9683( 3) - 09/04/02 13:20 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9683 Version: 3 Check-in Date: 04-Sep-2002 13:19:32 1.Proposal Title: A Chandra and HST Study of IC 10: The Nearest Starburst Galaxy to the Milky Way ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Franz Bauer The Pennsylvania State University CoI: Neil Brandt The Pennsylvannia State University N ------------------------------------------------------------------------------------ 5. Abstract We propose joint Chandra and HST observations of IC 10, the nearest starburst galaxy to the Milky Way (0.8 Mpc). We detected a possible ultraluminous X-ray binary in IC 10 (hearafter X-1) with ROSAT, but its properties were very poorly constrained. Chandra+HST will provide a far better measure of X-1's luminosity, spectrum, environment, and position (Wolf-Rayet companion?). The Chandra image will also allow us to study most high-state X-ray binaries and the brightest young, evolving supernova remnants in IC 10, while the HST images will constrain the properties of the intermediate stellar mass population over much of the galaxy. This combination will thus offer a high-resolution glimpse into the early stages of stellar evolution, enabling us to test ideas about the starburst processes. ------------------------------------------------------------------------------------ 9683( 3) - 09/04/02 13:20 - [ 2] Observations Description ------------------------ To resolve and characterize the stellar population within IC~10 via magnitudes and colors, we will observe IC~10 with the ACS detector on {\it HST}. The area covered on the sky by a single ACS pointing is smaller than that of the 500- pixel Chandra ACIS-S3 subarray field of view by a factor of $\approx$3.1. By concentrating the {\it HST} observations on the central regions of IC~10 where the majority of star formation has occurred (see Fig.~1), however, we can image the vast majority of the galaxy in two slightly overlapped ACS pointings. To properly separate age and metallicity degeneracies, as well as to study the important horizontal branch stars within IC~10's stellar population, we require 3-band imaging using the $B$ (F435W), $V$ (F555W), and $I$ (F814W) filters. We adopt $m_v = 25$ as a reasonable working limit for the detection of point sources in IC~10, allowing us to probe IC~10 to $M_V \approx 0.5$, low enough to detect all main sequence O and B, supergiant and bright giant stars (i.e., stars with $\ga$6--10~$M_{\odot}$). To achieve this limit in all three bands with a $S/N = 10$--20, depending on the exact input spectrum chosen, we require exposures of approximately 1200 seconds in each band. Thus, to image two pointings, assuming 1 orbit yields $\sim$ 2400 seconds after overhead, we request a total of 3 {\it HST} ACS orbits. Our proposed ACS observations are comparable in depth to the archival WFPC2 $V$ and $I$ images outlined in Fig.~1, but will achieve uniform coverage of IC~10 over an area $\sim$6$\times$ larger and at twice the spatial resolution. These new ACS observations represent a substantial leap in high-resolution coverage and will be invaluable both as a tool for identifying optical counterparts to {\it Chandra} X-ray sources and for the study of IC~10's stellar populations in general. Based on the stellar density in the archival WFPC observations ($\sim$44, 000 stars), we predict the multi-band detection of $>$200, 000 stars with ACS. The two ACS pointings will not be highly roll-angle constrained since they can be observed at 90$^\circ$ ($\pm$ 10--15$^\circ$) intervals from our preferred orientation without substantial loss of coverage. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9683( 3) - 09/04/02 13:20 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-POS1 GALAXY, DWARF COMPACT RA=00H 20M 26.2S +/- 5", DEC=59D J2000 B = 11.8+/-0.5 17' 35.6" +/- 5" Coordinate Source: IMAGE_TIED_TO_GSC_FRAME 2 IC10-POS2 GALAXY, DWARF COMPACT RA=00H 20M 24.42S +/- 5", J2000 B = 11.8+/-0.5 DEC=59D 17' 34.0" +/- 5" Coordinate Source: IMAGE_TIED_TO_GSC_FRAME 9683( 3) - 09/04/02 13:20 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose MOSAIC Number_Of_Points 2 Point_Spacing 130 Coordinate_Frame CELESTIAL Pattern_Orient 320 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9683( 3) - 09/04/02 13:20 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 130D TO 150D On Hold Comments: Additional Comments: I've specified only one roll angle (130-150deg), but these observations may also be performed at ~90 deg offset roll angles such as 40-60, 220-240, or 310-330 provided the aimpoints are changed to crudely have the same ariel coverage of IC 10. These aimpoints are '00 20 27.0,+59 17 35.6', '00 20 24.0,+59 17 18.6', and '00 20 24.4,+59 17 38.6', respectively. Also note that the second aimpoint is offset from the original by ~2.6" in the direction of the roll angle in order to image objects which fall within the ACS chip gap of the first aimpoint. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC10-POS1 ACS/WF ACCUM WFC F435W CR-SPLIT=3 1 1020 S PATTERN 1 1 C ------------------------------------------------------------------------------------------------------------------------------------ 2 IC10-POS2 ACS/WF ACCUM WFC F606W CR-SPLIT=3 1 1080 S PATTERN 1 2 C ------------------------------------------------------------------------------------------------------------------------------------ 3 IC10-POS2 ACS/WF ACCUM WFC F814W CR-SPLIT=3 1 1080 S PATTERN 1 3 C ------------------------------------------------------------------------------------------------------------------------------------ 9683( 3) - 09/04/02 13:20 - [ 6] Summary Form for Proposal 9683 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 130D TO 150D PATTERN 1 1 PATTERN 1 2 PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F435W F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names IC10-POS1 IC10-POS2 ------------------------------------------------------------------------------------------------------------------------------------