[논문 리뷰] Investigating the origin of radio emission in candidate super-Eddington accreting black holes

Marie-Lou Gendron-Marsolais, Paola Marziani외 9명|arXiv (Cornell University)|2026. 01. 30.

Astrophysical Phenomena and Observations인용 수 0

한 줄 요약

본 연구는 18 xA quasars에 대해 다중 대역 라디오(VLA, LOFAR, VLASS)와 IR 데이터를 활용하여 그들의 라디오 방출이 star formation에 의해 지배되는지 아니면 AGN 관련 과정에 의해 지배되는지 여부를 결정하고, SF가 지배적인 경우가 다수이며 몇몇은 concurrent super-Eddington accretion과 relativistic ejections가 동시에 나타나는 혼합 사례를 발견했다.

ABSTRACT

Recent works show that the radio power of quasars accreting at very high rates can reach surprisingly high values. These studies suggest that this radio emission might originate from star formation, but lack of data leaves open the possibility that they could also contain a jetted active galactic nucleus (AGN). We investigate the origin of the radio emission of a sample of 18 super-Eddington candidates, over a wide range of redshifts. These sources are expected to have extreme radiative output per unit black hole mass, show high-velocity outflows and are therefore thought to be a prime mover of galactic evolution via radiative and mechanical feedback. We present new Karl G. Jansky Very Large Array (VLA) observations at L, C and X-band of these sources, which we combine with observations from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) and the Very Large Array Sky Survey (VLASS). We also use optical and IR data to derive estimates of accretion and wind parameters, as well as star formation rates to compare with the ones derived from the radio emission. Based on the radio variability, luminosity, morphology, radio spectral properties, radio vs IR estimates of star formation rate and radio-to-mid IR flux ratio, we find that 7 of our 18 targets are likely to have their radio emission predominantly coming from SF, and 6 from a combination of SF and AGN-related mechanisms, while only three sources indicate a core or jetted AGN only origin for the detected radio emission. This is consistent with previous studies, and supports the prevalence of lower power radio structures associated with star-forming activity rather than relativistic jets in the high Eddington ratio regime. In the same sample, however, we find three sources for which the data suggest a concomitant presence of super-Eddington accretion and relativistic ejections.

연구 동기 및 목표

• Assess whether radio emission in a sample of 18 xA (high Fe II) quasars is primarily from star formation or AGN-related outflows/jets.
• Combine VLA, LOFAR, and VLASS radio data with optical/IR measurements to estimate accretion, wind, and star formation parameters.
• Classify radio morphology and spectral properties to infer the dominant emission mechanism for each source.

제안 방법

• Observe 18 xA quasars with VLA in L, C, and X bands (1.5, 5, 10 GHz) and supplement with LOFAR LoTSS (144 MHz) and VLASS (3 GHz).
• Reduce data with CASA, perform wideband imaging, and apply self-calibration and wideband primary beam corrections.
• Compute spectral indices from multi-band fluxes, derive radio luminosities and Kellermann R_K values, and compare radio to mid-IR flux ratios (Q22) and SFR indicators.
• Define radio morphologies using peak/total flux ratios to classify as Compact, Intermediate, or Extended.
• Estimate SFR from IR luminosity and compare to radio-derived SFR using established calibrations (e.g., Kennicutt).

Figure 1: Prevalence of FIRST-detected type-1 AGN (Marziani et al. , 2013 ) (blue circles and cyan shading) and median radio power (red circles and rose shading) as a function of spectral type along the quasar main sequence.

실험 결과

연구 질문

• RQ1 What fraction of the radio emission in xA quasars is due to star formation versus AGN-related processes?
• RQ2 Can radio morphologies, spectral indices, and radio-to-IR diagnostics discriminate between SF-dominated and jet-dominated emission in super-Eddington candidates?
• RQ3 Are there sources showing concurrent super-Eddington accretion and relativistic ejections?
• RQ4 How does radio activity in xA objects relate to their place on the quasar main sequence and Eddington ratios?

주요 결과

• 7 of the 18 targets have radio emission predominantly from star formation.
• 6 sources show a mix of star formation and AGN-related mechanisms contributing to radio emission.
• 3 sources indicate a core or jet-dominated (AGN-only) origin for detected radio emission.
• Three sources show evidence suggesting concurrent super-Eddington accretion and relativistic ejections.
• At LOFAR frequencies a higher fraction appears extended, while most high-frequency data are compact.
• Radio-to-mid-IR diagnostics generally do not place the whole sample in the blazar domain, with most sources not jet-dominated by radio emission.

Figure 2: Radio morphology distribution across the redshifts of the sources. C indicates compact at all frequencies observed, I is intermediate morphology detected in at least one band, and E indicates the presence of diffuse emission in at least one band.