开创性的新暗物质图验证了爱因斯坦的广义相对论

Atacama Cosmology Telescope Collaboration 的研究最终在理解宇宙演化方面取得了重大突破。

几千年来，人类一直对宇宙的奥秘着迷。

与想象宇宙起源的古代哲学家不同，现代宇宙学家使用定量工具来深入了解宇宙的演化和结构。 随着爱因斯坦广义相对论的发展，现代宇宙学可以追溯到 20 世纪初。

现在，来自阿塔卡马宇宙学望远镜 (ACT) 合作组织的研究人员向 这[{” attribute=””>Astrophysical Journal featuring a groundbreaking new map of dark matter distributed across a quarter of the sky, extending deep into the cosmos, that confirms Einstein’s theory of how massive structures grow and bend light over the 14-billion-year life span of the universe.

The new map uses light from the cosmic microwave background (CMB) essentially as a backlight to silhouette all the matter between us and the Big Bang.

The Atacama Cosmology Telescope in Northern Chile, supported by the National Science Foundation, operated from 2007-2022. The project is led by Princeton University and the University of Pennsylvania — Director Suzanne Staggs at Princeton, Deputy Director Mark Devlin at Penn — with 160 collaborators at 47 institutions. Credit: Mark Devlin, Deputy Director of the Atacama Cosmology Telescope and the Reese Flower Professor of Astronomy at the University of Pennsylvania

“It’s a bit like silhouetting, but instead of just having black in the silhouette, you have texture and lumps of dark matter, as if the light were streaming through a fabric curtain that had lots of knots and bumps in it,” said Suzanne Staggs, director of ACT and Henry DeWolf Smyth Professor of Physics at Princeton University. “The famous blue and yellow CMB image [from 2003] 它是大约 130 亿年前宇宙在一个时代的快照，现在它为我们提供了自那时以来所有时代的信息。”

领导这项分析的物理学和天体物理学教授乔·邓克利 (Joe Dunkley) 告诉 ACT：“能够看到不可见的事物，并揭示支撑我们可见星状星系的暗物质支架，真是令人兴奋。” “在这张新图片中，我们可以亲眼看到环绕并连接星系的无形暗物质宇宙网。”

“通常情况下，天文学家只能测量光，所以我们可以看到星系是如何分布在整个宇宙中的。这些观测揭示了质量的分布，因此它们基本上显示了暗物质是如何在我们的宇宙中分布的，”普林斯顿查尔斯 A. .

阿塔卡马宇宙望远镜合作的研究最终形成了一张具有开创性的新暗物质地图，覆盖整个天空的四分之一，深入宇宙。 这些结果进一步支持了爱因斯坦的广义相对论，一个多世纪以来它一直是宇宙学标准模型的基础，并提供了揭开暗物质神秘面纱的新方法。 图片来源：Lucy Reading-Ikkanda，西蒙斯基金会

“我们绘制了天空中不可见暗物质的分布图，这与我们的理论所预测的完全一致，”共同作者 Blake Sherwin 博士说，2013 年。 毕业于普林斯顿大学和剑桥大学宇宙学教授，在那里他领导着一大群 ACT 研究人员。 “这是一个惊人的证据，表明我们了解宇宙结构如何在数十亿年内形成的故事，但[{” attribute=””>Big Bang to today.’

He added: “Remarkably, 80% of the mass in the universe is invisible. By mapping the dark matter distribution across the sky to the largest distances, our ACT lensing measurements allow us to clearly see this invisible world.”

“When we proposed this experiment in 2003, we had no idea the full extent of information that could be extracted from our telescope,” said Mark Devlin, the Reese Flower Professor of Astronomy at the University of Pennsylvania and the deputy director of ACT, who was a Princeton postdoc from 1994-1995. “We owe this to the cleverness of the theorists, the many people who built new instruments to make our telescope more sensitive, and the new analysis techniques our team came up with.” This includes a sophisticated new model of ACT’s instrument noise by Princeton graduate student Zach Atkins.

