Questions tagged [galaxy]

Questions regarding systems of large numbers of stars held together by gravity.

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43 views

Is there a tool to convert N-body RAMSES simulation file formats to GADGET 2 format in Python?

I am looking for a way to convert RAMSES files to GADGET-2 binary files because I want to use the package SimSpin (https://github.com/kateharborne/SimSpin/blob/master/R/make_simspin_file.R) which is ...
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Databases for galaxy luminosity profiles and velocity rotation curves

I'm looking for databases of the following for a variety of different galaxies, but have so far struggled to find anything. Any help hugely appreciated. Firstly, I'm looking for observations which ...
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what is the difference between Composite Stellar Population and Galaxy Spectral Energy Distribution?

I am reading Conroy et al. (2013), an extensive review on Stellar Population Synthesis technique, and I really can't get the difference between Composite Stellar Population and Spectral Energy ...
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40 views

Approximately what fraction of the galaxy's stars are in the bulge? [closed]

In the text of the question it is said to consider density uniformly
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1answer
105 views

What is that stuff around Andromeda Galaxy

I know Andromeda Galaxy is one of the closest galaxies to our Milky Way, but there are photographs showing it to be surrounded by smaller bodies. Are there any that are closer, or are they all farther ...
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1answer
143 views

What are some astrophotography editing options and strategies for taking photos of galaxies with a telescope and a cell phone?

We purchased a phone adapter for my sons telescope and got some amazing pictures, BUT we believe that they can be clearer. What is the best, or a really good, image editing program for amateur ...
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1answer
69 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 ...
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1answer
46 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 ...
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Measuring the mass of the luminous matter in a galaxy

The mass of total matter in a galaxy can be measured using the rotation curve of the galaxy. However, how do people determine the mass of luminous matter in the galaxy, as a function of the distance ...
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how would you explain the motions in the solar system? [closed]

like so i don't get it it does not make sense I'm confused
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3answers
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Does dark energy make galaxies expand over long periods of time?

Does dark energy expand galaxies slightly over time? I would think this could be verified easily (observe if galaxies far away / further in the past smaller and denser), and might make a good ...
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1answer
143 views

Is a black hole found in the centre of the low-surface-brightness and dark-matter-free galaxy AGC 114905

Per information found on Internet: AGC 114905 was discovered while observing the constellation Pisces with the VLA ground-based radio telescope. The galaxy is about 250 million light-years distant ...
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Stellar and gaseous surface mass density spiral galaxies

I have a database with more than 1000 rotation curves of spiral and lenticular galaxies (xxx-gxx notation is ESOxxx-G0xx). I am working on dark matter mass modeling and I would like to know whether ...
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Is the number of galaxies in the observable universe increasing? [duplicate]

Is the number of galaxies in the observable universe increasing? Are more and more galaxies coming into view? Or is the number decreasing? If it's increasing then when will it reach a maximum? If it's ...
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1answer
31 views

How to find magnitude of one galaxy being a hypothetical observer in the other?

The given apparent magnitude of M31 galaxy is 3.4$^m$, M33 - 5.7$^m$. I wonder how can I calculate the apparent magnitude of one of them (ex. M33) if I imagine myself being in the other (ex. M31)?
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125 views

How to interpret skewness and kurtosis plots of galaxy snapshots?

What I did:- I am analysing some simulation snapshots of the Milky Way and it is modelled as a dark matter halo – bulge – disc system. I produced some skewness (using ...
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1answer
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Calculate the diameter of a galaxy

With reference to this Diameter of any galaxy question. I need some help to calculate an estimate for NGC 1792. I need to calculate a few galaxy diameters so looking for help on one to then work out ...
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1answer
88 views

Can you calculate the radius of a galaxy from Angular Size?

Is there a formula for calculating the size of a galaxy or even a nebula if you have the Angular Size. For example, M31 has an angular size of 199.53 70.79 35 (Opt) D M31 should be 200,000 light ...
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2answers
101 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 ...
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1answer
952 views

Why can't 'dead' galaxies start forming stars again if they merge with another, 'active' galaxy?

I heard Matthew O'Dowd mention on PBS Space-Time that dead galaxies cannot start re-forming stars even if they collect gas and/or dust from elsewhere, or even merge with another galaxy.... Why? And ...
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How to calculate S/N in galaxy absorption spectra?

I want to calculate the S/N of an galaxy absorption spectrum. I therefore chose a part of the spectrum which contains very little to none absorption features and should be only made up of noise and ...
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How to find x-values of fourier-transformed correlation functions in velocity space?

I am trying to extract the kinematic parameters (rotation velocity, velocity dispersion, ...) of an elliptical galaxy by extracting the kinematical broadening function using the FCQ-Algortihm first ...
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1answer
216 views

How many stars are in the Milky Way galaxy?

So, I've always heard that the Milky Way hosts between 100 billion to 400 billion stars. My problem is very simple: I'm unable to find any research papers on that topic or giving those estimates. I'm ...
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1answer
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If all objects move, where do we go?

Yes I know that the sun and planets in the solar system travel fast with an average speed of 448,000 mph. Are we going to the center of the galaxy? If so, does that mean our galaxy is getting smaller ...
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Milky Way vs Milky Way Galaxy

I saw this question on Quizlet which said: What is the difference between the Milky Way and the Milky Way Galaxy? And the answer was: The Milky Way is a fairly narrow band of faint diffuse light ...
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How to remove redshift from galaxy spectra in Python?

