-sided jet of Cygnus A. Acceleration and collimation
• A Highly Magnetized Twin-Jet Base Pinpoints a Supermassive Black Hole
• Radio observations of active galactic nuclei with mm-VLBI
• Collimation, Acceleration and Recollimation Shock in the Jet of Gamma-Ray-emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy 1H 0323+342
• Studies of the Jet in BL Lacertae I. Recollimation Shock and Moving Emission Features
• Jet collimation in NGC 315 and other nearby AGN
• Structure and flux variability in the VLBI jet of BL Lacertae during the WEBT campaigns (1995--2004)
• First 3 mm-VLBI imaging of the two-sided jet in Cygnus A. Zooming into the launching region
• New constraints on the structure and dynamics of black hole jets
• Studies of the Jet in BL Lacertae. II. Superluminal Alfvén Waves
• Asymmetric jet production in the Active Galactic Nucleus of NGC1052
• The Two-sided Jet Structures of NGC 1052 at Scales from 300 to $4\times 10^7$ Schwarzschild Radii
• The magnetic field structure in CTA 102 from high resolution mm-VLBI observations during the flaring state in 2016-2017
• Rapid Particle Acceleration due to Recollimation Shocks and Turbulent Magnetic Fields in Injected Jets with Helical Magnetic Fields
• Localizing the $\gamma$-ray emitting region in the blazar TXS 2013+370
• Studies of stationary features in jets: BL Lacertae. I. Dynamics and brightness asymmetry on sub-parsec scales

Cited by in corpus (14)

• Kinematics of Parsec-Scale Jets of Gamma-Ray Bright Blazars at 43 GHz during Ten Years of the VLBA-BU-BLAZAR Program
• X-ray Polarization of BL Lacertae in Outburst
• X-ray Polarization Observations of BL Lacertae
• Enabling Transformational ngEHT Science via the Inclusion of 86 GHz Capabilities
• Dual-high-frequency VLBI study of blazar-jet brightness-temperature gradients and collimation profiles
• ExHaLe-jet: An extended hadro-leptonic jet model for blazars. I. Code description and initial results
• A multi-frequency study of sub-parsec jets with the Event Horizon Telescope
• The microvariability and wavelength dependence of polarization degree/angle of BL Lacertae in the outburst 2020 to 2021
• MOJAVE -- XXII. Brightness temperature distributions and geometric profiles along parsec-scale AGN jets
• Double SSA Spectrum and Magnetic Field Strength of the FSRQ 3C 454.3
• Chromatic optical polarization of BL Lac: while faint and bright
• How do recollimation-induced instabilities shape the propagation of hydrodynamic relativistic jets?
• Analysis of Jet Dynamics and Collimation Characteristics of 0241+622 on Parsec Scales
• The January 2010 flare of Mrk421: Insights from a stochastic acceleration model