/ftp/cats/aliases/V//VVH2014



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J/ApJ/780/85   Molecular line study of infrared dark clouds   (Vasyunina+, 2014)
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	table1.dat table2.dat table[89].dat
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Beginning of ReadMe : J/ApJ/780/85 Molecular line study of infrared dark clouds (Vasyunina+, 2014) ================================================================================ Organic species in infrared dark clouds. Vasyunina T., Vasyunin A.I., Herbst E., Linz H., Voronkov M., Britton T., Zinchenko I., Schuller F. <Astrophys. J., 780, 85 (2014)> =2014ApJ...780...85V ================================================================================ ADC_Keywords: Infrared sources ; Molecular clouds ; Interstellar medium ; Millimetric/submm sources ; Radio lines ; Abundances Keywords: ISM: clouds - ISM: molecules - radio lines: ISM - stars: formation Abstract: It is currently assumed that infrared dark clouds (IRDCs) represent the earliest evolutionary stages of high-mass stars (>8M_sun_). Submillimeter and millimeter-wave studies performed over the past 15yr show that IRDCs possess a broad variety of properties, and hence a wide range of problems and questions that can be tackled. In this paper, we report an investigation of the molecular composition and chemical processes in two groups of IRDCs. Using the Mopra, APEX, and IRAM radio telescopes over the last four years, we have collected molecular line data for CO, H_2_CO, HNCO, CH_3_CCH, CH_3_OH, CH_3_CHO, CH_3_OCHO, and CH_3_OCH_3_. For all of these species we estimated molecular abundances. We then undertook chemical modeling studies, concentrating on the source IRDC028.34+0.06, and compared observed and modeled abundances. This comparison showed that to reproduce observed abundances of complex organic molecules, a zero-dimensional gas-grain model with constant physical conditions is not sufficient. We achieved greater success with the use of a warm-up model, in which warm-up from 10K to 30K occurs following a cold phase. Description: For the present study, two sets of InfraRed Dark Clouds (IRDCs) were used, as listed in Tables 1 and 2. A set of southern sources, shown in Table 1, was selected from Vasyunina et al. 2011 (cat. J/A+A/527/A88). A set of northern sources, shown in Table 2, was taken from previous studies and includes classical clouds from the first studies about molecular line observations in IRDCs (e.g., Carey et al., 1998ApJ...508..721C; Pillai et al., 2006A&A...450..569P; Simon et al. 2006, cat. J/ApJ/639/227) as well as the recent work by Ragan et al. 2012 (cat. J/A+A/547/A49). With 22m Mopra telescope, several observational setups were employed. In all cases, we used the MOPS spectrometer, which allowed us to place 16 "zoom" windows along the 8.3GHz bandpass and reach a resolution of 0.1km/s, or 30kHz. Since for the present study we are interested mainly in organic species, we will focus only on the CO, HNCO, CH_3_CCH, and CH_3_OH molecules observed with Mopra. Four CO isotopologues, ^12^CO, ^13^CO, C^18^O, C^17^O, and CH_3_OH lines, were observed on 2011 April 27-May 2 with the central frequencies of 111.6GHz and 81GHz, respectively. The HNCO and CH_3_CCH data were obtained by adopting a central frequency of 89.27GHz, and have been already presented in Vasyunina et al. 2011 (cat. J/A+A/527/A88). Observations with the Atacama Pathfinder Experiment (APEX) telescope were conducted on 2011 September 25-26, 2011 November 15-18 and 2012 September 12-14. We used the APEX-1 receiver of the Swedish Heterodyne Facility Instrument (SHeFI) with frequency settings at 218.75, 243.25, and 214.77GHz. The backend for all observations was the eXtended bandwidth Fast Fourier Transform Spectrometer (XFFTS) with instantaneous bandwidth of 2.5GHz and 32768 spectral channels. This allowed us to cover the intervals 213-220.5GHz, and 241.5-243GHz for the southern objects and 213-220GHz for the northern objects with 88.5kHz spectral resolution. See Section 2.3 for all the details about the APEX observations. Observations with the IRAM 30m were performed on 2011 June 8-12. For these observations, the EMIR receiver with the Fast Fourier Transform Spectrometer (FTS) as a backend was used. During the observing run, the frequency intervals 76-79GHz and 152.5-156.5GHz were covered with a spectral resolution of 195kHz. According to the IRAM official website, at 86GHz the beam size is 29'', and the beam efficiency is 0.81, while at 153GHz, the telescope beam size is 16'', and the beam efficiency is 0.74.

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