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1. Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument

Author

DESI Collaboration, A. G. Adame, J. Aguilar, S. Ahlen, S. Alam, G. Aldering, D. M. Alexander, R. Alfarsy, C. Allende Prieto, M. Alvarez, O. Alves, A. Anand, F. Andrade-Oliveira, E. Armengaud, J. Asorey, S. Avila, A. Aviles, S. Bailey, A. Balaguera-Antolínez, O. Ballester, C. Baltay, A. Bault, J. Bautista, J. Behera, S. F. Beltran, S. BenZvi, L. Beraldo e Silva, J. R. Bermejo-Climent, A. Berti, R. Besuner, F. Beutler, D. Bianchi, C. Blake, R. Blum, A. S. Bolton, S. Brieden, A. Brodzeller, D. Brooks, Z. Brown, E. Buckley-Geer, E. Burtin, L. Cabayol-Garcia, Z. Cai, R. Canning, L. Cardiel-Sas, A. Carnero Rosell, F. J. Castander, J. L. Cervantes-Cota, S. Chabanier, E. Chaussidon, J. Chaves-Montero, S. Chen, X. Chen, C. Chuang, T. Claybaugh, S. Cole, A. P. Cooper, A. Cuceu, T. M. Davis, K. Dawson, R. de Belsunce, R. de la Cruz, A. de la Macorra, A. de Mattia, R. Demina, U. Demirbozan, J. DeRose, A. Dey, B. Dey, G. Dhungana, J. Ding, Z. Ding, P. Doel, R. Doshi, K. Douglass, A. Edge, S. Eftekharzadeh, D. J. Eisenstein, A. Elliott, S. Escoffier, P. Fagrelius, X. Fan, K. Fanning, V. A. Fawcett, S. Ferraro, J. Ereza, B. Flaugher, A. Font-Ribera, D. Forero-Sánchez, J. E. Forero-Romero, C. S. Frenk, B. T. Gänsicke, L. Á. García, J. García-Bellido, C. Garcia-Quintero, L. H. Garrison, H. Gil-Marín, J. Golden-Marx, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, V. Gonzalez-Perez, C. Gordon, O. Graur, D. Green, D. Gruen, J. Guy, B. Hadzhiyska, C. Hahn, J. J. Han, M. M. S Hanif, H. K. Herrera-Alcantar, K. Honscheid, J. Hou, C. Howlett, D. Huterer, V. Iršič, M. Ishak, A. Jana, L. Jiang, J. Jimenez, Y. P. Jing, S. Joudaki, E. Jullo, R. Joyce, S. Juneau, N. Kizhuprakkat, N. G. Karaçaylı, T. Karim, R. Kehoe, S. Kent, A. Khederlarian, S. Kim, D. Kirkby, T. Kisner, F. Kitaura, J. Kneib, S. E. Koposov, A. Kovács, A. Kremin, A. Krolewski, B. L’Huillier, O. Lahav, A. Lambert, C. Lamman, T.-W. Lan, M. Landriau, D. Lang, J. U. Lange, J. Lasker, L. Le Guillou, A. Leauthaud, M. E. Levi, T. S. Li, E. Linder, A. Lyons, C. Magneville, M. Manera, C. J. Manser, D. Margala, P. Martini, P. McDonald, G. E. Medina, L. Medina-Varela, A. Meisner, J. Mena-Fernández, J. Meneses-Rizo, M. Mezcua, R. Miquel, P. Montero-Camacho, J. Moon, S. Moore, J. Moustakas, E. Mueller, J. Mundet, A. Muñoz-Gutiérrez, A. D. Myers, S. Nadathur, L. Napolitano, R. Neveux, J. A. Newman, J. Nie, G. Niz, P. Norberg, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, A. Palmese, P. Zhiwei, D. Parkinson, S. Penmetsa, W. J. Percival, A. Pérez-Fernández, I. Pérez-Ràfols, M. Pieri, C. Poppett, A. Porredon, F. Prada, R. Pucha, A. Raichoor, C. Ramírez-Pérez, S. Ramirez-Solano, M. Rashkovetskyi, C. Ravoux, A. Rocher, C. Rockosi, A. J. Ross, G. Rossi, R. Ruggeri, V. Ruhlmann-Kleider, C. G. Sabiu, K. Said, A. Saintonge, L. Samushia, E. Sanchez, C. Saulder, E. Schaan, E. F. Schlafly, D. Schlegel, D. Scholte, M. Schubnell, H. Seo, A. Shafieloo, R. Sharples, W. Sheu, J. Silber, F. Sinigaglia, M. Siudek, Z. Slepian, A. Smith, D. Sprayberry, L. Stephey, J. Suárez-Pérez, Z. Sun, T. Tan, G. Tarlé, R. Tojeiro, L. A. Ureña-López, R. Vaisakh, D. Valcin, F. Valdes, M. Valluri, M. Vargas-Magaña, A. Variu, L. Verde, M. Walther, B. Wang, M. S. Wang, B. A. Weaver, N. Weaverdyck, R. H. Wechsler, M. White, Y. Xie, J. Yang, C. Yèche, J. Yu, S. Yuan, H. Zhang, Z. Zhang, C. Zhao, Z. Zheng, R. Zhou, Z. Zhou, H. Zou, S. Zou, and Y. Zu

