Infrared Space Observatory Satellite Research Articles

Photoelectric Heating and [Cii] Cooling in Translucent Clouds: Results for Cloud Models Based on Simulations of Compressible Magnetohydrodynamic Turbulence

Far-ultraviolet (FUV) photons expel electrons from interstellar dust grains and the excess kinetic energy of the electrons is converted into gas thermal energy through collisions. This photoelectric heating is believed to be the main heating mechanism in cool H I clouds. The heating rate cannot be directly measured, but it can be estimated through observations of the [C II] line emission, since this is believed to be the main coolant in regions where the photoelectric effect dominates the heating. Furthermore, the comparison of the [C II] emission with the far-infrared (FIR) emission allows us to constrain the efficiency of the photoelectric heating using model calculations that take into account the strength of the radiation field. Recent [C II] observations carried out with the Infrared Space Observatory satellite have made this study possible.

ISO and stellar evolution

Mid- and far-infrared spectroscopy and photometry for many newborn and dying stars, which very often are hidden in thick and opaque clouds, has become possible with the advent of the Infrared Space Observatory (ISO). In this review I present the most important results obtained with the Infrared Space Observatory as far as the initial and final stages of stellar evolution are concerned. These achievements are based on observations made by all four instruments on board the ISO satellite, with emphasis on data from the spectrometers.

10 Hygiea: ISO Infrared Observations

Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8–11.6 and 7–45 μm, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo–physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated.

Cygnus X-3 with ISO: investigating the wind

Cygnus X-3 with ISO: investigating the wind

A program to search for dyson spheres with the infrared space observatory

A contribution to the Search for Extraterrestrial Intelligence is made by searching for astro-engineering products (Dyson spheres) of advanced civilizations using the Infrared Space Observatory (ISO) satellite. ISO is the European infrared astronomy mission covering the wavelength region of 2–240 microns. A SETI program using 1 h 18 m total spacecraft time has been established and will be described. The program will be the first attempt to perform active SETI in the infrared using a spacecraft. A photometric survey, covering 3–60 microns, of several old main sequence stars will be performed in order to assess infrared excesses compatible with the presence of large astro-engineering products like Dyson spheres that emit a blackbody temperature of several hundred K. This survey shall identify candidates for Dyson spheres. In addition, a few objects which are known to show infrared excesses in the 12 or 25 micron IRAS measurements are considered for a detailed photometric investigation. The usage of the ISO satellite is crucial for the success of the program as only ISO currently offers, with its infrared photometer, the high sensitivity that is needed to detect the radiation of cold artificial structures superimposed on the several thousand K blackbody background spectrum of the host star.

A Self‐consistent Photoionization–Dust Continuum–Molecular Line Transfer Model of NGC 7027

A model to simulate the entire spectrum (1000 Å to 1 cm) of the high-excitation young planetary nebula NGC 7027 is presented. The ionized, dust, and molecular components of the object are modeled using geometric parameters obtained from visible, radio, infrared, and CO data. The physical processes considered include recombination lines of H and He, collisional excited lines of metals, bf and ff continuum radiations, two-photon radiation, dust continuum radiation, and molecular rotational and vibrational transitions. The dust component is assumed to be heated by a combination of direct starlight and the line and continuum radiation from the ionized nebula. The molecular component of the nebula is coupled to the dust component through the stimulated absorption of the dust continuum radiation. Specifically, we compare the predicted fluxes of the CO rotational lines and the 179.5 μm water rotational line to those observed by the Infrared Space Observatory satellite. From the observed ratio of these lines, we derived a gas phase water-to-H2 abundance ratio of 3.2 × 10-7 assuming that the water is uniformly mixed with the CO.

A self-consistent photoionization-dust continuum-molecular line transfer model of NGC7027

A model to simulate the entire spectrum (1000 Å to 1 cm) of the high-excitation young planetary nebula NGC 7027 is presented. The ionized, dust, and molecular components of the object are modeled using geometric parameters obtained from visible, radio, infrared, and CO data. The physical processes considered include recombination lines of H and He, collisional excited lines of metals, bf and ff continuum radiations, two-photon radiation, dust continuum radiation, and molecular rotational and vibrational transitions. The dust component is assumed to be heated by a combination of direct starlight and the line and continuum radiation from the ionized nebula. The molecular component of the nebula is coupled to the dust component through the stimulated absorption of the dust continuum radiation. Specifically, we compare the predicted fluxes of the CO rotational lines and the 179.5 μm water rotational line to those observed by the Infrared Space Observatory satellite (Liu et al. 1996, A&A in press).

Far-infrared imaging, polarimetry, and spectrophotometry on the Infrared Space Observatory

The Infrared Space Observatory (ISO) photometer is one of four instruments on board the European Space Agency ISO satellite scheduled for launch in September 1995. It covers the wavelength range 2.5 to 240 μm with wide and narrow spectral bands. Diffraction-limited observations as well as wide-beam measurements of faint extended sources are possible. Polarimetric observations can be made over the whole wavelength range. The minimal detectable flux is ~10 mJy. The astronomical areas to be addressed range from solar system objects to cosmology.