Galaxy structure with strong gravitational lensing: decomposing the internal mass distribution of massive elliptical galaxies

Nightingale, J.W.; Massey, R.J.; Harvey, D.R.; Cooper, A.P.; Etherington, A.; Tam, S.-I.; Hayes, R.G.

Abstract

We investigate how strong gravitational lensing can test contemporary models of massive elliptical (ME) galaxy formation, by combining a traditional decomposition of their visible stellar distribution with a lensing analysis of their mass distribution. As a proof of concept, we study a sample of three ME lenses, observing that all are composed of two distinct baryonic structures, a ‘red’ central bulge surrounded by an extended envelope of stellar material. Whilst these two components look photometrically similar, their distinct lensing effects permit a clean decomposition of their mass structure. This allows us to infer two key pieces of information about each lens galaxy: (i) the stellar mass distribution (without invoking stellar populations models) and (ii) the inner dark matter halo mass. We argue that these two measurements are crucial to testing models of ME formation, as the stellar mass profile provides a diagnostic of baryonic accretion and feedback whilst the dark matter mass places each galaxy in the context of LCDM large scale structure formation. We also detect large rotational offsets between the two stellar components and a lopsidedness in their outer mass distributions, which hold further information on the evolution of each ME. Finally, we discuss how this approach can be extended to galaxies of all Hubble types and what implication our results have for studies of strong gravitational lensing.

Citation

Nightingale, J., Massey, R., Harvey, D., Cooper, A., Etherington, A., Tam, S.-I., & Hayes, R. (2019). Galaxy structure with strong gravitational lensing: decomposing the internal mass distribution of massive elliptical galaxies. Monthly Notices of the Royal Astronomical Society, 489(2), 2049-2068. https://doi.org/10.1093/mnras/stz2220

• Journal Article Type: Article
• Acceptance Date: Jun 29, 2019
• Online Publication Date: Aug 16, 2019
• Publication Date: Oct 30, 2019
• Deposit Date: Jun 25, 2019
• Publicly Available Date: Aug 20, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 489
• Issue: 2
• Pages: 2049-2068
• DOI: https://doi.org/10.1093/mnras/stz2220
• Public URL: https://durham-repository.worktribe.com/output/1328069