Subjects
Cosmology, Redshift surveys, Astronomy, QB1-991
Abstract

The Dark Energy Spectroscopic Instrument (DESI) was designed to conduct a survey covering 14,000 deg ^2 over 5 yr to constrain the cosmic expansion history through precise measurements of baryon acoustic oscillations (BAO). The scientific program for DESI was evaluated during a 5 month survey validation (SV) campaign before beginning full operations. This program produced deep spectra of tens of thousands of objects from each of the stellar Milky Way Survey (MWS), Bright Galaxy Survey (BGS), luminous red galaxy (LRG), emission line galaxy (ELG), and quasar target classes. These SV spectra were used to optimize redshift distributions, characterize exposure times, determine calibration procedures, and assess observational overheads for the 5 yr program. In this paper, we present the final target selection algorithms, redshift distributions, and projected cosmology constraints resulting from those studies. We also present a One-Percent Survey conducted at the conclusion of SV covering 140 deg ^2 using the final target selection algorithms with exposures of a depth typical of the main survey. The SV indicates that DESI will be able to complete the full 14,000 deg ^2 program with spectroscopically confirmed targets from the MWS, BGS, LRG, ELG, and quasar programs with total sample sizes of 7.2, 13.8, 7.46, 15.7, and 2.87 million, respectively. These samples will allow exploration of the Milky Way halo, clustering on all scales, and BAO measurements with a statistical precision of 0.28% over the redshift interval z < 1.1, 0.39% over the redshift interval 1.1 < z < 1.9, and 0.46% over the redshift interval 1.9 < z < 3.5.

Published
2024
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2. The Early Data Release of the Dark Energy Spectroscopic Instrument

