Search Publications
Hubble Space Telescope Observations of the Double-peaked Emission Lines in the Seyfert Galaxy Markarian 78: Mass Outflows from a Single Active Galactic Nucleus
Kraemer, S. B.; Crenshaw, D. M.; Schmitt, H. R. +3 more
Previous ground-based observations of the Seyfert 2 galaxy Mrk 78 revealed a double set of emission lines, similar to those seen in several active galactic nuclei (AGNs) from recent surveys. Are the double lines due to two AGNs with different radial velocities in the same galaxy, or are they due to mass outflows from a single AGN? We present a stu…
The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. IV. Construction and Validation of a Grid of Models for Oxygen-rich AGB Stars, Red Supergiants, and Extreme AGB Stars
Meixner, M.; Sargent, Benjamin A.; Srinivasan, S.
To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch s…
Population Parameters of Intermediate-age Star Clusters in the Large Magellanic Cloud. III. Dynamical Evidence for a Range of Ages Being Responsible for Extended Main-sequence Turnoffs
Chandar, Rupali; Goudfrooij, Paul; Puzia, Thomas H. +1 more
We present a new analysis of 11 intermediate-age (1-2 Gyr) star clusters in the Large Magellanic Cloud based on Hubble Space Telescope imaging data. Seven of the clusters feature main-sequence turnoff (MSTO) regions that are wider than can be accounted for by a simple stellar population, whereas their red giant branches (RGBs) indicate a single va…
Surface Chemistry and Particle Shape: Processes for the Evolution of Aerosols in Titan's Atmosphere
Lavvas, P.; Sander, M.; Kraft, M. +1 more
We use a stochastic approach in order to investigate the production and evolution of aerosols in Titan's atmosphere. The simulation initiates from the benzene molecules observed in the thermosphere and follows their evolution to larger aromatic structures through reaction with gas-phase radical species. Aromatics are allowed to collide and provide…
Effect of a Dark Matter Halo on the Determination of Black Hole Masses
Gebhardt, Karl; Schulze, Andreas
Stellar dynamical modeling is a powerful method to determine the mass of black holes in quiescent galaxies. However, in previous work the presence of a dark matter halo has been ignored in the modeling. Gebhardt & Thomas in 2009 showed that accounting for a dark matter halo increased the black hole mass of the massive galaxy M87 by a factor of…
Color and Stellar Population Gradients in Passively Evolving Galaxies at z ~ 2 from HST/WFC3 Deep Imaging in the Hubble Ultra Deep Field
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +10 more
We report the detection of color gradients in six massive (stellar mass (M star) > 1010 M ⊙) and passively evolving (specific star formation rate <10-11 yr-1) galaxies at redshift 1.3 < z < 2.5 identified in the Hubble Ultra Deep Field using ultra-deep Hubble Space Telescope (HST) …
The First Observations of Low-redshift Damped Lyα Systems with the Cosmic Origins Spectrograph
Sembach, K. R.; Jenkins, E. B.; Prochaska, J. X. +6 more
We report on the first Cosmic Origins Spectrograph observations of damped Lyα systems (DLAs) and sub-damped Lyα systems (sub-DLAs) discovered in a new survey of the gaseous halos of low-redshift galaxies. From observations of 37 sightlines, we have discovered three DLAs and four sub-DLAs. We measure the neutral gas density ΩH I , and re…
Possible Charge-exchange X-ray Emission in the Cygnus Loop Detected with Suzaku
Katsuda, Satoru; Petre, Robert; Yamaguchi, Hiroya +8 more
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant's rim are depleted to ~0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to ~1 solar). The reason for these ano…
Constraints on Coronal Mass Ejection Evolution from in Situ Observations of Ionic Charge States
Antiochos, Spiro K.; Zurbuchen, Thomas H.; Gruesbeck, Jacob R. +1 more
We present a novel procedure for deriving the physical properties of coronal mass ejections (CMEs) in the corona. Our methodology uses in situ measurements of ionic charge states of C, O, Si, and Fe in the heliosphere and interprets them in the context of a model for the early evolution of interplanetary CME (ICME) plasma, between 2 and 5 R s…
LYRA Observations of Two Oscillation Modes in a Single Flare
Berghmans, D.; Goossens, M.; Zender, J. +2 more
We analyze light curves from the LYRA irradiance experiment on board PROBA2 during the flare of 2010 February 8. We see both long- and short-period oscillations during the flare. The long-period oscillation is interpreted in terms of standing slow sausage modes; the short-period oscillation is thought to be a standing fast sausage mode. The simult…