Using Megamaser Disks to Probe Black Hole Accretion

TL;DR

This study investigates the alignment of megamaser disks with circumnuclear structures and jets, revealing misalignments with stellar disks but strong alignment with radio jets, shedding light on black hole fueling mechanisms.

Contribution

It provides new insights into the orientation relationships between megamaser disks, circumnuclear structures, and jets in gas-rich spiral galaxies.

Findings

Megamaser disks are misaligned with circumnuclear stellar disks.

Megamaser disk axes align with radio jets in detected galaxies.

Supports the idea of complex gas dynamics influencing black hole fueling.

Abstract

We examine the alignment between H_2O megamaser disks on sub-pc scales with circumnuclear disks and bars on <500 pc scales observed with HST/WFC3. The HST imaging reveals young stars, indicating the presence of gas. The megamaser disks are not well aligned with the circumnuclear bars or disks as traced by stars in the HST images. We speculate on the implications of the observed misalignments for fueling supermassive black holes in gas-rich spiral galaxies. In contrast, we find a strong preference for the rotation axes of the megamaser disks to align with radio continuum jets observed on >50 pc scales, in those galaxies for which radio continuum detections are available. Sub-arcsecond observations of molecular gas with ALMA will enable a more complete understanding of the interplay between circumnuclear structures.