Researchers Use Galaxy as a ‘Cosmic Telescope’ to Study Heart of the Young Universe
一种独特的新乐器，加上强大的望远镜和自然界的一点帮助，使研究人员能够凝视年轻宇宙中心的银河苗圃。
After the big bang some 13.8 billion years ago, the early universe was filled with enormous clouds of neutral diffuse gas, known as Damped Lyman-α systems, or DLAs. These DLAs served as galactic nurseries, as the gasses within slowly condensed to fuel the formation of stars and galaxies. They can still be observed today, but it isn’t easy.
“DLAs are a key to understanding how galaxies form in the universe, but they are typically difficult to observe since the clouds are too diffuse and don’t emit any light themselves,” says Rongmon Bordoloi, assistant professor of physics at North Carolina State University and corresponding author of the research.
目前，天体物理学家使用类星体 - 散发光线的超大质量黑洞 - 作为“背光”来检测DLA云。尽管这种方法确实允许研究人员查明DLA位置，但来自类星体的光仅通过巨大的云作为小串，从而阻碍了衡量其总尺寸和质量的努力。
但是W.M.的首席科学家Bordoloi和John O’Meara夏威夷卡缪尔（Kamuela）的凯克天文台（Keck Persvatory）通过使用重力镜头的银河系和整体田间光谱法发现了解决问题的方法，观察了两个DLA和内部的宿主星系 - 大约在大约110亿年前，而不久之后。
博尔多洛伊说：“重力镜头的星系是指似乎伸展和变亮的星系。”“这是因为星系前面有一个重力巨大的结构，它在向我们行驶时弯曲了它的光线。因此，我们最终要查看对象的扩展版本 - 就像使用宇宙望远镜增加放大倍率并为我们提供更好的可视化。
“这是双重的：一个，背景对象遍布天空和明亮，因此很容易在对象的不同部分上读取频谱读数。第二，因为镜头扩展了对象，因此您可以探测很小的尺度。例如，如果该物体是一年的光明年，我们可以以很高的忠诚度学习小块。”
Spectrum readings allow astrophysicists to “see” elements in deep space that are not visible to the naked eye, such as diffuse gaseous DLAs and the potential galaxies within them. Normally, gathering the readings is a long and painstaking process. But the team solved that issue by performing integral field spectroscopy with the Keck Cosmic Web Imager.
Integral field spectroscopy allowed the researchers to obtain a spectrum at every single pixel on the part of the sky it targeted, making spectroscopy of an extended object on the sky very efficient. This innovation combined with the stretched and brightened gravitationally lensed galaxy allowed the team to map out the diffuse DLA gas in the sky at high fidelity. Through this method the researchers were able to determine not only the size of the two DLAs, but also that they both contained host galaxies.
“I’ve waited most of my career for this combination: a telescope and instrument powerful enough, and nature giving us a bit of lucky alignments to study not one but two DLAs in a rich new way,” O’Meara says. “It’s great to see the science come to fruition.”
顺便说一下，DLA是巨大的。直径大于17.4千座，它们的大小超过了今天的银河系大小。相比之下，130亿年前，一个典型的星系的直径少于5千座。parsec是3.26光年，一公斤的parsec是1,000 parsecs，因此穿越每个DLA的光线约为56,723年。
“But to me, the most amazing thing about the DLAs we observed is that they aren’t unique – they seem to have similarities in structure, host galaxies were detected in both, and their masses indicate that they contain enough fuel for the next generation of star formation,” Bordoloi says. “With this new technology at our disposal, we are going to be able to dig deeper into how stars formed in the early universe.”
作品出现在自然并得到了国家航空航天管理局（W.M.）的支持凯克基金会和国家科学基金会。澳大利亚研究委员会所有天空物理学的卓越卓越中心（Astro 3D）也为这项工作做出了贡献。
-Ceake-
注释编辑: An abstract follows.
“在阻尼的Lyman-α系统中解决HI，以使星星形成动力”
DOI:10.1038 / s41586 - 022 - 04616 - 1
作者：北卡罗来纳州立大学艾哈迈德·沙班（Rongmon Bordoloi）；John M. O’Meara，Luca Rizzi，Greg Doppmann，W.M。凯克天文台；密歇根大学Keren Sharon；Jane R. Rigby，NASA Goddard飞行中心；杰夫·库克（Jeff Cooke），澳大利亚斯温本技术大学和Astro 3D；Mateusz Matuszewski，D。ChristopherMartin，Patrick Morrissey，James D. Neill，Caltech；安娜·摩尔（Anna M. Moore），澳大利亚国立大学
出版：2022年5月18日自然
抽象的：
Reservoirs of dense atomic gas (primarily hydrogen), contain ~90% of the neutral gas at a redshift of 3, and contribute to 2-3% of the total baryons in the Universe. These “Damped Lyman-α systems” (so called because they absorb Lyman-α photons from within and from background sources) have been studied for decades, but only through absorption lines present in the spectra of background quasars and gamma-ray bursts. Such pencil beams do not constrain the physical extent of the systems. Here, we report integral-field spectroscopy of a bright, gravitationally lensed galaxy at a redshift of 2.7 with two foreground Damped Lyman-α systems. These systems are ≳ 238 kpc2 in extent, with column densities of neutral hydrogen varying by more than an order of magnitude on ≲3 kpc-scales. The mean column densities are ~ 1020.46 – 1020.84 cm-2 and the total DLA masses are ≳ 5.5×108 – 1.4×109 M_⊙, showing that DLAs contain the necessary fuel for the next generation of star formation, consistent with relatively massive, low-luminosity primeval galaxies at redshifts > 2.
