The Photometry Working Group (PWG) has recommended the C1M system as the baseline medium-band photometry system for Gaia. This follows detailed studies of various proposed systems and evaluation of their performance in characterizing the scientific targets (see also Picture of the Week, 2005-01-10).
In selecting the C1M system (renamed from S5M) the PWG took account of the main astrophysical parameters to characterize the stellar galactic populations (chemical abundances and ages). The MBP data will have a lower angular resolution than the BBP and, for non-crowded regions, will be combined with the C1B BBP data for estimating astrophysical parameters.
The figure above shows the selected baseline filter system for Gaia's medium-band photometry (C1M). The C1M system has 8 blue and 6 red bands; one of the red bands will cover the same spectral region as the Radial Velocity Spectrometer.
Further information about the selection of the MBP filter system, including specific details of this system and other proposals, are available in MBP photometric systems evaluation, UB-PWG-029, Jordi et al. 2004 (in Livelink) and references therein. See also the Photometry Working Group web site (under PS Optimization).
Image courtesy François Mignard.
[High resolution image available]