Engineering topics

Vigroux, L.

Publications and source records attributed to Vigroux, L..

4 records

NASA NTRS1990

The effects of stellar age and metallicity on the infrared emission in the Magellanic Clouds

Infrared Astronomical Satellite (IRAS) maps of the Magellanic Clouds smoothed to a 5-min angular resolution and young star catalogs are used to study the effects of stellar age and metallicity on the infrared emission of these galaxies. The construction of the stellar catalog is described, along with the conversion from the observational to the theoretical temperature-luminosity diagram and the derivation of stellar ages. The infrared color-color diagram of the Clouds is investigated, and the effect of stellar age on their infrared emission is investigated. The effects of the UV radiation field and of the metallicity on the infrared emission are also considered with emphasis on the influence of such parameters as gas-to-dust ratio on the infrared colors. It is shown that the far-infrared fluxes of individual pixels in the Clouds' maps follow the same behavior as the integrated emission of normal galaxies in the IRAS color-color diagram and that the precise position of a particular pixel depends on the age of the youngest star in that pixel.

Sauvage, M.↗

NASA NTRS1986

IC 3475 - A stripped dwarf galaxy in the Virgo cluster

B and R CCD and H I observations of the Virgo dwarf galaxy IC 3475 were obtained. The galaxy is very large, having a diameter of about 10 kpc; its hydrogen content is at least 60 times smaller than that of a normal dwarf irregular galaxy; and the galaxy shows a central bar structure with knots and inclusions scattered throughout its body but with the majority in the bar region. The results support the hypothesis that IC 3475 is a dwarf irregular galaxy that has been stripped of its neutral gas.

Vigroux, L.↗

NASA NTRS1984

Temperature and elemental abundances in the Abell cluster A576 derived from X-ray observations

Results of the Einstein Solid State Spectrometer (SSS) observations of the central region of Abell 576 combined with HEAO 1 spectra of the total cluster are reported. Line emission due to Fe, Si, and S from a hot plasma in the central region of the object are detected. Abundances roughly one-half of the solar value are derived for these elements. The total cluster spectrum is well fitted by a thermal bremsstrahlung model with a temperature of 4 +3.5 or -1.4 x 10 to the 7th K. This temperature is in conflict with the SSS temperature determination for the center of the cluster. This difference can be explained if cooling takes place in the central part of the cluster, or if the X-ray emission in the center is dominated by the emission of a single galaxy.

Rothenflug, R.↗

NASA NTRS1983

Temperature and elemental abundances in the Abell cluster A 576 derived from X-ray observations

Results of Einstein solid state spectrometer observations of the central region of Abell 576 combined with HEAO 1 spectra of the total cluster are given. Line emission was detected due to Fe, Si, and S from a hot plasma in the central region. The temperature of the total cluster spectrum may be in conflict with the central temperature. This difference can be explained either if cooling takes place in the center, or if part of the measured emission is due to individual galaxies. If the X-ray emission comes from the intergalactic gas only, there is some difficulty in producing all the silicon observed in the galaxies of A 576.

Rothenflug, R.↗