10242( 4) - 05/07/04 13:27 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10242 Version: 4 Check-in Date: 07-May-2004 17:24:09 1.Proposal Title: Pre-History of a Starburst: Deep Imaging of IC 10 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 13 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Andrew A. Cole Kapteyn Astronomical Institute CoI: Prof. Christopher L. Taylor California State University - Sacramento N CoI: Prof. J. Gallagher III University of Wisconsin - Madison N CoI: Prof. Eric Wilcots University of Wisconsin - Madison N ------------------------------------------------------------------------------------ 6. Abstract The peculiar Local Group dwarf galaxy IC 10 is the nearest case of a starburst in progress. Starburst galaxies are a prime laboratory for studying the physical processes which regulate star formation in galaxies; as the closest example, IC 10 is potentially the key galaxy for understanding the starburst phenomenon. We propose to obtain deep optical images of IC 10 with the ACS/WFC to achieve three main goals: 1) To make the first estimates of the pre-burst history of IC 10 based on morphological and statistical analysis of its (V, I) color-magnitude diagram; 2) to search for evidence of a past history of burst-dormancy cycles; and 3) to explore the connection between the ages and locations of bright stars and the large-scale structure of the interstellar medium. The distance (0.8 Mpc), extinction (2.5 mag), and high surface brightness of IC 10 make these goals unobtainable except with HST. The observations proposed here will yield far and away the deepest images, in absolute magnitudes, ever obtained for any starburst galaxy. Our photometry will reach to magnitudes (V, I) = (28.5, 27.5), which is below the level of the red clump/horizontal branch and the location of the main-sequence turnoff of stars as old as a billion years. For the first time, it will be possible to measure the detailed history of a starburst host for the Gigayear time period leading up to the burst. The horizontal branch morphology and colors will provide new information on the metallicity and age distribution of stars spanning the entire age of IC 10. Because of its close distance, IC 10 is the ONLY starburst galaxy for which this type of information is obtainable now or in the next decade. We propose to use WFPC2 in parallel to search for a low-surface brightness population associated with the neutral gas filaments surrounding IC 10. ------------------------------------------------------------------------------------ 10242( 4) - 05/07/04 13:27 - [ 2] Observations Description ------------------------ We will image the northern half of IC10 using the F555W and F814W filters of ACS/WFC, and an outlying region of the galaxy in F555W and F814W with WFPC2 in parallel. Our exposures are designed to uncover the pre-starburst history of IC10 by allowing photometry down to roughly 28th magnitude in the central field (about 2 mag brighter in the flanking field). Our limiting magnitude requirements are based on the expected brightness and colors of vital stellar populations tracers, most notably the horizontal branch. Simulations predict this feature to lie at (V, I) ~ (27.9, 25.9) for a distance of 820 kpc and a reddening E(B-V) = 0.85 mag. To accurately measure the HB, we require S/N > 5 photometry at least half a magnitude deeper than this; to measure the main- sequence turnoff of a 1 Gyr old population requires photometry to I ~ 27.5. The ACS ETC shows that exposures of 19840 sec in F555W and 9520 sec in F814W will meet this goal. This amounts to 8 and 4 orbits of imaging, respectively. We wil use WFPC2 parallels to attempt to detect a possible stellar population associated with the infalling HI streamers around IC10, and to help constrain the amount of contamination by foreground stars. Because of IC10's low galactic latitude, it is necessary to limit individual exposures to ~600 sec to prevent saturated foreground stars (V ~ 14) from obliterating too many WFC pixels by blooming; shorter exposures are impractical because of the overheads incurred by ACS buffer dumps and potential conflicts with readouts of the WFPC2 parallels. To maximize dynamic range and minimize saturation problems, we will observe with GAIN=2 instead of the default GAIN=1. Cosmic rays and hot pixels will be accounted for using the prescribed line dither pattern. Existing HST images and multi-color broad and narrowband imaging (UBVIJHK, H alpha/Hbeta) will be used to correct for differential reddening effects in the analysis. Should the parallel observations fail to reveal a low-surface brightness stellar population associated with the HI filaments, they will still be of great use for statistical subtraction of the foreground population. