13,941 research outputs found

    Intermediate-mass Black Holes in Galactic Nuclei

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    We present the first homogeneous sample of intermediate-mass black hole candidates in active galactic nuclei. Starting with broad-line active nuclei from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling relation to select a sample of 19 galaxies in the mass range M_BH ~ 8 x 10^4 - 10^6 solar masses. In contrast to the local active galaxy population, the host galaxies are ~1 mag fainter than M* and thus are probably late-type systems. The active nuclei are also faint, with M_g ~ -15 to -18 mag, while the bolometric luminosities are close to the Eddington limit. The spectral properties of the sample are compared to the related class of objects known as narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as observational analogues of primordial black holes, contributors to the integrated signal for future gravitational wave experiments, and as a valuable tool in the calibration of the M-sigma relation.Comment: 4 pages, 4 figures. To appear in "The Interplay among Black Holes, Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado, Brazil), eds Th. Storchi Bergmann, L.C. Ho, H.R. Schmit

    SOFIP: A Short Orbital Flux Integration Program

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    A computer code was developed to evaluate the space radiation environment encountered by geocentric satellites. The Short Orbital Flux Integration Program (SOFIP) is a compact routine of modular compositions, designed mostly with structured programming techniques in order to provide core and time economy and ease of use. The program in its simplest form produces for a given input trajectory a composite integral orbital spectrum of either protons or electrons. Additional features are available separately or in combination with the inclusion of the corresponding (optional) modules. The code is described in detail, and the function and usage of the various modules are explained. A program listing and sample outputs are attached

    Feedback In Luminous Obscured Quasars

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    We use spatially resolved long-slit spectroscopy from Magellan to investigate the extent, kinematics, and ionization structure in the narrow-line regions of 15 luminous, obscured quasars with z < 0.5. Increasing the dynamic range in luminosity by an order of magnitude, as well as improving the depth of existing observations by a similar factor, we revisit relations between narrow-line region size and the luminosity and linewidth of the narrow emission lines. We find a slope of 0.22 +/- 0.04 for the power-law relationship between size and luminosity, suggesting that the nebulae are limited by availability of gas to ionize at these luminosities. In fact, we find that the active galactic nucleus is effectively ionizing the interstellar medium over the full extent of the host galaxy. Broad (similar to 300-1000 km s(-1)) linewidths across the galaxies reveal that the gas is kinematically disturbed. Furthermore, the rotation curves and velocity dispersions of the ionized gas remain constant out to large distances, in striking contrast to normal and starburst galaxies. We argue that the gas in the entire host galaxy is significantly disturbed by the central active galactic nucleus. While only similar to 10(7)-10(8) M-circle dot worth of gas are directly observed to be leaving the host galaxies at or above their escape velocities, these estimates are likely lower limits because of the biases in both mass and outflow velocity measurements and may in fact be in accord with expectations of recent feedback models. Additionally, we report the discovery of two dual obscured quasars, one of which is blowing a large-scale (similar to 10 kpc) bubble of ionized gas into the intergalactic medium.NSF AST-0548198Astronom

    The Bright and the Dark Side of Malin 1

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    Malin 1 has long been considered a prototype giant, dark matter dominated Low Surface Brightness galaxy. Two recent studies, one based on a re-analysis of VLA HI observations and the other on an archival Hubble I-band image, throw a new light on this enigmatic galaxy and on its dark/luminous matter properties.Comment: 4 pages, 3 figures, to appear in the Proceedings of the 41st ESLAB Symposium "The Impact of HST on European Astronomy", 29 May to 1 June 2007, ESTEC, Noordwijk, N

    A Stellar Dynamical Mass Measurement of the Black Hole in NGC 3998 from Keck Adaptive Optics Observations

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    We present a new stellar dynamical mass measurement of the black hole in the nearby, S0 galaxy NGC 3998. By combining laser guide star adaptive optics observations obtained with the OH-Suppressing Infrared Imaging Spectrograph on the Keck II telescope with long-slit spectroscopy from the Hubble Space Telescope and the Keck I telescope, we map out the stellar kinematics on both small spatial scales, well within the black hole sphere of influence, and on large scales. We find that the galaxy is rapidly rotating and exhibits a sharp central peak in the velocity dispersion. Using the kinematics and the stellar luminosity density derived from imaging observations, we construct three-integral, orbit-based, triaxial stellar dynamical models. We find the black hole has a mass of M_BH = (8.1_{-1.9}^{+2.0}) x 10^8 M_sun, with an I-band stellar mass-to-light ratio of M/L = 5.0_{-0.4}^{+0.3} M_sun/L_sun (3-sigma uncertainties), and that the intrinsic shape of the galaxy is very round, but oblate. With the work presented here, NGC 3998 is now one of a very small number of galaxies for which both stellar and gas dynamical modeling have been used to measure the mass of the black hole. The stellar dynamical mass is nearly a factor of four larger than the previous gas dynamical black hole mass measurement. Given that this cross-check has so far only been attempted on a few galaxies with mixed results, carrying out similar studies in other objects is essential for quantifying the magnitude and distribution of the cosmic scatter in the black hole mass - host galaxy relations.Comment: 19 pages, 15 figures, accepted for publication in Ap

    Exploring Counselors’ Personal Guiding Theories: A Qualitative Study in Portraiture

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    A personal guiding theory of counseling is an important component of professional identity development for counselors. We utilized the qualitative methodology of portraiture to explore how professional counselors understand their own personal guiding theories of counseling. Three research portraits are shared that demonstrate how participants use the counseling relationship as the means to incorporate their personal guiding theories into their work with clients. Implications for counselors and counselor educators and future research are presented

    Violation of particle number conservation in the it GW approximation

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    We present a nontrivial model system of interacting electrons that can be solved analytically in the GW approximation. We obtain the particle number from the GW Green's function strictly analytically, and prove that there is a genuine violation of particle number conservation if the self-energy is calculated non-self-consistently from a zeroth order Green's function, as done in virtually all practical implementations. We also show that a simple shift of the self-energy that partially restores self-consistency reduces the numerical deviation significantly

    The current prevalence of child sexual abuse worldwide: a systematic review and meta-analysis

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    Objectives: Systematic reviews on prevalence estimates of child sexual abuse (CSA) worldwide included studies with adult participants referring on a period of abuse of about 50years. Therefore we aimed to describe the current prevalence of CSA, taking into account geographical region, type of abuse, level of country development and research methods. Methods: We included studies published between 2002 and 2009 that reported CSA in children below 18years. We performed a random effects meta-analysis and analyzed moderator variables by meta-regression. Results: Fifty-five studies from 24 countries were included. According to four predefined types of sexual abuse, prevalence estimates ranged from 8 to 31% for girls and 3 to 17% for boys. Nine girls and 3 boys out of 100 are victims of forced intercourse. Heterogeneity between primary studies was high in all analyses. Conclusions: Our results based on most recent data confirm results from previous reviews with adults. Surveys in children offer most recent estimates of CSA. Reducing heterogeneity between studies might be possible by standardized measures to make data more meaningful in international comparison
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