Astrophysics and Astronomy Commons^™

Dynamical Masses Of Early-Type Galaxies: A Comparison To Lensing Results And Implications For The Stellar Initial Mass Function And The Distribution Of Dark Matter, J. Thomas, R. P. Saglia, R. Bender, D. Thomas, K. Gebhardt, J. Magorrian, E. M. Corsini, G. Wegner, S. Seitz

Dartmouth Scholarship

This work aims to study the distribution of the luminous and dark matter in Coma early-type galaxies. Dynamical masses obtained under the assumption that mass follows light do not match with the masses of strong gravitational lens systems of similar velocity dispersions. Instead, dynamical fits with dark matter haloes are in good agreement with lensing results. We derive mass-to-light ratios of the stellar populations from Lick absorption line indices, reproducing well the observed galaxy colours. Even in dynamical models with dark matter haloes the amount of mass that follows the light increases more rapidly with the galaxy velocity dispersion than …

Analysis Of The 2008 Flare Of Markarian 421 Flare With Veritas, Casey Allard

Physics

A theoretical light curve model is fit to an observed short term flare of Markarian (Mrk) 421 in the very high energy spectrum. The flare is characterized by its measured light curve from the Very Energetic Radiation Imaging telescope Array System (VERITAS). The flare we analyzed occurred in May 2008. We successfully fit a theoretical model to the Mrk 421 data light curve. The data appears to agree with the Wagner [1] and Salvati [2] models. These models appear to fit both broad and sharp flaring regions found in the measured light curve. Furthermore the Wagner model is used to …

The Double Galaxy Cluster Abell 2465 - I. Basic Properties: Optical Imaging And Spectroscopy, Gary A. Wegner

Dartmouth Scholarship

Optical imaging and spectroscopic observations of the z= 0.245 double galaxy cluster Abell 2465 are described. This object appears to be undergoing a major merger. It is a double X-ray source and is detected in the radio at 1.4 GHz. The purpose of this paper is to investigate signatures of the interaction of the two components. Redshifts were measured to determine velocity dispersions and virial radii of each component. The technique of fuzzy clustering was used to assign membership weights to the galaxies in each clump. Using redshifts of 93 cluster members within 1.4 Mpc of the subcluster centres, …

Oral Presentation: The Universe In A Box, Jason Jaacks

Festival of Communities: UG Symposium (Posters)

When and how galaxies formed throughout the history of the Universe is one of the most fundamental questions of astronomy and astrophysics. As technology improves, astronomers are able to push the frontier of galaxy observation to a period when the Universe was less than 1 billion years old. This is when the first galaxies are beginning to form. However, beyond the limits of observational technology lies data fundamental to our complete understanding of these processes. Using state-of-the-art cosmological hydrodynamic computer codes combined with access to the nation’s largest and fastest supercomputers, we are able to simulate the formation and evolution …

Halo Occupation Of Lyman-Break Galaxies, Saju Varghese, Ken Nagamine, Jason Jaacks, Jun-Hwan Choi

Festival of Communities: UG Symposium (Posters)

Lyman-break galaxies (LBGs) are star-forming galaxies found at high redshift that provide large amounts of information on early star and galaxy formation. We use large-scale cosmological smoothed-particle hydrodynamical simulations to simulate the physical properties of LBGs, such as stellar mass, star-formation rate, and magnitude. In particular, we focus on the question of which dark matter (DM) halos host LBGs. Our simulation suggests that only 1.74% of all DM halos host LBGs, though among the massive DM halos with mass Mhalo >1011.5 Msun, the fraction is 51.93%. The occupation number of LBGs ranges from 1 to 17 per halo.

The Efficacy Of Galaxy Shape Parameters In Photometric Redshift Estimation: A Neural Network Approach, Jack Singal, M. Shmakova, B. Gerke, R. L. Griffith, J. Lotz

Physics Faculty Publications

We present a determination of the effects of including galaxy morphological parameters in photometric redshift estimation with an artificial neural network method. Neural networks, which recognize patterns in the information content of data in an unbiased way, can be a useful estimator of the additional information contained in extra parameters, such as those describing morphology, if the input data are treated on an equal footing. We use imaging and five band photometric magnitudes from the All-wavelength Extended Groth Strip International Survey. It is shown that certain principal components of the morphology information are correlated with galaxy type. However, we find …

The Arcade 2 Instrument, Jack Singal, D. J. Fixsen, A. Kogut, S. Levin, M. Limon, P. Lubin, P. Mirel, M. Seiffert, T. Villela, E. Wollack, C. A. Wuensche

Physics Faculty Publications

The second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) instrument is a balloon-borne experiment to measure the radiometric temperature of the cosmic microwave background and Galactic and extragalactic emission at six frequencies from 3 to 90 GHz. ARCADE 2 utilizes a double-nulled design where emission from the sky is compared to that from an external cryogenic full-aperture blackbody calibrator by cryogenic switching radiometers containing internal blackbody reference loads. In order to further minimize sources of systematic error, ARCADE 2 features a cold fully open aperture with all radiometrically active components maintained at near 2.7 K without …

Discovery Of Tev Gamma Ray Emission From Tycho's Supernova Remnant, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the discovery of TeV gamma-ray emission from the Type Ia supernova remnant (SNR) G120.1+1.4, known as Tycho's SNR. Observations performed in the period 2008-2010 with the VERITAS ground-based gamma-ray observatory reveal weak emission coming from the direction of the remnant, compatible with a point source located at 00h25m270, + 64°10'50'' (J2000). The TeV photon spectrum measured by VERITAS can be described with a power law dN/dE = C(E/3.42 TeV)–Γ with Γ = 1.95 ± 0.51stat ± 0.30sys and C = (1.55 ± 0.43stat ± 0.47sys) × 10–14 cm–2 s–1 TeV–1. The integral …

