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The massive dark halo of the compact, early-type galaxy NGC 1281 | | Akın Yıldırım
; Remco van den Bosch
; Glenn van de Ven
; Aaron Dutton
; Ronald Läsker
; Bernd Husemann
; Jonelle L. Walsh
; Karl Gebhardt
; Kayhan Gültekin
; Ignacio Martín-Navarro
; | | Date: |
10 Nov 2015 | | Abstract: | We investigate the compact, early-type galaxy NGC 1281 with integral field
unit observations to map the stellar LOSVD out to 5 effective radii and
construct orbit-based dynamical models to constrain its dark and luminous
matter content. Under the assumption of mass-follows-light, the H-band stellar
mass-to-light ratio (M/L) is {Upsilon} = 2.7(+-0.1) {Upsilon}_{sun}, higher
than expected from our stellar population synthesis fits with either a
canonical Kroupa ({Upsilon} = 1.3 {Upsilon}_{sun}) or Salpeter ({Upsilon} =
1.7 {Upsilon}_{sun}) stellar initial mass function. Such models also cannot
reproduce the details of the LOSVD. Models with a dark halo recover the
kinematics well and indicate that NGC 1281 is dark matter dominated, making up
~ 90 per cent of the total enclosed mass within the kinematic bounds.
Parameterised as a spherical NFW profile, the dark halo mass is 11.5 <
log(M_{DM}/M_{sun}) < 11.8 and the stellar M/L is 0.6 < {Upsilon} < 1.1.
However, this stellar M/L is lower than predicted by its old stellar
population. Moreover, the halo mass within the kinematic extent is ten times
larger than expected based on {Lambda}CDM predictions, and an extrapolation
yields cluster sized dark halo masses. Adopting {Upsilon} = 1.7
{Upsilon}_{sun} yields more moderate dark halo virial masses, but these models
fit the kinematics worse. A non-NFW model might solve the discrepancy between
the unphysical consequences of the best-fitting dynamical models and models
based on more reasonable assumptions for the dark halo and stellar
mass-to-light ratio, which are disfavoured according to our parameter
estimation. | | Source: | arXiv, 1511.3131 | | Services: | Forum | Review | PDF | Favorites | |
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