Influence of baryonic physics in galaxy simulations: a semi-analytic treatment of the molecular component

Recent work in galaxy formation has enlightened the important role of baryon physics, to solve the main problems encountered by the standard theory at the galactic scale, such as the galaxy stellar mass functions, or the missing satellites problem. The present work aims at investigating in particular the role of the cold and dense molecular phase, which could play a role of gas reservoir in the outer galaxy discs, with low star formation efficiency. Through TreeSPH simulations, implementing the cooling to low temperatures, and the inclusion of the molecular hydrogen component, several feedback efficiencies are studied, and results on the gas morphology and star formation are obtained. It is shown that molecular hydrogen allows some slow star formation (with gas depletion times of about 5 Gyr) to occur in the outer parts of the discs. This dense and quiescent phase might be a way to store a significant fraction of dark baryons, in a relatively long time-scale, in the complete baryonic cycle, connecting the galaxy discs to hot gaseous haloes and to the cosmic filaments.Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 29 figure

Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discs

Radial stellar migration in galactic discs has received much attention in studies of galactic dynamics and chemical evolution, but remains a dynamical phenomenon that needs to be fully quantified. In this work, using a Tree-SPH simulation of an Sb-type disc galaxy, we quantify the effects of blurring (epicyclic excursions) and churning (change of guiding radius). We quantify migration (either blurring or churning) both in terms of flux (the number of migrators passing at a given radius), and by estimating the population of migrators at a given radius at the end of the simulation compared to non-migrators, but also by giving the distance over which the migration is effective at all radii. We confirm that the corotation of the bar is the main source of migrators by churning in a bar-dominated galaxy, its intensity being directly linked to the episode of a strong bar, in the first 1-3 Gyr of the simulation. We show that within the outer Lindblad resonance (OLR), migration is strongly dominated by churning, while blurring gains progressively more importance towards the outer disc and at later times. Most importantly, we show that the OLR limits the exchange of angular momentum, separating the disc in two distinct parts with minimal or null exchange, except in the transition zone, which is delimited by the position of the OLR at the epoch of the formation of the bar, and at the final epoch. We discuss the consequences of these findings for our understanding of the structure of the Milky Way disc. Because the Sun is situated slightly outside the OLR, we suggest that the solar vicinity may have experienced very limited churning from the inner disc.Comment: Accepted for publication in Astronomy and Astrophysics (acceptance date: 27/04/15), 24 pages, 24 figure

Earned Value Analysis Lesson Plan and Activity

At California Polytechnic State University, in the Construction Management Department there is a need for a lesson plan which teaches students the concepts of earned value analysis as it applies to construction projects. As many construction management students from Cal Poly go into industry and take part in complex projects, it will be beneficial to understand project management tools such as earned value. Earned value analysis focuses on two critical components, time and money and how they relate to each other and compare to the original estimate throughout the duration of a project. Comparing the estimated values to actual values during construction provides variables to calculate the schedule performance index and cost performance index. These indexes give an accurate estimate as to if the project is ahead or behind schedule and over or under budget. Understanding how to calculate these values will allow for timely action by the project team to keep projects on schedule and on budget

The COMPLETE Survey of Outflows in Perseus

We present a study on the impact of molecular outflows in the Perseus molecular cloud complex using the COMPLETE survey large-scale 12CO(1-0) and 13CO(1-0) maps. We used three-dimensional isosurface models generated in RA-DEC-Velocity space to visualize the maps. This rendering of the molecular line data allowed for a rapid and efficient way to search for molecular outflows over a large (~ 16 sq. deg.) area. Our outflow-searching technique detected previously known molecular outflows as well as new candidate outflows. Most of these new outflow-related high-velocity features lie in regions that have been poorly studied before. These new outflow candidates more than double the amount of outflow mass, momentum, and kinetic energy in the Perseus cloud complex. Our results indicate that outflows have significant impact on the environment immediately surrounding localized regions of active star formation, but lack the energy needed to feed the observed turbulence in the entire Perseus complex. This implies that other energy sources, in addition to protostellar outflows, are responsible for turbulence on a global cloud scale in Perseus. We studied the impact of outflows in six regions with active star formation within Perseus of sizes in the range of 1 to 4 pc. We find that outflows have enough power to maintain the turbulence in these regions and enough momentum to disperse and unbind some mass from them. We found no correlation between outflow strength and star formation efficiency for the six different regions we studied, contrary to results of recent numerical simulations. The low fraction of gas that potentially could be ejected due to outflows suggests that additional mechanisms other than cloud dispersal by outflows are needed to explain low star formation efficiencies in clusters.Comment: Published in The Astrophysical Journa