Author

DESI Collaboration, A. G. Adame, J. Aguilar, S. Ahlen, S. Alam, G. Aldering, D. M. Alexander, R. Alfarsy, C. Allende Prieto, M. Alvarez, O. Alves, A. Anand, F. Andrade-Oliveira, E. Armengaud, J. Asorey, S. Avila, A. Aviles, S. Bailey, A. Balaguera-Antolínez, O. Ballester, C. Baltay, A. Bault, J. Bautista, J. Behera, S. F. Beltran, S. BenZvi, L. Beraldo e Silva, J. R. Bermejo-Climent, A. Berti, R. Besuner, F. Beutler, D. Bianchi, C. Blake, R. Blum, A. S. Bolton, S. Brieden, A. Brodzeller, D. Brooks, Z. Brown, E. Buckley-Geer, E. Burtin, L. Cabayol-Garcia, Z. Cai, R. Canning, L. Cardiel-Sas, A. Carnero Rosell, F. J. Castander, J. L. Cervantes-Cota, S. Chabanier, E. Chaussidon, J. Chaves-Montero, S. Chen, X. Chen, C. Chuang, T. Claybaugh, S. Cole, A. P. Cooper, A. Cuceu, T. M. Davis, K. Dawson, R. de Belsunce, R. de la Cruz, A. de la Macorra, J. Della Costa, A. de Mattia, R. Demina, U. Demirbozan, J. DeRose, A. Dey, B. Dey, G. Dhungana, J. Ding, Z. Ding, P. Doel, R. Doshi, K. Douglass, A. Edge, S. Eftekharzadeh, D. J. Eisenstein, A. Elliott, J. Ereza, S. Escoffier, P. Fagrelius, X. Fan, K. Fanning, V. A. Fawcett, S. Ferraro, B. Flaugher, A. Font-Ribera, J. E. Forero-Romero, D. Forero-Sánchez, C. S. Frenk, B. T. Gänsicke, L. Á. García, J. García-Bellido, C. Garcia-Quintero, L. H. Garrison, H. Gil-Marín, J. Golden-Marx, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, V. Gonzalez-Perez, C. Gordon, O. Graur, D. Green, D. Gruen, J. Guy, B. Hadzhiyska, C. Hahn, J. J. Han, M. M. S Hanif, H. K. Herrera-Alcantar, K. Honscheid, J. Hou, C. Howlett, D. Huterer, V. Iršič, M. Ishak, A. Jacques, A. Jana, L. Jiang, J. Jimenez, Y. P. Jing, S. Joudaki, R. Joyce, E. Jullo, S. Juneau, N. G. Karaçaylı, T. Karim, R. Kehoe, S. Kent, A. Khederlarian, S. Kim, D. Kirkby, T. Kisner, F. Kitaura, N. Kizhuprakkat, J. Kneib, S. E. Koposov, A. Kovács, A. Kremin, A. Krolewski, B. L’Huillier, O. Lahav, A. Lambert, C. Lamman, T.-W. Lan, M. Landriau, D. Lang, J. U. Lange, J. Lasker, A. Leauthaud, L. Le Guillou, M. E. Levi, T. S. Li, E. Linder, A. Lyons, C. Magneville, M. Manera, C. J. Manser, D. Margala, P. Martini, P. McDonald, G. E. Medina, L. Medina-Varela, A. Meisner, J. Mena-Fernández, J. Meneses-Rizo, M. Mezcua, R. Miquel, P. Montero-Camacho, J. Moon, S. Moore, J. Moustakas, E. Mueller, J. Mundet, A. Muñoz-Gutiérrez, A. D. Myers, S. Nadathur, L. Napolitano, R. Neveux, J. A. Newman, J. Nie, R. Nikutta, G. Niz, P. Norberg, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, A. Palmese, Z. Pan, D. Parkinson, S. Penmetsa, W. J. Percival, A. Pérez-Fernández, I. Pérez-Ràfols, M. Pieri, C. Poppett, A. Porredon, S. Pothier, F. Prada, R. Pucha, A. Raichoor, C. Ramírez-Pérez, S. Ramirez-Solano, M. Rashkovetskyi, C. Ravoux, A. Rocher, C. Rockosi, A. J. Ross, G. Rossi, R. Ruggeri, V. Ruhlmann-Kleider, C. G. Sabiu, K. Said, A. Saintonge, L. Samushia, E. Sanchez, C. Saulder, E. Schaan, E. F. Schlafly, D. Schlegel, D. Scholte, M. Schubnell, H. Seo, A. Shafieloo, R. Sharples, W. Sheu, J. Silber, F. Sinigaglia, M. Siudek, Z. Slepian, A. Smith, M. T. Soumagnac, D. Sprayberry, L. Stephey, J. Suárez-Pérez, Z. Sun, T. Tan, G. Tarlé, R. Tojeiro, L. A. Ureña-López, R. Vaisakh, D. Valcin, F. Valdes, M. Valluri, M. Vargas-Magaña, A. Variu, L. Verde, M. Walther, B. Wang, M. S. Wang, B. A. Weaver, N. Weaverdyck, R. H. Wechsler, M. White, Y. Xie, J. Yang, C. Yèche, J. Yu, S. Yuan, H. Zhang, Z. Zhang, C. Zhao, Z. Zheng, R. Zhou, Z. Zhou, H. Zou, S. Zou, and Y. Zu

Subjects
Astronomy data reduction, Observational cosmology, Astronomy databases, Astronomy data analysis, Astronomy software, Surveys, Astronomy, QB1-991
Abstract

