Mining Mini-Halos with MeerKAT I. Calibration and Imaging
Date Issued
2023
Author(s)
Trehaeven, K. S.
•
Parekh, V.
•
Oozeer, N.
•
Hugo, B.
•
Smirnov, O.
•
•
Knowles,K.
•
Tasse, C.
•
Asad, K. M. B.
•
Giacintucci, S.
Abstract
Radio mini-halos are clouds of diffuse, low surface brightness synchrotron
emission that surround the Brightest Cluster Galaxy (BCG) in massive cool-core
galaxy clusters. In this paper, we use third generation calibration (3GC), also
called direction-dependent (DD) calibration, and point source subtraction on
MeerKAT extragalactic continuum data. We calibrate and image archival MeerKAT
L-band observations of a sample of five galaxy clusters (ACO 1413, ACO 1795,
ACO 3444, MACS J1115.8+0129, MACS J2140.2-2339). We use the CARACal pipeline
for direction-independent (DI) calibration, DDFacet and killMS for 3GC,
followed by visibility-plane point source subtraction to image the underlying
mini-halo without bias from any embedded sources. Our 3GC process shows a
drastic improvement in artefact removal, to the extent that the local noise
around severely affected sources was halved and ultimately resulted in a 7\%
improvement in global image noise. Thereafter, using these spectrally
deconvolved Stokes I continuum images, we directly measure for four mini-halos
the flux density, radio power, size and in-band integrated spectra. Further to
that, we show the in-band spectral index maps of the mini-halo (with point
sources). We present a new mini-halo detection hosted by MACS J2140.2-2339,
having flux density $S_{\rm 1.28\,GHz} = 2.61 \pm 0.31$ mJy, average diameter
296 kpc and $\alpha^{\rm 1.5\,GHz}_{\rm 1\,GHz} = 1.21 \pm 0.36$. We also found
a $\sim$100 kpc southern extension to the ACO 3444 mini-halo which was not
detected in previous VLA L-band observations. Our description of MeerKAT
wide-field, wide-band data reduction will be instructive for conducting further
mini-halo science.
Volume
520
Issue
3
Start page
4410
Issn Identifier
0035-8711
Rights
open.access
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