Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5303 Report Date: 18-Jul-95:17:07 Version: ********** Check-in Date: ********** 1.Proposal Title: CALIBRATION OF STELLAR EVOLUTIONARY AGES AND VARIATIONS IN THE IMF -- CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID COOL STARS GO Sub Category OLD CLUSTERS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Ted A Von hippel 8014 UNITED KIN 44-223-337516 ------------------------------------------------------------------------------------ 7. Abstract There are two related and fundamental aspects of star formation and evolution which are best studied in open clusters: comparison of the cooling age of white dwarfs with turnoff ages from stellar evolutionary models, and the universality of the Initial Mass Function. Photometry of nearby open clusters can determine the white dwarf luminosity function, and hence calibrate evolutionary and cooling age scales directly. The same observations determine the M dwarf luminosity function, and hence search for IMF variations. We propose here to do this experiment for 2 open clusters spanning a range of ages from approximately 1 to 3 Gyrs, as only the Hubble Space Telescope and WFPC2 is capable of acquiring the deep photometry required for the successful completion of this project. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 6.00 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5303 PI: Ted A Von hippel Proposal Title: CALIBRATION OF STELLAR EVOLUTIONARY AGES AND VARIATIONS IN THE IMF -- CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Ted A Von Hippel 8014 UNITED KING X Gerry F Gilmore 8014 UNITED KING X Derek H Jones 8070 UNITED KING X ------------------------------------------------------------------------------------ 3. Description of proposed observations. This project seeks to measure the luminosity of the faint end of the White Dwarf (WD) cooling sequence and to determine the Luminosity Function (LF) to approx. 0.18 solar masses in two open clusters. The faintest WDs are expected to be at approx. V = 24.5 (NGC 2477), and V = 25.6 (NGC 2420), while the 0.18 solar mass stars are expected to be at approx. V = 25.5 (both clusters). A S/N of >= 15 is sought for the photometry of all the WDs, and for the low mass stars. While the faintest WDs in NGC 2477 are approx. 1 mag. brighter than their counterparts in NGC 2420 a reduction in exposure time for this cluster would be counterproductive scientifically as the lowest mass stars would be missed in NGC 2477. Furthermore, the faintest WDs can be more readily identified in NGC 2477 by going significantly fainter than the WD faintness limit, proving that the entire WD cooling sequence has been identified. These brightness and S/N requirements yield cumulative exposures of 1 hour in each of our two filters, F555W and F814W, for each cluster. Since both these clusters contain many bright stars it is impossible to avoid saturating some parts of the WFPC2 CCDs. Care has been taken to choose cluster fields which avoid the brightest stars, but to further reduce the effect of saturation we request that the 1 hour exposures be broken into 9 x 400 second exposures for NGC 2477 and 4 x 900 second exposures for NGC 2420. To further lessen the effects of saturation we request that the optional parameter CLOCKS be set to YES and that the Gain be set to 15 e-/DN. The quality of the photometry would be enhanced, and the data reduction made easier, if each 3600 seconds of exposure (for a given filter and a given cluster) were at the same physical position on the sky, to the degree possible. Also, the relative positions of the F555W exposures to the F814W exposures, for a given cluster, should be approx. the same, to avoid the loss of objects measured in only one filter, though offsets of a few pixels between the filters is not important. Roll angle is important, however, and while any roll angle can be used for a given cluster we request that the same roll angle be maintained for all exposures in both filters for that cluster. Cosmic ray splits are not required since a number of exposures will be taken in each filter for both clusters. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. No special scheduling requirements. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. No special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Page 3 ------------------------------------------------------------------------------------ 11. Address Information Name: Ted A von Hippel Category: PI Institution: 8014 Address: Institute of Astronomy Madingley Road University of Cambridge City: Cambridge State: Zip Code: CB3 OHA Country: United Kingdom Telephone: 44-223-337516 Telex (or e-mail): ted@mail.ast.cam.ac.uk ------------------------------------------------------------------------------------ Name: Ted A von Hippel Category: CON Institution: 8014 Address: Institute of Astronomy Madingley Road University of Cambridge City: Cambridge State: Zip Code: CB3 OHA Country: United Kingdom Telephone: 44-223-337516 Telex (or e-mail): ted@mail.ast.cam.ac.uk ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5303 [ 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 NGC2420 C,202 RA = 7H 35M 13.3S +/- 1950.0 1 V = 25.6 +/- 0.2 0.01S, 1 B-V = 0.7 +/- 0.2 DEC = +21D 40' 00" +/- 0.1" 1 E(B-V) = 0.02 +/- 0.02 2 V = 25.5 +/- 0.2 2 V-I = 2.4 +/- 0.2 2 E(B-V) = 0.02 +/- 0.02 Comments: FLUXVALUES FOR A TYPICAL TARGET CLUSTER COOL WHITE DWARF (1) AND FOR A TYPICAL TARGET LOW MASS MAIN SEQUENCE STAR (2) FOR WHICH THE S/N IS ACHIEVED IN EXPO TIME. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC2477 C,202 RA = 7H 50M 30.1S +/- 1950.0 3 V = 24.5 +/- 0.2 0.01S, 3 B-V = 0.8 +/- 0.2 DEC = -38D 27' 52" +/- 0.1" 3 E(B-V) = 0.29 +/- 0.08 4 V = 25.5 +/- 0.2 4 V-I = 3.0 +/- 0.2 4 E(B-V) = 0.02 +/- 0.02 Comments: FLUXVALUES FOR A TYPICAL TARGET CLUSTER COOL WHITE DWARF (3) AND FOR A TYPICAL TARGET LOW MASS MAIN SEQUENCE STAR (4) FOR WHICH THE S/N IS ACHIEVED IN EXPO TIME. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5303 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC2420 WFPC2 IMAGE WFALL- F555W CR-SPLIT=NO 4 900S 15 1 1 CYCLE 4 FIX CLOCKS=NO 3600S 2 SAME ORIENT FOR ATD-GAIN=7 10.0 AS 11.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC2420 WFPC2 IMAGE WFALL- F814W CR-SPLIT=NO 4 900S 15 1 1 CYCLE 4 FIX CLOCKS=NO 3600S 2 SAME ORIENT FOR ATD-GAIN=7 11.0 AS 10.0 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC2477 WFPC2 IMAGE WFALL- F555W CR-SPLIT=NO 9 400S 15 3 1 CYCLE 4 FIX CLOCKS=NO 3600S 4 SAME ORIENT FOR ATD-GAIN=7 12.0 AS 13.0 ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC2477 WFPC2 IMAGE WFALL- F814W CR-SPLIT=NO 9 400S 15 3 1 CYCLE 4 FIX CLOCKS=NO 3600S 4 SAME ORIENT FOR ATD-GAIN=7 13.0 AS 12.0 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5303 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT CLOCKS ATD-GAIN ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 6.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COOL STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category OLD CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; SAME ORIENT FOR 10.0 AS 11.0 CYCLE 4; SAME ORIENT FOR 11.0 AS 10.0 CYCLE 4; SAME ORIENT FOR 12.0 AS 13.0 CYCLE 4; SAME ORIENT FOR 13.0 AS 12.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2420 NGC2477 ------------------------------------------------------------------------------------------------------------------------------------