Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5420 Report Date: 18-Jul-95:17:21 Version: ********** Check-in Date: ********** 1.Proposal Title: COLOR-MAGNITUDE DIAGRAMS OF GLOBULAR CLUSTERS IN M31: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category DISTANCE SCALE ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Flavio Fusi pecci 6426 ITALY +39-51-259321 ------------------------------------------------------------------------------------ 7. Abstract The solution of the distance-scale problem is crucial in Astronomy. The main goals of this program are: a) to improve the accuracy of globular cluster distance (and age) determinations by deriving the dependence of Mv(HB) on metallicity and HB morphology, taking advantage of the M31 globular clusters being in practice all at the same distance; b) to study the HB morphologies as a function of various parameters (e.g. metallicity, galactocentric distance, concentration, etc.) for the essential information they may provide on the formation and early evolutionary phases of galaxies. Structural parameters (e.g. core radius, ellipticity, surface brightness profile) can also be derived. With the allocated observing time we can only obtain Colour-Magnitude Diagrams of two globular clusters in M31 using the FOC/96 and the filters F430W (B) and F480LP (V). Besides, two more clusters will be observed in parallel mode (WFC). With the proposed exposure times it will be possible to measure HB stars with an accuracy of approximately 0.1 mag. The number of clusters will not be sufficient to draw any firm conclusion, but this represents the first important step for an accurate feasibility study and for additional future observations. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 10.42 par: 10.42 10. Num targs pri: 2 par: 3 ------------------------------------------------------------------------------------ 11. Instruments requested: FOC WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5420 PI: Flavio Fusi pecci Proposal Title: COLOR-MAGNITUDE DIAGRAMS OF GLOBULAR CLUSTERS IN M31: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Flavio Fusi Pecci 6426 ITALY X Orazio Bendinelli 6460 ITALY X Carla Cacciari 6426 ITALY X Luciana Federici 6426 ITALY X Francesco Ferraro 6426 ITALY X Gianluigi Parmeggiani 6426 ITALY X Franco Zavatti 6460 ITALY X George S. Djorgovsky 1590 USA Ivan R. King 1500 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. The primary targets are: G351 (V=15.16 B-V=0.72) and G280 (V=14.26 B-V=0.92); the parallel targets are G262 and G272, which can both be observed in the WFPC2 FOV when G280 is in FOC/96, for an appropriate value of the roll angle. The observation setup is FOC/96+F430W and FOC/96+F480LP for primary observations, and WFPC2+F555W and WFPC2+F814W for the respective parallel observations. The observing strategy is: Exp.n.1: FOC/96+F430W on G351 + parallel WFPC2+F555W on generic field Exp.n.2: same as n.1 with filters F480LP (FOC) and F814W (WFPC2) Exp.n.3: FOC/96+F430W on G280 + parallel WFPC2+F555W on G262 and G272 Exp.n.4: same as n.3 with filters F480LP (FOC) and F814W (WFPC2). Exposures n.3 and 4 require a special orientation in order to have the two clusters in the parallel field of the WFPC2 while pointing the FOC/96 on the primary target. The optimum Position Angle (N through E) is 63D +/- 3D, which places G272 in WF4 and G262 in WF2. The resulting ORIENT angle is 181D +/- 3D. The exposure times have been calculated in order to reach S/N=10 for a typical HB stars F0V at V=25, observed with FOC/96 through the filters F430W and F480LP. The algorithm used for the exposure time calculation is that specified in the FOC Handbook, February 1993, page 72, with the following assumptions: 1. E(B-V)=0.10 2. New optical element characteristics as in Table 3 of the FOC Handbook 3. Expected energy fraction on the assumed area of 21 pixel square (which consistently gave the shortest exposure time at a given S/N), as derived by linear interpolation of the data in Table 8 of the FOC Handbook 4. Detector background noise = 6.4E-4 counts/pixel/sec 5. Zodiacal light S10 = 3.0E-7 and 1.3E-7 for the two filters respectively, as estimated from Figure 41, assuming a zodiacal line intensity 120/90 S10 units 6. Zero astronomical background from the cluster or M31. The algorithm used for the S/N and exposure time calculations of the parallel observations is based on the procedure specified in the WFPC2 Handbook, March 1993, Sect. 6. We have used the quantities given in Tables 6.1, 6.2, 6.4, assuming readout noise rn=14e, and saturation threshold equal to 60000 cts in the central pixel. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The space resolution of ground-based observations is too poor to allow the photometry of individual HB stars in any globular cluster in M31 with the required accuracy. The very interesting data of the clusters G1 and G219 obtained with the CFHT in excellent seeing conditions for instance by Heasley et al. (1988, AJ 96, 1312) and Christian and Heasley (1991, AJ 101, 848) are still largely insufficient for the purpose of this program. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. In order to achieve the proposed scientific goals it is necessary to observe eventually a statistically significant number of clusters. Therefore the use of parallel observations with the WFPC2 to observe those clusters located at the appropriate projected distance from the FOC is very important to improve the program efficiency. One of our primary targets (G280) is associated with two parallel targets (G262 and G272) which both fall in the WFPC2 field of view if the Roll Angle is 181 +/- 3 deg (see Question 3). Although the need for the definition of the orientation makes the scheduling of the observations somewhat less flexible, we believe that the scientific return and the overall increase of efficiency of the program fully justify the proposed choice. The other primary target (G351) does not need any special orientation. