Search Publications
A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
Tlatov, A.; Illarionov, E.; Sokoloff, D. +1 more
We obtain the latitude-time distribution of the averaged tilt angle of solar bipoles. For large bipoles, which are mainly bipolar sunspot groups, the spatially averaged tilt angle is positive in the Northern solar hemisphere and negative in the Southern, with modest variations during the course of the solar cycle. We consider the averaged tilt ang…
Helioseismic calibration of the equation of state and chemical composition in the solar convective envelope
Vorontsov, S. V.; Baturin, V. A.; Ayukov, S. V. +1 more
Accurate and precise measurements of solar p-mode frequencies allow sensitive diagnostics of the adiabatic exponent Γ1 = (∂ln p/∂ln ρ)S as a function of depth in the adiabatically stratified part of the solar convective envelope. The profile of the adiabatic exponent contains information about the chemical composition of the …
Rehabilitating C IV-based black hole mass estimates in quasars
Shang, Zhaohui; Brotherton, M. S.; Runnoe, Jessie C. +1 more
Currently, the ability to produce black hole mass estimates using the C IV λ1549 line that are consistent with Hβ mass estimates is uncertain, due in large part to disagreement between velocity line width measurements for the two lines. This discrepancy between Hβ and C IV arises from the fact that both line profiles are treated the same way in si…
Weak lensing analysis of RXC J2248.7-4431
Zenteno, A.; Gruen, D.; Young, J. +8 more
We present a weak lensing analysis of the cluster of galaxies RXC J2248.7-4431, a massive system at z = 0.3475 with prominent strong lensing features covered by the Cluster Lensing And Supernova survey with Hubble (CLASH). Based on UBVRIZ imaging from the Wide-Field Imager camera at the MPG/ESO 2.2-m telescope, we measure photometric redshifts and…
Newborn spheroids at high redshift: when and how did the dominant, old stars in today's massive galaxies form?
Ryan, R. E.; O'Connell, R. W.; Dekel, A. +10 more
We study ∼330 massive (M* > 109.5 M⊙), newborn spheroidal galaxies (SGs) around the epoch of peak star formation (1 < z < 3) to explore the high-redshift origin of SGs and gain insight into when and how the old stellar populations that dominate today's Universe formed. The sample is drawn from the Hubble S…
The flux-dependent X-ray time lags in NGC 4051
Vaughan, S.; Uttley, P.; Alston, W. N.
We present an analysis of the X-ray time lags for the highly variable Seyfert 1 galaxy NGC 4051, based on a series of XMM-Newton observations taken in 2009. We investigate the Fourier frequency dependent time lags in the light curves between the 0.3-1.0 keV and 2.0-5.0 keV energy bands as a function of source flux, including simultaneous modelling…
Constraints on the nature of CID-42: recoil kick or supermassive black hole pair?
Elvis, Martin; Loeb, Abraham; Blecha, Laura +1 more
The galaxy CXOC J100043.1+020637, also known as CID-42, is a highly unusual object. As an apparent galaxy merger remnant, it displays signatures of both an inspiraling, kiloparsec-scale active galactic nucleus (AGN) pair and of a recoiling AGN with a kick velocity of ≳ 1300 km s-1. Among recoiling AGN candidates, CID-42 alone has both s…
The baryon budget on the galaxy group/cluster boundary
Zabludoff, Ann I.; Gonzalez, Anthony H.; Zaritsky, Dennis +4 more
We present a study of the hot gas and stellar content of five optically selected poor galaxy clusters, including a full accounting of the contribution from intracluster light (ICL) and a combined hot gas and hydrostatic X-ray mass analysis with XMM-Newton observations. We find weighted mean stellar (including ICL), gas and total baryon mass fracti…
On the shear estimation bias induced by the spatial variation of colour across galaxy profiles
Schrabback, T.; Huang, Z.; Hoekstra, H. +13 more
The spatial variation of the colour of a galaxy may introduce a bias in the measurement of its shape if the point spread function (PSF) profile depends on wavelength. We study how this bias depends on the properties of the PSF and the galaxies themselves. The bias depends on the scales used to estimate the shape, which may be used to optimize meth…
Unveiling new members in five nearby young moving groups
Ábrahám, P.; Kóspál, Á.; Kiss, L. L. +5 more
In the past decade many kinematic groups of young stars (<100 Myr) were discovered in the solar neighbourhood. Since the most interesting period of planet formation overlaps with the age of these groups, their well dated members are attractive targets for exoplanet searches by direct imaging. We combined astrometric, photometric and X-ray data,…