Nuclear Black Hole Formation in Clumpy Galaxies at High Redshift

Massive stellar clumps in high redshift galaxies interact and migrate to the center to form a bulge and exponential disk in <1 Gyr. Here we consider the fate of intermediate mass black holes (BHs) that might form by massive-star coalescence in the dense young clusters of these disk clumps. We find that the BHs move inward with the clumps and reach the inner few hundred parsecs in only a few orbit times. There they could merge into a supermassive BH by dynamical friction. The ratio of BH mass to stellar mass in the disk clumps is approximately preserved in the final ratio of BH to bulge mass. Because this ratio for individual clusters has been estimated to be ~10^{-3}, the observed BH-to-bulge mass ratio results. We also obtain a relation between BH mass and bulge velocity dispersion that is compatible with observations of present-day galaxies.Comment: 10 pages, 3 figures, accepted by Ap

Rapid formation of exponential disks and bulges at high redshift from the dynamical evolution of clump cluster and chain galaxies

Many galaxies at high redshift have peculiar morphologies dominated by 10^8-10^9 Mo kpc-sized clumps. Using numerical simulations, we show that these "clump clusters" can result from fragmentation in gravitationally unstable primordial disks. They appear as "chain galaxies" when observed edge-on. In less than 1 Gyr, clump formation, migration, disruption, and interaction with the disk cause these systems to evolve from initially uniform disks into regular spiral galaxies with an exponential or double-exponential disk profile and a central bulge. The inner exponential is the initial disk size and the outer exponential is from material flung out by spiral arms and clump torques. A nuclear black hole may form at the same time as the bulge from smaller black holes that grow inside the dense cores of each clump. The properties and lifetimes of the clumps in our models are consistent with observations of the clumps in high redshift galaxies, and the stellar motions in our models are consistent with the observed velocity dispersions and lack of organized rotation in chain galaxies. We suggest that violently unstable disks are the first step in spiral galaxy formation. The associated starburst activity gives a short timescale for the initial stellar disk to form.Comment: ApJ Accepted, 13 pages, 9 figure

A Turbulent Origin for Flocculent Spiral Structure in Galaxies

The flocculent structure of star formation in 7 galaxies has a Fourier transform power spectrum for azimuthal intensity scans with a power law slope that increases systematically from -1 at large scales to -1.7 at small scales. This is the same pattern as in the power spectra for azimuthal scans of HI emission in the Large Magellanic Clouds and for flocculent dust clouds in galactic nuclei. The steep part also corresponds to the slope of -3 for two-dimensional power spectra that have been observed in atomic and molecular gas surveys of the Milky Way and the Large and Small Magellanic Clouds. The same power law structure for star formation arises in both flocculent and grand design galaxies, which implies that the star formation process is the same in each. Fractal Brownian motion models that include discrete stars and an underlying continuum of starlight match the observations if all of the emission is organized into a global fractal pattern with an intrinsic 1D power spectrum having a slope between 1.3 and 1.8. We suggest that the power spectrum of optical light in galaxies is the result of turbulence, and that large-scale turbulent motions are generated by sheared gravitational instabilities which make flocculent spiral arms first and then cascade to form clouds and clusters on smaller scales.Comment: accepted for ApJ, 31 pg, 9 figure

Fractal Structure in Galactic Star Fields

The fractal structure of star formation on large scales in disk galaxies is studied using the size distribution function of stellar aggregates in kpc-scale star fields. Achival HST images of 10 galaxies are Gaussian smoothed to define the aggregates, and a count of these aggregates versus smoothing scale gives the fractal dimension. Fractal and Poisson models confirm the procedure. The fractal dimension of star formation in all of the galaxies is ~2.3. This is the same as the fractal dimension of interstellar gas in the Milky Way and nearby galaxies, suggesting that star formation is a passive tracer of gas structure defined by self-gravity and turbulence. Dense clusters like the Pleiades form at the bottom of the hierarchy of structures, where the protostellar gas is densest. If most stars form in such clusters, then the fractal arises from the spatial distribution of their positions, giving dispersed star fields from continuous cluster disruption. Dense clusters should have an upper mass limit that increases with pressure, from ~1000 Msun in regions like the Solar neighborhood to one million Msun in starbursts.Comment: 7 pages, 3 figures, to be published in Astronomical Journal, Vol 121, March 200

Risk Factors for Severe Violence in Intimate Partner Stalking Situations: An Analysis of Police Records

Stalkers can be violent, and empirical studies have sought to identify factors associated with violence perpetrated by the stalker. Most of these works view physical violence as a homogeneous construct and do not differentiate between moderate and severe violence. The present study aims to identify correlates of nonviolent, moderate, and severe physical violence within an archival sample of 369 domestically violent police incident reports, where stalking behavior was indicated. The incident reports utilized in this study occurred between 2013 and 2017, among intimate or ex-intimate partners. The present study explored 12 independent variables that have yielded mixed findings in previous stalking violence literature, as well as two previously untested factors of nonfatal strangulation and child contact. The police records were coded for severity of physical violence using the Revised Conflict Tactics Scale and analyzed using a logistic regression. The regression analysis revealed significant independent associations between the outcome variable of severe physical violence and child contact, history of domestic violence, separation, nonfatal strangulation, jealousy, previous injury, and victim belief of potential harm. These results may help produce pragmatic recommendations for law enforcement agencies and other relevant bodies who seek to identify victims at risk of severe violence, increasing the potential for early intervention and prevention of physical harm. The awareness of factors that are shown to be related to serious physical violence may assist first responders in recognizing which victims may be at risk of serious harm, as well as effectively allocating any appropriate resources to reduce and prevent harm

Martial arts as a mental health intervention for children? Evidence from the ECLS-K

