Among the foremost unsolved astrophysical problems of these decades are the structures, and working schemes of the central regions of galaxies, called “CEs” (:= Central Engines), “AGNs” (:= Active Galactic Nuclei), “UMOs” (:= Unidentified Massive Objects), or more recently “SMBHs” (:= Supermassive Black Holes).
In the (nearest) case of our own Galaxy, the CE is agreed to be the unresolved broadband point source Sgr A*, at the rotation center of the Milky Way disk, whose mass has been determined as ≳106.4 M⊙ (from the Keplerian periods of several orbiting S-stars), and whose emission is variable on all timescales down to an hour or even much shorter, down to 0.1 min, and ranges in frequency from GHz up to PeV energies. In my understanding, Sgr A* is the innermost part of our Galactic disk, a “Burning Disk”(=: BD), a flat star, of stellar mass density, stellar height (= some 1012 cm), and of radius some 1014 cm, as likewise calculated by Endrik Krügel & A.Tutukov in A&A 158, 367 (1986), and by Ian Roxburgh in MNRAS 264, 636 (1993). It is this innermost part of our Galactic disk in which its growing mass density – for inspiralling matter – reaches stellar values, and therefore starts nuclear burning – like stars – feeding our Galaxy’s BLR, and NLR, with its stormy outflow (of 10-2.5 M⊙/yr, at 103 km/s), and launching our (feeble) Galactic twin jet, (which has been mapped out to large halo distances).
None of these central structures of our Galaxy is unstable to BH formation, or has been unstable to such in the surveyable past, hence no hint at a SMBH anywhere near Sgr A*, or anywhere else in our Galaxy. Above-mentioned outflow requires a steadily blowing powerhouse – unlike what BHs could do, if such existed – as well as above-mentioned twin jet, whose source should be a heavy, magnetised rotator, like for all the other well-understood jet sources, and as well as the hard Fermi Bubbles, see Fig.1. All these facts, and reasonings, have been discussed, and documented in my books edited in 1996, 2005, and 2014, whereby my present understanding of the functioning of jet sources is first presented in Kundt & Krishna (2004). In my most recent writeup on Sgr A*, I hold 28 independent reasons against a SMBH in the core of our Milky Way.
An extreme case of an AGN has just been reported in NATURE 543, 83 (2017) by M.L. Parker et al, the Narrow Line Seyfert 1 galaxy IRAS 13224-3809, at redshift z = 0.0658, whose outflows are even relativistic, of speed ≲0.24c, and whose absorption redshifts signal nuclear burning, up to Fe XXV, or even Fe XXVI. Again, the core of this active galaxy appears to be powered by a nuclear stove, a BD, keeping its fountain-like, transrelativistic motions active throughout Myrs, or longer. A SMBH, even if such had not been ruled out in recent investigations (Kundt, 2015), would fail for many reasons. Even worse: it would have grown spectacularly via accretion, and swallowed our solar system, already a long time ago. Similar well-studied galaxy-scale fountain motions have been recently encountered in the nearby massive, active galaxies NGC 3842, 4859, and 1600, as well as in Mrk 1018, and in the brightest cluster galaxy in Abell 2597. Swallowing BHs would have prevented their steady powering.
Another strong (statistical) argument against the presence of SMBHs in the centers of active galaxies is the monotonic decline of their masses with cosmic evolution, from an initial ≲1010 M⊙, near z = 4, to a present ≲107 M⊙, as shown by the SDSS plot, in Fig.2; SMBH masses should have grown, not shrunken with time.
In summary: I feel like the little boy in the fairytale of the emperor’s new dresses: I see BDs, where most other people (have learned to) see SMBHs. In my view, the cores of galactic disks burn even faster, and even more intensely than their surroundings, like BDs. They re-expand the infalling matter.
- Kundt, W., 1996, ed.: Jets from Stars and Galactic Nuclei, Lecture Notes in Physics 471, Springer, 1-290.
- Kundt, W., 2005: Astrophysics, A New Approach, Springer, 1-223.
- Kundt, W., Krishna, Gopal, 2004: The Physics of ExB-drifting Jets, J. Astrophys. Astr. 25, 115-127.
- Kundt, W., 2013: Our Galactic Center – the nearest Burning Disk, Vulcano Workshop 2012, ACTA POLYTECHNICA 53, Supplement 2013, pp. 506-512.
- Kundt, W., Marggraf, Ole, 2014: Physikalische Mythen auf dem Prüfstand, Springer, 1-445.
- Kundt, W., 2015: A brief Observational History of the Black-Hole Spacetimes, Advances in Mathematical Physics, doi:10.1155/2015/617128.
- Kundt, W., 2017: Sgr A*, the best-sampled of all AGN, PoS(MULTIF17)050, 1-12 (2017).
- Kundt, W., 2018: Gravitational Astrophysics, PoS(MULTIF18)016.