GeminiFocus October 2015 | Page 12

Figure 4. Continuum-subtracted TEXES spectrum (black) and dominant “hot” model fit (blue), which yields the temperature (450 K) and location (0.3 AU) of the emitting water vapor. A “warm” component (red) is required to account for additional measurements at longer wavelengths. The sum of the models is plotted in gray. called “transition disks” in showing evidence for water; yet by later stages of evolution, as young stars with disks, water vapor emission is common. The inner ring of DoAr 44 may be replenished by material from the outer disk, accounting for the large water content it maintains compared with similar objects. Alternatively, planets may affect the chemistry in this region where terrestrial planets develop. The warm (450 K) water arises in the inner ring, appearing in emission at mid-infrared wavelengths (Figure 4). The data were obtained at a spectral resolution R ~ 80,000 using the Texas Echelon Cross Echelle Spectrograph (TEXES), a visitor instrument on the 10 GeminiFocus Gemini North telescope. Colette Salyk (National Optical Astronomy Observatory and Vassar College) and collaborators used the kinematic characteristics of the spectrally resolved emission to determine the location of its origin, at 0.3 AU. Avoiding destruction of water molecules in this region close to the stellar source requires material in the region — either gas or dust — as protection against the star’s strong radiation. The paper will appear in The Astrophysical Journal Letters and a preprint is now available. Nancy A. Levenson is Deputy Director and Head of Science at Gemini Observatory and can be reached at: [email protected] October 2015