High-Frequency VLBI Imaging of the Jet Base of M87

By C. Ly, R. Walker, William Junor. 2007

134 citations recorded by the source corpus.

VLBA and Global VLBI observations of M87 at 43 GHz, some new and some previously published, are used to study the structural evolution of the jet with a spatial resolution of under 100 Schwarzschild radii. The images, taken between 1999 and 2004, have an angular resolution of 0.00043′′ × 0.00021′′. An edge-brightened jet structure and an indication of a large opening angle at the jet base are seen in all five epochs. In addition, a probable counterjet is seen in the latter three epochs. A 22 GHz VLBA image also confirms many of the structures seen at the higher frequency, including the counterjet. A comparison of the counterjet flux density at 22 and 43 GHz reveals that it is not free-free absorbed at these frequencies. Attempts to obtain speeds from the proper motions of jet and counterjet components indicate that these observations are undersampled. The closest pair of images gives apparent speeds of (0.25-0.40)c for the jet and 0.17c for the counterjet. These speeds should be treated as lower limits because of possible errors in associating components between epochs. If they are real, they indicate that the jet is oriented 30°-45° from the line of sight and that the component speeds along the jet are (0.3-0.5)c. Using the jet orientation derived from proper motions, the spectral index of the counterjet, and a jet-to-counterjet brightness ratio of 14.4, the inferred bulk flow is (0.6-0.7)c, which, given the considerable uncertainties in how to measure the brightness ratio, is not significantly larger than the component speed.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5355655181de2faab59c65e842573346e50c5a1a

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In Astronomy and Astrophysics

1. Y. Kovalev
2. M. Lister
3. T. Savolainen
4. A. Pushkarev
5. R. Blandford
6. E. Orlando
7. Bing Zhang
8. J. McKinney

In Nuclear and High Energy Physics

1. Y. Kovalev
2. M. Lister
3. T. Savolainen
4. A. Pushkarev
5. E. Orlando
6. R. Blandford
7. J. McKinney
8. A. Lobanov

Citations in the corpus

• Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks (2020, background): “…close to the event horizon can potentially explain Very Long Baseline Interferometry (VLBI) observations of the black hole at the center of the galaxy M87 which clearly show a limb-brightened jet down to 7rg (Ly et al. 2007; Kovalev et al. 2007; Hada et al. 2016; Kim et al. 2016; Kim et al. 2018).”
• MOJAVE. X. PARSEC-SCALE JET ORIENTATION VARIATIONS AND SUPERLUMINAL MOTION IN ACTIVE GALACTIC NUCLEI (2013, background): “Ly et al. (2007) found speeds of 0.25 to 0.4c in the region 2-4 mas downstream from the core, based on five VLBIepochs at 22 and 43 GHz obtained between 1999 and 2004.”
• Stability of relativistic jets from rotating, accreting black holes via fully three-dimensional magnetohydrodynamic simulations (2008, background): “M87’s jet structure hasbeen observed down to tens of gravitational radii of the putativeblack hole (BH) (e.g. Junor et al. 1999; Kovalev et al. 2007; Ly et al. 2007) with impressive animations created (Walker et al. 2008).”
• FERMI LARGE AREA TELESCOPE GAMMA-RAY DETECTION OF THE RADIO GALAXY M87 (2009, methodology): “…one-zone synchrotron self-Compton (SSC) jet model (Finke et al. 2008) assuming an angle to the line of sight,θ=10◦, and bulk Lorentz factor,Γb = 2.3 (Doppler factor,δ = 3.9), consistent with observations of apparent motions of>∼ 0.4c (Γb > 1.1) in the parsec-scale radio jet (Ly et al. 2007).”
• Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii (2016, background): “While Kovalev et al. (2007) could not identify any fast component, Ly et al. (2007) reported possible features with speeds between 0.25 c and 0.4 c at a distance of 3 mas from the core, with the detection obtained from only 2 epochs.”
• Superluminal Radio Features in the M87 Jet and the Site of Flaring TeV Gamma-Ray Emission (2007, background): “For example, the innermost (sub-pc scale) jet region is characterized by only small-amplitude optical/X-ray variability (Harris et al. 2006) and only mildly relativistic radio features (Ly et al. 2007).”