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Astrophysics and Astronomy

Aerospace, Physics, and Space Science Faculty Publications

2014

Articles 1 - 20 of 20

Full-Text Articles in Physical Sciences and Mathematics

Recoiling Supermassive Black Holes: A Search In The Nearby Universe, Davide Lena, Andrew Edward Robinson, Alessandro Marconi, David J. Axon, Alessandro Capetti, David Merritt, Daniel P. Batcheldor Nov 2014

Recoiling Supermassive Black Holes: A Search In The Nearby Universe, Davide Lena, Andrew Edward Robinson, Alessandro Marconi, David J. Axon, Alessandro Capetti, David Merritt, Daniel P. Batcheldor

Aerospace, Physics, and Space Science Faculty Publications

The coalescence of a binary black hole can be accompanied by a large gravitational recoil due to anisotropic emission of gravitational waves. A recoiling supermassive black hole (SBH) can subsequently undergo long-lived oscillations in the potential well of its host galaxy, suggesting that offset SBHs may be common in the cores of massive ellipticals. We have analyzed Hubble Space Telescope archival images of 14 nearby core ellipticals, finding evidence for small (≲ 10 pc) displacements between the active galactic nucleus (AGN; the location of the SBH) and the center of the galaxy (the mean photocenter) in 10 of them. Excluding …

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X-Ray Emission From Magnetic Massive Stars, Yaël Nazé, Véronique Petit, Melanie Rinbrand, David H. Cohen, Stanley P. Owocki, Asif Ud-Doula, Gregg A. Wade Nov 2014

X-Ray Emission From Magnetic Massive Stars, Yaël Nazé, Véronique Petit, Melanie Rinbrand, David H. Cohen, Stanley P. Owocki, Asif Ud-Doula, Gregg A. Wade

Aerospace, Physics, and Space Science Faculty Publications

Magnetically confined winds of early-type stars are expected to be sources of bright and hard X-rays. To clarify the systematics of the observed X-ray properties, we have analyzed a large series of Chandra and XMM-Newton observations, corresponding to all available exposures of known massive magnetic stars (over 100 exposures covering 60% of stars compiled in the catalog of Petit et al.). We show that the X-ray luminosity is strongly correlated with the stellar wind mass-loss rate, with a power-law form that is slightly steeper than linear for the majority of the less luminous, lower- B stars and flattens for the …

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Polarized Mid-Infrared Synchrotron Emission In The Core Of Cygnus A, Enrique López Rodríguez, Eric S. Perlman Oct 2014

Polarized Mid-Infrared Synchrotron Emission In The Core Of Cygnus A, Enrique López Rodríguez, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

We present high-angular (∼0". 4) resolution mid-infrared (MIR) polarimetric observations in the 8.7μm and 11.6μm filters of Cygnus A using CanariCam on the 10.4 m Gran Telescopio CANARIAS. A highly polarized nucleus is observed with a degree of polarization of 11% ±3% and 12% ±3% and a position angle of polarization of 27◦ ±8◦ and 35◦ ± 8◦ in a 0.".38 (∼380 pc) aperture for each filter. The observed rising of the polarized flux density with increasing wavelength is consistent with synchrotron radiation from the parsec-scale jet close to the core of Cygnus A. Based on our polarization model, the …

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Model Of Electromagnetic Ion Cyclotron Waves In The Inner Magnetosphere, K. V. Gamayunov, M. J. Engebretson, M. Zhang, H. K. Rassoul Sep 2014

Model Of Electromagnetic Ion Cyclotron Waves In The Inner Magnetosphere, K. V. Gamayunov, M. J. Engebretson, M. Zhang, H. K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

he evolution of He+-mode electromagnetic ion cyclotron (EMIC) waves is studied inside the geostationary orbit using our global model of ring current (RC) ions, electric field, plasmasphere, and EMIC waves. In contrast to the approach previously used by Gamayunov et al. (2009), however, we do not use the bounce-averaged wave kinetic equation but instead use a complete, nonbounce-averaged, equation to model the evolution of EMIC wave power spectral density, including off-equatorial wave dynamics. The major results of our study can be summarized as follows. (1) The thermal background level for EMIC waves is too low to allow waves to grow …

