Now showing items 1-20 of 33

    • Applications of High-Resolution Observations of Millimeter Wavelengths 

      Rosenfeld, Katherine (2015-12-17)
      nterferometric observations at millimeter wavelengths provide a precious, detailed view of certain astrophysical objects. This thesis is composed of studies that both rely on and enable this technique to study the structure ...
    • C/o and Snowline Locations in Protoplanetary Disks: The Effect of Radial Drift and Viscous Gas Accretion 

      Piso, Ana-Maria Adriana; Oberg, Karin; Birnstiel, Tilman David; Murray-Clay, Ruth Ann (IOP Publishing, 2015)
      The C/O ratio is a defining feature of both gas giant atmospheric and protoplanetary disk chemistry. In disks, the C/O ratio is regulated by the presence of snowlines of major volatiles at different distances from the ...
    • Chemical Imaging of the CO Snow Line in the HD 163296 Disk 

      Qi, Chunhua; Oberg, Karin; Andrews, Sean M.; Wilner, David J.; Bergin, Edwin A.; Hughes, Amy L; Hogherheijde, Michiel; D’Alessio, Paola (IOP Publishing, 2015)
      The condensation fronts (snow lines) of H2O, CO, and other abundant volatiles in the midplane of a protoplanetary disk affect several aspects of planet formation. Locating the CO snow line, where the CO gas column density ...
    • CO diffusion into amorphous H2O ices 

      Lauck, Trish; Karssemeijer, Leendertjan; Shulenberger, Katherine; Rajappan, Mahesh; Oberg, Karin; Cuppen, Herma M. (IOP Publishing, 2015)
      The mobility of atoms, molecules, and radicals in icy grain mantles regulates ice restructuring, desorption, and chemistry in astrophysical environments. Interstellar ices are dominated by H2O, and diffusion on external ...
    • The comet-like composition of a protoplanetary disk as revealed by complex cyanides 

      Oberg, Karin; Guzmán, Viviana V.; Furuya, Kenji; Qi, Chunhua; Aikawa, Yuri; Andrews, Sean M.; Loomis, Ryan; Wilner, David J. (Nature Publishing Group, 2015)
      Observations of comets and asteroids show that the Solar Nebula that spawned our planetary system was rich in water and organic molecules. Bombardment brought these organics to the young Earth's surface, seeding its early ...
    • Complex molecule formation around massive young stellar objects 

      Oberg, Karin; Fayolle, Edith C.; Reiter, John B.; Cyganowski, Claudia Jane Klimick (Royal Society of Chemistry (RSC), 2014)
      Interstellar complex organic molecules were first identified in the hot inner regions of massive young stellar objects (MYSOs), but have more recently been found in many colder sources, indicating that complex molecules ...
    • Complex Organic Molecules During Low-Mass Star Formation: Pilot Survey Results 

      Oberg, Karin; Lauck, Trish; Graninger, Dawn M (IOP Publishing, 2014)
      Complex organic molecules (COMs) are known to be abundant toward some low-mass young stellar objects (YSOs), but how these detections relate to typical COM abundance are not yet understood. We aim to constrain the frequency ...
    • Complex organic molecules in organic-poor massive young stellar objects 

      Fayolle, Edith C.; Oberg, Karin; Garrod, Robin T.; van Dishoeck, Ewine F.; Bisschop, Suzanne E. (EDP Sciences, 2015)
      Context. Massive young stellar objects (MYSOs) with hot cores are classic sources of complex organic molecules. The origins of these molecules in such sources, as well as the small- and large-scale differentiation between ...
    • Constraining the X-ray and cosmic ray ionization chemistry of the TW Hya protoplanetary disk: evidence for a sub-interstellar cosmic-ray rate. 

      Cleeves, Lauren Ilsedore; Bergin, Edwin A.; Qi, Chunhua; Adams, Fred C.; Oberg, Karin (IOP Publishing, 2015)
      We present an observational and theoretical study of the primary ionizing agents (cosmic rays and X-rays) in the TW Hya protoplanetary disk. We use a set of resolved and unresolved observations of molecular ions and other ...
    • Cyanide Photochemistry and Nitrogen Fractionation in the Mwc 480 Disk 

      Guzmán, V. V.; Oberg, Karin; Loomis, Ryan; Qi, Celina (IOP Publishing, 2015)
      HCN is a commonly observed molecule in Solar System bodies and in interstellar environments. Its abundance with respect to CN is a proposed tracer of UV exposure. HCN is also frequently used to probe the thermal history ...
    • Detection of N2D+ in a protoplanetary disk 

