http://www.astro.ku.dk/~erik/gaia/71.phot.systems Tables of photometric systems ============================= SAG_CUO_71 E. Hoeg 5 April 2000 ABSTRACT: Photometric filter systems with relevance for the discussions of systems proposed for GAIA are described and presented in tabular form. The following six systems are tabulated: UBVRcIc, Sloan, and Geneva, and specific systems proposed for GAIA, here called 1G, 2A and 1F. ===== Introduction A number of photometric systems for GAIA have been discussed in the course of 1999. The so-called F system of 4 broad and 11 medium bands was chosen as preliminary baseline at a SAG meeting in May 1999. A Stromvil-based system, hereafter called 1G was proposed in early 1999. An improvement hereof, the 2G system, will be proposed in the near future, including a graphical overview of relevant systems. Further discussions are required before the optimal system for GAIA can be defined in a way that is convincing and documented. The following documentation of the various proposals and other related filter systems in tabular form could be useful for the coming discussion. The systems are: Sloan, Fukugita et al. 1996, AJ 111, 1748. See Table 1. 1G, RR1.1, p.40, based on the Stromvil system. See Table 2. 2A, RR1.1, p.42, Asiago Photometric System (APS II). See Table 3. 1F, RR1.3, p.121, based on the Geneva system. See Tables 4 and 5. Geneva, Rufener & Nicolet 1988, A&A 206, 357. See Table 6. Johnson-Cousins UBVRcIc. See Table 7. ===== Explanation to the Tables The tables give the central wavelength (CW), full width at half maximum (FWHM), the two half-maximum wavelengths (HMW) of each filter, QE at centre, Integration time, and notes. Centre = CW = mean value of the two HMWs for the filter. This will be different from the effective wave length in case of skew filters. FWHM = the difference between the two HMWs for the filter. Filters are listed in sequence of wavelength in the first tables in order to facilitate comparison between systems, but another sequence may be preferred in the focal plane (see Table 5). The UBVRI, Sloan and Geneva systems are included, and three systems which have been proposed for GAIA, these latter here named by the letters 1G, 2A, 1F. This designation will allow improved versions to be named 2G, 3A etc., resulting in a final G system for GAIA. The passbands are designated, e.g., 1F45B for a band in the BBP at 450 nm in the 1F system, and 1F41 for a band in the MBP at 410 nm. This holds even though e.g. the band at 330 nm has the same width in the BBP and MBP and is thus designated respectively 1F33B and 1F33. The widest band, without filter, is called G, or Gw if required in the context. Abbreviations: RR#1.1 : Red Report version #1.1, early 1999 RR#1.6 : Red Report version #1.6, 15 Mar. 2000 (very close to final). --------------------------------------------------------- ===== Transmission curves The transmission curves should also be documented. They are assumed to be almost rectangular for the 1G system, with low wings as is possible with interference filters. A central transmission of 0.80 is assumed for the 1G system. Tables of realistic transmissions should be provided. Curves for the 2A system are shown in the Baltic Astronomy paper (Vol. 8, 123-138, 1999). Tables of realistic transmissions should be provided. The 1F system is implemented by coloured glasses, represented by theoretical response functions with very long wings (Fig.2.12, RR1.6). Transmission curves have been received at Copenhagen in a number of emails from X. Luri and C. Jordi. Luri could perhaps provide this documentation in a single file with description? Other proposers should then use the same file format for exchange of transmission curves as required in our coming discussions. --------------------------------------------------------- ===== Sloan filters Table 1. Sloan filters. Fukugita et al. 1996, AJ 111, 1748, Table 2a (rounded values). CCD as in Fig.1, thinned UV-coated SITe CCD. The QE shape of this CCD is very similar to that of the CCD#1B to be used for the broad bands of GAIA. The Sloan bands are realized by colour glass, and are essentially non-overlapping, say the