The detection and study of magnetic fields surrounding galaxies is important
to understand galaxy evolution since magnetic fields are tracers for dynamical
processes in the circumgalactic medium (CGM) and can have a significant impact
on the evolution of the CGM. The Faraday rotation measure (RM) of the polarized
light of background radio sources passing through the magnetized CGM of
intervening galaxies can be used as a tracer for the strength and extent of
magnetic fields around galaxies. We use rotation measures observed by the
MIGHTEE-POL (MeerKAT International GHz Tiered Extragalactic Exploration
POLarisation) survey by MeerKAT in the XMM-LSS and COSMOS fields to investigate
the RM around foreground star-forming galaxies. We use spectroscopic catalogs
of star-forming and blue cloud galaxies to measure the RM of MIGHTEE-POL
sources as a function of the impact parameter from the intervening galaxy. We
then repeat this procedure using a deeper galaxy catalog with photometric
redshifts. For the spectroscopic star-forming sample we find a
redshift-corrected |RM| excess of 5.6 +/- 2.3 rad m-2 which corresponds to a
2.5 sigma significance around galaxies with a median redshift of z = 0.46 for
impact parameters below 130 kpc only selecting the intervenor with the smallest
impact parameter. Making use of a photometric galaxy catalog and taking into
account all intervenors with Mg < -13.6 mag, the signal disappears. We find no
indication for a correlation between redshift and RM, nor do we find a
connection between the total number of intervenors to the total |RM| . We have
presented tentative evidence that the CGM of star-forming galaxies is permeated
by coherent magnetic fields within the virial radius. We conclude that mostly
bright, star-forming galaxies with impact parameters less than 130 kpc
significantly contribute to the RM of the background radio source.Comment: 11 pages, 8 figures, accepted for publication in A&