University of Oulu

Rautio, R. P. V., Watkins, A. E., Comerón, S., Salo, H., Díaz-García, S., & Janz, J. (2022). The multifarious ionization sources and disturbed kinematics of extraplanar gas in five low-mass galaxies. Astronomy & Astrophysics, 659, A153. https://doi.org/10.1051/0004-6361/202142440

The multifarious ionization sources and disturbed kinematics of extraplanar gas in five low-mass galaxies

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Author: Rautio, R. P. V.1; Watkins, A. E.2; Comerón, S.3,4;
Organizations: 1Space Physics and Astronomy research unit, University of Oulu, 90014 Oulu, Finland
2Centre of Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
3Departamento de Astrofísica, Universidad de La Laguna, 38200 La Laguna, Tenerife, Spain
4Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
5Department of Physics, Engineering Physics and Astrophysics, Queen’s University, Kingston, ON K7L 3N6, Canada
6Finnish Centre of Astronomy with ESO (FINCA), Vesilinnantie 5, FI-20014 University of Turku, Finland
7Specim, Spectral Imaging Ltd., Elektroniikkatie 13, FI-90590 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 8.5 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2022021719628
Language: English
Published: EDP Sciences, 2022
Publish Date: 2022-02-17
Description:

Abstract

Aims: We investigate the origin of the extraplanar diffuse ionized gas (eDIG) and its predominant ionization mechanisms in five nearby (17‐46 Mpc) low-mass (10⁹‐10¹⁰ M) edge-on disk galaxies: ESO 157‐49, ESO 469‐15, ESO 544‐27, IC 217, and IC 1553.

Methods: We acquired Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy and deep narrowband H_ imaging of our sample galaxies. To investigate the connection between in-plane star formation and eDIG, we measure the star formation rates (SFRs) and perform a photometric analysis of our narrowband Hα imaging. Using our MUSE data, we investigate the origin of eDIG via kinematics, specifically the rotation velocity lags. We also construct standard diagnostic diagrams and emission-line maps (EW(H), [N ii]/Hα, [S ii]//Hα, [O iii]/Hβ) and search for regions consistent with ionization by hot low-mass evolved stars (HOLMES) and shocks.

Results: We measure eDIG scale heights of hzeDIG = 0.59‐1.39 kpc and find a positive correlation between them and specific SFRs. In all galaxies, we also find a strong correlation between extraplanar and midplane radial Hα profiles. These correlations along with diagnostic diagrams suggest that OB stars are the primary driver of eDIG ionization. However, we find regions consistent with mixed OB–HOLMES and OB–shock ionization in all galaxies and conclude that both HOLMES and shocks may locally contribute to the ionization of eDIG to a significant degree. From Hα kinematics, we find rotation velocity lags above the midplane with values between 10 and 27 km s⁻¹ kpc⁻¹. While we do find hints of an accretion origin for the ionized gas in ESO 157‐49, IC 217, and IC 1553, overall the ionized gas kinematics of our galaxies do not match a steady galaxy model or any simplistic model of accretion or internal origin for the gas.

Conclusions: Despite our galaxies’ similar structures and masses, our results support a surprisingly composite image of ionization mechanisms and a multifarious origin for the eDIG. Given this diversity, a complete understanding of eDIG will require larger samples and composite models that take many different ionization and formation mechanisms into account.

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Series: Astronomy and astrophysics
ISSN: 0004-6361
ISSN-E: 1432-0746
ISSN-L: 0004-6361
Volume: 659
Article number: A153
DOI: 10.1051/0004-6361/202142440
OADOI: https://oadoi.org/10.1051/0004-6361/202142440
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: RR acknowledges funding from the Technology and Natural Sciences Doctoral Program (TNS-DP) of the University of Oulu. HS and AW acknowledge funding from the Academy of Finland grant n:o 297738. AW additionally acknowledges support from the STFC [ST/S00615X/1]. SC acknowledges funding from the State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grants “The structure and evolution of galaxies and their central regions” with reference PID2019-105602GBI00 /10.13039/501100011033, and “Thick discs, relics of the infancy of galaxies" with reference PID2020-113213GA-I00. SDG acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 893673. SDG additionally acknowledges financial support from the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement No 721463 to the SUNDIAL ITN network, from the State Research Agency (AEIMCINN) of the Spanish Ministry of Science and Innovation under the grant "The structure and evolution of galaxies and their central regions" with reference PID2019-105602GB-I00/10.13039/501100011033, and from IAC project P/300724, financed by the Ministry of Science and Innovation, through the State Budget and by the Canary Islands Department of Economy, Knowledge and Employment, through the Regional Budget of the Autonomous Community. This work was partly done using GNU Astronomy Utilities (Gnuastro, ascl.net/1801.009) version 0.13.22-69bae. Work on Gnuastro has been funded by the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT) scholarship and its Grant-in-Aid for Scientific Research (21244012, 24253003), the European Research Council (ERC) advanced grant 339659-MUSICOS, European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No 721463 to the SUNDIAL ITN, and from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2016-76219-P.
EU Grant Number: (721463) SUNDIAL - SUrvey Network for Deep Imaging Analysis and Learning
Academy of Finland Grant Number: 297738
Detailed Information: 297738 (Academy of Finland Funding decision)
Copyright information: © ESO 2021.