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The Evolution Of Stellar Structures In Dwarf Galaxies, N. Bastian, D. R. Weisz, E. D. Skillman, K. B.W. Mc Quinn, A E. Dolphin, R. A. Gutermuth 2010 University of Massachusetts - Amherst

The Evolution Of Stellar Structures In Dwarf Galaxies, N. Bastian, D. R. Weisz, E. D. Skillman, K. B.W. Mc Quinn, A E. Dolphin, R. A. Gutermuth

Astronomy Department Faculty Publication Series

We present a study of the variation of spatial structure of stellar populations within dwarf galaxies as a function of the population age. We use deep Hubble Space Telescope/Advanced Camera for Surveys imaging of nearby dwarf galaxies in order to resolve individual stars and create composite colour-magnitude diagrams (CMDs) for each galaxy. Using the obtained CMDs, we select Blue Helium Burning stars (BHeBs), which can be unambiguously age-dated by comparing the absolute magnitude of individual stars with stellar isochrones. Additionally, we select a very young (<10 >Myr) population of OB stars for a subset of the galaxies based on the ...


The Mass Distribution Of Starless And Protostellar Cores In Gould Belt Clouds, Sarah I. Sadavoy, James Di Francesco, Sylvain Bontemps, S. Thomas Megeath, Luisa M. Rebull, Erin Allgaier, Sean Carey, Robert Gutermuth 2010 University of Massachusetts - Amherst

The Mass Distribution Of Starless And Protostellar Cores In Gould Belt Clouds, Sarah I. Sadavoy, James Di Francesco, Sylvain Bontemps, S. Thomas Megeath, Luisa M. Rebull, Erin Allgaier, Sean Carey, Robert Gutermuth

Astronomy Department Faculty Publication Series

Using data from the SCUBA Legacy Catalogue (850 μm) and Spitzer Space Telescope (3.6-70 μm), we explore dense cores in the Ophiuchus, Taurus, Perseus, Serpens, and Orion molecular clouds. We develop a new method to discriminate submillimeter cores found by Submillimeter Common-User Bolometer Array (SCUBA) as starless or protostellar, using point source photometry from Spitzer wide field surveys. First, we identify infrared sources with red colors associated with embedded young stellar objects (YSOs). Second, we compare the positions of these YSO candidates to our submillimeter cores. With these identifications, we construct new, self-consistent starless and protostellar core mass functions ...


Distance To U Pegasi By The Dde Algorithm, Todd R. Vaccaro, Dirk Terrell, Robert E. Wilson 2010 St. Cloud State University

Distance To U Pegasi By The Dde Algorithm, Todd R. Vaccaro, Dirk Terrell, Robert E. Wilson

Physics and Astronomy Faculty Publications

A distance is found for the W UMa type binary U Pegasi, with a newly modified version of the Wilson-Devinney program (W-D) that makes use of the direct distance estimation (DDE) algorithm. The reported distance of d=123.6pc is an average based on solutions for B and V data and a primary star temperature of 5800K. Standardized light curves (not differential), radial velocities, and a spectroscopic primary star temperature are input to the program. Differential corrections were performed for each light curve band along with the velocities for two primary temperatures that span 100K. Log10d is a ...


Dual Gamma-Ray Mission, S. Boggs, C. Wunderer, P. von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, J Greiner, E Grove, Dieter H. Hartmann 2010 Space Sciences Laboratory, University of California

Dual Gamma-Ray Mission, S. Boggs, C. Wunderer, P. Von Ballmoos, T. Takahashi, N. Gehrels, J. Tueller, M. Baring, J. Beacom, R. Diehl, J Greiner, E Grove, Dieter H. Hartmann

Publications

Gamma-rays at MeV energies provide a unique window on the high energy Universe, especially so for nuclear astrophysics. The potential for significant contributions, e.g., to the understanding of SNe Ia as well as the large potential for new discoveries has long been recognized, but technical progress in this challenging energy band has been slow. The groundbreaking discoveries of CGRO’s COMPTEL, however, have inspired and driven the development of powerful new instrumentation over the past decade. Novel detector technologies developed in the US and Japan enable compact Compton telescopes, greatly improving the efficiency and field-of-view achievable with this technique ...


