Amazing stuff!
"Astronomers have discovered a new celestial object, a compact radio beacon located in the galaxy NGS 4945, about 12 million light-years away. Its light is polarized at an almost impossible level that hints at a perfectly aligned magnetic field. The object has been nicknamed "Punctum"; it’s a signal so clean and precise that it stands out like a lighthouse beam cutting through fog.
In a groundbreaking new study, astronomers ... first spotted the new celestial object using the Atacama Large Millimeter/submillimeter Array (ALMA), during Band 3 observations (92-104 GHz) of the starburst galaxy NGC 4945. At the time, researchers were observing the bright, active core of the galaxy when they came across something unexpected. ..."
From the abstract:
"We report the discovery of a highly polarized millimeter (mm) continuum source in the central region of NGC 4945, identified through ALMA Band 3 observations. This starburst Seyfert 2 galaxy contains numerous compact mm sources, yet only one - located approximately 3.4" (~60 pc) from the galactic center and unresolved with ~0.1" resolution - exhibits an unusually high polarization degree of 50% 14%, likely originating from non-thermal synchrotron radiation. The source is faint, yet clearly detected in two separate epochs of observation taken 14 days apart, with flux of 0.104 0.018 and 0.125 0.016 mJy, as well as in earlier ALMA observations, showing no variability at any timescale. The spectral index remains stable within large uncertainties, -1.8 2.5 and -1.3 2.5.
The source, which we further refer to as Punctum due to its compactness, revealed no clear counterparts in existing X-ray or radio observations. Assuming association with the central region of NGC 4945, we estimate upper limits for its luminosity of ~1 10 erg s in the 3-6 keV X-ray band (from archival Chandra data) and ~5 10 erg s at 23 GHz (from archival ATCA data).
A comparison of the radio, mm (including polarization), and X-ray properties with known astrophysical sources emitting synchrotron radiation, such as accreting neutron stars, supernova remnants, and non-thermal galactic filaments, revealed no clear match in any of these scenarios. The exact nature of this highly polarized source remains undetermined."
ALMA discovery of Punctum, a highly polarized millimeter source in the nuclear starburst galaxy NGC 4945 (a forthcoming article)
ALMA discovery of Punctum -- a highly polarized mm source in nuclear starburst galaxy NGC 4945 (preprint, open access)
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