Search Publications
Properties of Polycyclic Aromatic Hydrocarbons in the Northwest Photon Dominated Region of NGC 7023. I. PAH Size, Charge, Composition, and Structure Distribution
Boersma, C.; Bregman, J. D.; Allamandola, L. J.
Polycyclic aromatic hydrocarbon (PAH) emission in the Spitzer Infrared Spectrograph spectral map of the northwest photon dominated region (PDR) in NGC 7023 was analyzed exclusively using PAH spectra from the NASA Ames PAH IR Spectroscopic Database (www.astrochem.org/pahdb). The 5-15 µm spectrum at each pixel is fitted using a non-negative-le…
ALMA Observations of the HH 46/47 Molecular Outflow
Garay, Guido; Mardones, Diego; Noriega-Crespo, Alberto +3 more
The morphology, kinematics, and entrainment mechanism of the HH 46/47 molecular outflow were studied using new ALMA Cycle 0 observations. Results show that the blue and red lobes are strikingly different. We argue that these differences are partly due to contrasting ambient densities that result in different wind components having a distinct effec…
Improving the Precision of Time-delay Cosmography with Observations of Galaxies along the Line of Sight
Treu, Tommaso; Bradač, Maruša; Marshall, Philip J. +8 more
In order to use strong gravitational lens time delays to measure precise and accurate cosmological parameters the effects of mass along the line of sight must be taken into account. We present a method to achieve this by constraining the probability distribution function of the effective line-of-sight convergence κext. The method is bas…
Vlasov Simulations of Multi-ion Plasma Turbulence in the Solar Wind
Veltri, P.; Perrone, D.; Servidio, S. +2 more
Hybrid Vlasov-Maxwell simulations are employed to investigate the role of kinetic effects in a two-dimensional turbulent multi-ion plasma, composed of protons, alpha particles, and fluid electrons. In the typical conditions of the solar-wind environment, and in situations of decaying turbulence, the numerical results show that the velocity distrib…
On the Origin of Mass Segregation in NGC 3603
Grebel, Eva K.; Drissen, Laurent; Moffat, Anthony F. J. +5 more
We present deep Hubble Space Telescope/Wide Field and Planetary Camera 2 photometry of the young HD 97950 star cluster in the giant H II region NGC 3603. The data were obtained in 1997 and 2007 permitting us to derive membership based on proper motions of the stars. Our data are consistent with an age of 1 Myr for the HD 97950 cluster. A possible …
Discovery of a New Kind of Explosive X-Ray Transient near M86
Maccarone, T.; Fender, R.; Miller-Jones, J. C. A. +6 more
We present the discovery of a new type of explosive X-ray flash in Chandra images of the old elliptical galaxy M86. This unique event is characterized by the peak luminosity of 6 × 1042 erg s-1 for the distance of M86, the presence of precursor events, the timescale between the precursors and the main event (~4000 s), the abs…
Calibrating C-IV-based Black Hole Mass Estimators
Park, Daeseong; Denney, Kelly D.; Woo, Jong-Hak +1 more
We present the single-epoch black hole mass estimators based on the C IV λ1549 broad emission line, using the updated sample of the reverberation-mapped active galactic nuclei and high-quality UV spectra. By performing multi-component spectral fitting analysis, we measure the C IV line widths (FWHMC IV and line dispersion, σC IV <…
The NuSTAR Extragalactic Survey: A First Sensitive Look at the High-energy Cosmic X-Ray Background Population
Harrison, F. A.; Stern, D.; Zhang, W. W. +31 more
We report on the first 10 identifications of sources serendipitously detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) to provide the first sensitive census of the cosmic X-ray background source population at >~ 10 keV. We find that these NuSTAR-detected sources are ≈100 times fainter than those previously detected at >~ 10 keV …
Azimuthal Density Variations around the Rim of Tycho's Supernova Remnant
Petre, Robert; Reynolds, Stephen P.; Ghavamian, Parviz +5 more
Spitzer images of Tycho's supernova remnant in the mid-infrared reveal limb-brightened emission from the entire periphery of the shell and faint filamentary structures in the interior. As with other young remnants, this emission is produced by dust grains, warmed to ~100 K in the post-shock environment by collisions with energetic electrons and io…
Caught in the Act: The Assembly of Massive Cluster Galaxies at z = 1.62
Papovich, Casey; Ferguson, Henry C.; Koekemoer, Anton M. +13 more
We present the recent merger history of massive galaxies in a spectroscopically confirmed proto-cluster at z = 1.62. Using Hubble Space Telescope WFC3 near-infrared imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we select cluster and z ~ 1.6 field galaxies with M star >= 3 × 1010 M ⊙<…