Using Machine Learning to Find Ghostly Damped Ly$\alpha$ Systems in SDSS DR14

Abstract

We report the discovery of 59 new ghostly absorbers from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). These absorbers, with $z_{\mathrm{abs}}$$\sim$$z_{\mathrm{QSO}}$, reveal no Ly$\alpha$ absorption, and they are mainly identified through the detection of strong metal absorption lines in the spectra. The number of previously known such systems is 30. The new systems are found with the aid of machine learning algorithms. The spectra of 41 (out of total of 89) absorbers also cover the Ly$\beta$ spectral region. By fitting the damping wings of the Ly$\beta$ absorption in the stacked spectrum of 21 (out of 41) absorbers with relatively stronger Ly$\beta$ absorption, we measured an HI column density of log$N$(HI)=21.50. This column density is 0.5dex higher than that of the previous work. We also found that the metal absorption lines in the stacked spectrum of the 21 ghostly absorbers with stronger Ly$\beta$ absorption have similar properties as those in the stacked spectrum of the remaining systems. These circumstantial evidence strongly suggest that the majority of our ghostly absorbers are indeed DLAs.

Accepted for publication in The Astrophysical Journal (ApJ)

References in corpus (32)

• Damped Lyman alpha Systems
• The Sloan Digital Sky Survey Quasar Catalog: Fourteenth Data Release
• The SDSS Damped Lya Survey: Data Release 3
• On the Kinematics of the Damped Lyman Alpha Protogalaxies
• Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9
• On the (Non)Evolution of HI Disks over Cosmic Time
• Damped Lyman alpha absorbers at high redshift -- large disks or galactic building blocks?
• Protogalactic Disk Models of Damped Lya Kinematics
• APM z>4 QSO Survey: Spectra and Intervening Absorption Systems
• Reproducing the Kinematics of Damped Lyman-alpha Systems
• Deep Learning of Quasar Spectra to Discover and Characterize Damped Lya Systems
• The UCSD Radio-Selected Quasar Survey for Damped Lyman alpha System
• The SDSS Damped Lya Survey: Data Release 1
• Damped Lyman alpha absorber and the faint end of the galaxy luminosity function at high redshift
• The nature of proximate damped Lyman alpha systems
• The CORALS Survey II: Clues to Galaxy Clustering Around QSOs from z_abs ~ z_em Damped Lyman Alpha Systems
• A z = 3 Lyman Alpha Blob Associated with a Damped Lyman Alpha System Proximate to its Background Quasar
• [CII] 158 Micron Emission from z~4 HI Absorption-Selected Galaxies
• Molecular Emission from a Galaxy Associated with a z~2.2 Damped Lyman-alpha Absorber
• A glance at the host galaxy of high-redshift quasars using strong damped Lyman-alpha systems as coronagraphs
• ALMA + VLT observations of a Damped Lyman-α absorbing galaxy: Massive, wide CO emission, gas-rich but with very low SFR
• Massive, Absorption-selected Galaxies at Intermediate Redshifts
• ALMACAL V: Absorption-selected galaxies with evidence for excited ISMs
• A ghostly damped Ly$\alpha$ system revealed by metal absorption lines
• Detecting Multiple DLAs per Spectrum in SDSS DR12 with Gaussian Processes
• Metallicities and dust content of proximate damped Lyman alpha systems in the Sloan Digital Sky Survey
• Extended Ly$\alpha$ emission around quasars with eclipsing damped Ly$\alpha$ systems
• Strong Ly alpha Emission in the Proximate Damped Ly alpha Absorption Trough toward the Quasar SDSS J095253.83+011422.0
• Eclipsing damped Ly$\alpha$ systems in the Sloan Digital Sky Survey Data Release 12
• A coronagraphic absorbing cloud reveals the narrow-line region and extended Lyman-$\alpha$ emission of QSO J0823+0529
• Ghostly Damped Ly$\alpha$ Systems: Tracers of Gas Flows in the Close Vicinity of Quasars ?
• Identifying the Lens Galaxy B1152+199 as a Ghostly Damped Lyman Alpha System by the Cosmic Origins Spectrograph

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