Hands-on Gravitational Wave Astronomy: Extracting astrophysical information from simulated signals

In this paper we introduce a hands-on activity in which introductory astronomy students act as gravitational wave astronomers by extracting information from simulated gravitational wave signals. The process mimics the way true gravitational wave analysis will be handled by using plots of a pure gravitational wave signal. The students directly measure the properties of the simulated signal, and use these measurements to evaluate standard formulae for astrophysical source parameters. An exercise based on the discussion in this paper has been written and made publicly available online for use in introductory laboratory courses.Comment: 5 pages, 4 figures; submitted to Am. J. Phy

Ionizing feedback from massive stars in massive clusters: Fake bubbles and untriggered star formation

We use Smoothed Particle Hydrodynamics to simulate the formation of a massive (10^6Msun) stellar cluster system formed from the gravitational collapse of a turbulent molecular cloud. We investigate the hierarchical clustering properties of our model system and we study the influence of the photoionizing radiation produced by the system's multiple O-type stars on the evolution of the protocluster. We find that dense gas near the ionizing sources prevents the radiation from eroding the filaments in which most of the star formation occurs and that instead, ionized gas fills pre-existing voids and bubbles originally created by the turbulent velocity field.Comment: 9 pages, 12 figures, accepted by MNRA

Report to the California Public Utilities Commission Regarding Ex Parte Communications and Related Practices

Part I contains the analysis of existing law. We review the statutes and regulations governing ex parte communications before the CPUC, examine corresponding laws of other jurisdictions, and compare the CPUC statutes and regulations with those of the other jurisdictions. In Part II we examine actual ex parte practices before the CPUC. Based on data obtained from notices filed on the Commission’s website by parties to rate-setting cases, we provide a quantitative characterization of the extent and nature of noticed ex parte communications over the past roughly 22 years. We then place ex parte communications within the context of the CPUC’s proceedings. Part III provides the results of an interview process we undertook to hear the experiences and opinions of people with a stake or an interest in CPUC decision-making, including representatives of regulated utilities, intervenor groups who generally (but not always) appear in CPUC rate-setting cases in opposition to the positions of utilities, companies and industry groups who generally oppose specific utilities’ positions, legislators and legislative staff, public critics of CPUC ex parte practices, CPUC staff (administrative law judges (ALJs), attorneys, and technical staff), and the CPUC Commissioners and their staffs. Then, in Part IV, we present our analysis of this information and our recommendations for changes to statutes, CPUC rules, and Commission practices

Massive stars in massive clusters - IV. Disruption of clouds by momentum-driven winds

We examine the effect of momentum-driven OB-star stellar winds on a parameter space of simulated turbulent giant molecular clouds using smoothed particle hydrodynamic simulations. By comparison with identical simulations in which ionizing radiation was included instead of winds, we show that momentum-driven winds are considerably less effective in disrupting their host clouds than are H ii regions. The wind bubbles produced are smaller and generally smoother than the corresponding ionization-driven bubbles. Winds are roughly as effective in destroying the very dense gas in which the O stars are embedded, and thus shutting down the main regions of star-forming activity in the model clouds. However, their influence falls off rapidly with distance from the sources, so they are not as good at sweeping up dense gas and triggering star formation further out in the clouds. As a result, their effect on the star formation rate and efficiency is generally more negative than that of ionization, if they exert any effect at all.Peer reviewe