6092( 8) - 11/15/95 17:31 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6092 Version: 8 Check-in Date: ********** 1.Proposal Title: Disk Globular Clusters in Edge-On Spiral Galaxies ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Keith Ashman University of Kansas CoI: Stephen Zepf University of California, Berkeley N CoI: Kenneth Freeman Mount Stromlo & Siding Springs Observatory N ------------------------------------------------------------------------------------ 6. Abstract The role of interactions and mergers in the formation and evolution of galaxies is controversial. However, evidence is growing that galaxy morphology is determined to some extent by mergers. In this proposal we address the specific question of the origin of the thick disk component of spiral galaxies. By searching two nearby edge- on spirals for the presence of disk globular clusters we will be able to constrain formation models for thick disks. With only modest exposure times we will test the hypothesis that the thick disks of spiral galaxies are formed by the accretion of one or more satellite galaxies. This hypothesis is directly related to critical questions concerning galaxy formation, including the frequency of galaxy mergers, the role mergers play in determining the morphology of galaxies, the observed thinness of spiral disks and the conflict it raises with predicted merger rates in cosmological models, and the relation between the thick disk stars and globular clusters in the Milky Way. The discovery of disk globular clusters in our target objects would represent the first detection of such objects outside the Local Group. ------------------------------------------------------------------------------------ 6092( 8) - 11/15/95 17:31 - [ 2] Observations Description ------------------------ We propose to use the WFPC2 to obtain images in the B (F450W) and I (F814W) filters of the edge-on spiral galaxies NGC 4565 and NGC 5907 in order to search for globular clusters analogous to the thick disk clusters in the Milky Way. We aim to obtain photometry with a signal-to-noise of 10 for objects as faint as M_V = -5.5, which is 1.5Sigma past the expected turnover of the luminosity function. The primary source of noise in the images will be the bright galaxy background, which is about V=21.5 mag/arcsec^2 over most of the image. At the distance of our target galaxies (15 Mpc for NGC 4565 and 11 Mpc for NGC 5907), globular clusters will be just at the resolution limit of the WFC CCDs. Therefore, we consider photometry within a radius of two pixels and use the colors appropriate for spiral galaxies and globular clusters to find that for globular clusters of M_V=-5.5, exposure times of 32 minutes in I and 45 minutes in B are necessary for a S/N of 10 at the distance of NGC 4565, and the corresponding exposure times required for the more nearby NGC 5907 are 10 minutes in I and 15 minutes in B. For NGC 4565, one WFPC2 image with two of the WFC CCDs aligned along the axis of the disk provides sufficient spatial coverage to include almost all expected thick disk clusters. Therefore, we propose to image this galaxy in two orbits, the first for the I image, and the second for the B image. NGC 5907 is nearer, so the exposure times are shorter, but the areal coverage of an individual WFPC2 frame is not as good. Therefore we propose to observe at two positions in this galaxy, with one orbit dedicated to obtaining both B and I exposures at one position, and a second orbit for the other position. Real Time Justification ----------------------- None. Study of thick disk clusters in these galaxies is not feasible except with the spatial resolution of HST. The photometry which provides the basis for the detection of the stellar thick disk in NGC 4565 and the upper limit on such a component in NGC 5907 has been published. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6092( 8) - 11/15/95 17:31 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5907 GALAXY, SPIRAL RA=15H 15M 54.00S +/- 5", 2000 V = +667 B=25.7 DEC=56D 19' 45.5" +/- 5", PLATE- B-I=2.0 +/- 0.2 ID=01RT SURF-BKG(B)=22.0 SURF-BKG(I)=20.5 Comments: Flux values for (faintest) globular clusters in target galaxies Background flux is for galaxy 3 NGC4565 GALAXY, SPIRAL RA=12H 36M 20.69S +/- 3.4", B2000 V = B=26.4 DEC=25D 59' 16.7" +/- 2.5", +1227 B-I=2.0 +/- 0.2 PLATE-ID=038A SURF-BKG(B)=22.0 SURF-BKG(I)=20.5 Comments: Flux values for (faintest) globular clusters in target galaxies Background flux is for galaxy 6092( 8) - 11/15/95 17:31 - [ 4] Visit: 01 Visit Requirements: PCS MODE Fine ORIENT 268D TO 274D On Hold Comments: Additional Comments: Align disk of galaxy along Y-axis of WFC Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4565 WFPC2 IMAGE WF2-FIX F814W CR-SPLIT=NO 1 160S POS TARG 0.0,19.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4565 WFPC2 IMAGE WF2-FIX F814W CR-SPLIT=NO 1 160S POS TARG 0.5,18.5 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4565 WFPC2 IMAGE WF2-FIX F814W CR-SPLIT=NO 1 160S POS TARG -0.5,19.5 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4565 WFPC2 IMAGE WF2-FIX F450W CR-SPLIT=NO 1 200S POS TARG 0.0,19.0 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4565 WFPC2 IMAGE WF2-FIX F450W CR-SPLIT=NO 1 200S POS TARG 0.5,18.5 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4565 WFPC2 IMAGE WF2-FIX F450W CR-SPLIT=NO 1 200S POS TARG -0.5,19.5 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC4565 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG 0.0,-19.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC4565 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG 0.5,-18.5 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC4565 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG -0.5,-19.5 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC4565 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 200S POS TARG 0.0,-19.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC4565 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 200S POS TARG 0.5,-18.5 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC4565 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 230S POS TARG -0.5,-19.5 ------------------------------------------------------------------------------------------------------------------------------------ 6092( 8) - 11/15/95 17:31 - [ 5] Visit: 02 Visit Requirements: PCS MODE Fine ORIENT 197D TO 203D On Hold Comments: Additional Comments: Align disk of galaxy along X-axis of WFC Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5907 WFPC2 IMAGE WF4-FIX F450W CR-SPLIT=NO 1 200S POS TARG 20.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5907 WFPC2 IMAGE WF4-FIX F450W CR-SPLIT=NO 1 200S POS TARG 20.5,-0.5 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5907 WFPC2 IMAGE WF4-FIX F450W CR-SPLIT=NO 1 200S POS TARG 19.5,0.5 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC5907 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 160S POS TARG 20.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5907 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 160S POS TARG 20.5,-0.5 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC5907 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 160S POS TARG 19.5,0.5 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC5907 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 260S POS TARG -20.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC5907 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 260S POS TARG -20.5,0.5 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC5907 WFPC2 IMAGE WF3-FIX F450W CR-SPLIT=NO 1 260S POS TARG -19.5,-0.5 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC5907 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG -20.0,0.0 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC5907 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG -20.5,0.5 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC5907 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 160S POS TARG -19.5,-0.5 ------------------------------------------------------------------------------------------------------------------------------------ 6092( 8) - 11/15/95 17:31 - [ 6] Summary Form for Proposal 6092 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE Fine ORIENT 268D TO 274D POS TARG 0.0,19.0 POS TARG 0.5,18.5 POS TARG -0.5,19.5 POS TARG 0.0,-19.0 POS TARG 0.5,-18.5 POS TARG -0.5,-19.5 PCS MODE Fine ORIENT 197D TO 203D POS TARG 20.0,0.0 POS TARG 20.5,-0.5 POS TARG 19.5,0.5 POS TARG -20.0,0.0 POS TARG -20.5,0.5 POS TARG -19.5,-0.5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F450W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4565 NGC5907 ------------------------------------------------------------------------------------------------------------------------------------