A Distinctive Disk-Jet Coupling In The Seyfert-1 Active Galactic Nucleus Ngc 4051, A. L. King, J. M. Miller, E. M. Cackett, A. C. Fabian, S. Markoff, M. A. Nowak, M. Rupen, K. Gültekin, M. T. Reynolds

Physics and Astronomy Faculty Research Publications

We report on the results of a simultaneous monitoring campaign employing eight Chandra X-ray (0.5-10 keV) and six Very Large Array/Extended Very Large Array (8.4 GHz) radio observations of NGC 4051 over seven months. Evidence for compact jets is observed in the 8.4 GHz radio band; this builds on mounting evidence that jet production may be prevalent even in radio-quiet Seyferts. Assuming comparatively negligible local diffuse emission in the nucleus, the results also demonstrate an inverse correlation of L _radio ∝ L ^-0.72±0.04 _X-ray . If the A configuration is excluded in the case where diffuse emission plays a significant …

Sources Of The Radio Background Considered, Jack Singal, L. Stawarz, A. Lawrence, V. Petrosian

Physics Faculty Publications

We investigate different scenarios for the origin of the extragalactic radio background. The surface brightness of the background, as reported by the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission 2 (ARCADE 2) collaboration, is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low-surface-brightness regions of radio sources and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio …

Discovery Of Very High Energy Gamma-Ray Emission From The Snr G54.1+0.3, P. T. Reynolds, Et Al

Physical Sciences Publications

We report the discovery of very high energy (VHE) gamma-ray emission from the direction of the SNR G54.1+0.3 using the VERITAS ground-based gamma-ray observatory. The TeV signal has an overall significance of 6.8σ and appears pointlike given the resolution of the instrument. The integral flux above 1 TeV is 2.5% of the Crab Nebula flux and significant emission is measured between 250 GeV and 4 TeV, well described by a power-law energy spectrum dN/dE ~ E –Γ with a photon index Γ = 2.39 ± 0.23stat ± 0.30sys. We find no evidence of time variability among observations …

Colours Of Bulges And Discs Within Galaxy Clusters And The Signature Of Disc Fading On Infall, Michael J. Hudson, Jeffrey B. Stevenson, Russell J. Smith, Gary A. Wegner

Dartmouth Scholarship

The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z < 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L_* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio …

Stirring Up The Pot: Can Cooling Flows In Galaxy Clusters Be Quenched By Gas Sloshing?, J. A. A. Zuhone, M. Markevitch, R. E. Johnson

Dartmouth Scholarship

X-ray observations of clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts." In relaxed clusters with cool cores, these commonly observed edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. Such sloshing may provide a source of heat to the cluster core by mixing hot gas from the cluster outskirts with the cool-core gas. Using high-resolution N-body/Eulerian hydrodynamic simulations, we model gas sloshing in galaxy clusters initiated by mergers with subclusters. The simulations include merger scenarios with gas-filled and gasless subclusters. The …

The Discovery Of Gamma-Ray Emission From The Blazar Rgb J0710+591, P. T. Reynolds, Et Al

Physical Sciences Publications

The high-frequency-peaked BL Lacertae object RGB J0710+591 was observed in the very high-energy (VHE; E > 100 GeV) wave band by the VERITAS array of atmospheric Cherenkov telescopes. The observations, taken between 2008 December and 2009 March and totaling 22.1 hr, yield the discovery of VHE gamma rays from the source. RGB J0710+591 is detected at a statistical significance of 5.5 standard deviations (5.5σ) above the background, corresponding to an integral flux of (3.9 ± 0.8) × 10–12 cm–2 s–1 (3% of the Crab Nebula's flux) above 300 GeV. The observed spectrum can be fit by a power law from 0.31 …

Dla-Lbg Cross-Correlation And Basic Properties Of Infrared Galaxies In Cosmological Simulations, Tae Song Lee

UNLV Theses, Dissertations, Professional Papers, and Capstones

PART I

We calculate the cross-correlation function (CCF) between damped Ly-alpha systems (DLAs) and Lyman break galaxies (LBGs) using cosmological hydrodynamic simulations at z = 3. We compute the CCF with two different methods. First, we assume that there is one DLA in each dark matter halo if its DLA cross section is non-zero. In our second approach we weight the pair-count by the DLA cross section of each halo, yielding a cross-section-weighted CCF. We also compute the angular CCF for direct comparison with observations. Finally, we calculate the auto-correlation functions of LBGs and DLAs, and their bias against the …

Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman

Dartmouth Scholarship

We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M ₅₀₀ = (2.6 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the northern sub-cluster and M ₅₀₀ = (3.1 ± 0.4) × 10¹⁴ h ^–1 M _☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …

Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al

Physical Sciences Publications

We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured …

Begin The Adventure : How To Break The Light Barrier By A.D. 2079 (3rd Ed.), Florentin Smarandache, Homer B. Tilton

Branch Mathematics and Statistics Faculty and Staff Publications

This edition, the third, has undergone a subtle name change, going from "A.D. 2070" in the title to A.D. 2079 as the timeline is fine-tuned. Because of the almost universal failure to recognize the distinction between physical (reality-based, dynamical) and visual (appearance-based, kinematical) variables, a tremendous volume of mythology arose over the past 100 years centered around Einstein's reality view of the distortions of special relativity. To get a sense of it, we point the reader to Paul J. Nahin's heroic book, Time Machines, 2nd ed.,- to these Tech Notes in particular: TN#6. "A High-Speed Rocket Is a One-Way Time …

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. …

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 ± …

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 …