ULIRGs中恒星星族的性质I：样本、数据和光谱合成模拟
The properties of the stellar populations in ULIRGs I: sample, data and spectral synthesis modelling
摘要：
我们提出了深长缝光谱的36个超铝红外Galeros（ULIRGs），采取与威廉赫歇尔望远镜（WHT）在拉帕尔马的目的是调查恒星形成的历史和测试这些对象的演化场景的样本。在这里，我们介绍了样本、分析技术以及恒星星族属性的总体概述。光谱合成模型已被用来估计年龄的恒星星族中发现的漫射光采样的光谱在核和扩展区域的目标星系。我们发现，适当的拟合可以得到使用年轻的恒星星族（YSPs，t_YSP<=2 Gyr），年龄分为两组：非常年轻的恒星星族（VYSPs，t_VYSP <= 1亿年）和中间年轻的恒星星族（IYSPs，0.1 < t_IYSP <= 2 Gyr）的组合。我们的研究结果表明，YSPs存在于我们的狭缝位置所覆盖的星系的所有位置，除了北核区域的ULIRG IRAS 23327+2913。此外，VYSP存在于用于本研究的133个提取孔中的至少85%中。老的恒星星族（OSP，t_{OSP} > 2 Gyr）对提取的大部分孔径中的可见光没有主要贡献。事实上，它们对于仅在提取的孔径的5%（7）中拟合光谱是必不可少的。YSP的估计总质量（VYSP + IYSP）在0.18 x 10^{10} <= M_YSP <= 50 x 10^{10} Msun的范围内。我们还估算了在可见光波段探测到的与恒星星族相关的辐射热光度，发现它们落在0.07 x 10^{12} < L_bol < 2.2 x 10^{12} Lsun的范围内。此外，我们发现星系中所有位置的变红都很明显。
英文摘要：
We present deep long-slit optical spectra for a sample of 36 Ultraluminous Infrared Galaxies (ULIRGs), taken with the William Herschel Telescope (WHT) on La Palma with the aim of investigating the star formation histories and testing evolutionary scenarios for such objects. Here we present the sample, the analysis techniques and a general overview of the properties of the stellar populations. Spectral synthesis modelling has been used in order to estimate the ages of the stellar populations found in the diffuse light sampled by the spectra in both the nuclear and extended regions of the target galaxies. We find that adequate fits can be obtained using combinations of young stellar populations (YSPs,t_YSP<=2 Gyr), with ages divided into two groups: very young stellar populations (VYSPs, t_VYSP <=100 Myr) and intermediate-young stellar populations (IYSPs, 0.1 < t_IYSP <= 2 Gyr). Our results show that YSPs are present at all locations of the galaxies covered by our slit positions, with the exception of the northern nuclear region of the ULIRG IRAS 23327+2913. Furthermore, VYSPs are presents in at least 85% of the 133 extraction apertures used for this study. Old stellar populations (OSPs, t_{OSP} > 2 Gyr) do not make a major contribution to the optical light in the majority of the apertures extracted. In fact they are essential for fitting the spectra in only 5% (7) of the extracted apertures. The estimated total masses for the YSPs (VYSPs+IYSPs) are in the range 0.18 x 10^{10} <= M_YSP <= 50 x 10^{10} Msun. We have also estimated the bolometric luminosities associated with the stellar populations detected at optical wavelengths, finding that they fall in the range 0.07 x 10^{12} < L_bol < 2.2 x 10^{12} Lsun. In addition, we find that reddening is significant at all locations in the galaxies.
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