The Dark Energy Spectroscopic Instrument (DESI) completed its 5 month Survey Validation in 2021 May. Spectra of stellar and extragalactic targets from Survey Validation constitute the first major data sample from the DESI survey. This paper describes the public release of those spectra, the catalogs of derived properties, and the intermediate data products. In total, the public release includes good-quality spectral information from 466,447 objects targeted as part of the Milky Way Survey, 428,758 as part of the Bright Galaxy Survey, 227,318 as part of the Luminous Red Galaxy sample, 437,664 as part of the Emission Line Galaxy sample, and 76,079 as part of the Quasar sample. In addition, the release includes spectral information from 137,148 objects that expand the scope beyond the primary samples as part of a series of secondary programs. Here, we describe the spectral data, data quality, data products, Large-Scale Structure science catalogs, access to the data, and references that provide relevant background to using these spectra.

Published
2024
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3. The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra

Author

David M. Alexander, Tamara M. Davis, E. Chaussidon, V. A. Fawcett, Alma X. Gonzalez-Morales, Ting-Wen Lan, Christophe Yèche, S. Ahlen, J. N. Aguilar, E. Armengaud, S. Bailey, D. Brooks, Z. Cai, R. Canning, A. Carr, S. Chabanier, Marie-Claude Cousinou, K. Dawson, A. de la Macorra, A. Dey, Biprateep Dey, G. Dhungana, A. C. Edge, S. Eftekharzadeh, K. Fanning, James Farr, A. Font-Ribera, J. Garcia-Bellido, Lehman Garrison, E. Gaztañaga, Satya Gontcho A Gontcho, C. Gordon, Stefany Guadalupe Medellin Gonzalez, J. Guy, Hiram K. Herrera-Alcantar, L. Jiang, S. Juneau, N. G. Karaçaylı, R. Kehoe, T. Kisner, A. Kovács, M. Landriau, Michael E. Levi, C. Magneville, P. Martini, Aaron M. Meisner, M. Mezcua, R. Miquel, P. Montero Camacho, J. Moustakas, Andrea Muñoz-Gutiérrez, Adam D. Myers, S. Nadathur, L. Napolitano, J. D. Nie, N. Palanque-Delabrouille, Z. Pan, W. J. Percival, I. Pérez-Ràfols, C. Poppett, F. Prada, César Ramírez-Pérez, C. Ravoux, D. J. Rosario, M. Schubnell, Gregory Tarlé, M. Walther, B. Weiner, S. Youles, Zhimin Zhou, H. Zou, and Siwei Zou

Subjects
Quasars, Cosmology, Observational cosmology, Astronomy, QB1-991
Abstract

A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) of the optical spectroscopic data to quantify key survey metrics. In this paper we present results from VI of the quasar survey using deep coadded SV spectra. We show that the majority (≈70%) of the main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. A nonnegligible fraction of the quasars are misidentified by the standard spectroscopic pipeline, but we show that the majority can be recovered using post-pipeline “afterburner” quasar-identification approaches. We combine these “afterburners” with our standard pipeline to create a modified pipeline to increase the overall quasar yield. At the depth of the main DESI survey, both pipelines achieve a good-redshift purity (reliable redshifts measured within 3000 km s ^−1 ) of ≈99%; however, the modified pipeline recovers ≈94% of the visually inspected quasars, as compared to ≈86% from the standard pipeline. We demonstrate that both pipelines achieve a median redshift precision and accuracy of ≈100 km s ^−1 and ≈70 km s ^−1 , respectively. We constructed composite spectra to investigate why some quasars are missed by the standard pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of “Seyfert galaxies”) and/or more dust reddened than the standard-pipeline quasars. We also show example spectra to demonstrate the overall diversity of the DESI quasar sample and provide strong-lensing candidates where two targets contribute to a single spectrum.

