The low frequency radio detection using #LOFAR, allows to refine our understanding of this cosmic monsters which I described already in the past (https://mastodon.social/)
An important milestone for #radioastronomy: LOFAR ERIC was founded today, an independent European research organisation that will now manage the world's largest radio telescope #LOFAR. The organisation will e.g. enable large-scale studies of galaxies, pulsars and space weather. https://www.aip.de/news/en/lofar-eric
“Efficiency of turbulent reacceleration by solenoidal turbulence and its application to the origin of
radio mega halos in cluster outskirts” by K. Nishiwaki, Brunetti, Vazza & Gheller.
It is a new sophisticated exploration of the evolution of relativistic electrons in the vast volume of galaxy clusters, and it uses a cosmological MHD simulations to make a sense of recent fascinating radio observations.
It is now commonly accepted that Fermi II processes triggered by the turbulence of the very hot and diluted gas can explain these features…but reproducing in detail the morphological and spectrally resolved radio observations by telescopes like #LOFAR is a challenge for theoreticians.
The particular real system under the focus in this article is Abell 2255, which was recently observed in very great detail with one of the deepest LOFAR observations by Botteon et al.
It's described as "the largest radiotelescope in the world which can operate at the lowest frequencies that can be observed from earth" and it's about a thousand km wide, which makes it a nice example of peaceful international scientific cooperation.
What is this weird long radio structure in between two clusters of galaxies?
It's a....bridge! 🌉
In particular, it is the radio bridge connecting two of the most massive clusters in the nearby Universe: Abell 399 and Abell 401.
Huge discovery in 2019, by F.Govoni and collaborators, using LOFAR: https://arxiv.org/abs/1906.07584 #Astrodon#Astronomy
Let me use this new #AstrophysicsFactlet to tell you a bit about this discovery, and why we care so much!
The emission was the first discovered of this kind: it is the largest unique radio structure in the sky so far discovered (nearly 3.5 Megaparsecs from side to side!) and it is a surprise, because it appears between two clusters of galaxies which still have to undergo a merger.
It was discovered using the LOFAR telescope, High Band Antenna (HBA), at about 200 MHz, in a deep observation by F. Govoni (INAF) and collaborator (including your truly) in 2019.
Today, a group of scientists including @cgbassa and Yours truly published a paper on A&A. We report about a fascinating finding: #satellite constellations can leak electromagnetic radiowaves, originating from onboard electronics, which we detected using the #LOFAR radio telescope. 1/
In case you were wondering how we attempted to find satellite signals in the #LOFAR data, here is a summary of the approach:
The basic idea was to use satellite #TLE (two line elements) to predict when a satellite would be crossing the field of view. For each of the beams (pixels) on the sky, whe then extract some data around these event times (+/- some seconds). These are like the spectrograms included in the paper. 7/
The image below shows Figure 7 of the paper; a masterpiece by @cgbassa