The Herschel Dwarf Galaxy Survey - II. Physical conditions, origin of [C II] emission, and porosity of the multiphase low-metallicity ISM

D. Cormier; N. P. Abel; S. Hony; V. Lebouteiller; S. C. Madden; F. L. Polles; F. Galliano; I. De Looze; M. Galametz; A. Lambert-Huyghe

doi:10.1051/0004-6361/201834457

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Volume 626 (June 2019)

A&A, 626 (2019) A23

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Table 3.

Results of the H II+PDR best-fitting models for the DGS galaxies where single models are preferred.

			1-component model					2-component model
Galaxy	Z_bin	N_c^(a)	log n_H, HII^(b)	log n_H, PDR^(c)	log U	cov_PDR		log n_H, HII	log n_H, PDR	log U	cov_PDR	f_c^(d)
NGC 1705...	0.50	8					8.41 [1.68]	1.00	2.02	−2.39	1.00	0.50	6.85 [2.28]
								1.00	−	−2.88	0.00	0.50
IIZw 40...	0.50	13					19.33 [1.93]	2.50	3.41	−1.89	0.80	0.80	18.41 [2.30]
								2.50	−	−1.89	0.00	0.20
Mrk 930...	0.25	12					17.41 [1.93]	0.50	2.28	−0.38	0.60	0.60	5.77 [0.82]
								0.50	−	−3.29	0.00	0.40
NGC 1569...	0.25	13					11.43 [1.14]	0.50	2.28	−0.38	0.60	0.70	3.35 [0.42]
								0.50	−	−2.85	0.00	0.30
HS 1330...	0.25	5	0.50	2.28			2.38 [1.19]	0.50	2.28	−0.88	0.80	0.80	1.97 [−]
								0.50	−	−3.63	0.00	0.20
HS 1304...	0.25	5	0.50^1.61	2.28^2.98			17.83 [8.91]	0.50	2.28	−0.38	0.60	0.50	9.72 [−]
								0.50	−	−3.29	0.00	0.50
Mrk 153...	0.25	9					8.74 [1.46]	0.50	2.28	−0.88	0.60	0.60	2.34 [0.59]
								0.50	−	−2.85	0.00	0.40
UM 133...	0.25	4					0.37 [0.37]	3.00	3.83	−3.38	0.40	0.10	0.03 [−]
								1.00	−	−3.79	0.00	0.90
HS 1319...	0.25	3	0.50^3.50	2.28^5.05			0.30 [−]	2.00	3.28	−1.38	0.20	0.30	< 0.01 [−]
								1.00	−	−3.79	0.00	0.70
HS 1222...	0.25	4	0.50^1.04	2.28^2.44			1.32 [1.32]	2.50	3.72	−1.88	0.20	0.80	0.39 [−]
								0.50	−	−3.63	0.00	0.20
Mrk 209...	0.10	8					3.67 [0.73]	1.00	2.87	−0.35	1.00	0.30	2.55 [0.85]
								0.50	−	−0.85	0.00	0.70
Pox 186...	0.10	7				0.20	1.47 [0.37]	2.00	3.73	−0.85	0.20	0.90	0.93 [0.46]
								1.00	−	−3.76	0.00	0.10
SBS 1249...	0.10	4				0.20	0.52 [0.52]	1.00	2.87	−0.35	0.20	0.60	0.02 [−]
								0.50	−	−3.26	0.00	0.40
HS 0017...	0.10	3					0.03 [−]	2.50	3.98	−2.35	1.00	0.30	< 0.01 [−]
								1.50	−	−3.34	0.00	0.70
HS 1442...	0.10	4					0.34 [0.34]	1.00	2.87	−0.35	0.80	0.60	0.19 [−]
								1.00	−	−0.35	0.00	0.40
SBS 1211...	0.10	5				0.20	0.87 [0.44]	1.50	3.09	−1.85	0.60	0.30	0.28 [−]
								0.50	−	−2.34	0.00	0.70
SBS 1415...	0.10	8					4.47 [0.89]	1.00	2.87	−1.85	0.60	0.50	2.76 [0.92]
								1.00	−	−2.35	0.00	0.50
Tol 1214...	0.10	6				0.20	9.01 [3.00]	1.00	2.86	−0.85	0.20	0.60	7.13 [7.13]
								1.00	−	−3.76	0.00	0.40
UGC 4483...	0.10	4					2.06 [2.06]	1.50	3.01	−2.35	0.80	0.10	0.40 [−]
								0.50	−	−3.62	0.00	0.90
SBS 1159...	0.10	6					14.05 [4.68]	1.00	2.86	−1.35	0.40	0.20	4.88 [4.88]
								1.00	−	−3.76	0.00	0.80
HS 0822...	0.05	5				0.20	4.63 [2.32]	1.50	3.48	−0.83	0.20	0.70	4.14 [−]
								1.00	−	−3.75	0.00	0.30
SBS 0335...	0.05	9					7.42 [1.24]	2.00	4.01	−0.83	0.60	0.70	5.98 [1.49]
								1.00	−	−1.33	0.00	0.30
IZw 18...	0.05	8				0.20	9.88 [1.98]	1.00	3.18	−1.33	0.80	0.10	0.62 [0.21]
								1.00	−	−1.83	0.00	0.90

Notes. This table reports results of galaxies for which single models are preferred, and Table 4 reports results for galaxies where mixed models are preferred. The following notes apply to both tables.

^(a)

N_c is the number of observational constraints (number of detected lines plus 1 for the luminosity constraint).

^(b)

n_H, HII corresponds to the initial density.

^(c)

n_H, PDR corresponds to the density of the PDR at the H I-H₂ transition (i.e., A_V∼1 mag).

^(d)

f_c (1 − f_c) is the contribution of the first (second) model to the mixed model. We note that the values of the covering factor are those of the initial grid (with full coverage of the H II region). For 2-component models, cov_PDR needs to be further multiplied by f_c to obtain the effective covering factor. Galaxies are sorted by decreasing metallicity. For one-component models, uncertainties on the free parameters are given in upper and lower scripts and are calculated as the average ± the standard deviation of models within the 1σ confidence level (see Sect. 3.2 for details). The number of free parameters n_free is three for the one-component model, and five for the two-component model. The degrees of freedom are given by ν = N_c − n_free. The reduced χ² is given by .

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