7466( 10) - 09/19/00 11:09 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7466 Version: 10 Check-in Date: 19-Sep-2000 11:07:58 1.Proposal Title: From Globular Clusters to Tidal Dwarfs: Structure Formation in Tidal Tails. ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Jane Charlton The Pennsylvania State University CoI: John Hibbard Institute for Astronomy N CoI: Bradley Whitmore Space Telescope Science Institute N CoI: Dennis Zaritsky University of California, Santa Cruz N CoI: Joshua Barnes Institute for Astronomy N ------------------------------------------------------------------------------------ 5. Abstract We propose to study the range of substructures found within the tidal tails of the classic mergers NGC 4038/9, NGC 3921, NGC 7252, and NGC 3256. Structures as large as dwarf Irregulars are found within the tidal debris of each system, and we wish to explore whether there is a continuum of structure all the way down to globular clusters, which are found in such high numbers in the central regions of these mergers. Our sample includes a total of eight tidal tails occurring within four mergers at a variety of evolutionary stages and with a range of properties, and will cover both regions with and without an embedded tidal dwarf. By obtaining WFPC2 images in V and I we will determine the distributions of luminosities, colors, and sizes of all substructures within the tidal tails. These will be contrasted with the properties of the hundreds of young clusters in the central regions. Questions to be addressed include: 1) Do globular clusters form (and survive) in all regions of tidal debris or only within central regions; 2) Do tidal dwarfs also host star clusters; 3) Combining with dynamical information extracted from VLA HI maps, can we constrain the evolution of populations of young globulars (i.e. of their sizes and luminosities)? By modeling these systems with N--body hydrodynamic codes, can we identify the physical circumstances and formation histories which can produce tidal dwarfs, star clusters, and other structures in tidal tails? ------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 2] Observations Description ------------------------ Images in V (F555W) and I (F814W) will be obtained for four interacting galaxies. Similar exposure times, resulting in similar S/N, will be used for the V and I observations. Subpixel dithering between exposures will be used to flatten the background, remove hot pixels, and improve the spatial resolution. The following table illustrates the limiting magnitudes (50% completeness based on numerical experiments performed on WFPC2 images of these galaxies from Whitmore 1996) that can be achieved in the number of orbits requested for each target: Summary of Detection Limits Interacting Galaxy V(km/s) Detection limit Number of Orbits m_V M_v (in V and in I) N4038/9/S 1600 26 -5.6 2 N3921 5800 26 -8.5 1 N7252 4750 26 -8.0 2 N3256 2900 25.5 -7.4 1 Dithering will improve these limits by up to 0.5 magnitudes. Specific targets: NGC 4038/39 --- is the closest system (V=1630km/s), and provides us with the opportunity to explore the fainter part of the luminosity function. One pixel of the WFC corresponds to 14.2pc, and with high S/N images and a good PSF we can easily resolve clusters which have typical effective radii of 3-5pc. A tidal dwarf is embedded within the gas-rich tail southern tail (van der Hulst 1979), while the other tail is gas-poor and contains no such condensation. The dwarf is the target of a deep $UBVI$ HST study (Rich & Hibbard #6669), and we propose to complement this work and that of Whitmore et al. 1995 (who imaged the inner region in Whitmore #5962) with a pointing in each outer tidal tail (shown in Fig. 1). With 1 orbit in V and 1 orbit in I (deeper than for the other systems), we will be able to go as faint as images obtained for the central region (Whitmore et al. #5962) and will allow comparison of the luminosity functions well below the turnover for normal galaxies. NGC 7252 (``Atoms for Peace'') --- This system is an older, more relaxed merger remnant. Both tails are gas rich, and both contain possible tidal dwarfs (Hibbard et al. 1994). WFPC2 images (Whitmore et al. #5416) exist for its inner regions. We propose to cover essentially the full length of the tails, thus obtaining the first HST images of both dwarf galaxies. This coverage is possible because this system is at a larger distance (V = 4740 km/s). At this distance the 23pc pixel size is well suited for measuring the scale length and concentration of the tidal dwarfs and of larger substructures within the tails. WFPC2 observations of the inner regions of NGC 7252 (GO-5416) have already shown that clusters with typical sizes 3-5pc can be resolved on the PC. Performing subpixel dithering will make similar resolution possible on the WF chips, and will slightly improve the resolution on the PC. One orbit in ``V'' and one in ``I'' for each position will reach about the same limiting magnitude as in Whitmore's Cycle 5 images of the central region, about V = I = 26 corresponding to M_V = -8.5. NGC 3921 --- This merger is at a slightly less advanced stage of evolution than NGC 7252 (Schweizer 1996), although the HI observations show that it is the result of a merger between a gas rich and a gas poor disk (Hibbard & van Gorkom 1996). Schweizer (1996) argued that this might be the reason that NGC 3921 has relatively fewer globular cluster systems within its inner regions than NGC 7252. HST WFPC images of the central region of NGC 3921 (Whitmore et al. #5416) cover both the central region and most of the gas poor Northern plume. An example of this inner tidal debris is given in Fig. 2, revealing several young clusters in both the Northern plume, the southern loop, and the base of the southern tail. We again propose 1 orbit in ``V'' and 1 in ``I'', comparable to the time needed to obtain the image in Fig. 2, thus allowing a good comparison to the clusters in the Northern plume. As with NGC7252, this system is relatively distant (V=5838 km/s) so we can cover most of the Southern tail (including the tidal dwarf seen in Fig. 1) with one field. