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Hubble space telescope emission-line Images of nearby 3CR radio galaxies: Two photoionization, accretion, and feedback modes

Hubble space telescope emission-line Images of nearby 3CR radio galaxies: Two photoionization, accretion, and feedback modes
Hubble space telescope emission-line Images of nearby 3CR radio galaxies: Two photoionization, accretion, and feedback modes

We present HST/ACS narrowband images of a low-z sample of 19 3C radio galaxies to study the Hα and [O iii] emissions from the narrow-line region. Based on nuclear emission-line ratios, we divide the sample into high- and low-excitation galaxies (HEGs and LEGs). We observe different line morphologies, extended [O iii] emission, large [O iii]/Hα scatter across the galaxies, and a radio-line alignment. In general, HEGs show more prominent emission-line properties than LEGs: larger, more disturbed, more luminous, and more massive regions of ionized gas with slightly larger covering factors. We find evidence of correlations between line luminosities and (radio and X-ray) nuclear luminosities. All of these results point to a main common origin, the active nucleus, which ionizes the surrounding gas. However, the contribution of additional photoionization mechanisms (jet shocks and star formation) is needed to account for the different line properties of the two classes. A relationship between the accretion, photoionization, and feedback modes emerges from this study. For LEGs (hot-gas accretors), the synchrotron emission from the jet represents the main source of ionizing photons. The lack of cold gas and star formation in their hosts accounts for the moderate ionized-gas masses and sizes. For HEGs (cold-gas accretors), an ionizing continuum from a standard disk and shocks from the powerful jets are the main sources of photoionization, with a contribution from star formation. These components, combined with the large reservoir of cold/dust gas brought from a recent merger, account for the properties of their extended emission-line regions.

galaxies: active, galaxies: elliptical and lenticular, cD, galaxies: ISM, galaxies: jets, quasars: emission lines, radio continuum: galaxies
0004-637X
Baldi, Ranieri D.
c416ed4c-5d1c-48ee-989c-3a8ab38cd124
Rodríguez Zaurín, Javier
e4399417-6665-4b69-a98f-8e652f76579a
Chiaberge, Marco
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Capetti, Alessandro
4b5a2e61-ac39-42ca-aa3e-15983b11146c
Sparks, William B.
e5db8064-89b7-4605-ae28-22fadcbf63ed
McHardy, Ian M.
4f215137-9cc4-4a08-982e-772a0b24c17e
Baldi, Ranieri D.
c416ed4c-5d1c-48ee-989c-3a8ab38cd124
Rodríguez Zaurín, Javier
e4399417-6665-4b69-a98f-8e652f76579a
Chiaberge, Marco
c8e0b1d8-d96a-4fb6-b723-b921b9758add
Capetti, Alessandro
4b5a2e61-ac39-42ca-aa3e-15983b11146c
Sparks, William B.
e5db8064-89b7-4605-ae28-22fadcbf63ed
McHardy, Ian M.
4f215137-9cc4-4a08-982e-772a0b24c17e

Baldi, Ranieri D., Rodríguez Zaurín, Javier, Chiaberge, Marco, Capetti, Alessandro, Sparks, William B. and McHardy, Ian M. (2019) Hubble space telescope emission-line Images of nearby 3CR radio galaxies: Two photoionization, accretion, and feedback modes. The Astrophysical Journal, 870 (1). (doi:10.3847/1538-4357/aaf002).

Record type: Article

Abstract

We present HST/ACS narrowband images of a low-z sample of 19 3C radio galaxies to study the Hα and [O iii] emissions from the narrow-line region. Based on nuclear emission-line ratios, we divide the sample into high- and low-excitation galaxies (HEGs and LEGs). We observe different line morphologies, extended [O iii] emission, large [O iii]/Hα scatter across the galaxies, and a radio-line alignment. In general, HEGs show more prominent emission-line properties than LEGs: larger, more disturbed, more luminous, and more massive regions of ionized gas with slightly larger covering factors. We find evidence of correlations between line luminosities and (radio and X-ray) nuclear luminosities. All of these results point to a main common origin, the active nucleus, which ionizes the surrounding gas. However, the contribution of additional photoionization mechanisms (jet shocks and star formation) is needed to account for the different line properties of the two classes. A relationship between the accretion, photoionization, and feedback modes emerges from this study. For LEGs (hot-gas accretors), the synchrotron emission from the jet represents the main source of ionizing photons. The lack of cold gas and star formation in their hosts accounts for the moderate ionized-gas masses and sizes. For HEGs (cold-gas accretors), an ionizing continuum from a standard disk and shocks from the powerful jets are the main sources of photoionization, with a contribution from star formation. These components, combined with the large reservoir of cold/dust gas brought from a recent merger, account for the properties of their extended emission-line regions.

Text
HST EMISSION-LINE IMAGES OF NEARBY 3CR RADIO GALAXIES- TWO PHOTOIONIZATION, ACCRETION AND FEEDBACK MODES - Accepted Manuscript
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Accepted/In Press date: 8 November 2018
e-pub ahead of print date: 7 January 2019
Published date: January 2019
Keywords: galaxies: active, galaxies: elliptical and lenticular, cD, galaxies: ISM, galaxies: jets, quasars: emission lines, radio continuum: galaxies

Identifiers

Local EPrints ID: 427944
URI: https://eprints.soton.ac.uk/id/eprint/427944
ISSN: 0004-637X
PURE UUID: 660bc8ed-2cc5-4f1e-ad3f-8a51d014ad05

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Date deposited: 05 Feb 2019 17:30
Last modified: 07 May 2019 16:30

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Contributors

Author: Javier Rodríguez Zaurín
Author: Marco Chiaberge
Author: Alessandro Capetti
Author: William B. Sparks
Author: Ian M. McHardy

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