Published
2023
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4. The Spectroscopic Data Processing Pipeline for the Dark Energy Spectroscopic Instrument

Author

J. Guy, S. Bailey, A. Kremin, Shadab Alam, D. M. Alexander, C. Allende Prieto, S. BenZvi, A. S. Bolton, D. Brooks, E. Chaussidon, A. P. Cooper, K. Dawson, A. de la Macorra, A. Dey, Biprateep Dey, G. Dhungana, D. J. Eisenstein, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, D. Green, K. Honscheid, M. Ishak, R. Kehoe, D. Kirkby, T. Kisner, Sergey E. Koposov, Ting-Wen Lan, M. Landriau, L. Le Guillou, Michael E. Levi, C. Magneville, Christopher J. Manser, P. Martini, Aaron M. Meisner, R. Miquel, J. Moustakas, Adam D. Myers, Jeffrey A. Newman, Jundan Nie, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, A. Raichoor, C. Ravoux, A. J. Ross, E. F. Schlafly, D. Schlegel, M. Schubnell, Ray M. Sharples, Gregory Tarlé, B. A. Weaver, Christophe Yéche, Rongpu Zhou, Zhimin Zhou, and H. Zou

Subjects
Galaxy spectroscopy, High-redshift galaxies, Redshift surveys, Astronomy, QB1-991
Abstract

We describe the spectroscopic data processing pipeline of the Dark Energy Spectroscopic Instrument (DESI), which is conducting a redshift survey of about 40 million galaxies and quasars using a purpose-built instrument 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 technique and the growth rate of structure with redshift space distortions. Ten spectrographs with three cameras each disperse the light from 5000 fibers onto 30 CCDs, covering the near-UV to near-infrared (3600–9800 Å) with a spectral resolution ranging from 2000 to 5000. The DESI data pipeline generates wavelength- and flux-calibrated spectra of all the targets, along with spectroscopic classifications and redshift measurements. Fully processed data from each night are typically available to the DESI collaboration the following morning. We give details about the pipeline’s algorithms, and provide performance results on the stability of the optics, the quality of the sky background subtraction, and the precision and accuracy of the instrumental calibration. This pipeline has been used to process the DESI Survey Validation data set, and has exceeded the project’s requirements for redshift performance, with high efficiency and a purity greater than 99% for all target classes.

Published
2023
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5. Performance of the Quasar Spectral Templates for the Dark Energy Spectroscopic Instrument

Author

Allyson Brodzeller, Kyle Dawson, Stephen Bailey, Jiaxi Yu, A. J. Ross, A. Bault, S. Filbert, J. Aguilar, S. Ahlen, David M. Alexander, E. Armengaud, A. Berti, D. Brooks, E. Chaussidon, A. de la Macorra, P. Doel, K. Fanning, V. A. Fawcett, A. Font-Ribera, S. Gontcho A Gontcho, J. Guy, K. Honscheid, S. Juneau, R. Kehoe, T. Kisner, Anthony Kremin, Ting-Wen Lan, M. Landriau, Michael E. Levi, C. Magneville, Paul Martini, Aaron M. Meisner, R. Miquel, J. Moustakas, N. Palanque-Delabrouille, W. J. Percival, F. Prada, C. Ravoux, Graziano Rossi, C. Saulder, M. Siudek, Gregory Tarlé, B. A. Weaver, S. Youles, Zheng Zheng, Rongpu Zhou, and Zhimin Zhou

Subjects
Quasars, Cosmology, Observational cosmology, Redshift surveys, Astronomy, QB1-991
Abstract

Millions of quasar spectra will be collected by the Dark Energy Spectroscopic Instrument (DESI), leading to a fourfold increase in the number of known quasars. High-accuracy quasar classification is essential to tighten constraints on cosmological parameters measured at the highest redshifts DESI observes ( z > 2.0). We present spectral templates for identification and redshift estimation of quasars in the DESI Year 1 data release. The quasar templates are comprised of two quasar eigenspectra sets, trained on spectra from the Sloan Digital Sky Survey. The sets are specialized to reconstruct quasar spectral variation observed over separate yet overlapping redshift ranges and, together, are capable of identifying DESI quasars from 0.05 < z < 7.0. The new quasar templates show significant improvement over the previous DESI quasar templates regarding catastrophic failure rates, redshift precision and accuracy, quasar completeness, and the contamination fraction in the final quasar sample.

