Bibliographic Details
| Title: |
The nuclear activity and central structure of the elliptical galaxy NGC 5322 |
| Authors: |
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, Westcott, J. |
| Publication Year: |
2018 |
| Collection: |
Astrophysics |
| Subject Terms: |
Astrophysics - Astrophysics of Galaxies |
| More Details: |
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 $M_{\rm def}$ in the spheroid, scoured by SMBH binaries with final mass $M_{\rm BH}$ such that $M_{\rm def}/M_{\rm BH} \sim 1.3 - 3.4$. 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 onto the AGN, powering the radio core with a brightness temperature of $T_{\rm B,core} \sim 4.5 \times 10^{7}$ K and the low-power radio jets ($P_{\rm jets}\sim 7.04 \times 10^{20}$ W Hz$^{-1}$) which extend $\sim 1.6$ 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.
Comment: 14 pages, 5 figures, accepted for publication in MNRAS |
| Document Type: |
Working Paper |
| DOI: |
10.1093/mnras/sty069 |
| Access URL: |
http://arxiv.org/abs/1801.03660 |
| Accession Number: |
edsarx.1801.03660 |
| Database: |
arXiv |