<p>Abstract</p> <p>Background</p> <p>Martial arts studios for children market their services as providing mental health outcomes such as self-esteem, self-confidence, concentration, and self-discipline. It appears that many parents enroll their children in martial arts in hopes of obtaining such outcomes. The current study used the data from the Early Childhood Longitudinal Study, Kindergarten class of 1998-1999, to assess the effects of martial arts upon such outcomes as rated by classroom teachers.</p> <p>Methods</p> <p>The Early Childhood Longitudinal Study used a multistage probability sampling design to gather a sample representative of U.S. children attending kindergarten beginning 1998. We made use of data collected in the kindergarten, 3^rdgrade, and 5^thgrade years. Classroom behavior was measured by a rating scale completed by teachers; participation in martial arts was assessed as part of a parent interview. The four possible combinations of participation and nonparticipation in martial arts at time 1 and time 2 for each analysis were coded into three dichotomous variables; the set of three variables constituted the measure of participation studied through regression. Multiple regression was used to estimate the association between martial arts participation and change in classroom behavior from one measurement occasion to the next. The change from kindergarten to third grade was studied as a function of martial arts participation, and the analysis was replicated studying behavior change from third grade to fifth grade. Cohen's f²effect sizes were derived from these regressions.</p> <p>Results</p> <p>The martial arts variable failed to show a statistically significant effect on behavior, in either of the regression analyses; in fact, the f²effect size for martial arts was 0.000 for both analyses. The 95% confidence intervals for regression coefficients for martial arts variables have upper and lower bounds that are all close to zero. The analyses not only fail to reject the null hypothesis, but also render unlikely a population effect size that differs greatly from zero.</p> <p>Conclusion</p> <p>The data from the ECLS-K fail to support enrolling children in martial arts to improve mental health outcomes as measured by classroom teachers.</p

Design, development and validity testing of the Gang Affiliation Risk Measure (GARM)

This study aimed to create a measure of risk for gang affiliation, for use in the UK. A pilot stage invited gang affiliated and non-gang affiliated participants between the ages of 16–25 years to retrospectively self-report on 58 items of risk exposure at the age of 11 years. Based on performance of these items, a 26-item measure was developed and administered to a main study sample (n=185) of gang affiliated and non-gang affiliated participants. Categorical Principal Component Analysis was applied to data, yielding a single-factor solution (historic lack of safety and current perception of threat). A 15-item gang affiliation risk measure (GARM) was subsequently created. The GARM demonstrated good internal consistency, construct validity and discriminative ability. Items from the GARM were then transformed to read prospectively, resulting in a test measure for predictive purposes (T-GARM). The T-GARM requires further validation regarding its predictive utility and generalisability. However, this study has resulted in the first measure of gang affiliation, with promising results

Elliptical Galaxies and Bulges of Disk Galaxies: Summary of Progress and Outstanding Issues

This is the summary chapter of a review book on galaxy bulges. Bulge properties and formation histories are more varied than those of ellipticals. I emphasize two advances: 1 - "Classical bulges" are observationally indistinguishable from ellipticals, and like them, are thought to form by major galaxy mergers. "Disky pseudobulges" are diskier and more actively star-forming (except in S0s) than are ellipticals. Theys are products of the slow ("secular") evolution of galaxy disks: bars and other nonaxisymmetries move disk gas toward the center, where it starbursts and builds relatively flat, rapidly rotating components. This secular evolution is a new area of galaxy evolution work that complements hierarchical clustering. 2 - Disks of high-redshift galaxies are unstable to the formation of mass clumps that sink to the center and merge - an alternative channel for the formation of classical bulges. I review successes and unsolved problems in the formation of bulges+ellipticals and their coevolution (or not) with supermassive black holes. I present an observer's perspective on simulations of dark matter galaxy formation including baryons. I review how our picture of the quenching of star formation is becoming general and secure at redshifts z < 1. The biggest challenge is to produce realistic bulges+ellipticals and disks that overlap over a factor of 10**3 in mass but that differ from each other as observed over that whole range. Second, how does hierarchical clustering make so many giant, bulgeless galaxies in field but not cluster environments? I argue that we rely too much on AGN and star-formation feedback to solve these challenges.Comment: 46 pages, 10 postscript figures, accepted for publication in Galactic Bulges, ed. E. Laurikainen, R. F. Peletier, & D. A. Gadotti (New York: Springer), in press (2015

Ocular Shock Front in the Colliding Galaxy IC 2163

The final, definitive version of this paper has been published in The Astrophysical Journal, 831:161 (13pp), 2016 November 4, doi:10.3847/0004-637X/831/2/161 © 2016. The American Astronomical Society. All rights reserved.ALMA observations in the CO 1 - 0 line of the interacting galaxies IC 2163 and NGC 2207 at 2" x 1.5" resolution reveal how the encounter drives gas to pile up in narrow, ~ 1 kpc wide, "eyelids" in IC 2163. IC 2163 and NGC 2207 are involved in a grazing encounter, which has led to development in IC 2163 of an eye-shaped (ocular) structure at mid-radius and two tidal arms. The CO data show that there are large velocity gradients across the width of each eyelid, with a mixture of radial and azimuthal streaming of gas at the outer edge of the eyelid relative to its inner edge. The sense of the radial streaming in the eyelids is consistent with the idea that gas from the outer part of IC 2163 flows inward until its radial streaming slows down abruptly and the gas piles up in the eyelids. The radial compression at the eyelids causes an increase in the gas column density by direct radial impact and also leads to a high rate of shear. We find a strong correlation between the molecular column densities and the magnitude of dv/dR across the width of the eyelid at fixed values of azimuth. Substantial portions of the eyelids have high velocity dispersion in CO, indicative of elevated turbulence there.Peer reviewedFinal Accepted Versio