The Magnetic Field Induced By A Lightning Strikes Indirect Effect Double Exponential Current Waveform, S L. Meredith, S K. Earles, I N. Kostanic, Niescja E. Turner 2010 Trinity University

The Magnetic Field Induced By A Lightning Strikes Indirect Effect Double Exponential Current Waveform, S L. Meredith, S K. Earles, I N. Kostanic, Niescja E. Turner

Physics and Astronomy Faculty Research

Problem statement: Develop a new formula which describes the magnetic field induced by a lightning strike's indirect effect double exponential current waveform. Approach: A novel approach for developing a closed-form solution for the magnetic field from the indirect effect double exponential current waveform will be presented. In the literature, models typically employ the pulse waveform to derive the corresponding electromagnetic fields. However, given the Department of Defense (DoD) has incorporated the double exponential current waveform as part of their "Electromagnetic Environmental Effects Requirements For Systems", we felt it important to develop a solution for the magnetic field which utilized ...


A New Method To Describe Image Theory For An Imperfect Conductor, S L. Meredith, S K. Earles, Niescja E. Turner 2010 Trinity University

A New Method To Describe Image Theory For An Imperfect Conductor, S L. Meredith, S K. Earles, Niescja E. Turner

Physics and Astronomy Faculty Research

Problem statement: Modify the equations associated with image theory in order to account for perfect and imperfect conductors. Approach: A novel approach for describing the application of image theory for an imperfect conductive surface was presented. The method presented here purposely downplays the physics of how image theory was employed to account for a charge which is in the presence of an imperfect conductive surface. In turn, it adopted an approach which focused on the geometry that existed between the charged particle and surface ground. In doing so, the proposed method formulated a solution that had minimized the complexity of ...


High-Resolution Cavity-Enhanced Spectroscopy Of Molecular Ion Beams, Manori Perera, Andrew Mills, Brian Siller, Michael Porambo, Kyle Crabtree, Carrie Kauffman, Holger Kreckel, Benjamin McCall 2010 Illinois Wesleyan University

High-Resolution Cavity-Enhanced Spectroscopy Of Molecular Ion Beams, Manori Perera, Andrew Mills, Brian Siller, Michael Porambo, Kyle Crabtree, Carrie Kauffman, Holger Kreckel, Benjamin Mccall

Manori Perera

Molecular ions play a pivotal role in the chemistry of the interstellar medium due to their high reactivity even at low temperature. To identify these ions in interstellar space, it is essential to obtain high resolution laboratory spectra of potential interstellar ions for comparison to observational data. At the University of Illinois, we are developing a Sensitive, Cooled, Resolved Ion BEam Spectrometer (SCRIBES) that will allow us to obtain high resolution infrared direct absorption spectra of rotationally cold molecular ions in the absence of neutral molecules. This instrument can overcome many of the problems that arise when using other spectroscopic ...


A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids, Alejandro Garcia, A. Donev, J. B. Bell, B. Alder 2010 San Jose State University

A Hybrid Particle-Continuum Method For Hydrodynamics Of Complex Fluids, Alejandro Garcia, A. Donev, J. B. Bell, B. Alder

Faculty Publications

A previously developed hybrid particle-continuum method [J. B. Bell, A. Garcia, and S. A. Williams, Multiscale Model. Simul., 6 (2008), pp. 1256–1280] is generalized to dense fluids and two- and three-dimensional flows. The scheme couples an explicit fluctuating compressible Navier–Stokes solver with the isotropic direct simulation Monte Carlo (DSMC) particle method [A. Donev, A. L. Garcia, and B. J. Alder, J. Stat. Mech. Theory Exp., 2009 (2009), article P11008]. To achieve bidirectional dynamic coupling between the particle (microscale) and continuum (macroscale) regions, the continuum solver provides state-based boundary conditions to the particle subdomain, while the particle solver provides ...


Nlte Spectral Synthesis Based On 3d Mhd Convection Simulations - Understanding The Role Of The Magnetic Field In Intensity Variations, Margit Haberreiter, Sven Wedemeyer-Boehm, Mark Rast 2010 University of Colorado, Boulder

Nlte Spectral Synthesis Based On 3d Mhd Convection Simulations - Understanding The Role Of The Magnetic Field In Intensity Variations, Margit Haberreiter, Sven Wedemeyer-Boehm, Mark Rast

Astrophysical & Planetary Sciences Faculty Contributions

While the magnetic field is considered to be the main driver for Solar Spectral Irradiance (SSI) variations, the detailed physical mechanisms that explain this relation are not yet fully understood. In this paper we analyze the effect of small scale magnetic field on the intensity in Ca II 393.4 nm and various continuum wavelengths calculated with the NLTE radiative tranfer code SolMod3D. The code calculates NLTE level populations and line spectra based on 3D MHD simulations carried out with CO5BOLD. This enables us to study in great detail the effect of the varying small scale magnetic field on intensity ...


