Search Publications
Late-time Kilonova Light Curves and Implications to GW170817
Waxman, Eli; Ofek, Eran O.; Kushnir, Doron
We discuss the late-time (tens of days) emission from the radioactive ejecta of mergers involving neutron stars, when the ionization energy loss time of beta-decay electrons and positrons exceeds the expansion time. We show that if the e± are confined to the plasma (by magnetic fields), then the time dependence of the plasma heating rat…
The Role of Major Mergers and Nuclear Star Formation in Nearby Obscured Quasars
Ho, Luis C.; Zhao, Dongyao; Kim, Minjin +2 more
We investigate the triggering mechanism and the structural properties of obscured luminous active galactic nuclei from a detailed study of the rest-frame B and I Hubble Space Telescope images of 29 nearby (z ≈ 0.04-0.4) optically selected type 2 quasars. Morphological classification reveals that only a minority (34%) of the hosts are mergers or in…
Tidal Destruction in a Low-mass Galaxy Environment: The Discovery of Tidal Tails around DDO 44
Forbes, Duncan A.; Romanowsky, Aaron J.; Strader, Jay +10 more
We report the discovery of a ≳1° (∼50 kpc) long stellar tidal stream emanating from the dwarf galaxy DDO 44, a likely satellite of Local Volume galaxy NGC 2403 located ∼70 kpc in projection from its companion. NGC 2403 is a roughly Large Magellanic Cloud (LMC) stellar-mass galaxy 3 Mpc away, residing at the outer limits of the M81 group. We are ma…
Direct Estimates of the Solar Coronal Magnetic Field Using Contemporaneous Extreme-ultraviolet, Radio, and White-light Observations
Kumari, Anshu; Ramesh, R.; Kathiravan, C. +2 more
We report a solar coronal split-band type II radio burst that was observed on 2016 March 16 with the Gauribidanur Radio Spectro-Polarimeter in the frequency range ≈90-50 MHz, and the Gauribidanur RadioheliograPH at two discrete frequencies, viz. 80 and 53.3 MHz. Observations around the same epoch in extreme ultraviolet (EUV) and white light show t…
Transient Inverse-FIP Plasma Composition Evolution within a Solar Flare
Long, David M.; Matthews, Sarah A.; Brooks, David H. +9 more
Understanding elemental abundance variations in the solar corona provides an insight into how matter and energy flow from the chromosphere into the heliosphere. Observed variations depend on the first ionization potential (FIP) of the main elements of the Sun’s atmosphere. High-FIP elements (>10 eV) maintain photospheric abundances in the coron…
On a New Method to Estimate the Distance, Reddening, and Metallicity of RR Lyrae Stars Using Optical/Near-infrared (B, V, I, J, H, K) Mean Magnitudes: ω Centauri as a First Test Case
Walker, A. R.; Mateo, M.; Valenti, E. +26 more
We developed a new approach to provide accurate estimates of the metal content, reddening, and true distance modulus of RR Lyrae stars (RRLs). The method is based on homogeneous optical (BVI) and near-infrared (JHK) mean magnitudes and on predicted period-luminosity-metallicity relations (IJHK) and absolute mean magnitude-metallicity relations (BV…
Anchor Point of Electron Acceleration around Dipolarization Fronts in Space Plasmas
Fu, H. S.; Liu, C. M.
An anchor point, which is an energy threshold above which electrons are accelerated and below which electrons are decelerated, has recently been reported within the dipolarizing flux bundles behind dipolarization fronts (DFs) both in observations and simulations. However, what determines this point and how it is formed remain unclear. In this stud…
Galaxy Merger Fractions in Two Clusters at z\sim 2 Using the Hubble Space Telescope
Papovich, Casey; van Dokkum, Pieter; Momcheva, Ivelina +9 more
We measure the fraction of galaxy-galaxy mergers in two clusters at z ∼ 2 using imaging and grism observations from the Hubble Space Telescope. The two galaxy cluster candidates were originally identified as overdensities of objects using deep mid-infrared imaging and observations from the Spitzer Space Telescope, and were subsequently followed up…
An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). V. The Period-Luminosity Relation for Dusty Metal-poor AGB Stars
van Loon, J. Th.; Gehrz, R. D.; Skillman, E. D. +10 more
The survey for DUST in Nearby Galaxies with Spitzer (DUSTiNGS) has identified hundreds of candidate dust-producing asymptotic giant branch (AGB) stars in several nearby metal-poor galaxies. We have obtained multi-epoch follow-up observations for these candidates with the Spitzer Space Telescope and measured their infrared (IR) light curves. This h…
Testing Feedback-regulated Star Formation in Gas-rich, Turbulent Disk Galaxies
Bolatto, A. D.; Fisher, D. B.; Glazebrook, K. +3 more
In this paper we compare the molecular gas depletion times and midplane hydrostatic pressure in turbulent, star-forming disk galaxies to internal properties of these galaxies. For this analysis we use 17 galaxies from the DYNAMO sample of nearby (z ∼ 0.1) turbulent disks. We find a strong correlation, such that galaxies with lower molecular gas de…