7859( 8) - 06/10/98 11:49 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7859 Version: 8 Check-in Date: 10-Jun-1998 11:46:27 1.Proposal Title: Blue Compact Dwarf Galaxies -- young or old? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Regina E. Schulte-Ladbeck UNIVERSITY OF PITTSBURGH CoI: Dr. Mary Crone Skidmore College N CoI: Dr. Ulrich Hopp Universitddota tssternwarte Mddotu nchen N ------------------------------------------------------------------------------------ 5. Abstract Blue Compact Dwarf Galaxies (BCDs) challenge models of galaxy formation to explain the presence of small, low-metallicity galaxies experiencing vigorous bursts of star formation. Are BCDs examples of modern-day galaxy formation? Are they related to the mysterious faint blue excess? Crucial in distinguishing models is the age of the oldest stars in BCDs. Previous ground-based data, lacking spatial resolution, have failed to detect individual old stars in BCDs. Previous HST observations have focussed on extreme objects such as I Zw 18, too distant for even HST to resolve all but luminous star clusters and a few of the most massive young stars. With this proposal we demonstrate that HST CAN RESOLVE in THE MOST NEARBY BCDs stars with ages of a large fraction of the Hubble time. We propose to take advantage of the unique capabilities of high spatial resolution and IR-sensitivity of NICMOS to search for old stellar populations in 5 BCDs, a small but representative sample covering the range of properties found in BCDs. NIC2 J, J-H color-magnitude diagrams will be used to find the tip of the red giant branch, which we show is well above the detection limit, and which is an indicator for stars with ages > 7 Gyrs. Furthermore, the magnitude of the tip of the red giant branch will provide the best current distances to these nearby BCDs, allowing improved modelling of velocity flows and dark matter in the local universe. ------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 2] Observations Description ------------------------ For a central pointing with the NIC2 within the body of one of the target galaxies, the NIC1 will also point somewhere within ``Baade's sheet" of that galaxy, and so we request it as an internal parallel. We declared the NIC2 our primary camera. When NIC2 is focussed, the NIC1 is only slightly degraded, which we considered the best focussing option (rather than having the NIC1 in perfect focus and the NIC2, which has the lower resolution of the two, degraded further). Exposure times were calculated using the WWW NICMOS exposure time calculator, for point-source mode, with absolute magnitude and colors appropriate for a metal-poor RGB star, to be observed at a S/N of 10 in J and H. Our conclusion is that the scientific goal can be achieved with one orbit in J and two orbits in H, per galaxy. With five galaxies in the sample, this led to our request for 15 orbits. What are the chances that the distances are wrong and the red giants will remain below the detection limit in all but VII Zw 403? The unknown distances are clearly a risk factor of this proposal. The distance we derived for VII Zw 403 is about 45\% larger than that listed in the Kunth & Sevre catalog. Now, if we assume that the most distant galaxy in our sample, NGC 4214, has a similar distance error than it would be at 9.3 Mpc, still significantly closer than I Zw 18. In addition, we have previously resolved UGC 5272 from the ground, UGC 6541 was resolved by Georgiev (1996), NGC 4214 was resolved with the HST/FOC by Leitherer et al. Therefore, distance errors shold not be a large concern when assesing the probability of success for this proposal. Is it necessary to observe 5 galaxies? Having found an old population in VII Zw 403, should we look for it in other galaxies or should we simply claim its existence in all BCDs? We think that we should continue to investigate the presence of old populations in other BCDs. VII Zw 403 might turn out to be ``special", perhaps having had a merger history. It clearly is not representative for the whole spectrum of properties observed in BCDs. The galaxies we propose to observe have, in particular, metallicities which cover very well the maximum in the metallicity distribution of BCDs in the SBS sample (the recent large survey of BCDs, see Thuan et al. 1994, Fig. 5). There is a sharp rise in the numbers of BCDs with O/H larger than 7.7, and a sharp drop for values larger than 8.3. We are sampling this inverval in metallicity, but not any galaxies with very high, or extemely low metallicities. At the same time, the galaxies so selected represent all BCDs which are also closer than 10 Mpc, so that we can hope to be able to resolve them with HST/NICMOS. Given the unique situation that the NICMOS instrument find itself in, this might be our only opportunity to investigate old populations in a few BCDs. Finally, observing a sample offsets the risk that although resolved, the CMDs of one or two galaxies might not be deep enough to reach the RGB. Will this proposal provide the definitive answer to the question it poses? Even if we detect old stellar populations in all of the sample galaxies, one might argue that if extreme candidates such as I Zw 18 or SBS 0335-052 were observed, they wouldn't show it. There is nothing HST can do to refute this argmument. We have already shown that the detection of red giants in I Zw 18 with HST/NICMOS will depend crucially on small, favorable errors in the distance modulus. The investigation of the old stellar populations in objects such as I Zw 18 and SBS 0335-052 will remain a problem for the NGST to tackle. Real Time Justification ----------------------- Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UGC6456 GALAXY, Dwarf Compact RA=11H 28M 00.6 S +/- 0.1S, 2000 B = 14.7 DEC=78D 59' 27.5"+/- 0.5" Comments: POS=Center of HII-region from WFPC2 observation 2 UGC5272 GALAXY, Dwarf Compact RA=09H 50M 21.29 S +/- 0.03S, 2000 B = 14.7 DEC=31D 29' 15.38"+/- 0.3" Comments: POS=Center of 2nd brightest HII-region, located centrally in galaxy 3 UGC6541 GALAXY, Dwarf Compact RA=11H 33M 28.82 S +/- 0.03S, 2000 B = 13.9 DEC=49D 14' 12.37"+/- 0.3" Comments: POS=Center of brightest HII-region, located off center of galaxy, a second, fainter HII-region should also fall onto NIC2. 