Cusp Disruption in Minor Mergers

We present 0.55 x 10^6 particle simulations of the accretion of high-density dwarf galaxies by low-density giant galaxies, using models that contain both power-law central density cusps and point masses representing supermassive black holes. The cusp of the dwarf galaxy is disrupted during the merger, producing a remnant with a central density that is only slightly higher than that of the giant galaxy initially. Removing the black hole from the giant galaxy allows the dwarf galaxy to remain intact and leads to a remnant with a high central density, contrary to what is observed. Our results support the hypothesis that the persistence of low-density cores in giant galaxies is a consequence of supermassive black holes.Comment: 5 pages, 2 postscript figures, uses emulateapj.sty. Accepted for publication in The Astrophysical Journal Letter

“I\u27ll do whatever as long as you keep telling me that I’m important”: A case study illustrating the link between adolescent dating violence and sex trafficking victimization

Background: Approximately 10% of U.S. high school-attending youth are physically abused by a dating partner each year. Many sequelae of dating violence have been documented, but the dating violence literature is lacking information about commercial sexual exploitation as a possible outcome of an abusive dating relationship. Conversely, scholarship on sex trafficking victimization has documented that some girls are enticed into sex work by exploitative partners who initially pretend to be dating partners, but the research lacks specificity about why and how the girls become vulnerable to these destructive relationships. This case series chronicles the experiences of four women who were commercially sexually exploited in the U.S. as minors, identifies common themes cross their narratives, and organizes these themes into a proposed framework for understanding a possible pathway from safety to unsafe dating to sex trafficking victimization. Methods: We conducted in-depth qualitative interviews with four adult women who had firsthand experience as victims of domestic minor sex trafficking. Participants were recruited through an organization that serves sex trafficking survivors. A constructivist grounded approach was used for data analysis. Participants’ narratives are presented, as well as illustrative quotes that typify each of the primary themes identified. Results: There were six primary themes that emerged from the cases’ narratives. Factors that made girls vulnerable to entering into abusive dating relationships and subsequently to experiences as sex trafficked minors included: (1) feeling physically unattractive and unimportant; (2) lacking examples of healthy relationships; (3) experiencing sexual abuse that caused subsequent dissociation and emotional debilitation; (4) being flattered by romantic gestures early in an abusive dating relationship and becoming emotionally attached; (5) gaining confidence from dating someone with higher social status; and (6) experiencing short-term satisfaction from out-earning other sex workers. Secondary themes that merit further investigation included having conflicts with guardians, engaging in criminal behavior at the request of their dating partner, and developing substance dependence that made it difficult to exit sex work. Discussion: Findings support the conclusions that one pathway into commercial sexual exploitation for minors is via dating partners, and that some minors are motivated to engage in sex work out of devotion to their dating partners rather than fear of violent retribution. A proposed framework for understanding how youth become vulnerable to sexual exploitation by a dating partner includes pre-dating, early phase dating, and late phase dating factors. Some pre-dating factors, for example, include feeling insecure, being bullied by peers, and having conflict with a guardian. Early phase dating factors include being impressed by the high social status of a new love interest and romantic gestures. Late phase dating factors include engaging in criminal activity to please the dating partner, and being physically, sexually, financially and emotionally abused. Additional empirical research that replicates and expands the proposed framework is encouraged, with the long-term objective of improving both dating violence and sexual exploitation prevention initiative

A Counterpart to the Radial Orbit Instability in Triaxial Stellar Systems

Self-consistent solutions for triaxial mass models are highly non-unique. In general, some of these solutions might be dynamically unstable, making them inappropriate as descriptions of steady-state galaxies. Here we demonstrate for the first time the existence in triaxial galaxy models of an instability similar to the radial-orbit instability of spherical models. The instability manifests itself when the number of box orbits, with predominantly radially motions, is sufficiently large. N-body simulations verify that the evolution is due neither to chaotic orbits nor to departures of the model from self-consistency, but rather to a collective mode. The instability transforms the triaxial model into a more prolate, but still triaxial, configuration. Stable triaxial models are obtained when the mass contribution of radial orbits is reduced. The implications of our results for the shapes of dark-matter halos are discussed.Comment: 14 pages, 16 figure

