English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The observed velocity dispersion of the classical dwarf spheroidal (dSph)galaxies of the Milky Way (MW) requires the Newtonian stellar mass-to-light($M_*/L$) ratios in the range of about 10 to more than 100 solar units that arewell outside the acceptable limit predicted by stellar population synthesismodels. Using Jeans analysis, we calculate the line-of-sight velocitydispersion ($\sigma_{\emph{los}}$) of stars in eight MW dSphs in the context ofthe modified gravity (MOG) theory of Moffat, assuming a constant $M_*/L$ ratiowithout invoking the exotic cold dark matter. First, we use the weak fieldapproximation of MOG and assume the two parameters $ \alpha $ and $ \mu $ ofthe theory to be constant as has already been inferred from fitting to theobserved rotational data of The HI Nearby Galaxy Survey catalogue of galaxies.We find that the derived $M_*/L$ ratios for almost all dSphs are too large tobe explained by the stellar population values. In order to fit theline-of-sight velocity dispersions of the dSph with reasonable $M_*/L$ values,we must vary $\alpha$ and $\mu$ on a case by case basis. A common pair ofvalues cannot be found for all dSphs. Comparing with the values found fromrotation curve fitting, it appears that $\mu$ correlates strongly with galaxyluminosity, shedding doubt on it as a universal constant.

Testing modified gravity with dwarf spheroidal galaxies