Search Publications
High-dispersion Spectrum of the Halo Planetary Nebula DdDm 1
Izumiura, Hideyuki; Otsuka, Masaaki; Hyung, Siek +2 more
Using the High Dispersion Spectrograph (HDS) at the Subaru Telescope, we secured the high-resolution line spectra in the 3600-7500 Å wavelength range of the Galactic halo planetary nebula DdDm 1. We also analyzed the Hubble Space Telescope Faint Object Spectrograph data in the 1200-6730 Å wavelength range. The diagnostic results indicate the elect…
Grain Growth and Global Structure of the Protoplanetary Disk Associated with the Mature Classical T Tauri Star, PDS 66
Pascucci, Ilaria; Schneider, Glenn; Hines, Dean C. +4 more
We present Australia Telescope Compact Array interferometric observations of the old (13 Myr), nearby (86 pc) classical T Tauri star (cTTS), PDS 66. Unresolved 3 and 12 mm continuum emission is detected toward PDS 66, and upper limits are derived for the 3 and 6 cm flux densities. The millimeter-wave data show a spectral slope flatter than that ex…
Mapping the Structure of the Corona Using Fourier Backprojection Tomography
Morgan, Huw; Habbal, Shadia Rifai; Lugaz, Noé
Estimating the structure, or density distribution, of the solar corona from a set of two-dimensional white-light images made by coronagraphs is a critical challenge in coronal physics. This work describes new data-analysis procedures which are used to create global maps of the coronal structure at heights where the corona becomes approximately rad…
Improved Constraints on the Gravitational Lens Q0957+561. I. Weak Lensing
Schrabback, T.; Keeton, C. R.; Bernstein, G. M. +2 more
Attempts to constrain the Hubble constant using the strong gravitational lens system Q0957+561 are limited by systematic uncertainties in the mass model, since the time delay is known very precisely. One important systematic effect is the mass-sheet degeneracy, which arises because strong lens modeling cannot constrain the presence or absence of a…
Constraints on the Intracluster Dust Emission in the Coma Cluster of Galaxies
Onaka, Takashi; Kaneda, Hidehiro; Kitayama, Tetsu +7 more
We have undertaken a search for the infrared emission from the intracluster dust in the Coma cluster of galaxies by the Multiband Imaging Photometer for Spitzer. Our observations yield the deepest mid and far-infrared images of a galaxy cluster ever achieved. In each of the three bands, we have not detected a signature of the central excess compon…
The "Main Sequence" of Explosive Solar Active Regions: Discovery and Interpretation
Moore, Ronald L.; Gary, G. Allen; Falconer, David A. +1 more
We examine the location and distribution of the production of coronal mass ejections (CMEs) and major flares by sunspot active regions in the phase space of two whole-active-region magnetic quantities measured from 1897 SOHO/MDI magnetograms. These magnetograms track the evolution of 44 active regions across the central disk of radius 0.5 R S…
X-ray Sources and their Optical Counterparts in the Galactic Globular Cluster M12 (NGC 6218)
Anderson, Scott F.; Kong, Albert K. H.; Verbunt, Frank +4 more
We study a Chandra X-ray Observatory ACIS-S observation of the Galactic globular cluster M12. With a 26 ks exposure time, we detect six X-ray sources inside the half-mass radius (2farcm16) of which two are inside the core radius (0farcm72) of the cluster. If we assume that these sources are all associated with globular cluster M12, the luminosity …
Chandra Observations of Nuclear X-Ray Emission from Low Surface Brightness Galaxies
Reynolds, C. S.; Das, M.; Vogel, S. N. +2 more
We present Chandra detections of X-ray emission from the active galactic nuclei (AGN) in two giant low surface brightness (LSB) galaxies, UGC 2936 and UGC 1455. Their X-ray luminosities are 1.8 × 1042 ergs s-1 and 1.1 × 1040 ergs s-1 respectively. Of the two galaxies, UGC 2936 is radio loud. Together wit…
Reconnection Electric Field and Hardness of X-Ray Emission of Solar Flares
Liu, Chang; Wang, Haimin
Magnetic reconnection is believed to be the prime mechanism that triggers solar flares and accelerates electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons, manifests the successive reconnection that takes place higher up in the corona. Meanwhile, downward traveling en…
Overdensities of Galaxies at z ~ 3.7 in Chandra Deep Field-South
Im, Myungshin; Kang, Eugene
We report the discovery of possible overdensities of galaxies at z ~ 3.7 in Chandra Deep Field-South (CDF-S). These overdensities are identified from a photometric redshift-selected sample and a BVz-selected sample. One overdensity is identified in the proximity of two active galactic nuclei and Lyman break galaxies at z = 3.66 and z = 3.70 at 7σ …