Speaker
Description
Merging galaxy clusters host Megaparsec-scale diffuse radio emission that traces re-accelerated cosmic ray electrons in the intracluster medium. Recent observations report a growing number of enigmatic radio filaments connected to the lobes of cluster radio galaxies, which may transport and preserve relativistic electrons and thereby seed diffuse cluster-scale radio sources. Resolving these filaments and measuring their spectra requires ≲1arcsecond resolution at low radio frequencies, achievable only with very-long baseline interferometry (VLBI).
At frequencies below 100 MHz, however, severe ionospheric systematic effects have so far limited VLBI observations to a few extremely bright and compact sources.
In this talk, I present the first-ever wide-field VLBI image obtained at these ultra-low frequencies, enabled by a novel calibration strategy. An 8h LOFAR LBA VLBI observation of the Abell 2255 cluster reaches a noise level of 650 µJy/beam at 0.9''x0.5'' resolution in the 40-60 MHz band over four square-degrees, with direction-dependent calibration using ten in-field calibrators.
These data demonstrate the feasibility of sub-arcsecond imaging at tens of MHz and open a new observational window for studying the origin and transport of cosmic ray electrons in clusters. I will showcase their scientific potential at the example of the Abell 2255 cluster.
| Talk category | NOVA Network 3 |
|---|---|
| Second preference | NOVA Network 1, Plenary |
