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Ancient explosion in Milky Way's core lit up gas outside the galaxy

rod

Oct 22, 2019
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FYI, here is another report on the Fermi bubbles. First optical measurements of Milky Way's Fermi Bubbles probe their origin I note this in the phys.org report. "We combined those two measurements of emission and absorption to estimate the density, pressure and temperature of the ionized gas, and that lets us better understand where this gas is coming from,..But while the origin of the phenomenon has been inferred to date back several million years ago, the events that produced the bubbles remain a mystery."

My observation. Apparently an equation of state is being developed to better understand the Fermi bubbles. The precise cause for the origin of the bubbles is not solved yet or confirmed. What can be determined is that the Fermi bubbles are young in age compared to Milky Way H-R diagram ages for different star clusters like globular clusters or some open clusters like M67 as well as the time it takes for the Sun to revolve around the galaxy, i.e. the LSR and rotation period.
 
FYI, here is another report on the Fermi bubbles. First optical measurements of Milky Way's Fermi Bubbles probe their origin I note this in the phys.org report. "We combined those two measurements of emission and absorption to estimate the density, pressure and temperature of the ionized gas, and that lets us better understand where this gas is coming from,..But while the origin of the phenomenon has been inferred to date back several million years ago, the events that produced the bubbles remain a mystery."

My observation. Apparently an equation of state is being developed to better understand the Fermi bubbles. The precise cause for the origin of the bubbles is not solved yet or confirmed. What can be determined is that the Fermi bubbles are young in age compared to Milky Way H-R diagram ages for different star clusters like globular clusters or some open clusters like M67 as well as the time it takes for the Sun to revolve around the galaxy, i.e. the LSR and rotation period.
Yes, that paper is interesting too, but can only equivocate on the mechanism since they don't see Milky Way's temporary Seyfert galaxy core activity as the ionization map team did. I also think this work gives a timeline that match the 3.5 million year age suggested by the hominin illustration, but I haven't read the paper.

I don't think the Fermi Bubble insides will have an equation of state since they are dynamical and not equilibrium phenomena. But I may be mistaken.
 

rod

Oct 22, 2019
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FYI, the Fox study is found here with the arxiv report, Kinematics of the Magellanic Stream and Implications for its Ionization The arxiv report states "...the enhancement can be understood as fluorescence induced by a recent GC flare, in which the Milky Way's central supermassive black (SMBH) Sgr A* underwent an outburst several Myr ago (Bland-Hawthorn et al. 2013, 2019), releasing a burst of ionizing radiation and potentially creating the giant X-ray/ -ray Fermi Bubbles at the same time. This burst would have preferentially ionized the polar regions of the Stream since they lie in the ionization cone directly underneath the GC. The Stream would then recombine and produce the observed Halpha enhancement. In this scenario, the Magellanic Stream acts as a screen on which AGN-induced fluorescence occurs."

My note. The Fox, A. J. study proposes a Seyfert flare arising from the galaxy center to create what is observed today (including the Fermi bubbles), no indication that this is a repeating or cyclic event. After reading the arxiv copy, it seems to be a singular, catastrophic type of event proposed and not repeating. The space.com article stated "The black hole's activity likely came from a large hydrogen cloud, about 100,000 times the mass of the sun, falling onto material circling near the black hole. Ultraviolet radiation from the subsequent explosion penetrated far above and below our galaxy's plane, stripping atoms of their electrons in the Magellanic Stream."

Interesting, is this evidence for an abrupt, catastrophic, and rapid formation of the Milky Way galaxy's center? :) Other reports on the Fermi bubbles at the NASA ADS site suggest the origin of the Fermi bubbles remain elusive. Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets, "The Fermi bubbles are two giant bubbles in gamma-rays lying above and below the Galactic Center (GC). Despite numerous studies on the bubbles, their origin and emission mechanism remain elusive...This suggests that starburst or AGN winds are unlikely the origin of the bubbles in the shock scenario."
 
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FYI, the Fox study is found here with the arxiv report, Kinematics of the Magellanic Stream and Implications for its Ionization The arxiv report states "...the enhancement can be understood as fluorescence induced by a recent GC flare, in which the Milky Way's central supermassive black (SMBH) Sgr A* underwent an outburst several Myr ago (Bland-Hawthorn et al. 2013, 2019), releasing a burst of ionizing radiation and potentially creating the giant X-ray/ -ray Fermi Bubbles at the same time. This burst would have preferentially ionized the polar regions of the Stream since they lie in the ionization cone directly underneath the GC. The Stream would then recombine and produce the observed Halpha enhancement. In this scenario, the Magellanic Stream acts as a screen on which AGN-induced fluorescence occurs."

My note. The Fox, A. J. study proposes a Seyfert flare arising from the galaxy center to create what is observed today (including the Fermi bubbles), no indication that this is a repeating or cyclic event. After reading the arxiv copy, it seems to be a singular, catastrophic type of event proposed and not repeating. The space.com article stated "The black hole's activity likely came from a large hydrogen cloud, about 100,000 times the mass of the sun, falling onto material circling near the black hole. Ultraviolet radiation from the subsequent explosion penetrated far above and below our galaxy's plane, stripping atoms of their electrons in the Magellanic Stream."

Interesting, is this evidence for an abrupt, catastrophic, and rapid formation of the Milky Way galaxy's center? :) Other reports on the Fermi bubbles at the NASA ADS site suggest the origin of the Fermi bubbles remain elusive. Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets, "The Fermi bubbles are two giant bubbles in gamma-rays lying above and below the Galactic Center (GC). Despite numerous studies on the bubbles, their origin and emission mechanism remain elusive...This suggests that starburst or AGN winds are unlikely the origin of the bubbles in the shock scenario."
More detail here: https://www.sciencealert.com/astonomers-pinpoint-the-origin-of-huge-bubbles-of-gas-flowing-our-of-the-milky-way . "We can make comparisons to other galaxies by making the same kind of measurements towards the center of the Milky Way."

If it is sporadic flares, maybe they result from satellite galaxy supermassive black holes accreting, with their more compact accretion disks relatively intact relative their star and gas stripping - c.f. the Sagittarius arm itself - to the Milky Way supermassive black hole.
 

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