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Heliospheric Influence On The Anisotropy Of Tev Cosmic Rays, Ming Zhang, Pingbing Zuo, Nikolai Pogorelov Jul 2014

Heliospheric Influence On The Anisotropy Of Tev Cosmic Rays, Ming Zhang, Pingbing Zuo, Nikolai Pogorelov

Aerospace, Physics, and Space Science Faculty Publications

This paper provides a theory of using Liouville's theorem to map the anisotropy of TeV cosmic rays seen at Earth using the particle distribution function in the local interstellar medium (LISM). The ultimate source of cosmic ray anisotropy is the energy, pitch angle, and spatial dependence of the cosmic ray distribution function in the LISM. Because young nearby cosmic ray sources can make a special contribution to the cosmic ray anisotropy, the anisotropy depends on the source age, distance and magnetic connection, and particle diffusion of these cosmic rays, all of which make the anisotropy sensitive to the particle energy. …

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A Numerical Simulation Of Solar Energetic Particle Dropouts During Impulsive Events, Yi Wáng, Gang Qin, Ming Zhang, Silvia Dalla Jul 2014

A Numerical Simulation Of Solar Energetic Particle Dropouts During Impulsive Events, Yi Wáng, Gang Qin, Ming Zhang, Silvia Dalla

Aerospace, Physics, and Space Science Faculty Publications

This paper investigates the conditions for producing rapid variations of solar energetic particle (SEP) intensity commonly known as "dropouts." In particular, we use numerical model simulations based on solving the focused transport equation in the three-dimensional Parker interplanetary magnetic field to put constraints on the properties of particle transport coefficients in both directions perpendicular and parallel to the magnetic field. Our calculations of the temporal intensity profile of 0.5 and 5 MeV protons at the Earth show that the perpendicular diffusion must be small while the parallel mean free path is long in order to reproduce the phenomenon of SEP …

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Morphology And Environment Of Galaxies With Disc Breaks In The S4g And Nirs0s, J. Laine, E. Laurikainen, H. Salo, S. Comeron, R. J. Buta, D. Zaritsky, E. Athanassoula, A. Bosma, J.-C. Munoz-Mateos, D. A. Gadotti, J. L. Hinz, S. Erroz-Ferrer, A. Gil De Paz, T. Kim, K. Menendez-Delmestre, T. Mizusawa, M. W. Regan, M. Seibert, K. Sheth Jul 2014

Morphology And Environment Of Galaxies With Disc Breaks In The S4g And Nirs0s, J. Laine, E. Laurikainen, H. Salo, S. Comeron, R. J. Buta, D. Zaritsky, E. Athanassoula, A. Bosma, J.-C. Munoz-Mateos, D. A. Gadotti, J. L. Hinz, S. Erroz-Ferrer, A. Gil De Paz, T. Kim, K. Menendez-Delmestre, T. Mizusawa, M. W. Regan, M. Seibert, K. Sheth

Aerospace, Physics, and Space Science Faculty Publications

We study the surface brightness profiles of disc galaxies in the 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies (S4G) and Ks-band images from the Near-Infrared S0-Sa galaxy Survey (NIRS0S). We particularly connect properties of single exponential (type I), downbending double exponential (type II), and upbending double exponential (type III) disc profile types, to structural components of galaxies by using detailed morphological classifications, and size measurements of rings and lenses. We also study how the local environment of the galaxies affects the profile types by calculating parameters describing the environmental density and the tidal …

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Reconstructing The Stellar Mass Distributions Of Galaxies Using S4g Irac 3.6 And 4.5 Μm Images. Ii. The Conversion From Light To Mass, Sharon E. Meidt, Trisha F. Mizusawa Jun 2014

