Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session U14: Large Scale Structure Surveys: Updates from DESI and Other Projects |
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Sponsoring Units: DAP Chair: Richard Holmes, Boeing Company (retired) Room: Marquette V - 2nd Floor |
Tuesday, April 18, 2023 1:30PM - 1:42PM |
U14.00001: DESI: Early Data Release and project update Anand Raichoor The Dark Energy Spectroscopic Instrument (DESI) is an on-going Stage IV experiment, which will map the Universe up to z=3.5 with 40 million redshift measurements. I will present the content of the Early Data Release (EDR), the current status of the instrument and of the Main Survey. The EDR contains more than one million redshifts taken from Dec. 2020 to May 2021., which have been used to finalize and validate the Main Survey design. The Main Survey started in May 2021, and has already gathered more than 20 million redshifts. I will present the various performed data-quality assessments, which ensures that the provided redshifts can be used for the DESI science. |
Tuesday, April 18, 2023 1:42PM - 1:54PM |
U14.00002: First Detection of the BAO Signal from Early DESI Data Michael Rashkovetskyi, Graziano Rossi, Jeongin Moon, Christoph Saulder, David Valcin, Nikhil Padmanabhan, Hee-Jong Seo, Arnaud de Mattia, Ashley J Ross We present the detection of the baryon acoustic oscillations (BAO) signal using unblinded data collected during the initial two months of operations of the Stage-IV ground-based Dark Energy Spectroscopic Instrument (DESI). From 261,291 Luminous Red Galaxies spanning redshifts 0.4 < z < 1.1 and 1651 sq. deg. with a 57.9% completeness, we report a 5σ level BAO detection at a precision of 1.7%. Using 630,480 Bright Galaxy Sample over 0.1 < z < 0.5, 3677 sq. deg. with a 50.0% completeness, we also detect the BAO feature at 3σ significance with a 2.6% precision. These are an important milestone which confirms the choice of the survey design, quality performance of the complex robotically-actuated, fiber-fed DESI spectrograph, validates the spectroscopic pipeline and data management system. Based on these first promising results, we forecast that DESI is on target to achieve a high-significance BAO detection at a sub-percent accuracy with the completed 5-year survey data, meeting the Level 1 science requirements on BAO measurement precision. This will set novel standards in cosmology, and confirm DESI as one of the most competitive Stage-IV BAO experiments for large-scale spectroscopic surveys for the remainder of this decade. |
Tuesday, April 18, 2023 1:54PM - 2:06PM |
U14.00003: DESI Early Data Release: Galaxy-Dark-Matter-Halo Connection Jiaxi Yu The connection between dark matter haloes and galaxies describes the galaxy formation process in the dark matter field. It is crucial for modelling galaxy clustering on small scales and constructing high-fidelity large-scale simulations for galaxies. The Early Data Release (EDR) of DESI is a powerful dataset for understanding this galaxy-halo relation down to megaparsec scales, with the help of modern large-volume and high-resolution dark matter simulations. The DESI EDR sample consists of luminous red galaxies (LRGs), emission line galaxies (ELGs), and quasi-stellar objects (QSOs) in a redshift range of [0.4, 3.5], taken by the Mayall 4-m telescope in a few months, with a similar number density as the SDSS eBOSS data accumulated in 4 years. We analyze the galaxy-halo connection of DESI EDR with UNIT N-body simulations and a general subhalo abundance matching (SHAM) algorithm. This algorithm works for all three tracers and takes into account observational systematics like redshift uncertainty and stellar mass completeness. We detect the quenching of ELG star formation and QSO black-hole activity in a dense environment, and massive LRGs are found to be complete. The redshift uncertainty plays a role for LRGs and QSOs at 10-20Mpc/h but ELGs are immune to it on megaparsec scales. Similar studies using different SHAM and halo occupation distribution (HOD) methods and with alternative simulations report more properties of the DESI tracer. For instance, the average number of satellites of LRGs and QSOs increases as their host halo mass, while ELG satellites illustrate the opposite trend. In addition, there is no evidence of assembly bias for LRGs and QSOs. Besides, DESI ELGs do not include the most luminous OII emitters for z<0.8. |
Tuesday, April 18, 2023 2:06PM - 2:18PM |
