VLASSICK: The VLA Sky Survey in the Central Kiloparsec

At a distance of 8 kpc, the center of our Galaxy is the nearest galactic nucleus, and has been the subject of numerous key projects undertaken by great observatories such as Chandra, Spitzer, and Herschel. However, there are still no surveys of molecular gas properties in the Galactic center with less than 30" (1 pc) resolution. There is also no sensitive polarization survey of this region, despite numerous nonthermal magnetic features apparently unique to the central 300 parsecs. In this paper, we outline the potential the VLASS has to fill this gap. We assess multiple considerations in observing the Galactic center, and recommend a C-band survey with 10 micro-Jy continuum RMS and sensitive to molecular gas with densities greater than 10^4 cm^{-3}, covering 17 square degrees in both DnC and CnB configurations ( resolution ~5"), totaling 750 hours of observing time. Ultimately, we wish to note that the upgraded VLA is not just optimized for fast continuum surveys, but has a powerful correlator capable of simultaneously observing continuum emission and dozens of molecular and recombination lines. This is an enormous strength that should be fully exploited and highlighted by the VLASS, and which is ideally suited for surveying the center of our Galaxy.Comment: 13 pages, 3 figures, a White Paper submitted to provide input in planning the Very Large Array Sky Surve

Stellar Populations of the Sagittarius Dwarf Irregular Galaxy

We present deep BVRI CCD photometry of the stars in the dwarf irregular galaxy SagDIG. The color-magnitude diagrams of the measured stars in SagDIG show a blue plume which consists mostly of young stellar populations, and a well-defined red giant branch (RGB). The foreground reddening of SagDIG is estimated to be E(B-V)=0.06. The tip of the RGB is found to be at I_(TRGB)=21.55 +/- 0.10 mag. From this the distance to this galaxy is estimated to be d = 1.18 +/- 0.10 Mpc. This result, combined with its velocity information, shows that it is a member of the Local Group. The mean metallicity of the red giant branch is estimated to be [Fe/H] < -2.2 dex. This shows that SagDIG is one of the most metal-poor galaxies. Total magnitudes of SagDIG (< r_H (= 107 arcsec)) are derived to be B^T=13.99 mag, V^T=13.58 mag, R^T=13.19 mag, and I^T=12.88 mag, and the corresponding absolute magnitudes are M_B=-11.62 mag, M_V=-11.97 mag, M_R=-12.33 mag, and M_I=-12.60 mag. Surface brightness profiles of the central part of SagDIG are approximately fit by a King model with a core concentration parameter c = log (r_t / r_c) ~ 0.6, and those of the outer part follow an exponential law with a scale length of 37 arcsec. The central surface brightness is measured to be mu_B (0) = 24.21 mag arcsec^(-2) and mu_V (0) =23.91 mag arcsec^(-2). The magnitudes and colors of the brightest blue and red stars in SagDIG (BSG and RSG) are measured to be, respectively, _BSG = 19.89 +/- 0.13 mag, _BSG = 0.08 +/- 0.07 mag, _RSG = 20.39 +/- 0.10 mag, and _RSG = 1.29 +/- 0.12 mag. The corresponding absolute magnitudes are derived to be _BSG = -5.66 mag and _RSG = -5.16 mag, which are about one magnitude fainter than those expected from conventional correlations with galaxy luminosity.Comment: 16 pages(AASLaTeX), 10 Postscript figures, Accepted for publication in Astronomical Journal, 200

THE COMPARISON OF PHYSICAL PROPERTIES DERIVED FROM GAS AND DUST IN A MASSIVE STAR-FORMING REGION

We explore the relationship between gas and dust in a massive star-forming region by comparing the physical properties derived from each. We compare the temperatures and column densities in a massive star-forming Infrared Dark Cloud (G32.02+0.05), which shows a range of evolutionary states, from quiescent to active. The gas properties were derived using radiative transfer modeling of the (1,1), (2,2), and (4,4) transitions of NH3 on the Karl G. Jansky Very Large Array, while the dust temperatures and column densities were calculated using cirrus-subtracted, modified blackbody fits to Herschel data. We compare the derived column densities to calculate an NH3 abundance, χ$_{{\rm NH}_{3}}$ = 4.6 × 10–8. In the coldest star-forming region, we find that the measured dust temperatures are lower than the measured gas temperatures (mean and standard deviations T dust, avg ~ 11.6 ± 0.2 K versus T gas, avg ~ 15.2 ± 1.5 K), which may indicate that the gas and dust are not well-coupled in the youngest regions (~0.5 Myr) or that these observations probe a regime where the dust and/or gas temperature measurements are unreliable. Finally, we calculate millimeter fluxes based on the temperatures and column densities derived from NH3, which suggest that millimeter dust continuum observations of massive star-forming regions, such as the Bolocam Galactic Plane Survey or ATLASGAL, can probe hot cores, cold cores, and the dense gas lanes from which they form, and are generally not dominated by the hottest core

