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  1. Abstract

    Gas mass is a fundamental quantity of protoplanetary disks that directly relates to their ability to form planets. Because we are unable to observe the bulk H2content of disks directly, we rely on indirect tracers to provide quantitative mass estimates. Current estimates for the gas masses of the observed disk population in the Lupus star-forming region are based on measurements of isotopologues of CO. However, without additional constraints, the degeneracy between H2mass and the elemental composition of the gas leads to large uncertainties in such estimates. Here, we explore the gas compositions of seven disks from the Lupus sample representing a range of CO-to-dust ratios. With Band 6 and 7 ALMA observations, we measure line emission for HCO+, HCN, and N2H+. We find a tentative correlation among the line fluxes for these three molecular species across the sample, but no correlation with13CO or submillimeter continuum fluxes. For the three disks where N2H+is detected, we find that a combination of high disk gas masses and subinterstellar C/H and O/H are needed to reproduce the observed values. We find increases of ∼10–100× previous mass estimates are required to match the observed line fluxes. This work highlights how multimolecular studies are essentialmore »for constraining the physical and chemical properties of the gas in populations of protoplanetary disks, and that CO isotopologues alone are not sufficient for determining the mass of many observed disks.

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  2. null (Ed.)
    This article summarizes research conducted in the Sahuaripa and Bacanora valleys of Sonora, Mexico. Located in the Serrana culture area of the Sierra Madre Occidental, data from this region speaks to several prevalent debates regarding the precolonial era of Northwest Mexico. Radiocarbon dates support demographic reconstructions for sizeable populations post-1000 AD; a time when other regions of the Northwest/Southwest (NW/SW) experienced significant demographic changes. Material cultural patterns reflect substantial local and regional connections with neighboring Río Sonora groups and Huatabampo. Recovered polychrome ceramics demonstrate long-distance connections with Casas Grandes, and obsidian data reflect connections to the Sonora and other neighboring valleys. These data indicate the Sahuaripa Valley participated in a corridor of exchange, which potentially included interaction between Casas Grandes and West Mexico. These observations are relevant to macro-scale patterns of interaction in the late-precolonial NW/SW. Este trabajo resume las investigaciones realizadas en los valles de Sahuaripa y Bacanora de Sonora, México. Estos valles están localizados en el área cultural Serrana de la Sierra Madre Occidental. La información sirve para entender las interacciones culturales en la época prehispánica del noroeste de México. Los fechamientos indican que existían poblaciones considerables posteriores al año 1000 d. C. periodo histórico donde ocurrieron cambiosmore »demográficos significativos. Los materiales reflejan conexiones locales y regionales con los grupos de Río Sonora y Huatabampo. Las cerámicas policromadas demuestran vínculos culturales con Casas Grandes, y los datos de obsidiana reflejan su interacción con el valle de Sonora así como con otras regiones. Los datos indican que el valle de Sahuaripa sirvió como un corredor de intercambio, que incluía Casas Grandes y al occidente de México. Estas observaciones son relevantes para entender los patrones de interacción de mayor escala en el NW/SW.« less
  3. Abstract In this paper, we present the first results from a CARMA high-resolution 12 CO(1-0), 13 CO(1-0), and C 18 O(1-0) molecular line survey of the North America and Pelican (NAP) Nebulae. CARMA observations have been combined with single-dish data from the Purple Mountain 13.7 m telescope, to add short spacings and to produce high-dynamic-range images. We find that the molecular gas is predominantly shaped by the W80 H ii bubble, driven by an O star. Several bright rims noted in the observation are probably remnant molecular clouds, heated and stripped by the massive star. Matching these rims in molecular lines and optical images, we construct a model of the three-dimensional structure of the NAP complex. Two groups of molecular clumps/filaments are on the near side of the bubble: one is being pushed toward us, whereas the other is moving toward the bubble. Another group is on the far side of the bubble, and moving away. The young stellar objects in the Gulf region reside in three different clusters, each hosted by a cloud from one of the three molecular clump groups. Although all gas content in the NAP is impacted by feedback from the central O star, some regionsmore »show no signs of star formation, while other areas clearly exhibit star formation activity. Additional molecular gas being carved by feedback includes cometary structures in the Pelican Head region, and the boomerang features at the boundary of the Gulf region. The results show that the NAP complex is an ideal place for the study of feedback effects on star formation.« less