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The Andromeda Galaxy’s Last Major Merger: Constraints from the survey of Planetary Nebulae

Published online by Cambridge University Press:  13 February 2024

Souradeep Bhattacharya Open the ORCID record for Souradeep Bhattacharya [Opens in a new window] ,
Magda Arnaboldi Open the ORCID record for Magda Arnaboldi [Opens in a new window] ,
Ortwin Gerhard Open the ORCID record for Ortwin Gerhard [Opens in a new window] ,
Nelson Caldwell ,
Chiaki Kobayashi Open the ORCID record for Chiaki Kobayashi [Opens in a new window] ,
Francois Hammer ,
Yanbin Yang ,
Kenneth C. Freeman ,
Johanna Hartke  and
Alan McConnachie
Souradeep Bhattacharya*
Affiliation:
Inter University Centre for Astronomy and Astrophysics, Ganeshkhind, Post Bag 4, Pune 411007, India
Magda Arnaboldi
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Ortwin Gerhard
Affiliation:
Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
Nelson Caldwell
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Chiaki Kobayashi
Affiliation:
University of Hertfordshire, Astronomy and Mathematics, College Lane, Hatfield AL10 9AB, UK
Francois Hammer
Affiliation:
GEPI, Observatoire de Paris, Université PSL, CNRS, Place Jules Janssen, F-92195 Meudon, France
Yanbin Yang
Affiliation:
GEPI, Observatoire de Paris, Université PSL, CNRS, Place Jules Janssen, F-92195 Meudon, France
Kenneth C. Freeman
Affiliation:
Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, ACT 2611 Weston Creek, Australia
Johanna Hartke
Affiliation:
Finnish Centre for Astronomy with ESO (FINCA), University of Turku, FI-20014 Turku, Finland
Alan McConnachie
Affiliation:
NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
*
email: souradeep@iucaa.in
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Abstract

The Andromeda galaxy (M 31) has experienced a tumultuous merger history as evidenced by the many substructures present in its inner halo. We use planetary nebulae (PNe) as chemodynamic tracers to shed light on the recent merger history of M 31. We identify the older dynamically hotter thicker disc in M 31 and a distinct younger dynamically colder thin disc. The two discs are also chemically distinct with the PN chemodynamics implying their formation in a ‘wet’ major merger (mass ratio ∼ 1:5) ∼ 2.5–4.5 Gyr ago. From comparison of PN line-of-sight velocities in the inner halo substructures with predictions of a major-merger model in M 31, we find that the same merger event that formed the M 31 thick and thin disc is also responsible for forming these substructures. We thereby obtain constraints on the recent formation history of M 31 and the properties of its cannibalized satellite.

Keywords

galaxies: abundancesgalaxies: individual (M31)galaxies: kinematics and dynamicsgalaxies: structureplanetary nebulae: general
Type
Contributed Paper
Information
Proceedings of the International Astronomical Union , Volume 18 , Symposium S377: Early Disk-Galaxy Formation from JWST to the Milky Way , December 2022 , pp. 123 - 126
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Copyright
© The Author(s), 2024. Published by Cambridge University Press on behalf of International Astronomical Union

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References

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