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Published August 21, 2018 | Submitted + Supplemental Material + Published
Journal Article Open

Is there a relationship between AGN and star formationin IR-bright AGNs?

Abstract

We report the relationship between the luminosities of active galactic nuclei (AGNs) and the rates of star formation (SF) for a sample of 323 far-infrared (FIR)-detected AGNs. This sample has a redshift range of 0.2 < z < 2.5, and spans three orders of magnitude in luminosity, L_X ∼10^(42−45) erg s^(−1). We find that in AGN hosts, the total infrared (IR) luminosity (8–1000 µm) has a significant AGN contribution (average ∼ 20 per cent), and we suggest using the FIR luminosity (30–1000 µm) as a more reliable star formation rate (SFR) estimator. We conclude that monochromatic luminosities at 60 and 100 µm are also good SFR indicators with negligible AGN contributions, being less sensitive than integrated IR luminosities to the shape of the AGN spectral energy distribution (SED), which is uncertain at λ > 100µm. Significant bivariate L_X−L_(IR) correlations are found, which remain significant in the combined sample when using residual partial correlation analysis to account for the inherent redshift dependence. No redshift or mass dependence is found for the ratio between SFR and black hole accretion rate (BHAR), which has a mean and scatter of log (SFR/BHAR) = 3.1 ± 0.5, agreeing with the local mass ratio between supermassive black hole and host galaxies. The large scatter in this ratio and the strong AGN–SF correlation found in these IR-bright AGNs are consistent with the scenario of an AGN–SF dependence on a common gas supply, regardless of the evolutionary model.

Additional Information

© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices). Accepted 2018 May 17. Received 2018 May 17; in original form 2017 May 13. Published: 18 May 2018. We thank the anonymous referee for constructive and detailed comments that improved and clarified this paper. YSD would like to thank Lee Armus, Nick Scoville, Phillip Hopkins, Chris Hayward, Xiangcheng Ma, and Ranga R. Chary for helpful discussions. BJW gratefully acknowledged the support of NASA Contract NAS8-03060 (CXC). This work is sponsored in part by the Chinese Academy of Sciences (CAS), through a grant to the CAS South America Center for Astronomy (CASSACA) based in Santiago, Chile. This research has made use of data from HerMES project (http://hermes.sussex.ac.uk/). HerMES is a Herschel Key Programme utilizing Guaranteed Time from the SPIRE instrument team, ESAC scientists and a mission scientist. The HerMES data was accessed through the Herschel Database in Marseille (HeDaM - http://hedam.lam.fr) operated by CeSAM and hosted by the Laboratoire d'Astrophysique de Marseille.

Attached Files

Published - sty1341.pdf

Submitted - 1511.06761v2.pdf

Supplemental Material - sty1341_supplemental_file.zip

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Additional details

Created:
August 19, 2023
Modified:
October 23, 2023