eROSITA Final Equatorial-Depth Survey (eFEDS)

Ichikawa, Kohei; Yamashita, Takuji; Merloni, A.; Li, J.; Liu, T.; Salvato, M.; Akiyama, Masayuki; Arcodia, R.; Dwelly, T.; Chen, X.; Imanishi, Masatoshi; Inayoshi, Kohei; Kawaguchi, Toshihiro; Kawamuro, T.; Kokubo, Mitsuru; Matsuoka, Yoshiki; Nagao, Tohru; Schramm, Malte; Suh, Hyewon; Tanaka, Masayuki; Toba, Yoshiki; Ueda, Yoshihiro

doi:10.1051/0004-6361/202244271

A&A

2023

DOI: 10.1051/0004-6361/202244271

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eROSITA Final Equatorial-Depth Survey (eFEDS)

Kohei Ichikawa

Takuji Yamashita

A. Merloni

et al.

Abstract: We constructed the eROSITA X-ray catalog of radio galaxies discovered by the WERGS survey, made by cross-matching the wide area Subaru/Hyper Suprime-Cam (HSC) optical survey and VLA/FIRST 1.4 GHz radio survey. We report finding 393 eROSITA detected radio galaxies in the 0.5−2 keV band in the eFEDS field covering 140 deg2. Thanks to the wide and medium depth eFEDS X-ray survey down to f0.5 − 2 keV = 6.5 × 10−15 erg s−1 cm−2, the sample contains the rare and most X-ray luminous radio galaxies above the knee of t… Show more

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2024

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Cited by 3 publications

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The LOFAR – eFEDS survey: The incidence of radio and X-ray AGN and the disk–jet connection

Igo,

Merloni,

Hoang

et al. 2024

A&A

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Radio jets are present in a diverse sample of AGN. However, the mechanisms of jet powering are not fully understood, and it remains unclear to what extent they obey mass-invariant scaling relations similar to those found for the triggering and fuelling of X-ray-selected AGN. We use the multi-wavelength data in the eFEDS field observed by eROSITA/ Spectrum-Roentgen-Gamma (SRG) and LOFAR to study the incidence of X-ray and radio AGN as a function of several stellar mass ($M_*$)-normalised AGN power indicators. From the LOFAR - eFEDS survey, we defined a new sample of radio AGN, with optical counterparts from Legacy Survey DR9, according to a radio-excess relative to their host star formation rate. We further divided the sample into compact and complex radio morphologies. In this work, we used the subset matching to the well-characterised, highly complete spectroscopic GAMA09 galaxies ($0<z<0.4$). We release this value-added LOFAR - eFEDS catalogue$^*$. We calculated the fraction of GAMA09 galaxies hosting radio, X-ray, and both radio and X-ray AGN as functions of the specific black hole kinetic ($ Jet $) and radiative ($ Edd $) power. Despite the soft-X-ray eROSITA-selected sample, the incidence of X-ray AGN as a function of $ Edd $ shows the same mass-invariance and power law slope ($-0.65$) as that found in previous studies once corrected for completeness. Across the $M_*$ range probed, the incidence of compact radio AGN as a function of $ Jet $ is described by a power law with constant slope, showing that it is not only high mass galaxies hosting high power jets and vice versa. This slope is steeper than that of the X-ray incidence, which has a value of around $-1.5$. Furthermore, higher-mass galaxies are more likely to host radio AGN across the $ Jet $ range, indicating some residual mass dependence of jet powering. Upon adding complex radio morphologies, including 34 FRIIs, three of which are giant radio galaxies, the incidence not only shows a larger mass dependence but also a jet power dependence, being clearly boosted at high $ Jet $ values. Importantly, the latter effect cannot be explained by such radio AGN residing in more dense environments (or more massive dark matter haloes). The similarity in the incidence of quiescent and star-forming radio AGN reveals that radio AGN are not only found in `red and dead' galaxies. Overall, our incidence analysis reveals some fundamental statistical properties of radio AGN samples, but highlights open questions regarding the use of a single radio luminosity--jet power conversion. We explore how different mass and accretion rate dependencies of the incidence can explain the observed results for varying disk--jet coupling models.

