# The nature of H$\alpha$-selected galaxies along the large-scale structure at z=0.4 revealed by Subaru Hyper Suprime-Cam survey

## TL;DR

This study investigates how galaxy properties like color, mass, and star formation activity vary with environment at z=0.4, using H-alpha-selected galaxies from Subaru HSC data, revealing environmental influences on galaxy evolution.

## Contribution

It provides new insights into environmental effects on star-forming galaxies at z=0.4 using H-alpha selection and Subaru HSC data, highlighting the role of dense environments.

## Key findings

- Redder galaxy colors in denser environments.
- Possible color-density and color-radius correlations.
- Enhanced star formation rates in high-density regions.

## Abstract

We present the environmental dependence of colour, stellar mass, and star formation (SF) activity in H-alpha-selected galaxies along the large-scale structure at z=0.4 hosting twin clusters in DEEP2-3 field, discovered by Subaru Strategic Programme of Hyper Suprime-Cam (HSC SSP). By combining photo-z selected galaxies and H-alpha emitters selected with broad-band and narrow-band (NB) data of the recent data release of HSC SSP (DR1), we confirm that galaxies in higher-density environments or galaxies in the cluster central regions show redder colours. We find that there still remains a possible colour-density and colour-radius correlation even if we restrict the sample to H-alpha-selected galaxies, likely due to the presence of massive H-alpha emitters in denser regions. We also find a hint of increased star formation rates (SFR) amongst H-alpha emitters towards the highest-density environment, again primarily driven by the excess of red/massive H-alpha emitters in high-density environment, while their specific SFR does not significantly change with environment. This work demonstrates the power of the HSC SSP NB data to study SF galaxies across environment in the distant universe.