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arXiv 1104.0817astro-ph.CO
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II Zw 40、Mrk 71、Mrk 930、Mrk 996和SBS 0335- 052 E五个蓝色致密矮星系的近红外光谱

Near-infrared spectroscopy of five Blue Compact Dwarf galaxies: II Zw 40, Mrk 71, Mrk 930, Mrk 996 and SBS 0335-052E

Y. I. Izotov, T. X. Thuan

摘要:

本文介绍了对五个蓝矮星系(II Zw 40,Mrk 71,Mrk 930,Mrk 996和SBS 0335- 052 E)的近红外光谱观测结果。覆盖0.90微米-2.40微米波长范围的NIR光谱显示氢、分子氢、氦、硫和铁发射线。所有碱性催化剂的近红外数据都得到了光谱的补充。我们发现所有BCD的消光系数在光学和近红外范围内都非常相似。近红外氢发射谱线并没有显示出比光学谱线更多的恒星形成。从斯皮策关于和平号发射线的数据中也得到了同样的结论。这意味着低金属量BCD在~ 0.36 - 25微米波长范围内的发射线光谱是由相对透明的电离气体发射的。在某些BCD中,来自MIR连续发射的大消光意味着后者不是来自可见的H II区域本身,而是来自这些H II区域之外的位置。H2发射线通量可以通过荧光来解释。云恒星光化模型的所有BCD再现以及所观察到的光学和近红外发射线的大部分流量,除了在Mrk 930的冲击电离需要考虑的[Fe II]发射线。然而,在小于10%的恒星电离水平下的冲击电离的某些贡献需要再现所观察到的高电离物质的通量,例如光学范围内的He II 0.469微米和MIR范围内的[O IV] 25.89微米。

英文摘要:

We present near-infrared (NIR) spectroscopic observations of five blue compact dwarf (BCD) galaxies, II Zw 40, Mrk 71, Mrk 930, Mrk 996 and SBS 0335-052E. The NIR spectra which cover the 0.90 micron - 2.40 micron wavelength range, show hydrogen, molecular hydrogen, helium, sulfur and iron emission lines. The NIR data for all BCDs have been supplemented by optical spectra. We found the extinction coefficient in all BCDs to be very similar in both the optical and NIR ranges. The NIR hydrogen emission lines do not reveal more star formation than seen in the optical. The same conclusion is reached from Spitzer data concerning the MIR emission lines. This implies that emission-line spectra of low-metallicity BCDs in the ~ 0.36 - 25 micron wavelength range are emitted by relatively transparent ionized gas. The large extinction derived from the MIR continuum emission in some BCDs implies that the latter arises not from the visible H II regions themselves, but from locations outside these H II regions. The H2 emission line fluxes can be accounted for by fluorescence. CLOUDY stellar photoinization models of all BCDs reproduce well the fluxes of most of the observed optical and NIR emission lines, except in Mrk 930 where shock ionization is needed to account for the [Fe II] emission lines. However, some contribution of shock ionization at the level of < 10% that of stellar ionization is required to reproduce the observed fluxes of high ionization species, such as He II 0.469 micron in the optical range and [O IV] 25.89 micron in the MIR range.

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