Questions tagged [galactic-dynamics]
Questions regarding interactions between galaxies or between major parts of a galaxy.
117
questions
0
votes
1
answer
118
views
Have gas or dust or rock accumulated in our solar system on its 20 orbits around the Milky Way?
Also,does the absence of the accumulation of anything large such as rogue planets by the solar system suggest the Milky Way has been orderly and stable for billions of years?
user52681
1
vote
1
answer
73
views
Gas mass and velocity in galaxy
I was going through the SPARC data on galaxies (http://astroweb.cwru.edu/SPARC/)
The velocity of gas in the SPARC data is in http://astroweb.cwru.edu/SPARC/MassModels_Lelli2016c.mrt
The gas velocity ...
- 201
9
votes
3
answers
1k
views
Are there some (simple) mathematical models which can simulate the cellular/web structure of the universe?
To visualize the structure of a solar system we have some simple mathematical model: Planets orbiting around a Star in circular motion.
If we want to be more precise the circle becomes a ellipse, the ...
- 245
1
vote
0
answers
24
views
At what distance does the galactic tide significantly affect the orbit of a heliocentric object?
The title essentially explains the question. I was wondering if the galactic tide could play a role in raising perihelia of extreme trans-Neptunian objects (i.e. Sedna) versus the effect of a ...
- 6,613
3
votes
1
answer
133
views
Why is the dark matter component of MOND important in central regions?
A lot of papers say that even the theory of MOND requires the existence of dark matter, particularly in the central regions. However this is a bit counterintuitive to me considering that rotation ...
- 779
1
vote
0
answers
14
views
How to obtain the SDSS’s five-part imaging ID number for a list of galaxies whose Ra Dec is known?
I am trying to obtain the FITS file of a few hundreds galaxy from SDSS DR12 Survey. SDSS tries to download the FITS File with the link that contains the information about SDSS’s five-part imaging ID ...
- 11
4
votes
2
answers
140
views
Can the collapse of a gas cloud lead to an elliptical structure?
Is it likely, unlikely, or impossible for an elliptical structure to form when a gas cloud collapses?
Due to the conservation of angular momentum, one would expect that disk structures are much more ...
- 829
2
votes
0
answers
28
views
dark matter in galaxy cluster in intergalactic space
On the rotation speed of galaxies in a galaxy cluster:
-> Is the dark matter associated with each galaxy in a cluster, sufficient to explain the rotation speed of galaxies in the cluster, or extra ...
- 201
8
votes
1
answer
242
views
Have we discovered a Galaxy lacking in Dark matter?
This question is relevant but it was speaking about a specific discovery reported by pieter van Dokkum, and the answer then mentioned it was disputed whether the paper's conclusion is even correct.
I ...
- 231
0
votes
0
answers
49
views
Galactic rotation curves data samples: how to get them?
I am aiming to introduce data Science to my High-School students and I thought about giving to them data taken from galactic rotation curves (spiral galaxies at the moment) to stude the flatness of ...
- 399
1
vote
0
answers
22
views
Why use this density function to derive the Lane-Emden equation?
I am currently reading Binney and Tremaines Galactic Dynamics, learning about spherical systems. In chapter 4.33 a density function (Eq. 4.83) is given as:
$$ f(\mathcal{E}) = \begin{cases} F \...
- 111
17
votes
2
answers
4k
views
Where was the solar system born? Alternatively, how far back in time can we retrodict the location of the solar system?
I have two related questions:
Where in the Milky Way did the solar system form? Is there a particular nebula it can be traced to?
How far back in time can we track the location of the solar system ...
- 283
2
votes
0
answers
45
views
Formation scenarios for elliptical galaxies?
I am trying to get an overview of the latest research on different formation scenarios for elliptical galaxies and filter out old scenarios in the literature that are today proved to be not sufficient/...
- 829
5
votes
2
answers
96
views
What is meant by " elliptical galaxies stabilize due to the chaotic motion of stars"?
I read that elliptical galaxies stabilize due to the chaotic motion of stars. As I understand that means that the stellar motions are more nearly random in direction. So they perform independent ...
- 829
2
votes
1
answer
80
views
Why do stars orbit much faster than gas in galaxies?
The velocity dispersion of gas within galaxies is typically 30-40 km/s. Stars are born in gas clouds. But later on, their orbital velocities reach several hundreds of km/s. How is this possible? Where ...
2
votes
1
answer
199
views
3d distance between the Galaxies inside the galaxy cluster
I am currently working on the dynamics of the galaxy cluster, so i am trying to get the distance between the galaxies inside the galaxy cluster from its centre. As a input i have RA , DEC and Z (...
- 41
3
votes
0
answers
163
views
How do star orbits, density wave theory and dark matter distribution work together?
I got confused while trying to combine these 3 concepts. Would love to hear some detailed explanation.
