CS, HC3N, and CH3CCH multi-line analyses toward starburst galaxies - The evolution of cloud structures in the central regions of galaxies

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Table 2

Observed lines.

Transition	Frequency	F_eff/B_eff	θ _beam	n _crit^(a)	Galaxy
	(GHz)		(^′′)	(cm^-3)

CS (2 − 1)	97.981	1.25	25.5	1.2 × 10⁵	NGC 253, IC 342
CS (3 − 2)	146.969	1.35	16.8	2.0 × 10⁶	IC 342, M 82
CS(5 − 4)	244.936	1.79	10.1	4.6 × 10⁷	NGC 253, IC 342, Maffei 2, M 82

HC₃N (9 − 8)	81.881	1.22	30.2	1.6 × 10⁶	IC 342, Maffei 2
HC₃N (10 − 9)	90.979	1.23	27.5	3.6 × 10⁶	IC 342
HC₃N (11 − 10)	100.076	1.25	24.9	4.8 × 10⁶	IC 342
HC₃N (12 − 11)	109.174	1.27	22.2	7.2 × 10⁶	IC 342, Maffei 2
HC₃N (15 − 14)	136.464	1.32	18.2	2.6 × 10⁷	IC 342, M 82, Maffei 2
HC₃N (16 − 15)	145.561	1.35	16.9	7.0 × 10⁷	IC 342, M 82
HC₃N (17 − 16)	154.657	1.38	16.0	1.0 × 10⁸	IC 342, M 82
HC₃N (18 − 17)	163.753	1.41	15.1	1.3 × 10⁸	M 82
HC₃N (23 − 22)	209.230	1.60	12.0	...	Maffei 2^∗
HC₃N (24 − 23)	218.325	1.66	11.5	...	IC 342, M 82
HC₃N (28 − 27)	254.699	1.92	9.7	...	M 82, Maffei 2^∗

CH₃CCH (5₀ − 4₀)	85.457	1.22	29.1	3.7 × 10⁴	IC 342, Maffei 2
CH₃CCH (6₀ − 5₀)	102.548	1.28	24.2	1.3 × 10⁵	IC 342, Maffei 2
CH₃CCH (8₀ − 7₀)	136.728	1.32	18.2	6.8 × 10⁵	M 82, IC 342, Maffei 2
CH₃CCH (9₀ − 8₀)	153.817	1.38	16.1	1.1 × 10⁶	M 82
CH₃CCH (10₀ − 9₀)	170.906	1.44	14.4	3.1 × 10⁶	M 82
CH₃CCH (13₀ − 12₀)	222.167	1.25 / 1.68 ^b	21.7 / 11.3^b	1.3 × 10⁷	NGC 253, Maffei 2^*
CH₃CCH (14₀ − 13₀)	239.252	1.80	10.3	2.9 × 10⁷	Maffei 2^*
CH₃CCH (15₀ − 14₀)	256.337	1.87	9.6	4.4 × 10⁷	M 82
CH₃CCH (16₀ − 15₀)	273.420	2.02	9.1	9.4 × 10⁷	M 82

c-C₃H₂ (2_1,2 − 1_0,1)	85.339	1.22	29.2	...	Maffei 2
c-C₃H₂ (5_2,4 − 4_1,3)	218.160	1.66	11.5	...	M 82
H₂CO (2_0,2 − 1_0,1)	145.603	1.35	16.9	2.3 × 10⁶	M 82, IC 342
H₂CO (3_0,3 − 2_0,2)	218.222	1.66	11.5	9.4 × 10⁶	M 82, IC 342
H₂CO (3_2,2 − 2_2,1)	218.476	1.53	11.5	5.2 × 10⁶	M 82

Notes. Last column indicates the galaxies where each transition was observed. Name in italics means a new detection.

^(*)

Name with^∗ means an upper limit of the line intensity.

^(a)

Critical densities corresponding to a T_kin = 90 K. Because of a lack of collisional coefficients in our LVG model for CH₃CCH, the n_crit for this molecule were calculated with the collisional coefficients of CH₃CN, which are very similar;

^(b)

the first value corresponds to NGC 253 observed with the JCMT telescope, and the second value corresponds to Maffei 2 observed with IRAM 30-m telescope.

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