arXiv · 2503.14740
Construction of the Damped Ly$\alpha$ Absorber Catalog for DESI DR2 Ly$\alpha$ BAO
Abstract
We present the Damped Ly$\alpha$ Toolkit for automated detection and characterization of Damped Ly$\alpha$ absorbers (DLA) in quasar spectra. Our method uses quasar spectral templates with and without absorption from intervening DLAs to reconstruct observed quasar forest regions. The best-fitting model determines whether a DLA is present while estimating the redshift and \texttt{HI} column density. With an optimized quality cut on detection significance ($\Delta \chi_{r}^2>0.03$), the technique achieves an estimated 80\% purity and 79\% completeness when evaluated on simulated spectra with S/N~$>2$ that are free of broad absorption lines (BAL). We provide a catalog containing candidate DLAs from the DLA Toolkit detected in DESI DR1 quasar spectra, of which 21,719 were found in S/N~$>2$ spectra with predicted $\log_{10} (N_\texttt{HI}) > 20.3$ and detection significance $\Delta \chi_{r}^2 >0.03$. We compare the Damped Ly$\alpha$ Toolkit to two alternative DLA finders based on a convolutional neural network (CNN) and Gaussian process (GP) models. We present a strategy for combining these three techniques to produce a high-fidelity DLA catalog from DESI DR2 for the Ly$\alpha$ forest baryon acoustic oscillation measurement. The combined catalog contains 41,152 candidate DLAs with $\log_{10} (N_\texttt{HI}) > 20.3$ from quasar spectra with S/N~$>2$. We estimate this sample to be approximately 85\% pure and 79\% complete when BAL quasars are excluded.
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A. Brodzeller, M. Wolfson, D. M. Santos, M. Ho, T. Tan, M. M. Pieri, A. Cuceu, M. Abdul-Karim, J. Aguilar, S. Ahlen, A. Anand, U. Andrade, E. Armengaud, A. Aviles, S. Bailey, A. Bault, D. Bianchi, D. Brooks, R. Canning, L. Casas, M. Charles, E. Chaussidon, J. Chaves-Montero, D. Chebat, T. Claybaugh, K. S. Dawson, R. de Belsunce, A. de la Macorra, A. de Mattia, Arjun Dey, Biprateep Dey, M. Doshi, P. Doel, W. Elbers, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, C. Garcia-Quintero, L. H. Garrison, E. Gaztañaga, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, D. Green, G. Gutierrez, J. Guy, C. Hahn, M. Herbold, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett, D. Huterer, M. Ishak, S. Juneau, R. Kehoe, T. Kisner, A. Kremin, O. Lahav, C. Lamman, M. Landriau, J. M. Le Goff, L. Le Guillou, A. Leauthaud, M. E. Levi, Q. Li, M. Manera, P. Martini, A. Meisner, J. Mena-Fernandez, R. Miquel, J. Moustakas, A. Muñoz-Gutiérrez, A. D. Myers, S. Nadathur, L. Napolitano, H. E. Noriega, E. Paillas, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, I. Pérez-Ràfols, C. Ramírez-Pérez, C. Ravoux, J. Rohlf, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, F. Sinigaglia, D. Sprayberry, G. Tarlé, P. Taylor, W. Turner, M. Walther, B. A. Weaver, C. Yèche, R. Zhou, H. Zou, S. Zou. 2025-03-18. Construction of the Damped Ly$\alpha$ Absorber Catalog for DESI DR2 Ly$\alpha$ BAO. https://arxiv.org/abs/2503.14740
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