4 NGC4214 GALAXY, Dwarf Compact RA=12H 15M 41.02 S +/- 0.03S, 2000 B = 12.7 DEC=36D 19' 03.75"+/- 0.3" Comments: POS=Center of brightest HII-region, located off galaxy center 5 UGCA281 GALAXY, Dwarf Compact RA=12H 26M 15.76 S +/- 0.03S, 2000 B = 15.3 DEC=48D 29' 36.67"+/- 0.3" Comments: POS=Center of brightest HII-region, located off galaxy center 7859( 8) - 06/10/98 11:49 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Read the strategy comments in template after first exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 UGC6456 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 2-3 WITH 1 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=18 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=18 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=18 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 4 UGC6456 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 5-6 WITH 4 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7 UGC6456 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 8-9 WITH 7 CUM PATTERN=XSTRIP-DITH,NUM-POS=5, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 8 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 9 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Read strategy comments in template after first exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 UGC5272 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 11-12 WITH 10 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 11 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 12 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 13 UGC5272 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 14-15 WITH 13 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 15 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 16 UGC5272 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 17-18 WITH 16 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 17 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 18 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 7] Visit: 03 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Read strategy comments in template after first exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 19 UGC6541 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 20-21 WITH 19 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 20 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 21 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 22 UGC6541 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 23-24 WITH 22 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=17 ------------------------------------------------------------------------------------------------------------------------------------ 23 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 24 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 25 UGC6541 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 26-27 WITH 25 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=17 ------------------------------------------------------------------------------------------------------------------------------------ 26 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 27 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 8] Visit: 04 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Read strategy comments in template after first exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 28 NGC4214 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 29-30 WITH 28 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 29 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 30 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC4214 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 32-33 WITH 31 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 32 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 33 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 34 NGC4214 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 35-36 WITH 34 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 35 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 36 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 9] Visit: 05 Visit Priority: Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Read strategy comments in template after first exposure. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 37 UGCA281 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 38-39 WITH 37 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=16 ------------------------------------------------------------------------------------------------------------------------------------ 38 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 39 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=16 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 40 UGCA281 NIC2 MULTIAC NIC2 F110W CAMERA-FOCUS=DEF, 1 DEF PARallel 41-42 WITH 40 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=17 ------------------------------------------------------------------------------------------------------------------------------------ 41 ANY NIC1 MULTIAC NIC1 F110W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 42 ANY NIC3 MULTIAC NIC3 F110W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 43 UGCA281 NIC2 MULTIAC NIC2 F160W CAMERA-FOCUS=DEF, 1 DEF PARallel 44-45 WITH 43 CUM PATTERN=XSTRIP-DITH,NUM-POS=3, DITH-SIZE=1.0,SAMP-SEQ=SPARS64, NSAMP=17 ------------------------------------------------------------------------------------------------------------------------------------ 44 ANY NIC1 MULTIAC NIC1 F160W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 45 ANY NIC3 MULTIAC NIC3 F160W SAMP-SEQ=SPARS64,NSAMP=17 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 7859( 8) - 06/10/98 11:49 - [ 10] Summary Form for Proposal 7859 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures NIC2 NIC1 NIC3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC2 NIC1 NIC3 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CAMERA-FOCUS=DEF PATTERN=XSTRIP-DITH NUM-POS=3 DITH-SIZE=1.0 SAMP-SEQ=SPARS64 NSAMP=18 NSAMP=14 NUM-POS=5 NSAMP=16 NSAMP=17 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F PARallel 2-3 WITH 1 PARallel 5-6 WITH 4 PARallel 8-9 WITH 7 PARallel 11-12 WITH 10 PARallel 14-15 WITH 13 PARallel 17-18 WITH 16 PARallel 20-21 WITH 19 PARallel 23-24 WITH 22 PARallel 26-27 WITH 25 PARallel 29-30 WITH 28 PARallel 32-33 WITH 31 PARallel 35-36 WITH 34 PARallel 38-39 WITH 37 PARallel 41-42 WITH 40 PARallel 44-45 WITH 43 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names UGC6456 ANY UGC5272 UGC6541 NGC4214 UGCA281 ------------------------------------------------------------------------------------------------------------------------------------