Search Publications
Red Nuggets at z ~ 1.5: Compact Passive Galaxies and the Formation of the Kormendy Relation
Glazebrook, Karl; McCarthy, Patrick J.; Yan, Haojing +13 more
We present the results of Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) imaging of a sample of 19 high-mass passively evolving galaxies with 1.2 < z < 2, taken primarily from the Gemini Deep Deep Survey (GDDS). Around 80% of galaxies in our GDDS sample have spectra dominated by stars with ages gsim1 Gyr. Our rest-frame R-band i…
The Nature of Flare Ribbons in Coronal Null-Point Topology
Aulanier, G.; Schrijver, C. J.; Masson, S. +1 more
Flare ribbons are commonly attributed to the low-altitude impact, along the footprints of separatrices or quasi-separatrix layers (QSLs), of particle beams accelerated through magnetic reconnection. If reconnection occurs at a three-dimensional coronal magnetic null point, the footprint of the dome-shaped fan surface would map a closed circular ri…
Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample
Fabian, A. C.; Vasudevan, R. V.
We employ contemporaneous optical, ultraviolet (UV) and X-ray observations from the XMM-Newton European Photon Imaging Camera (EPIC-pn) and Optical Monitor (OM) archives to present, for the first time, simultaneous spectral energy distributions (SEDs) for the majority of the Peterson et al. reverberation mapped sample of active galactic nuclei (AG…
The Space Density of Compton-Thick Active Galactic Nucleus and the X-Ray Background
Treister, E.; Urry, C. Megan; Virani, Shanil
We constrain the number density and evolution of Compton-thick (CT) active galactic nuclei (AGNs). In the local universe, we use the wide-area surveys from the Swift and INTEGRAL satellites, while for high redshifts we explore candidate selections based on a combination of X-ray and mid-infrared (mid-IR) parameters. We find a significantly lower s…
Multiple stellar populations in Magellanic Cloud clusters. I. An ordinary feature for intermediate age globulars in the LMC?
Anderson, J.; Milone, A. P.; Bedin, L. R. +1 more
Context: The discovery of multiple main sequences (MS) in the massive clusters NGC 2808 and Omega Centauri, along with multiple subgiant branches in NGC 1851 and NGC 6388 has challenged the long-held paradigm that globular clusters consist of simple stellar populations. This evolving picture has been further complicated by recent photometric studi…
Radio-Loud Narrow-Line Seyfert 1 as a New Class of Gamma-Ray Active Galactic Nuclei
Maraschi, L.; Caraveo, P. A.; Tagliaferri, G. +147 more
We report the discovery with Fermi/LAT of γ-ray emission from three radio-loud narrow-line Seyfert 1 galaxies: PKS 1502+036 (z = 0.409), 1H 0323+342 (z = 0.061), and PKS 2004 - 447 (z = 0.24). In addition to PMN J0948+0022 (z = 0.585), the first source of this type to be detected in γ rays, they may form an emerging new class of γ-ray active galac…
Star formation and mass assembly in high redshift galaxies
Fiore, F.; Castellano, M.; Pentericci, L. +14 more
Aims: The goal of this work is to infer the star formation properties and the mass assembly process of high redshift (0.3 ≤ z < 2.5) galaxies from their IR emission using the 24 µm band of MIPS-Spitzer.
Methods: We used an updated version of the GOODS-MUSIC catalog, which has multiwavelength coverage from 0.3 to 24 µm and either…
A massive hypergiant star as the progenitor of the supernova SN 2005gl
Gal-Yam, A.; Leonard, D. C.
Our understanding of the evolution of massive stars before their final explosions as supernovae is incomplete, from both an observational and a theoretical standpoint. A key missing piece in the supernova puzzle is the difficulty of identifying and studying progenitor stars. In only a single case-that of supernova SN 1987A in the Large Magellanic …
Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue
van Leeuwen, F.
Context: A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming that the accuracies for nearly all stars brighter than magnitude Hp = 8 are improved, by up to a factor 4, compared to the original catalogue. As correlations between the underlying abscissa residuals have also been reduced by more th…
Transits of Earth-like Planets
Kaltenegger, Lisa; Traub, Wesley A.
Transmission spectroscopy of Earth-like exoplanets is a potential tool for habitability screening. Transiting planets are present-day "Rosetta Stones" for understanding extrasolar planets because they offer the possibility to characterize giant planet atmospheres and should provide an access to biomarkers in the atmospheres of Earth-like exoplanet…