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- IC10 was observed by ACS in program 9683 (PI: Bauer), but the exposures were factors of 2-4 too short to achieve our science goals. Program 9683 focussed on the starburst itself, while we are concerned with the quiescent galaxy outside the burst. The existing data are complementary to our proposed observations, because we can use F435W photometry to help constrain differential reddening. WFPC2 observations of IC10 by Hunter focused only on the central starburst region and are both too shallow and too spatially limited to address questions of the pre-burst history of IC10. We retrieved the archival ACS/WFC images to confirm that our proposed exposures will limit the blooming of bright stars to an acceptable level (<1% of pixels even in a worst-case scenario). 10242( 4) - 05/07/04 13:27 - [ 3] ------------------------------------------------------------------------------------ 10242( 4) - 05/07/04 13:27 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-BAR GALAXY, STARBURST, RA=00H20M13.7S +/- 0.3", J2000 V = - V = 26.0+/-2.0 DWARF COMPACT, DEC=+59D20'23.1" +/- 0.3", 348.0 B-V = 1.3 +/- 0.2 MAGELLANIC IRREGULAR PLATE-ID=01MT E(B-V) = 0.9 +/- 0.2 Coordinate Source: GSC_SURVEY_PLATE Comments: Galactic foreground stars with V ~ 14 are present. 10242( 4) - 05/07/04 13:27 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.146 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 47.17 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 10242( 4) - 05/07/04 13:27 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 0.0D TO 84.0 D; ORIENT 144.0D TO 249.0 D; ORIENT 344.0D TO 359.9 D On Hold Comments: Additional Comments: ORIENT specification from -16 to 249 (North through East) is required to place WFPC2 parallels on the network of infalling HI fillaments which surround IC10 while ACS/WFC is primary. The filaments cover PA 30-295 degrees on the sky relative to the ACS/WFC aperture, to which is added 314 degrees (modulo 360), the position angle between WFALL-FIX and WFC (Table 7.5 of Phase II instructions). ORIENTs from 84 to 144 degrees are excluded to keep 10th magnitude stars off the WFPC2 field. Alignment was confirmed using the VTT. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-BAR ACS/WFC ACCUM WFC F814W CR-SPLIT=2,GAIN=2 1 1190 S PATTERN 1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 3 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 3-4; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 5 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 5-6; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 1 1 none none 1 1 tbd 01 1 1 none none 2 1 tbd 01 1 2 none none 1 1 tbd 01 1 2 none none 2 1 tbd 01 2 1 none none 1 1 tbd 01 2 1 none none 2 1 tbd 01 2 2 none none 1 1 tbd 01 2 2 none none 2 1 tbd 01 3 1 none none 1 2 tbd 01 3 1 none none 2 2 tbd 01 3 2 none none 1 2 tbd 01 3 2 none none 2 2 tbd 01 4 1 none none 1 2 tbd 10242( 4) - 05/07/04 13:27 - [ 7] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 4 1 none none 2 2 tbd 01 4 2 none none 1 2 tbd 01 4 2 none none 2 2 tbd 01 5 1 none none 1 3 tbd 01 5 1 none none 2 3 tbd 01 5 2 none none 1 3 tbd 01 5 2 none none 2 3 tbd 01 6 1 none none 1 3 tbd 01 6 1 none none 2 3 tbd 01 6 2 none none 1 3 tbd 01 6 2 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 8] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: This visit should have the same ORIENT as Visit 01 in order to measure stars in the corners of the WFC with the same S/N as those in the center, and to keep WFPC2 parallels aligned on the region of HI infall. