Search Publications
New Detections of Arsenic, Selenium, and Other Heavy Elements in Two Metal-poor Stars
Beers, Timothy C.; Roederer, Ian U.; Frebel, Anna +6 more
We use the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope to obtain new high-quality spectra covering the 1900 <=λ <= 2360 Å wavelength range for two metal-poor stars, HD 108317 and HD 128279. We derive abundances of Cu II, Zn II, As I, Se I, Mo II, and Cd II, which have not been detected previously in either star. …
The Corona of HD 189733 and its X-Ray Activity
Günther, H. M.; Sciortino, S.; Drake, J. J. +5 more
Testing whether close-in massive exoplanets (hot Jupiters) can enhance the stellar activity in their host primary is crucial for the models of stellar and planetary evolution. Among systems with hot Jupiters, HD 189733 is one of the best studied because of its proximity, strong activity, and the presence of a transiting planet, which allows transm…
The Distribution of Polarized Radio Sources >15 µJy in GOODS-N
Owen, F. N.; Rudnick, L.
We present deep Very Large Array observations of the polarization of radio sources in the GOODS-N field at 1.4 GHz at resolutions of 1.''6 and 10''. At 1.''6, we find that the peak flux cumulative number count distribution is N(> p) ~ 45*(p/30 µJy)-0.6 per square degree above a detection threshold of 14.5 µJy. This repres…
Hubble Space Telescope Grism Spectroscopy of Extreme Starbursts across Cosmic Time: The Role of Dwarf Galaxies in the Star Formation History of the Universe
Martin, Crystal L.; Teplitz, Harry I.; Bunker, Andrew J. +15 more
Near infrared slitless spectroscopy with the Wide Field Camera 3, on board the Hubble Space Telescope, offers a unique opportunity to study low-mass galaxy populations at high redshift (z ~ 1-2). While most high-z surveys are biased toward massive galaxies, we are able to select sources via their emission lines that have very faint continua. We in…
ALMA Observations of a Candidate Molecular Outflow in an Obscured Quasar
Greene, Jenny E.; Zakamska, Nadia L.; Nesvadba, Nicole P. H. +1 more
We present Atacama Large Millimeter/Submillimeter Array CO (1-0) and CO (3-2) observations of SDSS J135646.10+102609.0, an obscured quasar and ultra-luminous infrared galaxy with two merging nuclei and a known 20 kpc scale ionized outflow. The total molecular gas mass is M_{mol}\approx 9^{+19}_{-6}\times 10^8 M ⊙, mostly distributed in …
Spatially Resolving the Very High Energy Emission from MGRO J2019+37 with VERITAS
Fortin, P.; Reyes, L. C.; Aune, T. +80 more
We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (~2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (S…
A Rigorous Free-form Lens Model of A2744 to Meet the Hubble Frontier Fields Challenge
Broadhurst, Tom; Zheng, Wei; Coe, Dan +4 more
Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters provides access to the most magnified distant galaxies. The challenge is to construct lens models capable of describing these complex massive, merging clusters so that individual lensed systems can be reliably identified and their intrinsic properties accurately derived. We…
The Onset of Spiral Structure in the Universe
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
The onset of spiral structure in galaxies appears to occur between redshifts 1.4 and 1.8 when disks have developed a cool stellar component, rotation dominates over turbulent motions in the gas, and massive clumps become less frequent. During the transition from clumpy to spiral disks, two unusual types of spirals are found in the Hubble Ultra Dee…
The Solar Wind Neon Abundance Observed with ACE/SWICS and Ulysses/SWICS
Landi, Enrico; Zurbuchen, Thomas H.; von Steiger, Rudolf +5 more
Using in situ ion spectrometry data from ACE/SWICS, we determine the solar wind Ne/O elemental abundance ratio and examine its dependence on wind speed and evolution with the solar cycle. We find that Ne/O is inversely correlated with wind speed, is nearly constant in the fast wind, and correlates strongly with solar activity in the slow wind. In …
The Star-forming Galaxy Contribution to the Cosmic MeV and GeV Gamma-Ray Background
Beacom, John F.; Horiuchi, Shunsaku; Lacki, Brian C.
Star-forming galaxies could be major contributors to the cosmic GeV γ-ray background, and they are expected to be MeV-dim because of the "pion bump" falling off below ~100 MeV. However, there are very few observations of galaxies in the MeV range and other emission processes could be present. We investigate the MeV background from star-forming gal…