标题： 恒星在LINERs能量学中的作用 显示英文标题

标题： The Role of Stars in the Energetics of LINERs

摘要： 成像研究显示，大约25%的LINER星系表现出紧凑的核紫外光源。我比较了现在可用于七个这样的“紫外明亮”LINER的HST紫外光谱。NGC 404、NGC 4569和NGC 5055的光谱显示出大质量恒星的清晰吸收线特征，表明紫外连续谱具有恒星起源。类似特征可能存在于NGC 6500中。同样的恒星特征可能存在于NGC 4594中，但由于光谱信噪比低，以及在M81和NGC 4579中由于叠加的强而宽的发射线而无法检测到。这些星系中观察到的紧凑中心紫外连续谱源是核星团，而不是低光度活动星系核（AGN），至少在某些情况下如此。至少四个LINER存在电离光子不足的情况，即从观测到的远紫外连续谱推断出的电离光子通量不足以驱动光学H I重组线。检查每个星系的核X射线流量显示，在这四个“紫外光子匮乏”的LINER中X射线/紫外比率很高。在这四个天体中，一个主要在极端紫外发射的独立组分可能是电离剂，可能与观测到的核紫外辐射无关。未来的观测可以确定LINER中的紫外连续谱是否总是由星暴主导，或者是否存在两种类型的紫外明亮LINER：星暴主导型和AGN主导型。有趣的是，最近的结果显示，星暴也主导了许多赛弗特2型星系的核能。 显示英文摘要

摘要： Imaging studies have shown that about 25% of LINER galaxies display a compact nuclear UV source. I compare the HST ultraviolet spectra now available for seven such ``UV-bright'' LINERs. The spectra of NGC 404, NGC 4569, and NGC 5055 show clear absorption-line signatures of massive stars, indicating a stellar origin for the UV continuum. Similar features are probably present in NGC 6500. The same stellar signatures may be present but undetectable in NGC 4594, due to the low signal-to-noise ratio of the spectrum, and in M81 and NGC 4579, due to superposed strong, broad emission lines. The compact central UV continuum source that is observed in these galaxies is a nuclear star cluster rather than a low-luminosity active galactic nucleus (AGN), at least in some cases. At least four of the LINERs suffer from an ionizing photon deficit, in the sense that the ionizing photon flux inferred from the observed far-UV continuum is insufficient to drive the optical H I recombination lines. Examination of the nuclear X-ray flux of each galaxy shows a high X-ray/UV ratio in the four ``UV-photon starved'' LINERs. In these four objects, a separate component, emitting predominantly in the extreme-UV, is the likely ionizing agent, and is perhaps unrelated to the observed nuclear UV emission. Future observations can determine whether the UV continuum in LINERs is always dominated by a starburst or, alternatively, that there are two types of UV-bright LINERs: starburst-dominated and AGN-dominated. Interestingly, recent results show that starbursts dominate the nuclear energetics in many Seyfert 2s as well.