Post-Starbursts as Laboratories: Probing Star Formation Quenching and Late Phases of Stellar Evolution with NIRWALS

镓可以被认为是形成“工厂”的星星，在那里各种过程（例如，密度波、潮汐力、合并、气体流入）的作用产生了密度大、引力不稳定的气体区域，这些气体随后碎裂并坍缩成恒星。根据所涉及的具体过程，这可能会导致相当恒定的星星形成率（SFR）或激烈但短暂的插曲，主要限于星系的核心，并经常伴随着气体吸积到超大质量黑洞上。星暴星系是后者的例子。在极端的情况下，星暴之后是一个漫长的“后星暴”阶段，在这个阶段中，星星的形成大部分被熄灭或“熄灭”。“首席研究员（PI）将领导一个团队，使用近红外（NIR）积分场摄谱仪在当地星暴后星系的大样本中研究这种淬火。改进的恒星演化模型也将得到测试。拟议的工作还将为本科生提供研究经验和培训，为博士论文提供材料，并向公共领域提供大型天文数据集。该团队将使用11米南部非洲大型望远镜（SALT）上的新近红外积分场光谱仪（NIRWALS）观察50个星暴后星系的样本。一个关键的问题是，星星形成淬灭是由降低的SFE引起的，还是由超新星和/或吸积超大质量黑洞的气体猛烈喷出引起的。近红外氢帕邢发射线将用于测量准确的星星形成率，与SFE估计结合现有的CO数据。氦、硫和铁的近红外发射线将用于揭示冲击气体，并确定中心超大质量黑洞是否主动向气体注入能量。该团队将比较后星暴星系的星光与新的恒星演化合成模型的预测。这些模型包括改进处理恒星演化的后期阶段，这些阶段主导了5亿至20亿岁（大致是观测星系的爆发后年龄）之间恒星种群的近红外辐射。正确校准这些模型对于理解星系中恒星质量随宇宙时间的积累至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Galaxies can be thought of as star forming "factories," where various processes (e.g., density waves, tidal forces, mergers, gas inflows) act to create regions of dense, gravitationally unstable gas, which subsequently fragment and collapse into stars. Depending on the specific process involved, this could result in a fairly constant star formation rate (SFR) or in an intense but short- lived episode, largely confined to the galaxy's nucleus and often accompanied by gas accreting onto a supermassive blackhole. Starburst galaxies are examples of the latter. In extreme cases the starburst is followed by a lengthy 'post-starburst' phase in which star formation is largely extinguished or 'quenched.' The principal investigator (PI) will lead a team investigating this quenching in a large sample of local post-starburst galaxies using a near-infrared (NIR) integral field spectrograph. Improved stellar evolution models will also be tested. The proposed work will also provide research experience and training for undergraduate students, provide material for a PhD thesis, and deliver a large astronomical dataset to the public domain. The team will observe a sample of 50 post-starburst galaxies using a new NIR integral-field spectrograph (NIRWALS) on the 11-meter Southern African Large Telescope (SALT). A key question is whether star formation quenching is caused by a lowered SFE or if it is caused by the violent blow-out of gas by supernova and/or or accreting supermassive blackholes. NIR hydrogen Paschen emission lines will be used to measure accurate star formation rates, with SFE estimated in combination with existing CO data. NIR emission lines of helium, sulfur, and iron will be used to reveal shocked gas and to determine if central supermassive blackholes actively inject energy into the gas. The team will compare post-starburst galaxies’ starlight to predictions of new stellar evolutionary synthesis models. These models include improved treatment of the late stages of stellar evolution that dominate the NIR emission of stellar populations between 0.5 to 2 billion years old (roughly the post-burst age of the observed galaxies). Correctly calibrating these models is critical for understanding the build-up of stellar mass in galaxies over cosmic time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.