Table 2.
Summary of the molecular lines in our compiled data set towards the centre of NGC 6946.
| νrest | νobs | Eu | nH2 (ϵmax) | neff | Project code | Setup | |||
|---|---|---|---|---|---|---|---|---|---|
| Molecules | [GHz] | [GHz] | [K] | [cm−3] | [cm−3] | ||||
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | |
| C2H | N = (1 − 0), J = 3/2 − 1/2 | 87.316 | 87.302 | 4.19 | Q059+R02C | A | |||
| HCN | (1 − 0) | 88.632 | 88.617 | 4.25 | 2 × 105 | 4.5 × 103 | Q059+R02C+P069 | A | |
| HCO+ | (1 − 0) | 89.188 | 89.173 | 4.28 | 4 × 104 | 5.3 × 102 | Q059+R02C | A | |
| HNC | (1 − 0) | 90.664 | 90.648 | 4.35 | 1 × 105 | 2.3 × 103 | Q059+R02C | C | |
| 3 mm | HC3N | (10 − 9) | 90.979 | 90.964 | 16.69 | 4.3 × 104 | R09F | C | |
| N2H+ | (1 − 0) | 93.174 | 93.158 | 4.47 | 5.5 × 103 | R09F | C | ||
| CH3OH | JK = 20 − 10 | 96.741 | 96.725 | 6.96 | Q059+R02C | B | |||
| CS | (2 − 1) | 97.980 | 97.965 | 7.10 | 1.2 × 104 | R09F+S08E | B | ||
| 12CO | (1 − 0) | 115.271 | 115.252 | 5.53 | 1 × 102 | M032 | D | ||
| CH3OH | JK = 30 − 20 | 145.100 | 145.073 | 18.80 | S02A | B | |||
| HC3N | (16 − 15) | 145.561 | 145.534 | 41.27 | S02A | B | |||
| 2 mm | p-H2CO | N = (2 − 1), J = 0/2 − 0/1 | 145.603 | 145.576 | 10.48 | 6.3 × 104 | S02A | B | |
| CS | (3 − 2) | 146.969 | 146.942 | 14.11 | 3.3 × 104 | S02A | B | ||
| 1.3 mm | 12CO | (2 − 1) | 230.538 | 230.499 | 16.59 | 1 × 103 | M032+P069 | One mm | |
Notes. (1) and (2) Molecular lines with their transition ordered by their rest frequencies; Throughout the paper, for simplicity, we refer to the transitions of C2H as (1−0), of CH3 OH as (2−1) and (3−2), and of H2CO as (2−1). (3) and (4) Rest and observational frequencies. (5) Upper energy levels. (6) Minimum density at which the emissivity of the line reaches 95% of its peak value for T = 25 K (see Table 2 within Leroy et al. 2017 and references therein). (7) Taken from Shirley (2015) (Table 1, for 20 K), and have been defined by radiative transfer modelling as the density that results in a molecular line with an integrated intensity of 1 K km s−1. (8) and (9) PdBI project code and setup. A = configuration C and D; B = configuration A, B, C, D; C = configuration B, C, D.
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