Search Publications
The Spitzer Ice Legacy: Ice Evolution from Cores to Protostars
Öberg, Karin I.; van Dishoeck, Ewine F.; Pontoppidan, Klaus M. +5 more
Ices regulate much of the chemistry during star formation and account for up to 80% of the available oxygen and carbon. In this paper, we use the Spitzer c2d Legacy ice survey, complimented with data sets on ices in cloud cores and high-mass protostars, to determine standard ice abundances and to present a coherent picture of the evolution of ices…
The Major and Minor Galaxy Merger Rates at z < 1.5
Somerville, Rachel S.; Lotz, Jennifer M.; Primack, Joel R. +4 more
Calculating the galaxy merger rate requires both a census of galaxies identified as merger candidates and a cosmologically averaged "observability" timescale langT obs(z)rang for identifying galaxy mergers. While many have counted galaxy mergers using a variety of techniques, langT obs(z)rang for these techniques have been po…
On Star Formation Rates and Star Formation Histories of Galaxies Out to z ~ 3
Koekemoer, Anton M.; Maiolino, Roberto; Daddi, Emanuele +23 more
We compare multi-wavelength star formation rate (SFR) indicators out to z ~ 3 in the GOODS-South field. Our analysis uniquely combines U to 8 µm photometry from FIREWORKS, MIPS 24 µm and PACS 70, 100, and 160 µm photometry from the PEP, and Hα spectroscopy from the SINS survey. We describe a set of conversions that lead to a cont…
Disequilibrium Carbon, Oxygen, and Nitrogen Chemistry in the Atmospheres of HD 189733b and HD 209458b
Moses, Julianne I.; Fortney, J. J.; Showman, A. P. +8 more
We have developed a one-dimensional photochemical and thermochemical kinetics and diffusion model to study the effects of disequilibrium chemistry on the atmospheric composition of "hot-Jupiter" exoplanets. Here we investigate the coupled chemistry of neutral carbon, hydrogen, oxygen, and nitrogen species on HD 189733b and HD 209458b and we compar…
Heating of the Solar Chromosphere and Corona by Alfvén Wave Turbulence
Cranmer, S. R.; van Ballegooijen, A. A.; DeLuca, E. E. +1 more
A three-dimensional magnetohydrodynamic (MHD) model for the propagation and dissipation of Alfvén waves in a coronal loop is developed. The model includes the lower atmospheres at the two ends of the loop. The waves originate on small spatial scales (less than 100 km) inside the kilogauss flux elements in the photosphere. The model describes the n…
The Bulk of the Black Hole Growth Since z ~ 1 Occurs in a Secular Universe: No Major Merger-AGN Connection
Koekemoer, Anton M.; Trump, Jonathan R.; Lisker, Thorsten +21 more
What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGNs) activity? To answer this long-standing question, we analyze 140 XMM-Newton-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z ~ 0.3-1.0 and M * < 1011.7 M sun w…
A Comprehensive Spectroscopic Analysis of DB White Dwarfs
Fontaine, G.; Bergeron, P.; Wesemael, F. +9 more
We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 M sun for our sample, with a dispersion of only 0.09 M sun. White dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample, and the…
The ACS Nearby Galaxy Survey Treasury. VIII. The Global Star Formation Histories of 60 Dwarf Galaxies in the Local Volume
McQuinn, Kristen B. W.; Dolphin, Andrew E.; Skillman, Evan D. +11 more
We present uniformly measured star formation histories (SFHs) of 60 nearby (D <~ 4 Mpc) dwarf galaxies based on color-magnitude diagrams of resolved stellar populations from images taken with the Hubble Space Telescope and analyzed as part of the ACS Nearby Galaxy Survey Treasury program (ANGST). This volume-limited sample contains 12 dwarf sph…
The Discovery of Y Dwarfs using Data from the Wide-field Infrared Survey Explorer (WISE)
Cushing, Michael C.; Kirkpatrick, J. Davy; Gelino, Christopher R. +13 more
We present the discovery of seven ultracool brown dwarfs identified with the Wide-field Infrared Survey Explorer (WISE). Near-infrared spectroscopy reveals deep absorption bands of H2O and CH4 that indicate all seven of the brown dwarfs have spectral types later than UGPS J072227.51-054031.2, the latest-type T dwarf currently…
A 100 pc Elliptical and Twisted Ring of Cold and Dense Molecular Clouds Revealed by Herschel Around the Galactic Center
Natoli, P.; Piacentini, F.; Polenta, G. +38 more
Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on board the Herschel satellite, reveal a ~3 × 107 M sun ring of dense and cold clouds orbiting the Galactic center. Using a simple toy model, an elliptical shape having semi-major axes of 100 and 60 pc is deduce…