Search Publications
Using the Fundamental Plane of black hole activity to distinguish X-ray processes from weakly accreting black holes
Anderson, Scott F.; Plotkin, Richard M.; Markoff, Sera +2 more
The Fundamental Plane of black hole activity is a relation between X-ray luminosity, radio luminosity and black hole mass for hard-state Galactic black holes and their supermassive analogues. The Fundamental Plane suggests that, at low-accretion rates, the physical processes regulating the conversion of an accretion flow into radiative energy coul…
Modeling the Effects of Star Formation Histories on Hα and Ultraviolet Fluxes in nearby Dwarf Galaxies
Skillman, Evan D.; Williams, Benjamin F.; Johnson, L. Clifton +9 more
We consider the effects of non-constant star formation histories (SFHs) on Hα and GALEX far-ultraviolet (FUV) star formation rate (SFR) indicators. Under the assumption of a fully populated Chabrier initial mass function (IMF), we compare the distribution of Hα-to-FUV flux ratios from ~1500 simple, periodic model SFHs with observations of 185 gala…
X-ray variability of 104 active galactic nuclei. XMM-Newton power-spectrum density profiles
Vaughan, S.; González-Martín, O.
Context. Active galactic nuclei (AGN), powered by accretion onto supermassive black holes (SMBHs), are thought to be scaled up versions of Galactic black hole X-ray binaries (BH-XRBs). In the past few years evidence of such correspondence include similarities in the broadband shape of the X-ray variability power spectra, with characteristic bend t…
X-ray-optical classification of cluster mergers and the evolution of the cluster merger fraction
Mann, Andrew W.; Ebeling, Harald
We present the results of a simple but robust morphological classification of a statistically complete sample of 108 of the most X-ray-luminous clusters at 0.15 ≤z≤ 0.7 observed with Chandra. Our aims are to (a) identify the most disturbed massive clusters to be used as gravitational lenses for studies of the distant Universe and as probes of part…
Resolving the Electron Temperature Discrepancies in H II Regions and Planetary Nebulae: κ-distributed Electrons
Dopita, Michael A.; Nicholls, David C.; Sutherland, Ralph S.
The measurement of electron temperatures and metallicities in H II regions and planetary nebulae (PNe) has—for several decades—presented a problem: results obtained using different techniques disagree. What is worse, they disagree consistently. There have been numerous attempts to explain these discrepancies, but none has provided a satisfactory s…
Large-scale electron acceleration by parallel electric fields during magnetic reconnection
Egedal, J.; Daughton, W.; Le, A.
Magnetic reconnection is a process by which the field lines of a magnetized plasma undergo dramatic realignment, releasing large amounts of energy. Large-scale simulations of reconnection events in the Earth's magnetosphere suggest that this process takes place over much greater distances than previously expected.
Fundamental Properties of Stars Using Asteroseismology from Kepler and CoRoT and Interferometry from the CHARA Array
Kawaler, S. D.; Thompson, M. J.; Christensen-Dalsgaard, J. +37 more
We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos paral…
Evidence for ultrafast outflows in radio-quiet AGNs - III. Location and energetics
Cappi, M.; Tombesi, F.; Reeves, J. N. +1 more
Using the results of a previous X-ray photoionization modelling of blueshifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this Letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upp…
The Evolution of Solar Flux from 0.1 nm to 160 µm: Quantitative Estimates for Planetary Studies
Meadows, Victoria S.; Cohen, Martin; Catling, David C. +3 more
Understanding changes in the solar flux over geologic time is vital for understanding the evolution of planetary atmospheres because it affects atmospheric escape and chemistry, as well as climate. We describe a numerical parameterization for wavelength-dependent changes to the non-attenuated solar flux appropriate for most times and places in the…
Energetic galaxy-wide outflows in high-redshift ultraluminous infrared galaxies hosting AGN activity
Ivison, R. J.; Smail, Ian; Alexander, D. M. +10 more
We present integral field spectroscopy observations, covering the [O III] λλ4959, 5007 emission-line doublet of eight high-redshift (z = 1.4-3.4) ultraluminous infrared galaxies (ULIRGs) that host active galactic nucleus (AGN) activity, including known submillimetre luminous galaxies. The targets have moderate radio luminosities that are typical o…