Populating WLM (and other galaxies) with REAL stars

The home for finished/released addons.
Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Populating WLM (and other galaxies) with REAL stars

Post #1by LukeCEL » 23.12.2017, 19:37

Hi everyone,

Here's something a bit different. Populating galaxies with stars is something that's been done before, but doing so with data from SIMBAD is something new, I believe.

This add-on adds about 370 stars in the dwarf galaxy Wolf-Lundmark-Melotte (WLM). These stars are real, and the data is from SIMBAD. Specifically, I've extracted names, coordinates, and spectral types (if known) from SIMBAD. For stars whose spectral types are not known, variable types have been used to fill in random spectral types; for example, Carbon stars would be given a spectral type of "C". Because the distance of these stars aren't known, I used special formulae to come up with random (but realistic) distances for each of the stars.

Note that in the default version of Celestia, WLM is rendered as a blob (Type "Irr") and not its more elongated shape. So, for the stars to actually fit in the galaxy, go to your galaxies.dsc and replace the definition of WLM with this:

Code: Select all

Galaxy "WLM:Wolf-Lundmark-Melotte:DDO 221"
{
        Type  "E5"
        RA            0.0328
        Dec         -15.4611
        Distance   3.001e+06 # method: rgb
        # Radius        4208
        Radius         10040
        AbsMag        -13.95
        Axis    [ -0.2128  -0.8243  -0.5246]
        Angle    177.0636
        InfoURL  "http://simbad.u-strasbg.fr/sim-id.pl?Ident=NAME WLM Galaxy"
}


Enjoy:
Attachments
wlm.stc.zip
(7.46 KiB) Downloaded 56 times
Last edited by LukeCEL on 29.12.2017, 20:08, edited 1 time in total.

john71
Posts: 319
Joined: 10.08.2016
With us: 1 year 10 months

Post #2by john71 » 24.12.2017, 07:57

Looks quite good, thank you!

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #3by LukeCEL » 29.12.2017, 20:04

(Okay, the newer add-on was lost, so I'll have to reupload it.)

More stars!

Here's about 1600 stars in the Sculptor Dwarf Spheroidal Galaxy (Sculptor dSph). If you look at a picture of the galaxy you'll see it has very blurry edges, and this is reflected in the addon, where stars are even scattered outside the boundaries of the rendered galaxy.

Enjoy:
Attachments
sculptor_dsph.stc.zip
(30.96 KiB) Downloaded 38 times

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #4by LukeCEL » 13.03.2018, 18:43

I finally got off my butt and made another one of these. Here's about 3300 stars in the Fornax Dwarf Spheroidal Galaxy (Fornax dSph). Like Sculptor dSph, the stars are quite scattered. Fornax dSph also happens to have five globular clusters, but I haven't added those yet, and I've kind of forgotten how to do those...

Enjoy:
Attachments
fornax_dsph.stc.zip
(60.79 KiB) Downloaded 30 times

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #5by Gurren Lagann » 14.03.2018, 23:25

Please do Messier 110, please?

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #6by LukeCEL » 18.03.2018, 00:13

Gurren Lagann, I'll try to do Messier 110, but note that sometimes the stars might not be able to be properly fitted into the galaxy. Also, these take a lot of time, which is why it took a few days to finish off the one I was working on. Which is this.

This adds about 670 stars in the Draco Dwarf. Like the previous two files, the stars are quite scattered, and that's a very common thing in dwarf galaxies.

Enjoy:
Attachments
draco_dwarf.stc.zip
(14.48 KiB) Downloaded 25 times

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #7by LukeCEL » 18.03.2018, 16:43

I've published two files. The first one about 140 stars in Messier 110 (M 110). The other adds about 250 stars in Messier 32 (M 32).

For both galaxies, SIMBAD's coverage of the stars is uneven, so the galaxies won't be fully populated, but that's fine.
Attachments
m_110.stc.zip
(3.1 KiB) Downloaded 25 times
m_32.stc.zip
(5.65 KiB) Downloaded 25 times

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #8by Gurren Lagann » 18.03.2018, 19:13

I wonder if you can do M 31/Andromeda and M 33/Triangulum. Or even Smith's Cloud.

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #9by LukeCEL » 18.03.2018, 19:56

Gurren Lagann, M 31 and M 33 are in theory possible but because they're spiral galaxies, populating them is a bit different. It would be easy if they were face-on (inclination = 0°) or edge-on (inclination = 90°) but it's not the case for either of these galaxies.

As for Smith's Cloud, it's just a cloud of hydrogen gas without any stars (probably), and SIMBAD lists no children objects anyway. You could try making a nebula model, maybe?

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #10by Gurren Lagann » 18.03.2018, 20:04

Oh then. Good luck on populating M 31 and M 33!

