Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

Ultra-relativistic electrons in Jupiter's radiation belts

Abstract: Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission1: thermal atmospheric emission and synchrotron emission2 from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements3,4 confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for electrons at energies up to 20 MeV. Although most radiation belt models predict electrons at higher energies5,6, adiabatic diffusion theory can account only for energies up to around 20 MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8 GHz synchrotron emission that confirm the presence of electrons with energies up to 50 MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20 MeV are more numerous than previously believed.

Eccentric, nonspinning, inspiral, Gaussian-process merger approximant for the detection and characterization of eccentric binary black hole mergers

Abstract: National Science Foundation [OCI-0725070, ACI-1238993]; State of Illinois; NCSA; SPIN (Students Pushing Innovation) Program at NCSA; CITA from NSERC of Canada; Ontario Early Researcher Awards Program; Canada Research Chairs Program; Canadian Institute for Advanced Research; European Union's Horizon research and innovation program under the Marie Sklodowska-Curie Grant [690904]; STFC Consolidator Grant [ST/L000636/1]; NSF [1550514]

The Importance of Major Mergers in the Build Up of Stellar Mass in Brightest Cluster Galaxies at z = 1

Abstract: Recent independent results from numerical simulations and observations have shown that brightest cluster galaxies (BCGs) have increased their stellar mass by a factor of almost 2 between z ∼ 0.9 and z ∼ 0.2. The numerical simulations further suggest that more than half this mass is accreted through major mergers. Using a sample of 18 distant galaxy clusters with over 600 spectroscopically confirmed cluster members between them, we search for observational evidence that major mergers do play a significant role. We find a major merger rate of 0.38 ± 0.14 mergers per Gyr at z ∼ 1. While the uncertainties, which stem from the small size of our sample, are relatively large, our rate is consistent with the results that are derived from numerical simulations. If we assume that this rate continues to the present day and that half of the mass of the companion is accreted on to the BCG during these mergers, then we find that this rate can explain the growth in the stellar mass of the BCGs that is observed and predicted by simulations. Major mergers therefore appear to be playing an important role, perhaps even the dominant one, in the build up of stellar mass in these extraordinary galaxies.