Sizes, Colour gradients and Resolved Stellar Mass Distributions for the Massive Cluster Galaxies in XMMUJ2235-2557 at z = 1.39

Jeffrey C. C. Chan; Alessandra Beifiori; J. Trevor Mendel; Roberto P. Saglia; Ralf Bender; Matteo Fossati; Audrey Galametz; Michael Wegner; David J. Wilman; Michele Cappellari; Roger L. Davies; Ryan C. W. Houghton; Laura J. Prichard; Ian J. Lewis; Ray Sharples; John P. Stott

doi:10.1093/mnras/stw502

paper

Sizes, Colour gradients and Resolved Stellar Mass Distributions for the Massive Cluster Galaxies in XMMUJ2235-2557 at z = 1.39

arXiv:1603.00468 · doi:10.1093/mnras/stw502

Abstract

We analyse the sizes, colour gradients, and resolved stellar mass distributions for 36 massive and passive galaxies in the cluster XMMUJ2235-2557 at z=1.39 using optical and near-infrared Hubble Space Telescope imaging. We derive light-weighted Sérsic fits in five HST bands ( $i_{775}, z_{850}, Y_{105}, J_{125}, H_{160}$ ), and find that the size decreases by ~20% going from $i_{775}$ to $H_{160}$ band, consistent with recent studies. We then generate spatially resolved stellar mass maps using an empirical relationship between $M_{*} / L_{H_{160}}$ and $(z_{850} - H_{160})$ and use these to derive mass-weighted Sérsic fits: the mass-weighted sizes are ~41% smaller than their rest-frame $r$ -band counterparts compared with an average of ~12% at z~0. We attribute this evolution to the evolution in the $M_{*} / L_{H_{160}}$ and colour gradient. Indeed, as expected, the ratio of mass-weighted to light-weighted size is correlated with the $M_{*} / L$ gradient, but is also mildly correlated with the mass surface density and mass-weighted size. The colour gradients $(\nabla_{z - H})$ are mostly negative, with a median value of $\sim 0.45$ mag dex $^{- 1}$ , twice the local value. The evolution is caused by an evolution in age gradients along the semi-major axis ( $a$ ), with $\nabla_{a g e} = d lo g (a g e) / d lo g (a)$ $\sim - 0.33$ , while the survival of weaker colour gradients in old, local galaxies implies that metallicity gradients are also required, with $\nabla_{Z} = d lo g (Z) / d lo g (a)$ $\sim - 0.2$ . This is consistent with recent observational evidence for the inside-out growth of passive galaxies at high redshift, and favours a gradual mass growth mechanism, such as minor mergers.

arXiv comment30 pages, 25 figures, 4 tables, accepted for publication in MNRAS

Sizes, Colour gradients and Resolved Stellar Mass Distributions for the Massive Cluster Galaxies in XMMUJ2235-2557 at z = 1.39

Abstract

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