Hello I extracted a spectrum from the central region of the 2D spectrum of the major axis from NGC 4697 (I just took a central row in the 2D data set, see this question for more information: How to ...
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1answer
40 views

How to calculate an infrared SED from the specific intensities?

I have values of total infrared fluxes (SED) in literature expressed in Jy (Jansky) for galaxies. I want to assure that my infrared radial profiles of the same galaxies in MJy/sr (and other in Jy/...
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1answer
61 views

Universe is a cluster of orbiting Galaxies?

Like planets orbiting stars, solar systems and other celestial objects orbiting a blackhole in the center of a galaxy, are the Galaxies and Galaxy clusters orbiting the centre of a universe (for ...
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1answer
64 views

E(B-V) , the color excess between B and V bands, for galaxy at redshift 0

Following Mo et al. 2010 (page 479), the quantity $E(B-V)$, called the color excess between B and V bands, is equal to: $$E(B-V) = A_B - A_V = (B - V) - (B - V)_0 = (m_B - m_V) - (M_B- M_V)$$ where $...
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Are there python packages to calculate mean line of sight velocity, linewidth and other distributions from galaxy simulation snapshots?

Does anyone know of any packages/functions in packages that can give mean line of sight velocities (losv) from a simulation snapshot (from the spatial and velocity coordinates or directly from the ...
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1answer
121 views

How to calculate mean line of sight velocity of stars after rotation of galaxy?

I am trying to calculate the mean line of sight velocity from a simulation snapshot of a galaxy after the galaxy is inclined by a certain angle, theta. I am coding it in python. What I have done so ...
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2answers
247 views

Why do other galaxies have such a low surface brightness?

Why do we need to take exposure photos of other galaxies, considering their stars should have roughly the same luminosity per square degree as the ones in the milky way? I'm not saying it should be ...
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How would it possible to Andromeda collide with Milky way? [duplicate]

If galaxies are moving away from each other how is it possible to Andromeda collide with Milky Way?
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396 views

Using masers to measure rotational velocity of a galaxy

When measuring the rotation velocity of a galaxy, most of the times we can only directly measure radial velocity, by looking at the redshift. I read in a lecture slide that some times it is possible ...
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2answers
45 views

How can I find more information on a certain galaxy when NED isn't helping?

The paper High Frequency Peakers: Young radio sources or flaring blazars? by S.Tinti et.al. lists some nice radio-wavelength SEDs, like these for instance: When looking for more photometric info on a ...
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starting from SSP spectra to evaluate galaxy spectrum and observed mag

I know that the galaxy spectrum, namely the flux per unit wavelength versus the wavelength, is the sum of the Simple Stellar Population (SSP) spectra at a fixed redshift (e.g. similar to eq. 1 in ...
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1answer
624 views

Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky Way?

It is thought that the number of satellite dwarf galaxies orbiting around Milky Way is counted in hundreds. Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky ...
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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 ...
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1answer
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The Sun's motion around the galaxy [duplicate]

As the Sun orbits the Milky Way, I understand that it also moves up and down through the plane of the Galaxy. How long does this movement take and can we tell where we are in the current cycle.
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Are the distribution of globular cluster systems in giant elliptical galaxies spherical?

I have been trying to find literature sources on the posted question in the title. The only source I found is from a 1991 review by William Harris which is provided here. In the review, the author ...
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1answer
99 views

What is the distance between solar system and a distant galaxy

When we say a galaxy is 300 million light-years away, is that its distance now or 300 million years ago?
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1answer
1k views

Is oxygen an alpha element?

Type II (core-collapse) supernovae occur shortly after star formation and enrich a galaxy with $\alpha$ elements such as O, C, NE, Mg, Ca and Si. On the other hand, Type Ia supernovae occur on a more ...
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1answer
114 views

How to extract galaxy spectra for different radii in Python for spectra taken by long slit spectrograph?

I am trying to extract the kinematics from the elliptical galaxy NGC 4697 using the Fourier Correlation Quotient (FCQ) algorithm described by Bender (http://adsabs.harvard.edu/full/1990A%26A...229.....
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1answer
47 views

Can the pebbles growth model be applied to the rotations of planetary systems? [duplicate]

I've just read the University of Amsterdam 2019 News item Pebbles determine the direction in which planets rotate (which links to R.G.Visser et al (2020) Spinning up planetary bodies by pebble ...
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4answers
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1answer
140 views

Can violet astronomical objects exist?

According to black-body radiation, violet stars are not possible. Even if there are 1 million Kelvin, they are blue, not violet. But are violet galaxies, nebulae, clusters etc. possible? Google found ...
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1answer
949 views

How big is the energy content of the magnetic field of the Milky Way?

Galaxies have associated magnetic fields. So does the Sun and so does the Earth. In the case of the Earth and Sun it seems clear that the energy content of the magnetic fields is much less than their ...
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Questions re galaxies clusters and galaxies mergers within them

An introduction (containing the info I gathered from several Wikipedia articles). A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of ...
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1answer
104 views

Why is the Milky Way's SMBH inactive?

Our galaxy is not an active galactic nucleus (AGN). With so many stars and so much gas orbiting it, as explained here Central kiloparsec of Seyfert and inactive host galaxies: a comparison of two-...
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187 views

Why was it so difficult to figure out the form of the Milky Way?

The exact form of the Milky Way was figured out the in early fifties of the 20-th century. Why did it take so long to see? Is it because we are in the "middle" of it? In general, it's easier ...

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