# The ALMA view of W33A: A Spiral Filament Feeding the Candidate Disc in MM1-Main

## TL;DR

This study uses ALMA observations to investigate the complex structures and potential disc feeding mechanisms in the massive star-forming region W33A MM1-Main, revealing filamentary inflows and unresolved multiplicity.

## Contribution

It provides high-resolution ALMA data showing filamentary structures feeding a potential disc around a massive young stellar object, with insights into the kinematics and multiplicity.

## Key findings

- Detection of a spiral filament feeding the central object.
- Complex kinematic signatures inconsistent with simple Keplerian rotation.
- Evidence suggesting possible unresolved binary or multiple system.

## Abstract

We targeted the massive star forming region W33A using the Atacama Large Sub/Millimeter Array (ALMA) in band 6 (230 GHz) and 7 (345 GHz) to search for a sub-1000au disc around the central O-type massive young stellar object (MYSO) W33A MM1-Main. Our data achieves a resolution of ~0.2" (~500au) and resolves the central core, MM1, into multiple components and reveals complex and filamentary structures. There is strong molecular line emission covering the entire MM1 region. The kinematic signatures are inconsistent with only Keplerian rotation although we propose that the shift in the emission line centroids within ~1000au of MM1-Main could hint at an underlying compact disc with Keplerian rotation. We cannot however rule out the possibility of an unresolved binary or multiple system. A putative smaller disc could be fed by the large scale spiral `feeding filament' we detect in both gas and dust emission. We also discuss the nature of the now-resolved continuum sources.