      Huang, Jane; Oberg, Karin (IOP Publishing, 2015)
      Observations of deuterium fractionation in the solar system, and in interstellar and circumstellar material, are commonly used to constrain the formation environment of volatiles. Toward protoplanetary disks, this approach ...
    • The distribution and chemistry of H2CO in the DM Tau protoplanetary disk 

      Loomis, Ryan; Cleeves, Lauren Ilsedore; Oberg, Karin; Guzman, Viviana V.; Andrews, Sean M. (IOP Publishing, 2015)
      H2CO ice on dust grains is an important precursor of complex organic molecules (COMs). H2CO gas can be readily observed in protoplanetary disks and may be used to trace COM chemistry. However, its utility as a COM probe ...
    • Double DCO+ rings reveal CO ice desorption in the outer disk around IM Lup 

      Oberg, Karin; Furuya, Kenji; Loomis, Ryan; Aikawa, Yuri; Andrews, Sean M.; Qi, Chunhua; Dishoeck, Ewine F. van; Wilner, David J. (IOP Publishing, 2015)
      In a protoplanetary disk, a combination of thermal and non-thermal desorption processes regulate where volatiles are liberated from icy grain mantles into the gas phase. Non-thermal desorption should result in volatile-enriched ...
    • First Detection of c-C3H2 in a Circumstellar Disk 

      Qi, Chunhua; Oberg, Karin; Wilner, David J.; Rosenfeld, Katherine Ann (IOP Publishing, 2013)
      We report the first detection of c-C3H2 in a circumstellar disk. The c-C3H2 J = 6-5 line (217.882 GHz) is detected and imaged through Atacama Large Millimeter Array (ALMA) Science Verification observations toward the disk ...
    • G11.92-061-MM2: A bonafide massive prestellar core? 

      Cyganowski, C. J.; Brogan, C. L.; Hunter, Tucker R; Graninger, Dawn M; Oberg, Karin; Vasyunin, A.; Zhang, Qiyu; Friesen, R.; Schnee, S. (IOP Publishing, 2014)
      Core accretion models of massive star formation require the existence of stable massive starless cores, but robust observational examples of such objects have proven elusive. We report subarcsecond-resolution Submillimeter ...
    • G11.92–0.61-MM2: A bonafide massive prestellar core? 

      Cyganowski, C. J.; Brogan, C. L.; Hunter, T. R.; Graninger, Dawn M; Oberg, Karin; Vasyunin, A.; Zhang, Q.; Friesen, R.; Schnee, S. (IOP Publishing, 2014)
      Core accretion models of massive star formation require the existence of stable massive starless cores, but robust observational examples of such objects have proven elusive. We report subarcsecond-resolution Submillimeter ...
    • H2CO and N2H+ in Protoplanetary Disks: Evidence for a CO-Ice Regulated Chemistry 

      Qi, Chunhua; Oberg, Karin; Wilner, David J. (IOP Publishing, 2013)
      We present Submillimeter Array observations of H2CO and N2H+ emission in the disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296 at 2"-6" resolution and discuss the distribution of these species with ...
    • HNC in Protoplanetary Disks 

      Graninger, Dawn M; Oberg, Karin; Qi, Chunhua; Kastner, Joel (IOP Publishing, 2015)
      The distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. ...
    • The HNC/HCN Ratio in Star-Forming Regions 

      Graninger, Dawn M; Herbst, Eric; Oberg, Karin; Vasyunin, Anton I. (IOP Publishing, 2014)
      HNC and HCN, typically used as dense gas tracers in molecular clouds, are a pair of isomers that have great potential as a temperature probe because of temperature dependent, isomer-specific formation and destruction ...
    • Imaging of the CO Snow Line in a Solar Nebula Analog 

      Qi, Chunhua; Oberg, Karin; Wilner, David J.; D'Alessio, Paola; Bergin, E.; Andrews, Sean M.; Blake, G. A.; Hogerheijde, M. R.; van Dishoeck, E. F. (American Association for the Advancement of Science (AAAS), 2013)
      Planets form in the disks around young stars. Their formation efficiency and composition are intimately linked to the protoplanetary disk locations of “snow lines” of abundant volatiles. We present chemical imaging of the ...