Celestia Forums

Hi,

in this thread, I will soon continue to describe the ongoing improvements in my 'deepsky' galaxy data base for the Celestia distribution.

First of all, some detailed, basic status information about inherent data documentation, errors and remaining distance uncertainties I have written in another thread.

This important information should better be located collecively in this thread, but here is the quote, at least:

http://www.celestiaproject.net/forum/viewtopic ... 83&start=2

A further important goal in the forthcoming upgrade of deepsky.dsc along with its PERL script deepsky.pl is a complete and accurate implementation of the local group of galaxies, including many familiar dwarf galaxies .

Bye Fridger

Let me collect here some more information about the so-called Local Group (LG) of galaxies:

Definition:
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The Local Group is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a 10 million light-year =3.1 Mpc diameter

The two most massive members of the group are the Milky Way and the Andromeda Galaxy M31. These two barred spirals each have a system of satellite galaxies.

* The Milky Way's satellite system consists of Sag DEG, Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), Canis Major Dwarf, Ursa Minor Dwarf, Draco Dwarf, Carina Dwarf, Sextans Dwarf, Sculptor Dwarf, Fornax Dwarf, Leo I, Leo II, Tucana Dwarf, and Ursa Major Dwarf.

* Andromeda's satellite system comprises M32, M110, NGC 147, NGC 185, And I, And II, And III, And IV, And V, Pegasus dSph, Cassiopeia Dwarf, And VIII, And IX, and And X.

Have a look to more details from the respective Wiki:

http://en.wikipedia.org/wiki/Local_Group

along with a more complete list of member galaxies.

Bye Fridger

Do you have a target size for this, and how do you plan to filter the DB down.


The galaxy surveys implemented as cmod's by Selden Ball come to 28.5megs in size, and that only implements the galaxies as point locations (i.e. no names, or brightness info is included).

Kolano wrote:Do you have a target size for this, and how do you plan to filter the DB down.


The galaxy surveys implemented as cmod's by Selden Ball come to 28.5megs in size, and that only implements the galaxies as point locations (i.e. no names, or brightness info is included).

You must be referring to something else...

I am not discussing here my cosmological aims (=> "Cosmo-Celestia") . This thread rather serves to more standard development work: a thorough overhauling of my present database of 10608 galaxies mainly as concerns accuracy in galaxy distances. In other words, we talk about 'deepsky.dsc' and the corresponding template .png images in the official Celestia distribution. Also as indicated above, I shall include the complete set of galaxies of the "Local Group".

Although there are 10000+ galaxies in my present 'deepsky' database, including brightness, sizes, orientations, names and morphological type, the "target size" is very modest, indeed . No need to cut anything down.

Bye Fridger

I see. Yes, I was getting confused with "Cosmo-Celestia". Chris's recent talk of supporting point sprites got me exited about that project.

Here is the next progress report on my implementation of ~400 new accurately measured nearby galactic objects in a "near" volume of V < (10 Mpc)^3.

The corresponding quite recent catalog,
J/AJ/127/2031 Catalog of neighboring galaxies (Karachentsev+, 2004),
http://cdsweb.u-strasbg.fr/viz-bin/Cat?J/AJ/127/2031
contains most needed parameters. The dataset also contains the complete Local Group.

Presently, I am checking my new PERL code and try to make it more transparent with future expansions in mind.

The main challenge is that every new catalog uses another syntax convention for the galaxies from the numerous catalogs. So the PERL code has to be really flexible to be able to cross-correlate these many data from different sources. One typo or a too restricted "regular expression" for some galaxy names and some galxies will be skipped...

This upgrade involved a lot of (re)coding. Also the PERL code grew from 900 to 1100 lines with 4(!) new catalog files added...

Let me display a few first images, to give you a flavour. It's much more fun however to actually maneuver through this genuine 3d constellation of satellite dwarf galaxies floating around the monster members, Milky Way, Andromeda (M31) and Triangulum (M33)

Soon I'll make a first test version available.

Here is a first view using my recent z-dist celx script. According to extensive tests by the authors of the "neighboring galaxy catalog", it is ~80% complete withing a volume of (8 Mpc)^3. NOT bad!



You can clearly see the various overdense regions (clusters) of dwarf galaxies etc. The green dot in the center is the Milky Way.

Next comes a neat display of the main Local Group satellites of the Milky Way after implementation of the new catalog. The view is right onto the galactic plane.



Finally, here is the analog view of the main Local group satellites of Andomeda (M31) and Triangulum (M33)



Enjoy,
Bye Fridger