Converting Cosmic Super-Voids from Mpc/h to LY - What is the Conversion Factor?

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SUMMARY

The discussion centers on converting cosmic void measurements from Mpc/h to light years (LY) for visualization in Celestia, a 3D astronomy software. The user references a paper that provides a list of voids, specifically noting the Hubble constant of 73.2 km/sec/Mpc, leading to a derived value of h = 0.732. The user encounters discrepancies in the size of voids when visualized, indicating a misunderstanding of the conversion process. The confusion arises from the nature of Mpc/h as a velocity unit and the need for a proper conversion to a distance unit like LY.

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  • Understanding of Hubble's Law and its application in cosmology
  • Familiarity with the concept of cosmic voids and their measurements
  • Knowledge of unit conversions between Mpc/h and light years
  • Experience using Celestia for astronomical visualizations
NEXT STEPS
  • Research the conversion factor from Mpc/h to light years, focusing on the implications of Hubble's constant
  • Learn how to properly visualize cosmic structures in Celestia, including scaling factors
  • Investigate the mathematical relationship between velocity and distance in cosmological contexts
  • Explore additional resources on cosmic voids and their significance in the universe
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Astronomers, astrophysicists, and software developers interested in cosmic structure visualization, particularly those working with Celestia and cosmic void data analysis.

Barnak
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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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Mpc/h is a unit of speed and a light year is a unit of distance so i don't think there can be a ratio
 
scupydog said:
Mpc/h is a unit of speed and a light year is a unit of distance so i don't think there can be a ratio

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 ??
 

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