The Kinematics of NGC$\thinspace$604

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Session 13 -- HII Regions
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[13.01] The Kinematics of NGC$\thinspace$604

Hui Yang, Evan Skillman (UMn), You-Hua Chu (UIl), Roberto Terlevich (RGO)

We have obtained interference filter CCD images at six wavelengths and mapped the internal motions with both long-slit echelle spectra and TAURUS Fabry-Perot observations. The physical and kinematical properties of NGC$\thinspace$604 are studied in H$\alpha$ emission, [S$\thinspace$II] ($\lambda$6717 and $\lambda$6731), and [O$\thinspace$III] ($\lambda$5007). The densities found from the [S$\thinspace$II] ratios are surprisingly uniform and always in the low density regime ($\leq$ 100 cm$^{-3}$). From excitation maps of [S$\thinspace$II]/H$\alpha$ and [O$\thinspace$III]/H$\alpha$, we recovered a previously known SNR and identified several ionization fronts.

The kinematics of NGC$\thinspace$604 are very complex and show numerous filaments and shell structures. The good spatial coincidence between some of the shell structures and the presence of line splitting in the Echelle data implies that the shell structures are truly expanding shells. Two shells have very high expansion velocities of over 100 km s$^{-1}$. Both stellar winds and supernova remnants are considered as the causes of the expanding shells. The high velocity gas and the extended X-ray emission (comparable with 30 Doradus (Chu \& Kennicutt 1994)) make it likely that there are SNRs in NGC$\thinspace$604 and that some of them are inside of the two high velocity expanding shells. Compared to the inner regions ($\leq$ 200 pc), the outer regions ($\geq$ 200 pc) have turbulent velocity around 20.4 to 33 km s$^{-1}$ FWHM and lack high velocity gas. Although most of the positions have FWHM larger than the thermal broading, there are bright positions having FWHM 22 km s$^{-1}$ which is about the same as the thermal broading. This fact indicates that the spatial resolution of our data is high enough to resolve individual clouds. The integrated profile made from the TAURUS data shows a surprisingly simple profile with a broad Gaussion core and faint extended wings. This structure can be explained by the combinated effects of thermal broading, stellar winds and supernovae. The only conventional SNR in NGC$\thinspace$604 is also found in the Echelle data with very high expanding velocity gas at 200 km s$^{-1}$.

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