Search Publications
Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Maoz, Dan +93 more
We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 Å. Significant diversity is seen in the near-maximum-light spectra (~…
Through the Looking Glass: Bright, Highly Magnified Galaxy Candidates at z ~ 7 behind A1703
Ford, H. C.; Zheng, W.; Zitrin, A. +7 more
We report the discovery of seven strongly lensed Lyman-break galaxy (LBG) candidates at z ~ 7 detected in Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging of A1703. The brightest candidate, called A1703-zD1, has an observed (lensed) magnitude of 24.0 AB (26σ) in the WFC3/IR F160W band, making it 0.2 mag brighter than the z 850-…
Near-infrared Imaging of a z = 6.42 Quasar Host Galaxy with the Hubble Space Telescope Wide Field Camera 3
Ryan, R. E.; Koekemoer, A. M.; Fan, X. +12 more
We report on deep near-infrared F125W (J) and F160W (H) Hubble Space Telescope Wide Field Camera 3 images of the z = 6.42 quasar J1148+5251 to attempt to detect rest-frame near-ultraviolet emission from the host galaxy. These observations included contemporaneous observations of a nearby star of similar near-infrared colors to measure temporal var…
Double Bow Shocks around Young, Runaway Red Supergiants: Application to Betelgeuse
Langer, Norbert; Neilson, Hilding R.; Mackey, Jonathan +2 more
A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow shock. In late evolutionary stages these stars may undergo rapid transitions from red to blue and …
Guiding Nonlinear Force-free Modeling Using Coronal Observations: First Results Using a Quasi-Grad-Rubin Scheme
Schrijver, C. J.; Wheatland, M. S.; Malanushenko, A. +2 more
At present, many models of the coronal magnetic field rely on photospheric vector magnetograms, but these data have been shown to be problematic as the sole boundary information for nonlinear force-free field extrapolations. Magnetic fields in the corona manifest themselves in high-energy images (X-rays and EUV) in the shapes of coronal loops, pro…
A Tale of Two Populations: The Contribution of Merger and Secular Processes to the Evolution of Active Galactic Nuclei
Ballantyne, D. R.; Draper, A. R.
Due to the co-evolution of supermassive black holes and their host galaxies, understanding the mechanisms that trigger active galactic nuclei (AGNs) is imperative to understanding galaxy evolution and the formation of massive galaxies. It is observationally difficult to determine the trigger of a given AGN due to the difference between the AGN lif…
Magnetic Energy and Helicity Budgets in the Active-region Solar Corona. II. Nonlinear Force-free Approximation
Georgoulis, Manolis K.; Tziotziou, Kostas; Raouafi, Nour-Eddine
Expanding on an earlier work that relied on linear force-free (LFF) magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free (NLFF) magnetic structure extending above a single known lower-boundary magnetic field vector. The propos…
A Comparison between the Stellar and Dynamical Masses of Six Globular Clusters
Bellazzini, M.; Sollima, A.; Lee, J. -W.
We present the results of a comprehensive analysis of the structure and kinematics of six Galactic globular clusters. By comparing the results of the most extensive photometric and kinematical surveys available to date with suitable dynamical models, we determine the stellar and dynamical masses of these stellar systems taking into account the eff…
Tracking down the Source Population Responsible for the Unresolved Cosmic 6-8 keV Background
Lehmer, B. D.; Alexander, D. M.; Bauer, F. E. +10 more
Using the 4 Ms Chandra Deep Field-South (CDF-S) survey, we have identified a sample of 6845 X-ray-undetected galaxies that dominates the unresolved ≈20%-25% of the 6-8 keV cosmic X-ray background (XRB). This sample was constructed by applying mass and color cuts to sources from a parent catalog based on GOODS-South Hubble Space Telescope z-band im…
Spatial Analysis of the Polycyclic Aromatic Hydrocarbon Features Southeast of the Orion Bar
Boersma, C.; Allamandola, L. J.; Rubin, R. H.
Polycyclic aromatic hydrocarbon (PAH) and dust emission features between 10 and 37 µm, observed with Spitzer at 11 positions southeast of the Bright Bar (BB) in Orion, are analyzed and connected to atomic and H2 lines reported earlier. Variations at these positions indicate changes in local conditions and materials sampled. The ma…