Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio

Measurement of Gamma-B(B)over-Bar/Gamma(Had) from Hadronic Decays of the Z

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High Mass Photon Pairs in L+L-Gamma-Gamma Events at Lep

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Results from the L3 Experiment at Lep

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Search for a Z' at the Z Resonance

Contains fulltext : 26850___.PDF (publisher's version ) (Open Access

Search For Nonminimal Higgs Bosons In Z0 Decays

We report on a search for the neutral and charged Higgs bosons predicted by models of spontaneous symmetry breaking with more than one Higgs doublet field. No signals are observed. We set model-independent limits on masses or branching ratios of singly and pair-produced neutral and charged Higgs bosons. In addition, we interpret our results in the framework of a general two-doublet Higgs model and the Minimal Supersymmetric extension of the Standard Model

SEARCH FOR NARROW VECTOR RESONANCES IN THE Z MASS RANGE

The hadronic lineshape of the Z has been analysed for evidence of signals of new, narrow vector resonances in the Z-mass range. The production rate of such resonances would be enhanced due to mixing with the Z. No evidence for new states is found, and it is thus possible to exclude, at the 95% confidence level, a quarkonium state in the mass range from 87.7 to 94.7 GeV