Month: September 2022

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

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

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

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

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

FEEDING THE BEAST. “Another matter of vigorous debate is the process or processes that trigger and regulate accretion on to the central SMBH. As noted above, the most luminous observed quasars require accretion rates such that ∼10(8)–10(9) M⊙ of gas must be funnelled on to the BH over a time-scale of

NEW LAWS. “The lowest temperature currently achieved in laboratories is of the order of picokelvins, i.e. many orders lower than the average temperature of the universe T = 2.73 K. At these temperatures we gain access to a world of exotic phenomena and physics that was once ordinary becomes extraordinary.” The laws of physics at extreme temperatures, densities and pressures are unknown, all common in the cosmos. https://lnkd.in/d63FZYV View in LinkedIn

The microclimate afforded by trees is physically similar to swimming in the sea and coming across layers of unmixed water at different temperatures. 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

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