9395( 2) - 02/14/02 15:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9395 Version: 2 Check-in Date: 14-Feb-2002 15:20:11 1.Proposal Title: Is Bulge Formation Still Going-On? , An ACS Survey of Pseudo-Bulges ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: C. Carollo Eidgenossiche Technische Hochschule (ETH) CoI: Dr. Reynier Peletier University of Nottingham N CoI: Dr. Massimo Stiavelli Space Telescope Science Institute N CoI: Dr. Rosemary F. G. Wyse The Johns Hopkins University N CoI: Dr. P. Tim de Zeeuw Leiden Observatory N ------------------------------------------------------------------------------------ 5. Abstract Pseudo-bulges, i.e., bulges with an exponential light profile, have been unveiled in the centers of many intermediate-type disks. Their structural similarity with the disks provides support to theoretical scenarios in which bulges may form due to secular evolution processes within the host disks. If at play, these processes would likely be active throughout a large fraction of cosmic history down to our days: `young' bulges should exist. Our previous HST WFPC2 and NICMOS survey of ~100 spirals has provided V-H colors for 11 Sb-Sc pseudo-bulges, and these could be interpreted as suggestive of relatively young stellar ages. Furthermore, dense nuclei have been discovered in these pseudo-bulges, and their V-H colors may imply stellar masses sufficiently large to activate the formation of the pseudo- bulge by means of dynamical dissolution of progenitor bars. However, the V-H color, on its own, is fully degenerate towards stellar ages, metallicities and masses, as well as dust content. We therefore propose to use ACS to observe the 11 pseudo-bulges of our combined WFPC2 and NICMOS sample in the F330W, F435W, and F814W filters. Extending the wavelength baseline to the bluer passbands is essential to break the mass-age- metallicity-dust degeneracy, and will provide far more accurate estimates for the stellar population properties of the pseudo-bulges and their nuclei. Proving the existence of `young' bulges in the local Universe would have a big impact in our understanding of the formation of the Hubble sequence. ------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 2] Observations Description ------------------------ Why HST (and ACS) Studying the stellar population properties of bulges from the ground is in general very difficult: seeing effects exacerbate any contamination from the disk, and localized compact features such as patches of dust or knots of star formation get blurred with the underlying stellar populations, thereby significantly affecting any estimate for the properties of the latter. This is particularly true for the small, intermediate-type pseudo- bulges: these are rather small creatures, with typical half-light radii of only a few arcseconds or less, making their investigation practically unfeasible from the ground. The high angular resolution of HST is necessary for studying the undelying `smooth' stellar populations in these systems. First, HST allows one to perform an accurate masking of any localized feature, thereby allowing a much more accurate determination of the properties of the underlying stellar populations. Second, it allows a superior disentagling of the bulge from the disk component. Our previous HST study has indeed demonstrated the need for the high angular resolution in order to access the stellar `continuum' underlying the complex structure of dust and bright knots present in the centers of intermediate-type spiral galaxies. ACS provides a far superior performance with respect to the WFPC2 in all filters, including the F330W filter in the HRC channel. The relatively smaller field of view of ACS/HRC with respect to WFPC2 in the U filter is not relevant for our project, since the HRC FOV is large enough to allow us to cover the pseudo- bulges and the inner-disk regions. sectionExposure Time Estimates In order to disentagle age, metallicity, and dust effects one needs colors accurate to better than 10% which require a S/N>~30 in each single filter. Such a S/N can be achieved for every nuclear `star cluster' in the sample by integrating 2700s in F330W, 240s in F435W, and 40s in F814W. A similar S/N is obtained for the isophotal profiles if the S/N over a 0".1 * 0".1 area is ~1.5. However, in order to detect possible gradients and substructure in the nuclear regions of the pseudo-bulges we need at least S/N~=3 over a 0".1 * 0".1 area in each filter. The orbit requirements are driven by the U (F330W) band which we will obtain by using ACS/HRC. To better correct for cosmic rays and detector defects, each exposure will be split in 4 read-outs (2 CR-splits at two locations) without significant loss of S/N. Using the surface brightness measured on the available WFPC2 images at 10 arcsec radius (Carollo et al. 1997, 1998), we find that we need 5400s for NGC1345 and ESO499G37, 3700s for ESO498G5, 3200s for NGC1483 and NGC2758, and 2600s or less for the remaining targets. The same S/N is achieved with ACS/WFC in the B (F435W) and I (F814W) filters with exposures of 650s and 100s, respectively. These exposures will only be split in 2 read-outs. The same exposures will be very effective in identifying individual associations of young stars, i.e., they will allow us to detect a single, unreddened, O5 star in each of the targets. In order to cover the gap between the two WFC chips we will dithered the two F435W and F814W images by more than 1 arcsec. In order to avoid the buffer dump overhead, the F435W and F814W filters the exposure times will be about 740s (in two exposure of 370s each). We have verified that all of our exposures will not saturate. Only the F814W images of the nucleus in NGC 6384 will saturate with the above exposure times. For this object, the saturation is only modest and will be alleviated by beginning the orbit devoted to WFC imaging with an extra single F814W exposure of 50 s duration. This image will be dumped to the SSR during the following longer integration and it will thus not cause an extra overhead. In order to convert the estimated exposure times in actual number of orbits we have taken into account the typical orbit duration (56 minutes), the guide-star acquisition (6.1m) and re-acq (5.7m), and the ACS overheads (taken from the ACS Handbook). As stated above, we require that each individual exposure is longer than 6 minutes to avoid the buffer dump overhead. We therefore need to complete the project 3 orbits for ESO498G5 and ESO499G37, and 2 orbits for all the remaining galaxies, for a total of 25 orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ESO498G5 GALAXY, BULGE RA=9H 24M 