Galaxy And Mass Assembly: Estimating galaxy group masses via caustic analysis

TL;DR

This paper introduces a modified caustic method to estimate galaxy group masses in the GAMA catalogue, calibrated on mock data, and finds it agrees well with existing dynamical estimates across various group types.

Contribution

It presents a new application and calibration of the caustic mass estimation algorithm for galaxy groups, improving mass estimates in the GAMA survey.

Findings

Caustic mass estimates agree within a factor of 2 for over 90% of groups.

The method performs well across different group sizes and mass ranges.

Calibrated on mock data, it provides reliable mass estimates for real galaxy groups.

Abstract

We have generated complementary halo mass estimates for all groups in the Galaxy And Mass Assembly Galaxy Group Catalogue (GAMA G3Cv1) using a modified caustic mass estimation algorithm, originally developed by Diaferio & Geller (1997). We calibrate the algorithm by applying it on a series of 9 GAMA mock galaxy light cones and investigate the effects of using different definitions for group centre and size. We select the set of parameters that provide median-unbiased mass estimates when tested on mocks, and generate mass estimates for the real group catalogue. We find that on average, the caustic mass estimates agree with dynamical mass estimates within a factor of 2 in 90.8 +/- 6.1% groups and compares equally well to velocity dispersion based mass estimates for both high and low multiplicity groups over the full range of masses probed by the G3Cv1.