The masses of satellites in GAMA galaxy groups from 100 square degrees of KiDS weak lensing data

TL;DR

This study measures the masses of satellite galaxy subhalos in GAMA groups using KiDS weak lensing data, revealing consistent subhalo masses and stellar mass fractions across different group-centric distances.

Contribution

It provides the first weak lensing-based satellite subhalo mass measurements in GAMA groups, accounting for data covariance and analyzing dependence on group-centric distance.

Findings

Satellite subhalo masses are approximately 10^{11.7} to 10^{12.2} solar masses.

Subhalo mass is about 1.5% of the host halo mass.

Stellar mass fractions in subhalos are around 4%.

Abstract

We use the first 100 sq. deg. of overlap between the Kilo-Degree Survey (KiDS) and the Galaxy And Mass Assembly (GAMA) survey to determine the galaxy halo mass of ~10,000 spectroscopically-confirmed satellite galaxies in massive ($M > 10^{13}h^{-1}{\rm M}_\odot$) galaxy groups. Separating the sample as a function of projected distance to the group centre, we jointly model the satellites and their host groups with Navarro-Frenk-White (NFW) density profiles, fully accounting for the data covariance. The probed satellite galaxies in these groups have total masses $\log M_{\rm sub} /(h^{-1}{\rm M}_\odot) \approx 11.7 - 12.2$ consistent across group-centric distance within the errorbars. Given their typical stellar masses, $\log M_{\rm \star,sat}/(h^{-2}{\rm M}_\odot) \sim 10.5$, such total masses imply stellar mass fractions of $M_{\rm \star,sat} /M_{\rm sub} \approx 0.04 h^{-1}$ . The average subhalo hosting these satellite galaxies has a mass $M_{\rm sub} \sim 0.015M_{\rm host}$ independent of host halo mass, in broad agreement with the expectations of structure formation in a $\Lambda$CDM universe.