ALBERT

Description: Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar System. We report here on millimeter spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between UT 16.948 to 18.120 January 2015, when the comet was at heliocentric distance of 1.30 au and geocentric distance of 0.53 au. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma. These observations allowed us to detect HCN, CH3OH (multiple transitions), H2CO and CO, and to measure precise molecular production rates. Additionally, sensitive upper limits were derived on the complex molecules acetaldehyde (CH3CHO) and formamide (NH2CHO) based on the average of the strongest lines in the targeted spectral range to improve the signal-to-noise ratio. Gas production rates are derived using a non-LTE molecular excitation calculation involving collisions with H2O and radiative pumping that becomes important in the outer coma due to solar radiation. We find a depletion of CO in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2.0%, and relatively low abundances of Q(HCN)/Q(H2O), 0.1%, and Q(H2CO)/Q(H2O), 0.2%. In contrast the CH3OH relative abundance Q(CH3OH)/Q(H2O), 2.2%, is close to the mean value observed in other comets. The measured production rates are consistent with values derived for this object from other facilities at similar wavelengths taking into account the difference in the fields of view. Based on the observed mixing ratios of organic molecules in four bright comets including C/2014 Q2, we find some support for atom addition reactions on cold dust being the origin of some of the molecules.

Description: The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [I]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of our new models for the chemistry of cometary comae that include atomic and molecular anions. We calculate the impact of these anions on the charge balance and examine their importance for cometary coma chemistry.

Description: We present sub-millimeter spectra of HCN isotopologues on Titan, derived from publicly available ALMA flux calibration observations of Titan taken in early 2014. We report the detection of a new HCN isotopologue on Titan, H13C15N, and confirm an earlier report of detection of DCN. We model high signal-to-noise observations of HCN, H13CN, HC15N, DCN, and H13C15N to derive abundances and infer the following isotopic ratios: 12C/13C = 89.8 +/- 2.8, 14N/15N = 72.3 +/- 2.2, D/H = (2.5 +/- 0.2) 104, and HCN/H13C15N = 5800 +/- 270 (1sigma errors). The carbon and nitrogen ratios are consistent with and improve on the precision of previous results, confirming a factor of approximately 2.3 elevation in 14N/15N in HCN compared to N2 and a lack of fractionation in 12C/13C from the protosolar value. This is the first published measurement of D/H in a nitrile species on Titan, and we find evidence for a factor of approximately 2 deuterium enrichment in hydrogen cyanide compared to methane. The isotopic ratios we derive may be used as constraints for future models to better understand the fractionation processes occurring in Titan's atmosphere.

Description: The 100-meter Robert C. Byrd Green Bank Telescope K-band (KFPA) receiver was used to perform a high-sensitivity search for rotational emission lines from complex organic molecules in the cold interstellar medium toward TMC-1 (Taurus Molecular Cloud - cyanopolyyne peak), focussing on the identification of new carbon-chain-bearing species as well as molecules of possible prebiotic relevance. We report a detection of the carbon-chain oxide species HC7O and derive a column density of (7.8 plus or minus 0.9) times 10 (sup 11) per square centimeter. This species is theorized to form as a result of associative electron detachment reactions between oxygen atoms and C7H minus, and/or reaction of C6H2 plus with CO (followed by dissociative electron recombination). Upper limits are given for the related HC6O, C6O, and C7O molecules. In addition, we obtained the first detections of emission from individual (sup 13) C isotopologues of HC7N, and derive abundance ratios HC7N/HCCCC (sup 13) CCCN equal to 110 plus or minus 16 and HC7N/HCCCC (sup 13) CCCN equal to 96 plus or minus 11, indicative of significant (sup 13) C depletion in this species relative to the local interstellar elemental (sup 12) C divided by (sup 13) C ratio of 60-70. The observed spectral region covered two transitions of HC11N, but emission from this species was not detected, and the corresponding column density upper limit is 7.4 times 10 (sup 10) per square centimeter (at 95 percent confidence). This is significantly lower than the value of 2.8 times 10 (sup 11) per square centimeter previously claimed by Bell et al. and conrms the recent nondetection of HC11N in TMC-1 by Loomis et al. Upper limits were also obtained for the column densities of malononitrile and the nitrogen heterocycles quinoline, isoquinoline, and pyrimidine.