Density wave theory states that spiral arms are formed by tilted elliptic orbits. Bertrand's ...
- 31
3
votes
1
answer
62
views
Can the Hubble expansion inject energy in AGN and quasar outflows?
I found this article about the behavior of quasar outflows in cosmology and how they can create a magnetic field.
In section 2.1.4., the authors say that when a quasar produces a "wave" or ...
- 767
2
votes
0
answers
54
views
You find yourself on a random planet in the milky way 2000 years in the future. Can you figure out where/when you are? [duplicate]
Imagine you're on a planet in a distant part of the milky way, 2000 years from now. You don't know where you are or how much time has passed. You have access to modern astronomical data and technology ...
- 31
6
votes
0
answers
92
views
How many galaxies are currently merging?
On the homepage of the galaxies research group at CfA SAO, it states, "Astronomers discovered that as many as 25% of galaxies are currently merging with others." They do not provide a ...
- 4,439
4
votes
2
answers
152
views
How is the potential-density pair relation derived?
How can it be shown that $$\nabla^2\phi = 4\pi G \rho(\vec{r})$$ ?
- 171
13
votes
2
answers
3k
views
Is Dark Matter possible if there is dynamical friction?
If dark matter existed: wouldn't it slow down the orbital velocity of stars in galactic disks by dynamical friction more than it would accelerate them through additional mass? The original orbital ...
2
votes
1
answer
77
views
Need help in writing a query using ADQL (Astronomical Data Query Language)
I am trying to query Gaia archive to get the medium quality sample as mentioned in Reico-Blanco et al. (2022) Gaia Data Release 3: Chemical cartography of the Milky Way. The idea is to query the ...
- 153
7
votes
1
answer
764
views
Why wouldn't an elliptical galaxy collapse back into a spiral galaxy?
I should preface this post with two parts of my tentative (probably wrong) understanding first.
First, it's been told to me that spiral galaxies typically form first, and then elliptical galaxies ...
- 265
1
vote
0
answers
91
views
Can this ppxf fit work?
I am trying to do kinematical analysis of spectra using ppxf-algorithm from Capellari. The velocity dispersion I get seems to be to high and I am not sure what the reason could be. On the website of ...
- 829
3
votes
1
answer
76
views
Evaluating Potentials using Galpy
I am trying to model galactic disks. From the past research we have discovered that the halo follows the logarithmic potential, the disk follows the Miyamoto-Nagai potential and the bulge follows the ...
- 153
1
vote
2
answers
121
views
Could primordial black holes explain the SMBH in the galactic centers?
If there were enough primordial black holes (with the right mass) they could explain dark matter. Could they explain the gargantuan monster holes in the center of galaxies?
- 1
2
votes
2
answers
156
views
What object(s) are furthest above/below the galactic plane?
This is kind of a spin-off of a question I did about a space telescope surveying the galaxy from above the galactic plane. So, it made me wonder, which object in the Milky Way has been spotted ...
- 714
4
votes
0
answers
58
views
What's the angle between the sun's galactic speed and the ecliptic?
I know the sun wobbles up and down the galactic plane around 35myr. I don't mind about that component.
I'd like the know the angle between the linear speed of sun around the Milky Way (just the ...
- 141
2
votes
2
answers
183
views
At what distance does MOND Modified Newtonian Dynamics take effect?
At what distance does MOND Modified Newtonian Dynamics take effect? I understand MOND is described in relation to very slow accelerations, which is related to distance. It is mentioned it has an ...
- 442
2
votes
1
answer
78
views
Is our Milky Way galaxy (and its neighbors?) moving through the universe at 370 km/s (~828,000 mph) or 370 miles/sec (~1,332,000 mph)? [duplicate]
I swear that exactly half of the many, many sites I found say that our Galaxy and its immediate neighbors are moving towards the Leo Constellation (I believe) and, ultimately, supposedly, the 'Great ...
- 4,891
2
votes
1
answer
70
views
Why are Galaxy doppler Light Curves rising from the center of the Galaxy? Stars near the center of a Galaxy are moving faster than those near edge
Why are Galaxy Doppler Light Curves rising from a low point near the center of the Galaxy? Stars near the center of a Galaxy are moving faster than those near the edge. I understand that we probably ...
- 21
1
vote
2
answers
392
views
How do bars form in barred spiral galaxies?
I am aware this duplicate question exists, but its only answer is unfortunately a rather unsatisfying quote which I could not even find within the provided link. Also, that question is from 2017 so ...
- 121
4
votes
1
answer
260
views
What are typical peculiar velocities?
I'm wondering what sorts actual values we can expect to find for peculiar velocities of individual objects when observing the universe, both typically and on the high end. I'm interested in any ...
- 142
1
vote
0
answers
41
views
Is the Condor Galaxy (NGC 6872) the result of a non-collision galaxy interaction?
