Open access
Datum
2017-11Typ
- Journal Article
ETH Bibliographie
yes
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Abstract
We present a new non-parametric Jeans code, GRAVSPHERE, that recovers the density ρ(r) and velocity anisotropy β(r) of spherical stellar systems, assuming only that they are in a steady state. Using a large suite of mock data, we confirm that with only line-of-sight velocity data, GRAVSPHERE provides a good estimate of the density at the projected stellar half-mass radius, ρ(R1/2), but is not able to measure ρ(r) or β(r), even with 10 000 tracer stars. We then test three popular methods for breaking this ρ − β degeneracy: using multiple populations with different R1/2; using higher order ‘virial shape parameters’ (VSPs); and including proper motion data. We find that two populations provide an excellent recovery of ρ(r) in-between their respective R1/2. However, even with a total of ∼7000 tracers, we are not able to well-constrain β(r) for either population. By contrast, using 1000 tracers with higher order VSPs we are able to measure ρ(r) over the range 0.5 < r/R1/2 < 2 and broadly constrain β(r). Including proper motion data for all stars gives an even better performance, with ρ and β well-measured over the range 0.25 < r/R1/2 < 4. Finally, we test GRAVSPHERE on a triaxial mock galaxy that has axis ratios typical of a merger remnant [1 : 0.8 : 0.6]. In this case, GRAVSPHERE can become slightly biased. However, we find that when this occurs the data are poorly fit, allowing us to detect when such departures from spherical symmetry become problematic. Mehr anzeigen
Persistenter Link
https://doi.org/10.3929/ethz-b-000219959Publikationsstatus
publishedExterne Links
Zeitschrift / Serie
Monthly Notices of the Royal Astronomical SocietyBand
Seiten / Artikelnummer
Verlag
Oxford University PressThema
methods: miscellaneous; proper motions; globular clusters: general; galaxies: clusters: general; galaxies: haloes; dark matterFörderung
128540 - Shedding light on dark matter (SNF)
Anmerkungen
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.ETH Bibliographie
yes
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