A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems
A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems
To understand the active galactic nuclei (AGNs) phenomenon and their impact on the evolution of galaxies, a complete AGN census is required; however, finding heavily obscured AGNs is observationally challenging. Here we use the deep and extensive multiwavelength data in the COSMOS field to select a complete sample of 578 infrared (IR) quasars (L
AGN,IR > 10
45 erg s
−1) at z < 3, with minimal obscuration bias, using detailed UV-to-far-IR spectral energy distribution (SED) fitting. We complement our SED constraints with X-ray and radio observations to further investigate the properties of the sample. Overall, 322 of the IR quasars are detected by Chandra and have individual X-ray spectral constraints. From a combination of X-ray stacking and L
2−10 kev – L
6 μm analyses, we show that the majority of the X-ray faint and undetected quasars are heavily obscured (many are likely Compton thick), highlighting the effectiveness of the mid-IR band to find obscured AGNs. We find that 355 (≈61 per cent) IR quasars are obscured (N
H > 10
22 cm
−2) and identify differences in the average properties between the obscured and unobscured quasars: (1) obscured quasars have star formation rates ≈3 times higher than unobscured systems for no significant difference in stellar mass and (2) obscured quasars have stronger radio emission than unobscured systems, with a radio-loudness parameter ≈ 0.2 dex higher. These results are inconsistent with a simple orientation model but in general agreement with either extreme host-galaxy obscuration towards the obscured quasars or a scenario where obscured quasars are an early phase in the evolution of quasars.
astro-ph.GA, quasars: general, infrared: galaxies, galaxies: active
2577-2598
Andonie, Carolina
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Alexander, David M.
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Rosario, David
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Laloux, Brivael
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Georgakakis, Antonis
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Morabito, Leah K.
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Villforth, Carolin
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Avirett-Mackenzie, Mathilda
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Rivera, Gabriela Calistro
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Moro, Agnese Del
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Fotopoulou, Sotiria
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Harrison, Chris
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Lapi, Andrea
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Petley, James
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Petter, Grayson
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Shankar, Francesco
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1 December 2022
Andonie, Carolina
9af94180-efac-40de-8036-720cdb3838f2
Alexander, David M.
49c9b059-8447-4859-8242-fa6bb8f267c7
Rosario, David
c94b3793-e8c1-4ad4-9c9f-fe9892eb938b
Laloux, Brivael
a8be06b5-4182-4045-b14c-193c33134a9a
Georgakakis, Antonis
9cab20e1-44db-4d30-a608-8b420c54a3b0
Morabito, Leah K.
ba511a9e-71f5-40ea-991a-a205bb125e03
Villforth, Carolin
6853642c-f699-429a-bfb5-dc5c485f5934
Avirett-Mackenzie, Mathilda
48a739d7-7058-4b37-a0b1-5c58862b32bf
Rivera, Gabriela Calistro
43947a52-bab7-4cf8-ac92-135086562dce
Moro, Agnese Del
6e1d7c6d-ffb1-441a-958a-3fb565326974
Fotopoulou, Sotiria
f3ddc462-b679-43b2-ae6c-d10fc679c984
Harrison, Chris
d34df276-e5cb-4cbe-8445-78cfe485e849
Lapi, Andrea
126b5f87-60fa-4a57-8b84-802d5ffb1f17
Petley, James
3fca1ef4-57ee-47b2-af52-d14918790489
Petter, Grayson
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Shankar, Francesco
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Andonie, Carolina, Alexander, David M., Rosario, David, Laloux, Brivael, Georgakakis, Antonis, Morabito, Leah K., Villforth, Carolin, Avirett-Mackenzie, Mathilda, Rivera, Gabriela Calistro, Moro, Agnese Del, Fotopoulou, Sotiria, Harrison, Chris, Lapi, Andrea, Petley, James, Petter, Grayson and Shankar, Francesco
(2022)
A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems.
Monthly Notices of the Royal Astronomical Society, 517 (2), .
(doi:10.1093/mnras/stac2800).
Abstract
To understand the active galactic nuclei (AGNs) phenomenon and their impact on the evolution of galaxies, a complete AGN census is required; however, finding heavily obscured AGNs is observationally challenging. Here we use the deep and extensive multiwavelength data in the COSMOS field to select a complete sample of 578 infrared (IR) quasars (L
AGN,IR > 10
45 erg s
−1) at z < 3, with minimal obscuration bias, using detailed UV-to-far-IR spectral energy distribution (SED) fitting. We complement our SED constraints with X-ray and radio observations to further investigate the properties of the sample. Overall, 322 of the IR quasars are detected by Chandra and have individual X-ray spectral constraints. From a combination of X-ray stacking and L
2−10 kev – L
6 μm analyses, we show that the majority of the X-ray faint and undetected quasars are heavily obscured (many are likely Compton thick), highlighting the effectiveness of the mid-IR band to find obscured AGNs. We find that 355 (≈61 per cent) IR quasars are obscured (N
H > 10
22 cm
−2) and identify differences in the average properties between the obscured and unobscured quasars: (1) obscured quasars have star formation rates ≈3 times higher than unobscured systems for no significant difference in stellar mass and (2) obscured quasars have stronger radio emission than unobscured systems, with a radio-loudness parameter ≈ 0.2 dex higher. These results are inconsistent with a simple orientation model but in general agreement with either extreme host-galaxy obscuration towards the obscured quasars or a scenario where obscured quasars are an early phase in the evolution of quasars.
Text
2209.13321v1
- Author's Original
UNSPECIFIED
stac2800
- Version of Record
More information
Accepted/In Press date: 26 September 2022
Published date: 1 December 2022
Additional Information:
Funding Information:
We thank the referee for his positive and constructive comments. We would also like to express our gratitude to Philip Hopkins for useful research discussions. We want to thank Mara Salvato for sharing her redshift compilation in the COSMOS field, and Stefano Marchesi and Giorgio Lanzuisi for sharing their X-ray spectral fitting results in COSMOS. This work has been supported by the EU H2020-MSCAITN-2019 Project 860744 ‘BiD4BESt: Big Data applications for black hole Evolution STudies.’ DMA thanks the Science Technology Facilities Council (STFC) for support from the Durham consolidated grant (ST/T000244/1). CH acknowledges funding from an United Kingdom 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’. JP acknowledges support from STFC grants ST/T506047/1 and ST/V506643/1.
Publisher Copyright:
© 2022 The Author(s).
Keywords:
astro-ph.GA, quasars: general, infrared: galaxies, galaxies: active
Identifiers
Local EPrints ID: 472493
URI: http://eprints.soton.ac.uk/id/eprint/472493
ISSN: 1365-2966
PURE UUID: 1b2e77a8-54d4-4dd6-92c4-65fb14dfd081
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Date deposited: 06 Dec 2022 17:53
Last modified: 11 Jul 2024 05:17
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Contributors
Author:
Carolina Andonie
Author:
David M. Alexander
Author:
David Rosario
Author:
Brivael Laloux
Author:
Antonis Georgakakis
Author:
Leah K. Morabito
Author:
Carolin Villforth
Author:
Mathilda Avirett-Mackenzie
Author:
Gabriela Calistro Rivera
Author:
Agnese Del Moro
Author:
Sotiria Fotopoulou
Author:
Chris Harrison
Author:
Andrea Lapi
Author:
James Petley
Author:
Grayson Petter
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