Search Publications
Can a supervoid explain the cold spot?
Nadathur, Seshadri; Räsänen, Syksy; Hotchkiss, Shaun +1 more
The discovery of a void of size ∼200 h-1 Mpc and average density contrast of ∼-0.1 aligned with the cold spot direction has been recently reported. It has been argued that, although the first-order integrated Sachs-Wolfe (ISW) effect of such a void on the cosmic microwave background is small, the second-order Rees-Sciama (RS) contributi…
Primordial magnetic field limits from the CMB trispectrum: Scalar modes and Planck constraints
Subramanian, Kandaswamy; Seshadri, T. R.; Trivedi, Pranjal
Cosmic magnetic fields are observed to be coherent on large scales and could have a primordial origin. Non-Gaussian signals in the cosmic microwave background (CMB) are generated by primordial magnetic fields as the magnetic stresses and temperature anisotropy they induce depend quadratically on the magnetic field. We compute the CMB scalar trispe…
Spatially Resolving the Very High Energy Emission from MGRO J2019+37 with VERITAS
Fortin, P.; Reyes, L. C.; Aune, T. +80 more
We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (~2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (S…
A Rigorous Free-form Lens Model of A2744 to Meet the Hubble Frontier Fields Challenge
Broadhurst, Tom; Zheng, Wei; Coe, Dan +4 more
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters provides access to the most magnified distant galaxies. The challenge is to construct lens models capable of describing these complex massive, merging clusters so that individual lensed systems can be reliably identified and their intrinsic properties accurately derived. We…
A volume-limited sample of X-ray galaxy groups and clusters - II. X-ray cavity dynamics
Fabian, A. C.; Hlavacek-Larrondo, J.; Sanders, J. S. +1 more
We present the results of our study of a volume-limited sample (z ≤ 0.071) of 101 X-ray galaxy groups and clusters, in which we explore the X-ray cavity energetics. Out of the 101 sources in our parent sample, X-ray cavities are found in 30 of them, all of which have a central cooling time of ≤3 Gyr. New X-ray cavities are detected in three source…
The Onset of Spiral Structure in the Universe
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
The onset of spiral structure in galaxies appears to occur between redshifts 1.4 and 1.8 when disks have developed a cool stellar component, rotation dominates over turbulent motions in the gas, and massive clumps become less frequent. During the transition from clumpy to spiral disks, two unusual types of spirals are found in the Hubble Ultra Dee…
Mid-infrared spectroscopy of Uranus from the Spitzer infrared spectrometer: 2. Determination of the mean composition of the upper troposphere and stratosphere
Fletcher, Leigh N.; Moses, Julianne I.; Line, Michael R. +7 more
Mid-infrared spectral observations Uranus acquired with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope are used to determine the abundances of C2H2, C2H6, CH3C2H, C4H2, CO2, and tentatively CH3 on Uranus at the time of the …
Time-Dependent Modulation of Cosmic Rays in the Heliosphere
Ferreira, S. E. S.; Potgieter, M. S.; Manuel, R.
The time-dependent modulation of galactic cosmic rays in the heliosphere is studied by computing intensities using a time-dependent modulation model. By introducing recent theoretical advances in the transport coefficients in the model, computed intensities are compared with Voyager 1, International Monitoring Platform (IMP) 8, and Ulysses proton …
The Solar Wind Neon Abundance Observed with ACE/SWICS and Ulysses/SWICS
Landi, Enrico; Zurbuchen, Thomas H.; von Steiger, Rudolf +5 more
Using in situ ion spectrometry data from ACE/SWICS, we determine the solar wind Ne/O elemental abundance ratio and examine its dependence on wind speed and evolution with the solar cycle. We find that Ne/O is inversely correlated with wind speed, is nearly constant in the fast wind, and correlates strongly with solar activity in the slow wind. In …
The Star-forming Galaxy Contribution to the Cosmic MeV and GeV Gamma-Ray Background
Beacom, John F.; Horiuchi, Shunsaku; Lacki, Brian C.
Star-forming galaxies could be major contributors to the cosmic GeV γ-ray background, and they are expected to be MeV-dim because of the "pion bump" falling off below ~100 MeV. However, there are very few observations of galaxies in the MeV range and other emission processes could be present. We investigate the MeV background from star-forming gal…