Astronomers confirm powerful radio galaxy from nearly 12.5 billion years ago
Follow-up spectroscopy placed radio galaxy TXS 2354+015 at redshift 4.946, nearly 12.5 billion years in the past.
Astronomers have confirmed a powerful radio galaxy from nearly 12.5 billion years ago. The source, TXS 2354+015, was first identified as a high-redshift candidate from a characteristic drop in its optical light. Follow-up spectroscopy placed it at a redshift of 4.946. The paper was posted to the arXiv preprint server on 23 September.
The team, led by Barbara Balmaverde of the INAF Astrophysical Observatory of Turin, combined deep optical imaging from the Subaru Hyper Suprime-Cam Subaru Strategic Program survey with radio catalogues including TGSS at 150 MHz and VLASS at 3 GHz. They searched for radio sources whose optical counterparts showed the Lyman-break dropout feature between redshifts of 4.5 and 5.3, when the universe was 1.1 billion to 1.3 billion years old.
TXS 2354+015 showed a prominent Lyman-alpha emission line in its optical spectrum. The team verified the redshift using a second, fainter emission line.
This approach was chosen because the dominant method of hunting radio sources, which looks for unusually steep spectra, appears to miss a large part of the population. A 2024 study suggests as many as 90% of such sources at redshifts above 3.5 might be hidden in the ultraviolet and optical bands.
Sourcephys.org