Astrophysics and Astronomy Commons^™

Discovery Of Very High Energy Gamma Rays From Pks 1424+240 And Multiwavelength Constraints On Its Redshift, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the first detection of very high energy83Gamma-ray emission above 100 GeV. (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140 GeV measured by VERITAS is well described by a power law with a photon index of 3.8 ± 0.5stat ± 0.3syst and a flux normalization at 200 GeV of (5.1 ± 0.9stat ± 0.5syst) × 10–11 TeV–1 cm–2 s–1, where stat and syst denote the statistical and systematical uncertainties, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (from …

The Acs Survey Of Galactic Globular Clusters. Ix. Horizontal Branch Morphology And The Second Parameter Phenomenon, Aaron Dotter, Ata Sarajedini, Jay Anderson, Antonio Aparicio, Luigi R. Bedin, Brian Chaboyer

Dartmouth Scholarship

The horizontal branch (HB) morphology of globular clusters (GCs) is most strongly influenced by metallicity. The second parameter phenomenon, first described in the 1960s, acknowledges that metallicity alone is not enough to describe the HB morphology of all GCs. In particular, astronomers noticed that the outer Galactic halo contains GCs with redder HBs at a given metallicity than are found inside the solar circle. Thus, at least a second parameter was required to characterize HB morphology. While the term "second parameter" has since come to be used in a broader context, its identity with respect to the original problem has …

On Neutral Absorption And Spectral Evolution In X-Ray Binaries, J. M. Miller, E. M. Cackett, R. C. Reis

Physics and Astronomy Faculty Research Publications

Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual …

The Fundamental Plane Of Accretion Onto Black Holes With Dynamical Masses, Kayhan Gültekin, Edward M. Cackett, Jon M. Miller, Tiziana Di Matteo, Sera Markoff, Douglas O. Richstone

Physics and Astronomy Faculty Research Publications

Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively …

A Spectroscopically Confirmed Excess Of 24 Μm Sources In A Super Galaxy Group At Z=0.37: Enhanced Dusty Star Formation Relative To The Cluster And Field Environment, Kim-Vy H. Tran, Amelie Saintonge, John Moustakas, Lei Bai, Anthony H. Gonzalez, Bradford P. Holden, Dennis Zaritsky, Stefan Kautsch

Chemistry and Physics Faculty Articles

To trace how dust-obscured star formation varies with environment, we compare the fraction of 24 μm sources in a super galaxy group to the field and a rich galaxy cluster at z ~ 0.35. We draw on multi-wavelength observations that combine Hubble, Chandra, and Spitzer imaging with extensive optical spectroscopy (>1800 redshifts) to isolate galaxies in each environment and thus ensure a uniform analysis. We focus on the four galaxy groups (σ_1D = 303-580 km s^–1) in supergroup 1120-12 that will merge to form a galaxy cluster comparable in mass to Coma. We find …

Constraining The Spin Of The Black Hole In Fairall 9 With Suzaku, S. Schmoll, J. M. Miller, M. Volonteri, E. Cackett, C. S. Reynolds, A. C. Fabian, L. W. Brenneman, G. Miniutti, L. C. Gallo

Physics and Astronomy Faculty Research Publications

We report on the results of spectral fits made to data obtained from a 168 ks Suzaku observation of the Seyfert 1 galaxy Fairall 9. The source is clearly detected out to 30 keV. The observed spectrum is fairly simple; it is well described by a power law with soft excess and disk reflection. A broad iron line is detected, and easily separated from distinct narrow components owing to the resolution of the CCDs in the X-ray Imaging Spectrometer (XIS). The broad line is revealed to be asymmetric, consistent with a disk origin. We fit the XIS and Hard X-ray …

Detection Of Extended Vhe Gamma Ray Emission From G106.3+2.7 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3σ (pre-trials) detection has a full angular extent of roughly 06 by 04. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 04 away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. …