Synchrotron Radiation By Fast Fermions In Heavy-Ion Collisions, Kirill Tuchin 2010 Iowa State University

Synchrotron Radiation By Fast Fermions In Heavy-Ion Collisions, Kirill Tuchin

Physics and Astronomy Publications

We study the synchrotron radiation of gluons by fast quarks in strong magnetic field produced by colliding relativistic heavy ions. We argue that due to high electric conductivity of plasma, the magnetic field is almost constant during the entire plasma lifetime. We calculate the energy loss due to synchrotron radiation of gluons by fast quarks. We find that the typical energy loss per unit length for a light quark at the Large Hadron Collider is a few GeV per fm. This effect alone predicts quenching of jets with p⊥ up to about 20 GeV.We also show that the spin-flip ...


The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante 2010 Argelander-Institut für Astronomie

The Globular Cluster System Of Ngc 1399. V. Dynamics Of The Cluster System Out To 80 Kpc, Y. Schuberth, T. Richtler, M. Hilker, B. Dirsch, L. Bassino, Aaron J. Romanowsky, L. Infante

Faculty Publications

Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations (Richtler et al. 2004) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399. We have obtained 477 ...


Central Dark Matter Content Of Early-Type Galaxies: Scaling Relations And Connections With Star Formation Histories, N. R. Napolitano, Aaron J. Romanowsky, A. J. Tortora 2010 INAF

Central Dark Matter Content Of Early-Type Galaxies: Scaling Relations And Connections With Star Formation Histories, N. R. Napolitano, Aaron J. Romanowsky, A. J. Tortora

Faculty Publications

We examine correlations between masses, sizes and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar population models. We confirm an anticorrelation between the size and stellar age and go on to survey for trends with the central content of dark matter (DM). An average relation between the central DM density and galaxy size of 〈ρDM〉∝R−2eff provides the first clear indication of cuspy DM haloes in these galaxies – akin to standard Λ cold dark matter haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass ...


Is There Such A Thing As Quiet Sun?, Mark Peter Rast 2010 University of Colorado, Boulder

Is There Such A Thing As Quiet Sun?, Mark Peter Rast

Astrophysical & Planetary Sciences Faculty Contributions

The Cycle 23–Cycle 24 minimum was deep and prolonged, similar to minima of the late 19th and early 20th centuries but quite different from those between the overlapping cycles of the early space age. This provides a unique opportunity to study the Sun at very low levels of magnetic activity. Here we examine the quiet Sun, defining it to be those portions of the Sun for which continuum intensity variations are dominated by thermal perturbations as op- posed to opacity fluctuations due to the presence of magnetic fields. We briefly present evidence that: (1) The expected thermal signature of ...


Modeling The Solar Irradiance Background Via Numerical Simulation, B. Viticchié, M. Vantaggiato, F. Berrilli, D. del Moro, V. Penza, E. Pietropaolo, M. Rast 2010 Universitá degli Studi di Roma “Tor Vergata”

Modeling The Solar Irradiance Background Via Numerical Simulation, B. Viticchié, M. Vantaggiato, F. Berrilli, D. Del Moro, V. Penza, E. Pietropaolo, M. Rast

Astrophysical & Planetary Sciences Faculty Contributions

Various small scale photospheric processes are responsible for spatial and temporal variations of solar emer- gent intensity. The contribution to total irradiance fluctua- tions of such small scale features is the solar irradiance back- ground. Here we examine the statistical properties of irradi- ance background computed via a n-body numerical scheme mimicking photospheric space-time correlations and cal- ibrated by means of IBIS/DST spectro-polarimetric data. Such computed properties are compared with experimen- tal results derived from the analysis of a VIRGO/SPM data. A future application of the model here presented could be the interpretation of stellar irradiance power spectra ...


Computational Fluctuating Fluid Dynamics, Alejandro Garcia, J. B. Bell, S. Williams 2010 San Jose State University

Computational Fluctuating Fluid Dynamics, Alejandro Garcia, J. B. Bell, S. Williams

Faculty Publications

This paper describes the extension of a recently developed numerical solver for the Landau-Lifshitz Navier-Stokes (LLNS) equations to binary mixtures in three dimensions. The LLNS equations incorporate thermal fluctuations into macroscopic hydrodynamics by using white-noise fluxes. These stochastic PDEs are more complicated in three dimensions due to the tensorial form of the correlations for the stochastic fluxes and in mixtures due to couplings of energy and concentration fluxes (e.g., Soret effect). We present various numerical tests of systems in and out of equilibrium, including time-dependent systems, and demonstrate good agreement with theoretical results and molecular simulation


