Census of Extended Sources in the First 2MASS Working Release DB

The "release" working database represents the larger set from which the Extended Source Catalog will be derived. To date, the prescription for generating the catalog is as follows:

• Mag thresholds: J <= 15.1, K <= 13.5
  (there is also an SNR threshold of >=7, but I'll ignore this for now since the mag threshold takes care of low snr srcs)
  
• "E" and "G" score thresholds:
  0 < "E" <= 1.4, OR, 0 < "G" <= 1.4
  
• Removal of dupes, including inscan dupes and cross-scan dupes (for the stat below, I have NOT attempted to remove scan-scan dupes, since this will be some DB task assigned later)
  
• Removal of artifacts (streaks, bright stars, etc)
  (again, nothing has been removed in the stats below)

Detailed summary of extended source counts as a function of stellar source density. The counts reflects all extended sources that pass the criteria given above (but note exceptions).

Ext. Sources per scan
or equivalently, per sq. degree
counts are broken down in "monthly" groups:
970601_970630n
970701_970731n
970801_970831n
970901_970930n
971001_971031n
971101_971130n
971201_971231n
980101_980131n


Ext. Sources per scan for Jan 1998 Here I a list of Ext. Sources in a scan by scan breakdown

Summary of Extended Sources Per Scan Per Density

density	#scans	#srcs	#srcs/scan
2.60	747	42043	56.3
2.80	740	41375	55.9
3.00	727	34156	47.0
3.20	374	14838	39.7
3.40	295	9938	33.7
3.60	315	7865	25.0
3.80	46	646	14.0
4.00	40	224	5.6
4.20	39	154	3.9
4.40	34	74	2.2
4.60	13	21	1.6

NED matches with 2MASS extractions
and the RA-DEC skyplot,
showing the 2mass sources (white points) and the NED matches (green points). The red line is GLAT=0.