Day 517

Friday.

1309.6634
The galaxy-wide IMF of dwarf late-type to massive early-type galaxies
Weidner, Kroupa, Pflamm-Altenburg, Vazdekis

Observations show: galaxy-wide stellar IMF are top-heavy in galaxies with high SFRs.  Calculating the integrated galactic stellar IMF (IGIMF) as a function of SFR of a galaxy, it follows that galaxies which have or which formed with SFRs > 10 Msun/yr would have a top-heavy IGIMF in excellent consistency with the observations.  Consequently and in agreement with observations, elliptical galaxies would have higher M/L ratios as a result of the overabundance of stellar remnants compared to a stellar population that formed with an invariant canonical stellar IMF.  For the MW, the IGIMF yields very good agreement with the disk- and the bulge-IMF determinations.  Conclusions are that purely stochastic descriptions of SF on the scales of a pc and above are falsified.  Instead, SF follows the laws, stated her as axioms, which define the IGIMF theory.  Also find evidence that the power-law index beta of the embedded cluster mass function decreases with increasing SFR.  Propose further test of the IGIMF theory through counting massive stars in dwarf galaxies.

1309.6635
The Neutron Star mass distribution
Kiziltan, et al

Recent secure mass measurements of numbers of pulsars allow probing of underlying NS mass distribution.  Critically review the radio pulsar mass measurements; able to analyze a sizable population of NSs with a flexible modeling approach that can effectively accommodate a skewed underlying distribution and asymmetric measurement errors.  Find that NSs that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar distribution peak [distribution of mass?] and mass cutoff values.  NSs in double NS and NS-WD systems show consistent respective peaks at 1.33 Msun and 1.55 Msun suggesting significant mass accretion (delta m~0.22 Msun) has occurred during the spin-up phase.  The width of the mass distribution implied by double NS systems is indicative of a tight IMF while the inferred mass range is significantly wider for NSs that have gone through recycling [?].  FInd a mass cutoff at ~2.1 Msun for NSs with white dwarf companions which establishes a firm lower bound for the maximum NS mass.  This rules out the majority of strange quark and soft equation of state models as viable configurations for NS matter.  The lack of truncation close to the maximum mass cutoff along with the skewed nature of the inferred mass distribution both enforce the suggestion that the 2.1 Msun limit is set by evolutionary constraints rather than nuclear physics or GR, and the existence of rare super-massive NSs is possible.