Speaker
Description
The extended neutral hydrogen (HI) environments of spiral galaxies provide essential insights into galactic evolution but remain poorly characterised beyond optical boundaries. While star-forming regions define the visible galaxy extent, neutral hydrogen can extend far beyond as diffuse halos, tidal streams, and undetected gas-rich companions that significantly contribute to the total baryonic mass budget.
We present deep radio observations of three nearby spiral galaxies selected for their diverse morphological and environmental properties: NGC 7496 (barred spiral, Grus, ~18 Mpc), NGC 1512 (Horologium, ~12 Mpc), and NGC 4535 (Virgo cluster outskirts, ~16 Mpc). These systems span a range of stellar masses, star formation rates, and local environments, serving as ideal laboratories for understanding how galactic properties and external influences shape neutral hydrogen distribution.
Using low-resolution radio observations to maximise field of view and sensitivity, we reveal faint HI features invisible to previous surveys, including low surface brightness extensions, satellite galaxies below traditional detection thresholds, and diffuse circumgalactic gas clouds. Our statistical analysis quantifies both the diffuse HI component and contributions from previously undetected gas-rich companions, improving our understanding of the complete HI census around spiral galaxies and its implications for galaxy evolution models.
| Stream | Science or Engineering |
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