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Questions tagged [galactic-dynamics]

Questions regarding interactions between galaxies or between major parts of a galaxy.

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0 votes
2 answers
168 views

What happens to planets as they cross the Galactic equator?

We know from research that the Solar System travels around the Galactic plane, and sometimes (periodically) dips below the Galactic equator, only to return and dip back above the Galactic equator ...
0 votes
1 answer
74 views

The distribution of mass in the bullet cluster

Can someone point me to a database which contains the luminous and gas mass distribution of the bullet cluster?
1 vote
0 answers
85 views

Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?

Related questions have been raised before Is our central black hole actually at the CG of the galaxy? Orbiting supermassive black hole or galactic center of mass? , where explanations have been given ...
6 votes
1 answer
492 views

Does the Final-Parsec problem apply to stellar collisions?

The final parsec problem describes the difficulty of two blackholes merging with one another when their distances reach ~3.2 light years apart. Does this also then apply to stellar collisions, perhaps ...
4 votes
1 answer
270 views

How do two supermassive black holes reach "the last parsec" in the case of merging galaxies?

This answer to Why can't supermassive black holes merge? (or can they?) describes the barrier to merging that two supermassive black holes face when two galaxies are in the process of merging or have "...
1 vote
0 answers
40 views

How to decide and narrow down the broad topics I should get an astronomy internship on? [closed]

This is to inform that I am a third-year Physics Major student. I am enrolled in a five-year dual degree BS-MS programme at IISER Bhopal, India. I had a keen pop-science-like interest in astronomy ...
0 votes
1 answer
124 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?
1 vote
1 answer
79 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 ...
9 votes
3 answers
2k 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 ...
1 vote
0 answers
31 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 ...
2 votes
1 answer
8k views

In which direction does the Milky Way rotate?

We don't have a photo of our Milky Way the whole, all the pictures are artists' interpretations showing a bulge, a central bar, and several spiral arms. The milky way is spinning. I would like to know:...
4 votes
2 answers
148 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 ...
3 votes
1 answer
170 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 ...
5 votes
2 answers
3k views

What is the direction of the movement of the solar system in relation to the galaxy's plane

I got from this answer that the axis of the solar system is tilted of about 63 degrees in relation to that of our galaxy, so I can assume that we move through space (at least locally) roughly in a ...
1 vote
0 answers
19 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 ...
2 votes
0 answers
32 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 ...
8 votes
1 answer
298 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 ...
1 vote
0 answers
26 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 \...
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 ...
2 votes
0 answers
47 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/...
5 votes
2 answers
102 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 ...
2 votes
1 answer
82 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
272 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 (...
3 votes
0 answers
177 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 ...
3 votes
1 answer
63 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 ...
2 votes
0 answers
57 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 ...
6 votes
0 answers
98 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 votes
2 answers
165 views

How is the potential-density pair relation derived?

How can it be shown that $$\nabla^2\phi = 4\pi G \rho(\vec{r})$$ ?
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
98 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 ...
7 votes
1 answer
816 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 ...
3 votes
1 answer
91 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 ...
1 vote
0 answers
115 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 ...
1 vote
2 answers
128 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?
2 votes
2 answers
202 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 ...
7 votes
2 answers
2k views

Could dark energy be negative gravity?

Main question: Could dark energy (the mysterious accelerating expansion of the universe) be explained by "negative gravity"? "Spin off" questions: Does antimatter have negative gravity? If ...
10 votes
2 answers
2k views

What (actually) is the " deprojected half-light radius" of this almost-all-dark-matter Galaxy?

The recent news of the Ultra Diffuse Galaxy (UDG) Dragonfly 44 is an excellent example of what could be termed 'observe different' thinking. The dragonfly telescope is noted not for the size of its ...
4 votes
0 answers
67 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 ...
2 votes
2 answers
202 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 ...
2 votes
1 answer
82 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 ...
2 votes
1 answer
76 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 ...
6 votes
0 answers
45 views

Are metallicities of molecular clouds lower in the outskirts of the galaxy?

(this question was originally posted in an answer by user PSR-1937-21 to another post. I find it an interesting one, but since they don't seem to be active anymore, I'm posting it to see if somebody ...
2 votes
2 answers
526 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 ...
4 votes
1 answer
316 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 ...
4 votes
0 answers
92 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. ...
1 vote
0 answers
46 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 ...
2 votes
1 answer
85 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?...
3 votes
1 answer
108 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. ...
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
113 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 ...