sncat proposal

New supernovae catalogue proposal

Note: This is a WIP (work in progress) and intended for internal usage.

There are several reasons to revise our SAI SN catalogue.

• We want to abandon historical monolithic table and follow relational approach and normalize data - map objects and connections between them to relations;
• We propose to use sid (supernovae identificator) as a reference name instead of Zwicky's nomenclature, see [[sid_details?]] below;
• We want to add links to images and supernovae light curves (we still need to find out how to store light curves in VO-compatible way, though). Also, we want to reorganize some odd internal atrributes to more friendly values and follow IVOA UCD convention, CDS Strasburg list;

Objects (primary keys are shown in parentheses):

• Supernovae (sn) - primary key (sid)
• Host galaxy (galaxy) - primary key (gid)
• SN Search Team (team) - primary key (tid)

Auxiliary maps:

• Supernovae - Galaxy (sn_galaxy_map) - (sid,gid)
• Supernovae - SN Search Team (sn_team_map) - (sid,tid)

These relations allows us to run basic queries

• All info about specific supernova:

 select s.*, g.* from sn s, galaxy g, sn_galaxy_map sg 
 where s.name = '1972e' and s.sid = sg.sid and g.gid = sg.gid;

• All supernovae in specific galaxy:

 select s.*, g.* from sn s, galaxy g, sn_galaxy_map sg
 where g.name = 'NGC5253' and g.gid = sg.sid and s.sid = sg.sid;

• All info about supernovae discovered by SAI SN team:

 select s.*, g.*  from sn s, galaxy g, team t, sn_team_map st, sn_galaxy_map sg 
 where t.name = 'SAI' and st.tid = t.tid and s.sid = st.sid and
       sg.sid = s.sid and sg.gid = g.gid;

[::sid details]

Primary keys are unique (by definition) and non-monotonic integers. Note, they have no special meaning. This looks questionable in regards to supernovae, because historically, supernovae are referenced by their name, introduced by Zwicky. But, actually, this is just a convention, a habit.

The supernova designation, in the standard form, as recommended by the [Dictionary of Astronomical Nomenclature], consisting of the 'SN ' prefix followed by the year it was discovered, and then (if there were multiple supernovae in a particular year) either the upper-case letters 'A' through 'Z' (for the first 26 SNe discovered in a given year) or the lower-case letters 'aa', 'ab', etc. (for the 27th, 28th, etc., SNe discovered in a given year).

Some notes about Zwicky nomenclature:

• poor capacity - it is not adequate even for current rate of supernovae discoveries and will certainly fail in near future
• the year in the designation may be either year of discovery, or year of outburst. For example, SN1962Q was discovered in 1966; SN1985F reached maximum light in 1984.

So then, I don't see any rationale in semantic of supernovae names, they are just unique identifiers. For compatibility reason we'll keep old names, but I suggest to use new nomenclature for supernovae, for example, 1965.23, which roughly indicates the year of discovery and its serial number in this year.

[::Images]

Images are stored in a special location known to application. There could be several images per object, so we need arrays to store filenames in relations.

Filename of images are in following conventions:

• {galaxy.img} - array of presupernova images of galaxy, name-#.ext, where name - is the name of a galaxy (case is important). For example, ngc5253-1.jpg, ngc5253-2.jpg, anonHHMMSS.ss[+-]DDMMSS.ss-1.jpg
• {sn.img} - array of images of galaxy with supernova, SNsid-#.ext. For example, 1965.23-1.jpg