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The nuclear activity and central structure of the elliptical galaxy NGC 5322

The nuclear activity and central structure of the elliptical galaxy NGC 5322
The nuclear activity and central structure of the elliptical galaxy NGC 5322

We have analysed a new high-resolution e-MERLIN 1.5 GHz radio continuum map together with HST and SDSS imaging of NGC 5322, an elliptical galaxy hosting radio jets, aiming to understand the galaxy's central structure and its connection to the nuclear activity. We decomposed the composite HST + SDSS surface brightness profile of the galaxy into an inner stellar disc, a spheroid, and an outer stellar halo. Past works showed that this embedded disc counter-rotates rapidly with respect to the spheroid. The HST images reveal an edge-on nuclear dust disc across the centre, aligned along the major-axis of the galaxy and nearly perpendicular to the radio jets. After careful masking of this dust disc, we find a central stellar mass deficit Mdef in the spheroid, scoured by SMBH binaries with final mass MBH such that Mdef/MBH ~ 1.3-3.4. We propose a three-phase formation scenario for NGC 5322, where a few (2-7) 'dry' major mergers involving SMBHs built the spheroid with a depleted core. The cannibalism of a gas-rich satellite subsequently creates the faint counter-rotating disc and funnels gaseous material directly on to the AGN, powering the radio core with a brightness temperature of TB,core ~ 4.5 × 107 K and the low-power radio jets (Pjets ~ 7.04 × 1020 W Hz-1), which extend ~1.6 kpc. The outer halo can later grow via minor mergers and the accretion of tidal debris. The low-luminosity AGN/jet-driven feedback may have quenched the late-time nuclear star formation promptly, which could otherwise have replenished the depleted core.

Galaxies: elliptical and lenticular, cD, Galaxies: nuclei, Galaxies: photometry, Galaxies: structure, Radio continuum: galaxies
0035-8711
4670-4682
Dullo, Bililign T.
ae12129a-e3e0-4628-a208-cb5f4b329baf
Knapen, Johan H.
530be1bc-2889-4654-a05d-788dd6f3832e
Williams, David R.A.
c9ded967-198f-4c26-96b1-8c03d7d26445
Beswick, Robert J.
d3f37275-1f32-4ba3-a745-7dab2d21da60
Bendo, George
a7ca062c-d0de-4f79-b9f1-d384db778a39
Baldi, Ranieri D.
c416ed4c-5d1c-48ee-989c-3a8ab38cd124
Argo, Megan
4099113a-b9c5-457a-b7b3-8e8cdfc71e11
McHardy, Ian M.
4f215137-9cc4-4a08-982e-772a0b24c17e
Muxlow, Tom
7eeabedc-e9a3-4765-8bcd-077940454ab0
Westcott, J.
4ac23629-2401-48c0-8c76-03b81a590c95
Dullo, Bililign T.
ae12129a-e3e0-4628-a208-cb5f4b329baf
Knapen, Johan H.
530be1bc-2889-4654-a05d-788dd6f3832e
Williams, David R.A.
c9ded967-198f-4c26-96b1-8c03d7d26445
Beswick, Robert J.
d3f37275-1f32-4ba3-a745-7dab2d21da60
Bendo, George
a7ca062c-d0de-4f79-b9f1-d384db778a39
Baldi, Ranieri D.
c416ed4c-5d1c-48ee-989c-3a8ab38cd124
Argo, Megan
4099113a-b9c5-457a-b7b3-8e8cdfc71e11
McHardy, Ian M.
4f215137-9cc4-4a08-982e-772a0b24c17e
Muxlow, Tom
7eeabedc-e9a3-4765-8bcd-077940454ab0
Westcott, J.
4ac23629-2401-48c0-8c76-03b81a590c95

Dullo, Bililign T., Knapen, Johan H., Williams, David R.A., Beswick, Robert J., Bendo, George, Baldi, Ranieri D., Argo, Megan, McHardy, Ian M., Muxlow, Tom and Westcott, J. (2018) The nuclear activity and central structure of the elliptical galaxy NGC 5322. Monthly Notices of the Royal Astronomical Society, 475 (4), 4670-4682. (doi:10.1093/mnras/sty069).

Record type: Article

Abstract

We have analysed a new high-resolution e-MERLIN 1.5 GHz radio continuum map together with HST and SDSS imaging of NGC 5322, an elliptical galaxy hosting radio jets, aiming to understand the galaxy's central structure and its connection to the nuclear activity. We decomposed the composite HST + SDSS surface brightness profile of the galaxy into an inner stellar disc, a spheroid, and an outer stellar halo. Past works showed that this embedded disc counter-rotates rapidly with respect to the spheroid. The HST images reveal an edge-on nuclear dust disc across the centre, aligned along the major-axis of the galaxy and nearly perpendicular to the radio jets. After careful masking of this dust disc, we find a central stellar mass deficit Mdef in the spheroid, scoured by SMBH binaries with final mass MBH such that Mdef/MBH ~ 1.3-3.4. We propose a three-phase formation scenario for NGC 5322, where a few (2-7) 'dry' major mergers involving SMBHs built the spheroid with a depleted core. The cannibalism of a gas-rich satellite subsequently creates the faint counter-rotating disc and funnels gaseous material directly on to the AGN, powering the radio core with a brightness temperature of TB,core ~ 4.5 × 107 K and the low-power radio jets (Pjets ~ 7.04 × 1020 W Hz-1), which extend ~1.6 kpc. The outer halo can later grow via minor mergers and the accretion of tidal debris. The low-luminosity AGN/jet-driven feedback may have quenched the late-time nuclear star formation promptly, which could otherwise have replenished the depleted core.

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More information

Accepted/In Press date: 8 January 2018
e-pub ahead of print date: 10 January 2018
Published date: 21 April 2018
Keywords: Galaxies: elliptical and lenticular, cD, Galaxies: nuclei, Galaxies: photometry, Galaxies: structure, Radio continuum: galaxies

Identifiers

Local EPrints ID: 424884
URI: http://eprints.soton.ac.uk/id/eprint/424884
ISSN: 0035-8711
PURE UUID: 76d5be40-a288-43cb-b058-099c39726c7c
ORCID for David R.A. Williams: ORCID iD orcid.org/0000-0001-7361-0246

Catalogue record

Date deposited: 05 Oct 2018 11:52
Last modified: 07 Oct 2020 01:03

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