Accretion disk around galaxy NGC 4261

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Discussion Overview

The discussion revolves around the characteristics of the accretion disk surrounding the galaxy NGC 4261, focusing on the temperature gradients within the disk and the expected radiation from the dust present in the outer regions.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that the accretion disk consists of a cold outer region and an ultra-hot inner region near the black hole, questioning why the heated dust does not radiate brightly in UV or X-rays.
  • Another participant provides a link to an X-ray image of NGC 4261, suggesting that there is observable radiation from the galaxy.
  • The initial participant later clarifies that the image they referenced was taken at visible wavelengths, questioning if this explains the lack of brightness from the dust material.
  • Another participant confirms that dust radiates at the frequency of light it receives, implying that the observed wavelengths affect the visibility of the dust's radiation.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between the observed wavelengths and the dust's radiation properties, but the initial question regarding the expected brightness of the heated dust remains unresolved.

Contextual Notes

The discussion does not address the specific mechanisms of radiation from the dust or the detailed properties of the accretion disk, leaving assumptions about the temperature and radiation processes unexamined.

Who May Find This Useful

Astronomy enthusiasts, astrophysicists, and students interested in accretion disks, galaxy formation, and radiation processes in astrophysical contexts may find this discussion relevant.

JeffOCA
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Hello,

When you look at the accretion disk around NGC 4261 (see here), you can read that the dark, dusty disk represents a cold outer region which extends inwards to an ultra-hot accretion disk with a few hundred million miles from the suspected black hole.
So, from the outside, you have successively a bright ring, then a dark dusty ring and "an ultra-hot accretion disk" very close to the center black hole itself.

My question : due to the ultra-hot temperature in the accretion disk, the dark material (dust) is extremely heated and, so, should radiate in a very bright way (UV and/or X-rays). Why not ?

Regards
JF
 
Astronomy news on Phys.org
Ok, the picture link I posted is taken at visible wavelengths that why dust material is not bright. Am I right ?

Regards
JF
 
Yes. Dust tends to radiate at the frequency of light it receives.
 

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