With the exception of RA,dec position (see below), all search criteria and combined with an AND operation. That is, the returned objects will satisfy all the specified criteria.
There are no compulsory criteria which must be filled in. You could if you wished run a search with no criteria set at all and it would return all objects in the catalogue. This is strongly discouraged though, as it would take a very long time and when the results finally came back, your browser probably would not be able to display it all anyway. The only constraint made on the parameters you fill in is that if a search around a position is made, all three parameters, RA, DEC and RADIUS must be used.
There are two positional search mechanisms.
RA format: hours, minutes and seconds (hh mm ss.ss) or decimal
degrees (d.ddd) e.g.:
12 30 00 or 187.6380
DEC format: degrees, minutes and seconds (+/-dd mm ss.s) or
decimal degrees (+/-d.ddd). e.g.:
-30 30 00 or -30.50
RADIUS format: this is always in arcminutes. e.g.:
If only one RA limit (minimum or maximum) is entered this is assume
to be bounded at
RA=0/24h, so a search with only:
ramax=00 30 0
will be interpreted as ramin=00 00 0 ramax=00 30 0
If both RA limits are used (minimum and maximum) then the search is
done between the limits. In the special case of a search spanning
RA=0h, the search algorithm will also perform a valid search.
ramin=23 30 0 ramax=00 30 0
will result in sources around RA=0h being selected.
|QSO||spectrum with one of more broad lines (>1000 km/s)|
|NELG||spectrum with one or more narrow lines (<1000 km/s)|
|gal||galaxy spectrum with no emission lines|
|star||galactic star spectrum|
|cont||high signal to noise spectrum (S/N>10) with no identifiable emission or absorption features|
There are also a number of sub classes, which are placed after the main
classification in parentheses:
|BAL||broad absorption line QSO|
|DA||DA white dwarf (hydrogen Balmer line dominated)|
|DB||DB white dwarf (neutral helium dominated)|
|DO||DO white dwarf (singly ionized helium dominated)|
|DZ||DZ white dwarf (calcium H,K dominated)|
|DA/M||DA - M dwarf binary|
|DB/M||DB - M dwarf binary|
All these classifications are the same as used in the 2QZ survey. For a fuller description of the classification scheme see the 2QZ papers Croom et al. (2001) - Paper V. or Croom et al. (2003) - Paper XII.
Quality Flag: The quality flag contains information
on both the reliability of the object's type identification and the assigned
Quality = 10 × ID_quality + redshift_quality
ID_quality and redshift_quality are 1, 2 or 3 meaning `Good', `Poor' and `Too poor to classify' respectively. Therefore the best quality objects have a 11 quality flag, while the worst have a 33 quality flag.
Signal-to-noise ratio: Signal-to-noise is calculated as an average over the entire spectrum.
Lastly, when setting the maximum number of records, we recommend that the user doesn't set this value to be too large (> 1000), as the browser will struggle to display the table. In all cases the catalogue file produced as output from the search (there is a link to this at the bottom of the results page) contains all the selected objects, not only those up to the maximum number of rows.