# Cosmic Super-Voids

1. Aug 26, 2008

### Barnak

I need to convert some data about cosmic Voids, from Mpc/h to LY. What is the conversion factor ?

More specifically, I'm trying to adapt the voids list found in this paper (p. 313) : [B]http://adsabs.harvard.edu/abs/1994MNRAS.269..301E[/B][/URL]
to show the voids distribution in [B][I]Celestia[/I][/B], a free 3D astronomy software.

For example, the first item in the list of 27 voids looks like this :

[B]No.------alpha-------delta---------Dist.--------Diam.
--------------------------------------(Mpc / h)---(Mpc / h)
-------------------------------------------------------------------------------------
1______19,0______-57,1_____134_______88 [/B]

In the paper, they gives [B]h = Hubble's constant in units of 100 km/sec/MPc[/B], so with Hubble constant = 73,2 km/sec/Mpc, I get [B]h = 0.732[/B]. Right ? But then it doesn't make any sense in Celestia : the voids distribution doesn't match the galactic distribution at all ! The voids spheres are way too large, as you can see on the following picture.

Each yellow sphere represents a void, according to the paper (with radius = half the quoted diameter). It's evident that this distribution doesn't match the marked galactic distribution (small dots). The yellow spheres are way too large. I'm yet unable to figure out what I may be doing wrong.

So how am I supposed to translate the data to LY ?

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Last edited by a moderator: Apr 23, 2017
2. Aug 27, 2008

### scupydog

Mpc/h is a unit of speed and a light year is a unit of distance so i dont think there can be a ratio

3. Aug 27, 2008

### Barnak

Well, isn't h = H0/(100 km/sec/Mpc), so a unitless quantity ? If it's a velocity unit, it should be related to Hubble's law : v = H0 * d, then d = v/H0 or v/h ??