Evidence of a pure starburst nature of the nuclear region of NGC 253

TL;DR

This study uses high-resolution radio observations to show that the nuclear region of NGC 253 is dominated by starburst activity rather than an active galactic nucleus, based on water maser emissions and lack of compact continuum sources.

Contribution

The paper provides new high-resolution VLBI and VLA data demonstrating the starburst nature of NGC 253's nucleus and challenges previous assumptions of an active nucleus.

Findings

Water masers are linked to star formation, not an active nucleus.

No compact continuum emission detected at milliarcsecond scales.

Supports the starburst-only model for NGC 253's nuclear region.

Abstract

We present high-resolution spectral line and continuum VLBI and VLA observations of the nuclear region of NGC 253 at 22 GHz. While the water vapor masers in this region were detected on arcsecond and milliarcsecond scales, we could not detect any compact continuum emission with a 5 sigma upper limit of ~ 1 mJy. The observations reveal that the water maser emission is not related to a possible low-luminosity active galactic nucleus but is almost certainly associated with star-formation activity. Not detecting any compact continuum source on milliarcsecond scales also questions the presence of a - previously assumed - active nucleus in NGC 253.