Reconstructing The Stellar Mass Distributions Of Galaxies Using S4g Irac 3.6 And 4.5 Μm Images. Ii. The Conversion From Light To Mass, Sharon E. Meidt, Trisha F. Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

We present a new approach for estimating the 3.6 μm stellar mass-to- light (M/L) ratio Υ3.6 in terms of the [3.6]-[4.5] colors of old stellar populations. Our approach avoids several of the largest sources of uncertainty in existing techniques using population synthesis models. By focusing on mid-IR wavelengths, we gain a virtually dust extinction-free tracer of the old stars, avoiding the need to adopt a dust model to correctly interpret optical or optical/near-IR colors normally leveraged to assign the mass-to-light ratio Υ. By calibrating a new relation between near-IR and mid-IR colors of giant stars observed in GLIMPSE we also …

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Subaru Spectroscopy And Spectral Modeling Of Cygnus A, Matthew J. Merlo, Eric S. Perlman, Robert Nikutta, Christopher Packham, Moshe Elitzur, Masatoshi Imanishi, Nancy A. Levenson, James T. Radomski, Itziar Aretxaga Jun 2014

Subaru Spectroscopy And Spectral Modeling Of Cygnus A, Matthew J. Merlo, Eric S. Perlman, Robert Nikutta, Christopher Packham, Moshe Elitzur, Masatoshi Imanishi, Nancy A. Levenson, James T. Radomski, Itziar Aretxaga

Aerospace, Physics, and Space Science Faculty Publications

We present high angular resolution (∼0.″5) MIR spectra of the powerful radio galaxy, Cygnus A (Cyg A), obtained with the Subaru telescope. The overall shape of the spectra agree with previous high angular resolution MIR observations, as well as previous Spitzer spectra. Our spectra, both on and off nucleus, show a deep silicate absorption feature. The absorption feature can be modeled with a blackbody obscured by cold dust or a clumpy torus. The deep silicate feature is best fit by a simple model of a screened blackbody, suggesting that foreground absorption plays a significant, if not dominant, role in shaping …

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The Baryonic Tully-Fisher Relationship For S4g Galaxies And The "Condensed" Baryon Fraction Of Galaxies, Dennis Zaritsky, Trisha F. Mizusawa Jun 2014

The Baryonic Tully-Fisher Relationship For S4g Galaxies And The "Condensed" Baryon Fraction Of Galaxies, Dennis Zaritsky, Trisha F. Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of H I spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which …

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The White Dwarfs Within 25 Pc Of The Sun: Kinematics And Spectroscopic Subtypes, Edward M. Sion, Jay B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic, Janine Myszka Jun 2014

The White Dwarfs Within 25 Pc Of The Sun: Kinematics And Spectroscopic Subtypes, Edward M. Sion, Jay B. Holberg, Terry D. Oswalt, George P. Mccook, Richard Wasatonic, Janine Myszka

Aerospace, Physics, and Space Science Faculty Publications

We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is …

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Unveiling The Structure Of Barred Galaxies At 3.6 Μm With The Spitzer Survey Of Stellar Structure In Galaxies (S4g). I. Disk Breaks, Taehyun Kim, Trisha Mizusawa Feb 2014

Unveiling The Structure Of Barred Galaxies At 3.6 Μm With The Spitzer Survey Of Stellar Structure In Galaxies (S4g). I. Disk Breaks, Taehyun Kim, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

We have performed two-dimensional multicomponent decomposition of 144 local barred spiral galaxies using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Our model fit includes up to four components (bulge, disk, bar, and a point source) and, most importantly, takes into account disk breaks. We find that ignoring the disk break and using a single disk scale length in the model fit for Type II (down-bending) disk galaxies can lead to differences of 40% in the disk scale length, 10% in bulge-to-total luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that for galaxies …

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Planetary Candidates Observed By Kepler Iv: Planet Sample From Q1-Q8 (22 Months), Christopher J. Burke, Darin Ragozzine Feb 2014

