# A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).XIV. The main sequence relation in a rich environment down to M_star ~ 10^6 Mo

**Authors:** A. Boselli, M. Fossati, J. Roediger, M. Boquien, M. Fumagalli, M. Balogh, S. Boissier, J. Braine, L. Ciesla, P. Côté, J. C. Cuillandre, L. Ferrarese, G. Gavazzi, S. Gwyn,  Junais, G. Hensler, A. Longobardi, M. Sun  
**arXiv:** [2211.01821](https://arxiv.org/abs/2211.01821)  
**Date:** 2022-11-03  
**Summary page:** https://www.summarizepaper.com/en/paper/2211.01821v1/

## Key points

- Study focuses on analysis of Hα fluxes for 384 star-forming galaxies detected during VESTIGE survey
- Investigates scaling relations for complete sample of galaxies in rich environment
- Explores entire dynamic range of Hα luminosity function, from massive to dwarf systems
- Main objective is to examine Main Sequence (MS) relation for all star-forming galaxies within one virial radius of Virgo cluster
- Dispersion in MS relation within rich environment is approximately three times larger than in other samples
- Strong connection found between dispersion and amount of HI gas available
- Gas-poor systems located below objects with similar stellar mass but normal HI content
- Slope (a) of 0.92, intercept (b) of -1.57, and scatter (~0.40) derived for MS relation when considering unperturbed galaxies with normal HI gas content
- Violent and active stripping processes, like ram-pressure stripping, can reproduce observed scatter in MS relation, ruling out milder processes like starvation as significant contributors
- Star-forming regions formed in stripped material outside perturbed galaxies located above MS relation drawn by unperturbed systems
- These regions undergo starburst phase before transitioning into quiescent systems

## Summary

This study focuses on the analysis of Hα fluxes for 384 star-forming galaxies detected during the VESTIGE survey. The authors investigate several important scaling relations for a complete sample of galaxies in a rich environment, taking advantage of the extraordinary sensitivity of the data. This allows them to explore the entire dynamic range of the Hα luminosity function, ranging from massive systems with stellar masses around 10^11 times that of the Sun (M*) to dwarf systems with stellar masses around 10^6 times that of the Sun (M*). The main objective is to examine the Main Sequence (MS) relation for all star-forming galaxies within one virial radius of the Virgo cluster. The MS relation represents a correlation between stellar mass and star formation rate (SFR) and is commonly observed in nearby samples of isolated objects. However, in this study, it is found that the dispersion in the MS relation within this rich environment is approximately three times larger than in other samples. The authors also find a strong connection between this dispersion and the amount of HI gas available. Gas-poor systems are located significantly below objects with similar stellar mass but normal HI content. When considering unperturbed galaxies with normal HI gas content, they derive a slope (a) of 0.92, an intercept (b) of -1.57, and a scatter (~0.40) for the MS relation. To further understand these observational results, they compare them to predictions from models. It is determined that only violent and active stripping processes, such as ram-pressure stripping that removes gas from galactic discs and quenches star formation on short timescales (<1 billion years), can reproduce the observed scatter in the MS relation. This rules out milder processes like starvation as significant contributors. This interpretation aligns with the position of galaxies with different levels of star formation activity and gas content within phase-space diagrams. Additionally, the study reveals that star-forming regions formed in stripped material outside perturbed galaxies are located above the MS relation drawn by unperturbed systems. These HII regions, which may be responsible for compact sources typically found in rich environments, undergo a starburst phase lasting less than 50 million years before transitioning into quiescent systems. Overall, this research provides valuable insights into the Main Sequence relation and its dispersion within a rich environment.