Search Publications
Excitation of magnetosonic waves in the terrestrial magnetosphere: Particle-in-cell simulations
Gary, S. Peter; Liu, Kaijun; Winske, Dan
Two-dimensional electromagnetic particle-in-cell simulations are performed to study the temporal development of an ion Bernstein instability driven by a proton velocity distribution with positive slope in the perpendicular velocity distribution fp(v$\perp$), where $\perp$ denotes directions perpendicular to the background mag…
Constraining the role of star cluster mergers in nuclear cluster formation: simulations confront integral-field data
Quinn, Thomas R.; Cappellari, Michele; Seth, Anil +2 more
We present observations and dynamical models of the stellar nuclear clusters (NCs) at the centres of NGC 4244 and M33. We then compare these to an extensive set of simulations testing the importance of purely stellar dynamical mergers on the formation and growth of NCs. Mergers of star clusters are able to produce a wide variety of observed proper…
AEGIS: The Morphologies of Green Galaxies at 0.4 < z < 1.2
Moustakas, John; Salim, Samir; Coil, Alison L. +3 more
We present quantitative morphologies of ~300 galaxies in the optically defined green valley at 0.4 < z < 1.2, in order to constrain the mechanism(s) responsible for quenching star formation in the bulk of this population. The sample is selected from galaxies in the All-Wavelength Extended Groth Strip International Survey (AEGIS). While the g…
Kinematic signature of an intermediate-mass black hole in the globular cluster NGC 6388
Kissler-Patig, M.; de Zeeuw, P. T.; Lützgendorf, N. +4 more
Context. Intermediate-mass black holes (IMBHs) are of interest in a wide range of astrophysical fields. In particular, the possibility of finding them at the centers of globular clusters has recently drawn attention. IMBHs became detectable since the quality of observational data sets, particularly those obtained with HST and with high resolution …
On the origin of radio loudness in active galactic nuclei and its relationship with the properties of the central supermassive black hole
Marconi, Alessandro; Chiaberge, Marco
We investigate the relationship between the mass of central supermassive black holes (SMBHs) and the radio loudness of active galactic nuclei (AGNs). We use the most recent calibrations to derive 'virial' BH masses for samples of radio-loud quasi-stellar objects (QSOs) for which relatively small masses (MBH < 108 M⊙
Spatially resolved optical integral field unit spectroscopy of the inner superwind of NGC 253
Smith, L. J.; Gallagher, J. S., III; Westmoquette, M. S.
We present optical integral field unit (IFU) observations (VLT/VIMOS-IFU and WIYN/SparsePak), and associated archival deep Hα imaging (MPG/ESO 2.2 m WFI), of the nearby starburst galaxy NGC 253. With VIMOS we observed the nuclear region and southern superwind outflow in detail with five pointings, and with the WIYN/SparsePak IFU we observed two pa…
Are C60 Molecules Detectable in Circumstellar Shells of R Coronae Borealis Stars?
Lambert, D. L.; García-Hernández, D. A.; Kameswara Rao, N.
The hydrogen-poor, helium-rich, and carbon-rich character of the gas around R Coronae Borealis (RCB) stars has been suggested to be a site for formation of C60 molecules. This suggestion is not supported by observations reported here showing that infrared transitions of C60 are not seen in a large sample of RCB stars observed…
Dispersion relation analysis of solar wind turbulence
Glassmeier, K. -H.; Narita, Y.; Motschmann, U. +2 more
Frequency versus wave number diagram of turbulent magnetic fluctuations in the solar wind was determined for the first time in the wide range over three decades using four Cluster spacecraft. Almost all of the identified waves propagate quasi-perpendicular to the mean magnetic field at various phase speeds, accompanied by a transition from the dom…
Supermassive Black Hole Growth in Starburst Galaxies over Cosmic Time: Constraints from the Deepest Chandra Fields
Lehmer, B. D.; Alexander, D. M.; Papovich, C. +5 more
We present an analysis of deep multiwavelength data for z ≈ 0.3-3 starburst galaxies selected by their 70 µm emission in the Extended-Chandra Deep Field-South and Extended Groth Strip. We identify active galactic nuclei (AGNs) in these infrared sources through their X-ray emission and quantify the fraction that host an AGN. We find that the …
Stellar Activity in the Broadband Ultraviolet
Findeisen, K.; Hillenbrand, L.; Soderblom, D.
The completion of the GALEX All-Sky Survey in the ultraviolet allows activity measurements to be acquired for many more stars than is possible with the limited sensitivity of ROSAT or the limited sky coverage of Chandra, XMM, or spectroscopic surveys for line emission in the optical or ultraviolet. We have explored the use of GALEX photometry as a…