The GCS will image 10 open star clusters and star-formation associations, covering a total area of 1400 sq. degs, in JHK to a depth K=18.7. The survey requires 74 nights of UKIRT time over 7 years.¹ The GCS will be completed in two stages. The first stage is a single pass in JHK over 1400 sq. degs. The second stage is an additional pass in K over the same 1400 sq. degs, for proper motions, with a baseline of at least 2 years. The parameters of the survey are summarised in the table below. The GCS Survey Head is Nige Hambly.
¹ These figures are revised from the original plan (that appears in the Science Case) of 1600 sq. degs requiring 84 nights, because of the revision of the target list following a search for suitable southern clusters.
|Galactic Clusters Survey
The GCS will measure the stellar mass function in the sub-stellar régime, down to a mass limit ~25MJupiter, and establish the universality of the IMF, or uncover the important factors that explain variation between clusters. The science goals are described in detail on the science case page (dated Nov. 2001).
The 10 targets are listed in the Table below, and their locations are shown in Fig. 1.
|1||Pleiades||open cluster||03 47||+24 07||79|
|2||Alpha Per||open cluster||03 22||+48 37||50|
|3||Praesepe||open cluster||08 40||+19 40||28|
|4||IC 4665||open cluster||17 46||+05 43||0.8|
|5||Taurus-Auriga||SF assoc.||04 30||+25 00||386|
|6||Orion||SF assoc.||05 29||-02 36||314.2|
|7||Sco||SF assoc.||16 10||-23 00||154|
|8||Per-OB2||SF assoc.||03 45||+32 17||12.6|
|9||Hyades||open cluster||04 27||+15 52||292|
|10||Coma-Ber||open cluster||12 25||+26 06||78.5|
Figure 1. Planned final GCS sky coverage. The circles mark the coordinates of the clusters. The size of the symbol scales with the solid angle that will be imaged. The dashed line marks the Galactic plane, and the dotted line marks the ecliptic.
The UKIDSS plan for the first two years of operation is based around an allocation of 290 nights of observing, which is 31% of the 936 nights required to complete the surveys. The GCS will proceed more quickly in the first two years, receiving 30 nights or 41% of the total 74 nights required. The strategy is to cover the entire 1400 sq. degs in a single pass in K, to provide the proper-motion baseline. JH imaging of 460 sq. degs will be completed (one third the total area), essentially following the priority ranking in the table above, modified as follows: only the central 47 sq. degs of the Taurus-Auriga, Orion, and Sco clusters, and the central 146 sq. degs of the Hyades cluster will be imaged, while Coma-Ber will not be imaged. The parameters of the 2-year plan are summarised in the table below.
|Galactic Clusters Survey