# A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

Jesse Van De Sande, Nicholas Scott, Joss Bland-Hawthorn, Sarah Brough, Julia J. Bryant, Matthew Colless, Luca Cortese, Scott M. Croom, Francesco Deugenio, Caroline Foster, Michael Goodwin, Iraklis S. Konstantopoulos, Jon S. Lawrence, Richard M. McDermid, Anne M. Medling, Matt S. Owers, Samuel N. Richards, Rob Sharp

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

## Abstract

Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum 1-3 . A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics 4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions 5 . With the rise of large multi-object integral field spectroscopic surveys, such as SAMI 6 and MaNGA 7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8 ), CALIFA 9, MASSIVE 10 ), it is now feasible to connect a galaxy′s star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment 4,11,12 . Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, $${\boldsymbol{\epsilon}}-{{\boldsymbol{e}}}$$ Iμ e) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.

Original language English 483-488 6 Nature Astronomy 2 6 https://doi.org/10.1038/s41550-018-0436-x Published - 1 Jun 2018

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