The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation
The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation
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DOI：
10.1093/mnras/stab1998
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发表时间：
2021-07
影响因子：
4.8
通讯作者：
C. Macfarlane;P. Best;J. Sabater;G. Gürkan;M. Jarvis;H. Röttgering;R. D. Baldi;G. Calistro Rivera-G.-Calistro Rive
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文献类型：
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作者：
C. Macfarlane;P. Best;J. Sabater;G. Gürkan;M. Jarvis;H. Röttgering;R. D. Baldi;G. Calistro Rivera-G.-Calistro Rive
我们研究了来自斯隆数字巡天的约42000个类星体的射电发射分布，这些类星体是在LOFAR两米巡天（LoTSS）中测量的。我们提出了一个类星体的射电亮度分布模型，该模型假设每个类星体都显示两个射电发射源的叠加：活动星系核（喷流）和恒星形成。我们的双组分模型与观测到的射电通量密度分布在广泛的红移和类星体光学光度范围内提供了很好的匹配；这表明喷射发射机制在所有类星体中都起作用，只是动力效率不同。喷流功率的广泛分布允许在“无线电安静”和“无线电大声”类星体制度之间的平稳过渡，而不需要任何明确的双峰性。最佳拟合模型参数表明，类星体宿主星系的恒星形成速率与类星体亮度密切相关，并且至少在z ～ 2范围内随着红移而增加。对于恒星形成速率尺度为$L_{\rm bol}^{\alpha } (1+z)^{\beta }$的模型，我们发现α = 0.47±0.01,β = 1.61±0.05，与远红外研究一致。类星体在z = 0.5时占宇宙恒星形成速率密度的约0.15％，在z ～ 2时上升到0.4％。典型的射电喷流功率分别随光学光度和黑洞质量的增加而增加，但不随红移而变化，这表明射电喷流的产生受内在特性的控制。我们讨论了这些结果对触发类星体活动和喷射的影响。
We examine the distribution of radio emission from ∼42 000 quasars from the Sloan Digital Sky Survey, as measured in the LOFAR Two-metre Sky Survey (LoTSS). We present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: active galactic nuclei (jets) and star formation. Our two-component model provides an excellent match to the observed radio flux density distributions across a wide range of redshifts and quasar optical luminosities; this suggests that the jet-launching mechanism operates in all quasars but with different powering efficiency. The wide distribution of jet powers allows for a smooth transition between the ‘radio-quiet’ and ‘radio-loud’ quasar regimes, without need for any explicit bimodality. The best-fitting model parameters indicate that the star formation rate of quasar host galaxies correlates strongly with quasar luminosity and also increases with redshift at least out to z ∼ 2. For a model where star formation rate scales as $L_{\rm bol}^{\alpha } (1+z)^{\beta }$, we find α = 0.47 ± 0.01 and β = 1.61 ± 0.05, in agreement with far-infrared studies. Quasars contribute ≈0.15 per cent of the cosmic star formation rate density at z = 0.5, rising to 0.4 per cent by z ∼ 2. The typical radio jet power is seen to increase with both increasing optical luminosity and black hole mass independently, but does not vary with redshift, suggesting intrinsic properties govern the production of the radio jets. We discuss the implications of these results for the triggering of quasar activity and the launching of jets.