Radial Distribution Of Stars, Gas, And Dust In Sings Galaxies. Ii. Derived Dust Properties, J.C. Munoz-Mateo, A. Gil De Paz, S. Boissier, J. Zamorano, D.A. Dale, P.G. Perez-Gonzalez, Michele D. Thornley

Michele Thornley

Observation Of Extended Very High Energy Emission From The Supernova Remnant Ic 443 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hr during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (σ) before trials and 7.5σ after trials in a point-source search. The emission is centered at 6h16m51s + …

Long-Term Optical And X-Ray Variability Of The Seyfert Galaxy Markarian 79, E. Breedt, P. Arévalo, I. M. Mchardy, P. Uttley, S. G. Sergeev, T. Minezaki, Y. Yoshii, C. M. Gaskell, E. M. Cackett, K. Horne, S. Koshida

Physics and Astronomy Faculty Research Publications

We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than 5yr. We find that on short to medium time-scales (days to a few tens of days) the 2-10 keV X-ray and optical u- and V-band fluxes are significantly correlated, with a delay between the bands consistent with 0d. We show that most of these variations may be well reproduced by a model where the short-term optical variations originate from reprocessing of X-rays by an optically thick accretion disc. The optical light curves, however, also display long time-scale …

Neutrosophic Logic, Wave Mechanics, And Other Stories: Selected Works 2005-2008, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

There is beginning for anything; we used to hear that phrase. The same wisdom word applies to us too. What began in 2005 as a short email on some ideas related to interpretation of the Wave Mechanics results in a number of papers and books up to now. Some of these papers can be found in Progress in Physics or elsewhere. It is often recognized that when a mathematician meets a physics-inclined mind then the result is either a series of endless debates or publication. In our story, we prefer to publish rather than perish. Therefore, our purpose with this …

Veritas Observations Of A Very High Energy Gamma-Ray Flare From The Blazar 3c 66a, P. T. Reynolds, Et Al

Physical Sciences Publications

The intermediate-frequency peaked BL Lacertae (IBL) object 3C 66A is detected during 2007-2008 in VHE (very high energy; E > 100 GeV) γ rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events is detected, corresponding to a significance of 21.2 standard deviations (σ), in these observations (32.8 hr live time). The observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows evidence for variability on the timescale of days. The measured energy spectrum is characterized by a soft power law with photon index Γ = 4.1 ± 0.4stat ± …

The Role Of Stellar Feedback In Galaxy Evolution, Li Zhiyuan

Open Access Dissertations

Aiming at understanding the role of stellar feedback in galaxy evolution, I present a study of the hot interstellar medium in several representative galaxies, based primarily on X-ray observations as well as theoretical modelling. I find that, in the massive disk galaxies NGC2613 and M104, the observed amount of hot gas is much less than that predicted by current galaxy formation models. Such a discrepancy suggests a lack of appropriate treatments of stellar/AGN feedback in these models. I also find that stellar feedback, primarily in the form of mass loss from evolved stars and energy released from supernovae, and presumably …

Dark Matter Scaling Relations And The Assembly Epoch Of Coma Early-Type Galaxies, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J Magorrian, E. M. Corsini, G. Wegner

Dartmouth Scholarship

Axisymmetric, orbit-based dynamical models are used to derive dark matter scaling relations for Coma early-type galaxies. From faint to bright galaxies, halo core radii and asymptotic circular velocities increase. Compared to spirals of the same brightness, the majority of Coma early-type galaxies—those with old stellar populations—have similar halo core radii but more than two times larger asymptotic halo velocities. The average dark matter density inside 2 r _eff decreases with increasing luminosity and is 6.8 times larger than in disk galaxies of the same B-band luminosity. Compared at the same stellar mass, dark matter densities in ellipticals are 13.5 …

New Eclipsing Close Binary Star In The Constellation Of Sextants, Jeff W. Robertson

Journal of the Arkansas Academy of Science

No abstract provided.