Major substructure in the M31 outer halo: The south-west cloud

N. F. Bate; A. R. Conn; B. McMonigal; G. F. Lewis; N. F. Martin; A. W. McConnachie; J. Veljanoski; A. D. Mackey; A. M.N. Ferguson; R. A. Ibata; M. J. Irwin; M. Fardal; A. P. Huxor; A. Babul

doi:10.1093/mnras/stt2139

Major substructure in the M31 outer halo: The south-west cloud

N. F. Bate^*, A. R. Conn, B. McMonigal, G. F. Lewis, N. F. Martin, A. W. McConnachie, J. Veljanoski, A. D. Mackey, A. M.N. Ferguson, R. A. Ibata, M. J. Irwin, M. Fardal, A. P. Huxor, A. Babul

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

21 Citations (Scopus)

Abstract

We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo ofM31. The South-West Cloud lies at a projected distance of ̃100 kpc from the centre of M31 and extends for at least ̃50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793⁺⁴⁵_-45 kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 ± 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 ± 0.15. We measure a brightness for the Cloud of MV = -12.1 mag; this is ̃75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.

Original language	English
Pages (from-to)	3362-3372
Number of pages	11
Journal	Monthly Notices of the Royal Astronomical Society
Volume	437
Issue number	4
DOIs	https://doi.org/10.1093/mnras/stt2139
Publication status	Published - Feb 2014

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Bate, N. F., Conn, A. R., McMonigal, B., Lewis, G. F., Martin, N. F., McConnachie, A. W., Veljanoski, J., Mackey, A. D., Ferguson, A. M. N., Ibata, R. A., Irwin, M. J., Fardal, M., Huxor, A. P., & Babul, A. (2014). Major substructure in the M31 outer halo: The south-west cloud. Monthly Notices of the Royal Astronomical Society, 437(4), 3362-3372. https://doi.org/10.1093/mnras/stt2139

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abstract = "We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo ofM31. The South-West Cloud lies at a projected distance of{\~ }100 kpc from the centre of M31 and extends for at least{\~ }50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793+45-45 kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 ± 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 ± 0.15. We measure a brightness for the Cloud of MV = -12.1 mag; this is{\~ }75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.",

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T2 - The south-west cloud

AU - Bate, N. F.

AU - Conn, A. R.

AU - McMonigal, B.

AU - Lewis, G. F.

AU - Martin, N. F.

AU - McConnachie, A. W.

AU - Veljanoski, J.

AU - Mackey, A. D.

AU - Ferguson, A. M.N.

AU - Ibata, R. A.

AU - Irwin, M. J.

AU - Fardal, M.

AU - Huxor, A. P.

AU - Babul, A.

PY - 2014/2

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N2 - We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo ofM31. The South-West Cloud lies at a projected distance of ̃100 kpc from the centre of M31 and extends for at least ̃50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793+45-45 kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 ± 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 ± 0.15. We measure a brightness for the Cloud of MV = -12.1 mag; this is ̃75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.

AB - We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo ofM31. The South-West Cloud lies at a projected distance of ̃100 kpc from the centre of M31 and extends for at least ̃50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793+45-45 kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 ± 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 ± 0.15. We measure a brightness for the Cloud of MV = -12.1 mag; this is ̃75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.

KW - Galaxies

KW - Individual

KW - M31-Local Group-galaxies

KW - Stellar content.

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DO - 10.1093/mnras/stt2139

M3 - Article

SN - 0035-8711

VL - 437

SP - 3362

EP - 3372

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 4

ER -

Major substructure in the M31 outer halo: The south-west cloud

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