over the massive group or cluster galaxies, and the radial effect becomes more effective in less massive galaxies. The results support mergers and/or starvation as the main quenching mechanisms in the group environment, while harassment and/or starvation dominate in clusters.'
author:
- 'Hung-Yu Jian'
- Lihwai Lin
- 'Kai-Yang Lin'
- Sebastien Foucaud
- 'Chin-Wei Chen'
- Tzihong Chiueh
- 'R. G. Bower'
- Shaun Cole
- 'Wen-Ping Chen'
- 'W. S. Burgett'
- 'P. W. Draper'
- 'H. Flewelling'
- 'M. E. Huber'
- 'N. Kaiser'
- 'R.-P. Kudritzki'
- 'E. A. Magnier'
- 'N. Metcalfe'
- 'R. J. Wainscoat'
- 'C. Waters'
title: 'The Pan-STARRS1 Medium-deep Survey: Star Formation Quenching in Group and Cluster Environments'
---

Introduction
============

Galaxy properties exhibit strong correlations with their stellar mass ($M_{*}$) and hosting environments [@dre80; @coo07; @ger07; @pen10; @muz12; @wet12]. Galaxies in denser environments tend to be older, redder, and less strongly star-forming. However, more massive galaxies also have a tendency to be older, redder, and have less strongly star-forming active star formation [@bal06; @pen10]. The debate about the extent to which the properties of galaxies are determined by external processes (environmental quenching, associated with a galaxy being accreted by a 