Origins Of The Extragalactic Background At 1mm From A Combined Analysis Of The Aztec And Mambo Data In Goods-N, Kyle Penner, Alexandra Pope, Edward L. Chapin, Thomas R. Greve, Frank Bertoldi, Mark Brodwin, Ranga-Ram Chary, Christopher J, Conselice, Kristen Coppin, Mauro Giavalisco, David H. Hughes, Rob J. Ivison, Thushara Perera, Douglas Scott, Kimberly Scott, Grant Wilson 2010 University of Massachusetts - Amherst

Origins Of The Extragalactic Background At 1mm From A Combined Analysis Of The Aztec And Mambo Data In Goods-N, Kyle Penner, Alexandra Pope, Edward L. Chapin, Thomas R. Greve, Frank Bertoldi, Mark Brodwin, Ranga-Ram Chary, Christopher J, Conselice, Kristen Coppin, Mauro Giavalisco, David H. Hughes, Rob J. Ivison, Thushara Perera, Douglas Scott, Kimberly Scott, Grant Wilson

Mauro Giavalisco

We present a study of the cosmic infrared background, which is a measure of the dust obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16mm map (sigma ~ 0.5mJy) by combining the AzTEC 1.1mm and MAMBO 1.2mm datasets in GOODS-N. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16mm flux densities of individually undetected galaxies with 24um flux densities > 25uJy ...


A Spectroscopic Search For Leaking Lyman Continuum At Z~0.7, Carrie R. Bridge, Harry I. Teplitz, Brian Siana, Claudia Scarlata, Christopher J. Conselice, Henry C. Ferguson, Thomas M. Brown, Mara Salvato, Gwen C. Rudie, Duilia F. de Mello, James Colbert, Jonathan P. Gardner, Mauro Giavalisco, Lee Armus 2010 University of Massachusetts - Amherst

A Spectroscopic Search For Leaking Lyman Continuum At Z~0.7, Carrie R. Bridge, Harry I. Teplitz, Brian Siana, Claudia Scarlata, Christopher J. Conselice, Henry C. Ferguson, Thomas M. Brown, Mara Salvato, Gwen C. Rudie, Duilia F. De Mello, James Colbert, Jonathan P. Gardner, Mauro Giavalisco, Lee Armus

Mauro Giavalisco

We present the results of rest-frame, UV slitless spectroscopic observations of a sample of 32 z~0.7 Lyman break galaxy (LBG) analogs in the COSMOS field. The spectroscopic search was performed with the Solar Blind Channel (SBC) on Hubble Space Telescope. We report the detection of leaking Lyman continuum (LyC) radiation from an AGN-starburst composite. While we find no direct detections of LyC emission in the remainder of our sample, we achieve individual lower limits (3 sigma) of the observed non-ionizing UV to LyC flux density ratios, f_{nu}(1500A)/f_{nu}(830A) of 20 to 204 (median of ...


Improving The Estimation Of Star Formation Rates And Stellar Population Ages Of High-Redshift Galaxies From Broadband Photometry, Seong-Kook Lee, Henry C. Ferguson, Rachel S. Somerville, Tommy Wiklind, Mauro Giavalisco 2010 University of Massachusetts - Amherst

Improving The Estimation Of Star Formation Rates And Stellar Population Ages Of High-Redshift Galaxies From Broadband Photometry, Seong-Kook Lee, Henry C. Ferguson, Rachel S. Somerville, Tommy Wiklind, Mauro Giavalisco

Mauro Giavalisco

We explore methods to improve the estimates of star formation rates and mean stellar population ages from broadband photometry of high redshift star-forming galaxies. We use synthetic spectral templates with a variety of simple parametric star formation histories to fit broadband spectral energy distributions. These parametric models are used to infer ages, star formation rates and stellar masses for a mock data set drawn from a hierarchical semi-analytic model of galaxy evolution. Traditional parametric models generally assume an exponentially declining rate of star-formation after an initial instantaneous rise. Our results show that star formation histories with a much more gradual ...


