| 7th of April 2021 |
|---|
 |
| The Ultra-Steep Spectrum Jellyfish |
| by Hodgson et al. |
|
Hodgson et al.
have reported the discovery
of an ultra-steep spectrum (USS) synchrotron source in the galaxy
cluster Abell 2877. They observed the source with the Murchison
Widefield Array at five frequencies between 72 MHz and 231 MHz and
found the source to exhibit strong spectral curvature over this range,
and the steepest known spectra of a synchrotron cluster source, with a
spectral index across the central three frequency bands of α =
-6. Higher frequency radio observations, including a deep observation
with the Australia Telescope Compact Array, did not detect any of the
extended diffuse emission.
The source is approximately 370 kpc wide and at the lowest frequencies resembles a jellyfish, with two peaks of emission and long tentacles descending south towards the cluster centre. The image above is a composite image of the "USS Jellyfish" in Abell 2877 showing the optical Digitised Sky Survey (background) with XMM X-ray data (magenta overlay) and MWA 118 MHz radio data (red-yellow overlay). The results are reported in a paper published in The Astrophysical Journal. (Image credit: Torrance Hodgson, ICRAR/Curtin University.) |