Astronomers using the LOw-Frequency ARray (LOFAR), discovered a diffuse radio halo across the spiral galaxy NGC 4565. The finding, reported in a paper revealed July 16 on the arXiv pre-print server, could shed more light on the character of NGC 4565, disclosing valuable insights about star-forming activity and the distribution of cosmic-ray electrons on this galaxy.
Radio haloes are commonly noticed around late-sort spiral galaxies seen in an edge-on orientation. Studies show that the emission in radiohalos is dominated by the non-thermal radio continuum component, indicative of cosmic-ray electrons (CRe) and magnetic fields.
Very little is known about the transport of cosmic rays in galaxies other than Milky Way. Low-frequency radio continuum observations have the potential to alter this. They permit to analyze the oldest CRe far away from star formation sites in the halos of galaxies.
So a team of astronomers led by Volker Heesen of the University of Hamburg in Germany used LOFAR to conduct deep, low-frequency (144 MHz) observations of NGC 4565. Positioned about 38.8 million gentle years away, the target is a late-type spiral galaxy at a nearly edge-on orientation. It is a quiescent galaxy with a low star-formation rate and an average mass surface density.
During the observations, the astronomers detected a warp within the radio continuum of NGC 4565 that is reminiscent of an impartial hydrogen line (HI) warp and identifying a slight flaring of the galaxy’s radio halo. The researchers assume that this flaring is attributable to the warp because the vertical depth profiles are asymmetric, which is in the settlement with the warp. Following the study, the minimum age for the warp was estimated at roughly 130 million years. That is the spectral age of the galaxy’s CRe, during which they are transported into the warp.
Taking into account the results, the astronomers concluded that the NGC 4565 could also be within the aftermath of an interval with new intense star formation. They added that the galaxy has a comparatively old inhabitant of CRe that has slowly diffused away from the star-forming disc.