Space telescope imaging spectrograph slitless observations of Small Magellanic Cloud planetary nebulae: A study on morphology, emission-line intensity, and evolution

被引:60
作者
Stanghellini, L
Shaw, RA
Balick, B
Mutchler, M
Blades, JC
Villaver, E
机构
[1] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[2] Natl Opt Astron Observ, Tucson, AZ 85719 USA
[3] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[4] ESA, Space Telescope Div, F-75738 Paris 15, France
关键词
Magellanic Clouds; planetary nebulae : general; stars : AGB and post-AGB; stars : evolution;
D O I
10.1086/378042
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
A sample of 27 planetary nebulae (PNs) in the Small Magellanic Cloud (SMC) have been observed with the Hubble Space Telescope Imaging Spectrograph (HST/STIS) to determine their morphology, size, and the spatial variation of the ratios of bright emission lines. The morphologies of SMC PNs are similar to those of LMC and Galactic PNs. However, only a third of the resolved SMC PNs are asymmetric, compared to half of those in the LMC. The low-metallicity environment of the SMC seems to discourage the onset of bipolarity in PNs. We measured the line intensity, average surface brightness, and photometric radius of each nebula in Halpha, Hbeta, [O III] lambdalambda4959 and 5007, [N II] lambdalambda6548 and 6584, [S II] lambdalambda6716 and 6731, He I lambda6678, and [O I] lambdalambda6300 and 6363. We show that the surface brightness -to-radius relationship is the same as in LMC PNs, indicating its possible use as a distance scale indicator for Galactic PNs. We determine the electron densities and the ionized masses of the nebulae where the [S II] lines were measured accurately, and we find that the SMC PNs are denser than the LMC PNs by a factor of 1.5. The average ionized mass of the SMC PNs is 0.3 M-.. We also found that the median [O III]/Hbeta intensity ratio in the SMC is about half that of the corresponding LMC median. We use CLOUDY to model the dependence of the [O III]/ Hbeta ratio on the oxygen abundance. Our models encompass very well the average observed physical quantities. We suggest that the SMC PNs are principally cooled by the carbon lines, making it hard to study their excitation based on the optical lines at our disposal.
引用
收藏
页码:997 / 1014
页数:18
相关论文
共 23 条