Research by the Atacama Cosmology Telescope collaboration has culminated in a groundbreaking new map of dark matter distributed across a quarter of the entire sky, reaching deep into the cosmos. Findings provide further support to Einstein’s theory of general relativity, which has been the foundation of the standard model of cosmology for more than a century, and offer new methods to demystify dark matter. Credit: Image courtesy of Debra Kellner

Despite making up most of the universe, dark matter has been hard to detect because it doesn’t interact with light or other forms of electromagnetic radiation. As far as we know, dark matter only interacts with gravity.

To track it down, the more than 160 collaborators who have built and gathered data from the National Science Foundation’s Atacama Cosmology Telescope in the high Chilean Andes observed light emanating following the dawn of the universe’s formation, the Big Bang — when the universe was only 380,000 years old. Cosmologists often refer to this diffuse CMB light that fills our entire universe as the “baby picture of the universe.”

The team tracked how the gravitational pull of massive dark matter structures can warp the CMB on its 14-billion-year journey to us, just as antique, lumpy windows bend and distort what we can see through them.

“We’ve made a new mass map using distortions of light left over from the Big Bang,” said Mathew Madhavacheril, a 2016-2018 Princeton postdoc who is the lead author of one of the papers and an assistant professor in physics and astronomy at the University of Pennsylvania. “Remarkably, it provides measurements that show that both the ‘lumpiness’ of the universe, and the rate at which it is growing after 14 billion years of evolution, are just what you’d expect from our standard model of cosmology based on Einstein’s theory of gravity.”

Sherwin added, “Our results also provide new insights into an ongoing debate some have called ‘The Crisis in Cosmology.’” This “crisis” stems from recent measurements that use a different background light, one emitted from stars in galaxies rather than the CMB. These have produced results that suggest the dark matter was not lumpy enough under the standard model of cosmology and led to concerns that the model may be broken. However, the ACT team’s latest results precisely assessed that the vast lumps seen in this image are the exact right size.

“While earlier studies pointed to cracks in the standard cosmological model, our findings provide new reassurance that our fundamental theory of the universe holds true,” said Frank Qu, lead author of one of the papers and a Cambridge graduate student as well as a former Princeton visiting researcher.

“The CMB is famous already for its unparalleled measurements of the primordial state of the universe, so these lensing maps, describing its subsequent evolution, are almost an embarrassment of riches,” said Staggs, whose team built the detectors that gathered this data over the past five years. “We now have a second, very primordial map of the universe. Instead of a ‘crisis,’ I think we have an extraordinary opportunity to use these different data sets together. Our map includes all of the dark matter, going back to the Big Bang, and the other maps are looking back about 9 billion years, giving us a layer that is much closer to us. We can compare the two to learn about the growth of structures in the universe. I think is going to turn out to be really interesting. That the two approaches are getting different measurements is fascinating.”

ACT, which operated for 15 years, was decommissioned in September 2022. Nevertheless, more papers presenting results from the final set of observations are expected to be submitted soon, and the Simons Observatory will conduct future observations at the same site, with a new telescope slated to begin operations in 2024. This new instrument will be capable of mapping the sky almost 10 times faster than ACT.

Of the co-authors on the ACT team’s series of papers, 56 are or have been Princeton researchers. More than 20 scientists who were junior researchers on ACT while at Princeton are now faculty or staff scientists themselves. Lyman Page, Princeton’s James S. McDonnell Distinguished University Professor in Physics, was the former principal investigator of ACT.

This research will be presented at “Future Science with CMB x LSS,” a conference running from April 10-14 at Yukawa Institute for Theoretical Physics, Kyoto University. The pre-print articles highlighted here will appear on the open-access arXiv.org. They have been submitted to the Astrophysical Journal. This work was supported by the U.S. National Science Foundation (AST-0408698, AST-0965625 and AST-1440226 for the ACT project, as well as awards PHY-0355328, PHY-0855887 and PHY-1214379), Princeton University, the University of Pennsylvania, and a Canada Foundation for Innovation award. Team members at the University of Cambridge were supported by the European Research Council.