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-BAR ACS/WFC ACCUM WFC F814W CR-SPLIT=2,GAIN=2 1 1190 S PATTERN 1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 3 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 3-4; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 5 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 5-6; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 1 1 none none 1 1 tbd 02 1 1 none none 2 1 tbd 02 1 2 none none 1 1 tbd 02 1 2 none none 2 1 tbd 02 2 1 none none 1 1 tbd 02 2 1 none none 2 1 tbd 02 2 2 none none 1 1 tbd 02 2 2 none none 2 1 tbd 02 3 1 none none 1 2 tbd 02 3 1 none none 2 2 tbd 02 3 2 none none 1 2 tbd 02 3 2 none none 2 2 tbd 02 4 1 none none 1 2 tbd 02 4 1 none none 2 2 tbd 02 4 2 none none 1 2 tbd 02 4 2 none none 2 2 tbd 02 5 1 none none 1 3 tbd 02 5 1 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 9] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 5 2 none none 1 3 tbd 02 5 2 none none 2 3 tbd 02 6 1 none none 1 3 tbd 02 6 1 none none 2 3 tbd 02 6 2 none none 1 3 tbd 02 6 2 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 10] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: This visit should have the same ORIENT as Visit 01 in order to measure stars in the corners of the WFC with the same S/N as those in the center, and to keep WFPC2 parallels aligned on the region of HI infall. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-BAR ACS/WFC ACCUM WFC F814W CR-SPLIT=2,GAIN=2 1 1190 S PATTERN 1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 3 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 3-4; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 5 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 5-6; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 03 1 1 none none 1 1 tbd 03 1 1 none none 2 1 tbd 03 1 2 none none 1 1 tbd 03 1 2 none none 2 1 tbd 03 2 1 none none 1 1 tbd 03 2 1 none none 2 1 tbd 03 2 2 none none 1 1 tbd 03 2 2 none none 2 1 tbd 03 3 1 none none 1 2 tbd 03 3 1 none none 2 2 tbd 03 3 2 none none 1 2 tbd 03 3 2 none none 2 2 tbd 03 4 1 none none 1 2 tbd 03 4 1 none none 2 2 tbd 03 4 2 none none 1 2 tbd 03 4 2 none none 2 2 tbd 03 5 1 none none 1 3 tbd 03 5 1 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 11] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 03 5 2 none none 1 3 tbd 03 5 2 none none 2 3 tbd 03 6 1 none none 1 3 tbd 03 6 1 none none 2 3 tbd 03 6 2 none none 1 3 tbd 03 6 2 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 12] Visit: 04 Visit Priority: Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: This visit should have the same ORIENT as Visit 01 in order to measure stars in the corners of the WFC with the same S/N as those in the center, and to keep WFPC2 parallels aligned on the region of HI infall. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-BAR ACS/WFC ACCUM WFC F814W CR-SPLIT=2,GAIN=2 1 1190 S PATTERN 1 1-2; PAR 2 WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ANY WFPC2 IMAGE WFALL-FIX F814W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 3 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 3-4; PAR 4 WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 5 IC10-BAR ACS/WFC ACCUM WFC F555W CR-SPLIT=2,GAIN=2 1 1240 S PATTERN 1 5-6; PAR 6 WITH 5 ------------------------------------------------------------------------------------------------------------------------------------ 6 ANY WFPC2 IMAGE WFALL-FIX F555W CR-SPLIT=DEF 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 04 1 1 none none 1 1 tbd 04 1 1 none none 2 1 tbd 04 1 2 none none 1 1 tbd 04 1 2 none none 2 1 tbd 04 2 1 none none 1 1 tbd 04 2 1 none none 2 1 tbd 04 2 2 none none 1 1 tbd 04 2 2 none none 2 1 tbd 04 3 1 none none 1 2 tbd 04 3 1 none none 2 2 tbd 04 3 2 none none 1 2 tbd 04 3 2 none none 2 2 tbd 04 4 1 none none 1 2 tbd 04 4 1 none none 2 2 tbd 04 4 2 none none 1 2 tbd 04 4 2 none none 2 2 tbd 04 5 1 none none 1 3 tbd 04 5 1 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 13] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 04 5 2 none none 1 3 tbd 04 5 2 none none 2 3 tbd 04 6 1 none none 1 3 tbd 04 6 1 none none 2 3 tbd 04 6 2 none none 1 3 tbd 04 6 2 none none 2 3 tbd 10242( 4) - 05/07/04 13:27 - [ 14] Summary Form for Proposal 10242 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC WFALL-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 GAIN=2 CR-SPLIT=DEF ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0.0D TO 84.0 D; ORIENT 144.0D TO 249.0 D; ORIENT 344.0D TO 359.9 D PATTERN 1 1-2; PAR 2 WITH 1 PATTERN 1 3-4; PAR 4 WITH 3 PATTERN 1 5-6; PAR 6 WITH 5 SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names IC10-BAR ANY ------------------------------------------------------------------------------------------------------------------------------------