Search Publications
A Joint Model of X-Ray and Infrared Backgrounds. II. Compton-thick Active Galactic Nucleus Abundance
Armus, Lee; Helou, George; Shi, Yong
We estimate the abundance of Compton-thick (CT) active galactic nuclei (AGNs) based on our joint model of X-ray and infrared backgrounds. At L rest2-10 keV > 1042 erg s-1, the CT AGN density predicted by our model is a few ×10-4 Mpc-3 from z = 0 up to z = 3. CT AGNs with higher luminosity c…
The influence of slope morphology on gullies: Terrestrial gullies in Lake George as analogues for Mars
Hobbs, S. W.; Paull, D. J.; Clarke, J. D. A.
Terrestrial gullies provide a useful benchmark to compare martian gully forms against. We compare pole and equator facing gullies in an unnamed crater located in the martian southern mid-latitudes with gullies located on the Lake George escarpment south of Gearys Gap, New South Wales, Australia. Our investigations showed gully morphology at both s…
The Planck Sunyaev-Zel'dovich versus the X-Ray View of the Coma Cluster
Lapi, A.; Cavaliere, A.; Fusco-Femiano, R.
The Planck collaboration has recently published precise and resolved measurements of the Sunyaev-Zel'dovich (SZ) effect in Abell 1656 (the Coma cluster of galaxies), thus directly gauging the electron pressure profile in the intracluster plasma. On the other hand, such a quantity may be also derived from combining the density and temperature provi…
A Magnetic Reconnection Origin for the Soft X-Ray Excess in an Active Galactic Nucleus
Wang, Jiancheng; Zhong, Xiaogu
We present a new scenario to explain the soft X-ray excess in an active galactic nucleus (AGN). Magnetic reconnection could happen in a thin layer on the surface of an accretion disk. Electrons are accelerated by a shock wave and turbulence is triggered by magnetic reconnection. Inverse Compton scattering then takes place above the accretion disk,…
An XMM-Newton search for X-ray sources in the Fornax dwarf galaxy
Nucita, A. A.; De Paolis, F.; Ingrosso, G. +2 more
We report the results of a deep archive XMM-Newton observation of the Fornax spheroidal galaxy that we analyzed with the aim of fully characterizing the X-ray source population (in most of the cases likely to be background active galactic nuclei) detected towards the target. A cross correlation with the available databases allowed us to find a sou…
Hubble Space Telescope Observations of Dusty Filaments in Hercules A: Evidence for Entrainment
Perley, R.; O'Dea, C. P.; Cotton, W. +3 more
We present U-, V-, and I-band images of the host galaxy of Hercules A (3C 348) obtained with HST/WFC3/UVIS. We find a network of dusty filaments which are more complex and extended than seen in earlier Hubble Space Telescope (HST) observations. The filaments are associated with a faint blue continuum light (possibly from young stars) and faint Hα …
X-ray, optical, and infrared investigation of the candidate supergiant fast X-ray transient IGR J18462 - 0223
Masetti, N.; Sidoli, L.; Bird, A. J. +4 more
We report on a broad-band X-ray study (0.5-60 keV) of the poorly known candidate supergiant fast X-ray transient (SFXT) IGR J18462 - 0223, and on optical and near-infrared (NIR) followup observations of field objects. The out-of-outburst X-ray state has been investigated for the first time with archival INTEGRAL/IBIS, ASCA, Chandra, and Swift/XRT …
Ultraluminous X-ray source XMMUJ132218.3-164247 is in fact a type I Quasar
Cappi, M.; Ponti, G.; Masetti, N. +5 more
Context. The true nature of ultraluminous X-ray sources (ULX) is still currently vigorously debated. One of the most interesting possibilities is that these sources are intermediate-mass (M ~ 103 - 105 M⊙) black holes. The most luminous ULX (L2 - 10 keV ~ 1041 erg s-1) are the most …
Features of the interaction of interplanetary coronal mass ejections/magnetic clouds with the Earth's magnetosphere
Farrugia, C. J.; Erkaev, N. V.; Torbert, R. B. +4 more
The interaction of interplanetary coronal mass ejections (ICMEs) and magnetic clouds (MCs) with the Earth's magnetosphere exhibits various interesting features principally due to interplanetary parameters which change slowly and reach extreme values of long duration. These, in turn, allow us to explore the geomagnetic response to continued and ext…
Modeling Solar Oscillation Power Spectra. II. Parametric Model of Spectral Lines Observed in Doppler-velocity Measurements
Jefferies, Stuart M.; Vorontsov, Sergei V.
We describe a global parametric model for the observed power spectra of solar oscillations of intermediate and low degree. A physically motivated parameterization is used as a substitute for a direct description of mode excitation and damping as these mechanisms remain poorly understood. The model is targeted at the accurate fitting of power spect…