Questions tagged [galaxy-rotation-curve]

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Could the Many-Worlds-Interpretation influence the Galaxy-Rotation-Curves? [closed]

A Galaxy Rotation Curve shows the orbital speeds of stars vs. the distance from the galactic center. Measured Galaxy Rotatation Curves are curiously flat, meaning the outer stars orbit faster around ...
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1answer
46 views

Is there software to calculate/plot decomposed rotation curves from observational data (FITS, etc)?

I have observation data of galaxies (in FITS format). From the FITS data, I want to calculate & plot the decomposed rotation curves as pictured below. Is there a software package that will do that ...
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2answers
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How much faster are the stars on the outskirts of galaxies going than they are 'meant' to as predicted by general relativity?

this is in reference to dark matter. I've look on the internet for this but I can't find precisely what I am looking for.
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Unruh effect on rotating galaxies?

According to the Unruh effect, an accelerating observer will experience a thermal bath. This is equivalent to Hawking radiation. If we applied this to a spinning galaxy, I wonder if this thermal bath ...
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Keplerian galactic rotation curve

I am trying to plot my obtained galactic rotation curve from Hydrogen line measurements with Keplerian galactic rotation model. However what values should I use for Keplerian galactic rotation model ...
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2answers
44 views

How can I plot Rotation Curves of Spiral Galaxies $v$ (km/s) vs $r$ (kly)?

I have a formula about Rotation Curves of Spiral Galaxies that I have written below: $$v(r)=c [L/(2*r)+1/2\cdot c_3+ c_4\cdot\ln(r)]^{1/2}$$ that $c=3\cdot10^8m/s$ is the speed of light and $c_3=2.8\...
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23 views

Are there galaxies with satellites in retrograde orbit?

If frame dragging is important for properly calculating galactic rotation curves, it seems that galactic satellites in retrograde orbit should behave as if they experience a different amount of ...
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Has frame dragging been accounted for in galactic rotation curves?

This article explicitly takes frame dragging into account in calculating expected galactic rotation curves in the absence of dark matter, and appears to obtain very close matches to observed curves. ...
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1answer
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Is galactic gravitational lensing self-magnification big enough to contribute noticeably to the galaxy rotation curve problem?

Gravitational lenses magnifies the appearance of themselves, so in the case of a galaxy it looks bigger than it is. Thus the outer stars in a galaxy seems to have a higher tangential velocity. For ...
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1answer
49 views

How could I calculate the circumferential velocity of stars in an idealized spherical galaxy from the distribution of mass through that galaxy? [closed]

We will assume that the galaxy is a sphere where stars orbit around the center on different radii. Since there are so many stars, we will not deal with individual stars, but we will assume that the ...
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Does dark matter interact with baryonic matter only through the gravitational field? [duplicate]

Do I understand correctly that dark matter fields are interact with baryonic matter only through the gravitational field? In this case, how can it be registred at all if it does not interact with the ...
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4answers
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Are orbiting masses in a uniform disc affected by masses outside its orbit?

For a sphere of uniform density, we know an orbiting mass experiences a net attraction only by the mass inside its orbit, and that the mass outside its orbit exerts a net zero force (using Newton's ...
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2answers
52 views

How can we know the velocity curve past the cut-off radius of visible matter in a galaxy?

I am trying to understand a typical explanation for the need of a dark matter halo in galaxies. The rotational velocity of stars around the centre of a galaxy seems to be constant past a certain ...
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2answers
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Single galactic proof of Dark matter?

I've heard tell that many galaxies have visible mass profiles which do not match up to a predicted Gravitationally Newtonian velocity distribution. Can anyone here find me an accessible paper of an ...
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3answers
67 views

What's stopping stars in galaxy from traveling at infinite speed?

The dark matter in galaxies causes the starts to orbit with a higher orbital speed. Now, assuming that there is a constant force from the dark matter on the starts, there should be constant ...
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2answers
52 views

How far the galaxy's 'flat part of rotation curve' extends?

