Search Publications
Constraining black hole masses in low-accreting active galactic nuclei using X-ray spectra
Titarchuk, L.; Gliozzi, M.; Jang, I. +1 more
In a recent work we demonstrated that a novel X-ray scaling method, originally introduced for Galactic black holes (BHs), can be reliably extended to estimate the mass of supermassive BHs accreting at a moderate to high level. Here we investigate the limits of applicability of this method to low-accreting active galactic nuclei (AGN), using a cont…
Control of periodic variations in Saturn's magnetosphere by compressional waves
Kivelson, Margaret Galland; Jia, Xianzhe
Many of the periodic variations observed in Saturn's magnetosphere can be linked directly to the presence of a rotating pattern of field-aligned currents that link the northern and southern ionospheres with each other and with the magnetosphere. Such a current system is incorporated in a magnetohydrodynamic simulation that has previously been show…
Stellar content of the metal-poor galaxy DDO 68
Tikhonov, N. A.; Galazutdinova, O. A.; Lebedev, V. S.
Based on archival Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for the metal-poor galaxy DDO 68. The apparent distributions of stars of different ages and stellarmetallicity determinations indicate that DDO68 is a systemof two galaxies that have different stellar metallicities ( Z = 0.004 and 0.001) and are in the st…
An ALMA Survey of Sub-millimeter Galaxies in the Extended Chandra Deep Field South: Sub-millimeter Properties of Color-selected Galaxies
Smail, I.; Greve, T. R.; Walter, F. +16 more
We study the sub-millimeter properties of color-selected galaxies via a stacking analysis applied for the first time to interferometric data at sub-millimeter wavelengths. We base our study on 344 GHz ALMA continuum observations of ~20''-wide fields centered on 86 sub-millimeter sources detected in the LABOCA Extended Chandra Deep Field South (ECD…
Polar confinement of Saturn's magnetosphere revealed by in situ Cassini observations
Coates, A. J.; Dougherty, M. K.; Masters, A. +4 more
Plasma rotation plays a large role in determining the size and shape of Saturn's disk-like magnetosphere. A magnetosphere more confined to the equator in the polar regions is expected as a result of the interaction between this type of obstacle and the solar wind. In addition, at times away from equinox, a north-south asymmetry is expected where t…
Evidence for Two Separate Heliospheric Current Sheets of Cylindrical Shape During Mid-2012
Young, P. R.; Wang, Y. -M.; Muglach, K.
During the reversal of the Sun's polar fields at sunspot maximum, outward extrapolations of magnetograph measurements often predict the presence of two or more current sheets extending into the interplanetary medium, instead of the single heliospheric current sheet (HCS) that forms the basis of the standard "ballerina skirt" picture. By comparing …
HST-COS Spectroscopy of the Cooling Flow in A1795—Evidence for Inefficient Star Formation in Condensing Intracluster Gas
Veilleux, Sylvain; Roediger, Joel; McDonald, Michael +1 more
We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope of a cool, star-forming filament in the core of A1795. These data, which span 1025 Å < λrest < 1700 Å, allow for the simultaneous modeling of the young stellar populations and the intermediate-temperature (105.5 K) gas in t…
Tracing the cosmic velocity field at z 0.1 from galaxy luminosities in the SDSS DR7
Nusser, Adi; Feix, Martin; Branchini, Enzo
Spatial modulations in the distribution of observed luminosities (computed using redshifts) of ~ 5× 105 galaxies from the SDSS Data Release 7, probe the cosmic peculiar velocity field out to z~ 0.1. Allowing for luminosity evolution, the r-band luminosity function, determined via a spline-based estimator, is well represented by a Schech…
Spectral energy distributions of the BL Lac PKS 2155 - 304 from XMM-Newton
Bhagwan, Jai; Gupta, Alok C.; Papadakis, I. E. +1 more
We have used all 20 archival XMM-Newton observations of PKS 2155 - 304 with simultaneous X-ray and UV/optical data to study its long-term flux and spectral variability. We find significant variations, in all bands, on time-scales of years with an rms amplitude of ∼35-45 per cent, though the optical/UV variations are not correlated with those in th…
Shocks and Star Formation in Stephan's Quintet. I. Gemini Spectroscopy of Hα-bright Knots
Bastian, N.; Appleton, P. N.; Smith, L. J. +8 more
We present a Gemini-GMOS spectroscopic study of Hubble Space Telescope (HST)-selected Hα-emitting regions in Stephan's Quintet (HCG 92), a nearby compact galaxy group, with the aim of disentangling the processes of shock-induced heating and star formation in its intra-group medium. The ≈40 sources are distributed across the system, but most densel…