DESI: The Dark Energy Spectroscopic Instrument

暗能量光谱仪（DESI）是一种大规模多路复用光纤光谱仪，将在2019-2023年的时间框架内实现基础宇宙学研究的下一个重大进展。在Mayall望远镜上，DESI将获得至少1800万个发射线星系、400万个发光红色星系和300万个准恒星物体的光谱和红移。DESI将：（i）探测暗能量对使用重子声学振荡的膨胀历史的影响，（ii）测量通过红移空间扭曲的引力增长历史，（iii）测量中微子质量的总和，（iv）调查宇宙膨胀的签名通过原始非高斯。由此产生的z 2的3-D星系图< 2 and Lyman-alpha forest at z >将在35个红移箱中对距离尺度进行1%水平的测量;与现有数据相比，这将使宇宙学约束的精度提高近一个数量级，并且至少比目前计划的竞争对手实验的结果好三倍。DESI将在欧几里得之前开始，将通过提供基本的相对较低和较高的红移数据点来补充其红移测量范围，并将改进弱透镜测光红移的欧几里得校准。利用DESI还可以进行广泛的其他科学研究，包括星系演化研究，星系团调查，银河系的结构和银河系考古学。我们建议STFC使具有相关技术和科学专业知识的英国科学家核心小组加入DESI合作，并在这项实验中发挥主导作用，使用与加入成功的暗能量调查（DES）项目类似的策略。DES将根据成像数据和光度红移对DESI进行补充测量，这些测量明显弱于基于光谱学的测量。通过建立在公认的英国在大型光学和高度复用光纤系统技术方面的优势，这笔核心资金将使英国在光学校正器和光纤系统工作包中发挥领先的技术作用，从而可以在DESI项目的科学领导地位及其调查数据产品的分析中获得强大的杠杆作用。这是一个英国小组已经建立了跟踪记录的领域，例如在开发2度场星系红移巡天方面。DESI是从BigBOSS和DESpec研究合并而来的一个实验，并将建立在STFC资助的两个项目的可行性研究基础上。它汇集了来自粒子物理学和天文学社区的团队，拥有20多年的此类项目合作经验。DESI比DES或重子振荡光谱测量（BOSS）前体实验更强（分别导致DESpec和BigBOSS），并将利用这一遗产组织参与的科学家和工程师的大规模合作，英国科学家在该组织中发挥关键作用。通过这一提议，STFC有机会支持英国天文技术的关键领域，并使英国科学卓越的战略重要领域在这个独特的宇宙学实验。我们请求主要支持由UCL和达勒姆大学领导的关于光学校正器和光纤系统的技术工作包，以及与科学工作组和DESI进展会议相关的项目特定旅行。我们将通过我们的STFC合并赠款单独寻求对科学开发的支持。为了给英国带来最大利益，我们建议提供280万英镑的支持，这将使参与大规模结构研究的四个英国领先团体（朴茨茅斯、达勒姆、爱丁堡和伦敦大学学院）的科学家能够充分参与，并确保调查科学产品也与更广泛的英国优先事项保持一致。

The Dark Energy Spectroscopic Instrument (DESI) is a massively multiplexed fibre-fed spectrograph that will make the next major advance in Fundamental Cosmology research in the timeframe 2019-2023. On the Mayall telescope, DESI will obtain spectra and redshifts for at least 18 million emission-line galaxies, 4 million luminous red galaxies and 3 million quasi-stellar objects. DESI will: (i) probe the effects of Dark Energy on the expansion history using baryon acoustic oscillations, (ii) measure the gravitational growth history through redshift-space distortions, (iii) measure the sum of neutrino masses, and (iv) investigate the signatures of cosmological inflation via primordial non-Gaussianity. The resulting 3-D galaxy maps at z < 2 and Lyman-alpha forest at z > 2 will make 1%-level measurements of the distance scale in 35 redshift bins; this will improve the precision of cosmological constraints by almost an order of magnitude compared to existing data, and be at least three times better than any result from currently planned competitor experiments. DESI will start before Euclid, will complement its redshift survey range by providing essential comparative lower and higher redshift data points, and will improve the Euclid calibrations of weak-lensing photometric redshifts. A wide range of additional science will also be possible using DESI including the study of galaxy evolution, galaxy cluster surveys, the structure of the Milky-Way galaxy and Galactic archaeology.We propose that STFC enables a core group of UK scientists with relevant technical and scientific expertise to join the DESI collaboration and take a leading role in this experiment, using a similar strategy to that adopted to join the successful Dark Energy Survey (DES) project. DES will make complementary measurements to DESI, based on imaging data and photometric redshifts, which are significantly weaker than those based on spectroscopy. By building on acknowledged UK strengths in the technologies of large optics and highly multiplexed fibre systems, this core funding will enable leading UK technical roles in the optical corrector and fibre system work packages, from which strong leverage can be secured in the scientific leadership of the DESI project and the analysis of its survey data products. This is an area where UK groups have an established track record, for example in exploitation of the 2-degree Field Galaxy Redshift Survey.DESI is an experiment that grew from the merger of the BigBOSS and DESpec studies, and will build upon STFC-funded feasibility studies for both projects. It brings together a team of people from both the particle physics and astronomy communities, with over 20 years of experience of working together on such projects. DESI is stronger than either the DES or the Baryon Oscillation Spectroscopic Survey (BOSS) pre-cursor experiments (which led to DESpec and BigBOSS respectively) and will utilise this heritage to organise the large collaboration of scientists and engineers involved, with UK scientists playing a key role in that organisation.With this proposal, STFC has the opportunity to support key areas of UK astronomy technology, and to enable strategically important areas of UK scientific excellence in this unique cosmological experiment. We request support primarily for the technical work-packages led by UCL and Durham University on the optical corrector and optical fibre system, and for project-specific travel associated with the science working groups and DESI progress meetings. We will seek support for science exploitation separately through our STFC consolidated grants. For optimum benefit to the UK, we propose support at the level of £2.8M which will enable full participation from scientists in four of the leading UK groups involved in large-scale structure studies (Portsmouth, Durham, Edinburgh and UCL) and ensure that the survey science products are also well aligned with wider UK priorities.