I know that the galaxy rotation curve doesn't obey general relativity and instead of decreasing, the star velocity remains constant which is shown by a flat rotation curve (rotation velocity v/s ...
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2answers
115 views

Dynamical mass of a galaxy

What does the dynamical mass of a galaxy represent? Is it the mass of the gas in the galaxy or the total mass of the galaxy? What can we infer from the rotation curves, is it dynamical mass or mass ...
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25 views

What is the gas distribution in galaxies?

I'm fitting a number of galaxy rotation curves, and I need the density distributions of stars, gas, and DM. I know that the baryonic disk densities fall off exponentially (the characteristic radii can ...
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3answers
83 views

If the distribution of dark matter is not uniform, why it is not attracted towards center of galaxies?

The dark matter hypothesis was formed due to difference in theoretical and observed speed of the outer parts of galaxies. Therefore, there is more dark matter in the outer parts of the galaxy than in ...
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1answer
80 views

How do I decompose my overall rotation curve for M31 into a rotation curve for the disk and halo?

How do I decompose my grand rotation curve into rotation curves for the disk and halo, like the image below? The picture is from this link pages.pomona.edu/~tmoore/RotCurve The data points are ...
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1answer
24 views

What methods can I use to determine the total mass of M31 using rotation curve data (galactocentric radius and rotational velocities)?

I've used M(r) = RV^2/G to find the enclosed mass within the orbit of a target body in M31, but I want to use other methods to derive the total mass of the galaxy, including the mass of dark matter ...
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Questions about Dark Matter and Galactic Rotation

First, does the dark matter halo and galactic rotation of a galaxy depend on it's size? So bigger galaxies, bigger dark matter halo. Secondly, is the amount of dark matter for a galaxy universal? So ...
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1answer
46 views

Star distribution (density of stars) as a function of distance from Galaxy centre?

Is there any mathematical formula or empirical relation that defines the density of stars as a function of distance from the Galaxy centre in a spiral galaxy?
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1answer
98 views

Express the total mass of the galaxy in solar masses

I have the following problem: "The Sun has an orbital speed of about 220 km s−1 around the center of the Galaxy, whose distance is 28 000 light years. Estimate the total mass of the Galaxy in ...
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1answer
59 views

Why are galalxies spiral? [duplicate]

In every picture we see that galaxies are spiral, why so? are there any other shapes possible?
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1k views

Why is the distribution of dark matter in a Galaxy different from the distribution of normal matter?

The dynamics of a galaxy are driven by gravity. And dark matter experiences the same gravitational forces as normal matter. The effects of other forces are very small in comparison. So why is the ...
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2answers
153 views

Why physical / cosmological models that have been falsified weren't abandoned? [closed]

Before anything, I'd like to say that I'm a layman (non physicist) and english is not my main language; I apologize if my choice of words make me sound rude / arrogant, that is not my intent. I often ...
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1answer
54 views

Is it possible that black holes generate space? [closed]

Suppose that there is a limit to the strength of a gravitational field. Then, if the mass is added to a black hole, the gravity term in the EFE will not increase, so the spatial expansion term must ...
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0answers
95 views

Gravitational potential energy of an isothermal sphere

I am trying to calculate the gravitational potential energy, W, defined as: $W = -\frac{1}{2}\int\rho(r)\Phi(r)d^{3}r$ for an isothermal sphere. I am given that the density profile varies with r as:...
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1answer
131 views

Why does not dark matter gather and form celestial bodies? [duplicate]

since the only thing we know about dark matter that it "attracts" and affect our Baryonic matter's momentum and speed, which means that it does have mass of a sort. so why didn't we witness a ...
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1answer
57 views

Could dark matter be normal matter that is beyond the observational horizon?

As I understand it, matter that is too distant for its light to reach us would not be observable, and the CMB is the limit of what is observable from our location within the universe. Could what is ...
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1answer
65 views

How do we know the quantity of dark matter in the universe?

