A precise benchmark for cluster scaling relations: Fundamental Plane, Mass Plane, and IMF in the Coma cluster from dynamical models

Monthly Notices of the Royal Astronomical Society, vol. 494, pp. 5619–5635

Abstract

ABSTRACT We study a sample of 148 early-type galaxies in the Coma cluster using SDSS photometry and spectra, and calibrate our results using detailed dynamical models for a subset of these galaxies, to create a precise benchmark for dynamical scaling relations in high-density environments. For these galaxies, we successfully measured global galaxy properties, modelled stellar populations, and created dynamical models, and support the results using detailed dynamical models of 16 galaxies, including the two most massive cluster galaxies, using data taken with the SAURON IFU. By design, the study provides minimal scatter in derived scaling relations due to the small uncertainty in the relative distances of galaxies compared to the cluster distance. Our results demonstrate low (≤55 per cent for 90th percentile) dark matter fractions in the inner 1Re of galaxies. Owing to the study design, we produce the tightest, to our knowledge, IMF–σe relation of galaxies, with a slope consistent with that seen in local galaxies. Leveraging our dynamical models, we transform the classical Fundamental Plane of the galaxies to the Mass Plane. We find that the coefficients of the Mass Plane are close to predictions from the virial theorem, and have significantly lower scatter compared to the Fundamental Plane. We show that Coma galaxies occupy similar locations in the (M*–Re) and (M*−σe) relations as local field galaxies but are older. This, and the fact we find only three slow rotators in the cluster, is consistent with the scenario of hierarchical galaxy formation and expectations of the kinematic morphology–density relation.

Authors 7

1. Shravan Shetty corresponding

   Peking University

   Affiliation as printed

   Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China

2. Michele Cappellari

   University of Oxford

   Affiliation as printed

   Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK

3. Richard M. McDermid

   Macquarie University

   Affiliation as printed

   Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia

4. Davor Krajnović

   Leibniz Institute for Astrophysics Potsdam

   Affiliation as printed

   Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany

5. P. T. de Zeeuw Aachen Sterrewacht Leiden

   Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory

   Affiliation as printed

   Max-Planck-Institut für Extraterrestrische Physik, D-85741 Giessenbachstraβe, Germany

   Sterrewacht Leiden, Leiden University, Postbus 9513, NL-2300 RA Leiden, the Netherlands

6. Roger L. Davies

   University of Oxford

   Affiliation as printed

   Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK

7. Chiaki Kobayashi

   University of Hertfordshire

   Affiliation as printed

   Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK