J/A+A/690/A129 M87 VLBA 43GHz images (Kim+, 2024)
Bayesian self-calibration and imaging in very long baseline interferometry.
Kim J.-S., Nikonov A.S., Roth J., Ensslin T.A., Janssen M., Arras P.,
Mueller H., Lobanov A.P.
<Astron. Astrophys. 690, A129 (2024)>
=2024A&A...690A.129K 2024A&A...690A.129K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Interferometry ; Polarization ; Radio sources
Keywords: methods: statistical - techniques: high angular resolution -
techniques: image processing - techniques: interferometric -
galaxies: active - galaxies: individual: M87
Abstract:
Self-calibration methods with the CLEAN algorithm have been widely
employed in Very Long Baseline Interferometry (VLBI) data processing
in order to correct antenna-based amplitude and phase corruptions
present in the data. However, human interaction during the
conventional CLEAN self-calibration process can impose a strong
effective prior, which in turn may produce artifacts within the final
image and hinder the reproducibility of final results.
In this work, we aim to demonstrate a combined self-calibration and
imaging method for VLBI data in a Bayesian inference framework. The
method corrects for amplitude and phase gains for each antenna and
polarization mode by inferring the temporal correlation of the gain
solutions.
We use Stokes I data of M87 taken with the Very Long Baseline Array
(VLBA) at 43 GHz, pre-calibrated using the rPICARD CASA-based
pipeline. For antenna-based gain calibration and imaging, we use the
Bayesian imaging software resolve. To estimate gain and image
uncertainties, we use a Variational Inference method.
We obtain a high-resolution M87 Stokes I image at 43GHz in
conjunction with antenna-based gain solutions using our Bayesian
self-calibration and imaging method. The core with counter-jet
structure is better resolved, and extended jet emission is better
described compared to the CLEAN reconstruction. Furthermore,
uncertainty estimation of the image and antenna-based gains allows us
to quantify the reliability of the result.
Our Bayesian self-calibration and imaging pipeline is able to
reconstruct robust and reproducible Stokes I images with gain
solutions without the need of human interaction.
Description:
To validate the Bayesian self-calibration and imaging method
on the real data, we applied it to a Very Long Baseline Array (VLBA)
observation of M87 in 2013 at 43GHz (7mm).
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
12 30 49.42 +12 23 28.0 M87 = NGC 4486
-----------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 137 2 List of fits images
fits/* . 2 Individual fits images
--------------------------------------------------------------------------------
See also:
J/A+A/616/A188 : M87 jet VLBI images (Kim+, 2018)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 34 I5 Kibyte size Size of FITS file
36- 68 A33 --- FileName Name of FITS file, in subdirectory fits
70-137 A68 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Jong-Seo Kim, jongkim(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 02-Sep-2024