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High-Resolution Spectroscopy of X-Ray Quasars: Searching for the X-Ray Absorption from the Warm-Hot Intergalactic Medium
Canizares, Claude R.; Marshall, Herman L.; Fang, Taotao
We present a survey of six low- to moderate-redshift quasars with Chandra and XMM-Newton. The primary goal is to search for the narrow X-ray absorption lines produced by highly ionized metals in the warm-hot intergalactic medium. All the X-ray spectra can be fitted by a power law with the neutral hydrogen absorption method. The residuals that may …
Visible albedo of Mars' south polar cap: 2003 HST observations
Wolff, Michael J.; James, Philip B.; Bonev, Boncho P.
The martian south polar cap was observed with the High Resolution Camera on Hubble Space Telescope near the very favorable 2003 opposition. Well calibrated images taken at a number of wavelengths in visible and UV were used to measure the apparent Lambert albedos of two bright polar areas. These were corrected for the effects of atmospheric dust t…
Far-Infrared and Millimeter Continuum Studies of K Giants: α Bootis and α Tauri
McMurry, A. D.; Lim, Tanya; Schulz, Bernhard +5 more
We have imaged two normal, noncoronal, infrared-bright K giants, α Tau and α Boo, in the 1.4 and 2.8 mm continua using BIMA. These stars have been used as important absolute calibrators for several infrared satellites. Our goals are (1) to establish whether these stars radiate as simple photospheres or possess long-wavelength chromospheres and (2)…
Measured cosmological mass density in the WHIM: The solution to the ‘Missing Baryons’ problem
Elvis, Martin; Nicastro, Fabrizio; Fiore, Fabrizio +1 more
We review the current high-significance X-ray detections of Warm-Hot Intergalactic Medium (WHIM) filaments at z > 0 along the lines of sight to the two blazars Mrk 421 ( z = 0.03) and 1ES 1028 + 511 ( z = 0.361). For these WHIM filaments, we derive ionization corrections and, when possible, metallicity estimates. This allows us to obtain refine…
Mg II chromospheric radiative loss rates in cool active and quiet stars
Cardini, D.
The Mg II k emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the Mg II k line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric act…
Prospects in space-based gamma-ray astronomy
Knödlseder, J.
Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechani…
Characterizing the Adaptive Optics Off-Axis Point-Spread Function. II. Methods for Use in Laser Guide Star Observations
Faber, S. M.; Gates, E. L.; Macintosh, B. A. +2 more
Most current astronomical adaptive optics (AO) systems rely on the availability of a bright star to measure the distortion of the incoming wave front. Replacing the guide star with an artificial laser beacon alleviates this dependency on bright stars and therefore increases sky coverage, but it does not eliminate another serious problem for AO obs…
Near-Infrared Properties of Faint X-Ray Sources from NICMOS Imaging in the Chandra Deep Fields
Teplitz, Harry I.; McCarthy, Patrick J.; Malkan, Matthew A. +2 more
We measure the near-infrared properties of 42 X-ray-detected sources from the Chandra Deep Fields North and South, the majority of which lie within the NICMOS Hubble Deep Field-North and Ultra Deep Field. We detect all 42 Chandra sources with NICMOS, with 95% brighter than H160=24.5. We find that X-ray sources are most often in the brig…
Hubble Space Telescope Imaging of the Ultracompact Blue Dwarf Galaxy HS 0822+3542: An Assembling Galaxy in a Local Void?
Somerville, Rachel S.; Windhorst, Rogier A.; Vacca, William D. +2 more
We present deep U-band, narrow V-band, and I-band images and photometry of the ultracompact blue dwarf galaxy HS 0822+3542 obtained with the Advanced Camera for Surveys/High Resolution Channel of the Hubble Space Telescope. This object is also extremely metal-poor [12+log(O/H)=7.45] and resides in a nearby void. The images resolve it into two phys…
Signs of warm-hot intergalactic medium in the soft X-ray background
Sołtan, A. M.; Freyberg, M. J.; Hasinger, G.
Small angular scale structure of the soft X-ray background correlated with the galaxy distribution is investigated. An extensive data sample from the ROSAT and XMM-Newton archives are used. Excess emission below 1 keV extending up to at least several hundred kpc around galaxies is detected. The relative amplitude of the excess emission in the 0.3-…