ATRONOMY – TELLAR PHYIC (48) CALCULATOR
Agn Black Hole Mass
A precise tool.
What is the Agn Black Hole Mass & How does it work?
Active Galactic Nuclei (AGN) host super‑massive black holes whose masses can be estimated from the properties of the surrounding broad‑line region (BLR). The BLR radius scales with the AGN continuum luminosity because a brighter nucleus ionises gas farther out, a relationship that is calibrated with reverberation‑mapping campaigns.
Assuming the BLR gas is virialised, the black‑hole mass follows the virial theorem: the gravitational force balances the kinetic energy of the orbiting clouds. By measuring the width of a broad emission line (often expressed as the full‑width at half‑maximum, FWHM) we obtain a proxy for the velocity dispersion (Delta V). Combining this with the luminosity‑derived radius yields a direct mass estimate.
The practical formula used in most single‑epoch estimators is
This expression can be rewritten in solar‑mass units after inserting the empirical radius‑luminosity relation (R_{rm BLR}=a,(L_{5100}/10^{44},mathrm{erg,s^{-1}})^{b}) where (a) is in light‑days and (b) is typically ≈0.5.
M_{BH}=frac{f,R_{rm BLR},(Delta V)^2}{G}
M_{BH} = black‑hole mass (g); f = dimensionless virial factor (geometry); R_{rm BLR} = BLR radius (cm); Delta V = velocity dispersion (cm s⁻¹); G = gravitational constant (cgs).
Parameters
Result
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Frequently Asked Questions
What is the relationship between the BLR radius and AGN continuum luminosity?
The BLR radius scales with the AGN continuum luminosity because brighter nuclei ionize gas farther out.
How does the virial theorem apply to black hole mass estimation?
The virial theorem states that gravitational force balances the kinetic energy of orbiting clouds, allowing for black hole mass calculation.
What is reverberation mapping in AGN studies?
Reverberation mapping calibrates the relationship between BLR radius and AGN continuum luminosity to estimate black hole masses.
Why is the gas assumed to be virialised in this calculation?
Assuming virialisation simplifies the calculations by balancing gravitational force with kinetic energy of orbiting clouds.
Can this calculator estimate black hole masses for any AGN?
This calculator is designed for AGNs where the BLR gas properties and continuum luminosity are known and applicable to the virial theorem.
What are the limitations of using this calculator?
The accuracy depends on assumptions like virialisation and may not be suitable for all AGN types or environments.
How do changes in AGN continuum luminosity affect black hole mass estimates?
Increased continuum luminosity can ionize gas farther out, increasing the BLR radius and potentially affecting black hole mass estimations.
Results are for informational purposes only and do not constitute professional advice.