I have been reading on dark matter and it is given specific numbers of its quantity, i.e, ~27%, in the universe. How we come up with that number as we have no strong opinion what it is made of? We ...
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1answer
114 views

Effects of dark matter

I was wondering, when sims of galaxies show that we need dark matter to account for the movement of outer stars, are models taking into account relativistic effects on gravity? The tips of spiral ...
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1answer
65 views

Spacetime drag and galaxies' radial velocity mismatch

We know - or theorize - that a spinning black hole drags spacetime in its surroundings, producing measurable effects on the accretion disk (the minimum stable orbit radius). What I cannot grasp is why ...
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2answers
113 views

Mass versus rotation Curves

Is there an equation that describes the relationship between the mass of the Galaxy and rotation curve? I found V versus R graphs and equations that describe their relationship (kind of). But I ...
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1answer
81 views

Can we weight dark matter?

We can observe the effect of light as it gets bended in the presence of dark matter, and I wonder how is it possible to measure their mass given that we can't see them and they don't interact with ...
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1answer
76 views

Do attraction between two galaxies count for dark matter?

We know that the uniform rotation curve of individual spiral galaxies does require presence of some form of dark entity (matter). Does the attraction between two (or more) spiral galaxies also require ...
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Could dark matter consist of the supermassive black holes at the centers of galaxies?

Inspired by this question about whether dark matter is matter, noting that dark matter tends to be clumped in galaxies near the center and less so on the edges, accepting that many (most?) galaxies ...
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2answers
248 views

What's wrong with the Big Spin Model?

A Dr. Serkan Zorba has a paper on arxiv in which he considers, what if the universe is actually slowly rotating? This gives rise to centrifugal and Coriolis forces on a galactic scale that seem to ...
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1answer
91 views

Is the dark matter present only around the galaxies?

Dark matter is believed to give galaxies its shape and prevent them from flying apart. Is dark matter present only on outer edges of the galaxy or is it present throughout the galaxy?
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Population histograms and relationship between size of galactic disk and amount of dark matter

I am interested in seeing a plot of dark to baryonic matter ratios in terms of the galactic disk size (when it applies, as not all galaxies fit into disk shapes, and probably analyzing disk galaxies ...
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1answer
226 views

Galaxy Rotation Speeds and General Relativity

Is it true that the predictions from the General Theory of Relativity don’t match the observations of galaxy rotation speeds, and that this then started the search for dark matter? Is it only the ...
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1answer
73 views

Dark matter or Misunderstanding: Is it possible that the dark matter is simply missed variables in the math?

Is it possible that the dark matter is simply missed variables in the math? I am not a physicist but examples might include: effects of planetary and galaxy rotation, electromagnetic fields, ...
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2answers
135 views

How do we know that galaxies are not losing significant numbers of stars from their outer regions?

A major reason for believing in the existence of dark matter is that the stars in the outer regions of galaxies are moving too fast to remain bound to their galaxies, given only the estimated mass of ...
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1answer
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Can there be forces between three things? [closed]

In all the physics I know forces are always between pairs of things. Gravity is between pairs of masses, so is electrostatic repulsion, so are the strong and weak forces as far as I understand them (...
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1answer
218 views

How Much Do Spiral Arms Affect Their Galaxies' Rotation Curves?

According to Jerry Sellwood of Rutgers University, in the article What process creates and maintains the beautiful spiral arms around spiral galaxies?: Fortunately, nearly every one agrees that ...
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3answers
5k views

How did we 'discover' dark matter? [closed]

I'm an astrophysics student and I've been researching this topic and there is one point that keeps eluding me. How did the scientific community realize that there had to be dark matter in the ...
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1answer
1k views

What is the meaning of 'systemic velocity' of galaxies?

I came across the term systemic velocities of galaxies. Can you please explain what it means?
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1answer
85 views

Estimating total mass inside the Sun's orbit

I'm trying to estimate the local density of dark matter at a given radius, $r=R_0=8\text{kpc}$. I also have values for the core radius, $a=5\text{kpc}$, and circular velocity of the Sun, $v_{\text{...
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How is it possible to have red shift along one axis and blue shift on another in a spiral galaxy arm?

I don't understand this image: If the stars are moving in roughly circular orbits why would red shift occur in the direction of the orbit and how would it be possible to have blue shift in two ...