# The Bluedisk survey: thickness of HI layers in gas rich spiral galaxies

**Authors:** Toky H. Randriamampandry, Jing Wang, K. Moses Mogotsi  
**arXiv:** [2105.10683](https://arxiv.org/abs/2105.10683)  
**Date:** 2021-05-22  
**Summary page:** https://www.summarizepaper.com/en/paper/2105.10683v1/

## Key points

- Study on the thickness of HI layers in gas-rich spiral galaxies using 21-cm observations
- Sample consists of galaxies from BLUEDISK, THINGS, and VIVA surveys
- Objective is to compare HI layer thickness in unusually HI-rich galaxies with normal spiral galaxies and investigate correlations with other galaxy properties
- Unusually HI-rich galaxies have similar HI disk thickness compared to control sample and THINGS/VIVA survey galaxies
- Correlation between average thickness of neutral hydrogen inside optical disk and atomic gas fraction inside optical disk, with scatter of approximately 0.22 dex
- Correlation observed between HI scale height and atomic-to-molecular gas ratio, indicating link between star formation and vertical distribution of HI
- Proposed new scaling relation between HI scale height and atomic gas fraction for predicting HI scale height in many galaxies
- Detailed information provided on sample selection, methodology (tilted ring analysis), measurement of HI scale height, and discussions on correlations with other galaxy properties
- Contributes to understanding galactic structures and their relationship with gas content and star formation processes

## Summary

This paper presents a study on the thickness of HI layers in gas-rich spiral galaxies using 21-cm observations. The sample consists of galaxies selected from the BLUEDISK, THINGS, and VIVA surveys. The main objective is to compare the thickness of the HI layer in unusually HI-rich galaxies with that of normal spiral galaxies and investigate any correlations between the HI scale height and other galaxy properties. The results show that, on average, the unusually HI-rich galaxies have similar HI disk thickness compared to the control sample and the galaxies selected from the THINGS and VIVA surveys within their uncertainties. Additionally, a correlation is found between the average thickness of neutral hydrogen inside the optical disk and the atomic gas fraction inside the optical disk, with a scatter of approximately 0.22 dex. Furthermore, a correlation is observed between the HI scale height and the atomic-to-molecular gas ratio, indicating a link between star formation and the vertical distribution of HI. This finding is consistent with previous studies. The authors propose a new scaling relation between the HI scale height and atomic gas fraction which can be used to predict the HI scale height of a large number of galaxies. The paper provides detailed information on sample selection, methodology (including tilted ring analysis), measurement of HI scale height, and discussions on correlations with other galaxy properties. Overall, this study contributes to our understanding of galactic structures and their relationship with gas content and star formation processes.