The eROSITA Final Equatorial Depth Survey (eFEDS)

Context. During its calibration and performance verification phase, the eROSITA instrument aboard the Spectrum-RG satellite performed a uniform wide-area X-ray survey of approximately 140 deg 2 , known as the eROSITA Final Equatorial Depth Survey (eFEDS). Aims. The primary aim of eFEDS is to demonstrate the scientific performance to be expected at the end of the eight–pass eROSITA all-sky survey. This survey will provide the first focussed image of the whole sky in the hard X-ray (>2 keV) bandpass. The expected source population in this energy range is thus of great interest, particularly for AGN studies. Methods. We used a 2.3–5 keV selection to construct a sample of 246 point-like hard X-ray sources for further study and characterisation. These sources are classified as either extragalactic (∼90%) or Galactic (∼10%), with the former consisting overwhelmingly of AGN and the latter active stars. We concentrated our further analysis on the extragalactic AGN sample, describing their X-ray and multi-wavelength properties and comparing them to the eFEDS main AGN sample selected in the softer 0.2–2.3 keV band. Results. The eROSITA hard band selects a subsample of sources that is a factor of more than ten brighter than the eFEDS main sample. The AGN within the hard population reach up to z = 3.2 but on the whole, they are relatively nearby, with median z = 0.34 compared to z = 0.94 for the main sample. The hard survey probes typical luminosities in the range log L X = 43–46. The X-ray spectral analysis shows significant intrinsic absorption (with log N H > 21) in ~20% of the sources, with a hard X-ray power law continuum with mean < Γ >= 1.83 ± 0.04, which is typical of AGN, but slightly harder than the soft-selected eROSITA sample. Around 10% of the hard sample show a significant ‘soft excess’ component. The sampled black hole mass distribution in the eFEDS broad-line AGN population is consistent with that of the deeper COSMOS survey that probes a higher redshift population. On the other hand, the Eddington ratios appear systematically lower, which is consistent with the idea that the decline in SMBH activity since z ∼ 1 is due to a reduction in the typical accretion rate, rather than a shift towards activity in lower-mass black holes. Conclusions. The eFEDS hard sample provides a preview of what can be expected from the eRASS final survey in terms of data quality. This pilot survey indicates the power of eROSITA to shed new light on the demographics and evolution of AGN, and the potential for discovery of new and rare populations.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-10-14
DOI
https://doi.org/10.1051/0004-6361/202449416
Citations
8
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
2.65

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article

The eROSITA Final Equatorial Depth Survey (eFEDS)

Z. Igo, W. N. Brandt, M. Krumpe, Héctor J. Ibarra-Medel et al.
8 citations
Astronomy and Astrophysics
Astro and Planetary Science
2.65
article

The eROSITA Final Equatorial Depth Survey (eFEDS)

Z. Igo, W. N. Brandt, M. Krumpe, Héctor J. Ibarra-Medel, B. Musiimenta, Sophia G. H. Waddell, F. E. Bauer, Hans‐Walter Rix, Roberto J. Assef, A. Merloni, J. Wolf, M. Salvato, H. Brunner, J. Comparat, R. Arcodia, T. Dwelly, Yue Shen, K. Nandra, A. Georgakakis, Johannes Büchner, W. Collmar, G. Lamer, M. Brusa, Tingting Liu, Thomas Böller, Qingwen Wu, M. Grau, S. Hämmerich
article en
8 citations

Abstract

Context. During its calibration and performance verification phase, the eROSITA instrument aboard the Spectrum-RG satellite performed a uniform wide-area X-ray survey of approximately 140 deg 2 , known as the eROSITA Final Equatorial Depth Survey (eFEDS). Aims. The primary aim of eFEDS is to demonstrate the scientific performance to be expected at the end of the eight–pass eROSITA all-sky survey. This survey will provide the first focussed image of the whole sky in the hard X-ray (>2 keV) bandpass. The expected source population in this energy range is thus of great interest, particularly for AGN studies. Methods. We used a 2.3–5 keV selection to construct a sample of 246 point-like hard X-ray sources for further study and characterisation. These sources are classified as either extragalactic (∼90%) or Galactic (∼10%), with the former consisting overwhelmingly of AGN and the latter active stars. We concentrated our further analysis on the extragalactic AGN sample, describing their X-ray and multi-wavelength properties and comparing them to the eFEDS main AGN sample selected in the softer 0.2–2.3 keV band. Results. The eROSITA hard band selects a subsample of sources that is a factor of more than ten brighter than the eFEDS main sample. The AGN within the hard population reach up to z = 3.2 but on the whole, they are relatively nearby, with median z = 0.34 compared to z = 0.94 for the main sample. The hard survey probes typical luminosities in the range log L X = 43–46. The X-ray spectral analysis shows significant intrinsic absorption (with log N H > 21) in ~20% of the sources, with a hard X-ray power law continuum with mean < Γ >= 1.83 ± 0.04, which is typical of AGN, but slightly harder than the soft-selected eROSITA sample. Around 10% of the hard sample show a significant ‘soft excess’ component. The sampled black hole mass distribution in the eFEDS broad-line AGN population is consistent with that of the deeper COSMOS survey that probes a higher redshift population. On the other hand, the Eddington ratios appear systematically lower, which is consistent with the idea that the decline in SMBH activity since z ∼ 1 is due to a reduction in the typical accretion rate, rather than a shift towards activity in lower-mass black holes. Conclusions. The eFEDS hard sample provides a preview of what can be expected from the eRASS final survey in terms of data quality. This pilot survey indicates the power of eROSITA to shed new light on the demographics and evolution of AGN, and the potential for discovery of new and rare populations.

Astronomy and AstrophysicsVol. 693
Space Science Institute (US), Pennsylvania State University (US), University of Illinois Urbana-Champaign (US), Pontificia Universidad Católica de Chile (CL), Friedrich-Alexander-Universität Erlangen-Nürnberg (DE), University of Atacama (CL), Leibniz Institute for Astrophysics Potsdam (DE), Max Planck Institute for Extraterrestrial Physics (DE), Millennium Institute of Astrophysics (CL), Max Planck Institute for Astronomy (DE), National Observatory of Athens (GR), Osservatorio di Astrofisica e Scienza dello Spazio, Universidad Diego Portales (CL), University of Bologna (IT)
National Science Foundation, Smithsonian Institution, U.S. Department of Energy, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Princeton University, Ohio State University, Harvard University, University of Utah, Johns Hopkins University, New Mexico State University, Space Telescope Science Institute, European Commission, Ministry of Education, Culture, Sports, Science and Technology, École Polytechnique Fédérale de Lausanne, Academia Sinica, Eberhard Karls Universität Tübingen, Cabinet Office, Government of Japan, University of Toronto, Max-Planck-Gesellschaft, Universität Hamburg, Universidad Nacional Autónoma de México, National Astronomical Observatory of Japan, High Energy Accelerator Research Organization, Yunnan University, Nanjing University, Rheinische Friedrich-Wilhelms-Universität Bonn, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Agencia Nacional de Investigación y Desarrollo, Max-Planck-Institut für Astronomie, Toray Science Foundation, University of Illinois at Urbana-Champaign, Office of Science, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Leibniz-Gemeinschaft, Japan Society for the Promotion of Science, Japan Science and Technology Agency, Russian Academy of Sciences, National Astronomical Observatories, Chinese Academy of Sciences, HORIZON EUROPE Marie Sklodowska-Curie Actions
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Openalex Percentile: Top 10%
Astro and Planetary Science
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