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J/MNRAS/446/3842    Spectral line survey of two LOSs   (Armijos-Abendano+, 2015)

3-mm spectral line survey of two lines of sight towards two typical cloud complexes in the Galactic Centre. Armijos-Abendano J., Martin-Pintado J., Requena-Torres M.A., Martin S., Rodriguez-Franco A. <Mon. Not. R. Astron. Soc., 446, 3842-3862 (2015)> =2015MNRAS.446.3842A (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Interstellar medium ; Molecular clouds ; Line Profiles Keywords: ISM: abundances - ISM: clouds - ISM: molecules - Galaxy: centre Abstract: We present the results of two Mopra 3-mm spectral line surveys of the lines of sight (LOS) towards the Galactic Centre (GC) molecular complexes Sgr B2 (LOS+0.693) and Sgr A (LOS-0.11). The spectra covered the frequency ranges of ∼77-93 GHz and ∼105-113 GHz. We have detected 38 molecular species and 25 isotopologues. The isotopic ratios derived from column density ratios are consistent with the canonical values, indicating that chemical isotopic fractionation and/or selective photodissociation can be considered negligible (<10 percent) for the GC physical conditions. The derived abundances and rotational temperatures are very similar for both LOSs, indicating very similar chemical and excitation conditions for the molecular gas in the GC. The excitation conditions are also very similar to those found for the nucleus of the starburst galaxy NGC 253. We report for the first time the detection of HCO and HOC+ emission in LOS+0.693. Our comparison of the abundance ratios between CS, HCO, HOC+ and HCO+ found in the two LOSs with those in typical Galactic photodissociation regions (PDRs) and starbursts galaxies does not show any clear trend to distinguish between ultraviolet- and X-ray-induced chemistries. We propose that the CS/HOC+ ratio could be used as a tracer of the PDR components in the molecular clouds in the nuclei of galaxies. Description: The observations were carried out with the 22-m Mopra radio telescope in November 2007. We used the dual 3-mm Monolithic Microwave Integrated Circuit (MMIC) receiver connected to the 8-GHz spectrometer, which provided a velocity resolution of ∼0.9 km/s at 90 GHz. Spectra in two polarizations were observed simultaneously. Two frequency ranges in the 3-mm window were covered, ∼77-93 GHz and ∼105-113 GHz. The beam size of the telescope was 38 arcsec at 90 GHz and 30 arcsec at 115 GHz. Objects: ---------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------- 17 47 20.4 -28 23 07 Sgr B2 = NAME Sgr B2 17 45 40.04 -29 00 28.2 Sgr A = NAME Sgr A * ---------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 126 224 Line parameters for the LOS+0.693 table2.dat 126 150 Line parameters for the LOS-0.11 table3.dat 99 150 Trot, column densities and abundances for both LOSs
See also: J/ApJS/117/427 : Sgr B2 spectral survey (Nummelin+, 1998) J/ApJS/196/12 : First results from Mopra HCO+ maps (Barnes+, 2011) J/A+A/595/A94 : Temperature structures in Galactic center clouds (Immer+, 2016) Byte-by-byte Description of file: table1.dat table2.dat
Bytes Format Units Label Explanations
1- 15 A15 --- Mol Molecule 16 A1 --- n_Mol [bc] Note on molecule (1) 18- 25 F8.1 MHz Freq Frequency 27- 56 A30 --- Trans Transition 58- 63 F6.2 Area ? Area 65- 67 F3.1 e_Area ? Uncertainty in Area 69- 72 F4.1 km/s b_VLSR ? Local Standard of Rest velocity interval, lower value 74- 78 F5.1 km/s B_VLSR ? Local Standard of Rest velocity interval, upper value 80- 84 F5.2 km/s VLSR ? Local Standard of Rest velocity 86- 88 F3.1 km/s e_VLSR ? Uncertainty in VLSR 89 A1 --- n_VLSR [a] Note on VLSR (2) 91- 94 F4.1 km/s Deltav1/2 ? Average value of the FWHM of the line, Δv1/2 96-100 F5.2 km/s e_Deltav1/2 ? Uncertainty in Deltav1/2 101 A1 --- n_Deltav1/2 [a] Note on Deltav1/2 (2) 103-108 F6.1 mK Ta* ? Ambient temperature 110-115 F6.2 mK e_Ta* ? Uncertainty in Ta* 116 A1 --- n_Ta* [a] Note on Ta* 118-126 A9 --- Note Note(s) (3)
Note (1): Note as follows: b = Substates EE, AA, EA, AE blended, we show just the most intense transition. c = Frequency refers to species A. Note (2): Note as follows: a = Parameter fixed in the Gaussian fit. Note (3): Note as follows: bl = Blended line; m = Multitransition line (frequency refers to the main component of the group); hf = Hyperfine structure (frequency refers to the main component of the group); hfa = Hyperfine component, it is possible to resolve this hyperfine component since its frequency is sufficiently far from the frequencies of the other hyperfine components; ot = Transition less affected by opacity; cl = This line is contaminated by the emission from an unknown molecular species; al = Absorption line; cd = This transition have been used to derive the column density (although several transitions of this molecule have been detected, there is an insufficient dynamical range in Eu to derive the column density by using a rotational diagram).
