The eROSITA Final Equatorial-Depth Survey (eFEDS)

Toba, Yoshiki; Liu, T.; Urrutia, T.; Salvato, M.; Li, J.; Ueda, Yoshihiro; Brusa, M.; Yutani, Naomichi; Wada, Keiichi; Nishizawa, Atsushi J.; Buchner, Johannes; Nagao, Tohru; Merloni, A.; Akiyama, Masayuki; Arcodia, R.; Hsieh, Bau-Ching; Ichikawa, Kohei; Imanishi, Masatoshi; Inoue, Kaiki Taro; Kawaguchi, Toshihiro; Lamer, G.; Nandra, K.; Silverman, John D.; Terashima, Yuichi

doi:10.1051/0004-6361/202141547

Cited by 22 publications

(16 citation statements)

References 176 publications

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“…In addition to LS8, Gaia, and WISE, it is also partly covered by the Galex survey, the Kilo-degree Survey (KiDS), the Viking survey, the VISTA/VHS survey, and the UKIDSS survey (see Paper II). Particularly, highspatial-resolution photometry was also obtained with the Hyper Suprime-Cam (HSC; Miyazaki et al 2018) Program (HSC-SSP; Aihara et al 2018); its S19A photometry data (Aihara et al 2019;Toba et al 2022) was used in Paper II to construct the SED. According to optical spectra or SED, Paper II classified each counterpart as galactic or extragalactic sources.…”

Section: The Efeds Agn Catalogmentioning

confidence: 99%

The eROSITA Final Equatorial-Depth Survey (eFEDS)

Liu

Buchner

Nandra

et al. 2022

A&A

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Context. The eROSITA Final Equatorial Depth Survey (eFEDS), observed with eROSITA ahead of its planned 4-yr all-sky survey, is the largest contiguous-field X-ray survey at present. It yielded a large sample of X-ray sources with very rich multiband photometric and spectroscopic coverage. Aims. We present here the eFEDS active galactic nuclei (AGN) catalog and the eROSITA X-ray spectral properties of the eFEDS sources. Methods. Using a Bayesian method, we performed a systematic X-ray spectral analysis for all the eFEDS sources. We adopted multiple spectral models, including single-component power-law or hot-plasma models and double-component models of a power law plus soft excess. We investigated the capacity of eROSITA X-ray spectra for constraining AGN spectral shapes through a detailed analysis of the posterior parameter probability distribution functions. Hierarchical Bayesian modeling was used to recover the spectral parameter distribution of the sample. The source fluxes and luminosities were measured from the posterior of the spectral fitting. Results. The eFEDS AGN catalog (22 079 sources) comprises ~80% of the eFEDS point sources. Despite a large number of faint sources, our spectral fitting provides reasonable measurements of spectral shapes and intrinsic luminosities for a majority of the sources. Because of sample selection bias, this AGN catalog is dominated by X-ray unobscured sources, with an obscured (logNH > 21.5) fraction of 8%; the power-law emission of the hot corona is also relatively soft, with a typical slope of 2.0. For type-I AGN, the X-ray emission is well correlated with the UV emission with the usual anticorrelation between the X-ray to UV spectral slope αOX and the UV luminosity. The X-ray spectral properties measured with various models are presented for all the eFEDS sources.

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Section: The Efeds Agn Catalogmentioning

confidence: 99%

The eROSITA Final Equatorial-Depth Survey (eFEDS)

Liu

Buchner

Nandra

et al. 2022

A&A

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“…X-CIGALE generates the best-fit model, including the stellar, AGN, and SF components that fit the photometric data in the rest-frame UV to far-infrared (FIR) bands. We utilize the Herschel Space Observatory (Pilbratt et al 2010) Astrophysical Terahertz Large Area Survey (H- To search for the H-ATLAS counterpart of the four BluDOGs, we adopt a search radius of 10″ by following Toba et al (2019) (and Toba et al 2022). Accordingly, we found the counterparts of two BluDOGs (J1202 and J1207).…”

Section: Estimating the Dust Extinctionmentioning

confidence: 99%

Extreme Nature of Four Blue-excess Dust-obscured Galaxies Revealed by Optical Spectroscopy

