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DESI DR1 Ly$α$ 1D power spectrum: Validation of estimators

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Main Authors:	Karaçaylı, N. G., Ravoux, C., Martini, P., Goff, J. M. Le, Armengaud, E., Abdul-Karim, M., Aguilar, J., Ahlen, S., Anand, A., BenZvi, S., Bianchi, D., Brooks, D., Claybaugh, T., Cuceu, A., de la Macorra, A., Dey, Biprateep, Doel, P., Ferraro, S., Font-Ribera, A., Forero-Romero, J. E., Gaztañaga, E., Gontcho, S. Gontcho A, Gutierrez, G., Herrera-Alcantar, H. K., Honscheid, K., Ishak, M., Jimenez, J., Joyce, R., Kirkby, D., Kisner, T., Kremin, A., Lahav, O., Landriau, M., Guillou, L. Le, Manera, M., Meisner, A., Miquel, R., Nadathur, S., Niz, G., Palanque-Delabrouille, N., Percival, W. J., Poppett, C., Prada, F., Pérez-Ràfols, I., Rossi, G., Sanchez, E., Schlegel, D., Schubnell, M., Seo, H., Silber, J., Sprayberry, D., Tan, T., Tarlé, G., Walther, M., Weaver, B. A., Zou, H.
Format:	Preprint
Published:	2025
Subjects:	Cosmology and Nongalactic Astrophysics
Online Access:	Acceder al recurso
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author	Karaçaylı, N. G. Ravoux, C. Martini, P. Goff, J. M. Le Armengaud, E. Abdul-Karim, M. Aguilar, J. Ahlen, S. Anand, A. BenZvi, S. Bianchi, D. Brooks, D. Claybaugh, T. Cuceu, A. de la Macorra, A. Dey, Biprateep Doel, P. Ferraro, S. Font-Ribera, A. Forero-Romero, J. E. Gaztañaga, E. Gontcho, S. Gontcho A Gutierrez, G. Herrera-Alcantar, H. K. Honscheid, K. Ishak, M. Jimenez, J. Joyce, R. Kirkby, D. Kisner, T. Kremin, A. Lahav, O. Landriau, M. Guillou, L. Le Manera, M. Meisner, A. Miquel, R. Nadathur, S. Niz, G. Palanque-Delabrouille, N. Percival, W. J. Poppett, C. Prada, F. Pérez-Ràfols, I. Rossi, G. Sanchez, E. Schlegel, D. Schubnell, M. Seo, H. Silber, J. Sprayberry, D. Tan, T. Tarlé, G. Walther, M. Weaver, B. A. Zou, H.
author_facet	Karaçaylı, N. G. Ravoux, C. Martini, P. Goff, J. M. Le Armengaud, E. Abdul-Karim, M. Aguilar, J. Ahlen, S. Anand, A. BenZvi, S. Bianchi, D. Brooks, D. Claybaugh, T. Cuceu, A. de la Macorra, A. Dey, Biprateep Doel, P. Ferraro, S. Font-Ribera, A. Forero-Romero, J. E. Gaztañaga, E. Gontcho, S. Gontcho A Gutierrez, G. Herrera-Alcantar, H. K. Honscheid, K. Ishak, M. Jimenez, J. Joyce, R. Kirkby, D. Kisner, T. Kremin, A. Lahav, O. Landriau, M. Guillou, L. Le Manera, M. Meisner, A. Miquel, R. Nadathur, S. Niz, G. Palanque-Delabrouille, N. Percival, W. J. Poppett, C. Prada, F. Pérez-Ràfols, I. Rossi, G. Sanchez, E. Schlegel, D. Schubnell, M. Seo, H. Silber, J. Sprayberry, D. Tan, T. Tarlé, G. Walther, M. Weaver, B. A. Zou, H.
