The extended H i halo of NGC 4945 as seen by MeerKAT

Author:

Ianjamasimanana Roger123ORCID,Koribalski B S45ORCID,Józsa Gyula I G236,Kamphuis Peter7,de Blok W J G8910,Kleiner Dane11ORCID,Namumba Brenda2,Carignan Claude91213,Dettmar Ralf-Jürgen7,Serra Paolo11,Smirnov Oleg M23,Thorat Kshitij1415ORCID,Hugo Benjamin V23,Ramaila Athanaseus J T3,Maina Eric2,Maccagni Filippo M11ORCID,Makhathini Sphesihle16,Andati Lexy A L2,Molnár Dániel Cs11,Perkins Simon3,Loi Francesca11ORCID,Ramatsoku Mpati211,Atemkeng Marcellin2ORCID

Affiliation:

1. Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, E-18008 Granada, Spain

2. Department of Physics and Electronics, Rhodes University, PO Box 94, Makhanda 6140, South Africa

3. South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory, Cape Town 7925, South Africa

4. Australia Telescope National Facility, CSIRO Astronomy and Space Science, PO Box 76, NSW 1710, Epping, Australia

5. Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia

6. Max-Planck-Institut für Radioastronomie, Radioobservatorium Effelsberg, Max-Planck-Straße 28, D-53902 Bad Münstereifel, Germany

7. Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute, D-44780 Bochum, Germany

8. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, NL-7990 AA Dwingeloo, the Netherlands

9. Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa

10. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, the Netherlands

11. INAF - Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy

12. Département de physique, Université de Montréal, Complexe des sciences MIL, 1375 Avenue Thérèse-Lavoie-Roux Montréal, Qc, H2V 0B3, Canada

13. Laboratoire de Physique et de Chimie de l’Environnement, Observatoire d’Astrophysique de l’Université Ouaga I Pr Joseph Ki-Zerbo (ODAUO), BP 7021, Ouaga 03, Burkina Faso

14. Department of Physics, University of Pretoria, Hatfield, Pretoria 0028, South Africa

15. The Inter-University Institute for Data Intensive Astronomy (IDIA), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa

16. University of the Witswatersrand, 1 Jan Smuts Avenue, Braamfontein 2000, Johannesburg, South Africa

Abstract

ABSTRACT Observations of the neutral atomic hydrogen (H i) in the nuclear starburst galaxy NGC 4945 with MeerKAT are presented. We find a large amount of halo gas, previously missed by H i observations, accounting for 6.8 per cent of the total H i mass. This is most likely gas blown into the halo by star formation. Our maps go down to a 3σ column density level of 5 × 1018 cm−2. We model the H i distribution using tilted-ring fitting techniques and find a warp on the galaxy’s approaching and receding sides. The H i in the northern side of the galaxy appears to be suppressed. This may be the result of ionization by the starburst activity in the galaxy, as suggested by a previous study. The origin of the warp is unclear but could be due to past interactions or ram pressure stripping. Broad, asymmetric H i absorption lines extending throughout the H i emission velocity channels are present towards the nuclear region of NGC 4945. Such broad lines suggest the existence of a nuclear ring moving at a high circular velocity. This is supported by the clear rotation patterns in the H i absorption velocity field. The asymmetry of the absorption spectra can be caused by outflows or inflows of gas in the nuclear region of NGC 4945. The continuum map shows small extensions on both sides of the galaxy’s major axis that might be signs of outflows resulting from the starburst activity.

Funder

AEI

FEDER

UE

European Regional Development Fund

European Union

Department of Science and Technology

National Research Foundation

BMBF

DFG

European Research Council

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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