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 3] Data Distribution Paper Products: YES Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4038-9S- GALAXY, TIDAL TAIL RA=12H 1M 58.47S +/- 1", DEC=- J2000 V = 26+/-0.5 POSA 18D 55' 29.4" +/- 1", PLATE- ID=04UV Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 2 NGC4038-9S- GALAXY, TIDAL TAIL RA=12H 1M 49.68S +/- 1", DEC=- J2000 V = 26+/-0.5 POSB 18D 58' 42.2" +/- 1", PLATE- ID=04UV Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 3 NGC4038-9N- GALAXY, TIDAL TAIL RA=12H 2M 5.76S +/- 1", DEC=-18D J2000 V = 26+/-0.5 POSC 49' 56.4" +/- 1", PLATE-ID=04UV Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 4 NGC7252E GALAXY, TIDAL TAIL RA=22H 20M 55.89S +/- 1", DEC=- J2000 V = 26+/-0.5 24D 40' 32.4" +/- 1", PLATE- ID=024S Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 5 NGC7252W GALAXY, TIDAL TAIL RA=22H 20M 37.43S +/- 1", DEC=- J2000 V = 26+/-0.5 24D 37' 20.3" +/- 1", PLATE- ID=024S Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star cluster in tidal debris. 6 NGC3256E GALAXY, TIDAL TAIL RA=10H 28M 3.90S +/- 1", DEC=- J2000 V = 25.5+/-0.5 43D 54' 39.3" +/- 1", PLATE- ID=04UJ Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 7 NGC3256W GALAXY, TIDAL TAIL RA=10H 27M 37.07S +/- 1", DEC=- J2000 V = 25.5+/-0.5 43D 52' 48.6" +/- 1", PLATE- ID=04UJ Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 8 NGC3921S GALAXY, TIDAL TAIL RA=11H 51M 7.52S +/- 1", DEC=55D J2000 V = 26+/-0.5 2' 21.07" +/- 1", PLATE-ID=00LK Coordinate Source: Comments: Flux value is limiting magnitude expected for target globular star clusters in tidal debris. 7466( 10) - 09/19/00 11:09 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 260D TO 280D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S POSA ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S POSA ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSA ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSA ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC4038-9S- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POS TARG 0.25, 0.25 POSA ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC4038-9S- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POSA ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 305D TO 325D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S GS ACQ SCENARIO SINGLE POSB ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S POSB ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSB ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC4038-9S- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSB ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC4038-9S- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POS TARG 0.25, 0.25 POSB ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC4038-9S- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POSB ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 285D TO 305D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC4038-9N- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S POSC ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC4038-9N- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S POSC ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC4038-9N- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSC ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC4038-9N- WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 POSC ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC4038-9N- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POS TARG 0.25, 0.25 POSC ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC4038-9N- WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POSC ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 8] Visit: 04 Visit Priority: Visit Requirements: ORIENT 350D TO 20D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC7252E WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC7252E WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC7252E WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC7252E WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC7252E WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC7252E WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 9] Visit: 05 Visit Priority: Visit Requirements: ORIENT 35D TO 55D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC7252W WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC7252W WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC7252W WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC7252W WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC7252W WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC7252W WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 10] Visit: 06 Visit Priority: Visit Requirements: ORIENT 230D TO 250D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC3256E WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC3256E WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 11] Visit: 07 Visit Priority: Visit Requirements: ORIENT 50D TO 70D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC3256W WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC3256W WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 12] Visit: 08 Visit Priority: Visit Requirements: CVZ On Hold Comments: Additional Comments: Main goal is to look at dwarf galaxy in the PC. If CVZ is too restrictive adjustments could be made. NOTE: Split the two iterations of exposure 11 into exposure 11 and 12. This was done to avoid a bug in the software. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC3921S WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S GS ACQ SCENARIO SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC3921S WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC3921S WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 2 400 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC3921S WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 400 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 41 NGC3921S WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 2 500 S ------------------------------------------------------------------------------------------------------------------------------------ 7466( 10) - 09/19/00 11:09 - [ 13] Summary Form for Proposal 7466 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 260D TO 280D POS TARG 0.25, 0.25 ORIENT 305D TO 325D GS ACQ SCENARIO SINGLE ORIENT 285D TO 305D ORIENT 350D TO 20D ORIENT 35D TO 55D ORIENT 230D TO 250D ORIENT 50D TO 70D CVZ ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4038-9S-POSA NGC4038-9S-POSB NGC4038-9N-POSC NGC7252E NGC7252W NGC3256E NGC3256W NGC3921S ------------------------------------------------------------------------------------------------------------------------------------