• Dopita, M. A.
• Kennicutt, R. C.
• Pellerin, A.
• Gallagher, J. S.
• Chandar, R.
• Hong, Sungryong
• Martin, C.
• Calzetti, D.

Abstract

We present the small- and intermediate-scale structure of interstellar medium(ISM) of five local starburst galaxies; NGC1569, NGC4449, Holmberg II, NGC5236, and HE2-10. Each galaxy has four narrow band images for H-beta(4861A), [OIII](5007A), H-alpha(6563A), and [SII](6717,6731A) (or [NII](6583A)), imaged by Advanced Camera for Survey(ACS), Wide Field Planetary Camera 2(WFPC2), and Wide Field Camera 3(WFC3) of the Hubble Space Telescope(HST). We produce line diagnostics diagrams from those narrow band images on a pixel-by-pixel basis and discriminate shock-ionized gas (pixels) by using the ``maximum starburst line'' of Kewley et al. (2001). The properties of line ratios, [SII]/H-alpha vs [OIII]/H-beta, H-alpha vs [OIII]/H-beta, and H-alpha vs [SII]/H-alpha, for photo-ionized gas are well explained by the photo-ionization model of Kewley et al. (2001). When comparing the four galaxies, NGC3077, NGC4214, NGC5236, and NGC5253, previously studied in Calzetti et al. (2004) with our galaxies, we have found similar groups which share the same trend in line ratio plots. The origin of the groups can be explained by the effects of different metallicity and different starforming strength with respect to potential depth, which are strongly related to cooling rate and galactic wind driving mechanism. We compare the shock-ionized gas with shock-ionization model of Allen et al. (2008). Although the ``maximum starburst line'' gives us conservative estimation of shock-ionized gas, our rough estimation of shock velocity 250km/s of HE2-10 is consistent with Mendez et al. (1999). As an Appendix, we present a new objective technique for continuum subtraction from narrow-band image. We have found that skewness values of continuum subtracted images show a transitional feature around the optimal subtraction. We present some real applications and discuss about the strong points and the weak points of this technique....

Topics

• impedance spectroscopy
• strength