Table 2
Parameters employed or derived for the Bar.
| Parameter | Value | Reference |
|---|---|---|
| Distance | 414±7 pc (a) 1″= 0.002 pc | Menten et al. (2007) |
| Projected distance, dproj, between θ1 Ori C and the IF | 0.228 pc | |
Transverse size  |
~0.1 pc | Peeters et al. (2023) |
| G0 at IF | ~(2.2–7.1) × 104 | Peeters et al. (2023) |
| FUV dust cross-section σH | 6.5 × 10−22 cm2/H | Cardelli et al. (1989); Blagrave et al. (2007) Schirmer et al. (2022) |
| RV = AV/E(B − V) | 5.5 | Cardelli et al. (1989); Blagrave et al. (2007) |
| AV/NH | 3.5 × 10−22 mag/cm−2 | Cardelli et al. (1989); Blagrave et al. (2007) |
| Density in atomic PDR nH | (5–10) × 104 cm−3 | This article (Sect. 5.1) |
| Density at the IF ne | 5 × 103 cm−3 | Weilbacher et al. (2015) |
| Temperature at the IF Te | ~9 × 103 K | Weilbacher et al. (2015) |
| Distance between IF and DF dIF−DF | 0.02–0.04 pc | This article (Sect. 5.2.1) |
| Average atomic density between IF and DF | 4.6 ×104 cm−3 | This article (Sect. 5.2.1) |
| Density from NIR H2 nH | (3.5)×104 to ×105 cm−3 | Peeters et al. (2023) |
| Temperature at the DF T | ~400–700 K | Allers et al. (2005), van de Putte et al. (2024) |
Notes. (a)The adopted distance is based on the Menten et al. (2007) study using radio very long baseline interferometry. We underline that more recent observations, including Gaia, point to slightly lower or similar values. Kounkel et al. (2017) used the Very Large Baseline Array and measured a distance of 388±5 pc toward the Orion Nebula Cluster (ONC). This distance corresponds to the weighted average distance of all the stars located toward the ONC, including the Trapezium. Kounkel et al. (2018) used Gaia DR2 and measured an average distance of 386±3 pc for the ONC. However, other studies based on Gaia DR2 parallaxes such as Binder & Povich (2018); Großschedl et al. (2018); Kuhn et al. (2019) quote distances for the ONC of 410 pc, 400–410 pc and 
pc, respectively which are near the estimate from Menten et al. (2007). Großschedl et al. (2018) suggested that the about 10 pc difference compared to the literature value can be seen as an estimate of remaining systematic uncertainties. In Appendix A of Kuhn et al. (2019), they compare their distance estimate to one from Kounkel et al. (2018) and discuss effects of the three-dimensional structure of Orion A. Moreover, one should note that these distances correspond to the distances of the stars and not the one of the molecular cloud and the Bar. New Gaia releases (in combination with new trigonometric parallax) will provide even more accurate distance determinations. For simplicity, we choose to assume the distance of 414±7 pc from Menten et al. (2007) in order to remain consistent with Berné et al. (2022b). The difference in distance values has anyway no important implications for the results presented in this article.
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