Galaxies are much bigger than we thought, study reveals

[DanMP]

I read this article stating that 

Quote

galaxies are far bigger than originally thought, perhaps several times bigger.

I have access to the original article but I didn't understand how they measured everything and if this new finding would reduce the need of dark matter.

Searching "dark matter" in the article I found:

Quote

The vast reservoir of diffuse gas surrounding galaxies known as the circumgalactic medium (CGM) contains ~70% of all mass that is not dark matter1,2,3,4. The CGM was discovered, and is almost exclusively studied, using quasar absorption line probes of galaxy outskirts. [...] Here we observe a single galaxy and its inner CGM to ~0.3 virial radii (Rvir) with kiloparsec-scale-resolution integral field spectroscopy of [O ii], Hβ and [O iii] optical emission lines, which traces cool 104 K gas. By directly imaging the CGM, we obtain the equivalent of thousands of quasar sightlines around a single galaxy. This controls for galaxy-to-galaxy variations that introduce scatter in the CGM properties inferred with quasar absorption lines.

 

[Mordred]

Typically and assuming the old boundary condition still holds but the boundary used to be considered as 100 times the mean average density of the void regions which can be calculated via the critical density formula as our universe is extremely close to critical density.

No this paper will not replace the need for DM though may reduce the local to galaxy quantity needed to match rotation curves.

[DanMP]

22 hours ago, Mordred said:

Typically and assuming the old boundary condition still holds but the boundary used to be considered as 100 times the mean average density of the void regions which can be calculated via the critical density formula as our universe is extremely close to critical density.

I still don't understand how the density of baryonic matter between galaxies can be inferred or accurately measured. They wrote about quasar absorption lines and integral field spectroscopy of [O ii], Hβ and [O iii] optical emission lines, but I don't know how accurate those methods are. At the second (and last) instance where "dark matter" was found in the article, they wrote:

Quote

The ubiquitous emission around IRAS08 implies a large cool CGM gas mass. A key property required to estimate this mass is the electron density, n_e. Quasar absorption line probes of the cool CGM4 and independent estimates from fast radio bursts28 estimate a low value of n_e ≈ 10⁻³ cm⁻³. For our observations, only the central galaxy KCWI pointing had a spectral resolution that was sufficient to resolve the [O ii] doublet, where the line ratio can be used to measure n_e. At the edge of this pointing (r = 7 kpc) the [O ii] line ratio is below the low-density limit29, indicating that n_e < 30 cm⁻³. We therefore could not make a direct estimate of the mass, but we could use our Hβ luminosity profile fit and mass estimates from quasar absorption lines to place constraints on n_e of the cool emitting CGM. To estimate a gas mass, we assumed spherical symmetry in all gas properties and that the Hβ SB power law from Fig. 2 holds between r_break and R_vir (the rough outer boundary of the CGM). A constant n_e = 10⁻³ cm⁻³ and unity volume filling factor gave a total ionized gas mass three orders of magnitude larger than the estimated cool CGM mass for galaxies roughly at the break in the galaxy luminosity function, L*, from absorption line estimates1,4,30 and, more importantly, larger even than the dark matter halo mass of IRAS08. When we instead assumed n_e ≈ 0.3 cm⁻³, we inferred a total ionized gas mass of M_Rvir ≈ 10¹¹ M⊙, which is similar to the absorption line estimate. The clumpiness (or volume filling factor) of the gas will further complicate this. If the clumpiness is high, then this allows even larger n_e for the emitting gas. Overall, our observations—combined with the absorption and fast radio burst results—suggest a wide range of densities in the CGM, which was also seen in recent simulations31,32.

(I don't know if it's ok to quote so much text from the article. If it's not, please delete or reduce it.)

 

I wonder how this extragalactic/circumgalactic mass/medium is influencing the luminosity we measure in order to establish distances and if this influence is or is not important for the Hubble tension ...

Edited September 12 by DanMP

[Mordred]

Well for starters there is a mass/luminosity relation this typically involves processes such as Compton scatterings etc. When I get a chance I will provide further detail on that.

It's doubtful it will affect the Hubble contention as a large part of the contention is due to local calibration issues which involves supernova and different types of cepheids rather than the galaxy itself.

We don't use luminosity of the galaxy for luminosity to distance relations as there is too many unknowns involved for determining the emitter luminosity frequencies.