Planetary Candidates Observed By Kepler Iv: Planet Sample From Q1-Q8 (22 Months), Christopher J. Burke, Darin Ragozzine

Aerospace, Physics, and Space Science Faculty Publications

We provide updates to the Kepler planet candidate sample based upon nearly two years of high-precision photometry (i.e., Q1-Q8). From an initial list of nearly 13,400 threshold crossing events, 480 new host stars are identified from their flux time series as consistent with hosting transiting planets. Potential transit signals are subjected to further analysis using the pixel-level data, which allows background eclipsing binaries to be identified through small image position shifts during transit. We also re-evaluate Kepler Objects of Interest (KOIs) 1-1609, which were identified early in the mission, using substantially more data to test for background false positives and …

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Extended Warm Gas In The Ulirg Mrk273: Galactic Outflows And Tidal Debris, Javier Rodríguez Zaurín, Clive N. Tadhunter, David S.N. Rupke, Sylvain Veilleux, Henrik W.W. Spoon, Marco Chiaberge, Cristina Ramos Almeida, Dan Batcheldor, William B. Sparks Jan 2014

Extended Warm Gas In The Ulirg Mrk273: Galactic Outflows And Tidal Debris, Javier Rodríguez Zaurín, Clive N. Tadhunter, David S.N. Rupke, Sylvain Veilleux, Henrik W.W. Spoon, Marco Chiaberge, Cristina Ramos Almeida, Dan Batcheldor, William B. Sparks

Aerospace, Physics, and Space Science Faculty Publications

We present new HST/ACS medium-and narrow-band images and optical Isaac Newton Telescope long-slit spectra of the merging system Mrk273. The HST observations sample the [OIII]λλ4959,5007 emission from the galaxy and the nearby continuum. These data were taken as a part of a larger study of ultraluminous infrared galaxies (ULIRGs) with the aim of investigating the importance of the warm, AGN induced outflows in such objects. The HST images show that the morphologies of the extended continuum and the ionised gas emission from the galaxy are decoupled, extending almost perpendicular to each other. In particular, we detect for the first time …

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Emission Lines Properties Of The Radio-Loud Quasar Lamost J1131+3114, Zhixin Shi, Georges Comte, Ali L. Luo, Tuehong H. Zhao, Jingkun K. Zhao, T D. Oswalt, Fuchao C. Wu Jan 2014

Emission Lines Properties Of The Radio-Loud Quasar Lamost J1131+3114, Zhixin Shi, Georges Comte, Ali L. Luo, Tuehong H. Zhao, Jingkun K. Zhao, T D. Oswalt, Fuchao C. Wu

Aerospace, Physics, and Space Science Faculty Publications

The radio-loud quasar LAMOST J1131+3114 (Ton 580, B2 1128+315), showing asymmetrical profile in Hβ and [O III] lines, has been selected from the LAMOST Pilot Survey for further study. We present an analysis of its emission lines by means of multiple Gaussian fitting, performed on LAMOST, Apache Point Observatory, and archival spectra. The broad line region, with an Hβ line of FWHM ~ 4000 km sˉ¹ has been fit with a double Gaussian, one of which is very broad and redshifted from the reference frame. The object is a likely Population B quasar. The [O III] λλ4959,5007 lines profiles of …

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Embedded Star Formation In S4g Galaxy Dust Lanes, Debra M. Elmegreen, Trisha Mizusawa Jan 2014

Embedded Star Formation In S4g Galaxy Dust Lanes, Debra M. Elmegreen, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

Star-forming regions that are visible at 3.6 μm and Hα but not in the u, g, r, i, z bands of the Sloan Digital Sky Survey are measured in five nearby spiral galaxies to find extinctions averaging ∼3.8 mag and stellar masses averaging ∼5 × 104 M ⊙. These regions are apparently young star complexes embedded in dark filamentary shock fronts connected with spiral arms. The associated cloud masses are ∼10 7 M ⊙. The conditions required to make such complexes are explored, including gravitational instabilities in spiral-shocked gas and compression of incident clouds. We find that instabilities are too …