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Our primary target G351 was already obseved by us during cycle 2 using FOC/96 + F342W and F140W in order to derive the surface brightness profile and test the possibility of detecting UV-bright stars. Stellar photometry was not feasible with the required accuracy due to the HST optical aberration. We intend to observe this cluster again now, since it is one of our high priority targets, in order to derive its color-magnitude diagram. Hence, this is not a duplication of previous science or observations. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Two GO programs were previously granted observing time, namely GO 2583 (cycle 1) and GO 3726 (cycle 2). With GO 2583 13 clusters were observed with FOC/96 + F430W and accurate surface brightness profiles were obtained, along with the related photometric and structural parameters. These results are of far superior quality than what can be obtained from ground-based observations of M31 globular clusters, and are comparable to the results on galactic globular clusters. The two cluster families show very similar characteristics. We have found the first evidence of a PCC cluster in M31. These results have been presented at the Workshop ``Science with the Hubble Space Telescope'' held in Baia Chia in July 1992 and in two papers published on ApJ and AA. With GO 3726 one cluster was observed with FOC/96 + F342W and F140W in order to explore the possibility of obtaining a UV C-M diagram of at least the brightest and hottest stars even in presence of the known HST aberration. The data reduction and analysis is presently being carried on, but it is evident that only the restored HST can provide useful results. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Data Analysis capabilities: Our Institute in Bologna is equipped with various Workstations (DEC) plus numerous peripherals specifically devoted to the analysis of HST data. Research assistance and students: there are typically 10 graduate students in Astronomy in Bologna, part of them already working on HST-related projects. Research assistance will be secured. Funds: our personal research grants are sufficient to cover all the expenses that may be required to carry on this HST project. The facilities of the ST-ECF are also available, if needed. American co-investigators will submit a separate request for funds. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: FLAVIO FUSI PECCI Category: PI Institution: 6426 Address: OSSERVATORIO ASTRONOMICO VIA ZAMBONI 33 City: BOLOGNA State: Zip Code: 40126 Country: ITALY Telephone: +39-51-259321 Telex (or e-mail): (SPAN) 37907::FLAVIO, fax:+39-51-259407 ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5420 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 G351 BO405 D,201 RA = 00H 49M 39.78S +/- 2000 1 V=15.16 +/- 0.1, B-V=0.72 0.1S, 2 V=25.0 +/- 0.1, TYPE=F0V, E(B- DEC = +41D 35' 29.4" +/- 1", V)=0.10 PLATE-ID = 01JV Comments: FLUX1= CLUSTER INTEGRATED V FOR ACQ ONLY FLUX2= HB STAR FOR TIME EXP. ------------------------------------------------------------------------------------------------------------------------------------ 2 G280 BO225 D,201 RA = 00H 44M 29.51S +/- 2000 1 V=14.26 +/- 0.1, B-V=0.92 0.1S, 2 V=25.0 +/- 0.1, TYPE=F0V, E(B- DEC = +41D 21' 35.48" +/- V)=0.10 1", PLATE-ID = 01JV Comments: FLUX1= CLUSTER INTEGRATED V FOR ACQ ONLY FLUX2= HB STAR FOR TIME EXP. ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST c)Generic Targets ID = 5420 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 7 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria |Acqui|FLX| Flux data No | Name | Description | |Prblm|REF| | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 5 G351-FIELD E,301,911 RA = 00H 49M 39.78S, 1 V=25.0 +/- 0.1, TYPE=F0V, E(B-V)=0.10 BO405-FIELD DEC = +41D 35' 29.42", R = 4.55' Comments: ANY PARALLEL WFPC2 FIELD WHEN, FOC/96 IS POINTING ON G351 ------------------------------------------------------------------------------------------------------------------------------------ 6 G272 E,301,911 RA = 00H 44M 14.27S, 1 V=14.83 +/- 0.1,TYPE=F0V, E(B-V)=0.10 BO218-FIELD DEC = +41D 19' 19.09", R = 4.55' Comments: PARALLEL WFPC2 FIELD WHEN FOC/96 IS ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5420 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 G351 FOC/96 IMAGE 512X512 F430W 1 3800S 10 2 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 G351 FOC/96 IMAGE 512X512 F480LP 1 10800S 10 2 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 3 G351-FIELD WFPC2 IMAGE WFALL- F555W 1 3800S 10 1 2 PAR FIX CYCLE 4 Comments: PARALLEL WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 G351-FIELD WFPC2 IMAGE WFALL- F814W 1 10800S 10 1 2 PAR FIX CYCLE 4 Comments: PARALLEL WITH 2 ------------------------------------------------------------------------------------------------------------------------------------ 5 G280 FOC/96 IMAGE 512X512 F430W 1 3800S 10 2 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 G280 FOC/96 IMAGE 512X512 F480LP 1 10800S 10 2 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 7 G272 WFPC2 IMAGE WFALL- F555W 1 3800S 10 1 2 PAR FIX CYCLE 4 Comments: PARALLEL WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 8 G272 WFPC2 IMAGE WFALL- F814W 1 10800S 10 1 2 PAR FIX CYCLE 4 Comments: PARALLEL WITH 6 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5420 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 10.42 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category DISTANCE SCALE ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 PAR; CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F430W F480LP F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names G351 BO405 G280 BO225 G351-FIELD BO405-FIELD G272 BO218-FIELD ------------------------------------------------------------------------------------------------------------------------------------