The SAMI Galaxy Survey: the intrinsic shape of kinematically selected galaxies

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Foster, C., van de Sande, J., D'Eugenio, F., Cortese, L., McDermid, R. M., Bland-Hawthorn, J., Brough, S., Bryant, J., Croom, S. M., Goodwin, M., Konstantopoulos, I. S., Lawrence, J., López-Sánchez, Ã. R., Medling, A. M., Owers, M. S., Richards, S. N., Scott, N., Taranu, D. S., Tonini, C., Zafar, T.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Royal Astronomical Society 2017
• Subjects: galaxies: fundamental parameters – galaxies: kinematics and dynamics; sami
• Online Access: https://doi.org/10.1093/mnras/stx1869

Using the stellar kinematic maps and ancillary imaging data from the Sydney AAO Multi Integral field (SAMI) Galaxy Survey, the intrinsic shape of kinematically selected samples of galaxies is inferred. We implement an efficient and optimized algorithm to fit the intrinsic shape of galaxies using an established method to simultaneously invert the distributions of apparent ellipticities and kinematic misalignments. The algorithm output compares favourably with previous studies of the intrinsic shape of galaxies based on imaging alone and our re-analysis of the ATLAS^(3D) data. Our results indicate that most galaxies are oblate axisymmetric. We show empirically that the intrinsic shape of galaxies varies as a function of their rotational support as measured by the 'spin' parameter proxy Λ_(Re). In particular, low-spin systems have a higher occurrence of triaxiality, while high-spin systems are more intrinsically flattened and axisymmetric. The intrinsic shape of galaxies is linked to their formation and merger histories. Galaxies with high-spin values have intrinsic shapes consistent with dissipational minor mergers, while the intrinsic shape of low-spin systems is consistent with dissipationless multimerger assembly histories. This range in assembly histories inferred from intrinsic shapes is broadly consistent with expectations from cosmological simulations. © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 July 19; Received 2017 July 19; in original form 2017 March 13; Published: 08 September 2017. We thank R. Davies for insightful discussions. The SAMI Galaxy Survey is based on observations made at the Anglo-Australian Telescope. The Sydney-AAO Multi-object Integral field spectrograph (SAMI) was developed jointly by the University of Sydney and the Australian Astronomical Observatory. The SAMI input catalogue is based on data taken from the Sloan Digital Sky Survey, the GAMA Survey and the VST ATLAS Survey. The SAMI Galaxy Survey is funded by ...