A refined sub-grid model for black hole accretion and AGN feedback in large cosmological simulations

In large scale cosmological hydrodynamic simulations simplified sub-grid models for gas accretion onto black holes and AGN feedback are commonly used. Such models typically depend on various free parameters, which are not well constrained. We present a new advanced model containing a more detailed description of AGN feedback, where those parameters reflect the results of recent observations. The model takes the dependency of these parameters on the black hole properties into account and describes a continuous transition between the feedback processes acting in the so-called radio-mode and quasar-mode. In addition, we implement a more detailed description of the accretion of gas onto black holes by distinguishing between hot and cold gas accretion. Our new implementations prevent black holes from gaining too much mass, particularly at low redshifts so that our simulations are now very successful in reproducing the observed present-day black hole mass function. Our new model also suppresses star formation in massive galaxies slightly more efficiently than many state-of-the-art models. Therefore, the simulations that include our new implementations produce a more realistic population of quiescent and star-forming galaxies compared to recent observations, even if some discrepancies remain. In addition, the baryon conversion efficiencies in our simulation are - except for the high mass end - consistent with observations presented in literature over the mass range resolved by our simulations. Finally, we discuss the significant impact of the feedback model on the low-luminous end of the AGN luminosity function.Comment: 25 pages, 19 figures. MNRAS accepted. Magneticum website: http://www.magneticum.or

Origin and properties of dual and offset active galactic nuclei in a cosmological simulation at z=2

In the last few years, it became possible to observationally resolve galaxies with two distinct nuclei in their centre. For separations smaller than 10kpc, dual and offset active galactic nuclei (AGN) are distinguished: in dual AGN, both nuclei are active, whereas in offset AGN only one nucleus is active. To study the origin of such AGN pairs, we employ a cosmological, hydrodynamic simulation with a large volume of (182Mpc)^3 from the set of Magneticum Pathfinder Simulations. The simulation self-consistently produces 35 resolved black hole (BH) pairs at redshift z=2, with a comoving distance smaller than 10kpc. 14 of them are offset AGN and nine are dual AGN, resulting in a fraction of (1.2 \pm 0.3)% AGN pairs with respect to the total number of AGN. In this paper, we discuss fundamental differences between the BH and galaxy properties of dual AGN, offset AGN and inactive BH pairs and investigate their different triggering mechanisms. We find that in dual AGN the BHs have similar masses and the corresponding BH from the less massive progenitor galaxy always accretes with a higher Eddington ratio. In contrast, in offset AGN the active BH is typically more massive than its non-active counterpart. Furthermore, dual AGN in general accrete more gas from the intergalactic medium than offset AGN and non-active BH pairs. This highlights that merger events, particularly minor mergers, do not necessarily lead to strong gas inflows and thus, do not always drive strong nuclear activity.Comment: 17 pages, 18 figures, accepted for publication in MNRAS, website: http://www.magneticum.or

Neutral hydrogen in galaxy clusters: impact of AGN feedback and implications for intensity mapping

By means of zoom-in hydrodynamic simulations, we quantify the amount of neutral hydrogen (H i) hosted by groups and clusters of galaxies. Our simulations, which are based on an improved formulation of smoothed particle hydrodynamics, include radiative cooling, star formation, metal enrichment and supernova feedback, and can be split into two different groups, depending on whether feedback from active galactic nuclei (AGN) is turned on or off. Simulations are analysed to account for H I self-shielding and the presence of molecular hydrogen. We find that the mass in neutral hydrogen of dark matter haloes monotonically increases with the halo mass and can be well described by a power law of the form MH I(M, Z) 1d M3/4. Our results point out that AGN feedback reduces both the total halo mass and its H i mass, although it is more efficient in removing H i. We conclude that AGN feedback reduces the neutral hydrogen mass of a given halo by ~50 per cent, with a weak dependence on halo mass and redshift. The spatial distribution of neutral hydrogen within haloes is also affected by AGN feedback, whose effect is to decrease the fraction of H i that resides in the halo inner regions. By extrapolating our results to haloes not resolved in our simulations, we derive astrophysical implications from the measurements of \u3a9H I(Z): haloes with circular velocities larger than ~25 km s-1 are needed to host H i in order to reproduce observations. We find that only the model with AGN feedback is capable of reproducing the value of \u3a9HIbHI derived from available 21 cm intensity mapping observations. \ua9 2016 The Authors

