Measures of galaxy environment - I. What is ‘environment’?

The influence of a galaxy's environment on its evolution has been studied and compared extensively in the literature, although differing techniques are often used to define environment. Most methods fall into two broad groups: those that use nearest neighbours to probe the underlying density field and those that use fixed apertures. The differences between the two inhibit a clean comparison between analyses and leave open the possibility that, even with the same data, different properties are actually being measured. In this work, we apply 20 published environment definitions to a common mock galaxy catalogue constrained to look like the local Universe. We find that nearest-neighbour-based measures best probe…

• NR
  National Research Foundation
• DG
  Danmarks Grundforskningsfond
• SA
  Smithsonian Astrophysical Observatory
• SA
  Science and Technology Facilities Council