authors. We list the half-maximum wavelength (HMW) in a separate column. The QE of the CCD is given for the wavelength in the Centre column, and also for the red tail of the CCD which defines one side of the z' filter. Name Centre HMW FWHM QE nm nm nm % Sloan 320 u' 350 60 30 380 410 g' 480 140 62 550 555 r' 625 140 65 695 695 i' 770 150 56 845 840 z' 910 140 30 Red tail of QE: 950 20 980 1000 10 1050 0 --------------------------------------------------------- ===== The 1G system The BBP consists of 5 bands covering the range >400 nm. The MBP consists of the 7 Stromvil bands and 3 bands at the Paschen jump. The 1G system will soon be replaced by the improved 2G system. Table 2. BBP and MBP filters of the 1G system. The system is described in CUO_58 of 11 Feb 1999. It was called G1 in RR#1.1, Table 3 on p.40, Section 2.3.4. The system was designed for the CCD#1B in both BBP and MBP. Names Centre FWHM QE t Notes nm nm % s BBP, CCD#1B 1G45B f 445 110 84 0.86 1G55B g 550 100 80 0.86 1G65B r 650 100 76 0.86 1G75B i 750 100 60 0.86 1G85B z 850 100 35 0.86 ---- BBP total 4.30 s MBP, CCD#1B 1G35 u 345 40 65 2*4.8 1G38 P 380 30 77 2*4.8 1G41 v 405 20 84 4.8 1G46 b 460 20 84 4.8 1G52 Z 515 20 82 4.8 1G55 y 545 20 80 4.8 1G66 S 655 20 75 4.8 1G80 p1 800 40 46 4.8 1G88 p2 875 30 28 4.8 1G94 p3 938 20 14 2*4.8 ---- MBP total integration 62.4 s ~ 2 deg MBP total transit time 90 s ~ 3 deg including spaces between CCDs Total means reflected and transmitted through dichroic filter. --------------------------------------------------------- ===== The 2A system This system is, according to Munari, considered to be superseded by the 1F system. The system was called G2 in RR#1.1, Table 4 on p.42, Section 2.3.5. Munari wrote in an email to me on 2 Nov. 1999: "The presently named F system is the result of an extension of the second version of the Asiago Photometric System (APS-II), as described in Baltic Astronomy 8, 123, (1999), which includes interesting suggestions by Grenon. I would like to remind that the first version of APS might still be of [first version : internal document of the Photometric Working Group UM-PWG-007, with additional notes in UM-PWG-008]. some utility if a larger number of photometric bands could fit. In this connection it should perhaps be considered that Grenon's scheme makes use of a larger number of bands than APS-II [=2A]. Now, in order to produce a consistent red report for GAIA in time during the decision process, I understood that a good baseline is provided by the F System. We are further developing the APS with massive tests and calibrations on extant spectral data bases including our known observations and I will let you known when the results will be fixed. " Table 3. BBP and MBP filters of the 2A system. No specific CCD is mentioned in the descriptions, but in this table the QE for the CCD#1B is assumed in both BBP and MBP. Name Centre FWHM QE t Notes nm nm % s BBP, CCD#1B 2A30B 300 140 48 0.86 2A48B 480 150 84 0.86 2A63B 630 150 77 0.86 2A79B 792 170 46 0.86 2A96B 964 170 10 0.86 ---- BBP total 4.30 s MBP, CCD#1B 2A39 386 19 79 - 2A41 410 18 84 - 2A43 430 12 84 - 2A52 517 8 83 - 2A53 531 17 81 - 2A66 656 17 76 - 2A84 839 18 37 - 2A85 853 12 35 - ---- - MBP total integration available 60 s ~ 2 deg, but was not specified. MBP total transit time 90 s ~ 3 deg including spaces between CCDs Total means reflected and transmitted through dichroic filter. --------------------------------------------------------- ====== The 1F system The 1F system is given in the following Table 4 in a simple form containing only the 4+11 colour filters, given in the sequence of wavelength. The full focal plane layout for the MBP in the Spectro telescope for the 1F system is given in a following section (Table 5). The CCD#1B (see following section for reference to the red report) is adopted for the SSMs, for the BBP and for the MBP filters with $lambda < 550$~nm. The more red-sensitive CCD#2 is assumed for the other MBP filters. The corresponding QE at the central wavelength is listed. Table 4. The 1F system. Name Centre FWHM QE t Notes nm nm % s BBP, CCD#1B 1F33B 326 82 58 0.86 (1) 1F45B 448 132 84 0.86 1F63B 628 208 77 