8337( 3) - 02/16/99 13:34 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8337 Version: 3 Check-in Date: 16-Feb-1999 13:33:36 1.Proposal Title: Red Giants, Planetary Nebulae, and the Properties of Virgo's Intracluster Stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Robin Ciardullo Pennsylvania State University CoI: Mr. John Feldmeier The Pennsylvania State University N CoI: Dr. George Jacoby National Optical Astronomy Observatories N CoI: Dr. Abi Saha National Optical Astronomy Observatories N ------------------------------------------------------------------------------------ 5. Abstract Intracluster starlight can be a powerful probe of the structure and evolutionary state of galaxy clusters. Recently, this field of study has been revolutionized by the ground-based discovery of intracluster planetary nebulae (IPN) in the Virgo and Fornax Clusters, and by the detection of Virgo's intracluster red giants (IRG) by HST. These two measurements should complement each other: ground-based IPN surveys can map out the distribution and kinematics of the intracluster stars, while HST IRG measurements at specific locations in the cluster can provide details about the stellar population and normalize the IPN data. Unfortunately, the IPN and the IRG observations to date are not complementary. The distribution of intracluster stars in Virgo is clumpy, and the HST IRG field has the misfortune to be located in a region of very low stellar density. Since very few IPN are located in the field, we cannot compare their luminosity function to that of the red giants. We pro po se to use the Hubble Space Telescope to detect IRG stars in regions of the Virgo cluster where the stellar density is high and the IPN luminosity function is well defined. These observations will allow us to calibrate IPN measurements in the rest of the cluster, independently confirm the Virgo Cluster morphology, and place new constraints on the parent populations of the intracluster stars. ------------------------------------------------------------------------------------ 8337( 3) - 02/16/99 13:34 - [ 2] Observations Description ------------------------ We propose to observe one WFPC fields in the Virgo Cluster using the F814W (I) filter to search for intracluster red giant stars. (The approximate V magnitude in the proposal header is given only for completeness.) From the absolute magnitude of the tip of the red giant branch (M_I = -4.2 +/- 0.1), and the approximate distance modulus of Virgo (Mu_0 ~ 31.0), we expect the red giant branch tip to appear at approximately I = 26.8, in agreement with the earlier observations of Ferguson, Tanvir & von Hippel (1998) and Harris Etal (1998). To sample a significant number of these stars, we need to observe at least a magnitude down the red giant branch. Therefore, we need to reach an I$ magnitude of ~ 28.0. Entering these requirements into the WFPC2 Exposure Time Calculator, we find that we need 32, 300 seconds of exposure for our first field. Given the declination of our targets, and after accounting for instrumental overhead, a total of 13 orbits is required for the first field . Obviously, we do not know beforehand the exact number of intracluster red giants we will detect in each field. The observations of Ferguson, Tanvir & von Hippel (1998) found ~ 630 excess sources in their HST field (relative to counts in the Hubble Deep Field) with the major source of error on their measurement (+/- 80) being from the fluctuation of background galaxy counts. From our planetary nebula observations, we expect at least a factor of ~ 10 more stars. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8337( 3) - 02/16/99 13:34 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 VIRGO-CLUS2 CLUSTER OF GALAXIES, RA=12H 28M 15.8S +/- 1S, DEC=12D J2000 I = 28.0+/-0.5 POOR CLUSTER, HALO, 41' 22" +/- 1" BLANK SKY, EXT-STAR, K III-I, CARBON STAR, M Comments: BLANK FIELD IN THE VIRGO CLUSTER - NEAR ISOPLETH CENTER OF SUBCLUMP "A" (SEE BINGGELLI, SANDAGE, & TAMMANN 1987 FOR SUBCLUMP DEFINITIONS) 8337( 3) - 02/16/99 13:34 - [ 4] Visit: 01 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 110 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 40 M LOW-SKY EXPAND MAX DUR 60 IX M ------------------------------------------------------------------------------------------------------------------------------------ 120 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M LOW-SKY EXPAND MAX DUR 60 IX M ------------------------------------------------------------------------------------------------------------------------------------ 130 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M LOW-SKY EXPAND MAX DUR 60 IX M ------------------------------------------------------------------------------------------------------------------------------------ 140 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M LOW-SKY EXPAND MAX DUR 60 IX M ------------------------------------------------------------------------------------------------------------------------------------ 150 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M LOW-SKY EXPAND MAX DUR 60 IX M ------------------------------------------------------------------------------------------------------------------------------------ 8337( 3) - 02/16/99 13:34 - [ 5] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 210 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 40 M EXPAND LOW-SKY MAX DUR 60 IX M POS TARG 0.233, 0.233 ------------------------------------------------------------------------------------------------------------------------------------ 220 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND LOW-SKY POS TARG IX 0.233, 0.233 MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ 230 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND LOW-SKY MAX DUR 60 IX M POS TARG 0.233, 0.233 ------------------------------------------------------------------------------------------------------------------------------------ 240 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND LOW-SKY MAX DUR 60 IX M POS TARG 0.233, 0.233 ------------------------------------------------------------------------------------------------------------------------------------ 8337( 3) - 02/16/99 13:34 - [ 6] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 310 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 40 M EXPAND POS TARG -.233, IX -.233 LOW-SKY MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ 320 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND POS TARG -.233, IX -.233 LOW-SKY MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ 330 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND POS TARG -.233, IX -.233 LOW-SKY MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ 340 VIRGO-CLUS2 WFPC2 IMAGE WFALL-F F814W CR-SPLIT=0.0 1 42 M EXPAND POS TARG -.233, IX -.233 LOW-SKY MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ 8337( 3) - 02/16/99 13:34 - [ 7] Summary Form for Proposal 8337 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFALL-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.0 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements LOW-SKY EXPAND MAX DUR 60 M SAME ORIENT AS 01 EXPAND LOW-SKY MAX DUR 60 M POS TARG 0.233, 0.233 EXPAND LOW-SKY POS TARG 0.233, 0.233 MAX DUR 60 M EXPAND POS TARG -.233,-.233 LOW-SKY MAX DUR 60 M ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names VIRGO-CLUS2 ------------------------------------------------------------------------------------------------------------------------------------