Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3726c Report Date: 09-May-96:18:48 Version: ********** Check-in Date: ********** 1.Proposal Title: GLOBULAR CLUSTERS IN M31 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR POPULATIONS GO Sub Category GLOBULAR CLUSTERS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Prof. Flavio Fusi pecci BOLOGNA OBSERVATORY ITALY +39-51-259321 PROFESSOR ------------------------------------------------------------------------------------ 7. Abstract The original aim of this proposal was to observe 27 globular clusters in M31 using FOC/96 over a period of three years with the following scientific rationale: a) during cycle 2 and 3, B and UV images in order to obtain surface brightness profiles and blue upper parts of CMDs (e.g. Post-AGB and blue HB stars). This is essential for understanding the dynamical properties of the clusters and the galaxy, and the stellar population characteristics also in comparison with other LG galaxies (MW, MCs). 13 clusters are planned to be observed in cycle 1 in B and surface brightness profiles have been obtained. b) On the assumption that in cycle 4 HST is restored to its original optical performance, we proposed to observe 10 top-priority clusters using B and V filters, in order to obtain accurate (0.1 mag) CMDs down to the HB level. This would allow to derive the slope of the HB luminosity vs metallicity relation, a key ingredient in globular cluster distance and age determinations, with well known cosmological implications. Within this framework, the TAC has recommended that the time allocated to this proposal (2.5hrs) be used to observe one cluster in two filters during cycle 2, in order to test the feasibility and obtain the blue upper part of the CMD (i.e. UV-bright, Post-AGB and blue HB stars). ------------------------------------------------------------------------------------ 8. Scientific Key Words: EXT-CLUSTER ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.50 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3726c PI: Prof. Flavio Fusi pecci Proposal Title: GLOBULAR CLUSTERS IN M31 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Flavio Fusi Pecci BOLOGNA OBSERVATORY ITALY X Pierluigi Battistini UNIVERSITY OF BOLOGNA ITALY X Orazio Bendinelli UNIVERSITY OF BOLOGNA ITALY X Fabrizio Bonoli UNIVERSITY OF BOLOGNA ITALY X Carla Cacciari BOLOGNA OBSERVATORY ITALY X Luciana Federici BOLOGNA OBSERVATORY ITALY X Gianluigi Parmeggiani BOLOGNA OBSERVATORY ITALY X Franco Zavatti UNIVERSITY OF BOLOGNA ITALY X Roberto Buonanno ROMA OBSERVATORY ITALY X Ivan R. King UNIVERSITY OF CALIFORNIA, USA BERKELEY Rene' Walterbos NEW MEXICO STATE UNIVERSITY USA George S. Djorgovski CALTECH USA ------------------------------------------------------------------------------------ 2. Scientific Justification. ------------------------------------------------------------------------------------ 3. Description of proposed observations. Target: G351 (globular clusters in M31) Distance modulus (m-M)v = 24.4 Total integrated apparent magnitude of the cluster: V = 15.18 Integrated colour: B-V = 0.72 Angular size: 8 arcsec Reddening: E(B-V) = 0.10 + contribution within M31 (small) Proposed observations: FOC/96 with F342W and F140W (one exposure in each filter) The exposure times have been calculated in order to obtain approximately S/N=7 for a typical Post-AGB star with T=30,000K and logL/Lo=3.1, such as vZ1128 in M3, and S/N= 7-9 for a UV-bright star with T=22,500K and logL/Lo=3.1 such as K559 in M15. Fainter UV-bright stars will also be detectable, although with a lower S/N. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Even in its present degraded optical situation, HST still has capabilities that are unmatched by ground-based instruments, namely the spatial resolution and the possibility of observing in the UV range. Post-AGB and Hot HB stars can efficiently be observed only in the UV range, and because the crowding is not severe in this wavelength range they can easily be detected and measured with a good degree of photometric accuracy. Observations in the U filter allow the construction of a CMD, which provides information on the hot stellar population of the cluster. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. For the data reduction a good knowledge of the PSF is important in order to obtain as accurate as possible photometric information on individual stars. Given the very limited amount of time granted to the program, however, we plan to use the PSFs available in the library either from theoretical models or from previous standard calibration observations. Page 3 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Data reduction and analysis will be performed mainly: a) in Rome as far as the properties of individual stars are concerned, and b) in Bologna for features of the integrated surface brightness. We also expect to spend a significant amount of time (1-2 months) at the STScI and/or ST-ECF for getting acquainted with particular aspects/problems, especially during the initial phase of data reduction. To achieve the goals of a), we have already started checks and simulations using both synthetic and HST-SV images and the photometric package ROMAFOT (Buonanno et al. 1983, integrated with some routines by Bendinelli et al.), which has been recently optimized for HST image reduction taking into account both PSF features and problems related to sampling and flat-fielding. Star photometry will also be performed using the Malumuth technique which exploits the bright small cores of HST images to achieve better star separation near the cluster centers. REFERENCES Buonanno,R., Buscema,G., Corsi.C.E., Ferraro,I., Iannicola,G.,1983, Astron. Astrophys. 126, 278 Malumuth, E.M., Neill,J.D., Lindler,D.J., Heap,S.R., 1990, B.A.A.S. 22, 1276 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. We plan to measure accurate target positions using GASP frames. This can be done at ST-ECF, as it was done in previous occasions. ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO Program 2583: Surface Photometry of a Sample of Globular Clusters in M31. This program is strictly related to the present project. Only part of the observations have been taken at the present time. The data are extremely good for the purpose of deriving surface photometry, and the preliminary reduction shows excellent surface brightness profiles. The results will be presented at the forthcoming HST Workshop in Baia Chia (Sardinia, Italy, June-July 1992), and a paper is in preparation. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computing: Bologna: one VAX 8530, one VAX 8800, 3 Microvaxes, 3 DEC 3100 Workstations, 3Gby mass memory, one Gould-DeAnza image processor, one Microvax GPX workstation, in addition to numerous peripherals. Access to the Cray2 of the Bologna University is also available. Rome: 4 Microvaxes and numerous peripherals. Berkeley: private MicrovaxGPX with 8 Mby + 210 Mby disk, VAX 200 workstation Caltech: Several VAX-class computers, including one private Microvax GPX. One Convex C-1. NMSU (Las Cruces): private Sun Sparc 1+ station with peripherals. Access to the 3.5-m Apache Point Observatory. The facilities of the ST-ECF are also available, if needed. Research Assistants and Students: there are typically 10 graduate students in Astronomy in Bologna, part of which already working on HST-related projects. Research assistance will be secured. Funds: our personal Research Grants are sufficient to cover all the expenses conceivably required to complete this project. A separate request for funding will be submitted by our U.S. co-investigators. ------------------------------------------------------------------------------------ 11. Address Information Name: FLAVIO FUSI PECCI Category: PI Institution: BOLOGNA OBSERVATORY Address: VIA ZAMBONI 33 City: BOLOGNA State: Zip Code: 40126 Country: ITALY Telephone: +39-51-259321 Telex (or e-mail): 520634 INFNBO I ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 3726c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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=15.18 +/- 0.1, B-V=0.72 0.3", 2 F(1360)=26 +/- 1 E-18 DEC = +41D 35' 29.4" +/- 3 F(3360)=24 +/- 1 E-19 0.3", PLATE-ID = 01JV Comments: FLUX1= CLUSTER INTEGR. V FOR ACQ ONLY FLUX2,3 REFER TO PAGB STAR B=24.0, B-V=- 0.40 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3726c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 F342W 1 1680S 7 3 1 CYCLE 2 ------------------------------------------------------------------------------------------------------------------------------------ 2 G351 FOC/96 IMAGE 512X512 F140W 1 4560S 7 2 1 CYCLE 2 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3726c [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.50 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category GLOBULAR CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F342W F140W ------------------------------------------------------------------------------------------------------------------------------------ Target Names G351 BO405 ------------------------------------------------------------------------------------------------------------------------------------