The Intrinsic Sizes of Odd Radio Circles
Abstract A new class of sources, the so-called odd radio circles (ORCs), have been discovered by recent sensitive, large-area radio continuum surveys. The distances of these sources have so far relied on photometric redshifts of optical galaxies found at the centers of or near ORCs. Here we present...
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Published in | The Astrophysical journal Vol. 967; no. 1; pp. 51 - 66 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
The American Astronomical Society
01.05.2024
IOP Publishing |
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
A new class of sources, the so-called odd radio circles (ORCs), have been discovered by recent sensitive, large-area radio continuum surveys. The distances of these sources have so far relied on photometric redshifts of optical galaxies found at the centers of or near ORCs. Here we present Gemini rest-frame optical spectroscopy of six galaxies at the centers of, or potentially associated with, the first five ORC discoveries. We supplement this with Legacy Survey imaging and Prospector fits to their
griz
+W1/W2 photometry. Of the three ORCs with central galaxies, all lie at distances (
z
= 0.27–0.55) that confirm the large intrinsic diameters of the radio circles (300–500 kpc). The central galaxies are massive (
M
*
∼ 10
11
M
☉
), red, unobscured ellipticals with old (≳1 Gyr) stellar populations. They have LINER spectral types that are shock-powered or active galactic nucleus (AGN)-powered. All three host low-luminosity, radio-quiet AGN. The similarity of their central galaxies is consistent with a common origin, perhaps as a blast wave from an ancient starburst. The other two ORCs are adjacent and have no prominent central galaxies. However, the
z
= 0.25 disk galaxy that lies between them hosts a Type 2, moderate-luminosity AGN. They may instead be the lobes of a radio jet from this AGN. |
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Bibliography: | Galaxies and Cosmology AAS51540 |
ISSN: | 0004-637X 1538-4357 |
DOI: | 10.3847/1538-4357/ad3934 |