Search Publications
Magnification Bias of Distant Galaxies in the Hubble Frontier Fields: Testing Wave Versus Particle Dark Matter Predictions
Broadhurst, Tom; Windhorst, Rogier; Schive, Hsi-Yu +4 more
Acting as powerful gravitational lenses, the strong lensing galaxy clusters of the deep Hubble Frontier Fields (HFF) program permit access to lower-luminosity galaxies lying at higher redshifts than hitherto possible. We analyzed the HFF to measure the volume density of Lyman-break galaxies at z > 4.75 by identifying a complete and reliable sam…
In-flight calibration of Hitomi Soft X-ray Spectrometer. (3) Effective area
Maeda, Yoshitomo; Tsujimoto, Masahiro; Okajima, Takashi +14 more
We present the result of the in-flight calibration of the effective area of the Soft X-ray Spectrometer (SXS) on board the Hitomi X-ray satellite using an observation of the Crab nebula. We corrected for artifacts when observing high count rate sources with the X-ray microcalorimeter. We then constructed a spectrum in the 0.5-20 keV band, which we…
Nuclear processes in astrophysics: Recent progress
Malheiro, M.; Liccardo, V.; Hussein, M. S. +2 more
The question about the origin of the elements is a fascinating one, that scientists have been trying to answer for the last seven decades. The formation of light elements in the primordial universe and heavier elements in astrophysical sources occurs through nuclear reactions. We can say that nuclear processes are responsible for the production of…
Toward a Quantitative Model for Simulation and Forecast of Solar Energetic Particle Production during Gradual Events. I. Magnetohydrodynamic Background Coupled to the SEP Model
Gombosi, T. I.; Taktakishvili, A.; Roussev, I. I. +2 more
Solar energetic particles (SEPs) are an important aspect of space weather. SEP events possess a high destructive potential, since they may cause disruptions of communication systems on Earth and be fatal to crew members on board spacecraft and, in extreme cases, harmful to people on board high-altitude flights. However, currently the research comm…
Constraining the Solar Galactic Reflex Velocity using Gaia Observations of the Sagittarius Stream
Law, David R.; Majewski, Steven R.; Hayes, Christian R.
Because of its particular orientation around the Galaxy—i.e., in a plane nearly perpendicular to the Galactic plane and containing both the Sun and Galactic center—the Sagittarius (Sgr) stream provides a powerful means by which to measure the solar reflex velocity, and thereby infer the velocity of the Local Standard of Rest (LSR), in a way that i…
A Wide-field Map of Intracluster Globular Clusters in Coma
O'Neill, Conor R.; Madrid, Juan P.; Gagliano, Alexander T. +1 more
The large-scale distribution of globular clusters in the central region of the Coma cluster of galaxies is derived through the analysis of Hubble Space Telescope/Advanced Camera for Surveys data. Data from three different HST observing programs are combined in order to obtain a full surface density map of globular clusters in the core of Coma. A t…
The variability of the warm absorber in I Zwicky 1 as seen by XMM-Newton
Brandt, W. N.; Kriss, G. A.; Costantini, E. +4 more
We present new XMM-Newton observations of the intriguing warm absorber in I Zwicky 1. This luminous and nearby narrow-line Seyfert 1 galaxy shows ionized absorption by two components of outflowing gas; a low and a high-ionization phase with log ξ ∼ 0 and log ξ ∼ 2, respectively. Detailed modelling of these data reveal a complex and variable multip…
Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue
Bobylev, V. V.; Bajkova, A. T.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance sca…
Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements
Waite, J. Hunter; Hörst, S. M.; Perry, M. E. +4 more
Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 3…
An X-ray view of central engines of low-luminosity quasars (LLQSO) in the local Universe
Guainazzi, Matteo; Laha, Sibasish; Markowitz, Alex G. +1 more
We have carried out a systematic X-ray spectral analysis of a sample of low-luminosity quasars (LLQSO) to investigate the nature of the central engines of these sources. The optically selected LLQSO sample consists of close, known bright active galactic nuclei (AGN) which serves as an important link between the powerful quasars at higher redshift …