Open AccessDynamical virial masses of Lyman‐break galaxy haloes at z = 3
Author(s) -
Weatherley Stephen J.,
Warren Stephen J.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2005.00071.x
Subject(s) - physics , astrophysics , halo , virial theorem , virial mass , galaxy , dark matter , redshift , radius , velocity dispersion , baryon , concentration parameter , population , mass distribution , astronomy , computer science , boundary value problem , dirichlet distribution , demography , computer security , quantum mechanics , sociology
We improve on our earlier dynamical estimate of the virial masses of the haloes of Lyman‐break galaxies (LBGs) at redshift z = 3 by accounting for the effects of seeing, slit width and observational uncertainties. From an analysis of the small number of available rotation curves for LBGs we determine a relation V c7 = (1.9 ± 0.2)σ between circular velocity at a radius of 7 kpc, V c7 , and central line velocity width, σ. We use this relation to transform the measured velocity widths of 32 LBGs to the distribution of circular velocities, V c7 , for the population of LBGs brighter than . We compare this distribution against the predicted distribution for the ‘massive‐halo’ model in which LBGs pinpoint all of the highest mass dark matter haloes at that epoch. The observed LBG circular velocities are smaller than the predicted circular velocities by a factor of >1.4 ± 0.15. This is a lower limit, as we have ignored any increase of circular velocity caused by baryonic dissipation. The massive‐halo model predicts a median halo virial mass of 10 12.3 M ⊙ , and a small spread of circular velocities, V c7 . Our median estimated dynamical mass is <10 11.6±0.3 M ⊙ , which is significantly smaller; furthermore, the spread of our derived circular velocities is much larger than the massive‐halo prediction. These results are consistent with a picture which leaves some of the most massive haloes available for occupation by other populations which do not meet the LBG selection criteria. Our new dynamical mass limit is a factor of 3 larger than our earlier estimate which neglected the effects of seeing and slit width. The median halo mass recently estimated by Adelberger et al. from the measured clustering of LBGs is 10 11.86±0.3 M ⊙ . Our dynamical analysis appears to favour lower masses and to be more in line with the median mass predicted by the collisional starburst model of Somerville et al., which is 10 11.3 M ⊙ .