Dark and luminous matter in the outer halos of elliptical galaxies
Final Report Abstract
The goal of this proposal was to learn about the dark matter content, angular momentum distribution, and orbital structure in the outer halos of early-type galaxies (ETGs). With Planetary Nebula Spectrograph (PN.S) data we were able to follow the angular momentum and velocity dispersion profiles of ∼ 15 of these galaxies to beyond 5 half-light radii Re. The division from Sauron into fast and slow rotators generally extends into the outer halos, but in a few galaxies either the central parts or the outer halos rotate more slowly than this would predict. Most of these galaxies were shown to have slowly falling total velocity dispersion profiles; however, a significant fraction of intermediate-luminosity ETGs has steeply falling profiles. We analyzed a few ETGs from both classes with dynamical models in order to understand their dark matter fractions and orbital structure. In the intermediate-luminosity ETGs with steeply falling dispersion profiles the degeneracy between mass and anisotropy remains large; dark matter halos corresponding to ΛCDM predictions are consistent with the data if the orbital anisotropy in the halos is large. By contrast, the massive, X-ray bright ellipticals have nearly constant dispersion profiles and circular velocity curves, implying massive and dense dark matter halos with little degeneracy. A still on-going comparison with cosmological hydrodynamic simulations indicates that the dark matter halo and angular momentum properties of the simulated galaxies are consistent with the halos of ETGs as inferred from their outer kinematics.
Publications
- 2008. Dark matter content and internal dynamics of NGC 4697: NMAGIC particle models from slit data and planetary nebulae velocities. Mon. Not. R. astr. Soc. 385, 1729-1748
De Lorenzi, F., Gerhard, O., Saglia, R.P., Sambhus, N., Debattista, V.P., Panella, M., Méndez, R.H.
(See online at https://doi.org/10.1111/j.1365-2966.2008.12905.x) - 2009. Dearth of dark matter or massive dark halo? Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC 3379. Mon. Not. R. astr. Soc. 395, 76-96
De Lorenzi, F., Gerhard, O., Coccato, L., Arnaboldi, M., Capaccioli, M., Douglas, N.G., Freeman, K.C., Kuijken, K., Merrifield, M.R., Napolitano, N.R., Noordermeer, E., Romanowsky, A.J., Debattista, V.P.
(See online at https://doi.org/10.1111/j.1365-2966.2009.14553.x) - 2009. Kinematic properties of early-type haloes using planetary nebulae. Mon. Not. R. astr. Soc. 394, 1249-1283
Coccato, L., Gerhard, O., Arnaboldi, M., Das, P., Douglas, N.G., Kuijken, K., Merrifield, M.R., Napolitano, N.R., Noordermeer, E., Romanowsky, A.J., Capaccioli, M., Cortesi, A., De Lorenzi, F., Freeman, K.C.
(See online at https://doi.org/10.1111/j.1365-2966.2009.14417.x) - 2010. The non-isothermal mass profiles of X-ray bright elliptical galaxies. Mon. Not. R. astr. Soc. 409, 1362-1378
Das, P., Gerhard, O., Churazov, E., Zhuravleva, I.
(See online at https://doi.org/10.1111/j.1365-2966.2010.17417.x) - 2011. Unifying a boxy bulge and planar long bar in the Milky Way. Astrophys. J. (Letters) 734, L20-L24
Martinez-Valpuesta, I., Gerhard, O.
(See online at https://doi.org/10.1088/2041-8205/734/1/L20) - 2011. Unravelling the origins of S0 galaxies using maximum likelihood analysis of planetary nebulae kinematics. Mon. Not. R. astr. Soc. 414, 642-651
Cortesi, A., Merrifield, M.R., Arnaboldi, M., Gerhard, O., Martinez-Valpuesta, I., Saha, K., Coccato, L., Bamford, S., Napolitano, N.R., Das, P., Douglas, N.G., Romanowsky, A.J., Kuijken, K., Capaccioli, M., Freeman, K.C.
(See online at https://doi.org/10.1111/j.1365-2966.2011.18429.x) - 2011. Using NMAGIC to probe the dark matter halo and orbital structure of the X-ray bright, massive elliptical galaxy, NGC 4649. Mon. Not. R. astr. Soc. 415, 1244-1258
Das, P., Gerhard, O., Mendez, R.H., Teodorescu, A.M., de Lorenzi, F.
(See online at https://doi.org/10.1111/j.1365-2966.2011.18771.x)
