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

Abstract

We use the first 100 deg 2 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 M ) 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 sub /(h −1 M ) ≈ 11.7 − 12.2 consistent across group-centric distance within the errorbars. Given their typical stellar masses, log M ,sat /(h −2 M ) ∼ 10.5, such total masses imply stellar mass fractions of M ,sat /M sub ≈ 0.04 h −1 . The average subhalo hosting these satellite galaxies has a mass M sub ∼ 0.015M host independent of host halo mass, in broad agreement with the expectations of structure formation in a ΛCDM universe.

A unified model for the spatial and mass distribution of subhaloes

“…Li et al 2013Li et al , 2014Li et al , 2015Sifón et al 2015). Because stellar mass is most directly related to the infall mass of its host subhalo, such measurements essentially constrain the mass of subhaloes selected at fixed infall mass.…”

“…However, a full investigation which would have to consider many issues is beyond the scope of this paper. For example, the observational selection function is more complicated than we have assumed and involves selection in host halo mass (Sifón et al 2015) and redshift. Systematic uncertainties in stellar mass estimates may also introduce bias in the mass ratio as well as complicating the selection function.…”

Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2of KiDS weak lensing data

“…However, at R > 200 h −1 kpc the GGL signal changes significantly with the addition of satellite galaxies to the stack. Where the ESD profiles of lens samples without satellites drop sharply, the profiles of samples with satellites does not, due to the off-set contribution of the satellites' host haloes (also seen in Sifón et al 2015). These changes in the ESD profile imply that, as the contributions from different group members are added to the stacked signal, we need to model these different components to account for the total lensing signal.…”

“…Each stacked satellite adds a host contribution at its respective projected distance R sat to the group central, such that the total host contribution is integrated over the number distribution n(R sat ) (see Sifón et al 2015 for a more detailed description). The two ESD components related to satellite galaxies are multiplied by the satellite fraction f sat : the fraction of satellites with respect to the total number of galaxies (including satellites, centrals and non-group galaxies).…”

“…To select foreground galaxies, we use the spectroscopic Galaxy And Mass Assembly survey (Driver et al 2011), whereas the images of the background galaxies are taken from the photometric KiloDegree Survey (de Jong et al 2013). This combination of data sets was also employed by the GGL studies of Viola et al (2015) to measure the masses of galaxy groups, Sifón et al (2015) to study group satellites, and van Uitert et al (2016) to measure the stellarto-halo mass relation. To infer the mass of the haloes associated with the lens galaxies, we employ a simple halo model on the measured GGL signals.…”