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arXiv · 2212.01707

Powerful yet lonely: Is 3C 297 a high-redshift fossil group?

Valentina Missaglia·Juan P. Madrid·Mischa Schirmer·Francesco Massaro·Alberto Rodriguez-Ardila·Carlos J. Donzelli·Martell Valencia·Alessandro Paggi·Ralph P. Kraft·Chiara Stuardi·Belinda J. Wilkes
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Abstract

The environment of the high-redshift (z=1.408), powerful radio-loud galaxy 3C 297 has several distinctive features of a galaxy cluster. Among them, a characteristic halo of hot gas revealed by Chandra X-ray observations. In addition, a radio map obtained with the Very Large Array (VLA) shows a bright hotspot in the northwestern direction, created by the interaction of the AGN jet arising from 3C 297 with its environment. In the X-ray images, emission cospatial with the northwestern radio lobe is detected, and peaks at the position of the radio hotspot. The extended, complex X-ray emission observed with our new Chandra data is largely unrelated to its radio structure. Despite having attributes of a galaxy cluster, no companion galaxies have been identified from 39 new spectra of neighboring targets of 3C 297 obtained with the Gemini Multi-Object Spectrograph. None of the 19 galaxies for which a redshift was determined lies at the same distance as 3C 297. The optical spectral analysis of the new Gemini spectrum of 3C 297 reveals an isolated Type-II radio-loud AGN. We also detected line broadening in [O II](3728) with a FWHM about 1700 km/s and possible line shifts of up to 500-600 km/s. We postulate that the host galaxy of 3C 297 is a fossil group, in which most of the stellar mass has merged into a single object, leaving behind an X-ray halo.

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Valentina Missaglia, Juan P. Madrid, Mischa Schirmer, Francesco Massaro, Alberto Rodriguez-Ardila, Carlos J. Donzelli, Martell Valencia, Alessandro Paggi, Ralph P. Kraft, Chiara Stuardi, Belinda J. Wilkes. 2022-12-03. Powerful yet lonely: Is 3C 297 a high-redshift fossil group?. https://doi.org/10.3847/1538-4365/ac9f3e

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