6773( 14) - 03/03/97 10:49 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6773 Version: 14 Check-in Date: 03-Mar-1997 10:35:41 1.Proposal Title: The Butcher-Oemler Effect in Nearby Clusters of Galaxies ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle GALAXIES & CLUSTERS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: JAMES ROSE UNIV. OF NORTH CAROLINA CoI: Nelson Caldwell F.L.\\ Whipple Observatory, Smithsonian N Institution CoI: Richard Bower Department of Physics, University of N Durham CoI: Richard Ellis Institute of Astronomy, Cambridge N University CoI: Ray Sharples Department of Physics, University of N Durham ------------------------------------------------------------------------------------ 6. Abstract Recently we discovered a surprisingly large number of current starburst (SB) and post-starburst (PSB) early-type galaxies in three nearby clusters of galaxies, including the Coma cluster. The spectroscopic characteristics of these SB/PSB galaxies are remarkably similar to those found for the unusual galaxies in distant clusters. Thus we appear to be witnessing activity that is very similar in nature to the Butcher-Oemler (B-O) effect, but in clusters that are more than ten times nearer than the B-O clusters at z~0.3-0.5. The proximity of the clusters we are studying provides a unique opportunity to solve the principal questions concerning the origin of the B-O effect, such as what actually triggers the major star formation episodes in B-O cluster galaxies. In particular, we propose to acquire WFPC2 images of seven SB/PSB galaxies in the Coma cluster and in DC2048-52 to obtain high-resolution information on the central regions of these galaxies, where the star formation activity has been the most intense. ------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 2] Observations Description ------------------------ The observations will help define the morphologies of the inner regions of these early-type galaxies, all of which are classified S0 from ground based images. We have selected five post-starburst galaxies from the two clusters and two certain starburst galaxies. Images for this sample should be definitive in the properties of such galaxies. The data in particular should be useful to identify possible massive star clusters formed during the bursts. Such clusters as are found in NGC 7252 and NGC 1275 (Holtmann et al. and Whitmore et al.) have a mean M_V=--13. In Coma, such clusters would thus appear at V=23, about 2.5 mags brighter than the brightest normal globular clusters. A decrease in the luminosity with age is expected of course, but the starbursts in the Coma PSB galaxies have been dated to around 1 Gyr, which is similar to the ages found for the NGC 7252 clusters. So the comparison in luminosities is apt. Their relatively bright apparent magnitudes don't make their detection easy from the ground, because they are expected to be located in the high surface brightness regions of the bulge, where because of crowding and the high background their detection requires HST (as Holtzman et al. and Whitmore et al. found for their galaxies). The WFPC2 exposure time calculator indicates that an exposure time of 1000s for the PC chip in F450W will give a S/N of about 10 at V=25. Taking into account the noise added by the presence of the galaxy, we estimate that the S/N would be about 7 for the stated parameters, sufficient certainly to detect clusters and measure them. The F450W filter is chosen to maximize the throughput and sensitivity to young ages, while the F814W filter was chosen to provide a red baseline for the measurement of colors (F555W overlaps with F450W and hence is not ideal for this work). Color gradients in the diffuse light distribution will be used to map out the location of the star bursts. As mentioned above, from ground based data it appears that the starbursts were wide-spread but centrally concentrated. What we don't know is whether the nucleus itself was the main site of the starburst. HST data will clarify that issue. At the declination of the Coma cluster, 53 minutes of visibility per orbit are available. Counting overhead with CR-SPLIT, we can thus obtain one 1000s F450W exposure and one 700s F814W exposure per orbit. Thus one orbit per galaxy should suffice, for a total of 4 orbits. There are an additional 3 minutes of time available for the DC2048-52 galaxies, which will be added into the two filters. The net result is still one orbit per galaxy, so the overall total will be 7 orbits requested. Real Time Justification ----------------------- none We are engaged in further ground based observations to further define the frequency and location of SB/PSB galaxies in nearby clusters, by obtaining multi-fiber spectroscopy with large telescopes. Followup up work on identified galaxies is planned to age-date the starbursts, study unusual kinematics, and look for unusual morphologies that may be indicative of the origin of the starbursts. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: ------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 COMA-D45 GALAXY, Lenticular, RA=12H 57M 56.25S +/-0.3", J2000 SURF(V) = 24.0+/-0.5 CLUSTER OF GALAXIES, DEC=27D 34' 52.25" +/-0.3" B-V = 0.85 Rich Cluster 2 COMA-D15 GALAXY, Lenticular, RA=12H 57M 25.32S +/-0.3", J2000 SURF(V) = 24.0+/-0.5 CLUSTER OF GALAXIES, DEC=27D 24' 15.86" +/-0.3" B-V = 0.85 Rich Cluster 3 COMA-D99 GALAXY, Lenticular, RA=13H 00M 09.7S +/-0.3", J2000 SURF(V) = 24.0+/-0.5 CLUSTER OF GALAXIES, DEC=27D 51' 52.10" +/-0.3" B-V = 0.85 Rich Cluster 4 COMA-D61 GALAXY, Lenticular, RA=13H 02M 0.10S +/-0.3", J2000 SURF(V) = 17.0+/-0.5 CLUSTER OF GALAXIES, DEC=27D 46' 56.40" +/-0.3" B-V = 0.85 Rich Cluster Comments: New target selected by PI as D94 has a high chance of gs failure 5 DC2048-D148 GALAXY, Lenticular, RA=20H 49M 13.63S +/-0.3", DEC=- J2000 SURF(V) = 20.0+/-0.5 CLUSTER OF GALAXIES, 52D 33' 51.40" +/-0.3" B-V = 0.90 Rich Cluster 6 DC2048-D192 GALAXY, Lenticular, RA=20H 51M 56.3S +/-0.3", DEC=- J2000 SURF(V) = 20.0+/-0.5 CLUSTER OF GALAXIES, 52D 03' 45.4" +/-0.3" B-V = 0.90 Rich Cluster 7 DC2048-D216 GALAXY, Lenticular, RA=20H 49M 24.51S +/-0.3", DEC=- J2000 SURF(V) = 20.0+/-0.5 CLUSTER OF GALAXIES, 51D 56' 54.5" +/-0.3" B-V = 0.90 Rich Cluster 6773( 14) - 03/03/97 10:49 - [ 5] Visit: 01 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 COMA-D45 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 2 COMA-D45 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 6] Visit: 02 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 COMA-D15 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 2 COMA-D15 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 7] Visit: 03 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 COMA-D61 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 2 COMA-D61 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 8] Visit: 04 Visit Requirements: On Hold Comments: Additional Comments: 180 orientation switch ok (i.e., to 280D < angle < 320D) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 COMA-D99 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 2 COMA-D99 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 9] Visit: 05 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DC2048-D148 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 DC2048-D148 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 10] Visit: 06 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DC2048-D192 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 DC2048-D192 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 11] Visit: 07 Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DC2048-D216 WFPC2 IMAGE PC1 F450W 4519 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 DC2048-D216 WFPC2 IMAGE PC1 F814W 7921 CR-SPLIT=0.5,CR-TOLERANCE=0.0 1 800 S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6773( 14) - 03/03/97 10:49 - [ 12] Summary Form for Proposal 6773 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.5 CR-TOLERANCE=0.0 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F450W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names COMA-D45 COMA-D15 COMA-D61 COMA-D99 DC2048-D148 DC2048-D192 DC2048-D216 ------------------------------------------------------------------------------------------------------------------------------------