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Numerical Simulations Of Compact Intracloud Discharges As The Relativistic Runaway Electron Avalanche-Extensive Air Shower Process, Shahab Arabshahi, Joseph R. Dwyer, A. Nag, V. A. Rakov, Hamid K. Rassoul Jan 2014

Numerical Simulations Of Compact Intracloud Discharges As The Relativistic Runaway Electron Avalanche-Extensive Air Shower Process, Shahab Arabshahi, Joseph R. Dwyer, A. Nag, V. A. Rakov, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Compact intracloud discharges (CIDs) are sources of the powerful, often isolated radio pulses emitted by thunderstorms. The VLF-LF radio pulses are called narrow bipolar pulses (NBPs). It is still not clear how CIDs are produced, but two categories of theoretical models that have previously been considered are the Transmission Line (TL) model and the Relativistic Runaway Electron Avalanche-Extensive Air Showers (RREA-EAS) model. In this paper, we perform numerical calculations of RREA-EASs for various electric field configurations inside thunderstorms. The results of these calculations are compared to results from the other models and to the experimental data. Our analysis shows that …

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Modulated X-Ray Emission Of The Magnetic O8.5v-Star Tr16-22, Yaël Nazé, Gregg A. Wade, Véronique Petit Jan 2014

Modulated X-Ray Emission Of The Magnetic O8.5v-Star Tr16-22, Yaël Nazé, Gregg A. Wade, Véronique Petit

Aerospace, Physics, and Space Science Faculty Publications

Using an extensive X-ray dataset, we analyzed the X-ray emission of the massive O-star Tr16-22, which was recently found to be magnetic. Its bright X-ray emission is found to be modulated with a 54d period. This timescale should represent the rotational timescale of the star, as it does for other magnetic massive stars. In parallel, new spectropolarimetric data confirm the published magnetic detection.

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Arrakis: Atlas Of Resonance Rings As Known In The S⁴G, Sébastien Comerón, Trisha Mizusawa Jan 2014

Arrakis: Atlas Of Resonance Rings As Known In The S⁴G, Sébastien Comerón, Trisha Mizusawa

Aerospace, Physics, and Space Science Faculty Publications

Context. Resonance rings and pseudorings (here collectively called rings) are thought to be related to the gathering of material near dynamical resonances caused by non-axisymmetries in galaxy discs. This means that they are the result of secular evolution processes that redistribute material and angular momentum in discs. Studying them may give clues on the formation and growth of bars and other disc non-axisymmetries. Aims. Our aims are to produce a catalogue and an atlas of the rings detected in the Spitzer Survey of Stellar Structure in Galaxies (S⁴G) and to conduct a statistical study of the data in the catalogue. …

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An Analytical Approach For Calculating Energy Spectra Of Relativistic Runaway Electron Avalanches In Air, Eric S. Crame, Joseph R. Dwyer, Shahab Arabshahi, Igor B. Vodopiyanov, Ningyu Liu, Hamid K. Rassoul Jan 2014

An Analytical Approach For Calculating Energy Spectra Of Relativistic Runaway Electron Avalanches In Air, Eric S. Crame, Joseph R. Dwyer, Shahab Arabshahi, Igor B. Vodopiyanov, Ningyu Liu, Hamid K. Rassoul

Aerospace, Physics, and Space Science Faculty Publications

Simplified equations describing the transport and energy spectrum of runaway electrons are derived from the basic kinematics of the continuity equations. These equations are useful in modeling the energy distribution of energetic electrons in strong electric fields, such as those found inside thunderstorms. Dwyer and Babich (2011) investigated the generation of low-energy electrons in relativistic runaway electron avalanches. The paper also developed simple analytical expressions to describe the detailed physics of Monte Carlo simulations of relativistic runaway electrons in air. In the current work, the energy spectra of the runaway electron population are studied in detail. Dependence of electron avalanche …

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