Published
2023
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6. Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

Author

DESI Collaboration, B. Abareshi, J. Aguilar, S. Ahlen, Shadab Alam, David M. Alexander, R. Alfarsy, L. Allen, C. Allende Prieto, O. Alves, J. Ameel, E. Armengaud, J. Asorey, Alejandro Aviles, S. Bailey, A. Balaguera-Antolínez, O. Ballester, C. Baltay, A. Bault, S. F. Beltran, B. Benavides, S. BenZvi, A. Berti, R. Besuner, Florian Beutler, D. Bianchi, C. Blake, P. Blanc, R. Blum, A. Bolton, S. Bose, D. Bramall, S. Brieden, A. Brodzeller, D. Brooks, C. Brownewell, E. Buckley-Geer, R. N. Cahn, Z. Cai, R. Canning, R. Capasso, A. Carnero Rosell, P. Carton, R. Casas, F. J. Castander, J. L. Cervantes-Cota, S. Chabanier, E. Chaussidon, C. Chuang, C. Circosta, S. Cole, A. P. Cooper, L. da Costa, M.-C. Cousinou, A. Cuceu, T. M. Davis, K. Dawson, R. de la Cruz-Noriega, A. de la Macorra, A. de Mattia, J. Della Costa, P. Demmer, M. Derwent, A. Dey, B. Dey, G. Dhungana, Z. Ding, C. Dobson, P. Doel, J. Donald-McCann, J. Donaldson, K. Douglass, Y. Duan, P. Dunlop, J. Edelstein, S. Eftekharzadeh, D. J. Eisenstein, M. Enriquez-Vargas, S. Escoffier, M. Evatt, P. Fagrelius, X. Fan, K. Fanning, V. A. Fawcett, S. Ferraro, J. Ereza, B. Flaugher, A. Font-Ribera, J. E. Forero-Romero, C. S. Frenk, S. Fromenteau, B. T. Gänsicke, C. Garcia-Quintero, L. Garrison, E. Gaztañaga, F. Gerardi, H. Gil-Marín, S. Gontcho A Gontcho, Alma X. Gonzalez-Morales, G. Gonzalez-de-Rivera, V. Gonzalez-Perez, C. Gordon, O. Graur, D. Green, C. Grove, D. Gruen, G. Gutierrez, J. Guy, C. Hahn, S. Harris, D. Herrera, Hiram K. Herrera-Alcantar, K. Honscheid, C. Howlett, D. Huterer, V. Iršič, M. Ishak, P. Jelinsky, L. Jiang, J. Jimenez, Y. P. Jing, R. Joyce, E. Jullo, S. Juneau, N. G. Karaçaylı, M. Karamanis, A. Karcher, T. Karim, R. Kehoe, S. Kent, D. Kirkby, T. Kisner, F. Kitaura, S. E. Koposov, A. Kovács, A. Kremin, Alex Krolewski, B. L’Huillier, O. Lahav, A. Lambert, C. Lamman, Ting-Wen Lan, M. Landriau, S. Lane, D. Lang, J. U. Lange, J. Lasker, L. Le Guillou, A. Leauthaud, A. Le Van Suu, Michael E. Levi, T. S. Li, C. Magneville, M. Manera, Christopher J. Manser, B. Marshall, Paul Martini, W. McCollam, P. McDonald, Aaron M. Meisner, J. Mena-Fernández, J. Meneses-Rizo, M. Mezcua, T. Miller, R. Miquel, P. Montero-Camacho, J. Moon, J. Moustakas, E. Mueller, Andrea Muñoz-Gutiérrez, Adam D. Myers, S. Nadathur, J. Najita, L. Napolitano, E. Neilsen, Jeffrey A. Newman, J. D. Nie, Y. Ning, G. Niz, P. Norberg, Hernán E. Noriega, T. O’Brien, A. Obuljen, N. Palanque-Delabrouille, A. Palmese, P. Zhiwei, D. Pappalardo, X. PENG, W. J. Percival, S. Perruchot, R. Pogge, C. Poppett, A. Porredon, F. Prada, J. Prochaska, R. Pucha, A. Pérez-Fernández, I. Pérez-Ràfols, D. Rabinowitz, A. Raichoor, S. Ramirez-Solano, César Ramírez-Pérez, C. Ravoux, K. Reil, M. Rezaie, A. Rocher, C. Rockosi, N. A. Roe, A. Roodman, A. J. Ross, G. Rossi, R. Ruggeri, V. Ruhlmann-Kleider, C. G. Sabiu, S. Gaines, K. Said, A. Saintonge, Javier Salas Catonga, L. Samushia, E. Sanchez, C. Saulder, E. Schaan, E. Schlafly, D. Schlegel, J. Schmoll, D. Scholte, M. Schubnell, A. Secroun, H. Seo, S. Serrano, Ray M. Sharples, Michael J. Sholl, Joseph Harry Silber, D. R. Silva, M. Sirk, M. Siudek, A. Smith, D. Sprayberry, R. Staten, B. Stupak, T. Tan, Gregory Tarlé, Suk Sien Tie, R. Tojeiro, L. A. Ureña-López, F. Valdes, O. Valenzuela, M. Valluri, M. Vargas-Magaña, L. Verde, M. Walther, B. Wang, M. S. Wang, B. A. Weaver, C. Weaverdyck, R. Wechsler, Michael J. Wilson, J. Yang, Y. Yu, S. Yuan, Christophe Yèche, H. Zhang, K. Zhang, Cheng Zhao, Rongpu Zhou, Zhimin Zhou, H. Zou, J. Zou, S. Zou, and Y. Zu

