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 archival 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 (Re ≈ 0.5–3 kpc) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick (NH > 1024 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.
Original language | English |
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Pages (from-to) | L144-L150 |
Journal | Monthly Notices of the Royal Astronomical Society: Letters |
Volume | 527 |
Issue number | 1 |
Early online date | 6 Oct 2023 |
DOIs | |
Publication status | Published - 1 Jan 2024 |
Bibliographical note
Funding Information:This work was supported by the EU H2020-MSCA-ITN-2019 Project 860744 ‘BiD4BESt: Big Data applications for black hole Evolution STudies’. DMA and AP thank the Science and Technology Facilities Council (STFC) for support from the Durham consolidated grant (ST/T000244/1). AP acknowledges partial support by STFC through grant ST/P000541/1. CH acknowledges funding from a UK Research and Innovation grant (code: MR/V022830/1). AL is partly supported by the PRIN MIUR 2017 prot. 20173ML3WW 002 ‘Opening the ALMA window on the cosmic evolution of gas, stars, and massive black holes’. DJR acknowledges the support of STFC grant NU-012097.
Funding
This work was supported by the EU H2020-MSCA-ITN-2019 Project 860744 ‘BiD4BESt: Big Data applications for black hole Evolution STudies’. DMA and AP thank the Science and Technology Facilities Council (STFC) for support from the Durham consolidated grant (ST/T000244/1). AP acknowledges partial support by STFC through grant ST/P000541/1. CH acknowledges funding from a UK Research and Innovation grant (code: MR/V022830/1). AL is partly supported by the PRIN MIUR 2017 prot. 20173ML3WW 002 ‘Opening the ALMA window on the cosmic evolution of gas, stars, and massive black holes’. DJR acknowledges the support of STFC grant NU-012097.
Keywords
- galaxies: starburst
- quasars: general
- submillimetre: galaxies
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science