Search Publications
The topology of a mixed-polarity potential field, and inferences for the heating of the quiet solar corona
Title, Alan M.; Schrijver, Carolus J.
We study the statistical properties of the connectivity of the corona over the quiet Sun by analyzing the potential magnetic field above the central area of source planes sprinkled randomly with some 300 magnetic monopoles each. We find that the field is generally more complex than one might infer from a study of the field within the source plane …
Solar p-modes from 1979 days of the GOLF experiment
Grec, G.; Salabert, D.; Gelly, B. +5 more
With the GOLF instrument onboard the SoHO observatory, 1979 days of full-disc Doppler velocity observations have been compiled into a study of p-mode properties. We develop a multi-step iterative method (MSIM) algorithm to access all p-mode parameters while minimizing any perturbating effect or cross-talk between parameters during their determinat…
On the Column Density of AGN Outflows: The Case of NGC 5548
Korista, Kirk T.; Arav, Nahum; de Kool, Martijn
We reanalyze the Hubble Space Telescope high-resolution spectroscopic data of the intrinsic absorber in NGC 5548 and find that the C IV absorption column density is at least 4 times larger than previously determined. This increase arises from accounting for the kinematical nature of the absorber and from our conclusion that the outflow does not co…
A Uniform Analysis of the Lyα Forest at z = 0-5. III. Hubble Space Telescope Faint Object Spectrograph Spectral Atlas
Bechtold, Jill; Tran, Kim-Vy; Dobrzycki, Adam +5 more
We analyzed the absorption line spectra of all quasars observed with the high-resolution gratings of the Faint Object Spectrograph on board the Hubble Space Telescope. We examined 788 spectra for 334 quasars and present line lists and identifications of absorption lines in the spectra of 271 of them. Analysis of the statistics of the Lyα and metal…
The Microjansky Sky at 8.4 GHz
Fomalont, E. B.; Windhorst, R. A.; Richards, E. A. +2 more
We present the results from two deep radio integrations at 8.4 GHz using the Very Large Array. One of the fields, at 13h, +43° (SA 13 field), has an rms noise level of 1.49 µJy and is the deepest radio image yet made. Thirty-four sources in a complete sample were detected above 7.5 µJy, and 25 are optically identified to a l…
Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. I. Method and a Preliminary Measurement for Fornax
Minniti, Dante; Mateo, Mario; Piatek, Slawomir +6 more
This article presents and discusses a method for measuring the proper motions of the Galactic dwarf spheroidal galaxies using images taken with the Hubble Space Telescope. The method involves fitting an effective point-spread function to the image of a star or quasi-stellar object to determine its centroid with an accuracy of about 0.005 pixels (0…
Molecular Gas and Nuclear Activity in Ultraluminous Infrared Galaxies with Double Nuclei
Sanders, D. B.; Surace, J. A.; Evans, A. S. +1 more
High-resolution CO(1-->0) observations of five ultraluminous infrared galaxies [ULIGs; LIR(8-1000µm)>~1012 Lsolar] with double nuclei are analyzed. These sources constitute a complete subset of local ULIGs expected to be in an intermediate stage of merging and are selected to have projected nuclear sepa…
Faint stars in the Ursa Minor dwarf spheroidal galaxy: implications for the low-mass stellar initial mass function at high redshift
Wyse, Rosemary F. G.; Gilmore, Gerard; Gallagher, John S., III +4 more
The stellar initial mass function at high redshift is an important defining property of the first stellar systems to form and may also play a role in various dark matter problems. We here determine the faint stellar luminosity function in an apparently dark-matter-dominated external galaxy in which the stars formed at high redshift. The Ursa Minor…
Chandra Observations of Markarian 273: Unveiling the Central Active Galactic Nucleus and the Extended Hot Gas Halo
Xia, X. Y.; Xue, S. J.; Mao, S. +3 more
We report X-ray observations of the field containing the ultraluminous IRAS galaxy Mrk 273. The data were obtained using the Advanced CCD Imaging Spectrometer S3 instrument on board Chandra. The high-resolution X-ray image for the first time reveals a compact hard X-ray nucleus in Mrk 273. Its position is coincident with the northern nucleus ident…
Resolving subdwarf B stars in binaries by HST imaging
Heber, U.; Green, E. M.; Thejll, P. +2 more
The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little success. We have carried out a small survey of spectroscopic binary candidates (19 systems consisting of an sdB star and late type companion) with the Plan…