Galaxy And Mass Assembly (GAMA): in search of Milky Way Magellanic Cloud analogues

A. S. G. Robotham*, I. K. Baldry, J. Bland-Hawthorn, S. P. Driver, J. Loveday, P. Norberg, A. E. Bauer, K. Bekki, S. Brough, M. Brown, A. Graham, A. M. Hopkins, S. Phillipps, C. Power, A. Sansom, L. Staveley-Smith

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

42 Citations (Scopus)

Abstract

Analysing all Galaxy And Mass Assembly (GAMA) galaxies within a factor of 2 (+/- 0.3 dex) of the stellar mass of the Milky Way (MW), there is a 11.9 per cent chance that one of these galaxies will have a close companion (within a projected separation of 70 kpc and radial separation of 400 km s-1) that is at least as massive as the Large Magellanic Cloud (LMC). Two close companions at least as massive as the Small Magellanic Cloud (SMC) are rare at the 3.4 per cent level. Two full analogues to the MWLMCSMC system were found in GAMA (all galaxies late-type and star-forming), suggesting that such a combination of close together, late-type, star-forming galaxies is rare: only 0.4 per cent of MW mass galaxies (in the range where we could observe both the LMC and SMC) have such a system. In summary, the MWLMCSMC system is a 2.7s event (when recast into Gaussian statistics). Using cross-correlation comparisons we find that there is a preference for SMCLMC binary pair analogues to be located within 2 Mpc of a range of different luminosity groups. There is a particular preference for such binaries to be located near Local Group luminosity systems. When these groups are subdivided into small magnitude gap and large magnitude gap subsets, the binaries prefer to be spatially associated with the small magnitude gap systems. These systems will be dynamically less evolved, but still offer the same amount of gravitational dark matter. This suggests that binaries such as the SMCLMC might be transient systems, usually destroyed during vigorous merger events. Details of a particularly striking analogue to the MWSMCLMC and M31 complex are included.

Original languageEnglish
Pages (from-to)1448-1453
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Volume424
Issue number2
DOIs
Publication statusPublished - Aug 2012

Keywords

  • galaxies: haloes
  • galaxies: kinematics and dynamics
  • Local Group
  • Magellanic Clouds
  • large-scale structure of Universe
  • LOCAL GROUP
  • PROPER-MOTION
  • SATELLITE GALAXIES
  • DWARF GALAXIES
  • STAR-FORMATION
  • POPULATION
  • CATALOG
  • HISTORY

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