I'm no model maker btw

EDIT: Jeez, 10790 children for M 31 and 4301 children for M 33

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #11by LukeCEL » 25.03.2018, 20:09

Does anybody know what the "Radius" parameter means when defining a globular cluster in Celestia? There are ways to define the size of a globular cluster, including the half-light radius (r_h) and the tidal radius (r_t). I assumed it meant the tidal radius, but I'm not so sure anymore.

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #12by Gurren Lagann » 27.03.2018, 18:54

The tidal radius, or Hill sphere, is the distance from the center of the globular cluster at which the external gravitation of the galaxy has more influence over the stars in the cluster than does the cluster itself. This is the distance at which the individual stars belonging to a cluster can be separated away by the galaxy.

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #13by LukeCEL » 27.03.2018, 20:54

Gurren Lagann, thanks, but I'm looking for the definition for Celestia code; i.e. which of the three radii it refers to.

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #14by Gurren Lagann » 30.03.2018, 11:34

Maybe the tidal radius? Because the half-light radius is either the CoreRadius or KingConcentration parameters.

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #15by LukeCEL » 30.03.2018, 13:53

This add-on adds 52 globular clusters around the Andromeda Galaxy (M 31).

Many of the parameters are approximations. Some random variation has been added to the "Distance" parameter, so the globular clusters don't appear in one plane. That means that the "CoreRadius" and "AbsMag" will also be slightly skewed. The data were cobbled from seven papers, and Mayall II has been custom-built from data from Ma et al. (2007).
Attachments
globulars_andromeda.dsc.zip
(4.41 KiB) Downloaded 16 times

Avatar
selden
Posts: 10214
Joined: 04.09.2002
With us: 15 years 9 months
Location: NY, USA

Post #16by selden » 30.03.2018, 13:56

Did you manage to determine which radius is used by Celestia?

I was about to suggest that if you compare the values of the parameters used in Celestia's globular cluster catalog file globulars.dsc with the published values for various globular clusters, that should tell you which is meant.
Selden

Gurren Lagann
Posts: 60
Joined: 31.01.2018
With us: 4 months 21 days

Post #17by Gurren Lagann » 30.03.2018, 14:18

LukeCEL wrote:This add-on adds 52 globular clusters around the Andromeda Galaxy (M 31).

Many of the parameters are approximations. Some random variation has been added to the "Distance" parameter, so the globular clusters don't appear in one plane. That means that the "CoreRadius" and "AbsMag" will also be slightly skewed. The data were cobbled from seven papers, and Mayall II has been custom-built from data from Ma et al. (2007).

only the stars are left

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #18by LukeCEL » 30.03.2018, 20:10

selden wrote:Did you manage to determine which radius is used by Celestia?

Sadly I couldn't. Just to be sure, I looked at two globulars, M 71 and 47 Tucanae. 47 Tucanae's "Radius" is 106.7 light years, which at its distance would be 0.416° = 24.96′. This corresponds to the SEDS 2007 catalog, which gives a diameter of 50.0′. M 71's "Radius" is 13.66 light years, which at its distance would be 0.06° = 3.6′. It also corresponds to the SEDS 2007 catalog, which gives a diameter of 7.2′. So, I assumed that it was used for the "Radius" parameter, but when I looked to see its definition, it just said "Apparent dimension in arc minutes".

The "Radius" parameter might just be half the apparent diameter of the object, which is a shame because that's not really rigorously defined. (Also, I may have to re-do my entire file.)

Added after 11 minutes 26 seconds:
If you've downloaded my LMC and SMC add-on, it's fine, because I used the apparent dimensions for that file.

Avatar
selden
Posts: 10214
Joined: 04.09.2002
With us: 15 years 9 months
Location: NY, USA

Post #19by selden » 31.03.2018, 13:51

Another source of info about galactic clusters is the database available at https://heasarc.gsfc.nasa.gov/W3Browse/all/globclust.html
It includes both the "core radius" and the "half light radius" for more than 150 of them.
Selden

Topic author
LukeCEL
Posts: 43
Joined: 26.09.2017
With us: 8 months 25 days

Post #20by LukeCEL » 31.03.2018, 14:59

selden, thank you for that. It won't really be relevant to my add-on, which is about globular clusters around Andromeda, but it might be possible to extract a few more globular clusters to add to the original globulars.dsc file.

Added after 8 hours 54 minutes:
The new version contains only 24 globular clusters, and the new Radius values feel uncomfortably small. For example, Mayall II's radius is 0.0283′ which corresponds to 10.34 ly. That's less than its half-light radius, which conceptually makes no sense...
Attachments
globulars_andromeda.dsc.zip
(3.02 KiB) Downloaded 12 times


Return to “Add-on releases”

Who is online

Users browsing this forum: 1 guest