8717( 2) - 03/30/00 09:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8717 Version: 2 Check-in Date: 01-Mar-2000 17:16:09 1.Proposal Title: Observations of Stellar Systems in Seyfert's Sextet ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Sally Hunsberger Lowell Observatory CoI: Prof. Jane Charlton Pennsylvania State University N CoI: Dr. Jayanne English Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain imaging in WFPC2 UBVI filters of the compact group of galaxies known as Seyfert's Sextet, near enough that super star clusters are detectable and luminosity profiles can be constructed for possible dwarf galaxy members, yet compact enough that the Sextet can be imaged in one pointing. Stages of Toomre's merger sequence, from initial encounter through interaction to final merger, occur simultaneously in the field-of-view. Our goal is to appraise the epochs of star formation associated with each of these stages in order to assess the role interactions and mergers play in the formation of stellar systems (e.g. globular clusters, dwarf galaxies) and in the evolution of galaxies within dense groups. Analysis of earlier HST observations (e.g. NGC 4038/9) has shown that stellar population ages can be determined by imaging in four filters. Single burst star formation systems, such as super star clusters, will be used to pinpoint eras of starburst. Stellar ages in tidal dwarfs, i.e., small galaxies forming in tidal tails, will indicate whether their stars were born in the sudden collapse of an HI cloud or whether they are clumps of stars torn from the ``parent'' galaxy. The formation epochs of stellar systems, along with their spatial distribution, and the detailed morphologies of the giant galaxies will constrain numerical simulations which attempt to model the Sextet's interaction history and/or the evolution of compact groups. ------------------------------------------------------------------------------------ 8717( 2) - 03/30/00 09:21 - [ 2] Observations Description ------------------------ WFPC2 will be used to image Seyfert's Sextet with the following filters: F336W (U), F439W (B), F555W (V), and F814W (I). At the target latitude, an HST orbit is 54 minutes and we are requesting six orbits for the proposed observations. The plan is to utilize two orbits each for the U and B observations and one orbit each for V and I. Total exposure times are 5200s for U, 5200s for B, 2000s for V, and 2000s for I. Observations in each filter will be split into four exposures, two at a single position in order to optimize removal of cosmic rays. Subpixel dithering (2 positions) will enhance spatial resolution. This is particularly helpful for detection of super star clusters which are marginally resolved at the distance of Seyfert's Sextet. According to results from the WFPC2 exposure time calculator, the proposed exposures yield signal-to-noise- per-pixel values of 1.4 for surface brightnesses of 23.1, 24.2, 24.5, and 23.7 mag/arcsec^2 in U, B, V, and I, respectively. Reaching these limits will allow us to also detect dwarf galaxies which can exhibit fairly low surface brightnesses. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8717( 2) - 03/30/00 09:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6027 CLUSTER OF GALAXIES, RA=15H 59M 13.98S +/- 0.02S, J2000 Z = SURF(V) = 21.3 GROUP, INTERACTING DEC=+20D 45' 14.99" +/- 0.34", 0.01450 E(B-V) = 0.055 GALAXY, TIDAL TAIL PLATE-ID=028U 8717( 2) - 03/30/00 09:21 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 115D TO 125D 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 NGC6027 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 1000 S POS TARG 0.00, 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6027 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 1000 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6027 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 1000 S POS TARG 0.00, 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6027 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 1000 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6027 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 2600 S POS TARG 0.00, 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6027 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 2600 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6027 WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 2600 S POS TARG 0.00, 0.00 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6027 WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=0.5,CR-TOLERANCE=0.1 1 2600 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 8717( 2) - 03/30/00 09:21 - [ 5] Summary Form for Proposal 8717 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.5 CR-TOLERANCE=0.1 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 115D TO 125D POS TARG 0.00, 0.00 POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W F336W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6027 ------------------------------------------------------------------------------------------------------------------------------------