The off-axis jet structure in Mrk 501 at mm-wavelengths

TL;DR

This study uses high-frequency VLBA and GMVA observations to reveal complex off-axis structures and spectral properties in the jet of Mrk 501, providing new insights into its jet morphology at millimeter wavelengths.

Contribution

It reports the first detection of an off-axis feature northeast of the core and analyzes spectral indices, advancing understanding of jet structure in TeV blazars.

Findings

Detection of a northeast off-axis feature at 43 GHz.

Identification of a jet feature at 86 GHz consistent with previous results.

Spectral index analysis shows diverse emission properties.

Abstract

We present results from 43 GHz (VLBA, six epochs from 2012.2 to 2013.2) and 86 GHz (GMVA, one epoch in 2012.4) observations toward the basis of the jet in the TeV Blazar Mrk 501. The 43-GHz data analysis reveals a new feature located northeast of the radio core, with a flux density of several tens of mJy, perpendicularly to the jet axis. The 86-GHz image shows the jet feature located 0.75 mas southeast of the radio core, which is consistent with the previous result. The location of Gaussian model for 0.75 mas feature does not coincide with those for the jets in the 43-GHz image, however, a distribution of emission is found. We also discuss the spectral indices of the core, the northeast feature, and the jet feature between 43 GHz and 86 GHz, which show flat-to-steep, steep, and flat-to-invert, respectively.