Monday, August 9, 2021

Dancing Ghosts: A New, Deeper Sky Scan Offers Surprises to Astronomers

  Examining recent telescope data, we saw two ghosts dancing in the depths of the cosmos.  We had never seen anything like it before and had no idea what they were.

  Several weeks later, we discovered that we were seeing two radio galaxies, about a billion light years away.  At the center of each is a supermassive black hole, spouting jets of electrons that are bent into grotesque shapes by an intergalactic wind.

 But where does the intergalactic wind come from?  Why are you so tangled up?  And what is causing the radio broadcast streams?  We still don't understand the details of what's going on here and it will likely take a lot more observations and modeling before we do.

 The EMU Pilot Survey's first big surprise was the discovery of mysterious Odd Radio Circles (ORCs), which appear to be giant radio-emission rings, nearly a million light-years across, encircling distant galaxies.

  These have never been seen before, as they are very rare and faint.  We still don't know what they are, but we're working hard to find out.

 We are finding surprises even in places we thought we understood.  Beside the well-studied galaxy IC5063, we find a giant radio galaxy, one of the largest known, whose existence has never been suspected.

 This new galaxy also contains a supermassive black hole, spewing out jets of electrons nearly 5 million light years in length.  ASKAP is the only telescope in the world that can see the full extent of this weak emission.

  What EMU can do

  Most known sources of radio emissions are caused by supermassive black holes in quasars and active galaxies, which produce exceptionally bright signals.  This is because radio telescopes have always struggled to see the much fainter radio emissions from normal spiral galaxies like our Milky Way.

  The EMU project goes deep enough to see them too.  EMU sees nearly every spiral galaxy in the nearby Universe that was previously seen only by optical and infrared telescopes.  The EMU can even trace the spiral arms to the nearest ones.


 The two galaxies that we believe are responsible for the streams of electrons (shown as curved arrows) that form the Dancing Ghosts.  But we don't understand what's causing the filament labeled 3. Jayanne English and Ray Norris image using EMU and Dark Energy Survey data

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