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1 A1 --- LOS [AB] Line of sight identification (1) 3- 17 A15 --- Mol Molecule 19 A1 --- n_Mol [e] Note on Mol (2) 21- 22 I2 km/s b_VLSR ? Local Standard of Rest velocity interval, lower value 24- 26 I3 km/s B_VLSR ? Local Standard of Rest velocity interval, upper value 27 A1 --- nBVLSR [g] Note on B_VLSR (3) 29 A1 --- l_VLSR [~] Limit flag on VLSR 30- 33 F4.1 km/s VLSR ? Local Standard of Rest velocity 35- 37 F3.1 km/s e_VLSR ? Uncertainty in VLSR 38 A1 --- n_VLSR [cf] Note on VLSR (4) 40- 43 F4.1 K Trot ? Rotational temperature (5) 45- 49 F5.2 K e_Trot ? Uncertainty in Trot 50 A1 --- n_Trot [c] Note on Trot (4) 52- 53 A2 --- l_N [≳ ] Limit flag on N 54- 61 F8.2 10+13/cm2 N ? Local thermodynamic equilibrium total molecular column density 63- 69 F7.2 10+13/cm2 e_N ? Uncertainty in N 70 A1 --- n_N [bcd] Note on N (4) 72- 75 F4.1 10-9 b_N/NH2 ? N/NH2 column density ratio interval, lower value 77- 80 F4.1 10-9 B_N/NH2 ? N/NH2 column density ratio interval, upper value 81 A1 --- nBN/NH2 [g] Note on B_N/NH2 (3) 83- 84 A2 --- l_N/NH2 [≳ ] Limit flag on N/NH2 85- 91 F7.2 10-9 N/NH2 ? N/NH2 column density ratio 93- 99 F7.3 10-9 e_N/NH2 ? Uncertainty in N/NH2
Note (1): LOS as follows: A = LOS+0.693; B = LOS-0.11. Note (2): Note as follows: e = The observed transition is contaminated by the emission from an unknown molecular species. Note (3): Note as follows: g = These velocity ranges are chosen for deriving velocity-integrated intensities used in the molecular column density estimate. For LOS+0.693 we have used a velocity range for the 13CS(2-1) line as it is affected by opacity or self-absorption. For the 15N isotopologues of HNC and HCN, the velocity ranges are suitable for deriving 14N/15N ratios (see text). Note (4): Note as follows: b = We have inferred from the 12C/13C~<15,14N/15N~<280 and 16O/18O~<186 isotopic ratios given in Table 4 that the column density of the most abundant isotopologues of these molecules are biased by opacity or self-absorption. Thus here we have derived the column density by using either the 18O, 15N or 13C isotopologue for the respective velocity component and assuming 16O/18O=250 or 14N/15N>600 (Wilson & Rood, 1994ARA&A..32..191W) and if necessary our value 12C/13C=21. For LOS+0.693, the SiO column density is derived from the 28SiO isotopologue assuming 28Si/30Si=18 derived for LOS-0.11; c = Only one line of this molecule was detected; d = Although several transitions of this molecule are detected, there is an insufficient dynamical range for Eu to derive the column density from a rotational diagram, so we have chosen one transition, usually the less affected by opacity; f = This velocity is an average of different detected transitions. Note (5): Trot derived from rotational diagrams (RDs) or assumed for deriving molecular column densities. The assumed Trot for the 13C isotopologues of CH3CCH and CH3CN are taken from their other isotopologues. The assumed Trot for CH3OH and its 13C isotopologue are taken from Requena-Torres et al. (2008ApJ...672..352R). The Trot quoted with uncertainties are determined from RDs. When Trot is not listed then Trot=10 K is assumed, which corresponds to an average value of the low Trot component derived from other molecules by using RDs.
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 03-Nov-2017
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