Search Publications
Supergranules as Probes of Solar Convection Zone Dynamics
Hathaway, David H.
Supergranules are convection cells seen at the Sun's surface as a space filling pattern of horizontal flows. While typical supergranules have diameters of about 35 Mm, they exhibit a broad spectrum of sizes from ~10 Mm to ~100 Mm. Here we show that supergranules of different sizes can be used to probe the rotation rate in the Sun's outer convectio…
Polycyclic Aromatic Hydrocarbon Processing in the Blast Wave of the Supernova Remnant N132D
Rho, J.; Boersma, C.; Tappe, A. +1 more
We present Spitzer Infrared Spectrograph 14-36 µm mapping observations of the supernova remnant N132D in the Large Magellanic Cloud. This study focuses on the processing of polycyclic aromatic hydrocarbons (PAHs) that we previously identified in the southern blast wave. The mid-infrared spectra show strong continuum emission from shock-heate…
The Evolution and Environments of X-Ray Emitting Active Galactic Nuclei in High-redshift Large-scale Structures
Fassnacht, C. D.; Kocevski, D. D.; Lemaux, B. C. +5 more
We use deep Chandra imaging and an extensive optical spectroscopy campaign on the Keck 10 m telescopes to study the properties of X-ray point sources in two isolated X-ray-selected clusters, two superclusters, and one "supergroup" at redshifts of z ~ 0.7-0.9. We first study X-ray point sources using the statistical measure of cumulative source cou…
The Panchromatic Hubble Andromeda Treasury. II. Tracing the Inner M31 Halo with Blue Horizontal Branch Stars
Bell, Eric F.; Williams, Benjamin F.; Gilbert, Karoline M. +7 more
We attempt to constrain the shape of M31's inner stellar halo by tracing the surface density of blue horizontal branch (BHB) stars at galactocentric distances ranging from 2 kpc to 35 kpc. Our measurements make use of resolved stellar photometry from a section of the Panchromatic Hubble Andromeda Treasury survey, supplemented by several archival H…
Flash Mixing on the White Dwarf Cooling Curve: Spectroscopic Confirmation in NGC 2808
Brown, Thomas M.; Hubeny, Ivan; Sweigart, Allen V. +3 more
We present new Hubble Space Telescope far-UV spectroscopy of two dozen hot evolved stars in NGC 2808, a massive globular cluster with a large population of "blue-hook" (BHk) stars. The BHk stars are found in ultraviolet color-magnitude diagrams of the most massive globular clusters, where they fall at luminosities immediately below the hot end of …
Seasonal Disappearance of Far-infrared Haze in Titan's Stratosphere
Calcutt, S. B.; de Kok, R.; Flasar, F. M. +9 more
A far-infrared emission band attributed to volatile or refractory haze in Titan's stratosphere has been decreasing in intensity since Cassini's arrival in 2004. The 220 cm-1 feature, first seen by the Voyager Infrared Interferometer Spectrometer, has only been found in Titan's winter polar region. The emission peaks at about 140 km alti…
Observations of a Two-stage Solar Eruptive Event (SEE): Evidence for Secondary Heating
Veronig, Astrid; Chamberlin, Phillip C.; Su, Yang +4 more
We present RHESSI, SDO/AIA, SOHO/LASCO, STEREO, and GOES observations of a partially occulted solar eruptive event that occurred at the southwest limb on 2011 March 8. The GOES X-ray light curve shows two peaks separated by almost 2 hr that we interpret as two stages of a single event associated with the delayed eruption of a coronal mass ejection…
A Link to the Past: Using Markov Chain Monte Carlo Fitting to Constrain Fundamental Parameters of High-redshift Galaxies
Koekemoer, Anton; Malhotra, Sangeeta; Rhoads, James +4 more
We have developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo that we have dubbed "πMC2." It allows us to compare observations to arbitrarily comp…
Analysis of a Fragmenting Sunspot Using Hinode Observations
Venkatakrishnan, P.; Ravindra, B.; Mathew, Shibu K. +3 more
We employ high-resolution filtergrams and polarimetric measurements from Hinode to follow the evolution of a sunspot for eight days starting on 2007 June 28. The imaging data were corrected for intensity gradients, projection effects, and instrumental stray light prior to the analysis. The observations show the formation of a light bridge at one c…
Passive and Star-forming Galaxies at 1.4 <= z <= 2.5 in the AEGIS Field
Fang, Guanwen; Kong, Xu; Chen, Yang +1 more
Using a simple two-color selection based on g-, z-, and K-band photometry, we choose from 1609 star-forming galaxies (sgzKs) and 422 passively evolving galaxies (pgzKs) at z ~ 2 from a K-band-selected sample (K AB < 22.0) in an area of ~0.44 deg2 of the All-wavelength Extended Groth Strip International Survey. The number o…