reflection nebulae (rns) are objects of special interest because they provide an opportunity to explore the interaction of a single star with a region of high density ism.they are bright enough to permit a detailed spectroscopy of the emission by is dust and gas . in addition, the characteristics of the stellar radiation incident can vary from object to object (o/b to m stars), allowing tests of specific models for the excitation of different is species. our proposal will use iso to study a sample of rns illuminated with widely varying temperatures. we propose to obtain: - complete 2.5-200 um spectra for a subset of rns with varying stellar temperature. this is the heart of the proposal. - 3-200 um broad band energy distributions of the emission for all rns. - measurement of the gas heating efficiency for a subset of rns, by varying(i) the irradiation spectra (o/b to m stars) and (ii) the flux intensity (different distances from the star in a given rn). specifically, we want to: - confirm or deny the pah hypothesis;if confirmed, make a more specific identification of the molecular species and correlate their ionization and dehydrogenation states with the stellar irradiation. - search for c60 molecules or ions. - look for spectral features that could identify the particles emitting by temperature fluctuations in the 20-100 um range, because, presently, we know nothing on their chemical nature. - determine whether there is a cut-off in the exciting star temperature underwhich the gas heating efficiency drops, as expected if the heating mechanism is photoelectric effect.
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1999, Reflection Nebulae Part 3 Photometry And Full Range Spectroscopy Part 3, 1.0, European Space Agency, https://doi.org/10.5270/esa-ix92qwr