U14.00004: The DESI Peculiar Velocity Survey Kelly Douglass The Dark Energy Spectroscopic Instrument (DESI) Peculiar Velocity Survey is a secondary targeting program of the DESI main survey designed to systematically measure peculiar motion at z < 0.2. The Peculiar Velocity (PV) Survey combines the spectroscopic galaxy redshifts recorded by DESI with standardizable distance measurements from elliptical and spiral galaxies in the DESI Bright Galaxy Survey (BGS). Over the next few years, the DESI PV Survey will produce the largest catalog of peculiar velocities ever assembled, comprising more than 400,000 Fundamental Plane distances of elliptical galaxies in the BGS and more than 125,000 Tully-Fisher distances of disc galaxies in the Siena Galaxy Atlas. These measurements will offer a unique perspective on the mass and motions in the low redshift Universe and allow precision tests of gravity and dark energy. We describe the target selection of the PV survey and present preliminary results recorded during the first year of DESI observations. |
Tuesday, April 18, 2023 2:18PM - 2:30PM |
U14.00005: Early Results Using the Lyman-alpha Forest in DESI Abby Bault The Dark Energy Spectroscopic Instrument (DESI) is a multi-object spectrograph on the 4-m Mayall Telescope at Kitt Peak National Observatory. The main goal of DESI is to measure with unprecedented precision the expansion history of the Universe with the Baryon Acoustic Oscillation (BAO) technique and the growth rate of structure with Redshift Space Distortions. |
Tuesday, April 18, 2023 2:30PM - 2:42PM |
U14.00006: Cosmology beyond BAO from the 3D distribution of the Lyman-α forest measured by DESI Andrei Cuceu The Lyman-α (Lyα) forest is currently one of the most powerful probes of large-scale structure (LSS) at high redshift (z > 2). The Dark Energy Spectroscopic Instrument (DESI) is in the process of observing about one million forests, giving us unprecedented access to the distribution of neutral hydrogen in the high redshift Universe. While previous surveys have focused on measuring baryon acoustic oscillations (BAO) from this 3D distribution, we are now working towards extracting more information (beyond BAO) with DESI. In this talk I will show how we can use the full shape of the Lyα forest auto-correlation and its cross-correlation with quasars to improve constraints on the cosmic expansion rate through the Alcock-Paczynski (AP) effect, and measure the linear growth rate of structure from redshift space distortions (RSD). We have recently used extended Baryon Oscillation Spectroscopic Survey (eBOSS) data to measure the AP effect from the full shapes of Lyα correlations and found that it provides a factor of two tighter constraints compared to BAO analyses. Finally, I will show forecasts of Lyα forest full-shape measurements from DESI. |
Tuesday, April 18, 2023 2:42PM - 2:54PM |
U14.00007: Systematic study of projection biases in weak lensing analysis Prudhvi Raj Varma Chintalapati, Gaston R Gutierrez, Michael H Wang We present a systematic study of projection biases in the weak lensing analysis of the first year of data from the Dark Energy Survey (DES) experiment. In the analysis, we used a ΛCDM cosmology model and the three two-point correlation functions: (i) the cosmic shear correlation function, (ii) the galaxy angular correlation function (galaxy clustering), and (iii) the galaxy-shear cross-correlation function (galaxy-galaxy lensing). We show that the projection biases are a consequence of projecting or marginalizing, over parameters like h, Ωb, ns, and Ωνh2 that have wide likelihoods with respect to their priors (poorly constrained) and correlated with the parameters of interest like Ωm, σ8, and S8. Covering the relevant parameter space, we show that the projection biases are a function of where the true values of the poorly constrained parameters lie with respect to the parameter priors. We also show that the one-dimensional credible intervals are consistently inflated and discuss how careful study of these biases could transform the WL analysis credible intervals into confidence intervals with an equivalent gain of up to three times the data available for the experiment. |
Tuesday, April 18, 2023 2:54PM - 3:06PM Withdrawn |
U14.00008: Journey of galaxies through large scale structures Miguel Correa, Ali Snedden, Guobao Tang, Quynh Lan Q Nguyen, Lara A Phillips There exists a complex relationship between galaxies and their surroundings. It has been shown that certain galaxy shapes are dominant in different large-scale cosmic environments, such as the tendency of elliptical galaxies to dominate in clusters. Furthermore, previous studies suggest that these galaxies may undergo a morphological transition as they pass from one large-scale environment to the next. Specifically, this evolution may be influenced by the type of galaxy-galaxy interactions (fly-bys, mergers) and galaxy-medium interactions (collision with gas, disruption by collective dark matter potential). For this reason, it is interesting to know where galaxies are located throughout time. In this talk, I will present our simulation work in examining the history of galaxies as they move through different cosmic environments. In particular, we identify large-scale structures and galaxy trajectories within simulations produced by a modified SPH Gadget 2 code, as well as the publicly available IllustrisTNG data sets. |
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