Digging deeper into NGC 6868 II: ionized gas and excitation mechanism

ABSTRACT We studied the ionized gas in the inner region ($\sim$$680\times 470$ pc2) of the galaxy NGC 6868 using Gemini/GMOS (Gemini Multi-Object Spectrograph) integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow ($\sigma \sim 110$ km s$^{-1}$) tracing an ionized gas disc and a broad component ($\sigma \sim 300$ km s$^{-1}$) mainly associated with inflowing/outflowing gas. The derived V-band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from $\sim$14 000 K in the central region to $\gtrsim 20000$ K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching $N_e\sim 4000$ cm–3 for the broad component decreasing to $N_e\sim 100$ cm–3 towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both active galactic nucleus (AGN) and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionization mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-09-05
DOI
https://doi.org/10.1093/mnras/stae2077
Citations
1
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
Field-Weighted Citation Impact
0.33

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article

Digging deeper into NGC 6868 II: ionized gas and excitation mechanism

Daniel Ruschel-Dutra, Marina Trevisan, A. Vazdekis, J. E. Steiner et al.
1 citations
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
0.33
article

Digging deeper into NGC 6868 II: ionized gas and excitation mechanism

Daniel Ruschel-Dutra, Marina Trevisan, A. Vazdekis, J. E. Steiner, A. Rodríguez-Ardila, Anna Ferré-Mateu, Rogemar A. Riffel, Rogério Riffel, T. V. Ricci, L G Dahmer-Hahn, João P. V. Benedetti, M. G. Pastoriza
article en
1 citations

Abstract

ABSTRACT We studied the ionized gas in the inner region ($\sim$$680\times 470$ pc2) of the galaxy NGC 6868 using Gemini/GMOS (Gemini Multi-Object Spectrograph) integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow ($\sigma \sim 110$ km s$^{-1}$) tracing an ionized gas disc and a broad component ($\sigma \sim 300$ km s$^{-1}$) mainly associated with inflowing/outflowing gas. The derived V-band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from $\sim$14 000 K in the central region to $\gtrsim 20000$ K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching $N_e\sim 4000$ cm–3 for the broad component decreasing to $N_e\sim 100$ cm–3 towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both active galactic nucleus (AGN) and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionization mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy.

Monthly Notices of the Royal Astronomical SocietyVol. 534(1)
Universidade Federal do Rio Grande do Sul (BR), Universidad de La Laguna (ES), Universidade de São Paulo (BR), Shanghai Astronomical Observatory (CN), Universidade Federal da Fronteira Sul (BR), Universidade Federal de Santa Maria (BR), Universidade Federal de Santa Catarina (BR), Instituto de Astrofísica de Canarias (ES), Laboratório Nacional de Astrofísica (BR)
National Science Foundation, L'Oreal USA, National Natural Science Foundation of China, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Korea Astronomy and Space Science Institute, Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, Universidade Federal do Rio Grande do Sul, Ministério da Ciência, Tecnologia, Inovações e Comunicações, Fundación Bancaria Caixa d'Estalvis i Pensions de Barcelona, Agencia Nacional de Investigación y Desarrollo, Agencia Estatal de Investigación, National Key Research and Development Program of China
Openalex Percentile: Top 35%
Galaxies: Formation, Evolution, Phenomena
0.33
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