0.86 1F83B 826 155 39 0.86 ---- BBP total 3.44 s MBP, CCD#1B SSM0 550 500 - 0.004 G band, bright stars SSM1 550 500 - 3 G band = no filter 1F33 326 82 58 3*3 (1) 1F41 405 60 84 2*3 Note: only 1*3s in CUO_68 1F47 465 45 84 3 1F51 508 27 83 2*3 MBP, CCD#2 1F57 570 90 75 3 1F65N 656 4 84 3 1F67 674 116 87 3 1F75 747 28 92 3 1F78 778 31 91 3 1F82 816 48 90 3 1F89 894 48 82 3 Spaces 12*1 (2) Spare time 0 ---- MBP total transit time 60 s = 2 deg MBP total integration 15*3 s = 45 s (1) The FWHM of 1F33 is 82 nm, according to Table 3.2 in draft 1.3 from where all centre and FWHM values are taken. The FWHM was 96 nm in the original Table D in CUO_68, taken from information given in May 1999. Draft 1.2 also gives 82 nm for 1F33 (but it does not list the 1F63B band !). (2) For a MBP system with N different filters we assume N+1 spaces of 1 s. The space between CCDs is usually 2.4 mm = 1 s, but much less space (e.g. <0.1 mm) is required between the CCDs for repeated measurement of a colour, i.e. 1F33 and 1F51. Therefore 11+1= 12 spaces of 1s are counted. --------------------------------------------------------- ====== Focal plane layout for MBP of the 1F system See the MBP focal plane layout in Fig.2.13, p.141 of RR#1.6. As Table D in CUO_68 (with a correction of F41) : Table 5. Focal plane layout for the Spectro telescope, allocation of space and time, also for spectrometric sky mappers (SSM), 11-colour photometry (1F system), and radial velocity spectrometer (RVS). The CCD#1B (see Fig.~3.24) and Table ~3.15 of RR#1.6) is adopted for the SSMs and the filters with $lambda < 550$~nm. The more red-sensitive CCD#2 is assumed for the other filters and the RVS. Name Centre FWHM t Notes nm nm s SSM0 (No Filter) 0.004 G band, bright stars SSM1 (No Filter) 3 G band 1F57 570 90 3 (1) 1F67 674 116 3 1F82 816 48 3 (2) 1F33 326 82 3*3 (4) 1F41 405 60 2*3 Note: only 1*3s in CUO_68 <-- Centre of field 1F47 465 45 3 1F51 508 27 2*3 1F65N 656 4 3 1F75 747 28 3 1F78 778 31 3 1F89 894 48 3 Spaces 12*1 (3) ---- 60...60 RVS 30 Placed at centre of field Extension of RVS ? 30 Placed at centre of field ---- Total transit time 120 Available 4 deg 120 ---- Spare 0s Notes: (1) The filters 1F57 and 1F67 with fairly wide bands are placed right after the SSM in order to detect as faint as possible fast-moving asteroids. (2) The 1F82 band is close to the centre of the band at 850 nm used for radial-velocity measurement. A photometric value in this band should therefore probably be obtained onboard and be used to decide whether an RVS will be accurate enough to warrant a transmission to the ground. (3) The space between CCDs is usually 2.4 mm = 1 s, but much less space (e.g. <0.1 mm) is required between the CCDs for repeated measurement of a colour, i.e. 1F33 and 1F51. Therefore only 12 spaces of 1s are counted. (4) FWHM for 1F33 has been updated to 82 nm from the obsolete value of 96 nm. --------------------------------------------------------- ====== Geneva system Reference: Rufener & Nicolet 1988, A&A 206, 357. The Table 1 gives the filter responses and is used to derive the following Table 6. Fig.1 in the paper shows a graphic of the responses given in Table 1. The shapes are almost triangular, but sometimes quite skew so that the peak is not always at the central wavelength given in Table 6. Table 6. Geneva system. No. Name Centre HMW FWHM nm nm nm i Geneva 325 1 U 348 45 370 379 3 B1 398 38 417 382 0 B 421 78 460 426 4 B2 449 46 472 512 5 V1 538 51 563 507 2 V 541 68 575 558 6 G 579 42 600 --------------------------------------------------------- ====== UBVRcIc system References: UBV are Johnson system, ApJ 141, 923 (1965). Rc, Ic are adapted from MNASSA 33, 15 (1974). Revised response curves of the UBVsystem: A. Azusienis and V. Straizys, Astron. Zh. 46, 402, 1969 = Soviet Astron. 13, 316, 1969. It is noted that the Johnson UBVRI has much wider bands in R and I than the Cousins: 215 and 225 nm respectively instead of 152 and 110 nm. Table 7. UBVRcIc system. Name Centre HMW FWHM nm nm nm UBVRcIc 340 U 365 52 390 395 B 445 101 495 510 V 550 83 590 570 Rc 645 152 722 732 Ic 787 110 842 -----------------------------======================-------------