High Angular Resolution JHK Imaging of the Centers of the Metal-Poor Globular Clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92)

The Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) has been used to obtain high angular resolution JHK images of the centers of the metal-poor globular clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92). The color-magnitude diagrams (CMDs) derived from these data include the upper main sequence and most of the red giant branch (RGB), and the cluster sequences agree with published photometric measurements of bright stars in these clusters. The photometric accuracy is limited by PSF variations, which introduce systematic errors of a few hundredths of a magnitude near the AO reference star. The clusters are paired according to metallicity, and the near-infrared CMDs and luminosity functions are used to investigate the relative ages within each pair. The near-infrared CMDs provide the tightest constraints on the relative ages of the classical second parameter pair NGC5272 and NGC6205, and indicate that these clusters have ages that differ by no more than +/- 1 Gyr. These results thus support the notion that age is not the second parameter. We tentatively conclude that NGC6287 and NGC6341 have ages that differ by no more than +/- 2 Gyr. However, the near-infrared spectral energy distributions of stars in NGC6287 appear to differ from those of stars in outer halo clusters, bringing into question the validity of this age estimate.Comment: 22 pages, 17 figures. To be published in the Astronomical Journa

Micro‐cultures of Conflict: Couple‐level Perspectives on Reasons for and Causes of Intimate Partner Violence in Young Adulthood

Objective To highlight the development of young adult couples\u27 shared understandings about reasons for conflict in their relationships, views about why some disagreements included the use of aggression ( causes ), and gendered perspectives on these relationship dynamics. Background Feminist theories have centered on relationship dynamics associated with intimate partner violence (IPV), but have focused primarily on men\u27s concerns (e.g., jealousy) and use of violence as a means of control over female partners. The current analysis drew on symbolic interaction theory as a framework for exploring couple-level concerns, and ways in which dyadic communication contributes to these understandings, or what can be considered “micro-cultures” of conflict. Method The study relied on in-depth interviews with a heterogeneous sample of IPV-experienced young adults who had participated in a larger longitudinal study (Toledo Adolescent Relationships Study [TARS]) and separate interviews with their partners (n = 90). Results Analyses revealed that women\u27s concerns about men\u27s actions (e.g., infidelity) were frequently cited as reasons for serious conflicts, and showed significant concordance in partners\u27 reports. Shared understandings sometimes extended to views on the role of more distal causes (e.g., family background) and the meaning(s) of each partner\u27s use of aggression. Gendered dynamics included men\u27s tendency to minimize women\u27s concerns, and both partners\u27 more open discussions of women\u27s perpetration. Conclusions Theories of IPV and associated programmatic efforts should include attention to the social construction of these micro-cultures, as these shared meanings affect behavior, are potentially malleable, and add to the more intuitive focus on one-sided forces of control and constraint

Towards a multi-tracer timeline of star formation in the LMC -- I.\ Deriving the lifetimes of H\,{\sc i} clouds

The time-scales associated with the various stages of the star formation process remain poorly constrained. This includes the earliest phases of star formation, during which molecular clouds condense out of the atomic interstellar medium. We present the first in a series of papers with the ultimate goal of compiling the first multi-tracer timeline of star formation, through a comprehensive set of evolutionary phases from atomic gas clouds to unembedded young stellar populations. In this paper, we present an empirical determination of the lifetime of atomic clouds using the Uncertainty Principle for Star Formation formalism, based on the de-correlation of H$\alpha$ and H\,{\sc i} emission as a function of spatial scale. We find an atomic gas cloud lifetime of 48$\substack{+13\\-8}$\,Myr. This timescale is consistent with the predicted average atomic cloud lifetime in the LMC (based on galactic dynamics) that is dominated by the gravitational collapse of the mid-plane ISM. We also determine the overlap time-scale for which both H\,{\sc i} and H$\alpha$ emission are present to be very short ($t_{over}<1.7$\,Myr), consistent with zero, indicating that there is a near-to-complete phase change of the gas to a molecular form in an intermediary stage between H\,{\sc i} clouds and H\,{\sc ii} regions. We utilise the time-scales derived in this work to place empirically determined limits on the time-scale of molecular cloud formation. By performing the same analysis with and without the 30 Doradus region included, we find that the most extreme star forming environment in the LMC has little effect on the measured average atomic gas cloud lifetime. By measuring the lifetime of the atomic gas clouds, we place strong constraints on the physics that drives the formation of molecular clouds and establish a solid foundation for the development of a multi-tracer timeline of star formation in the LMC

Criminal Justice Involvement and Young Adult Health: The Role of Adolescent Health Risks and Stress