Pressure of the hot gas in simulations of galaxy clusters

14siWe analyse the radial pressure profiles, the intracluster medium (ICM) clumping factor and the Sunyaev-Zel'dovich (SZ) scaling relations of a sample of simulated galaxy clusters and groups identified in a set of hydrodynamical simulations based on an updated version of the treepm-SPH GADGET-3 code. Three different sets of simulations are performed: the first assumes non-radiative physics, the others include, among other processes, active galactic nucleus (AGN) and/or stellar feedback. Our results are analysed as a function of redshift, ICM physics, cluster mass and cluster cool-coreness or dynamical state. In general, the mean pressure profiles obtained for our sample of groups and clusters show a good agreement with X-ray and SZ observations. Simulated cool-core (CC) and non-cool-core (NCC) clusters also show a good match with real data. We obtain in all cases a small (if any) redshift evolution of the pressure profiles of massive clusters, at least back to z = 1. We find that the clumpiness of gas density and pressure increases with the distance from the cluster centre and with the dynamical activity. The inclusion of AGN feedback in our simulations generates values for the gas clumping (√{C}_{ρ }˜ 1.2 at R200) in good agreement with recent observational estimates. The simulated YSZ-M scaling relations are in good accordance with several observed samples, especially for massive clusters. As for the scatter of these relations, we obtain a clear dependence on the cluster dynamical state, whereas this distinction is not so evident when looking at the subsamples of CC and NCC clusters.openopenPlanelles, S.; Fabjan, D.; Borgani, S.; Murante, G.; Rasia, E.; Biffi, V.; Truong, N.; Ragone-Figueroa, C.; Granato, G. L.; Dolag, K.; Pierpaoli, E.; Beck, A. M.; Steinborn, Lisa K.; Gaspari, M.Planelles, S.; Fabjan, D.; Borgani, Stefano; Murante, G.; Rasia, E.; Biffi, Veronica; Truong, N.; Ragone Figueroa, C.; Granato, G. L.; Dolag, K.; Pierpaoli, E.; Beck, A. M.; Steinborn, Lisa K.; Gaspari, M

The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View

The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling. Detecting dual active galactic nuclei (AGN) – active SMBHs at projected separations larger than several parsecs – and binary AGN – probing the scale where SMBHs are bound in a Keplerian binary – is an observational challenge. The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics. The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web. This review describes the techniques used across the electromagnetic spectrum to detect dual and binary AGN candidates and proposes new avenues for their search. The current observational status is compared with the state-of-the-art numerical simulations and models for formation of dual and binary AGN. Binary SMBHs are among the loudest sources of gravitational waves (GWs) in the Universe. The search for a background of GWs at nHz frequencies from inspiralling SMBHs at low redshifts, and the direct detection of signals from their coalescence by the Laser Interferometer Space Antenna in the next decade, make this a theme of major interest for multi-messenger astrophysics. This review discusses the future facilities and observational strategies that are likely to significantly advance this fascinating field

Impaired Differentiation of Highly Proliferative ICOS+-Tregs Is Involved in the Transition from Low to High Disease Activity in Systemic Lupus Erythematosus (SLE) Patients

Dysregulations in the differentiation of CD4+-regulatory-T-cells (Tregs) and CD4+-responder-T-cells (Tresps) are involved in the development of active systemic lupus erythematosus (SLE). Three differentiation pathways of highly proliferative inducible costimulatory molecule (ICOS)+- and less proliferative ICOS−-CD45RA+CD31+-recent-thymic-emigrant (RTE)-Tregs/Tresps via CD45RA−CD31+-memory-Tregs/Tresps (CD31+-memory-Tregs/Tresps), their direct proliferation via CD45RA+CD31−-mature naïve (MN)-Tregs/Tresps, and the production and differentiation of resting MN-Tregs/Tresp into CD45RA−CD31−-memory-Tregs/Tresps (CD31−-memory-Tregs/Tresps) were examined in 115 healthy controls, 96 SLE remission patients, and 20 active disease patients using six color flow cytometric analysis. In healthy controls an appropriate sequence of these pathways ensured regular age-dependent differentiation. In SLE patients, an age-independently exaggerated differentiation was observed for all Treg/Tresp subsets, where the increased conversion of resting MN-Tregs/Tresps particularly guaranteed the significantly increased ratios of ICOS+-Tregs/ICOS+-Tresps and ICOS−-Tregs/ICOS−-Tresps during remission. Changes in the differentiation of resting ICOS+-MN-Tresps and ICOS−-MN-Tregs from conversion to proliferation caused a significant shift in the ratio of ICOS+-Tregs/ICOS+-Tresps in favor of ICOS+-Tresps and a further increase in the ratio of ICOS−-Tregs/ICOS−-Tresps with active disease. The differentiation of ICOS+-RTE-Tregs/Tresps seems to be crucial for keeping patients in remission, where their limited production of proliferating resting MN-Tregs may be responsible for the occurrence of active disease flares

