Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

The star formation rates of QSOs

Symeonidis, M., Maddox, N., Jarvis, M. J., Michalowski, M. J., Andreani, P., Clements, D. L., De Zotti, G., Duivenvoorden, S., Gonzalez-Nuevo, J., Ibar, E., Ivison, R. J., Leeuw, L., Page, M. J., Shirley, R., Smith, M. W. L. ORCID: and Vaccari, M. 2022. The star formation rates of QSOs. Monthly Notices of the Royal Astronomical Society 514 (3) , 4450–4464. 10.1093/mnras/stac1359

[thumbnail of Post-print.pdf]
PDF - Accepted Post-Print Version
Download (24MB) | Preview


We examine the far-infrared (FIR) properties of a sample of 5391 optically selected QSOs in the 0.5 < z < 2.65 redshift range down to log [νLν, 2500(erg s−1)] > 44.7, using SPIRE data from Herschel-ATLAS. We split the sample in a grid of 74 luminosity–redshift bins and compute the average optical–IR spectral energy distribution (SED) in each bin. By normalizing an intrinsic active galactic nucleus (AGN) template to the AGN optical power (at 5100 Å), we decompose the total IR emission (LIR; 8–1000 µm) into an AGN (LIR, AGN) and star-forming component (LIR, SF). We find that the AGN contribution to LIR increases as a function of AGN power, manifesting as a reduction of the ‘FIR bump’ in the average QSO SEDs. We note that LIR, SF does not correlate with AGN power; the mean star formation rates (SFRs) of AGN host galaxies are a function of redshift only and they range from ∼6 M⊙ yr−1 at z ∼ 0 to a plateau of ≲ 200 M⊙ yr−1 at z ∼ 2.6. Our results indicate that the accuracy of FIR emission as a proxy for SFR decreases with increasing AGN luminosity. We show that, at any given redshift, observed trends between IR luminosity (whether monochromatic or total) and AGN power (in the optical or X-rays) can be explained by a simple model which is the sum of two components: (i) the IR emission from star formation, uncorrelated with AGN power and (ii) the IR emission from AGN, directly proportional to AGN power in the optical or X-rays.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 6 January 2023
Date of Acceptance: 11 May 2022
Last Modified: 17 Nov 2023 19:09

Actions (repository staff only)

Edit Item Edit Item


Downloads per month over past year

View more statistics