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Most tables available through this web site have an integer "snapnum" column.
This column indexes the output snapshots from the different simulations described
here.
Each snapshot corresponds to a different redshift. And though the redshifts are generally also stored in the catalogues,
it is in general MUCH more efficient to base queries for specific snapshots on the snapnum column.
When indexes have been defined for speeding up requests for particular snapshots, almost always the snapnum column
has been used.
The relation between snapnum and redshift varies between simulations, and also between original versions of the
catalogues and their counterparts scaled to different cosmologies.
This database contains the following tables describing these relations:
- MR: snapshots from original Millennium and milli-Millennium simulations.
Equivalent to millimil..Snapshots and MField..Snapshots
- MRII: snapshots from original Millennium-II and mini-Millennium-II simulations.
Equivalent to MillenniumII..Snapshots
- MR7: snapshots from WMAP7-Millennium simulation
- MRscWMAP7: snapshots from Millennium scaled to WMAP7 cosmology. NOTE the last snapshot (63) corresponds to
negative redshift, i.e. is in the future!
Redshift 0 corresponds to snapshot 53.
- MRIIscWMAP7: snapshots from Millennium-II scaled to WMAP7 cosmology. NOTE the last snapshot (67) corresponds to negative redshift, i.e. is in the future!
Redshift 0 corresponds to snapshot 57.
All tables have the same design:
| column | type | UCD | unit | description |
| snapnum | integer | | | The index of the snapshot in the list of outputs orderd by time. |
| a | real | | | The scale factor t the time of this snapshot |
| z | real | | | The redshift in full precision |
| Hz | real | | km/s/Mpc | The Hubble parameter at the time of this snapshot |
| lookBackTime | real | | 109 years | The lookback time corresponding to the snapshot |
To find the relation between redshift and snapnum simply run a query like the following:
select *
from snapshots..MRscWMAP7
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