Improvement of the Water Distribution System in Chaguarpamba, Ecuador: An Engineers Without Borders Program.

EWB­Miami has been working on a collaborative initiative with the community of Chaguarpamba, Ecuador for the past four years to find a sustainable solution to disinfect the community’s water supply and provide an adequate supply of clean water. The project was opened in 2011 and since then the chapter has taken four trip to the community for assessment and implementation. On the first trip in March 2012, six student chapter members and our professional mentor traveled to Chaguarpamba to conduct a comprehensive assessment of the water quality. During that trip they identified fecal coliforms as the primary cause of water contamination. The health clinic overseen by the Peace Corps confirmed that parasites and diarrhea due to consuming contaminated water were the leading health care issues in Chaguarpamba. Therefore, EWB­Miami partnered with the Chaguarpamba municipality and community to engineer a sustainable water disinfection solution as well as work on a water source development project. EWB­Miami engineered a solution to improve capture at the water collection sites while eliminating pipe obstructions such as sediment blockage which frequently impedes water flow into the distribution system.Another group of students traveled to Chaguarpamba in January 2013 to implement their solutions to these two projects, mainly an improved water chlorination system, as well as search for and test the viability of a new potential source of water for the village. At the request of the community, EWB­Miami shifted the focus of the project work in 2014 to building an AutoCAD map of their existing water distribution system. This involved collecting the data necessary to create a map of the city’s water system, such as the locations of the piping, meters, valves, and other parts of the system. Beyond the map, EWB­Miami found it necessary to begin developing a hydraulic model, made in EPA NET, based on the map. Currently, the city does not receive enough water to support its growing population and does not have a map of its drinking water system. The map and especially the model are necessary to determine the locations of leaks and areas where water is being used but not being paid for. By creating a map and model of their system, we can provide a way to determine what changes should be made to increase the amount of water available for the city of Chaguarpamba. The municipality is also considering constructing a new pipeline from an additional water source in the future. This project is highly dependent on funding, such as government loans. Because of this very long term aspect to the project and the fact that Chaguarpamba does have college­educated engineers, EWB­Miami and the municipality have come to an agreement to end our project partnership approximately one year early. Before a complete program close out EWB­Miami will take a final trip to the community to provide an updated version of the AutoCAD map, a complete hydraulic model, and training for the local engineers on how to use the model software. 

As newly returned New York Police Commissioner, Bill Bratton’s first task will be to regain the trust of the city’s most heavily policed groups

Last week, Bill Bratton was sworn in as New York City’s police commissioner, as part of the administration of new mayor, Bill de Blasio. David Halle, Andrew A. Beveridge, and Sydney Beveridge, take a closer look at Bill Bratton’s policy success in reducing crime, in both New York and Los Angeles, through the use of the COMPSTAT program and its successors. They write that, now that he has returned to New York, Bratton’s challenge will be to keep crime rates low while reducing the widespread hatred of the police among black residents that has been created by ‘Stop & Frisk’ policies

Linguistics

Contains research objectives

Linguistics

Contains reports on three research projects.National Science Foundation (Grant GP-2495)National Institutes of Health (Grant MH-04737-04)U. S. Air Force. Electronics Systems Division (Contract AFl9(628)-2487)National Aeronautics and Space Administration (Grant NsG-496