Preparing for low surface brightness science with the Vera C. Rubin Observatory: characterisation of tidal features from mock images

TL;DR

This paper assesses the ability of the Vera C. Rubin Observatory to detect and characterize tidal features in galaxy outskirts using mock images, highlighting how depth and orientation influence visibility and classification accuracy.

Contribution

It provides a detailed analysis of tidal feature detectability and flux recovery in simulated images, informing strategies for low surface brightness science with the Rubin Observatory.

Findings

Approximately 80% of tidal flux detected at 10-year survey depth for Milky Way-mass galaxies.

Detection fraction decreases to 60% at shallower depths.

Higher mass galaxies show a greater fraction of flux in tidal features.

Abstract

Tidal features in the outskirts of galaxies yield unique information about their past interactions and are a key prediction of the hierarchical structure formation paradigm. The Vera C. Rubin Observatory is poised to deliver deep observations for potentially of millions of objects with visible tidal features, but the inference of galaxy interaction histories from such features is not straightforward. Utilising automated techniques and human visual classification in conjunction with realistic mock images produced using the NEWHORIZON cosmological simulation, we investigate the nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses. In our simulated sample, around 80 per cent of the flux in the tidal features around Milky Way or greater mass galaxies is detected at the 10-year depth of the Legacy Survey of Space and Time (30-31 mag / sq. arcsec), falling to 60 per cent assuming a shallower final depth of 29.5 mag / sq. arcsec. The fraction of total flux found in tidal features increases towards higher masses, rising to 10 per cent for the most massive objects in our sample (M*~10^{11.5} Msun). When observed at sufficient depth, such objects frequently exhibit many distinct tidal features with complex shapes. The interpretation and characterisation of such features varies significantly with image depth and object orientation, introducing significant biases in their classification. Assuming the data reduction pipeline is properly optimised, we expect the Rubin Observatory to be capable of recovering much of the flux found in the outskirts of Milky Way mass galaxies, even at intermediate redshifts (z<0.2).