Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies

Davor Krajnovic; Eric Emsellem; Mark den Brok; Raffaella Anna Marino; Kasper Borello Schmidt; Matthias Steinmetz; Peter M. Weilbacher

doi:10.1093/mnras/sty1031

arXiv · 1802.02591

Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies

Davor Krajnovic·Eric Emsellem·Mark den Brok·Raffaella Anna Marino·Kasper Borello Schmidt·Matthias Steinmetz·Peter M. Weilbacher

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Abstract

We present the stellar velocity maps of 25 massive early type galaxies located in dense environments observed with MUSE. Galaxies are selected to be brighter than M_K=-25.7 magnitude, reside in the core of the Shapley Super Cluster or be the brightest galaxy in clusters richer than the Virgo Cluster. We thus targeted galaxies more massive than 10^12 Msun and larger than 10 kpc (half-light radius). The velocity maps show a large variety of kinematic features: oblate-like regular rotation, kinematically distinct cores and various types of non-regular rotation. The kinematic misalignment angles show that massive galaxies can be divided into two categories: those with small or negligible misalignment, and those with misalignment consistent with being 90 degrees. Galaxies in this latter group, comprising just under half of our galaxies, have prolate-like rotation (rotation around the major axis). Among the brightest cluster galaxies the incidence of prolate-like rotation is 50 per cent, while for a magnitude limited sub-sample of objects within the Shapley Super Cluster (mostly satellites), 35 per cent of galaxies show prolate-like rotation. Placing our galaxies on the mass - size diagram, we show that they all fall on a branch extending almost an order of magnitude in mass and a factor of 5 in size from the massive end early-type galaxies, previously recognised as associated with major dissipation-less mergers. The presence of galaxies with complex kinematics and, particularly, prolate-like rotators suggests, according to current numerical simulations, that the most massive galaxies grow predominantly through dissipation-less equal-mass mergers.

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Davor Krajnovic, Eric Emsellem, Mark den Brok, Raffaella Anna Marino, Kasper Borello Schmidt, Matthias Steinmetz, Peter M. Weilbacher. 2018-02-07. Climbing to the top of the galactic mass ladder: evidence for frequent prolate-like rotation among the most massive galaxies. https://doi.org/10.1093/mnras/sty1031

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