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EP: Fachverband Extraterrestrische Physik

EP 10: Poster Session

EP 10.3: Poster

Donnerstag, 3. April 2025, 11:00–12:30, ZHG Foyer 1. OG

Water Megamasers: Rare Cosmic Beacons for Accurate SMBH Masses and Hubble Parameter Constraints — •Ahlam Farhan — Boğaziçi University, physics department, Istanbul, Turkiye

Extragalactic water vapour maser emission at 22 GHz (H2OMM) has been traced with remarkable accuracy to within a few parsecs of accretion discs around supermassive black holes (SMBHs). High-resolution VLBI observations demonstrate their ability to measure SMBH masses beyond the Milky Way and constrain the Hubble parameter to within 4% accuracy, as the Megamaser Cosmology Project (MCP) shows.

Despite these capabilities, H2OMMs are rare, with only 200 detections among over 6,000 surveyed galaxies. The complex and poorly understood physical conditions required for their formation, make it challenging to pinpoint the ideal galaxies to hunt new maser galaxies. Statistical studies are therefore crucial to identify trends that can guide future surveys toward higher detection rates.

Our study focuses on Active Galactic Nuclei (AGN) properties and highlights that galaxies with luminous dense gas tracers (e.g., HCO+, HCN) and weak 6.4 keV Fe Kα emission are more likely to host H2OMMs. These findings offer a pathway to optimise future searches, enhancing both cosmological measurements and our understanding of AGN environments.

Keywords: Water megamaser galaxies; Active Galactic Nuclei (AGN); Supermassive black holes (SMBHs); Hubble parameter; Accretion discs