Red Geyser Galaxies and the Suppression of Star Formation

在宇宙的大部分时间里，典型的星系通过将氢气和氦气转化为新的恒星而不断成长。然而，在过去的几十亿年里（大约是宇宙历史的最近25%），许多星系停止形成恒星，似乎进入了永久的静止状态。我们自己的银河系可能正在经历类似的命运。天文学家们不仅试图了解最初是什么阻止了这些星系中星星的形成，而且还试图了解当有新的气体供应时，是什么阻止了它重新开始。这个项目试图了解一个新发现的现象，可能发挥作用。所谓的“红色间歇泉”星系在其中心拥有超大质量黑洞，这些黑洞周期性地散发出热气体风，传播到整个星系。这种热气体可能能够加热较冷的储层，防止它们坍缩成新的恒星。该项目将确认红色间歇泉和中央黑洞之间的关系，并详细研究红色间歇泉风，以了解它们如何影响其宿主星系。该计划还将有助于对学生进行研究方法的培训。它将通过为高中生和早期大学生开设培训班，支持使用专门的Marvin笔记本电脑进行天文研究。这些研究人员最近发现了一类新的静止的、相对常见的早期类型星系，它们拥有大规模的活动星系核驱动的风。这些“红色间歇泉”-在5-10%的静止星系中发现-可能是维持星系中低水平星星形成所需的缺少的能量来源，在这些星系中，星星的形成通常很久以前就停止了。初始积分场观测相对较低的分辨率（R~2000; 2.5弧秒FWHM）的MaNGA调查显示特征电离气体速度场。该项目通过凯克天文台的后续观测解决两个关键问题。研究人员试图确定（1）泄漏增强的排放是否是由于冲击或气体密度过高，以及（2）风能如何与较冷的环境气体耦合以抑制星星的形成。这两个问题都将通过分析最近获得的凯克光谱数据来解决，这些数据在空间和光谱上以更精细的细节解析了多组分气体结构，使研究人员能够在风和较冷材料之间的界面处搜索激波和湍流。这些凯克观测，获得六个红色间歇泉超过两个晚上，也将限制定量风模型，以确认红色间歇泉在抑制后期星星形成的作用。最后，他们将测试的假设，这些风是由低光度AGN反馈叠加可用的，但浅的无线电通量观测，以确定是否无线电AGN活动更经常与红色间歇泉现象的光学识别相关联。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

For most of cosmic time, typical galaxies grow continuously by turning hydrogen and helium gas into new stars. However, in the last few billion years (roughly the most recent 25% of cosmic history), many galaxies stopped forming stars and seem to have entered a permanent state of quiescence. Our own Milky Way galaxy may be undergoing a similar fate. Astronomers are not only trying to understand what initially stops star formation in these galaxies, but what keeps it from re-starting when fresh supplies of gas become available. This project seeks to understand a newly-discovered phenomenon that may play a role. So-called "red geyser" galaxies host super-massive black holes at their centers that periodically emanate a wind of hot gas that spreads through the entire galaxy. This hot gas may be able to heat up cooler reservoirs and prevent them from collapsing into new stars. This project will confirm the relationship between red geysers and central black holes and study red geyser winds in detail to understand how they impact their host galaxies. This program will also contribute to training in research methods for students. It will support the use of specialized Jupyter-type Marvin notebooks for astronomical research through training classes for high school students and early undergraduates. This training will provide experience and job-skills for next generation researchers.These investigators have recently discovered a new class of quiescent, relatively common early- type galaxy that hosts large-scale, AGN-driven winds. These "red geysers''---found in 5-10% of the quiescent population---may be the missing energy source needed to maintain low levels of star formation in galaxies where star formation in general ceased long ago. Initial integral field observations from the relatively low resolution (R~2000; 2.5 arcsec FWHM) MaNGA Survey revealed characteristic ionized gas velocity fields. This project addresses two key issues through follow-up observations with the Keck Observatory. Investigators seek to determine (1) whether the tell-tale enhanced emission is due to shocks or gas over-densities, and (2) how the wind energy couples to the cooler ambient gas in order to suppress star formation. Both questions will be addressed by analyzing recently obtained Keck spectroscopic data that spatially and spectrally resolves the multicomponent gas structure with finer detail, allowing the investigators to search for shocks and turbulence at the interface between the wind and cooler material. These Keck observations, obtained for six red geysers over two nights, will also constrain a quantitative wind model to confirm the role of red geysers in suppressing late-time star formation. Finally, they will test the hypothesis that these winds are driven by low-luminosity AGN feedback by stacking the available but shallow radio flux observations to determine whether radio AGN activity is more often associated with optical identification of the red geyser phenomenon.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.