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

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In summary, the conversation is about converting data about cosmic voids from Mpc/h to LY and the confusion surrounding the conversion factor. The individual is trying to adapt a list of voids from a paper to a 3D astronomy software and is having trouble with the voids appearing too large. They are unsure if there is a specific conversion factor for Mpc/h to LY and are seeking clarification on the relationship between h and Hubble's constant.
  • #1
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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  • #2
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
 
  • #3
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 ??
 

1. What is a cosmic super-void?

A cosmic super-void is a vast region of space that is mostly empty, with very few galaxies or other matter. It is the opposite of a cosmic super-cluster, which is a region of space that contains a large number of galaxies.

2. Why do we need to convert from Mpc/h to LY?

Mpc/h stands for megaparsecs per hour, and is a unit of distance often used in cosmology. LY stands for light years, which is another unit of distance commonly used in astronomy. Converting from Mpc/h to LY allows us to better understand and compare distances in the vastness of the universe.

3. What is the conversion factor for Mpc/h to LY?

The conversion factor for Mpc/h to LY is approximately 3.26 million. This means that one megaparsec per hour is equivalent to approximately 3.26 million light years.

4. How do we calculate the conversion from Mpc/h to LY?

To convert from Mpc/h to LY, simply multiply the distance in megaparsecs per hour by 3.26 million. For example, if a cosmic super-void is 10 Mpc/h away, it would be equivalent to approximately 32.6 million light years.

5. What is the significance of converting cosmic super-voids from Mpc/h to LY?

Converting cosmic super-voids from Mpc/h to LY allows us to better understand the vast distances and scales of the universe. It also helps us to compare and analyze different regions of space in a more meaningful way.

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