Galaxy–galaxy lensing in the VOICE deep survey

Abstract

The multi-band photometry of the VOICE imaging data, overlapping with 4.9 deg2 of the Chandra Deep Field South (CDFS) area, enables both shape measurement and photometric redshift estimation to be the two essential quantities for weak lensing analysis. The depth of magAB is up to 26.1 (5σ limiting) in r-band. We estimate the excess surface density (ESD; ΔΣ) based on galaxy–galaxy measurements around galaxies at lower redshift (0.10 < zl < 0.35) while we select the background sources as those at higher redshift ranging from 0.3 to 1.5. The foreground galaxies are divided into two major categories according to their colour (blue and red), each of which has been further divided into high- and low-stellar-mass bins. The halo masses of the samples are then estimated by modelling the signals, and the posterior of the parameters are sampled using a Monte Carlo Markov chain process. We compare our results with the existing stellar-to-halo mass relation (SHMR) and find that the blue low-stellar-mass bin (median M* = 108.31 M⊙) deviates from the SHMR relation whereas the other three samples agree well with empirical curves. We interpret this discrepancy as the effect of the low star-formation efficiency of the low-mass blue dwarf galaxy population dominated in the VOICE-CDFS area.