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 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:
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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
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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
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Bytes Format Units Label Explanations
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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 K.km/s Area ? Area
65- 67 F3.1 K.km/s 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)
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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).
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Byte-by-byte Description of file: table3.dat
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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
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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 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 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.
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 03-Nov-2017