Napolitano, NR and Romanowsky, AJ and Capaccioli, M and Douglas, NG and Arnaboldi, M and Coccato, L and Gerhard, O and Kuijken, K and Merrifield, MR and Bamford, SP and Cortesi, A and Das, P and Freeman, KC (2011) The PN.S Elliptical Galaxy Survey: a standard ΛCDM halo around NGC 4374? \mnras , 411 2035-2053 - 2035-2053. 10.1111/j.1365-2966.2010.17833.x.
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As part of our current programme to test ΛCDM predictions for dark matter (DM) haloes using extended kinematical observations of early-type galaxies, we present a dynamical analysis of the bright elliptical galaxy NGC 4374 (M84) based on \tilde450 planetary nebulae (PNe) velocities from the PN.Spectrograph, along with extended long-slit stellar kinematics. This is the first such analysis of a galaxy from our survey with a radially constant velocity dispersion profile. We find that the spatial and kinematical distributions of the PNe agree with the field stars in the region of overlap. The velocity kurtosis is consistent with zero at almost all radii. We construct a series of Jeans models, fitting both velocity dispersion and kurtosis to help break the mass-anisotropy degeneracy. Our mass models include DM haloes either with shallow cores or with central cusps as predicted by cosmological simulations - along with the novel introduction in this context of adiabatic halo contraction from baryon infall. Both classes of models confirm a very massive dark halo around NGC 4374, demonstrating that PN kinematics data are well able to detect such haloes when present. Considering the default cosmological mass model, we confirm earlier suggestions that bright galaxies tend to have halo concentrations higher than ΛCDM predictions, but this is found to be solved if either a Salpeter initial mass function (IMF) or an adiabatic contraction with a Kroupa IMF is assumed. Thus for the first time a case is found where the PN dynamics may well be consistent with a standard dark matter halo. A cored halo can also fit the data, and prefers a stellar mass consistent with a Salpeter IMF. The less dramatic dark matter content found in lower-luminosity ’ordinary’ ellipticals suggests a bimodality in the halo properties which may be produced by divergent baryonic effects during their assembly histories. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias and ESO-VLT at the Cerro Paranal (Chile).
|Title:||The PN.S Elliptical Galaxy Survey: a standard ΛCDM halo around NGC 4374?|
|Additional information:||archiveprefix: arXiv primaryclass: astro-ph.CO keywords: planetary nebulae: general, galaxies: elliptical and lenticular, cD, galaxies: individual: NGC 4374, galaxies: kinematics and dynamics, galaxies: structure, dark matter adsurl: http://adsabs.harvard.edu/abs/2011MNRAS.411.2035N adsnote: Provided by the SAO/NASA Astrophysics Data System|
|UCL classification:||UCL > School of BEAMS > Faculty of the Built Environment > Bartlett School > Bartlett School of Graduate Studies|
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