In the standard quasar model, the accretion disc obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at z ≈1–3 and archi v al Atacama Large Millimetre/submillimetre Array submillimetre host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate star formation rates (SFR) and ISM column densities for the IR quasars and a control sample of submillimetre galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to SFR ≈300 M yr −1 , and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at SFR 300 M yr −1 , the SMGs and IR quasars have similarly compact submillimetre sizes ( R e ≈0 . 5 –3 kpc ) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick ( N H > 10 24 cm −2 ) levels in extreme cases. Based on our results, we infer that ≈10 –30 per cent of the IR quasars with SFR 300 M yr −1 are obscured solely by the ISM.

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts / Andonie, C.; Alexander, D. M.; Greenwell, C.; Puglisi, A.; Laloux, B.; Alonso-Tetilla, A. V.; Rivera, G. C.; Harrison, C.; Hickox, R. C.; Kaasinen, M.; Lapi, A.; Lopez, I. E.; Petter, G.; Almeida, C. R.; Rosario, D. J.; Shankar, F.; Villforth, C.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS. - ISSN 1745-3933. - 527:1(2024), pp. 144-150. [10.1093/mnrasl/slad144]

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts

Lapi A.;
2024-01-01

Abstract

In the standard quasar model, the accretion disc obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at z ≈1–3 and archi v al Atacama Large Millimetre/submillimetre Array submillimetre host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate star formation rates (SFR) and ISM column densities for the IR quasars and a control sample of submillimetre galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to SFR ≈300 M yr −1 , and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at SFR 300 M yr −1 , the SMGs and IR quasars have similarly compact submillimetre sizes ( R e ≈0 . 5 –3 kpc ) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick ( N H > 10 24 cm −2 ) levels in extreme cases. Based on our results, we infer that ≈10 –30 per cent of the IR quasars with SFR 300 M yr −1 are obscured solely by the ISM.
2024
527
1
144
150
https://arxiv.org/abs/2310.02330
Andonie, C.; Alexander, D. M.; Greenwell, C.; Puglisi, A.; Laloux, B.; Alonso-Tetilla, A. V.; Rivera, G. C.; Harrison, C.; Hickox, R. C.; Kaasinen, M.; Lapi, A.; Lopez, I. E.; Petter, G.; Almeida, C. R.; Rosario, D. J.; Shankar, F.; Villforth, C.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/135157
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