contents	The Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) is the largest sample to date for small-scale Ly$α$ forest cosmology, accessed through its one-dimensional power spectrum ($P_{\mathrm{1D}}$). The Ly$α$ forest $P_{\mathrm{1D}}$ is extracted from quasar spectra that are highly inhomogeneous (both in wavelength and between quasars) in noise properties due to intrinsic properties of the quasar, atmospheric and astrophysical contamination, and also sensitive to low-level details of the spectral extraction pipeline. We employ two estimators in DR1 analysis to measure $P_{\mathrm{1D}}$: the optimal estimator and the fast Fourier transform (FFT) estimator. To ensure robustness of our DR1 measurements, we validate these two power spectrum and covariance matrix estimation methodologies against the challenging aspects of the data. First, using a set of 20 synthetic 1D realizations of DR1, we derive the masking bias corrections needed for the FFT estimator and the continuum fitting bias needed for both estimators. We demonstrate that both estimators, including their covariances, are unbiased with these corrections using the Kolmogorov-Smirnov test. Second, we substantially extend our previous suite of CCD image simulations to include 675,000 quasars, allowing us to accurately quantify the pipeline's performance. This set of simulations reveals biases at the highest $k$ values, corresponding to a resolution error of a few percent. We base the resolution systematics error budget of DR1 $P_{\mathrm{1D}}$ on these values, but do not derive corrections from them since the simulation fidelity is insufficient for precise corrections.
format	Preprint
id	arxiv_https___arxiv_org_abs_2509_13593
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	DESI DR1 Ly$α$ 1D power spectrum: Validation of estimators Karaçaylı, N. G. Ravoux, C. Martini, P. Goff, J. M. Le Armengaud, E. Abdul-Karim, M. Aguilar, J. Ahlen, S. Anand, A. BenZvi, S. Bianchi, D. Brooks, D. Claybaugh, T. Cuceu, A. de la Macorra, A. Dey, Biprateep Doel, P. Ferraro, S. Font-Ribera, A. Forero-Romero, J. E. Gaztañaga, E. Gontcho, S. Gontcho A Gutierrez, G. Herrera-Alcantar, H. K. Honscheid, K. Ishak, M. Jimenez, J. Joyce, R. Kirkby, D. Kisner, T. Kremin, A. Lahav, O. Landriau, M. Guillou, L. Le Manera, M. Meisner, A. Miquel, R. Nadathur, S. Niz, G. Palanque-Delabrouille, N. Percival, W. J. Poppett, C. Prada, F. Pérez-Ràfols, I. Rossi, G. Sanchez, E. Schlegel, D. Schubnell, M. Seo, H. Silber, J. Sprayberry, D. Tan, T. Tarlé, G. Walther, M. Weaver, B. A. Zou, H. Cosmology and Nongalactic Astrophysics The Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) is the largest sample to date for small-scale Ly$α$ forest cosmology, accessed through its one-dimensional power spectrum ($P_{\mathrm{1D}}$). The Ly$α$ forest $P_{\mathrm{1D}}$ is extracted from quasar spectra that are highly inhomogeneous (both in wavelength and between quasars) in noise properties due to intrinsic properties of the quasar, atmospheric and astrophysical contamination, and also sensitive to low-level details of the spectral extraction pipeline. We employ two estimators in DR1 analysis to measure $P_{\mathrm{1D}}$: the optimal estimator and the fast Fourier transform (FFT) estimator. To ensure robustness of our DR1 measurements, we validate these two power spectrum and covariance matrix estimation methodologies against the challenging aspects of the data. First, using a set of 20 synthetic 1D realizations of DR1, we derive the masking bias corrections needed for the FFT estimator and the continuum fitting bias needed for both estimators. We demonstrate that both estimators, including their covariances, are unbiased with these corrections using the Kolmogorov-Smirnov test. Second, we substantially extend our previous suite of CCD image simulations to include 675,000 quasars, allowing us to accurately quantify the pipeline's performance. This set of simulations reveals biases at the highest $k$ values, corresponding to a resolution error of a few percent. We base the resolution systematics error budget of DR1 $P_{\mathrm{1D}}$ on these values, but do not derive corrections from them since the simulation fidelity is insufficient for precise corrections.
title	DESI DR1 Ly$α$ 1D power spectrum: Validation of estimators
topic	Cosmology and Nongalactic Astrophysics
url	https://arxiv.org/abs/2509.13593