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ORIGIN OF BLACK HOLES. “However, several aspects of the physics of BH growth and formation remain poorly understood. First, there are active ongoing debates about when and how seed BHs form: either via a direct collapse of cold gas clouds leading to massive seeds of ∼10(4)–10(5) M⊙, or via stellar remnants from Population III stars, resulting in low-mass (∼100 M⊙) BH seeds.” (BH = black hole; (M⊙ = solar mass). https://lnkd.in/d9JV8md View in LinkedIn

RADIO JETS. “Some mechanism must be adopted that reduces or stops gas cooling and accretion in massive dark matter haloes. Many models assume that low levels of accretion on to SMBH can produce radio jets that heat the surrounding hot halo thereby inhibiting cooling flows, preventing overmassive galaxies from forming and quenching star formation in massive galaxies, leading to more observationally consistent colour–magnitude or star formation rate–stellar mass relationships.” (SMBH = supermassive black hole). https://lnkd.in/d9JV8md View in LinkedIn

INSATIABLE GROWTH. “One must invoke a physical mechanism that can feed large amounts of gas on to the central BH within a short time. Galaxy–galaxy mergers are a popular (though not universally adopted) way to remove angular momentum from the gas and efficiently drive it to the centre of the galaxy.” (BH = black hole). https://lnkd.in/d9JV8md View in LinkedIn

GROWTH BY WINDS. “Self-regulated BH growth, perhaps via radiation-pressure-driven winds is a widely adopted means of obtaining the observed tight relationship between BH mass and spheroid mass (although some models simply assume this relationship without invoking a physical mechanism).” (BH = black hole). https://lnkd.in/d9JV8md View in LinkedIn

BRIGHT ACCRETION. “By estimating the total energy radiated by AGN over their whole lifetime, it can be shown that nearly all the mass seen in dormant BHs today can be accumulated during the periods of observed bright AGN activity. This implies that there is not a great deal of room for ‘dark’ or obscured accretion.” (BH = black hole; AGN = active galactic nuclei). https://lnkd.in/d9JV8md View in LinkedIn

Mr. Praline: (yelling and hitting the cage repeatedly) 'ELLO POLLY!!!!! Testing! Testing! Testing! Testing! This is your nine o'clock alarm call!" "(Takes parrot out of the cage and thumps its head on the counter. Throws it up in the air and watches it plummet to the floor.) https://lnkd.in/dt_3NP6 View in LinkedIn

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