Table 3
Radio continuum spectral index, free-free optical depth at 74 MHz, and ISM properties (emission measures (EM) and electronic densities (ne)) computed from our fit to the spectra presented in Fig. 3.
Absorption from extended envelopes of normal H II regions (EHEs) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Source (alias) | New results | Literature | |||||||
α | τ74 | EM (a) | ne (a) | α (b) | τ74 (c) | Refs. | |||
[cm−6 pc] | [cm−3] | ||||||||
G18.8 + 0.3 (Kes 67) | − 0.373 ± 0.010 | 0.043 ± 0.030 | 150 ± 130 | 1.2 ± 0.6 | − 0.46 to − 0.42 | 0.06 ± 0.03 | 1, 2; 1 | ||
G21.8 − 0.6 (Kes 69) | − 0.505 ± 0.018 | 0.088 ± 0.026 | 440 ± 140 | 2.1 ± 0.3 | − 0.56 to − 0.50 | 0.11 ± 0.04 | 1, 2; 1 | ||
G29.7 − 0.3 (Kes 75) | − 0.659 ± 0.014 | 0.176 ± 0.035 | 870 ± 190 | 2.9 ± 0.3 | − 0.73 to − 0.59 | 0.11 ± 0.04 | 1, 3; 1 | ||
G41.1 − 0.3 (3C 397) | − 0.356 ± 0.013 | 0.141 ± 0.013 | 720 ± 70 | 2.7 ± 0.2 | − 0.59 to − 0.46 | 0.13 ± 0.01 | 1, 2, 4; 1 | ||
Absorption: Special cases(d) | |||||||||
Source (alias) | New results | Literature | |||||||
α | τ74 | EM | ne | α (b) | τ74 (c) | Refs. | |||
[cm−6 pc] | [cm−3] | ||||||||
G23.3 − 0.3 (W41) | − 0.628 ± 0.040 | 1.214 ± 0.155 | 10 × 103 | 60 | − 0.63 to − 0.48 | 1.04 ± 0.11 | 1, 5; 1 | ||
G27.4 + 0.0 (Kes 73) | − 0.690 ± 0.035 | 0.878 ± 0.220 | 8–15 × 103 | 70–100 | − 0.71 ± 0.11 | 0.72 ± 0.32 | 1; 1 | ||
G31.9 + 0.0 (3C 391) | − 0.521 ± 0.004 | 1.210 ± 0.051 | 600–2500(e) | 10–40(e) | − 0.54 to − 0.49 | 1.1 | 1, 2, 6; 6 | ||
G39.2 − 0.3 (3C 396) | − 0.351 ± 0.010 | 0.063 ± 0.020 | — | — | − 0.53 to − 0.34 | 0.12 ± 0.04 | 1, 2, 4, 7; 1 | ||
G43.3 − 0.2 (W49B) | − 0.461 ± 0.009 | 0.580 ± 0.043 | 6−19 × 103 | 500 (f) | ≃ − 0.47 | 0.14 ± 0.05 | 1, 2; 8 | ||
No absorption | |||||||||
Source (alias) | New results | Literature | |||||||
α | α (b) | Refs. | |||||||
G4.5 + 6.8 (Kepler) | − 0.655 ± 0.010 | − 0.65 to − 0.62 | 1, 9 | ||||||
G21.5 − 0.9 | { | − 0.044 ± 0.013 ν ≲ 38 GHz | − 0.09 to +0.08 | 1, 2, 10, 11, 12 | |||||
− 0.546 ± 0.273 ν > 38 GHz | − 0.57 to −0.37 | 4, 12 | |||||||
G28.6 − 0.1 | − 0.690 ± 0.057 | − 0.6 to − 0.5 | 13 | ||||||
G120.1 + 1.4 (Tycho) | − 0.624 ± 0.004 | − 0.65 to − 0.58 | 1, 2, 9, 14, 15 | ||||||
G130.7 + 3.1 (3C 58) | { | − 0.076 ± 0.008 ν ≲ 12 GHz | − 0.10 to − 0.04 | 1, 2, 11, 14, 16, 17 | |||||
− 0.383 ± 0.022 ν > 12 GHz | − 0.58 to − 0.45 | 17, 18 |
Notes. (a) For EHEs, EM and ne calculations were done using a typical electron temperature of 5000 K and an average path length of 100 pc (Kassim 1989a). (b) Numbers without errors indicate that uncertainties are not given in the references. (c) Free-free continuum optical depth reported in the literature at a frequency ν were extrapolated to 74 MHz according to .
(d) The properties of the absorbing medium are analysed in Sect. 6.3. (e) The listed EM and ne values were extracted from the analysis in Brogan et al. (2005). (f)The estimate ne = 500 cm−3 comes from Zhu et al. (2014) for the postshock near-IR line emitting gas.
References. (1) Kovalenko et al. (1994a), (2) Sun et al. (2011), (3) Becker & Helfand (1984), (4) Anderson & Rudnick (1993), (5) Trushkin (1998), (6) Brogan et al. (2005), (7) Cruciani et al. (2016), (8) Kassim (1989b), (9) Reynolds & Ellison (1992), (10) Bietenholz & Bartel (2008), (11) Salter et al. (1989b), (12) Ivanov et al. (2019b), (13) Helfand et al. (1989), (14) Kothes et al. (2006), (15) Arias et al. (2019b), (16) Bietenholz et al. (2001), (17) Ivanov et al. (2019a), (18) Green & Scheuer (1992).
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