8668( 3) - 05/22/00 13:11 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8668 Version: 3 Check-in Date: 22-May-2000 13:10:34 1.Proposal Title: Spectroscopy of candidate, very massive, intermediate age globular clusters in ESO 338-IG04 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Goeran Oestlin Stockholm University CoI: Dr. Marcella Longhetti Institut d'Astrophysique de Paris N CoI: Ass.Prof. Nils Bergvall Uppsala Astronomical Observatory N CoI: Mr. Arnaud Pharasyn Uppsala Astronomical Observatory N CoI: Mr. Torgny Karlsson Uppsala Astronomical Observatory N CoI: Dr. Ariane Lancon Observatoire Astronomique de Strasbourg N CoI: Mr. Mustapha Mouchine Observatoire Astronomique de Strasbourg N ------------------------------------------------------------------------------------ 5. Abstract The blue compact starbursting galaxy ESO 338-IG04 has been found to be very rich in globular clusters (GCs) of varying age, from a few Myr to 10 Gyr. Among low mass galaxies, it appears to be an extraordinary efficient GC factory, and its GC richness is fully comparable to those of giant ellipticals. An important GC formation event occured some 2.5 Gyrs ago. In this age category we find cluster no. \#34, an unusually massive cluster with \cal M 10^7 \cal M_\odot. Here, we propose to observe this cluster, and two other intermediate age massive GC candidates. The aim is to derive ages, metallicities and internal extinction, in a self consistent way. This will provide a test on the origin and chemical evolution of the host galaxy, and a possibilty to assess the reliability of photometrically derived ages and masses for young GC candidates in general. The latter point is important, because GCs, beeing fossil starbursts, may be used to probe the starburst history of galaxies in the universe. Also, beeing true single stellar populations, massive (where number of stars are large and statisical fluctuations small) GCs provide important tests for stellar evolution models. ------------------------------------------------------------------------------------ 8668( 3) - 05/22/00 13:11 - [ 2] Observations Description ------------------------ The main target of interest, GC \#34 in the outer sample have the following magnitudes in the Vegamag system m_f814w=19.3, m_f555w=20.2, m_f439w=20.7, m_f336w=20.9. We aim at a formal signal to noise (S/N) of 20 per resoultion element at 4000 Angstrom \ and 7000 Angstrom (before background subtraction). With the use of the 52X0.1 slit total exposure times of 7600s would be required for the blue part (G430L) and 4000s for the red part. In addition a second (and likely a third) luminous cluster will be observed through the same slit. For example, a slit angle of 12 degrees (from N to E) would allow also clusters no. \#43 and \#44 in the inner sample to be observed at the ame time. These have estimated ages of 400 and 60 Myr respectively, and masses ~ 2 * 10^6 \cal M_\odot. The final choise may be subject to the orientation constraints which are not known at this moment but there are several interesting candidates with m_f555w~ 21 for which S/N = 10 can be achieved. The exposures will be split in 900s- 1200s long subexposures. The STIS is also a very sensitive instrument for imaging. With a short 300 seconds (CR-split) image in clear imaging mode we can reach 2 magnitudes deeper than previous WFPC2 observations and reach below m_V = 26 with a S/N of 5. In total, including overheads, the proposed observations would require 5 orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8668( 3) - 05/22/00 13:11 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 OFFSET-STAR STAR RA=19H 27M 57.2577S +/- 0.5", J2000 V = 13.5+/-0.5 DEC=-41D 34' 34.533" +/- 0.5", PLATE-ID=01IA Coordinate Source: HST_IMAGE 3 IRAS19245- EXT-CLUSTER, GLOBULAR RA-OFF=0.7488S+/- 0.0012S, DEC- J2000 Z = V = 20.2 4140-GC43 CLUSTER, GALAXY, DWARF OFF=1.079"+/- 0.005", FROM 2, 0.0097 SURF-BKG(V) = 20.7 COMPACT, STARBURST PLATE-ID=01IA B-V = 0.54 E(B-V) = 0.1 TYPE=F6V Coordinate Source: HST_IMAGE 8668( 3) - 05/22/00 13:11 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 1.0142 Coordinate_Frame POS-TARG Pattern_Orient 90 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 8668( 3) - 05/22/00 13:11 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 346.06D TO 346.22D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 3 OFFSET-STAR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.3 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 5 IRAS19245-4 STIS/C ACQ/PEA 52X0.1 MIRROR 1 40 S 140-GC43 CD K ------------------------------------------------------------------------------------------------------------------------------------ 60 IRAS19245-4 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=2 1 1750 S 140-GC43 CD ------------------------------------------------------------------------------------------------------------------------------------ 65 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 70 IRAS19245-4 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=5 1 4800 S PATTERN 1 70 140-GC43 CD ------------------------------------------------------------------------------------------------------------------------------------ 75 IRAS19245-4 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=NO 1 900 S 140-GC43 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 IRAS19245-4 STIS/C ACCUM F28X50O MIRROR 1 300 S 140-GC43 CD III ------------------------------------------------------------------------------------------------------------------------------------ 90 IRAS19245-4 STIS/C ACCUM 50CCD MIRROR 1 150 S 140-GC43 CD ------------------------------------------------------------------------------------------------------------------------------------ 100 IRAS19245-4 STIS/C ACCUM 50CCD MIRROR 1 150 S POS TARG 0.53246, 0.53246 140-GC43 CD Comments: Offset 10.5 pixels in X and Y ------------------------------------------------------------------------------------------------------------------------------------ 8668( 3) - 05/22/00 13:11 - [ 6] Summary Form for Proposal 8668 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 F28X50OIII 50CCD ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT CR-SPLIT=2 CR-SPLIT=5 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 346.06D TO 346.22D PATTERN 1 70 POS TARG 0.53246, 0.53246 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750L G430L ------------------------------------------------------------------------------------------------------------------------------------ Target Names OFFSET-STAR IRAS19245-4140-GC43 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 7751 4300 ------------------------------------------------------------------------------------------------------------------------------------