External Galaxies Commons^™

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 …