All Questions
128
questions
0
votes
1
answer
26
views
What is emission line ratio?
As the header stated, what exactly is the 'emission line ratio'? Like, [O III]/Hβ or [Ne V]/[Ne II]. Recently I've been reading some research papers in astronomy and astrophysics pertaining to ...
1
vote
0
answers
28
views
Galaxy harassment; flyby encounter (tidal interaction)
This following image is from the paper https://adsabs.harvard.edu/pdf/1978AJ.....83..219R#page=4
It shows the path of a flyby encounter of NGC 3627 (M66) with the galaxy NGC 3628 (the Hamburger galaxy)...
- 11
0
votes
0
answers
35
views
Can dark matter be isolated from baryonic matter?
The above is an image to test Verlinde's emergent gravity theory (2016, https://arxiv.org/abs/1611.02269). The research team observered galaxies and masses beyond, used gravitational lensing (y-axis) ...
- 117
1
vote
1
answer
34
views
Seyfert Galaxies: How does this statistical deduction about the age of their nucleus make sense?
As per this book, An Introduction to Active Galactic Nuclei by Bradley Peterson:
The nuclear emission must last more than $10^8$ years, because Seyfert galaxies constitute about 1 in 100 spiral ...
- 11
3
votes
1
answer
106
views
What happens to objects along spiral galaxy arms over long periods of time?
Observations of spiral galaxies reveal that objects within the same arm of a spiral galaxy move at around the same speeds, regardless of their distance from the center of the galaxy. Conversely, the ...
1
vote
1
answer
194
views
Do all galaxies in our observable universe have more or less the same age?
What is the current consensus about the age variation of the existing galaxies in our observable universe?
Not to be confused with the age of very distant galaxies as observed today by our telescopes ...
- 4,170
2
votes
1
answer
76
views
How much greater is the average distance between stars in the spaces between spiral arms? How much lower is it in them?
I've read about the overall average distance between stars in the milky way, and I've read that one of the best explanations for spirals arms is that they are density waves - that is, they are indeed ...
- 113
0
votes
0
answers
101
views
Galaxy S4G database: convert pixel to kpc
I am referring to S4G database (https://irsa.ipac.caltech.edu/data/SPITZER/S4G/overview.html ).
The information on the length of galaxies, and various length parameters are given in terms of pixels.
...
- 1,023
-1
votes
1
answer
66
views
Is dark matter present in all galaxies?
The rotation speeds of nearby galaxies like M31 or our own milky way are determined by observations. And we know there that luminous mass does not explain the rotation curve. Are there any galaxies ...
- 1,023
2
votes
0
answers
35
views
Dwarf galaxy rotation speed around Andromeda/Mily way
We know that the rotation speed of stars around the center of a galaxy is roughly flat.
But how fast does the dwarf galaxy rotate around the bigger galaxy, say andromeda or milky way?
Do they also ...
- 1,023
2
votes
0
answers
81
views
Keck versus Webb: discrepancies in the redshift measurements of the galaxy GN-z11 (the most distant galaxy discovered with the Hubble Space Telescope)
Two years ago Nature Astronomy published a paper based on measurements from the Keck Telescope stating that the redshift of the galaxy GN-z11 (discovered by Hubble) is:
$$ z=10.957 \pm 0.001 $$
Source:...
- 507
1
vote
0
answers
28
views
Identifying the Milky Way uniquely [closed]
Let’s suppose you wanted to elegantly represent the Milky Way in a minimalist fashion in a way that would make sense a billion years hence (ie let’s set aside the damage wrought by colliding with ...
- 111
1
vote
0
answers
56
views
Database for galaxy luminosity (or mass) distribution
I'm trying to get data on luminosity (or mass) distribution for galaxies.
I came across one paper (https://arxiv.org/abs/1106.3564) which gives luminosity distribution for Andromeda.
But is there any ...
- 1,023
2
votes
2
answers
214
views
Has MOND been tested or even confirmed for our own galaxy, the Milky Way?
MOND, based on a modifications of Newton's law for small accelerations, describes the rotation curves of stars in most galaxies, especially the outer stars.
Has MOND been tested for the stars in our ...
- 727
5
votes
1
answer
102
views
Thermodynamic ensemble of Stars instead of molecules
If we take an enormous amount of molecules (an ensemble), the laws of statistical thermodynamics become valid: we can use them to make predictions of the macroscopic behavior of the ensemble.
I was ...
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