[J.C.MacSwell]

So if correct they have significantly more mass. Do they have more volume also? Proportionately or disproportionately?

[Mordred]

The mass would be larger and the volume would also increase the photoionization process used by the paper is as follows

\[H_I+\gamma\rightarrow p+e\]

the cross section for the photoionization rate

\[\Gamma_\gamma H=\int_{\nu_t}^\infty c\sigma_\pi (\nu)N_\gamma(\nu)d\nu\]

where \(\nu_t\) is the threshold frequency of 13.6 ev. \(N_y(\nu)d\nu\) is the number density of photons with range \(\nu\rightarrow \nu+d\nu\) this is related to the energy flux \(J(\nu)\) by

\[N_\gamma(\nu)=\frac{4\pi J(\nu)}{ch\nu}\]

in essence the bound free transition probability thoug one can also apply the Milne relation (more specifically for recombination =ionization)

https://casper.astro.berkeley.edu/astrobaki/index.php/Milne_Relation

that is the essential process they are measuring to get the luminosity factors under spectrography

edit forgot to add the reason why the paper posted by the OP highlights the uncertainty in the electron density directly relates to the the above relation. So research tightening the error margin will also be helpful in regards to the Hubble contention. Its further data to help with local group calibrations in regards to distance measures. Specifically the interference to standard candle Lumosity distance relations (simplified descriptive light pollution generated by galactic mediums such as plasma )

 The above relations can be found in 

RADIATIVE PROCESSES
IN ASTROPHYSICS
GEORGE B. RYBICKI
ALAN P. LIGHTMAN

chapter 10.

in terms of H1 vs H11 these describe plasma ionization regions with H1 being partially ionized whilst the H11 region is almost entirely ionized

further details related being the Lyman break

https://en.wikipedia.org/wiki/Lyman-break_galaxy

 

Edited September 13 by Mordred

[Mordred]

Here is detail on the H11 region 

https://en.wikipedia.org/wiki/Strömgren_sphere

though the OP paper is examining H1 region. The link only mentions around a star but it also applies to galaxies in terms of its ionization regions example being the OP paper figure 2

Edited September 13 by Mordred

[DanMP]

19 hours ago, Mordred said:

It's doubtful it will affect the Hubble contention as a large part of the contention is due to local calibration issues which involves supernova and different types of cepheids rather than the galaxy itself.

We don't use luminosity of the galaxy for luminosity to distance relations as there is too many unknowns involved for determining the emitter luminosity frequencies.

Ok, but supernova and cepheids are in some galaxy, so you have to take into account all the matter between them and you when you measure their luminosity. This "new" circumgalactic matter may have some influence (scatter, absorb and/or emit light). Also, the distant/early galaxies may have even more circumgalactic matter then the closer/old ones, because in time this matter can be "absorbed" by the galaxy.

 

11 hours ago, Mordred said:

Here is detail on the H11 region 

https://en.wikipedia.org/wiki/Strömgren_sphere

Very interesting/helpful, thank you.

[Mordred]

Correct you always need to filter out unwanted noise pollution generated by other sources such as stars and plasma

[Simplicity]

If time and space is relative then the expansion of space and how we perceive it is to. So there for when looking at a distant galaxy the expansion of space between all things could be happening at a faster or slower rate there for also changing our perspective of how gravity would behave in that said Galaxy and there for could account for what we believe to be dark matter but really is just the expansion of space and time between all particles at a different rate then our own

[Mordred]

34 minutes ago, Simplicity said:

If time and space is relative then the expansion of space and how we perceive it is to. So there for when looking at a distant galaxy the expansion of space between all things could be happening at a faster or slower rate there for also changing our perspective of how gravity would behave in that said Galaxy and there for could account for what we believe to be dark matter but really is just the expansion of space and time between all particles at a different rate then our own

Unfortunately incorrect but also off topic for this thread which doesn't involve expansion.

For starters expansion is due to thermodynamics described by the equations of state 

https://en.m.wikipedia.org/wiki/Equation_of_state_(cosmology)

These factors determine the expansion rate. 

GR though involved cannot account for all the factors in expansion as per above.

As your new to the forum it is also a rules violation to post personal theories in reply to other posters threads. Any personal theories belong in our Speculation forum.

Edited Friday at 11:14 PM by Mordred