The eROSITA Final Equatorial Depth Survey (eFEDS): SDSS spectroscopic observations of X-ray sources

Abstract

We present one of the largest uniform optical spectroscopic surveys of X-ray selected sources to date that were observed as a pilot study for the Black Hole Mapper (BHM) survey. The BHM program of the Sloan Digital Sky Survey (SDSS)-V is designed to provide optical spectra for hundreds of thousands of X-ray selected sources from the SRG/eROSITA all-sky survey. This significantly improves our ability to classify and characterise the physical properties of large statistical populations of X-ray emitting objects. Our sample consists of 13079 sources in the eROSITA eFEDS performance verification field, 12011 of which provide reliable redshifts from 0<z<5.8. The vast majority of these objects were detected as point-like sources (X-ray flux limit F(0.5-2 keV)>6.5x10^-15 erg/s/cm^2) and were observed for about 20 years with fibre-fed SDSS spectrographs. After including all available redshift information for the eFEDS sources from the dedicated SDSS-V plate programme and archival data, we visually inspected the SDSS optical spectra to verify the reliability of these redshift measurements and the performance of the SDSS pipeline. The visual inspection allowed us to recover reliable redshifts (for 99% of the spectra with a signal-to-noise ratio of >2) and to assign classes to the sources, and we confirm that the vast majority of our sample consists of active galactic nuclei (AGNs). Only ~3% of the eFEDS/SDSS sources are Galactic objects. We also show the diversity of the optical spectra of the X-ray selected AGNs and provide spectral stacks with a high signal-to-noise ratio in various sub-samples with different redshift and optical broad-band colours. Our AGN sample contains optical spectra of (broad-line) quasars, narrow-line galaxies, and optically passive galaxies. It is considerably diverse in its colours and in its levels of nuclear obscuration.

References in corpus (79)

