Made-to-measure galaxy modelling utilising absorption line strength data

TL;DR

This paper extends the made-to-measure (M2M) particle method to simultaneously model stellar kinematics and absorption line strength data, demonstrating its effectiveness on four galaxies and opening avenues for more comprehensive galaxy modeling.

Contribution

The paper introduces a chemo-M2M method that integrates absorption line strength data into the M2M framework, enabling 3D distribution analysis of galaxy properties.

Findings

Successfully reproduces 2D line strength data with mean chi^2 ~1

Achieves >95% particle weight convergence

Provides plausible 3D line strength distributions

Abstract

We enhance the Syer & Tremaine made-to-measure (M2M) particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data thus creating a `chemo-M2M' modelling scheme. We apply the enhanced method to four galaxies (NGC 1248, NGC 3838, NGC 4452, NGC 4551) observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean chi^2 per bin values of ~1 with >95\% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these distributions are plausible representations of real galaxies requires further consideration. Overall we consider the modelling exercise to be a promising first step in developing a `chemo-M2M' modelling system and in understanding some of the issues to be addressed. Whilst the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.