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Register a new userA binning-free method reveals a continuous relationship between galaxies AGN power and offset from main sequence
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Studies investigating the relationship between AGN power and the star formation rates (SFRs) of their host galaxies often rely on averaging techniques -- such as stacking -- to incorporate information from non-detections. However, averages, and especially means, can be strongly affected by outliers and can therefore give a misleading indication of the typical case. Recently, a number of studies have taken a step further by binning their sample in terms of AGN power (approximated by the 2-10keV luminosity of the AGN), and investigating how the SFR distribution differs between these bins. These bin thresholds are often weakly motivated, and binning implicitly assumes that sources within the same bin have similar (or even identical) properties. In this paper, we investigate whether the distribution of host SFRs -- relative to the locus of the star-forming main sequence (i.e., $R_{rm MS}$) -- changes continuously as a function of AGN power. We achieve this by using a hierarchical Bayesian model that completely removes the need to bin in AGN power. In doing so, we find strong evidence that the $R_{rm MS}$ distribution changes with 2-10keV X-ray luminosity. The results suggest that higher X_ray luminosity AGNs have a tighter physical connection to the star-forming process than lower X-ray luminosity AGNs, at least within the $0.8 < z < 1.2$ redshift range considered here.
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Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P_jet, and synchrotron luminosity, P_rad. We expand the sample presented in Birzan et al. (2008) to lower radio power by incorporating measurements for 21 gEs to determine if the Birzan et al. (2008) P_jet-P_rad scaling relations are continuous in form and scatter from giant elliptical galaxies (gEs) up to brightest cluster galaxies (BCGs). We find a mean scaling relation of P_jet approximately 5.8x10^43 (P_rad/10^40)^(0.70) erg/s which is continuous over ~6-8 decades in P_jet and P_rad with a scatter of approximately 0.7 dex. Our mean scaling relationship is consistent with the model presented in Willott et al. (1999) if the typical fraction of lobe energy in non-radiating particles to that in relativistic electrons is > 100. We identify several gEs whose radio luminosities are unusually large for their jet powers and have radio sources which extend well beyond the densest parts of their X-ray halos. We suggest that these radio sources are unusually luminous because they were unable to entrain appreciable amounts of gas.
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In this study we demonstrate that stellar masses of galaxies (Mstar) are universally correlated through a double power law function with the product of the dynamical velocities (Ve) and sizes to one-fourth power (Re^0.25) of galaxies, both measured at the effective radii. The product VeRe^0.25 represents the fourth root of the total binding energies within effective radii of galaxies. This stellar mass-binding energy correlation has an observed scatter of 0.14 dex in log(VeRe^0.25) and 0.46 dex in log(Mstar). It holds for a variety of galaxy types over a stellar mass range of nine orders of magnitude, with little evolution over cosmic time. A toy model of self-regulation between binding energies and supernovae feedback is shown to be able to reproduce the observed slopes, but the underlying physical mechanisms are still unclear. The correlation can be a potential distance estimator with an uncertainty of 0.2 dex independent of the galaxy type.
We summarize the results from numerical simulations of mass outflows from AGN. We focus on simulations of outflows driven by radiation from large-scale inflows. We discuss the properties of these outflows in the context of the so-called AGN feedback problem. Our main conclusion is that this type of outflows are efficient in removing matter but inefficient in removing energy.
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