Search Publications
Nuclear Activity and Massive Star Formation in the Low-Luminosity Active Galactic Nucleus NGC 4303: Chandra X-Ray Observations
Mas-Hesse, J. M.; Colina, L.; Guainazzi, M. +4 more
We present evidence of the coexistence of either an AGN or an ultraluminous X-ray source, together with a young superstellar cluster, in the central 3 pc of NGC 4303. The galaxy contains a low-luminosity AGN and hosts a number of starburst regions in a circumnuclear spiral, as well as in the nucleus itself. A high spatial resolution Chandra image …
The Long-Term Evolution of AR 7978: Testing Coronal Heating Models
Klimchuk, J. A.; Mandrini, C. H.; van Driel-Gesztelyi, L. +2 more
We derive the dependence of the mean coronal heating rate on the magnetic flux density. Our results are based on a previous study of the plasma parameters and the magnetic flux density (B) in the active region NOAA 7978 from its birth to its decay, throughout five solar rotations using the Solar and Heliospheric Observatory Michelson Doppler Image…
Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F-Coronal Brightness
Kahler, S. W.; Ragot, B. R.
The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Rsolar. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of…
The Mass, Baryonic Fraction, and X-Ray Temperature of the Luminous, High-Redshift Cluster of Galaxies MS 0451.6-0305
Donahue, Megan; Hughes, John P.; Gaskin, Jessica A. +3 more
We present new Chandra X-ray observations of the luminous and cosmologically significant X-ray cluster of galaxies, MS 0451.6-0305, at z=0.5386. Spectral imaging data for the cluster are consistent with an isothermal cluster of (10.0-10.6)+/-1.6 keV, with an intracluster Fe abundance of (0.32-0.40)+/-0.13 solar. The systematic uncertainties, arisi…
A Survey of 557 GHz Water Vapor Emission in the NGC 1333 Molecular Cloud
Bergin, Edwin A.; Kaufman, Michael J.; Melnick, Gary J. +2 more
Using NASA's Submillimeter Wave Astronomy Satellite (SWAS), we have examined the production of water in quiescent and shocked molecular gas through a survey of the 556.936 GHz 110-101 transition of ortho-H2O in the NGC 1333 molecular core. These observations reveal broad emission lines associated with the IRAS 2, I…
Ks Number Counts in the Groth and Coppi Fields
Cardiel, Nicolás; Balcells, Marc; Gallego, Jesús +5 more
We have used William Herschel Telescope/INGRID Ks images on two high-latitude fields, the Coppi and Groth strips, to obtain galaxy number counts over ~180 arcmin2, to a depth of Ks~21.0. Detection efficiency corrections as a function of object size have been calculated on each pointing. We have used a signal-to-noi…
A Quadruple-Phase Strong Mg II Absorber at z ~ 0.9902 toward PG 1634+706
Charlton, Jane C.; Churchill, Christopher W.; Bond, Nicholas A. +2 more
The z=0.9902 system along the quasar PG 1634+706 line of sight is a strong Mg II absorber [Wr(λ2796)>0.3 Å] with only weak C IV absorption (it is ``C IV-deficient''). To study this system, we used high-resolution spectra from both the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) and the Keck I telescope High Res…
Test for Alfvén Wave Signatures in a Solar Coronal Hole
Moran, Thomas G.
Using spectral line observations to study minor ion motions in a solar coronal hole, a test was made for the presence of Alfvén waves. From this we conclude that the Alfvén wave flux into the upper portion of the hole is not significant. The SOHO/SUMER ultraviolet spectrograph was used to observe 22 coronal ions with masses ranging from 14mH<…
New Laboratory Spectra of Isolated β-SiC Nanoparticles: Comparison with Spectra Taken by the Infrared Space Observatory
Mutschke, H.; Henning, Th.; Klein, R. +1 more
We present new laboratory infrared spectra of matrix-isolated β-SiC nanoparticles, which perfectly match the band profile of the 11+ µm feature observed in carbon stars. The new laboratory spectra differ in the shape of the band profile from former measurements of SiC nanoparticles thanks to the matrix-isolation technique which allows to obt…
Diffuse X-Ray Emission from M101
Mukai, K.; Kuntz, K. D.; Snowden, S. L. +1 more
The total 0.45-1.0 keV luminosity of M101 is 3.2×1039 ergs s-1, of which 2.3×1039 ergs s-1 is due to diffuse emission. (Chandra observes only ~60% of the diffuse emission observed by ROSAT because of its superior point-source detection.) Of the diffuse emission seen by Chandra, no more than 6% can be due…