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EXAPTATION. “Evolution works best when it does not need to generate a whole new active site from scratch. Instead, evolution can generate a new enzyme from one that is “close”, that is, shares elements of mechanism or machinery from which the new activity can be built. Nature co-opts old machinery to do new jobs.” https://lnkd.in/d2-p85M View in LinkedIn

ACTIVE GALACTIC NUCLEI. “The disc becomes unstable if the ratio of dark matter mass to disc mass becomes smaller than a critical value, and give the following parametrization for the onset of disc instabilities.” https://lnkd.in/d9JV8md View in LinkedIn

OTHER FACTORS. “This suggests that moderately luminous AGN may undergo a ‘main-sequence’ secular growth, e.g. their nuclear activity might be additionally driven by disc instabilities.” (AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

LUMINOSITY AND GROWTH. “Various observational studies suggest that moderately luminous AGN are typically not major-merger driven, at z < 1, and interestingly also at z ≈ 2 as they do not find more morphological distortions for AGN host galaxies than for inactive galaxies.” (AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

“THE GOAL of this work is to explore the interplay of different physical processes that determine the masses of seed BHs, the triggering of AGN activity and the efficiency of gas accretion during the active phases of BHs, with the aim of understanding the physical origin of the observed downsizing trend in BH growth.” (BH = black hole; AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

STELLAR SEEDING. Our model “does not produce enough very luminous QSOs at high redshift (z > 5). Our third, main conclusion is that a heavy seeding mechanism for black holes provides a physically motivated way to increase the predicted number density of very luminous QSOs at high redshift, in line with observations.” (QSO = Quasi Stellar Objects). https://lnkd.in/d9JV8md View in LinkedIn

BLACK HOLE ACCRETION. “However, the observational situation remains murky. Observational studies have repeatedly failed to find evidence for a statistically significant enhancement of merger-related signatures, such as close pairs or morphological disturbance.” https://lnkd.in/d9JV8md View in LinkedIn

TWO FACTORS. “Our results therefore favour a ‘hybrid’ picture in which major merger events are the main driver of luminous AGN, especially at high redshift, while disc instabilities are the main mechanism powering moderately luminous Seyfert galaxies at low redshift.” (AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

BLACK HOLE GROWTH. “Mergers appear to be a physically well-motivated candidate for producing this dramatic effect, and semi-empirical calculations have shown that there is a statistical consistency between the observed merger rate and the observed AGN duty cycle and luminosity function (LF), suggesting that it is at least possible that these processes are causally linked.” (AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

How a feather in the wild, the rain, and mud, can retain such a perfect form has to do with two things: its barbed structure which hooks the pieces in place, and the fine coating of natural water-resistant talcum powder from the bird’s skin. View in LinkedIn