Celestia Forums

COSMO-CELESTIA ! ( to Fridger)

It may be interesting to add yet another layer to Celestia, according to these pages (or better, Fridger ?) :

http://en.wikipedia.org/wiki/Void_(astronomy)
http://en.wikipedia.org/wiki/List_of_galaxy_clusters
http://en.wikipedia.org/wiki/List_of_superclusters
http://en.wikipedia.org/wiki/Galaxy_filament

Labels of super-clusters, voids and filaments.

A project for the near future. Maybe...

Would be really nice to have a model using blobs appearing once you reach a certain distance from the MW, showing the super clusters like this map:

Chris L, what kind of labels should I use for this ? I'm not sure "Nebula" 3ds labels would be a good thing, in this case (because of orientation dependence). Maybe a new kind of location label, at the galactic scale ?

It may be very hard to get the coordinates of labels on this picture :



I'll need some help for this.

Also, the labels should be looking like our constellations labels (with a different color).

Cham wrote:It may be very hard to get the coordinates of labels on this picture :...

It's not possible, you need some kind of database...

Cham wrote:Chris L, what kind of labels should I use for this ? I'm not sure "Nebula" 3ds labels would be a good thing, in this case (because of orientation dependence). Maybe a new kind of location label, at the galactic scale ?

I think that what we need for this is support for markers that aren't attached to any particular object.

--Chris

chris wrote:

Cham wrote:Chris L, what kind of labels should I use for this ? I'm not sure "Nebula" 3ds labels would be a good thing, in this case (because of orientation dependence). Maybe a new kind of location label, at the galactic scale ?

I think that what we need for this is support for markers that aren't attached to any particular object.

--Chris

Markers could do it, but then we need markers WITHOUT any symbol attached to them. Only text with custom size (to have something similar to the constellation labels).

This paper gives the coordinates (galactic ?) of 27 "void" centers, and their size :

http://articles.adsabs.harvard.edu/cgi- ... etype=.pdf

See the table at page 313.

I could use the DATA to built something for "COSMO"-Celestia. However, the distances are given in [tex]h^{-1} Mpc[/tex]. What value should I use for [tex]h[/tex] (Fridger ?).

Cham wrote:This paper gives the coordinates (galactic ?) of 27 "void" centers, and their size :

http://articles.adsabs.harvard.edu/cgi- ... etype=.pdf

See the table at page 313.

I could use the DATA to built something for "COSMO"-Celestia. However, the distances are given in [tex]h^{-1} Mpc[/tex]. What value should I use for [tex]h[/tex] (Fridger ?).

is it [tex]h \mbox{ or } \overline{h}[/tex]??

In the latter case [tex]\overline{h} = 1[/tex], of course

Fridger

t00fri wrote:is it [tex]h \mbox{ or } \overline{h}[/tex]??

In the latter case [tex]\overline{h} = 1[/tex], of course

Please Fridger, look at the table on page 313. It is [tex]h[/tex]. I'm guessing [tex]h=H_{0}/100[/tex], but then I'm not sure to understand the units since [tex]h[/tex] is dimensionless while [tex]H_{0}[/tex] isn't. Is it 100 = 100 km/sec per Mpc ?

At the bottom of the first page on the paper and going over to the next page...

h is the Hubble constant in units of 100 km s^-1 Mpc^-1

Here's the table in question :


Guys, do you confirm that the coordinates are in the galactic system ?

ajtribick wrote:At the bottom of the first page on the paper and going over to the next page...

h is the Hubble constant in units of 100 km s^-1 Mpc^-1

Sorry I am kind of busy and have answered already many questions of Cham via email today and in the recent past. That's why I did not look at that table and rather replied with a joke (It will never happen again ).

Indeed little h is a popular abreviation for the Hubble constant normalized to the above reference value

Fridger

Here's the "voids" table converted to text. It's ready to use in a spreadsheet to convert the data in something Celestia could recognize.


(Why is the "code" format in the forum forgets about all the tabulations, in the table ? Geez this is annoying !)

Cham wrote:Here's the "voids" table converted to text. It's ready to use in a spreadsheet to convert the data in something Celestia could recognize.

Without asking for labels immediately, can you try to display a translucent sphere for each voids to see their positions in Celestia?

ElChristou wrote:

Cham wrote:Here's the "voids" table converted to text. It's ready to use in a spreadsheet to convert the data in something Celestia could recognize.

Without asking for labels immediately, can you try to display a translucent sphere for each voids to see their positions in Celestia?

This is exactly what I had in mind for a first test layer. However, what I think should be best is a simple label (constellation like) placed at the center of the void (and also at the center of the super-cluster for that case). The label should rotate around its center, instead of the lower-left corner, exactly like what the constellation labels are doing.

By the way, we should have something similar for the Milky Way arms.

Note to myself : Voids catalogue in this paper :

http://arxiv.org/pdf/astro-ph/9503044

Catalogue of super-clusters here :
http://www.aai.ee/~einasto/sclcat12.pdf

Related site :
http://spider.ipac.caltech.edu/staff/ja ... apers/LSS/

Voids list with coordinates :
http://www.atlasoftheuniverse.com/nearsc.html

A paper which defines clearly the various distance definitions used in cosmology :
http://www.physics.rutgers.edu/grad/608 ... tances.pdf

And some related page on distances :
http://www.atlasoftheuniverse.com/redshift.html

Here's a distribution of galactic clusters in Celestia (up to 100 MLY from Sol). Sadly, there are lots of distance discrepancies with all the databases I tested and Fridger's deepsky database. The match is extremely crude in 3D :


The Milky Way is the small green dot in the middle of the pictures.

Another view :


In the cases of voids, it's terrible. No match at all with Celestia's deepsky.dsc, and yet I'm pretty sure I didn't made any error.

Any zip to test?

There are numerous things that should be tested with your results:

• on cosmological scales there are different inequivalent definitions of /distance/! Are you sure always the same definition has been used? Are the Hubble constants compatible?
• What are the measurement institutions of your data on galactic clusters and voids? Sloan DSS?
• possible bugs. What kind of cross checks were made in your calculations that underline their correctness?

Fridger