Search Publications
Super-Eddington Accretion in the WISE-selected Extremely Luminous Infrared Galaxy W2246-0526
Tsai, Chao-Wei; Wright, Edward L.; Jun, Hyunsung D. +8 more
We use optical and near-infrared spectroscopy to observe rest-UV emission lines and estimate the black hole mass of WISEA J224607.56-052634.9 (W2246-0526) at z = 4.601, the most luminous hot, dust-obscured galaxy yet discovered by WISE. From the broad component of the Mg II 2799 Å emission line, we measure a black hole mass of log(M BH/…
An ALMA Survey of Faint Disks in the Chamaeleon I Star-forming Region: Why Are Some Class II Disks so Faint?
Pascucci, Ilaria; Herczeg, Gregory J.; Henning, Thomas +6 more
ALMA surveys of nearby star-forming regions have shown that the dust mass in the disk is correlated with the stellar mass, but with a large scatter. This scatter could indicate either different evolutionary paths of disks or different initial conditions within a single cluster. We present ALMA Cycle 3 follow-up observations for 14 Class II disks t…
Possible Signatures of a Termination Shock in the 2014 March 29 X-class Flare Observed by IRIS
Reeves, Katharine K.; Polito, Vanessa; Galan, Giselle +1 more
The standard model of flares predicts the existence of a fast-mode magnetohydrodynamic shock above the looptops, also known as termination shock (TS), as the result of the downward-directed outflow reconnection jets colliding with the closed magnetic loops. A crucial spectral signature of a TS is the presence of large Doppler shifts in the spectra…
The R-Process Alliance: Chemical Abundances for a Trio of r-process-enhanced Stars—One Strong, One Moderate, and One Mild
Casey, Andrew R.; Beers, Timothy C.; Placco, Vinicius M. +9 more
We present detailed chemical abundances of three new bright (V ∼ 11), extremely metal-poor ([Fe/H] ∼ -3.0), r-process-enhanced halo red giants based on high-resolution, high-S/N Magellan/MIKE spectra. We measured abundances for 20-25 neutron-capture elements in each of our stars. J1432-4125 is among the most r-process-rich r-II stars, with [Eu/Fe]…
Testing Viable f(T) Models with Current Observations
Wu, Puxun; Yu, Hongwei; Xu, Bing
We perform observational tests on the f(T) gravity with the BAO data (including the BOSS DR 12 galaxy sample, the DR12 Lyα-Forests measurement, the new eBOSS DR14 quasar sample, the 6dFGS, and the SDSS), the CMB distance priors from the Planck 2015, the SNIa data from the joint light-curve analysis, the latest H(z) data, and the local value of the…
A Decade of MWC 758 Disk Images: Where Are the Spiral-arm-driving Planets?
Debes, John H.; Schneider, Glenn; Esposito, Thomas M. +10 more
Large-scale spiral arms have been revealed in scattered light images of a few protoplanetary disks. Theoretical models suggest that such arms may be driven by and corotate with giant planets, which has called for remarkable observational efforts to look for them. By examining the rotation of the spiral arms for the MWC 758 system over a 10 year ti…
Reconnection in the Post-impulsive Phase of Solar Flares
Reeves, Katharine K.; Forbes, Terry G.; Seaton, Daniel B.
Using a recently developed analytical procedure, we determine the rate of magnetic reconnection in the “standard” model of eruptive solar flares. During the late phase, the neutral line is located near the lower tip of the reconnection current sheet, and the upper region of the current sheet is bifurcated into a pair of Petschek-type shocks. Despi…
The Optical/Near-infrared Extinction Law in Highly Reddened Regions
Hosek, Matthew W., Jr.; Lu, Jessica R.; Clarkson, William I. +6 more
A precise extinction law is a critical input when interpreting observations of highly reddened sources such as young star clusters and the Galactic Center (GC). We use Hubble Space Telescope observations of a region of moderate extinction and a region of high extinction to measure the optical and near-infrared extinction law (0.8-2.2 µm). Th…
Outflowing OH+ in Markarian 231: The Ionization Rate of the Molecular Gas
Sturm, E.; Veilleux, S.; Ashby, M. L. N. +6 more
The oxygen-bearing molecular ions OH+, H2O+, and H3O+ are key species that probe the ionization rate of (partially) molecular gas that is ionized by X-rays and cosmic-rays permeating the interstellar medium. We report Herschel far-infrared and submillimeter spectroscopic observations of OH
Chemical Abundances in the Leading Arm of the Magellanic Stream
Richter, Philipp; Lockman, Felix J.; Fox, Andrew J. +8 more
The Leading Arm (LA) of the Magellanic Stream is a vast debris field of H I clouds connecting the Milky Way and the Magellanic Clouds. It represents an example of active gas accretion onto the Galaxy. Previously, only one chemical abundance measurement had been made in the LA. Here we present chemical abundance measurements using Hubble Space Tele…