The mysterious cut-off of the Planetary Nebula Luminosity Function
The mysterious cut-off of the Planetary Nebula Luminosity Function
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行星状星云光度函数的神秘截止
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
M. M. Bertolami
中科院分区：
文献类型：
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作者：
K. Gesicki;A. Zijlstra;M. M. Bertolami
行星状星云 (PNe) 标志着 90% 的恒星活跃生命的结束。他们追踪了从红巨星到简并白矮星的转变。恒星模型预测，只有大约两倍于太阳质量的恒星才能形成明亮的PN。但在古老的恒星群（例如椭圆星系）中，明亮的PNe无处不在，这与这一点相矛盾：如此大质量的恒星并不存在于古老的系统中。行星状星云光度函数（PNLF），尤其是其明亮截止点，在具有高质量恒星的年轻螺旋星系和仅具有低质量恒星的古老椭圆星系之间几乎是不变的。在这里，我们展示了低质量恒星的新演化轨迹能够以简单的方式解释这个数十年之久的谜团。观测到的 PNLF 与恒星演化之间的一致性验证了最新的理论模型。通过这些模型，PNLF 提供了强大的诊断手段来推导中龄恒星的恒星形成历史。新模型预测，太阳在其生命终结时也将形成PN，但它会很微弱。低质量和中等质量的恒星，高达约8M⊙，以极端质量损失的阶段结束其生命。超级风将包膜弹出，只留下简并的核心。在进入白矮星末期冷却阶段之前，核心会短暂电离喷射物。在分散到星际介质中之前，电离的喷射物在数千年中都以行星状星云 (PN) 的形式保持可见。 PNe 形成其宿主恒星演化过程中最亮的阶段，典型光度为 L ∼ 10L⊙。此外，大部分星云光度以一些明亮、狭窄的发射线形式出现。最亮的线，[O III] 5007 Å，可发射高达 10L⊙ 的能量。这使得 PNe 可以在很远的距离内被探测到，包括室女座星团以外的星系。 PNLF 已被确立为重要的河外距离估计器。然而，恒星演化模型迄今为止还无法解释它。 PNLF 描述了星系中每个指定光度区间的 PNe 比例。对于发射线 [O III] 5007 Å，绝对星等为
Planetary Nebulae (PNe) mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models predicted that only stars above approximately twice the solar mass could form a bright PN. But the ubiquitous presence of bright PNe in old stellar populations, such as elliptical galaxies, contradicts this: such high mass stars are not present in old systems. The planetary nebula luminosity function (PNLF), and especially its bright cut-off, is almost invariant between young spiral galaxies, with high mass stars, and old elliptical galaxies, with only low mass stars. Here we show that new evolutionary tracks of low-mass stars are capable to explain in a simple manner the decades-old mystery. The agreement between the observed PNLF and stellar evolution validates the latest theoretical modelling. With these models, the PNLF provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a PN, but it will be faint. Low and intermediate mass stars, up to about 8M⊙, end their lives with a phase of extreme mass loss. The superwind ejects the envelope, leaving only the degenerate core behind. The core briefly ionizes the ejecta, before entering the terminal white dwarf cooling stage. The ionized ejecta remain visible as a planetary nebula (PN) for thousands of years, before dispersing into the interstellar medium. PNe form the most luminous phase of evolution of their host stars, with typical luminosity L ∼ 10L⊙. In addition, much of the nebular luminosity comes out in a few bright, narrow emission lines. The brightest line, [O III] 5007 Å, can emit as much as 10L⊙. This makes PNe detectable to very large distances, including galaxies beyond the Virgo cluster. The PNLF has been established as an important extragalactic distance estimator. However, stellar evolution models have thus far been unable to explain it. The PNLF describes the fraction of PNe in a galaxy at each specified luminosity bin. For the emission line [O III] 5007 Å, the absolute magnitude is