Astronomers using NSF’s Karl G. Jansky Very Large Array have produced a high-resolution map of the Perseus cluster, a collection of thousands of galaxies approximately 240 million light-years from Earth.
The central part of the total field of view of the VLA radio map of the Perseus cluster. NGC 1275 is the bright source in the middle of the image. The wide-angle tail radio galaxy NGC 1265 (NNW of NGC 1275) and the head-tail CR 15 (between NGC 1275 and IC 310), as well as IC 310 (WSW of NGC 1275) are clearly visible. Image credit: Gendron-Marsolais et al., doi: 10.1093/mnras/staa2003.
Approximately 11 million light-years across and located 240 million light-years away, the Perseus cluster is named for its host constellation.
Also known as Abell 426, it is one of the most massive objects in the observable Universe, containing over 1,000 galaxies immersed in a vast gas cloud.
Like all galaxy clusters, most of its observable matter takes the form of a pervasive gas averaging tens of millions of degrees, so hot it only glows in X-rays.
The galaxy sitting in the center of the Perseus cluster is NGC 1275, a very peculiar galaxy that emits abundant radio signals, for this known as Perseus A.
The cluster also hosts several other radio galaxies with complex structure, including NGC 1265, NGC 1272, CR 15, and IC 310.
ESO astronomer Marie-Lou Gendron-Marsolais and colleagues used the Very Large Array (VLA) to learn how a crowded environment affects galaxies in the Perseus cluster.
They identified previously unknown structures, both in the central regions surrounding NGC 1275 and in several complex radio sources.
Left: NGC 1275, at the core of the cluster, is seen in new detail, including a newly-revealed wealth of complex, filamentary structure in its radio lobes. Center: NGC 1265 shows the effects of its motion through the tenuous material between the galaxies; its radio jets are bent backward by that interaction, then merge into a single, broad tail; the tail then is further bent, possibly by motions within the intergalactic material. Right: the jets of IC 310 are bent backward, similarly to NGC 1265, but appear closer because of the viewing angle from Earth; that angle also allows astronomers to directly observe energetic gamma rays generated near the supermassive black hole at the galaxy’s core. Image credit: Gendron-Marsolais et al. / S. Dagnello / NRAO / AUI / NSF / Sloan Digital Sky Survey.
“New hints of sub-structures appear in the inner radio lobes of the brightest cluster galaxy NGC 1275,” the astronomers wrote in their paper.
“The spurs of radio emission extending into the outer X-ray cavities, inflated by past nuclear outbursts, are seen for the first time at these frequencies, consistent with spectral aging.”
“Beyond NGC 1275, we also analyze complex radio sources harbored in the cluster,” they added.
“Two new distinct, narrowly collimated jets are visible in IC 310, consistent with a highly projected narrow-angle tail radio galaxy infalling into the cluster.”
“We show how this is in agreement with its blazar-like behavior, implying that blazars and bent-jet radio galaxies are not mutually exclusive.”
The researchers also spotted filamentary structures across the entire tail of NGC 1265.
“We resolve the very narrow and straight tail of CR 15 without indication of double jets, so that the interpretation of such head-tail sources is yet unclear,” they wrote.
“Finally, we note that only the brightest western parts of the mini-halo remain, near NGC 1272 and its bent double jets.”
The team’s paper was published in the Monthly Notices of the Royal Astronomical Society.
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M. Gendron-Marsolais et al. 2020. High-resolution VLA low radio frequency observations of the Perseus cluster: radio lobes, mini-halo, and bent-jet radio galaxies. MNRAS 499 (4): 5791-5805; doi: 10.1093/mnras/staa2003
