H1821+643

H1821+643
H1821+643
Observation data (Epoch J2000.0)
Constellation	Draco
Right ascension	18h 21m 57.2365s
Declination	+64° 20′ 36.226″
Redshift	0.2970
Distance	3.4 gigalight-years (1.0 Gpc)
Type	Quasar
Apparent magnitude (V)	14.24
	See also: Quasar, List of quasars

H1821+643 is an extraordinarily luminous, radio-quiet quasar in the constellation of Draco. ^[1] The associated Active Galactic Nucleus (AGN) is situated in the Brightest Central Galaxy (BCG) of a massive ( $\sim 6.3\times 10^{14}M_{\odot }$ ), strong cooling flow cluster, CL 1821+64.^[2] Russel et al (2010) spatially isolated its X-ray signal from the surrounding cluster in Chandra X-ray observatory observations and computed $L_{\odot }=10^{47}erg/s$ from the observed X-ray luminosity. ^[2]

Supermassive Black Hole edit

The SMBH centred in CL 1821+64 is believed to be among the most massive in the known Universe.^[2] A variety of techniques have found different values for the mass. 5 studies found values $M_{BH}\sim 10^{9}M_{\odot }$ . Kim et al (2004) and Floyd et al (2008) used galactic bulge luminosity fits derived from Hubble data to find $10^{9}M_{\odot }$ and $3\times 10^{9}M_{\odot }$ respectively. Russell et al (2010) provided a rough estimate of $M_{BH}\sim 3\times 10^{9}$ M_☉.^[2] This was an underestimate with $\log(\Delta M_{BH}/M_{\odot })\geq 1$ . Kolman et al (1991) and Shapovalova (2016) independently modelled the quasar UV spectrum to find $M_{BH}\sim 3\times 10^{9}M_{\odot }$ . Capellupo et al (2017) found $M_{BH}\sim 3\times 10^{9}$ using $H\beta$ line emissions. 2 independent X-ray studies found significantly higher values. Reynolds et al (2014) found $6\times 10^{9}M_{\odot }$ by modelling reflection from the accretion disc and Walker et al found $3\times 10^{10}M_{\odot }$ by modelling the interaction of the black hole with the Intracluster medim (ICM) as a Compton-cooled feeding cycle. $M_{BH}$ is in the range $\log(M_{BH}/M_{\odot })\sim 9.2-10.5$ .^[2]

The Schwarzschild diameter of this black hole is between 9.4 terametres (63 AU) and 188 terametres (1,260 AU), which is about 16 times the diameter of Pluto's orbit. If the hole were a Euclidean sphere, the average density would be 18 g/m³, $\sim 1\%$ the density of air at sea level on Earth.^[a]

Footnotes edit

^ Mass 3.0×10¹⁰ * 2.0×10³⁰=6.0×10⁴⁰ kg. Volume at radius 8.6×10¹³ m is 2.66×10⁴² m³.

References edit

^ Walker, S. A.; Fabian, A. C.; Russell, H. R.; Sanders, J. S. (2014). "The effect of the quasar H1821+643 on the surrounding intracluster medium: Revealing the underlying cooling flow". Monthly Notices of the Royal Astronomical Society. 442 (3): 2809. arXiv:1405.7522. Bibcode:2014MNRAS.442.2809W. doi:10.1093/mnras/stu1067.
^ ^a ^b ^c ^d ^e Sisk-Reynés, J.; Reynolds, C. S.; Matthews, J. H.; Smith, R. N. (2022). "Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643". arXiv:1405.7522.

External links edit

Simbad, SIMBAD
NED, NED, NASA/IPAC Extragalactic Database

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[3] Mass 3.0×10¹⁰ * 2.0×10³⁰=6.0×10⁴⁰ kg. Volume at radius 8.6×10¹³ m is 2.66×10⁴² m³.

[joe-1] Walker, S. A.; Fabian, A. C.; Russell, H. R.; Sanders, J. S. (2014). "The effect of the quasar H1821+643 on the surrounding intracluster medium: Revealing the underlying cooling flow". Monthly Notices of the Royal Astronomical Society. 442 (3): 2809. arXiv:1405.7522. Bibcode:2014MNRAS.442.2809W. doi:10.1093/mnras/stu1067.

[J_S-R-2] Sisk-Reynés, J.; Reynolds, C. S.; Matthews, J. H.; Smith, R. N. (2022). "Evidence for a moderate spin from X-ray reflection of the high-mass supermassive black hole in the cluster-hosted quasar H1821+643". arXiv:1405.7522.

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