How common are the magellanic clouds?

Lulu Liu, Brian F. Gerke, Risa H. Wechsler, Peter S. Behroozi, Michael T. Busha

Research output: Contribution to journalArticlepeer-review

104 Scopus citations


We introduce a probabilistic approach to the problem of counting dwarf satellites around host galaxies in databases with limited redshift information. This technique is used to investigate the occurrence of satellites with luminosities similar to the Magellanic Clouds around hosts with properties similar to the Milky Way (MW) in the object catalog of the Sloan Digital Sky Survey (SDSS). Our analysis uses data from SDSS Data Release 7, selecting candidate MW-like hosts from the spectroscopic catalog and candidate analogs of the Magellanic Clouds from the photometric catalog. Our principal result is the probability for an MW-like galaxy to host N sat close satellites with luminosities similar to the Magellanic Clouds. We find that 81% of galaxies like the MW have no such satellites within a radius of 150kpc, 11% have one, and only 3.5% of hosts have two. The probabilities are robust to changes in host and satellite selection criteria, background-estimation technique, and survey depth. These results demonstrate that the MW has significantly more satellites than a typical galaxy of its luminosity; this fact is useful for understanding the larger cosmological context of our home galaxy.

Original languageEnglish (US)
Article number62
JournalAstrophysical Journal
Issue number1
StatePublished - May 20 2011
Externally publishedYes


  • Local Group
  • Magellanic Clouds
  • dark matter
  • galaxies: dwarf
  • galaxies: statistics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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