The Supersonic Project: Shining Light on SIGOs - a New Formation Channel for Globular Clusters

Supersonically induced gas objects (SIGOs) with little to no dark matter component are predicted to exist in patches of the Universe with non-negligible relative velocity between baryons and the dark matter at the time of recombination. Using {\sc arepo} hydrodynamic simulations we find that the gas densities inside these objects are high enough to allow stars to form. An estimate of the luminosity of the first star clusters formed within these SIGOs suggests that they may be observed at high redshift using future HST and JWST observations. Furthermore, our simulations indicate that SIGOs lie in a distinct place in the luminosity-radius parameter space, which can be used observationally to distinguish SIGOs from dark-matter hosting gas systems. Finally, as a proof-of-concept, we model star formation before reionization and evolve these systems to current times. We find that SIGOs occupy a similar part of the magnitude-radius parameter space as globular clusters. These results suggest that SIGOs may be linked with present-day metal-poor local globular clusters. Since the relative velocity between the baryons and dark matter is coherent over a few Mpc scales, we predict that if this is the dominant mechanism for the formation of globular clusters, their abundance should vary significantly over these scales.Comment: 9 pages, 5 figures, submitted to ApJ

Revoke First, Ask Questions Later: Challenging Minnesota’s Unconstitutional Pre-hearing Revocation Scheme

This analysis of the constitutionality of Minnesota’s prehearing revocation scheme begins by explaining the mechanics of Minnesota’s implied consent statute. Because the United States Supreme Court has established minimum procedural due process protections that must be afforded drivers, this backdrop is examined. After considering the federal standards for procedural due process, the numerous changes to Minnesota’s implied consent statute will be addressed. Next, the current challenge will be discussed, including the factual basis for the challenge, the arguments for the statute’s unconstitutionality, and the district court’s decision. Finally, this note will conclude that, given the dramatic increase in the private interest at stake and the complete lack of any procedural due process protections, Minnesota’s current pre-hearing revocation scheme is unconstitutional

“Live Sun Smart!” Testing the effectiveness of a sun safety program for middle schoolers

Background: Skin cancer is a well-recognized public health issue, and primary prevention is the most effective strategy for reducing skin cancer risk. The current recommendations are that behavioral counseling for sun safety measures is most beneficial and effective for children and adolescents and that targeting this population at primary and middle schools is the ideal intervention strategy to increase sun-protective behaviors and reduce UV exposure, sunburn incidence, and formation of new moles. Numerous studies on the effectiveness of school-based sun safety interventions among elementary and middle school students have shown an increase in sun safety knowledge, attitudes, and behaviors following the intervention. Objective: To conduct a pilot feasibility study of “Live Sun Smart!,” (LSS) a school-based, multicomponent, interactive sun safety presentation, at changing sun safety knowledge, attitudes, and behaviors among middle school students. Methods: A non-randomized, single-group pretest-posttest interventional pilot study of the LSS program among children enrolled in grade 6. Results: After exposure to LSS, participants were more likely to give correct answers to knowledge-based sun safety questions and to report negative attitudes toward tanning. Minimal and not significant changes were found in self-reported sun safety behaviors, though students did report an intention to change behaviors following the intervention. Participants were satisfied with the program and believed it increased their sun safety knowledge. Conclusion: Live Sun Smart! appears to be an effective school-based, multicomponent sun safety program for improving sun safety knowledge and attitudes toward tanning among middle school students in this initial test of it. The strengths and weaknesses of this pilot study have implications for future research

Magnetohydrodynamics (MHD) Engineering Test Facility (ETF) 200 MWe power plant. Design Requirements Document (DRD)

A description and the design requirements for the 200 MWe (nominal) net output MHD Engineering Test Facility (ETF) Conceptual Design, are presented. Performance requirements for the plant are identified and process conditions are indicated at interface stations between the major systems comprising the plant. Also included are the description, functions, interfaces and requirements for each of these major systems. The lastest information (1980-1981) from the MHD technology program are integrated with elements of a conventional steam electric power generating plant

Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster

Aims. We aim to provide observational constraints on diffusion models that predict peculiar chemical abundances in the atmospheres of Am stars. We also intend to check if chemical peculiarities and slow rotation can be explained by the presence of a weak magnetic field. Methods. We have obtained high resolution, high signal-to-noise ratio spectra of eight previously-classified Am stars, two normal A-type stars and one Blue Straggler, considered to be members of the Praesepe cluster. For all of these stars we have determined fundamental parameters and photospheric abundances for a large number of chemical elements, with a higher precision than was ever obtained before for this cluster. For seven of these stars we also obtained spectra in circular polarization and applied the LSD technique to constrain the longitudinal magnetic field. Results. No magnetic field was detected in any of the analysed stars. HD 73666, a Blue Straggler previously considered as an Ap (Si) star, turns out to have the abundances of a normal A-type star. Am classification is not confirmed for HD 72942. For HD 73709 we have also calculated synthetic Delta-a photometry that is in good agreement with the observations. There is a generally good agreement between abundance predictions of diffusion models and values that we have obtained for the remaining Am stars. However, the observed Na and S abundances deviate from the predictions by 0.6 dex and >0.25 dex respectively. Li appears to be overabundant in three stars of our sample.Comment: Accepted for publication on A&

TurbuStat: Turbulence Statistics in Python

We present TurbuStat (v1.0): a Python package for computing turbulence statistics in spectral-line data cubes. TurbuStat includes implementations of fourteen methods for recovering turbulent properties from observational data. Additional features of the software include: distance metrics for comparing two data sets; a segmented linear model for fitting lines with a break-point; a two-dimensional elliptical power-law model; multi-core fast-fourier-transform support; a suite for producing simulated observations of fractional Brownian Motion fields, including two-dimensional images and optically-thin HI data cubes; and functions for creating realistic world coordinate system information for synthetic observations. This paper summarizes the TurbuStat package and provides representative examples using several different methods. TurbuStat is an open-source package and we welcome community feedback and contributions.Comment: Accepted in AJ. 21 pages, 8 figure

A new density variance - Mach number relation for subsonic and supersonic, isothermal turbulence

The probability density function (PDF) of the gas density in subsonic and supersonic, isothermal, driven turbulence is analyzed with a systematic set of hydrodynamical grid simulations with resolutions up to 1024^3 cells. We performed a series of numerical experiments with root mean square (r.m.s.) Mach number M ranging from the nearly incompressible, subsonic (M=0.1) to the highly compressible, supersonic (M=15) regime. We study the influence of two extreme cases for the driving mechanism by applying a purely solenoidal (divergence-free) and a purely compressive (curl-free) forcing field to drive the turbulence. We find that our measurements fit the linear relation between the r.m.s. Mach number and the standard deviation of the density distribution in a wide range of Mach numbers, where the proportionality constant depends on the type of the forcing. In addition, we propose a new linear relation between the standard deviation of the density distribution and the standard deviation of the velocity in compressible modes, i.e. the compressible component of the r.m.s. Mach number. In this relation the influence of the forcing is significantly reduced, suggesting a linear relation between the standard deviation of the density distribution and the standard deviation of the velocity in compressible modes, independent of the forcing, ranging from the subsonic to the supersonic regime.Comment: 8 pages,6 figures, The Astrophysical Journal (submitted