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

Electron Beam Induced Luminescence of SiO2 Optical Coatings

Optical coatings of disordered thin film SiO2/SiOx dielectric samples on reflective metal substrates exhibited cathodoluminescence under electron beam irradiation. Measurements of the absolute radiance and emission spectra as functions of incident electron energy, flux and power over a range of sample temperatures are reported. Radiance reached a saturation plateau at high incident electron power. Well below saturation radiance scaled with deposited power, that is linearly with incident power for lower-energy non-penetrating electrons and decreasing with increasing energy for penetrating radiation. Four bands were observed in spectral measurements from 300 nm to 1000 nm. Changes in peak intensity and shifts in peak energies as functions of temperature are described. The observations are explained in terms of a simple disordered band theory model and the transitions that take place between electrons in extended conduction states and localized trapped states associated with structural or compositional defects in the highly disordered insulating materials; this provides a fundamental basis for understanding the dependence of cathodoluminescence on irradiation time, incident flux and energy, and sample thickness and temperature

Dust Streamers in the Virgo Galaxy M86 from Ram Pressure Stripping of its Companion VCC 882

The giant elliptical galaxy M86 in Virgo has a ~28 kpc long dust trail inside its optical halo that points toward the nucleated dwarf elliptical galaxy, VCC 882. The trail seems to be stripped material from the dwarf. Extinction measurements suggest that the ratio of the total gas mass in the trail to the blue luminosity of the dwarf is about unity, which is comparable to such ratios in dwarf irregular galaxies. The ram pressure experienced by the dwarf galaxy in the hot gaseous halo of M86 was comparable to the internal gravitational binding energy density of the presumed former gas disk in VCC 882. Published numerical models of this case are consistent with the overall trail-like morphology observed here. Three concentrations in the trail may be evidence for the predicted periodicity of the mass loss. The evaporation time of the trail is comparable to the trail age obtained from the relative speed of the galaxies and the trail length. Thus the trail could be continuously formed from stripped replenished gas if the VCC 882 orbit is bound. However, the high gas mass and the low expected replenishment rate suggest that this is only the first stripping event. Implications for the origin of nucleated dwarf ellipticals are briefly discussed.Comment: 22 pages, 7 figures, Astronomical Journal, August 2000, in pres

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

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

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

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