Browsing by Author "Carpenter, John"

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    An early and comprehensive millimetre and centimetre wave and X-ray study of SN 2011dh : a non-equipartition blast wave expanding into a massive stellar wind
    (2013) Horesh, Assaf; Stockdale, Christopher; Fox, Derek B.; Frail, Dale A.; Carpenter, John; Kulkarni, S. R.; Ofek, Eran O.; Gal-Yam, Avishay; Kasliwal, Mansi M.; Bauer, Franz Erik
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    Chemistry in Externally FUV-irradiated Disks in the Outskirts of the Orion Nebula Cluster
    (2024) Diaz-Berrios, Javiera K.; Guzman, Viviana V.; Walsh, Catherine; Oberg, Karin I.; Cleeves, L. Ilsedore; de la Villarmois, Elizabeth Artur; Carpenter, John
    Most stars are born in stellar clusters, and their protoplanetary disks, which are the birthplaces of planets, can, therefore, be affected by the radiation of nearby massive stars. However, little is known about the chemistry of externally irradiated disks, including whether or not their properties are similar to the so-far better-studied isolated disks. Motivated by this question, we present ALMA Band 6 observations of two irradiated Class II protoplanetary disks in the outskirts of the Orion Nebula Cluster to explore the chemical composition of disks exposed to (external) far-ultraviolet (FUV) radiation fields: the 216-0939 disk and the binary system 253-1536A/B, which are exposed to radiation fields of 102-103 times the average interstellar radiation field. We detect lines from CO isotopologues, HCN, H2CO, and C2H toward both protoplanetary disks. Based on the observed disk-integrated line fluxes and flux ratios, we do not find significant differences between isolated and irradiated disks. The observed differences seem to be more closely related to the different stellar masses than to the external radiation field. This suggests that these disks are far enough away from the massive Trapezium stars, that their chemistry is no longer affected by external FUV radiation. Additional observations toward lower-mass disks and disks closer to the massive Trapezium stars are required to elucidate the level of external radiation required to make an impact on the chemistry of planet formation in different kinds of disks.
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    Constraints on the Physical Origin of Large Cavities in Transition Disks from Multiwavelength Dust Continuum Emission
    (2024) Sierra, Anibal; Perez, Laura M.; Sotomayor, Benjamin; Benisty, Myriam; Chandler, Claire J.; Andrews, Sean; Carpenter, John; Henning, Thomas; Testi, Leonardo; Ricci, Luca; Wilner, David
    The physical origin of the large cavities observed in transition disks is to date still unclear. Different physical mechanisms (e.g., a companion, dead zones, enhanced grain growth) produce disk cavities of different depth, and the expected spatial distribution of gas and solids in each mechanism is not the same. In this work, we analyze the multiwavelength interferometric visibilities of dust continuum observations obtained with Atacama Large Millimeter/submillimeter Array and Very Large Array for six transition disks: CQTau, UXTau A, LkCa15, RXJ1615, SR24S, and DMTau, and calculate brightness radial profiles, where diverse emission morphology is revealed at different wavelengths. The multiwavelength data are used to model the spectral energy distribution and compute constraints on the radial profile of the dust surface density, maximum grain size, and dust temperature in each disk. They are compared with the observational signatures expected from various physical mechanisms responsible for disk cavities. The observational signatures suggest that the cavities observed in the disks around UXTau A, LkCa15, and RXJ1615 could potentially originate from a dust trap created by a companion. Conversely, in the disks around CQTau, SR24S, DMTau, the origin of the cavity remains unclear, although it is compatible with a pressure bump and grain growth within the cavity.
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    Radial and Vertical Constraints on the Icy Origin of H2CO in the HD 163296 Protoplanetary Disk
    (2024) Hernandez-Vera, Claudio; Guzman, Viviana V.; Artur de la Villarmois, Elizabeth; OEberg, Karin I.; Cleeves, L. Ilsedore; Hogerheijde, Michiel R.; Qi, Chunhua; Carpenter, John; Fayolle, Edith C.
    H2CO is a small organic molecule widely detected in protoplanetary disks. As a precursor to grain-surface formation of CH3OH, H2CO is considered an important precursor of O-bearing organic molecules that are locked in ices. Still, since gas-phase reactions can also form H2CO, there remains an open question on the channels by which organics form in disks, and how much the grain versus the gas pathways impact the overall organic reservoir. We present spectrally and spatially resolved Atacama Large Millimeter/submillimeter Array observations of several ortho- and para-H2CO transitions toward the bright protoplanetary disk around the Herbig Ae star HD 163296. We derive column density, excitation temperature, and ortho-to-para ratio (OPR) radial profiles for H2CO, as well as disk-averaged values of N-T similar to 4 x 10(12) cm(-2), T-ex similar to 20 K, and OPR similar to 2.7, respectively. We empirically determine the vertical structure of the emission, finding vertical heights of z/r similar to 0.1. From the profiles, we find a relatively constant OPR similar to 2.7 with radius, but still consistent with 3.0 among the uncertainties, a secondary increase of N-T in the outer disk, and low T-ex values that decrease with disk radius. Our resulting radial, vertical, and OPR constraints suggest an increased UV penetration beyond the dust millimeter edge, consistent with an icy origin but also with cold gas-phase chemistry. This Herbig disk contrasts previous results for the T Tauri disk, TW Hya, which had a larger contribution from cold gas-phase chemistry. More observations of other sources are needed to disentangle the dominant formation pathway of H2CO in protoplanetary disks.