Planetary nebulae as mass tracers of their parent galaxies: Biases in the estimate of the kinematical quantities

Free access article

Issue		A&A Volume 377, Number 3, October III 2001


Page(s)		784 - 800
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20011106

A&A 377, 784-800 (2001)
DOI: 10.1051/0004-6361:20011106

Planetary nebulae as mass tracers of their parent galaxies: Biases in the estimate of the kinematical quantities

N. R. Napolitano^{1, 2}, M. Arnaboldi¹, K. C. Freeman³ and M. Capaccioli^{1, 2}

¹ Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
² Dipartimento di Scienze Fisiche, Università Federico II di Napoli, Complesso Monte S. Angelo, via Cintia, 80126, Napoli, Italy
³ RSAA, Mount Stromlo Observatory, Australian National University, Weston Creek PO, ACT 2611, Australia

(Received 6 June 2001 / Accepted 31 July 2001)

Abstract
Multi-object and multi-fiber spectrographs on 4 and 8 m telescopes make it possible to use extragalactic planetary nebulae (PNe) in the outer halos of early-type galaxies as kinematical tracers, where classical techniques based on integrated stellar light fail. Until now, published PNe radial velocity samples are small, with only a few tens of radial velocity measurements (except for a few cases like NGC 5128 or M 31), causing uncertainties in the mass and angular momentum estimates based on these data. To quantify these uncertainties, we have made equilibrium models for spherical galaxies, with and without dark matter, and via Montecarlo simulations we produce radial velocity samples with different sizes. We then apply, to these discrete radial velocity fields, the same standard kinematical analysis as it is commonly done with small samples of observed PNe radial velocities. By comparison of the inferred quantities with those computed from the analytical model, we test for systematic biases and establish a robust procedure to infer the angular momentum distribution and radial velocity dispersion profiles from such samples.

Key words: techniques: radial velocities -- galaxies: elliptical -- galaxies: halos -- galaxies: kinematics and dynamics -- dark matter

Offprint request: N. R. Napolitano, napolita@na.astro.it

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