Search Publications
The Cause of the Weak Solar Cycle 24
Schüssler, M.; Jiang, J.; Cameron, R. H.
The ongoing 11 year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic flux, the source of the toroidal field responsible for solar magnetic activity in the subsequent cycle. Simulation of the evolution of the solar surface field shows that t…
The Atacama Cosmology Telescope: Lensing of CMB Temperature and Polarization Derived from Cosmic Infrared Background Cross-correlation
Hilton, Matt; Hasselfield, Matthew; Bond, J. Richard +49 more
We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by cross-correlating the reconstructed convergence signal from the first season of Atacama Cosmology Telescope Polarimeter data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the …
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters: The Internal Kinematics of the Multiple Stellar Populations in NGC 2808
Anderson, J.; Milone, A. P.; Marino, A. F. +9 more
Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many difficult challenges for the study of the formation and dynamical history of these stellar systems. In this Letter we present the results of a study of the kinematic properties of multiple populations in NGC 2808 …
Optically Thick H I Dominant in the Local Interstellar Medium: An Alternative Interpretation to "Dark Gas"
Fukui, Y.; Onishi, T.; Sano, H. +5 more
Dark gas in the interstellar medium (ISM) is believed to not be detectable either in CO or H I radio emission, but it is detectable by other means including γ rays, dust emission, and extinction traced outside the Galactic plane at |b| > 5°. In these analyses, the 21 cm H I emission is usually assumed to be completely optically thin. We have re…
Tracing the Reverberation Lag in the Hard State of Black Hole X-Ray Binaries
Nandra, K.; Ponti, G.; De Marco, B. +1 more
We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the …
A Clear Age-Velocity Dispersion Correlation in Andromeda’s Stellar Disk
Bell, Eric F.; Skillman, Evan D.; Williams, Benjamin F. +9 more
The stellar kinematics of galactic disks are key to constraining disk formation and evolution processes. In this paper, for the first time, we measure the stellar age-velocity dispersion correlation in the inner 20 kpc (∼3.5 disk scale lengths) of M31 and show that it is dramatically different from that in the Milky Way (MW). We use optical Hubble…
Magellan Adaptive Optics First-light Observations of the Exoplanet β Pic b. II. 3-5 µm Direct Imaging with MagAO+Clio, and the Empirical Bolometric Luminosity of a Self-luminous Giant Planet
Weinberger, Alycia J.; Bailey, Vanessa P.; Close, Laird M. +14 more
Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet β Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star β Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Pap…
Magnetically Driven Accretion Disk Winds and Ultra-fast Outflows in PG 1211+143
Behar, Ehud; Tombesi, Francesco; Shrader, Chris +3 more
We present a study of X-ray ionization of MHD accretion-disk winds in an effort to constrain the physics underlying the highly ionized ultra-fast outflows (UFOs) inferred by X-ray absorbers often detected in various sub classes of Seyfert active galactic nuclei (AGNs). Our primary focus is to show that magnetically driven outflows are indeed physi…
Nearby Galaxy Filaments and the Ly-alpha Forest: Confronting Simulations and the UV Background with Observations
Savage, Blair D.; Wakker, Bart P.; Oppenheimer, Benjamin D. +3 more
Simulations of the formation of large-scale structures predict that dark matter, low density highly ionized gas, and galaxies form 10 to 40 Mpc scale filaments. These structures are easily recognized in the distribution of galaxies. Here we use Lyα absorption lines to study the gas in 30 × 6 Mpc filament at cz ∼ 3500 km s-1, defined usi…
Correcting the z ∼ 8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
Stiavelli, Massimo; Schmidt, Kasper B.; Treu, Tommaso +7 more
We present a Bayesian framework to account for the magnification bias from both strong and weak gravitational lensing in estimates of high-redshift galaxy luminosity functions (LFs). We illustrate our method by estimating the z ∼ 8 UV LF using a sample of 97 Y-band dropouts (Lyman break galaxies) found in the Brightest of Reionizing Galaxies (BoRG…