Detecting Multiple DLAs per Spectrum in SDSS DR12 with Gaussian Processes

Abstract

We present a revised version of our automated technique using Gaussian processes (GPs) to detect Damped Lyman-$\alpha$ absorbers (DLAs) along quasar (QSO) sightlines. The main improvement is to allow our Gaussian process pipeline to detect multiple DLAs along a single sightline. Our DLA detections are regularised by an improved model for the absorption from the Lyman-$\alpha$ forest which improves performance at high redshift. We also introduce a model for unresolved sub-DLAs which reduces mis-classifications of absorbers without detectable damping wings. We compare our results to those of two different large-scale DLA catalogues and provide a catalogue of the processed results of our Gaussian process pipeline using 158 825 Lyman-$\alpha$ spectra from SDSS data release 12. We present updated estimates for the statistical properties of DLAs, including the column density distribution function (CDDF), line density ($dN/dX$), and neutral hydrogen density (${\Omega }_{\text{DLA}}$).

arXiv comment24 pages, 20 figures, plus 3 tables of figure values. Minor changes to match version published in MNRAS. Code available in https://github.com/rmgarnett/gp_dla_detection/tree/master/multi_dlas

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• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• Neutral CGM as damped Lyα absorbers at high redshift
• The MUSE eXtremely Deep Field: Individual detections of Lyα haloes around rest-frame UV-selected galaxies at z~2.9-4.4
• Damped Lyman-alpha Absorbers from Sloan Digital Sky Survey DR16Q with Gaussian processes
• Cosmological Constraints from the eBOSS Lyman-$\alpha$ Forest using the PRIYA Simulations
• Connecting cosmological accretion to strong Lyman-alpha absorbers
• Quasar Factor Analysis -- An Unsupervised and Probabilistic Quasar Continuum Prediction Algorithm with Latent Factor Analysis
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• Synthetic spectra for Lyman-$\alpha$ forest analysis in the Dark Energy Spectroscopic Instrument
• Constraining the Halo Mass of Damped Ly$\alpha$ Absorption Systems (DLAs) at $z=2-3.5$ using the Quasar-CMB Lensing Cross-correlation
• Detecting neutral hydrogen at z > 3 in large spectroscopic surveys of quasars
• Using Machine Learning to Find Ghostly Damped Ly$\alpha$ Systems in SDSS DR14
• The Qz5 Survey (I): How the HI Mass Density of the Universe Evolves With Cosmic Time
• Automated Measurement of Quasar Redshift with a Gaussian Process
• Star-Formation in Neutral Hydrogen Gas Reservoirs at Cosmic Noon
• The Lyman-$\alpha$ Forest from LBGs: First 3D Correlation Measurement with DESI and Prospects for Cosmology