7467( 3) - 01/29/99 16:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7467 Version: 3 Check-in Date: 08-Apr-1997 12:37:45 1.Proposal Title: Do Massive Star Clusters Form in Young and Weak Galaxy Interactions? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: William Keel University of Alabama CoI: Kirk Borne Hughes STX -- NASA / Goddard N ------------------------------------------------------------------------------------ 5. Abstract We propose WFPC2 imaging of two interacting galaxy pairs in two bandpasses (B and I). In the two-dimensional space of interactions that go from weak to strong, and from early to late, these 2 pairs represent the as-yet unstudied cases of ``late weak'' and ``early strong'' interactions. Our goal is primarily to determine whether the super star clusters (SSC's) that are so prevalent in strong, evolved interactions have also been able to form in the weak or young interactions. Secondly, if such clusters are found, we hope to correlate their properties as much as possible to the strengths and ages of the interactions, using the results of previous HST studies (by other authors) of SSC's in older, stronger interactions to complete the correlation space study. We wish to derive the luminosity function, color distribution, and spatial distribution of these clusters, with the hope of correlating those properties with (a) the distribution and site-specific properties of H II regions that are already seen in ground- based H-alpha observations and with (b) the global physical parameters of the tidal interaction event. In this way, we hope to understand further what are the conditions under which such massive star clusters form, what is their prevalence at the present epoch in violently star- forming regions, and are these regions likely analogs for early epochs of star and galaxy formation. ------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 2] Observations Description ------------------------ We propose two-color WFPC2 imaging of 2 targets: NGC 5754 and NGC 6621. Splitting the observations into two filters allows us to retain some color information for the brighter star clusters, while keeping the flexibility to co -add images and go deeper for sheer detection without a large penalty in observing time or noise. We propose a total exposure time of one orbit in each filter (actually the weighting will be about 60:40 in favor of F450W). The I- band (F814W) image will serve to measure the underlying old stellar population, while the B-band (F450W) image will provide both color information and greater sensitivity to the blue light of the young clusters. An indication of any dust obscuration effects will also be discernible in the (B-I) difference image, with such effects kept to a minimum in the I band image. For NGC 5754, our H- alpha data show numerous bright H II regions in the center of its companion (Arp 297C), suggesting that star formation is intense enough there that it would be worthwhile to center the PC chip on this companion. Both target pairs are good matches to the WFPC2 field, so we can search for clusters in the extended tidal features as well as in the main galaxies. Ground-based data show that a few bright H II regions do occur, for example, in the long tidal arm of NGC 5754. Real Time Justification ----------------------- (NONE) Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5754 Galaxy, Interacting RA=14H 45M 16.03S +/- 2", 2000 V=+4519 V = 13.4+/-0.2 Galaxy, Spiral, DEC=+38D 43' 47.1" +/- 2", PLATE B-V = 0.7 Amorphous Irregular -ID=019Q SIZE=120 Comments: The images are to search for luminous star clusters in this interacting-galaxy pair. The high-surface- brightness companion Arp 297C should fall on the PC chip. To ensure this, the pyramid apex position is set to a location between the galaxies (using WF3 and POS TARG to place it there), with ORIENT constrained to keep both galaxies and their tidal structure wthin the overall WFPC2 field. The listed SIZE is diameter to B=25 isophote. 2 NGC6621 Galaxy, Interacting RA=18H 12M 55.3S +/- 1", 2000 V=+6273 B = 14.4+/-0.3 Galaxy, Spiral, DEC=+68D 21' 49.2" +/- 1"PLATE- B-V = 0.8 Elliptical ID=00T0 E(B-V) = 0.13 SIZE=125 Comments: The images are to search for luminous star clusters in this interacting-galaxy pair. The pointing location and POS-TARG specification are designed to put the nucleus of NGC 6621 approximately along a boundary between two of the WF CCDs, and the pair aligned approximately parallel to these two chips, to cover the whole elongated system at once. Four possible ORIENT ranges are specified as possible different visits, only one of which should be executed, to accomodate the four different ways of getting the appropriate field orientation. The listed SIZE is the diameter to the B=25 isophote. 7467( 3) - 01/29/99 16:32 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 240D TO 285D 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 NGC5754 WFPC2 IMAGE WF3-FIX F814W 1 2700. S POS TARG +35, +35 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5754 WFPC2 IMAGE WF3-FIX F450W 1 2700. S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 0D TO 40D On Hold Comments: Additional Comments: Schedule one of visits 2-5; these are specified because there are four disjoint, acceptable ORIENT ranges (with different POS TARG to fit the long axis of this galaxy pair on two WF CCDs). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6621 WFPC2 IMAGE WF3-FIX F814W 1 2700. S POS TARG +35, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6621 WFPC2 IMAGE WF3-FIX F450W 1 2700. S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 90D TO 130D On Hold Comments: Additional Comments: Schedule one of visits 2-5; these are specified because there are four disjoint, acceptable ORIENT ranges (with different POS TARG to fit the long axis of this galaxy pair on two WF CCDs). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6621 WFPC2 IMAGE WF3-FIX F814W 1 2700. S POS TARG 0, +35 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6621 WFPC2 IMAGE WF3-FIX F450W 1 2700. S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 7] Visit: 04 Visit Priority: Visit Requirements: ORIENT 270D TO 310D On Hold Comments: Additional Comments: Schedule one of visits 2-5; these are specified because there are four disjoint, acceptable ORIENT ranges (with different POS TARG to fit the long axis of this galaxy pair on two WF CCDs). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6621 WFPC2 IMAGE WF3-FIX F814W 1 2700. S POS TARG 0, +35 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6621 WFPC2 IMAGE WF3-FIX F450W 1 2700. S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 8] Visit: 05 Visit Priority: Visit Requirements: ORIENT 180D TO 220D On Hold Comments: Additional Comments: Schedule one of visits 2-5; these are specified because there are four disjoint, acceptable ORIENT ranges (with different POS TARG to fit the long axis of this galaxy pair on two WF CCDs). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6621 WFPC2 IMAGE WF3-FIX F814W 1 2700. S POS TARG +35, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6621 WFPC2 IMAGE WF3-FIX F450W 1 2700. S SAME POSition AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7467( 3) - 01/29/99 16:32 - [ 9] Summary Form for Proposal 7467 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 240D TO 285D POS TARG +35, +35 SAME POSition AS 1 ORIENT 0D TO 40D POS TARG +35, 0 ORIENT 90D TO 130D POS TARG 0, +35 ORIENT 270D TO 310D ORIENT 180D TO 220D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F450W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5754 NGC6621 ------------------------------------------------------------------------------------------------------------------------------------