A Dearth of Dark Matter in Ordinary Elliptical Galaxies
Aaron J. Romanowsky,1,2*
Nigel G. Douglas,2
Magda Arnaboldi,3,4
Konrad Kuijken,5,2
Michael R. Merrifield,1
Nicola R. Napolitano,2
Massimo Capaccioli,3,6
Kenneth C. Freeman7
The kinematics of the outer parts of three intermediate-luminosity
elliptical galaxies were studied with the Planetary Nebula Spectrograph.
The galaxies' velocity-dispersion profiles were found to decline
with the radius, and dynamical modeling of the data indicates
the presence of little if any dark matter in these galaxies'
halos. This unexpected result conflicts with findings in other
galaxy types and poses a challenge to current galaxy formation
theories.
2 Kapteyn Astronomical Institute, Post Office Box 800, 9700 AV Groningen, Netherlands.
3 Istituto Nazionale di Astrofisica (INAF)–Astronomical Observatory of Capodimonte, via Moiariello 16, I–80131 Naples, Italy.
4 INAF-Astronomical Observatory of Pino Torinese, via Osservatorio 20, I–10025 Pino Torinese, Italy.
5 Leiden Observatory, Post Office Box 9513, 2300 RA Leiden, Netherlands.
6 Department of Physical Sciences, University Federico II, I–80126 Naples, Italy.
7 Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia.
* To whom correspondence should be addressed. E-mail: aaron.romanowsky{at}nottingham.ac.uk
