Interactions between large-scale radio structures and gas in a sample of optically selected type 2 quasars^⋆

¹ Centro de Astrobiología, CSIC-INTA, Ctra. de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
e-mail: villarmm@cab.inta-csic.es
² National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
³ GRANTECAN, Cuesta de San José s/n, 38712 Breña Baja, La Palma, Spain
⁴ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
⁵ Centro de Astrobiología, CSIC-INTA, ESAC Campus, 28692 Villanueva de la Cañada, Madrid, Spain
⁶ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁷ Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS, Brazil
⁸ Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

Received: 10 October 2020
Accepted: 10 March 2021

Abstract

Context. The role of radio mode feedback in non radio-loud quasars needs to be explored in depth to determine its true importance. Its effects can be identified based on the evidence of interactions between the radio structures and the ambient ionised gas.

Aims. We investigate this interaction in a sample of 13 optically selected type 2 quasars (QSO2) at z < 0.2 with the Very Large Array (VLA) FIRST Survey radio detections, none of which are radio-loud. The ranges of [OIII]λ5007 and monochromatic radio luminosities are log(L_[OIII]/erg s⁻¹) ∼ 42.08–42.79 and log(P_1.4 GHz/erg s⁻¹ Hz⁻¹) ∼ 30.08−31.76. All of them show complex optical morphologies, with signs of distortion across tens of kpc due to mergers and interactions.

Methods. We searched for evidence of interactions between the radio structures and the ionised gas by characterising and comparing their morphologies. The former was traced by narrow band Hα images obtained with the GTC 10.4 m Spanish telescope and the Osiris instrument. The latter is traced by VLA radio maps obtained with A and B configurations to achieve both high resolution and brightness sensitivity.

Results. The radio luminosity has an active galatic nucleus (AGN) component in 11 our of 13 QSO2, which is spatially extended in our radio data in 9 of them (jets, lobes, or other). The relative contribution of the extended radio emission to the total P_1.4 GHz is in most cases in the range from 30% to 90%. The maximum sizes are in the range of d^R_max of around a few to 500 kpc. The QSO2 undergoing interaction or merger events appear to be invariably associated with ionised gas spread over large spatial scales with maximum distances from the AGN in the range r_max ∼ 12−90 kpc. The morphology of the ionised gas at < 30 kpc is strongly influenced by AGN related processes. Evidence for radio-gas interactions exist in 10 out of 13 QSO2; that is, in all but one with confirmed AGN radio components. The interactions are identified across different spatial scales, from the nuclear narrow line region up to tens of kpc.

Conclusions. Although this sample cannot be considered representative of the general population of QSO2, it supports the idea that large-scale low to modest power radio sources can exist in radio-quiet QSO2, which can provide a source of feedback on scales of the spheroidal component of galaxies and well into the circumgalactic medium, in systems where radiative mode feedback is expected to dominate.