Submitted on May 30, 2003
Accepted on August 19, 2003
A Dearth of Dark Matter in Ordinary Elliptical Galaxies
Aaron J. Romanowsky 1*,
Nigel G. Douglas 2,
Magda Arnaboldi 3,
Konrad Kuijken 4,
Michael R. Merrifield 5,
Nicola R. Napolitano 2,
Massimo Capaccioli 6,
Kenneth C. Freeman 7
1 School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands.
2 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands.
3 INAF-Astronomical Observatory of Capodimonte, via Moiariello 16, I-80131 Naples, Italy; INAF-Astronomical Observatory of Pino Torinese, via Osservatorio 20, I-10025 Pino Torinese, Italy.
4 Leiden Observatory, Postbus 9513, 2300 RA Leiden, The Netherlands; Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands.
5 School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
6 INAF-Astronomical Observatory of Capodimonte, via Moiariello 16, I-80131 Naples, Italy; Department of Physical Sciences, University "Federico II", Naples, Italy.
7 Research School of Astronomy & Astrophysics, Mt. Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia.
* To whom correspondence should be addressed. E-mail: aaron.romanowsky{at}nottingham.ac.uk..
The kinematics of the outer parts of three intermediate-luminosity elliptical galaxies have been studied using the Planetary Nebula Spectrograph. The galaxies' velocity dispersion profiles are found to decline with radius; dynamical modeling of the data indicate the presence of little if any dark matter in these galaxies' halos. This surprising result conflicts with findings in other galaxy types, and poses a challenge to current galaxy formation theories.