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The LOFAR – eFEDS survey: The incidence of radio and X-ray AGN and the disk–jet connection

Igo,

Merloni,

Hoang

et al. 2024

A&A

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A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). X. The Massive and Passive Nature of Radio Galaxies at z ∼ 4

Yamamoto,

Nagao,

Yamashita

et al. 2024

ApJ

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High-z radio galaxies (HzRGs) are considered important objects for understanding the formation and evolution of massive galaxies in the early Universe. However, until to date, detailed studies of the stellar population of HzRGs, such as the star formation history, have been scarce. Therefore, this study conducted a new survey to establish a less-biased sample of HzRGs and consequently investigate their properties. We utilized a sample of g-dropout Lyman break galaxies (LBGs) obtained from an optical wide and deep imaging survey made by Subaru Hyper Suprime-Cam. Based on the cross matching of this LBG sample with the Very Large Array Faint Images of the Radio Sky at Twenty cm radio survey data, we constructed a photometric sample of HzRGs at z ∼ 4 for a ∼560 deg2 survey field. Consequently, we identified 146 HzRG candidates. To analyze the characteristics of these candidates, we focus on objects exhibiting the near-infrared photometry of VIKING or UKIRT Infrared Deep Sky Survey and the mid-infrared photometry of unWISE (28 objects). The results indicate that seven objects exhibit spectral energy distributions (SEDs) consistent with galaxies at z ∼ 4. The HzRG candidates have very large stellar masses with ∼4.2 × 1011 M ⊙ on average. This stellar mass is similar to that of previously discovered ultra-steep-spectrum HzRGs at z ∼ 4, though our sample is affected by a sample selection bias that selects only HzRGs with M ⋆ > 1011 M ⊙. Further, the SEDs of those HzRG candidates suggest a past fast quenching with a rough timescale of ∼0.1 Gyr, as evidenced from the rest-frame UVJ diagram.

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Birth of Rapidly Spinning, Overmassive Black Holes in the Early Universe

Inayoshi,

Ichikawa

2024

ApJL

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The James Webb Space Telescope (JWST) has unveiled numerous massive black holes (BHs) in faint, broad-line active galactic nuclei (AGNs). The discovery highlights the presence of dust-reddened AGN populations, referred to as “little red dots (LRDs),” more abundant than X-ray-selected AGNs, which are less influenced by obscuration. This finding indicates that the cosmic growth rate of BHs within this population does not decrease but rather increases at higher redshifts beyond z ∼ 6. The BH accretion rate density deduced from their luminosity function is remarkably higher than that from other AGN surveys in X-ray and infrared bands. To align the cumulative mass density accreted to BHs with the observed BH mass density at z ≃ 4–5, as derived from the integration of the BH mass function, the radiative efficiency must be doubled from the canonical 10% value, achieving significance beyond the >3σ confidence level. This suggests the presence of rapid spins with 96% of the maximum limit among these BHs under the thin-disk approximation, maintained by prolonged mass accretion instead of chaotic accretion with randomly oriented inflows. Moreover, we derive an upper bound for the stellar mass of galaxies hosting these LRDs, ensuring consistency with galaxy formation in the standard cosmological model, where the host stellar mass is limited by the available baryonic reservoir. Our analysis gives a lower bound for the BH-to-galaxy mass ratio that exceeds the typical value known in the nearby universe and aligns with that for JWST-detected unobscured AGNs. Accordingly, we propose a hypothesis that the dense, dust-rich environments within LRDs facilitate the emergence of rapidly spinning and overmassive BH populations during the epoch of reionization. This scenario predicts a potential association between relativistic jets and other high-energy phenomena with overmassive BHs in the early universe.

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eROSITA Final Equatorial-Depth Survey (eFEDS)

Cited by 3 publications

References 221 publications

The LOFAR – eFEDS survey: The incidence of radio and X-ray AGN and the disk–jet connection

The LOFAR – eFEDS survey: The incidence of radio and X-ray AGN and the disk–jet connection

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). X. The Massive and Passive Nature of Radio Galaxies at z ∼ 4

Birth of Rapidly Spinning, Overmassive Black Holes in the Early Universe

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