Further constraints on variations in the IMF from LMXB populations

摘要: We present constraints on variations in the initial mass function (IMF) of nine local early-type galaxies based their low X-ray binary (LMXB) populations. Comprised accreting black holes and neutron stars, these LMXBs can be used to constrain important high end IMF. consider LMXB populations beyond cores ($>0.2R_{e}$; covering $75-90\%$ stellar light) find no evidence for systematic IMF with velocity dispersion ($\sigma$). reject IMFs which become increasingly bottom heavy $\sigma$, up steep power-laws (exponent, $\alpha>2.8$) massive ($\sigma>300$km/s), galactocentric radii $>1/4\ R_{e}$. Previously proposed that $\sigma$ are consistent data if only number stars $(<0.5M_{\odot}$) varies. note our results some recent work proposes extreme central regions galaxies. also top-heavy resulting significantly more LMXBs. Such a model is observations, but additional required distinguish between this an invariant For six galaxies, we directly compare published mismatch parameters from Atlas3D survey, $\alpha_{dyn}$. good agreement population higher $\alpha_{dyn}$ have -- although caution sample quite small. Future observations provide further insights into origin variations.