Questions tagged [galactic-halo]

Questions about the roughly spherical component that extends beyond the visible part of a galaxy, made of a sparse field of stars and globular clusters, gas and dark matter.

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32 views

Is it possible to observe Lyman-continuum emission from extragalactic objects?

Lyman-continuum (LyC) emission is everything blueward of 912 Angstroms (so it includes extreme UV photons, X-rays and gamma rays). There are many low-redshift astrophysical plasmas such as the diffuse ...
4
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2answers
125 views

What is the mean separation between a star and its closest neighbor in the Milky Way halo?

My question is inspired by this previous question, Are there any stars that orbit perpendicular to the Milky Way's galactic plane?. In the great answer posted by @ConnorGarcia, one commenter said he ...
2
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0answers
25 views

Anatomy of a galaxy cluster: understanding the relationship between dark matter halos and subhalos and galaxies within the clusters?

In my understanding, galaxy clusters contain dark matter halos, which in turn contain subhalos, and the subhalos are what surrounds individual galaxies. I know that is a simplified picture, but I am ...
2
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1answer
58 views

Why is the boundary of friends-of-friends (FOF) halo corresponding to iso-density contour?

The friends-of-friends algorithm (hereafter FOF) is commonly used to find halos in cosmological simulations. (For more information, please refer to here and here) I found that some literature argues ...
11
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2answers
2k views

Why do people choose 0.2 as the value of linking length in the friends-of-friends algorithm?

The friends-of-friends algorithm (hereafter FOF) is commonly used to find halos in cosmological simulations. And FOF depends on only one parameter, linking length, $l_\mathrm{link}=b \left(\frac{V_u}{...
36
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2answers
4k views

Are there any stars that orbit perpendicular to the Milky Way's galactic plane?

Most stars orbit in the Milky Way's galactic disc. But is it possible for one to orbit perpendicular to it? Here on Earth since we're inside the galactic plane we can't get a good view of what the ...
3
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1answer
157 views

The contribution of components like dark matter, stars and gas to the mass of a galaxy

I am doing an introductory course in astrophysics and astronomy undergrad level. In it we were taught that the main components of matter in a galaxy are dark matter halo ($M_h$), gas ($M_{gas}$) and ...
2
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0answers
38 views

Plotting Histograms of stellar mass and gas mass given a halo mass

I am an undergrad doing a first course in astronomy. I am working on a small project. In it I have been assigned a halo mass (1.444e12 $M_{sun}$). I want to plot histograms of possible stellar masses ...
2
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1answer
73 views

How do disk-shaped galaxies then form at the sites of spherical galactic halos? Do the halo stars start orbiting or just sit in place?

Phys.org's Astronomers detect large amounts of oxygen in ancient star's atmosphere mentions "Stars like J0815+4729 are referred to as halo stars," explained UC San Diego astrophysicist Adam ...