ATRAN3S: An unsteady transonic code for clean wings

The development and applications of the unsteady transonic code ATRAN3S for clean wings are discussed. Explanations of the unsteady, transonic small-disturbance aerodynamic equations that are used and their solution procedures are discussed. A detailed user's guide, along with input and output for a sample case, is given

A center for commercial development of space: Real-time satellite mapping. Remote sensing-based agricultural information expert system

The research project results in a powerful yet user friendly CROPCAST expert system for use by a client to determine the crop yield production of a certain crop field. The study is based on the facts that heuristic assessment and decision making in agriculture are significant and dominate much of agribusiness. Transfer of the expert knowledge concerning remote sensing based crop yield production into a specific expert system is the key program in this study. A knowledge base consisting of a root frame, CROP-YIELD-FORECAST, and four subframes, namely, SATELLITE, PLANT-PHYSIOLOGY, GROUND, and MODEL were developed to accommodate the production rules obtained from the domain expert. The expert system shell Personal Consultant Plus version 4.0. was used for this purpose. An external geographic program was integrated to the system. This project is the first part of a completely built expert system. The study reveals that much effort was given to the development of the rules. Such effort is inevitable if workable, efficient, and accurate rules are desired. Furthermore, abundant help statements and graphics were included. Internal and external display routines add to the visual capability of the system. The work results in a useful tool for the client for making decisions on crop yield production

Interaction of Recoiling Supermassive Black Holes with Stars in Galactic Nuclei

Supermassive black hole binaries (SMBHBs) are the products of frequent galaxy mergers. The coalescence of the SMBHBs is a distinct source of gravitational wave (GW) radiation. The detections of the strong GW radiation and their possible electromagnetic counterparts are essential. Numerical relativity suggests that the post-merger supermassive black hole (SMBH) gets a kick velocity up to 4000 km/s due to the anisotropic GW radiations. Here we investigate the dynamical co-evolution and interaction of the recoiling SMBHs and their galactic stellar environments with one million direct N-body simulations including the stellar tidal disruption by the recoiling SMBHs. Our results show that the accretion of disrupted stars does not significantly affect the SMBH dynamical evolution. We investigate the stellar tidal disruption rates as a function of the dynamical evolution of oscillating SMBHs in the galactic nuclei. Our simulations show that most of stellar tidal disruptions are contributed by the unbound stars and occur when the oscillating SMBHs pass through the galactic center. The averaged disruption rate is ~10^{-6} M_\odot yr^{-1}, which is about an order of magnitude lower than that by a stationary SMBH at similar galactic nuclei. Our results also show that a bound star cluster is around the oscillating SMBH of about ~ 0.7% the black hole mass. In addition, we discover a massive cloud of unbound stars following the oscillating SMBH. We also investigate the dependence of the results on the SMBH masses and density slopes of the galactic nuclei.Comment: 38 pages, 10 figues; accepted for publication in Ap

Nuclear Star-Forming Ring of the Milky Way: Simulations

We present hydrodynamic simulations of gas clouds in the central kpc region of the Milky Way that is modeled with a three-dimensional bar potential. Our simulations consider realistic gas cooling and heating, star Formation, and supernova feedback. A ring of dense gas clouds forms as a result of X-1-X-2 orbit transfer, and our potential model results in a ring radius of similar to 200 pc, which coincides with the extraordinary reservoir of dense molecular clouds in the inner bulge, the Central Molecular Zone (CMZ). The gas clouds accumulated in the CMZ can reach high enough densities to form stars, and with an appropriate choice of simulation parameters, we successfully reproduce the observed gas mass and the star Formation rate (SFR) in the CMZ, similar to 2 x 10(7) M-circle dot and similar to 0.1 M-circle dot yr(-1). Star Formation in our simulations takes place mostly in the outermost X-2 orbits, and the SFR per unit surface area outside the CMZ is much lower. These facts suggest that the inner Galactic bulge may harbor a mild version of the nuclear star-forming rings seen in some external disk galaxies. Furthermore, from the relatively small size of the Milky Way's nuclear bulge, which is thought to be a result of sustained star Formation in the CMZ, we infer that the Galactic inner bulge probably had a shallower density profile or stronger bar elongation in the past.Korea Research Foundation KRF-2008-013-C00037MEST of Korea R31-1001NASA NNG 05-GC37G, NNX 10-AF84GNYSTAR Faculty Development ProgramAstronom