Galaxy-galaxy lensing in the VOICE deep survey

TL;DR

This study measures galaxy-galaxy lensing in the VOICE survey to estimate halo masses and compare them with known stellar-to-halo mass relations, revealing a deviation for low-mass blue galaxies likely due to low star formation efficiency.

Contribution

First measurement of galaxy-galaxy lensing in the VOICE survey, providing insights into halo masses and stellar-to-halo mass relation for different galaxy populations.

Findings

Blue low-mass galaxies deviate from the SHMR.

Most galaxy samples agree with empirical SHMR curves.

Low star formation efficiency observed in low-mass blue dwarf galaxies.

Abstract

The multi-band photometry of the VOICE imaging data, overlapping with 4.9 deg$^2$ 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 $mag_{AB}$ is up to 26.1 (5$\sigma$ limiting) in $r$-band. We estimate the Excess Surface Density (ESD; $\Delta\Sigma$) based on galaxy-galaxy measurements around galaxies at lower redshift (0.10<$z_l$<0.35) while we select the background sources to be at higher redshift ranging from 0.3 to 1.5. The foreground galaxies are divided into two major categories according to their colour (blue/red), each of which has been further divided into high/low stellar mass bins. Then the halo masses of the samples are estimated by modelling the signals, and the posterior of the parameters are samples via Mote Carlo Markov Chain (MCMC) process. We compare our results with the existing Stellar-to-Halo Mass Relation (SHMR) and find that the blue low stellar mass bin (median $M_*=10^{8.31}M_\odot$) deviates from the SHMR relation whereas all other three samples agrees well with empirical curves. We interpret this discrepancy as the effect of a low star formation efficiency of the low-mass blue dwarf galaxy population dominated in the VOICE-CDFS area.