Low rate of access site complications after transradial coronary catheterization: A prospective ultrasound study

Transradial artery (TRA) left heart catheterization is an increasingly used technique for both diagnostic and interventional coronary procedures. This study evaluates the incidence of access site complications in the current interventional era. A total of 507 procedures were performed under standardized conditions. Each procedure was performed using high levels of anticoagulation, hydrophilic sheaths, and short post-procedural compression times. Vascular complications were assessed one day after TRA catheterization using Duplex sonography and classified according to the necessity of additional medical intervention. A simple questionnaire helped identifying upper extremity neurologic or motor complications. Vascular complications were detected in 12 patients (2.36%): radial artery occlusion was detected in 9 patients (1.77%), 1 patient developed an AV-fistula (0.19%), and 2 patients had pseudoaneurysms (0.38%). None of the patients required specialized medical or surgical intervention. Under our procedural conditions, small radial artery diameter was the only significant predictor for the development of post-procedural vascular complications (2.11 ± 0.42 mm vs 2.52 ± 0.39 mm, p = 0.001). None of the previously reported risk factors, namely, advanced renal failure, diabetes, acuteness/complexity of procedure, or sheath and catheter size significantly influenced the rate of vascular complications. No major hematoma or local neurologic or motor complications were identified. Using current techniques and materials, we report a very low rate of local complications associated with TRA catheterization

Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?

International audienceWhich mechanism(s) are mainly driving nuclear activity in the centres of galaxies is a major unsettled question. In this study, we investigate the statistical relevance of galaxy mergers for fuelling gas onto the central few kpc of a galaxy, potentially resulting in an active galactic nucleus (AGN). To robustly address that, we employ large-scale cosmological hydrodynamic simulations from the Magneticum Pathfinder set, including models for black hole accretion and AGN feedback. Our simulations predict that for luminous AGN (⁠|$L_{\rm AGN} \gt 10^{45}\, {\rm erg\, s}^{-1}$|⁠) at z = 2, more than 50 per cent of their host galaxies have experienced a merger in the last 0.5 Gyr. These high merger fractions, however, merely reflect the intrinsically high merger fractions of massive galaxies at z = 2, in which luminous AGN preferentially occur. Apart from that, our simulations suggest that merger events are not the statistically dominant fuelling mechanism for nuclear activity over a redshift range z = 0 − 2: irrespective of AGN luminosity, less than 20 per cent of AGN hosts have on average undergone a recent merger, in agreement with a number of observational studies. The central interstellar medium conditions required for inducing AGN activity can be, but are not necessarily caused by a merger. Despite the statistically minor relevance of mergers, at a given AGN luminosity and stellar mass, the merger fractions of AGN hosts can be by up to three times higher than that of inactive galaxies. Such elevated merger fractions still point towards an intrinsic connection between AGN and mergers, consistent with our traditional expectation

Low rate of access site complications after transradial coronary catheterization: A prospective ultrasound study

Background: Transradial artery (TRA) left heart catheterization is an increasingly used technique for both diagnostic and interventional coronary procedures. This study evaluates the incidence of access site complications in the current interventional era. Methods and results: A total of 507 procedures were performed under standardized conditions. Each procedure was performed using high levels of anticoagulation, hydrophilic sheaths, and short post-procedural compression times. Vascular complications were assessed one day after TRA catheterization using Duplex sonography and classified according to the necessity of additional medical intervention. A simple questionnaire helped identifying upper extremity neurologic or motor complications. Vascular complications were detected in 12 patients (2.36%): radial artery occlusion was detected in 9 patients (1.77%), 1 patient developed an AV-fistula (0.19%), and 2 patients had pseudoaneurysms (0.38%). None of the patients required specialized medical or surgical intervention. Under our procedural conditions, small radial artery diameter was the only significant predictor for the development of post-procedural vascular complications (2.11 ± 0.42 mm vs 2.52 ± 0.39 mm, p = 0.001). None of the previously reported risk factors, namely, advanced renal failure, diabetes, acuteness/complexity of procedure, or sheath and catheter size significantly influenced the rate of vascular complications. No major hematoma or local neurologic or motor complications were identified. Conclusions: Using current techniques and materials, we report a very low rate of local complications associated with TRA catheterization