Near Infrared Studies of Reflection Nebulae

Near infrared studies have been made of the extended emission from, and stellar clusters within, three visual reflection nebulae, NGC 7023, 2023, and 2068. The extended emission from each nebula consists of a smooth continuum from 1.25 to 4.8 μm, which can be described by a greybody with a color temperature of ~1000 K, and strong emission features at 3.3 and 3.4 μm. The spectrum is the same in all three sources, and is independent of position over regions 0.4-0.9 pc in diameter within each source. The 2.2 μm surface brightness distributions in NGC 7023 and 2023 agree well with the distributions of visual reflected light. The continuum emission cannot be explained by free-free emission, reflected light, fluorescent processes, field stars, or thermal emission from grains in equilibrium with the stellar radiation field. A model is proposed in which the extended emission is due to thermal emission from very small grains (radius ~10 Å) which are briefly heated to ~1000 K by absorption of an ultraviolet photon. This model explains the agreement between near infrared and visual surface brightness distributions, and the constancy of the energy distribution with offset from the central stars. The numbers of 10 Å sized grains required by the observations are in agreement with the numbers expected from an extrapolation of the grain size distribution of Mathis, Rumpl, and Nordsieck (1977) to smaller grain sizes. Clusters of young stars found associated with the reflection nebulae NGC 7023, 2023, and 2068 have also been studied at near infrared wavelengths. At least 30-60 % of the stars found at 2.2 μm are pre-main sequence objects, as indicated by their infrared excesses, hydrogen line emission, or irregular variability. The spatial distributions and observed luminosity functions of these young open clusters are derived, and the inferred mass function and star formation efficiencies are discussed.</p

Training of Instrumentalists and Development of New Technologies on SOFIA

This white paper is submitted to the Astronomy and Astrophysics 2010 Decadal Survey (Astro2010)1 Committee on the State of the Profession to emphasize the potential of the Stratospheric Observatory for Infrared Astronomy (SOFIA) to contribute to the training of instrumentalists and observers, and to related technology developments. This potential goes beyond the primary mission of SOFIA, which is to carry out unique, high priority astronomical research. SOFIA is a Boeing 747SP aircraft with a 2.5 meter telescope. It will enable astronomical observations anywhere, any time, and at most wavelengths between 0.3 microns and 1.6 mm not accessible from ground-based observatories. These attributes, accruing from the mobility and flight altitude of SOFIA, guarantee a wealth of scientific return. Its instrument teams (nine in the first generation) and guest investigators will do suborbital astronomy in a shirt-sleeve environment. The project will invest $10M per year in science instrument development over a lifetime of 20 years. This, frequent flight opportunities, and operation that enables rapid changes of science instruments and hands-on in-flight access to the instruments, assure a unique and extensive potential - both for training young instrumentalists and for encouraging and deploying nascent technologies. Novel instruments covering optical, infrared, and submillimeter bands can be developed for and tested on SOFIA by their developers (including apprentices) for their own observations and for those of guest observers, to validate technologies and maximize observational effectiveness.Comment: 10 pages, no figures, White Paper for Astro 2010 Survey Committee on State of the Professio