Noboriguchi

Nagao

Toba

et al. 2022

ApJ

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We report optical spectroscopic observations of four blue-excess dust-obscured galaxies (BluDOGs) identified by the Subaru Hyper Suprime-Cam. BluDOGs are a subclass of dust-obscured galaxies (DOGs; defined with the extremely red color (i − [22])AB ≥ 7.0; Toba et al., showing a significant flux excess in the optical g and r bands over the power-law fits to the fluxes at the longer wavelengths. Noboriguchi et al. have suggested that BluDOGs may correspond to the blowing-out phase involved in a gas-rich major-merger scenario. However, the detailed properties of BluDOGs are not understood because of the lack of spectroscopic information. In this work, we carry out deep optical spectroscopic observations of four BluDOGs using Subaru/FOCAS and VLT/FORS2. The obtained spectra show broad emission lines with extremely large equivalent widths, and a blue wing in the C iv line profile. The redshifts are between 2.2 and 3.3. The averaged rest-frame equivalent widths of the C iv lines are 160 ± 33 Å, ∼7 times higher than the average of a typical type 1 quasar. The FWHMs of their velocity profiles are between 1990 and 4470 km s−1, and their asymmetric parameters are 0.05 and 0.25. Such strong C iv lines significantly affect the broadband magnitudes, which are partly the origin of the blue excess seen in the spectral energy distribution of BluDOGs. Their estimated supermassive black hole masses are 1.1 × 108 < M BH/M ⊙ <5.5 × 108. The inferred Eddington ratios of the BluDOGs are higher than 1 (1.1 < λ Edd < 3.8), suggesting that the BluDOGs are in a rapidly evolving phase of supermassive black holes.

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“…We used the X-CIGALE code (Yang et al 2020(Yang et al , 2022 to derive the physical properties of the high-z sources and, specifically, the M * and the SFR. X-CIGALE, is a new branch of the Code Investigating GALaxy Emission (CIGALE, Boquien et al 2019), a multi-component SED fitting algorithm that fits the observational data of the sources to the theoretical models, and has been widely used in the literature (e.g Pouliasis et al 2020;Padilla et al 2021;Toba et al 2021bToba et al ,a, 2022Yang et al 2021). X-CIGALE offers new capabilities, such as the inclusion of the X-ray absorption-corrected flux, f X , in the fitting process and accounts for extinction of the UV and optical emission in the poles of AGNs (Yang et al 2018;Mountrichas et al 2021a;Buat et al 2021;Toba et al 2021b).…”

Section: Sed Fitting and Parameter Estimationmentioning

confidence: 99%

XXL-HSC: Link between AGN activity and star formation in the early Universe (z⩾ 3.5)

Pouliasis

Mountrichas

Georgantopoulos

et al. 2022

A&A

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In this work, our aim is to investigate the star formation rate (SFR) of the host galaxies of active galactic nuclei (AGNs) in the early Universe. To this end, we constructed a sample of 149 luminous (L 2−10keV > 10 44 erg s −1 ) X-ray AGNs at z ≥ 3.5 selected in three fields with different depths and observed areas from the Chandra COSMOS Legacy survey, XMM-XXL North, and eROSITA Final Equatorial-Depth Survey. We built their spectral energy distributions (SED) using the available multi-wavelength photometry from X-rays up to the far-IR. Then, we estimated the stellar mass, M * , and the SFR of the AGNs using the X-CIGALE SED fitting algorithm. After applying several quality criteria, we ended up with 89 high-z sources. More than half (55%) of the X-ray sample have spectroscopic redshifts. Based on our analysis, our high-z X-ray AGNs live in galaxies with a median M * = 5.6 × 10 10 M ⊙ and SFR * ≈ 240 M ⊙ yr −1 . The majority of the high-z sources (∼ 89%) were found inside or above the main sequence (MS) of star-forming galaxies. Estimations of the normalised SFR, SFR NORM , defined as the ratio of the SFR of AGNs, to the SFR of MS galaxies, show that the SFR of AGNs is enhanced by a factor of ∼ 1.8 compared to non-AGN star-forming systems. Combining our results with previous studies at lower redshifts, we confirmed that SFR NORM does not evolve with redshift. Using the specific black hole accretion rate (i.e. L X divided by M * ), λ BHAR , which can be used as a tracer of the Eddington ratio, we found that the majority of AGNs that lie inside or above the MS have higher specific accretion rates compared to sources below the MS. Finally, we found indications that the SFR of the most massive AGN host galaxies (log (M * /M ⊙ ) > 10 11.5−12 ) remains roughly constant as a function of M * , in agreement with the SFR of MS star-forming galaxies.

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The eROSITA Final Equatorial-Depth Survey (eFEDS)

Cited by 22 publications

References 176 publications

The eROSITA Final Equatorial-Depth Survey (eFEDS)

The eROSITA Final Equatorial-Depth Survey (eFEDS)

Extreme Nature of Four Blue-excess Dust-obscured Galaxies Revealed by Optical Spectroscopy

XXL-HSC: Link between AGN activity and star formation in the early Universe (z⩾ 3.5)

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