B Galaxy rotational curves vs time

[Daniel Dimov]

Hello to everyone,

I'm trying to find some data about the relation between galaxy age and rotational curve... until now without success.

Are there any teams working on this? Are there any studies in this direction?

Thanks!

 

[Baluncore]

Welcome to PF.

I'm trying to find some data about the relation between galaxy age and rotational curve...

Radio observation of the hydrogen line from galaxies viewed side-on show two peaks due to the rate of rotation of the galaxy. From that the red shift of the galaxy as a whole can also be estimated.

Can you be more specific about what you need? and why you need it?

 

[Daniel Dimov]

The interesting question is: do galaxies evolve to what we see nearby (more apparent mass than we can directly see) or they are like this from the beginning?

 

[TEFLing]

The interesting question is: do galaxies evolve to what we see nearby (more apparent mass than we can directly see) or they are like this from the beginning?

I understand that the current consensus is there is no evidence of any significant evolution in. Rotation. curve profiles or dark matter content. Of spiral galaxies.

 

[phinds]

I understand that the current consensus is there is no evidence of any significant evolution in. Rotation. curve profiles or dark matter content. Of spiral galaxies.

I think your "." key is stuck.

 

[alantheastronomer]

I think your "." key is stuck.

I think he meant to use his comma - "," - key...

 

[phinds]

I think he meant to use his comma - "," - key...

Actually, that wouldn't make any sense either. There is no reason for a "." OR a "," anywhere in that sentence.

Ah. I see he's not a native English speaker. That's probably the heart of the issue. @TEFLing your English Is WAY better than my Thai

 

[ohwilleke]

Hello to everyone,

I'm trying to find some data about the relation between galaxy age and rotational curve... until now without success.

Are there any teams working on this? Are there any studies in this direction?

Thanks!

This is an area of active study. Many teams of astronomers are actively trying to compare the oldest observable galaxies with modern galaxies.

Leading theories of galaxy formation tend to predict that "modern" looking galaxies should only begin to be visible later in time since the Big Bang than they are actually observed. This is called the "Impossible Early Galaxy problem." As explained in the linked article:

The Impossibly Early Galaxy Problem
Charles L. Steinhardt, Peter Capak, Dan Masters, Josh S. Speagle
(Submitted on 3 Jun 2015 (v1), last revised 8 Apr 2016 (this version, v2))
The current hierarchical merging paradigm and ΛCDM predict that the z∼4−8 universe should be a time in which the most massive galaxies are transitioning from their initial halo assembly to the later baryonic evolution seen in star-forming galaxies and quasars. However, no evidence of this transition has been found in many high redshift galaxy surveys including CFHTLS, CANDELS and SPLASH, the first studies to probe the high-mass end at these redshifts. Indeed, if halo mass to stellar mass ratios estimated at lower-redshift continue to z∼6−8, CANDELS and SPLASH report several orders of magnitude more M∼1012−13M⊙ halos than are possible to have formed by those redshifts, implying these massive galaxies formed impossibly early. We consider various systematics in the stellar synthesis models used to estimate physical parameters and possible galaxy formation scenarios in an effort to reconcile observation with theory. Although known uncertainties can greatly reduce the disparity between recent observations and cold dark matter merger simulations, even taking the most conservative view of the observations, there remains considerable tension with current theory.
Comments: 10 pages, ApJ, in press
Subjects: Astrophysics of Galaxies (astro-ph.GA)
DOI: 10.3847/0004-637X/824/1/21
Cite as: arXiv:1506.01377 [astro-ph.GA]
(or arXiv:1506.01377v2 [astro-ph.GA] for this version)

 

[alantheastronomer]

"The Impossibly Early Galaxy Problem" seems to imply that the hierarchical merger model of galaxy formation doesn't work and needs to be abandoned as the process by which galaxies form. Apart from this, there's a practical reason why there are no measurements of rotation curves of galaxies in the early universe; you can only get rotation curves of galaxies which are nearly edge-on to the line of sight of the observer. This means that the galaxies you want to observe have very low surface brightness due to interference from dust lanes. On top of that, as you go to further distances, the angular size of the galaxies get smaller, you have less spatial resolution in order to determine velocity as a function of radius - and that's worse in the radio region. So these selection effects make it impractical to make the observations...It's too bad, because that's a very interesting question!

 

[ohwilleke]

Another example of studies early galaxies, where as @alantheastronomer notes, properties other than rotation curves (such a velocity dispersion) are usually measured:

Implications of the lens redshift distribution of strong lensing systems: cosmological parameters and the global properties of early-type galaxies
Yu-Bo Ma, Shuo Cao, Jia Zhang, Shuaibo Geng, Yuting Liu, Tonghua Liu, Yu Pan
(Submitted on 28 Jan 2019)
In this paper, we assemble a well-defined sample of early-type gravitational lenses extracted from a large collection of 158 systems, and use the redshift distribution of galactic-scale lenses to test the standard cosmological model (ΛCDM) and the modified gravity theory (DGP). Two additional sub-samples are also included to account for possible selection effect introduced by the detectability of lens galaxies. Our results show that independent measurement of the matter density parameter (Ωm) could be expected from such strong lensing statistics. Based on future measurements of strong lensing systems from the forthcoming LSST survey, one can expect Ωm to be estimated at the precision of ΔΩm∼0.006, which provides a better constraint on Ωm than \textit{Planck} 2015 results. Moreover, use the lens redshift test is also used to constrain the characteristic velocity dispersion of the lensing galaxies, which is well consistent with that derived from the optical spectroscopic observations. A parameter fE is adopted to quantify the relation between the lensing-based velocity dispersion and the corresponding stellar value. Finally, the accumulation of detectable galactic lenses from future LSST survey would lead to more stringent fits of ΔfE∼10−3, which encourages us to test the global properties of early-type galaxies at much higher accuracy.
Comments: 12 pages, accepted for publication in The European Physical Journal C
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1901.09737 [astro-ph.CO]
(or arXiv:1901.09737v1 [astro-ph.CO] for this version)