The Bright End Of The Z ~ 7 Uv Luminosity Function From A Wide And Deep Hawk-I Survey, M. Castellano, A. Fontana, D. Paris, A. Grazian, L. Pentericci, K. Boutsia, P. Santini, V. Testa, M. Dickinson, Mauro Giavalisco, R. Bouwens, J.-G. Cuby, F. Mannucci, B. Clément, S. Cristiani, F. Fiore, S. Gallozzi, E. Giallongo, R. Maiolino, N. Menci, A. Moorwood, N. Nonino, A. Renzini, P. Rosati, S. Salimbeni, E. Vanzella 2010 University of Massachusetts - Amherst

The Bright End Of The Z ~ 7 Uv Luminosity Function From A Wide And Deep Hawk-I Survey, M. Castellano, A. Fontana, D. Paris, A. Grazian, L. Pentericci, K. Boutsia, P. Santini, V. Testa, M. Dickinson, Mauro Giavalisco, R. Bouwens, J.-G. Cuby, F. Mannucci, B. Clément, S. Cristiani, F. Fiore, S. Gallozzi, E. Giallongo, R. Maiolino, N. Menci, A. Moorwood, N. Nonino, A. Renzini, P. Rosati, S. Salimbeni, E. Vanzella

Mauro Giavalisco

(Abridged) We present here the second half of an ESO Large Programme, which exploits the unique combination of area and sensitivity provided in the near-IR by the camera Hawk-I at the VLT. We have obtained - 30 observing hours with Hawk-I in the Y-band of two high galactic latitude fields. We combined the Y-band data with deep J and K Hawk-I observations, and with FORS1/FORS2 U, B, V, R, I, and Z observations to select z-drop galaxies having Z - Y > 1, no optical detection and flat Y - J and Y - K colour terms. We detect 8 high-quality candidates in the ...


The Hubble Space Telescope Goods Nicmos Survey: Overview And The Evolution Of Massive Galaxies At 1.5 < Z < 3, C. J. Conselice, A. F. L. Bluck, F. Buitrago, A. E. Bauer, R. Grützbauch, R. J. Bouwens, S. Bevan, A. Mortlock, M. Dickinson, E. Daddi, H. Yan, Douglas Scott, S. C. Chapman, R.-R. Chary, H. C. Ferguson, Mauro Giavalisco, N. Grogin, G. Illingworth, S. Jogee, A. M. Koekemoer, Ray A. Lucas, B. Mobasher, L. Moustakas, C. Papovich, S. Ravindranath, B. Siana, H. Teplitz, I. Trujillo, M. Urry, T. Weinzirl 2010 University of Massachusetts - Amherst

The Hubble Space Telescope Goods Nicmos Survey: Overview And The Evolution Of Massive Galaxies At 1.5 < Z < 3, C. J. Conselice, A. F. L. Bluck, F. Buitrago, A. E. Bauer, R. Grützbauch, R. J. Bouwens, S. Bevan, A. Mortlock, M. Dickinson, E. Daddi, H. Yan, Douglas Scott, S. C. Chapman, R.-R. Chary, H. C. Ferguson, Mauro Giavalisco, N. Grogin, G. Illingworth, S. Jogee, A. M. Koekemoer, Ray A. Lucas, B. Mobasher, L. Moustakas, C. Papovich, S. Ravindranath, B. Siana, H. Teplitz, I. Trujillo, M. Urry, T. Weinzirl

Mauro Giavalisco

We present the details and early results from a deep near-infrared survey utilising the NICMOS instrument on the Hubble Space Telescope centred around massive M_* > 10^11 M_0 galaxies at 1.7 < z < 2.9 found within the Great Observatories Origins Deep Survey (GOODS) fields. The GOODS NICMOS Survey (GNS) was designed to obtain deep F160W (H-band) imaging of 80 of these massive galaxies, as well as other colour selected objects such as Lyman-break drop-outs, BzK objects, Distant Red Galaxies, EROs, Spitzer Selected EROs, BX/BM galaxies, as well as sub-mm galaxies. We present in this paper details of the observations, our sample selection, as well as a description of features of the massive galaxies found within our survey fields. This includes: photometric redshifts, rest-frame colours, and stellar masses. We furthermore provide an analysis of the selection methods for finding massive galaxies at high redshifts, including colour selection, and how galaxy populations selected through different methods overlap. We find that a single colour selection method cannot locate all of the massive galaxies, with no one method finding more than 70 percent. We however find that the combination of these colour methods finds nearly all the massive galaxies, as selected by photometric redshifts with the exception of apparently rare blue massive galaxies. By investigating the rest-frame (U-B) vs. M_B diagram for these galaxies we furthermore show that there exists a bimodality in colour-magnitude space at z < 2, driven by stellar mass, such that the most massive galaxies are systematically red up to z~2.5, while lower mass galaxies tend to be blue. We also discuss the number densities for galaxies with stellar masses M_* > 10^11 M_0, whereby we find an increase of a factor of eight between z = 3 and z = 1.5, demonstrating that this is an epoch when massive galaxies establish most of their mass.


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