Investigating Galactic Fountains in M101: Insights from Ionized, UV emissions and Neutral Gas

TL;DR

This study investigates galactic fountain processes in M101 by analyzing ionized, UV, and neutral gas emissions, revealing how stellar feedback creates HI cavities and influences gas availability for star formation over tens of millions of years.

Contribution

It provides new high-resolution observations of HI holes and fountain effects in a face-on galaxy, quantifying feedback processes and their impact on gas dynamics and star formation.

Findings

Identified 20 new HI holes in M101.

Quantified the physical properties and energy balance of fountain candidates.

Demonstrated stellar feedback's role in creating HI cavities and expelling gas from the disk.

Abstract

Spiral galaxy disks are thought to exist in a quasi-stationary state, between fresh gas accretion from cosmic filaments and disk star formation, self-regulated through supernovae feedback. Our goal here is to quantify these processes and probe their efficiency. While star formation can be traced at 10 Myr time-scales through H$\alpha$ emission, the signature of OB stars, and at 100 Myr scale with UV emission, the gas surface density is traced by HI emission for the atomic phase. We choose to investigate feedback processes using fountain effects in M101, a nearby well-observed face-on galaxy. Face-on studies are very complementary to the more frequent edge-on observations of these fountains in the literature. We use high-resolution data from THINGS for the HI emission GALEX for UV, and SITELLE/SIGNALS IFU for the H$\alpha$ tracer. We have identified 20 new HI holes, in addition to the 52 holes found by Kamphuis in 1993. We study in more detail the nine holes satisfying strong criteria to be true fountain effects, compute their physical properties, and derive their energy balance. Only one small HI hole still contains H$\alpha$ and young stars inside, while the largest hole of 2.4 kpc and oldest age (94 Myr) is deprived of H$\alpha$ and UV. For face-on disks, the possibility to study simultaneously the HI shell morphology, the stellar association, and kinematic evidence is of primordial importance. In M101, we have quantified how stellar feedback is responsible for carving the observed cavities in the atomic gas disk, and how it can expel above the disk the neutral gas, which is then unavailable for star formation during up to 100 Myr.