3,199 research outputs found
Stellar mass versus stellar velocity dispersion: which is better for linking galaxies to their dark matter halos?
It was recently suggested that, compared to its stellar mass (M*), the
central stellar velocity dispersion (sigma*) of a galaxy might be a better
indicator for its host dark matter halo mass. Here we test this hypothesis by
estimating the dark matter halo mass for central alaxies in groups as function
of M* and sigma*. For this we have estimated the redshift-space
cross-correlation function (CCF) between the central galaxies at given M* and
sigma* and a reference galaxy sample, from which we determine both the
projected CCF, w_p(r_p), and the velocity dispersion profile (VDP) of
satellites around the centrals. A halo mass is then obtained from the average
velocity dispersion within the virial radius. At fixed M*, we find very weak or
no correlation between halo mass and sigma*. In contrast, strong mass
dependence is clearly seen even when sigma* is limited to a narrow range. Our
results thus firmly demonstrate that the stellar mass of central galaxies is
still a good (if not the best) indicator for dark matter halo mass, better than
the stellar velocity dispersion. The dependence of galaxy clustering on sigma*
fixed M*, as recently discovered by Wake et al. (2012), may be attributed to
satellite galaxies, for which the tidal stripping occurring within halos has
stronger effect on stellar mass than on central stellar velocity dispersion.Comment: 4 pages, 4 figures, accepted for publication in ApJ Letters, minor
revisions in the tex
The Status and Prospects of Community Education Workers in China
Professionalization, career development prospects, and social value are the three basic components of the status and prospects of community education workers, which influence their choice to continue their careers or not. In China, these problems are complex and lacking in systematic research, and the current situation does not meet the needs of community education. This study interviewed 24 community workers regarding their salaries, working conditions, and training and career advancement opportunities to evaluate this situation in Ningbo City. The findings highlight challenges in the evaluation processes and work motivations of community education workers, including teams without professional knowledge, lack of training opportunities, unsupportive policies, and low salaries. These findings can be used by governments and community workers to find collaborative ways to facilitate community education processes, including the provision of adult education for community educators. New legal policies to raise the status of community educators are also suggested
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