Are masers orbiting black holes a reliable standard ruler in cosmology?

[lomidrevo]

One of the distance measures in cosmology is angular diameter distance, that can be used to determine a distance to objects whose actual (spatial) size is known, i.e. standard rulers. Beside baryonic acoustic oscillations, do we know other objects (or maybe I should better say structures) that can be used as standard rulers?

 

[timmdeeg]

https://en.wikipedia.org/wiki/Tip_of_the_red-giant_branch

Red giants seem to play a role with regard to investigate the Hubble tension.

 

[lomidrevo]

Ok, but that would be answer to a different question

 

[mathman]

Shorter distances: parallax. Further distance - Cepheid variables. Long distance - IA supernovae.

 

[anorlunda]

It sounds like some of the replies talk about standard candles, but the OP specifically asks only about standard rulers.

 

[PAllen]

I believe the angular diameter distance is primarily a value computed from redshift per a certain model. That is, there are not large distant objects whose size we know, to calibrate an independent angular size distance. Thus, we say, given a cosmological model and observed redshift, if we can detect an angular extent, we can extrapolate a size.

 

[lomidrevo]

Shorter distances: parallax. Further distance - Cepheid variables. Long distance - IA supernovae.

I know the distance ladder, but question is different.

It sounds like some of the replies talk about standard candles, but the OP specifically asks only about standard rulers.

Exactly!

Let me provide a brief context, so maybe it will be clearer for future posters why I ask about standard rulers. I read Carroll's textbook on GR, and in the chapter 8. Cosmology he discuss different distance measures. Obviously the one most widely used is luminosity distance, that is related to standard candles already mentioned by some of you. The other measures are proper motion distance (which I have no idea how that can be used in cosmology, as at large scales everything looks pretty static) and finally the measure angular diameter distance. At the first glance, this measure didn't look to me very practical as at large scales (say hundreds of Mpc) it is quite difficult to imagine standard ruler, i.e. anything of a known size that can be angularly resolved by telescopes. But yet, I managed to google that BAOs are such standard ruler. But nothing else I was able to find, so I wonder whether this is the only case.

 

[lomidrevo]

That is, there are not large distant objects whose size we know, to calibrate an independent angular size distance.

Yes, the BAO already mentioned. (btw. it is fascinating that we can calculate the sound horizons )
From wiki:

The physics of the propagation of the baryon waves in the early universe is fairly simple; as a result cosmologists can predict the size of the sound horizon at the time of recombination. In addition the CMB provides a measurement of this scale to high accuracy.
...
In order to understand the nature of the dark energy, it is important to have a variety of ways of measuring the acceleration. BAO can add to the body of knowledge about this acceleration by comparing observations of the sound horizon today (using clustering of galaxies) to that of the sound horizon at the time of recombination (using the CMB). Thus BAO provides a measuring stick with which to better understand the nature of the acceleration, completely independent from the supernova technique.

So if I got it right, knowing the angular and spatial size of BAO in observed universe, and comparing that with CMB we have independent way to measure expansion of the universe, right?

Thus, we say, given a cosmological model and observed redshift, if we can detect an angular extent, we can extrapolate a size.

Yes that make sense! Is this method sensitive enough, for example to determine diameter of galaxies?

 

[kimbyd]

There are sometimes galaxies with uncommon features that can be used to measure the distance to them geometrically, such as here:
https://arxiv.org/abs/1307.6031

 

[PAllen]

There are sometimes galaxies with uncommon features that can be used to measure the distance to them geometrically, such as here:
https://arxiv.org/abs/1307.6031

Cool!

 

[lomidrevo]

There are sometimes galaxies with uncommon features that can be used to measure the distance to them geometrically, such as here:
https://arxiv.org/abs/1307.6031

I do not follow all the details, but if I understood right, they didn't use angular size of the AGN as an input. The inputs were observed sky position, radial velocities and radial accelerations.

The data used to determine the maser disk geometry and the distance to NGC 4258 consist of maser emission positions (X,Y ), line-of-sight (LOS) velocities (vlos), and LOS accelerations (alos).

To me, it seems that angular diameter measure was not used here, am I correct?

 

[kimbyd]

I do not follow all the details, but if I understood right, they didn't use angular size of the AGN as an input. The inputs were observed sky position, radial velocities and radial accelerations.To me, it seems that angular diameter measure was not used here, am I correct?

The sky positions they're referring to are the maser positions, which are used for the angular measurement using VLBI.

I haven't looked into the physics involved here, but from reading the paper it sounds like the masers orbit the central black hole and they can use the velocity/acceleration information to infer those orbits to some degree of precision. Then by using the VLBI observations they are able to compare the inferred physical size of the orbits to the angular size.