Background: Although some studies have found that incarceration is associated with young adults’ poor health, confounding factors including adolescent health risks, and mediating influences such as stress have not been examined in the same study. We assessed whether variation in criminal justice system experience (none, arrest only, incarceration) influenced young adults’ self-reported depressive symptoms and poor physical health after accounting for prospective risks to health including adolescent health risks. We then assessed whether stress mediated associations between criminal justice involvement and the two health indicators. Methods: Data are from Toledo Adolescent Relationships Study (TARS) (n =990), which included young adults, age 22-29, who have matured during the era characterized by mass incarceration. The dependent variables included a depressive symptoms scale and self-reported poor health. The adolescent health risks included economic disadvantage, body mass index, delinquency, problems with drugs, and prior depressive symptoms. We considered stress as a mediating variable. Sociodemographic characteristics included race/ethnicity, age, and gender. We used ordinary least squares regression and logistic regression analyses. We tested gender, race/ethnicity, and age interactions. Results: In multivariable models, incarceration, and adolescent health risks (economic disadvantage, prior depression, problems with drugs) were associated with young adults’ depressive symptoms, and stress was a mediating influence. Adolescent delinquency and stress, but not incarceration, were significantly associated with young adults’ self-reported poor health. Conclusion: This study provided a more nuanced understanding of incarceration and health by accounting for several key confounding factors and testing stress as a mechanism underlying the association. Care for prisoner health during and after incarceration is important for successful reintegration

Criminal Justice Involvement and Young Adult Health: The Role of Adolescent Health Risks and Stress

Background: Although some studies have found that incarceration is associated with young adults\u27 poor health, confounding factors including adolescent health risks, and mediating influences such as stress have not been examined in the same study. We assessed whether variation in criminal justice system experience (none, arrest only, incarceration) influenced young adults\u27 self-reported depressive symptoms and poor physical health after accounting for prospective risks to health including adolescent health risks. We then assessed whether stress mediated associations between criminal justice involvement and the two health indicators. Methods: Data are from Toledo Adolescent Relationships Study (TARS) (n =990), which included young adults, age 22-29, who have matured during the era characterized by mass incarceration. The dependent variables included a depressive symptoms scale and self-reported poor health. The adolescent health risks included economic disadvantage, body mass index, delinquency, problems with drugs, and prior depressive symptoms. We considered stress as a mediating variable. Sociodemographic characteristics included race/ethnicity, age, and gender. We used ordinary least squares regression and logistic regression analyses. We tested gender, race/ethnicity, and age interactions. Results: In multivariable models, incarceration, and adolescent health risks (economic disadvantage, prior depression, problems with drugs) were associated with young adults\u27 depressive symptoms, and stress was a mediating influence. Adolescent delinquency and stress, but not incarceration, were significantly associated with young adults\u27 self-reported poor health. Conclusion: This study provided a more nuanced understanding of incarceration and health by accounting for several key confounding factors and testing stress as a mechanism underlying the association. Care for prisoner health during and after incarceration is important for successful reintegration

High Performance Algorithms for Counting Collisions and Pairwise Interactions

The problem of counting collisions or interactions is common in areas as computer graphics and scientific simulations. Since it is a major bottleneck in applications of these areas, a lot of research has been carried out on such subject, mainly focused on techniques that allow calculations to be performed within pruned sets of objects. This paper focuses on how interaction calculation (such as collisions) within these sets can be done more efficiently than existing approaches. Two algorithms are proposed: a sequential algorithm that has linear complexity at the cost of high memory usage; and a parallel algorithm, mathematically proved to be correct, that manages to use GPU resources more efficiently than existing approaches. The proposed and existing algorithms were implemented, and experiments show a speedup of 21.7 for the sequential algorithm (on small problem size), and 1.12 for the parallel proposal (large problem size). By improving interaction calculation, this work contributes to research areas that promote interconnection in the modern world, such as computer graphics and robotics.Comment: Accepted in ICCS 2019 and published in Springer's LNCS series. Supplementary content at https://mjsaldanha.com/articles/1-hpc-ssp

The Distance of the First Overtone RR Lyrae Variables in the MACHO LMC Database: A New Method to Correct for the Effects of Crowding

Previous studies have indicated that many of the RR Lyrae variables in the LMC have properties similar to the ones in the Galactic globular cluster M3. Assuming that the M3 RR Lyrae variables follow the same relationships among period, temperature, amplitude and Fourier phase parameter phi31 as their LMC counterparts, we have used the M3 phi31-logP relation to identify the M3-like unevolved first overtone RR Lyrae variables in 16 fields near the LMC bar. The temperatures of these variables were calculated from the M3 logP-logTe relation so that the extinction could be derived for each star separately. Since blended stars have lower amplitudes for a given period, the period amplitude relation should be a useful tool for identifying which stars are affected by crowding. We find that the low amplitude stars are brighter. We remove them from the sample and derive an LMC distance modulus 18.49+/-0.11.Comment: 30 pages, 7 figures, accepted for publication in the Astronomical Journa