All the interacting galaxies that I can find are of collisions, I'm trying to find an example of a fly-by galaxy interaction. Is the Condor Galaxy an example of one?
Wikipedia's NGC 6872; Possible ...
- 1,301
4
votes
0
answers
89
views
Why do the Centaurus A radio jets have two "arms" each? (Event Horizon Telescope image)
Fig. 2: Image analysis of the final model: a, Model image corresponding to the image from Fig. 1 with a pixel size of 2 μas. Here, the tentative position of the jet apex is indicated with a circle. ...
- 31.3k
3
votes
2
answers
2k
views
How can the (in my eyes quite ridiculous) conjecture of Sheldrake be disproven? [closed]
In this question on the physics site, it is asked if astronomical objects can be conscious. Now, in a sense, every object has to be "conscious" somehow, as every object is composed of the ...
1
vote
0
answers
85
views
Why we can approximate the mass of spiral galaxy like this?
This is a question from Galaxies in the Universe: An Introduction(2nd edition),Linda S.Sparke&John S. Gallagher III. As shown in the picture
My question is why we can neglect the bulge of spiral ...
- 41
1
vote
0
answers
30
views
What new instruments "so sensitive that we can see (large circumgalactic winds) have only been on telescopes for a few years"?
The Rhodes College press release Prof. David Rupke and Team of Astrophysicists Make Major New Discovery About Galaxy Evolution links to
Astronomy Community/Nature.com: The Making of Makani; The story ...
- 31.3k
10
votes
3
answers
2k
views
How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes?
I just stumbled across the following answer "update" from 2013:
This just in, recent observations have ruled out the possibility that SMBHs gain mass only through merging with other black ...
- 31.3k
5
votes
0
answers
82
views
Did the density wave theory for spiral arms take account of this phenomenon?
I came across this link. In it the author speculates that in the outer region of a galaxy, the spiral arms overtake the stars, and vice versa for the inner region. That means there must be a middle ...
- 403
2
votes
1
answer
81
views
In 'Modified gravity' theories like MOND, are galaxies and stars actually, slowly accelerating? In the normal sense?
In the Modified Theory of Newtonian Gravity or MOND, they say that massive objects, accelerating slowly, experience this modified gravity.
But are they actually gaining in velocity, albeit very slowly?...
- 4,891
4
votes
1
answer
120
views
Deriving the first moment of Collisionless Boltzmann Equation in Spherical Polar Coordinates
I am following these notes: Dynamics and Astrophysics of Galaxies.
After equation 6.37, we have:
\begin{equation*}
p_r\,\frac{\partial f}{\partial r} + \frac{p_\theta}{r^2}\,\frac{\partial f}{\...
- 481
1
vote
1
answer
393
views
Do the stars in irregular galaxies orbit anything?
Do the stars of irregular galaxies (such as the Magellanic clouds) orbit a more precise point or are they just, I don't know, flying around? If they orbit, how stable would such orbits be, considering ...
- 263
2
votes
1
answer
1k
views
Will the Sagittarius A* Black Hole eventually swallow the entire Galaxy?
In one of his interviews, Sir Roger Penrose mentioned that when the Milky Way and the Andromeda galaxies eventually "collide" and merge into one, their super-massive black holes will also ...
- 235
2
votes
1
answer
97
views
Does this black hole mass/galaxy stellar mass relation hold for extremely low-mass galaxies?
I read a preprint last week (Palmese & Conselice 2020) that suggested that the recent gravitational wave detection GW190521 could be the end result of a merger of two extremely low-mass galaxies. ...
- 36k
2
votes
1
answer
151
views
Figure out the location of celestial objects relative to the Milky Way in x, y, z co-ordinates
I am trying to place various celestial objects the correct distance from the Milky Way, using x, y, z co-ordinates.
So assuming the centre-of-mass of the Milky Way is at 0, 0, 0 - how can I figure out ...
- 21
4
votes
1
answer
444
views
What does "unremarkable transverse peculiar velocity" mean exactly, and how is it calculated here?
The abstract of A magnetar parallax (also in MNRAS) contains the following:
Combining our new observations with two archival observations from 2006, we have refined the proper motion and reference ...
- 31.3k
0
votes
2
answers
148
views
Why is SPT0418-47 ("the most distant Milky Way look-alike") expected to evolve into an elliptical galaxy?
Phys.org's ALMA sees most distant Milky Way look-alike describes the image reconstruction of a strongly and very nicely lensed z = 4.2 galaxy by a by a foreground galaxy at z = 0.263 and says:
"...
- 31.3k
0
votes
1
answer
141
views
How do they know the newly-spotted gas near the center of our galaxy is molecular without knowing what gas it is?
Phys.org's Mystery gas discovered near center of Milky Way links to Teodoro et al 2020 in Nature Cold gas in the Milky Way’s nuclear wind who's abstract is shown below.
Question: My reading of the ...
- 31.3k