The HI distribution in the outskirts of M33 with the ALFALFA survey

TL;DR

This study analyzes ALFALFA survey data to identify and characterize high velocity HI clouds around M33, revealing a diverse population and an extended HI complex, contributing to understanding galaxy gas accretion.

Contribution

It provides the first detailed analysis of high velocity HI clouds around M33 using ALFALFA data, highlighting their properties and potential role in galaxy evolution.

Findings

Detected a population of HI clouds with masses 4x10^4 to a few 10^6 M_sun

Identified an extended HI complex at anomalous velocities

Estimated total neutral hydrogen mass of about 10^7 M_sun

Abstract

Spiral galaxies appear to be dynamical systems whose disks are still forming at the current epoch and which continue to accrete mass. The presence of extraplanar gas in spirals indicates that galactic halos can contain at least part of the material needed to fuel the star formation activity in their disks. Here we present the analysis of the ALFALFA survey data in the region of M33 aimed at searching high velocity clouds around this Local Group galaxy. We find a varied population of HI clouds with masses ranging between 4 x 10^4 and few times 10^6 M_sun. We also detect an extended HI complex at anomalous velocities, whose extragalactic nature cannot be firmly established. We estimate that the total amount of neutral hydrogen mass associated to these clouds is around 10^7 M_sun.