Subjects
Dark energy, Spectroscopy, Astronomical instrumentation, Spectrometers, Optical telescopes, Astronomy, QB1-991
Abstract

The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii ] doublet at 8 × 10 ^−17 erg s ^−1 cm ^−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.

Published
2022
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7. A framework to measure the properties of intergalactic metal systems with two-point flux statistics

Author

Naim Göksel Karaçaylı, Paul Martini, David H Weinberg, Vid Iršič, J Aguilar, S Ahlen, D Brooks, A de la Macorra, A Font-Ribera, S Gontcho A Gontcho, J Guy, T Kisner, R Miquel, C Poppett, C Ravoux, M Schubnell, G Tarlé, B A Weaver, Z Zhou, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
quasars: absorption lines, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, intergalactic medium, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], methods: data analysis, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The abundance, temperature, and clustering of metals in the intergalactic medium are important parameters for understanding their cosmic evolution and quantifying their impact on cosmological analysis with the Ly $\alpha$ forest. The properties of these systems are typically measured from individual quasar spectra redward of the quasar's Ly $\alpha$ emission line, yet that approach may provide biased results due to selection effects. We present an alternative approach to measure these properties in an unbiased manner with the two-point statistics commonly employed to quantify large-scale structure. Our model treats the observed flux of a large sample of quasar spectra as a continuous field and describes the one-dimensional, two-point statistics of this field with three parameters per ion: the abundance (column density distribution), temperature (Doppler parameter) and clustering (cloud-cloud correlation function). We demonstrate this approach on multiple ions (e.g., C IV, Si IV, Mg II) with early data from the Dark Energy Spectroscopic Instrument (DESI) and high-resolution spectra from the literature. Our initial results show some evidence that the C IV abundance is higher than previous measurements and evidence for abundance evolution over time. The first full year of DESI observations will have over an order of magnitude more quasar spectra than this study. In a future paper we will use those data to measure the growth of clustering and its impact on the Ly $\alpha$ forest, as well as test other DESI analysis infrastructure such as the pipeline noise estimates and the resolution matrix., Comment: 15 pages, 14 figures, accepted to MNRAS

Published
2023
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8. The Spectroscopic Data Processing Pipeline for the Dark Energy Spectroscopic Instrument

Author

J. Guy, S. Bailey, A. Kremin, Shadab Alam, D. M. Alexander, C. Allende Prieto, S. BenZvi, A. S. Bolton, D. Brooks, E. Chaussidon, A. P. Cooper, K. Dawson, A. de la Macorra, A. Dey, Biprateep Dey, G. Dhungana, D. J. Eisenstein, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, D. Green, K. Honscheid, M. Ishak, R. Kehoe, D. Kirkby, T. Kisner, Sergey E. Koposov, Ting-Wen Lan, M. Landriau, L. Le Guillou, Michael E. Levi, C. Magneville, Christopher J. Manser, P. Martini, Aaron M. Meisner, R. Miquel, J. Moustakas, Adam D. Myers, Jeffrey A. Newman, Jundan Nie, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, A. Raichoor, C. Ravoux, A. J. Ross, E. F. Schlafly, D. Schlegel, M. Schubnell, Ray M. Sharples, Gregory Tarlé, B. A. Weaver, Christophe Yéche, Rongpu Zhou, Zhimin Zhou, H. Zou, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), DESI, and Ministerio de Ciencia e Innovación (España)

