I. M. Coulson

MAPPING THE RELEASE OF VOLATILES IN THE INNER COMAE OF COMETS C/2012 F6 (LEMMON) AND C/2012 S1 (ISON) USING THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H_2CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution ≈0.5), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN is found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii ~500-1000 km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H_2CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H_2CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H_2CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.

Ground-based multiwavelength observations of comet 103P/Hartley 2

The Jupiter-family comet 103P/Hartley 2 (103P) was the target of the NASA EPOXI mission. In support of this mission, we conducted observations from radio to submillimeter wavelengths of comet 103P in the three weeks preceding the spacecraft rendezvous on UT 2010 November 4.58. This time period included the passage at perihelion and the closest approach of the comet to the Earth. Here, we report detections of HCN, H{sub 2}CO, CS, and OH and upper limits for HNC and DCN toward 103P using the Arizona Radio Observatory Kitt Peak 12 m telescope (ARO 12 m) and submillimeter telescope (SMT), the James Clerk Maxwell Telescope (JCMT), and the Green Bank Telescope (GBT). The water production rate, Q{sub H{sub 2O}} = (0.67-1.07) × 10{sup 28} s{sup –1}, was determined from the GBT OH data. From the average abundance ratios of HCN and H{sub 2}CO relative to water (0.13 ± 0.03% and 0.14 ± 0.03%, respectively), we conclude that H{sub 2}CO is depleted and HCN is normal with respect to typically observed cometary mixing ratios. However, the abundance ratio of HCN with water shows a large diversity with time. Using the JCMT data, we measured an upper limit for the DCN/HCN ratio 8 K (2σ).«xa0less

Catastrophic Disruption of Comet ISON

We report submillimeter 450 and 850 μm dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 (rh = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>105 km) in the anti-solar direction. Deconvolution of the November 28.04 850 μm image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ∼5.2 × 1010 kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the cometʼs residual nucleus.

Thermal Physics of the Inner Coma: ALMA Studies of the Methanol Distribution and Excitation in Comet C/2012 K1 (PanSTARRS)

We present spatially and spectrally-resolved observations of CH

The Evolution of Volatile Production in Comet C-2009 P1%28Garradd%29 During its 2011-2012 Apparition

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ALMA Mapping of Rapid Gas and Dust Variations in Comet C/2012 S1 (ISON): New Insights into the Origin of Cometary HNC

OH emission from comet C/2012 K1 (PanSTARRS) using The Atacama Large Millimeter/submillimeter Array (ALMA) on 2014 June 28-29. Two-dimensional maps of the line-of-sight average rotational temperature (

Measuring the Distribution and Excitation of Cometary CH3OH Using ALMA

T_{rot}

JCMT Observations of the Deep Impact Event

) were derived, covering spatial scales

JCMT Spectral and Continuum Imaging of Comet 252P/LINEAR

0.3-1.8

Erratum: Mapping the release of volatiles in the inner comae of comets C/2012 F6 (LEMMON) and C/2012 S1 (ISON) using the atacama large millimeter/submillimeter array (Astrophysical Journal Letters (2014) 792 (L2))

(corresponding to sky-projected distances