41S +/- 0.5", DEC=-25D J2000 V = 14+/-0.1 5' 34" +/- 0.5" Coordinate Source: HST_IMAGE 2 ESO499G37 GALAXY, BULGE RA=10H 3M 42S +/- 0.5", DEC=-27D J2000 V = 13.3+/-0.1 1' 39" +/- 0.5" Coordinate Source: HST_IMAGE 3 NGC406 GALAXY, BULGE RA=1H 7M 25S +/- 0.5", DEC=-69D J2000 V = 13.1+/-0.1 52' 32" +/- 0.5" Coordinate Source: HST_IMAGE 4 NGC1345 GALAXY, BULGE RA=3H 29M 32S +/- 0.5", DEC=-17D J2000 V = 14.3+/-0.1 46' 43" +/- 0.5" Coordinate Source: HST_IMAGE 5 NGC1483 GALAXY, BULGE RA=3H 52M 48S +/- 0.5", DEC=-47D J2000 V = 13.1+/-0.1 28' 39" +/- 0.5" Coordinate Source: HST_IMAGE 6 NGC2082 GALAXY, BULGE RA=5H 41M 51S +/- 0.5", DEC=-64D J2000 V = 12.5+/-0.1 18' 5" +/- 0.5" Coordinate Source: HST_IMAGE 7 NGC2758 GALAXY, BULGE RA=9H 5M 31S +/- 0.5", DEC=-19D J2000 V = 14.0+/-0.1 2' 34" +/- 0.5" Coordinate Source: HST_IMAGE 8 NGC3259 GALAXY, BULGE RA=10H 32M 35S +/- 0.5", DEC=65D J2000 V = 12.9+/-0.1 2' 28" +/- 0.5" Coordinate Source: HST_IMAGE 9 NGC3455 GALAXY, BULGE RA=10H 54M 31S +/- 0.5", DEC=17D J2000 V = 12.8+/-0.1 17' 4" +/- 0.5" Coordinate Source: HST_IMAGE 10 NGC4980 GALAXY, BULGE RA=13H 9M 10S +/- 0.5", DEC=-28D J2000 V = 13.2+/-0.1 38' 32" +/- 0.5" Coordinate Source: HST_IMAGE 11 NGC6384 GALAXY, BULGE RA=17H 32M 24S +/- 0.5", DEC=7D J2000 V = 10.7+/-0.1 3' 38" +/- 0.5" Coordinate Source: HST_IMAGE 9395( 2) - 02/14/02 15:21 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 ESO498G5 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 ESO498G5 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 ESO498G5 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 44 M C ------------------------------------------------------------------------------------------------------------------------------------ 40 ESO498G5 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 46 M POS TARG 0.5, 0.5 C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 5] Visit: 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 ESO499G37 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 ESO499G37 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 ESO499G37 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 44 M C ------------------------------------------------------------------------------------------------------------------------------------ 40 ESO499G37 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 46 M POS TARG 0.5, 0.5 C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 6] Visit: 03 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC406 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1170 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC406 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1170 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC406 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 47 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 7] Visit: 04 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1345 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1345 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1345 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 44 M C ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC1345 ACS/HR ACCUM HRC F330W CR-SPLIT=2 1 46 M POS TARG 0.5, 0.5 C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 8] Visit: 05 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1483 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1120 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1483 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1120 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1483 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 45 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 9] Visit: 06 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC2082 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1140 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC2082 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1140 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC2082 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 46 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 10] Visit: 07 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC2758 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC2758 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC2758 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 42 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 11] Visit: 08 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC3259 ACS/WF ACCUM WFC1 F814W CR-SPLIT=NO,GAIN=2 1 200 S C ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC3259 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1000 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC3259 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2,GAIN=2 1 1000 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC3259 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 46 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 12] Visit: 09 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC3455 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC3455 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC3455 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 42 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 13] Visit: 10 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC4980 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC4980 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1080 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC4980 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 43 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 14] Visit: 11 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC6384 ACS/WF ACCUM WFC1 F435W CR-SPLIT=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC6384 ACS/WF ACCUM WFC1 F814W CR-SPLIT=2,GAIN=2 1 1050 S C ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC6384 ACS/HR ACCUM HRC F330W CR-SPLIT=3 1 43 M C ------------------------------------------------------------------------------------------------------------------------------------ 9395( 2) - 02/14/02 15:21 - [ 15] Summary Form for Proposal 9395 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1 HRC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ACS/HRC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 GAIN=2 CR-SPLIT=3 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.5, 0.5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W F814W F330W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ESO498G5 ESO499G37 NGC406 NGC1345 NGC1483 NGC2082 NGC2758 NGC3259 NGC3455 NGC4980 NGC6384 ------------------------------------------------------------------------------------------------------------------------------------