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Space and Planetary Science, astro-ph.CO, FOS: Physical sciences, Astronomy and Astrophysics, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), astro-ph.IM, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Full list of authors: Guy, J.; Bailey, S.; Kremin, A.; Alam, Shadab; Alexander, D. M.; Allende Prieto, C.; BenZvi, S.; Bolton, A. S.; Brooks, D.; Chaussidon, E.; Cooper, A. P.; Dawson, K.; de la Macorra, A.; Dey, A.; Dey, Biprateep; Dhungana, G.; Eisenstein, D. J.; Font-Ribera, A.; Forero-Romero, J. E.; Gaztanaga, E.; Gontcho, S. Gontcho A.; Green, D.; Honscheid, K.; Ishak, M.; Kehoe, R.; Kirkby, D.; Kisner, T.; Koposov, Sergey E.; Lan, Ting-Wen; Landriau, M.; Le Guillou, L.; Levi, Michael E.; Magneville, C.; Manser, Christopher J.; Martini, P.; Meisner, Aaron M.; Miquel, R.; Moustakas, J.; Myers, Adam D.; Newman, Jeffrey A.; Nie, Jundan; Palanque-Delabrouille, N.; Percival, W. J.; Poppett, C.; Prada, F.; Raichoor, A.; Ravoux, C.; Ross, A. J.; Schlafly, E. F.; Schlegel, D.; Schubnell, M.; Sharples, Ray M.; Tarle, Gregory; Weaver, B. A.; Yeche, Christophe; Zhou, Rongpu; Zhou, Zhimin; Zou, H.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We describe the spectroscopic data processing pipeline of the Dark Energy Spectroscopic Instrument (DESI), which is conducting a redshift survey of about 40 million galaxies and quasars using a purpose-built instrument 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 technique and the growth rate of structure with redshift space distortions. Ten spectrographs with three cameras each disperse the light from 5000 fibers onto 30 CCDs, covering the near-UV to near-infrared (3600–9800 Å) with a spectral resolution ranging from 2000 to 5000. The DESI data pipeline generates wavelength- and flux-calibrated spectra of all the targets, along with spectroscopic classifications and redshift measurements. Fully processed data from each night are typically available to the DESI collaboration the following morning. We give details about the pipeline's algorithms, and provide performance results on the stability of the optics, the quality of the sky background subtraction, and the precision and accuracy of the instrumental calibration. This pipeline has been used to process the DESI Survey Validation data set, and has exceeded the project's requirements for redshift performance, with high efficiency and a purity greater than 99% for all target classes. © 2023. The Author(s). Published by the American Astronomical Society., This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under contract No. DEAC0205CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN); and the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Source data files for the plots are archived at 10.5281/zenodo.7087815., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

Published
2022
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11. Interstitial nitrogen atoms in diamond. A quantum mechanical investigation of its electronic and vibrational properties.

Author

Salustro S, Pascale F, Mackrodt WC, Ravoux C, Erba A, and Dovesi R

Abstract

The electronic and vibrational features of the single- (I1N) and double- (I2N) nitrogen interstitial defects in diamond are investigated at the quantum mechanical level using a periodic supercell approach based on hybrid functionals constructed from all electron Gaussian basis sets within the Crystal code. The results are compared with those of the well characterized 100 split self-interstitial defect (I2C). The effect of defect concentration has been investigated using supercells with different size, containing 64 and 216 atoms. Band structure, formation energy, charge and spin density distributions of each defect are analyzed. Irrespective of the defect concentration, these defects show important features for both IR and Raman spectroscopies. Stretching modes of the two atoms involved in the defect are calculated to be around 1837, 1761 and 1897 cm-1 for the I1N, I2N and I2C case, respectively. Since they are well removed from the one-phonon mode of pristine diamond (1332 cm-1), they are, in principle, detectable from the experimental point of view.

Published
2018
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