Radio Properties of NGC$\thinspace$2363
Session 30 -- Star Formation, Molecular Clouds and HII Regions
Display presentation, Tuesday, 31, 1994, 9:20-6:30

## [30.10] Radio Properties of NGC$\thinspace$2363

Hui Yang, Evan Skillman (U. Minnesota)

We have obtained the high resolution VLA radio images of the giant H$\thinspace$II region NGC$\thinspace$2363 in 3.6 cm, 21 cm and 92 cm. The spectral index (resolution = 1$^{\prime\prime}$) from the low noise 3.6 cm (rms = 0.02 mJy) and 21 cm (rms = 0.028 mJy) data suggests that this source including the large bubble inside of it discovered by Roy et al.$\thinspace$(1991) is dominated by the thermal emission. The 92 cm result (resolution = 5.8$^{\prime\prime}$, rms = 2.2 mJy) more strongly constrains the source to be thermal. The bubble found in the [O$\thinspace$III] emission line shows 45 km s$^{-1}$ expanding velocity and has the size about 200 pc. The existence of SNRs in a giant H$\thinspace$II region is an eventual certainty and McCray \& Kafatos (1987) have demonstrated the natural evolution of an OB cluster into a superbubble with a size of $\sim$ 100pc and an age of 10$^7$ years. Roy et al.$\thinspace$(1991) estimate a kinematic age for the N2363 bubble of 2 $\times$ 10$^6$ years and conclude that stellar winds are responsible since this is too young for supernovae to have played an important role. Detection of nonthermal emission coincident with the bubble would imply otherwise. Although no evidence of nonthermal emission was found (unlike in NGC$\thinspace$5471; Skillman 1985), the presence of SNRs is not ruled out. The shell sizes are similar to those found in the giant H$\thinspace$II regions 30 Dor and NGC$\thinspace$604. They are also dominated by thermal emission, yet new X-ray observations suggest there are SNRs inside these shells. The bubble associated with NGC$\thinspace$2363 may be just like one of the big shells found inside of 30 Dor or NGC$\thinspace$604.