Revisiting the Bulge-Halo Conspiracy. I. Dependence on Galaxy Properties and Halo Mass
Abstract
We carry out a systematic investigation of the total mass density profile of massive ({log} {M}{star}/{M}⊙ ≳ 11.3) early-type galaxies and its dependence on galactic properties and host halo mass with the aid of a variety of lensing/dynamical data and large mock galaxy catalogs. The latter are produced via semi-empirical models that, by design, are based on just a few basic input assumptions. Galaxies with measured stellar masses, effective radii, and Sérsic indices, are assigned, via abundance matching relations, host dark matter halos characterized by a typical ΛCDM profile. Our main results are as follows. (1) In line with observational evidence, our semi-empirical models naturally predict that the total, mass-weighted density slope at the effective radius γ‧ is not universal, steepening for more compact and/or massive galaxies, but flattening with increasing host halo mass. (2) Models characterized by a Salpeter or variable initial mass function (IMF) and uncontracted dark matter profiles are in good agreement with the data, while a Chabrier IMF and/or adiabatic contractions/expansions of the dark matter halos are highly disfavored. (3) Currently available data on the mass density profiles of very massive galaxies ({log} {M}{star}/{M}⊙ ≳ 12), with {M}{halo}≳ 3× {10}14 {M}⊙ , favor instead models with a stellar profile flatter than a Sérsic one in the very inner regions (r ≲ 3-5 kpc), and a cored NFW or Einasto dark matter profile with median halo concentration a factor of ∼2 or ≲1.3, respectively, higher than those typically predicted by N-body numerical simulations.
- Publication:
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The Astrophysical Journal
- Pub Date:
- May 2017
- DOI:
- 10.3847/1538-4357/aa66ce
- arXiv:
- arXiv:1703.06145
- Bibcode:
- 2017ApJ...840...34S
- Keywords:
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- cosmology: theory;
- galaxies: evolution;
- galaxies: statistics;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 23 pages, 10 figures, 3 Appendices (with an extra 7 figures). ApJ, accepted. Main results in Figures 3, 5, 6, 8