3.2.1  :  Science Questions

In analogy with the procedure followed in the design of the SDSS database (see http://arxiv.org/abs/cs.DB/0202014 for a description) we have asked associated theoretical astrophysicists for a set of typical questions they would want to be able to "ask" of the system. The goal is that the design of the database and the supporting periferal software should support the translation of these questions into SQL. The original set of questions is the following:

  1. Return the galaxies residing in halos of mass between 10^13 and 10^14 solar masses.
  2. Return the galaxy content at z=3 of the progenitors of a halo identified at z=0
  3. Return all the galaxies within a sphere of radius 3Mpc around a particular halo
  4. Return the complete halo merger tree for a halo identified at z=0
  5. Find positions and velocities for all galaxies at redshift zero with B-luminosity, colour and bulge-to-disk ratio within given intervals.
  6. Find properties of all galaxies in haloes of mass 10**14 at redshift 1 which have had a major merger (mass-ratio < 4:1) since redshift 1.5.
  7. Find all the z=3 progenitors of z=0 red ellipticals (i.e. B-V>0.8 B/T > 0.5)
  8. Find the descendents at z=1 of all LBG's (i.e. galaxies with SFR>10 Msun/yr) at z=3
  9. Make a list of all haloes at z=3 which contain a galaxy of mass >10**9 Msun which is a progenitor of BCG's in z=0 cluster of mass >10**14.5
  10. Find all z=3 galaxies which have NO z=0 descendent.
  11. Return the complete galaxy merging history for a given z=0 galaxy.
  12. Find all the z=2 galaxies which were within 1Mpc of a LBG (i.e. SFR>10Msun/yr) at some previous redshift.

Some of these queries can be answered using basic SQL on a straightforward database schema. For example, demo queries Halo 1 and Galaxy 1 below are examples of questions for properties of galaxies or halos such as question 1 and 6. The more tricky questions are those where the evolution/history of the galaxy or halo formation process is involved or where spatial relations are required. To deal with those more complex questions using not overly involved queries, whilst maintaining acceptable response times we have made some special design choices that will be described in the following two paragraphs.