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In this review we re-evaluate our observational and theoretical understanding of the chemical evolution of protoplanetary disks. We discuss how improved observational capabilities have enabled the detection of numerous molecules exposing an active disk chemistry that appears to be in disequilibrium. We outline the primary facets of static and dynamical(More)
We present a comprehensive study of the physical and chemical conditions along the TMC-1 ridge. Temperatures were estimated from observations of CH3CCH, NH3, and CO. Densities were obtained from a multitransition study of HC3N. The values of the density and temperature allow column densities for 13 molecular species to be estimated from statistical(More)
We report the results of spectroscopic mapping observations carried out toward small (1 ′ × 1 ′) regions within the supernova remnants W44, W28, IC443, and 3C391 using the Infrared Spectrograph of the Spitzer Space Telescope. These observations, covering the 5.2 − 37 µm spectral region, have led to the detection of a total of 15 fine structure transitions(More)
We report the results of spectroscopic mapping observations carried out toward the Herbig-Haro objects HH7–11 and HH54 over the 5.2 − 37 µm region using the Infrared Spectrograph of the Spitzer Space Telescope. These observations have led to the detection and mapping of the S(0) – S(7) pure rotational lines of molecular hydrogen, together with emissions in(More)
We present an observational and theoretical study of the ionization fraction in several massive cores located in regions that are currently forming stellar clusters. Maps of the emission from the J = 1 → 0 transitions of C 18 O, DCO + , N 2 H + , and H 13 CO + , as well as the J = 2 → 1 and J = 3 → 2 transitions of CS, were obtained for each core. Core(More)
For decades, the source of Earth's volatiles, especially water with a deuterium-to-hydrogen ratio (D/H) of (1.558 ± 0.001) × 10(-4), has been a subject of debate. The similarity of Earth's bulk composition to that of meteorites known as enstatite chondrites suggests a dry proto-Earth with subsequent delivery of volatiles by local accretion or impacts of(More)
We show how molecular clouds in the solar neighborhood might be formed and produce stars rapidly enough to explain stellar population ages, building on results from numerical simulations of the turbulent interstellar medium and general considerations of molecular gas formation. Observations of both star-forming regions and young, gas-free stellar(More)
Context. According to traditional gas-phase chemical models, O 2 should be abundant in molecular clouds, but until recently, attempts to detect interstellar O 2 line emission with ground-and space-based observatories have failed. Aims. Following the multi-line detections of O 2 with low abundances in the Orion and ρ Oph A molecular clouds with Herschel, it(More)
We report the detection of interstellar hydrogen deuteride (HD) toward the supernova remnant IC443, and the tentative detection of HD toward the Herbig Haro objects HH54 and HH7 and the star forming region GGD37 (Cepheus A West). Our detections are based upon spectral line mapping observations of the R(3) and R(4) rotational lines of HD, at rest wavelengths(More)