Search Publications
Globular Cluster Systems in Brightest Cluster Galaxies. II. NGC 6166
Whitmore, Bradley C.; Blakeslee, John P.; Rothberg, Barry +3 more
We present new deep photometry of the globular cluster system (GCS) around NGC 6166, the central supergiant galaxy in Abell 2199. Hubble Space Telescope data from the Advanced Camera for Surveys and WFC3 cameras in F475W and F814W are used to determine the spatial distribution of the GCS, its metallicity distribution function (MDF), and the depend…
Flare vs. Shock Acceleration of High-energy Protons in Solar Energetic Particle Events
Cliver, E. W.
Recent studies have presented evidence for a significant to dominant role for a flare-resident acceleration process for high-energy protons in large (“gradual”) solar energetic particle (SEP) events, contrary to the more generally held view that such protons are primarily accelerated at shock waves driven by coronal mass ejections (CMEs). The new …
The Detection of a Hot Molecular Core in the Large Magellanic Cloud with ALMA
Onaka, Takashi; Aikawa, Yuri; Shimonishi, Takashi +1 more
We report the first detection of a hot molecular core outside our Galaxy based on radio observations with ALMA toward a high-mass young stellar object (YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC). Molecular emission lines of CO, C17O, HCO+, H13CO+, H2CO, NO, SiO, …
Observational Signatures of Coronal Loop Heating and Cooling Driven by Footpoint Shuffling
Velli, M.; Warren, H. P.; Ugarte-Urra, I. +4 more
The evolution of a coronal loop is studied by means of numerical simulations of the fully compressible three-dimensional magnetohydrodynamic equations using the HYPERION code. The footpoints of the loop magnetic field are advected by random motions. As a consequence, the magnetic field in the loop is energized and develops turbulent nonlinear dyna…
NuSTAR and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A
Harrison, F. A.; Stern, D.; Farrah, D. +28 more
We present simultaneous XMM-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the centr…
A Search for an Optical Counterpart to the Gravitational-wave Event GW151226
Della Valle, M.; Sollerman, J.; Gal-Yam, A. +37 more
We present a search for an electromagnetic counterpart of the gravitational-wave source GW151226. Using the Pan-STARRS1 telescope we mapped out 290 square degrees in the optical I P1 filter, starting 11.5 hr after the LIGO information release and lasting for an additional 28 days. The first observations started 49.5 hr after the time of…
Lighting the Dark Molecular Gas: H2 as a Direct Tracer
Togi, Aditya; Smith, J. D. T.
Robust knowledge of molecular gas mass is critical for understanding star formation in galaxies. The {{{H}}}2 molecule does not emit efficiently in the cold interstellar medium, hence the molecular gas content of galaxies is typically inferred using indirect tracers. At low metallicity and in other extreme environments, these tracers ca…
DDO 68: A Flea with Smaller Fleas that on Him Prey
Aloisi, Alessandra; Cignoni, Michele; Sacchi, Elena +7 more
We present new photometry of the dwarf irregular galaxy DDO 68, one of the most metal-poor and least massive dwarfs, located in the Lynx-Cancer Void. The images were acquired with the Large Binocular Telescope in the g and r passbands and show unequivocally that DDO 68 has previously unknown stellar streams related to the accretion of at least two…
Characterizing X-Ray and Radio Emission in the Black Hole X-Ray Binary V404 Cygni during Quiescence
Gandhi, Poshak; Chakrabarty, Deepto; Walton, Dominic J. +17 more
We present results from multi-wavelength simultaneous X-ray and radio observations of the black hole X-ray binary V404 Cyg in quiescence. Our coverage with NuSTAR provides the very first opportunity to study the X-ray spectrum of V404 Cyg at energies above 10 keV. The unabsorbed broadband (0.3-30 keV) quiescent luminosity of the source is 8.9 × 10…
Herschel-resolved Outer Belts of Two-belt Debris Disks—Evidence of Icy Grains
Bryden, G.; Stapelfeldt, K. R.; Werner, M. W. +1 more
We present dual-band Herschel/PACS imaging for 59 main-sequence stars with known warm dust (T warm ∼ 200 K), characterized by Spitzer. Of 57 debris disks detected at Herschel wavelengths (70 and/or 100 and 160 µm), about half have spectral energy distributions (SEDs) that suggest two-ring disk architectures mirroring that of the a…