Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session H13: DESI Special SessionRecordings Available
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Sponsoring Units: DAP DPF Chair: Satya Gontcho A Gontcho, Berkeley Lab Room: Empire |
Sunday, April 10, 2022 10:45AM - 10:57AM |
H13.00001: Status of the DESI Instrument and Spectroscopic Pipeline Anthony Kremin The Dark Energy Spectroscopic Instrument (DESI) is composed of 5000 robotically positioned optical fibers mounted on the 4m KPNO Mayall TeIescope that transmit light to ten broad-band spectrographs. Since beginning Survey Validation just over one year ago, DESI has already acquired the spectra of millions of objects, forming one of the largest astronomical spectroscopic datasets from a single instrument to date. In this talk we will discuss the instrument, its capabilities, and the software developed to control its operation and process the data within hours of acquisition for the rapid assessment of data quality and uniformity. |
Sunday, April 10, 2022 10:57AM - 11:09AM |
H13.00002: DESI Emission Line Galaxies: Redshift Surveys of the 2020s Anand Raichoor Emission Line Galaxies (ELGs) are abundant at z=1-2 and today's experiments are able to measure their spectroscopic redshift despite their faintness, thanks to the presence of emission lines. |
Sunday, April 10, 2022 11:09AM - 11:21AM |
H13.00003: DESI Bright Galaxy Survey: Design and Validation ChangHoon Hahn Over the next five years, the Dark Energy Spectroscopic Instrument (DESI) will use a 5000-fiber spectrograph on the 4-meter Mayall Telescope at Kitt Peak National Observatory to realize the first Stage-IV Dark Energy galaxy survey. At z < 0.6, the DESI Bright Galaxy Survey (BGS) will produce the most detailed map of the Universe during the Dark Energy dominated epoch with >10 million galaxies spanning >9000 deg^2. In this talk, I will present the final target selection, design, and strategy of BGS. Furthermore, I will demonstrate using early observations conducted prior to the main survey that BGS will successfully complete its strategy and make optimal use of 'bright' time when the moon is above the horizon. Finally, I will discuss the extensive range of scientific applications that BGS will unlock. BGS will yield the most precise Baryon Acoustic Oscillations and Redshift-Space Distortions (RSD) measurements to probe Dark Energy at z < 0.4 to date. It also presents a unique opportunity to exploit new methods that require highly complete and dense galaxy samples, e.g. N-point statistics, multi-tracer RSD. BGS further provides a powerful tool to study galaxy populations including dwarf galaxies, galaxy groups and clusters, and the relations between galaxies and dark matter. |
Sunday, April 10, 2022 11:21AM - 11:33AM |
H13.00004: Early Galaxy and Quasar Science from Millions of DESI Spectra John Moustakas The Dark Energy Spectroscopic Instrument (DESI) survey has obtained observed-frame optical spectrophotometry for millions of galaxies and quasars at 0<z<4, making it among the largest datasets of extragalactic sources ever assembled. The sheer size and quality of the DESI survey data will yield transformative insights into the formation and evolution of galaxies and quasars, as well as on the physics of the baryon cycle over eighty percent of cosmic time. In this contribution, we highlight some of the initial science results from the first year of DESI observations, including work on the star formation and nuclear activity in low-mass galaxies; the stellar mass-metallicity relation; post-starburst galaxies; the content and velocity structure of the circumgalactic medium; and more. |
Sunday, April 10, 2022 11:33AM - 11:45AM |
H13.00005: First measurements of Lyman alpha correlations from DESI Satya Gontcho A Gontcho, Ignasi Pérez Ràfols Baryon Acoustic Oscillations (BAO) can be measured at high redshift (z~2-3) using the Lyman alpha forest of quasar spectra. |
Sunday, April 10, 2022 11:45AM - 11:57AM |
H13.00006: Cosmological Constraints from Cross-Correlation of Planck CMB lensing and DESI-like Emission-Line Galaxies in Legacy Surveys Tanveer Karim, Sukhdeep Singh, Mehdi Rezaie, Boryana Hadzhiyska, Daniel J Eisenstein Understanding the cause of the cosmic acceleration is one of the outstanding questions in physics. While dark energy is the leading explanation, its exact nature is unknown, and theories such as modified gravity also offer alternative explanations. A complementary probe to studying dark energy and modified gravity theories is via measuring the growth of structure. The high redshift emission-line galaxies (ELGs) in particular trace the growth of structure in an era when the dark energy density was not significant and consequently can serve as an ideal testing ground for modified gravity theories. In this project, we select DESI-like ELGs from the Legacy Surveys DR9 imaging data and cross-correlate their positions with the Planck 2018 CMB lensing map to measure the growth of structure, linear bias, and matter density in tomographic bins 0.6 < z < 1.1 and 1.1 < z < 1.6. We conduct a full 3 X 2 analysis (Cgg, Cκκ, Cκg) and account for imaging systematics in the final cosmological inferences. We further calibrate the ELG photometric redshifts using the DESI Survey Validation dataset. In the talk, I will specifically discuss our final measurements and how the same framework can be used by the upcoming galaxy and CMB lensing surveys to provide robust cosmological constraints. |
Sunday, April 10, 2022 11:57AM - 12:09PM |
H13.00007: DESI Mock Challenge: Preparing DESI Pipeline for LSS analysis Mariana Vargas In this talk I will describe the DESI Mock Challenge. DESI is a multi-object spectrograph currently collecting the largest data set of galaxy/quasar spectrum ever assembled. It is expected to provide the most precise measurement of dark energy. To achieve this, it is paramount that the accuracy of the data analysis pipeline is robust(i.e. systematics error is less than the statistical error) compared with previous stage III experiments. That is why we need to thoroughly validate all the pieces of the pipeline. The goal of the Mock Challenge is to build the analysis pipeline to extract cosmological information from the large-scale structure of galaxy clustering. We study the accuracy and precision of the main observables for DESI. We compare and cross-validate codes from different groups to build the pipeline and use state-of-art simulations to validate them. The mock challenge covers three main challenges: 1) Covariances 2) BAO and Reconstruction and 3) RSD and Full Shape Analysis . I will present briefly the methodology, the goals, the preliminary results and the near future plans. |
Sunday, April 10, 2022 12:09PM - 12:21PM |
H13.00008: The Role of DESI in Photo-z Inference for LSST, Euclid, and Future Cosmological Surveys Jamie McCullough We present the results of the DESI Complete Calibration of the Color-Redshift Relation (DC3R2) secondary target survey. The spectroscopic galaxies observed during DESI Science Verification, augmented by DC3R2, that overlap with KiDS-VIKING ugriZYHJKs photometry calibrate the color-redshift relationship and inform photometric redshift (photo-z) inference methods in future weak lensing surveys. With Emission Line Galaxies (ELGs) and Luminous Red Galaxies (LRGs) that provide a complementary color sample, we conservatively span 50% of the color space visible to Euclid and LSST. Examination of the redshift dependence on magnitude at fixed colors will provide a constraint on the use of preferentially bright spectra to calibrate redshifts in a correspondingly fainter photometric sample, which is deeply relevant to the next decade of anticipated, unprecedented survey depth. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self Organizing Maps trained on different photometry than the analysis sample. |
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