• The Sloan Digital Sky Survey: Technical Summary
• The Seventh Data Release of the Sloan Digital Sky Survey
• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The SIMBAD astronomical database
• SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems
• The Host Galaxies and Classification of Active Galactic Nuclei
• The Baryon Oscillation Spectroscopic Survey of SDSS-III
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Main Galaxy Sample
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Overview of the DESI Legacy Imaging Surveys
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• Using Strong Lines to Estimate Abundances in Extragalactic HII Regions and Starburst Galaxies
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
• The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures
• Spectroscopic Target Selection for the Sloan Digital Sky Survey: The Luminous Red Galaxy Sample
• The eROSITA X-ray telescope on SRG
• Revisiting the Unified Model of Active Galactic Nuclei
• An Overview of the Performance and Scientific Results from the Chandra X-Ray Observatory (CXO)
• The 2MASS Redshift Survey - Description and Data Release
• Spectral Classification and Redshift Measurement for the SDSS-III Baryon Oscillation Spectroscopic Survey
• Active Galactic Nuclei: what's in a name?
• A comprehensive classification of galaxies in the SDSS: How to tell true from fake AGN?
• Galaxy And Mass Assembly (GAMA): end of survey report and data release 2
• What Drives the Growth of Black Holes?
• Understanding Galaxy Evolution through Emission Lines
• The WiggleZ Dark Energy Survey: Survey Design and First Data Release
• Second Data Release of the Hyper Suprime-Cam Subaru Strategic Program
• Host galaxies, clustering, Eddington ratios, and evolution of radio, X-ray, and infrared-selected AGNs
• The Chandra COSMOS Legacy survey: overview and point source catalog
• The Thirteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey MApping Nearby Galaxies at Apache Point Observatory
• Second ROSAT all-sky survey (2RXS) source catalogue
• Obscured Active Galactic Nuclei
• Deep Extragalactic X-ray Surveys
• Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: II. Formation of Red Ellipticals
• GAMA: towards a physical understanding of galaxy formation
• The SRG X-ray orbital observatory, its telescopes and first scientific results
• Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The eROSITA Final Equatorial Depth Survey (eFEDS): The X-ray catalog
• The Anglo-Australian Observatory's 2dF Facility
• Cosmic X-ray Surveys of Distant Active Galaxies: The Demographics, Physics, and Ecology of Growing Supermassive Black Holes
• The XMM-Newton Wide-Field Survey in the COSMOS field (XMM-COSMOS): demography and multiwavelength properties of obscured and unobscured luminous AGN
• The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V
• Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions
• The HELLAS2XMM survey: IV. Optical identifications and the evolution of the accretion luminosity in the Universe
• The Evolution of Normal Galaxy X-ray Emission Through Cosmic History: Constraints from the 6 Ms Chandra Deep Field-South
• High-Redshift SDSS Quasars with Weak Emission Lines
• Gaia Data Release 2: Processing the spectroscopic data
• The eROSITA Final Equatorial-Depth Survey (eFEDS): Catalog of galaxy clusters and groups
• The 2dF-SDSS LRG and QSO Survey: The spectroscopic QSO catalogue
• The eROSITA Final Equatorial-Depth Survey (eFEDS): Identification and characterization of the counterparts to the point-like sources
• A Spectroscopic Survey of X-ray Selected AGN in the Northern XMM-XXL Field
• Supermassive Black Holes at High Redshift are Expected to be Obscured by their Massive Host Galaxies' Inter Stellar Medium
• BAL and non-BAL quasars: continuum, emission and absorption properties establish a common parent sample
• The eROSITA Final Equatorial-Depth Survey (eFEDS): The AGN Catalogue and its X-ray Spectral Properties
• New AGN diagnostic diagrams based on the [OIII]$\lambda 4363$ auroral line
• RCSED - A Value-Added Reference Catalog of Spectral Energy Distributions of 800,299 Galaxies in 11 Ultraviolet, Optical, and Near-Infrared Bands: Morphologies, Colors, Ionized Gas and Stellar Populations Properties
• The Hellas2XMM survey: III. Multiwavelength observations of hard X-ray selected sources in the PKS 0312-77 field
• SPIDERS: Selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys
• The eROSITA Final Equatorial-Depth Survey (eFEDS): Galaxy Clusters and Groups in Disguise
• BASS XXXVII: The role of radiative feedback in the growth and obscuration properties of nearby supermassive black holes
• Highly accreting quasars: The SDSS low-redshift catalog
• Full-sky photon simulation of clusters and active galactic nuclei in the soft X-rays for eROSITA
• The eROSITA Final Equatorial-Depth Survey (eFEDS): Optical confirmation, redshifts, and properties of the cluster and group catalog
• Sensitive Chandra coverage of a representative sample of weak-line quasars: revealing the full range of X-ray properties
• The eROSITA Final Equatorial-Depth Survey (eFEDS): A multiwavelength view of WISE mid-infrared galaxies/active galactic nuclei
• Observing Supermassive Black Holes across cosmic time: from phenomenology to physics
• The cosmic web of X-ray active galactic nuclei seen through the eROSITA Final Equatorial Depth Survey (eFEDS)
• The eROSITA Final Equatorial Depth Survey (eFEDS): Complex absorption and soft excesses in hard X-ray--selected active galactic nuclei
• The eROSITA Final Equatorial-Depth Survey (eFEDS). The stellar counterparts of eROSITA sources identified by machine learning and Bayesian algorithms
• The eROSITA Final Equatorial-Depth Survey (eFEDS): Presenting The Demographics of X-ray Emission From Normal Galaxies
• Compact white-dwarf binaries in the combined SRG/eROSITA/SDSS eFEDS survey
• The LOFAR-eFEDS survey: The incidence of radio and X-ray AGN and the disk-jet connection
• The eROSITA Final Equatorial Depth Survey (eFEDS): the hard X-ray selected sample
• Center for Astrophysics Optical Infrared Science Archive. I. FAST Spectrograph

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