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Table 4

Parameters of the emerging H ii regions deduced from line and continuum radiative transfer modeling (Sect. 5).

Parameter CRL 618 M2-9

Distance (d) 900 pc 650 pc
LSR systemic velocity (Vsys) − 19 km s-1 +75 km s-1
Geometry cylindrical cylindrical
Inner radius (Rin) 45 au 0.05 au (2 au)
Outer radius (Rout) 95 au 160 au
Electron density (ne) 2.4 × 107()-2.0  cm-3 6.4 × 105  cm-3
Electron temperature (Te) 16500 K 7500 K
Kinematics radial expansion radial expansion
Velocity (V)  km s-1 22 km s-1
Kinematic age (tk) 15–20 yr 15 yr
Inclination (i) 24° 17°
Mass-loss rate () 8.4 × 10-6M yr-1 3.9 × 10-7M yr-1
Ionized mass (Mion) 2.0 × 10-4M 5.5 × 10-6M
Parameter MWC 922

Distance (d) 1700 pc
LSR systemic velocity (Vsys) +33 km s-1
Geometry double-cone
Double-cone’s semi-opening angle (θa) 25°
Inclination (i) 0°
Inner radius (Rin) 0.05 au (35 au)
Electron density (ne) 9 × 107exp(− (θaθ) / 2°)  cm-3
Electron temperature (Te) 6700 K
Opening angle of the ionized disk (θd) 6.5°
Ionized disk’s outer radius (rd) 50 au
Ionized outflow’s outer radius (Rout) ~150 au
Ionized outflow’s velocity (Vexp) 5 km s-1 (radial expansion)
Keplerian rotation velocity (Vrot) 32.6/ km s-1
Mass-loss rate () 2 × 10-6M yr-1
Ionized mass (Mion) 3.6 × 10-5M

Notes. In all cases, r is the radial distance to the center; the mass-loss rate () is the equivalent isotropic mass-loss rate for a constant expansion velocity and ner-2; and the departure coefficients bn used are from Storey & Hummer (1995).


For CRL 618 and M 2-9, we assume a cylindrical H ii region with an outer radius Rout at the base (i.e., along the nebula equator) and a central spherical cavity with inner radius Rin. The cylinder extends to infinity along the major axis, where ~90% of the mm-continuum is produced within ~110 au and ~50 au along the axis, respectively.


Double-cone geometry as described in Sect. 5.3 and depicted in Fig. 3 of Báez-Rubio et al. (2013).

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