12862( 3) - 31-Jul-2012 20:01:49 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12862 Version: 3 Check-in Time: 31-Jul-2012 20:01:49 STScI Edit Number: 0 Title Towards Identifying Carbon Stars Beyond the Local Group ------------------------------------------------------------------------------------ Type Cycle GO 20 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Martha Boyer Space Telescope Science Institute Y CoI: Dr. Julianne Dalcanton University of Washington N CoI: Dr. Leo Girardi Osservatorio Astronomico di Padova N CoI: Dr. Karl D. Gordon Space Telescope Science Institute N CoI: Dr. Paola Marigo Universita degli Studi di Padova N CoI: Dr. Jason Lee Melbourne California Institute of Technology N CoI: Dr. Knut A.G. Olsen National Optical Astronomy Observatory, N AURA CoI: Mr. Philip A. Rosenfield University of Washington N CoI: Dr. Daniel R. Weisz University of Washington N CoI: Dr. Benjamin F. Williams University of Washington N ------------------------------------------------------------------------------------ Abstract Recently, HST WFC3/IR broad-band imaging has proved effective at detecting AGB stars in galaxies beyond the Local Group, but it is impossible to distinguish between different AGB subtypes with only the available broad-band filters. We propose a 1-orbit pilot program to establish the ability of the WFC3/IR medium-band filters to separate carbon-rich and oxygen-rich AGB stars. Synthetic spectra of C and M stars indicate that the molecular features in the NIR will cause C-rich stars to appear much bluer than O-rich stars in medium-band colors. The ratio of C to M stars can have a dramatic impact on a galaxy's NIR flux and colors and studies of the C-rich stars in particular inform models of the processes of the third dredge up and dust production (which is dominated by C-rich sources in the Magellanic Clouds). Separating C-rich and O-rich AGB stars in galaxies outside of the Local Group will provide robust constraints on stellar evolution models, especially in the low and high metallicity realms, and act as a pathfinder for future mid-IR JWST observations. We choose a well-studied field in M31 to calibrate the utility of using WFC3's medium-band filters to separate C and M stars. The metal-rich environment of M31 provides the added benefit of an opportunity to study C-rich stars at high metallicity. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe a field in M31 with WFC3/IR in the four medium-band IR filters, using a single orbit. We can achieve the necessary photometric depth in all four WFC3/IR medium-band filters within a single orbit. This allows for total exposure times of about 600 s in each filter, resulting in S/N >~9 in F139M for m_H = 22 mag. The S/N 12862( 3) - 31-Jul-2012 20:01:49 - [ 2] is even better in the F098M, F127M, and F153M filters, owing to a higher throughput. We choose a 2-point dithering strategy that will allow us to fit all four medium-band filters into a single orbit. Each exposure is about 300 s. We will avoid saturation of bright sources by using the STEP ramp sequences with 11 reads. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12862( 3) - 31-Jul-2012 20:01:49 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC224-DISK2 GALAXY, DISK, SPIRAL RA=00H43M21.6600S +/- 0.1", J2000 16 < H mag < 21 DEC=+41D21'55.08" +/- 0.1" Reference Frame: Other: GSC2 Comments: This is a field of the disk of M31 from Davidge et al. (2007). There is one bright star in the center that they used for AO imaging. The field is centered on that star (GSC2-N3300122890, V=11.386 +/- 0.122 mag, J=9.334 +/- 0.022 mag). We are targeting all AGB stars in the field (H < 21 mag). ------------------------------------------------------------------------------------------------------------------------------------ 12862( 3) - 31-Jul-2012 20:01:49 - [ 4] Visit: 01 Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: -All four medium-band filters (F098M, F127M, F139M, F153M), one field. -Two ~300s exposures per filter, using the STEP50 timing sequences. NSAMP = 11. -Each pair of exposures are manually dithered, according the WFC3/IR Manual, by adjusting POSTARG to mimic a linear 2-point dither. -Exposures arranged to avoid latency due to buffer dump. -Total of one orbit Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC224-DISK WFC3/IR MULTIAC IR F098M SAMP-SEQ=STEP50, NSAMP=11 1 DEF 2 CUM Comments: At dither position A ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC224-DISK WFC3/IR MULTIAC IR F127M SAMP-SEQ=STEP50, NSAMP=11 1 DEF 2 CUM Comments: At dither position A ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC224-DISK WFC3/IR MULTIAC IR F139M NSAMP=11, SAMP-SEQ=STEP50 1 DEF 2 CUM Comments: At dither position A ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC224-DISK WFC3/IR MULTIAC IR F153M NSAMP=11, SAMP-SEQ=STEP50 1 DEF 2 CUM Comments: At dither position A ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC224-DISK WFC3/IR MULTIAC IR F153M NSAMP=11, SAMP-SEQ=STEP50 1 DEF POS TARG 0.474, 0.424 2 CUM Comments: At dither position B ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC224-DISK WFC3/IR MULTIAC IR F098M NSAMP=11, SAMP-SEQ=STEP50 1 DEF POS TARG 0.474, 0.424 2 CUM Comments: At dither position B ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC224-DISK WFC3/IR MULTIAC IR F139M NSAMP=11, SAMP-SEQ=STEP50 1 DEF POS TARG 0.474, 0.424 2 CUM Comments: At dither position B ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC224-DISK WFC3/IR MULTIAC IR F127M NSAMP=11, SAMP-SEQ=STEP50 1 DEF POS TARG 0.474, 0.424 2 CUM Comments: At dither position B ------------------------------------------------------------------------------------------------------------------------------------ 12862( 3) - 31-Jul-2012 20:01:49 - [ 5] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC224-DISK2 1 WFC3/IR MULTIAC IR F098M none none none none 1 N/A CUM NGC224-DISK2 2 WFC3/IR MULTIAC IR F127M none none none none 1 N/A CUM NGC224-DISK2 3 WFC3/IR MULTIAC IR F139M none none none none 1 N/A CUM NGC224-DISK2 4 WFC3/IR MULTIAC IR F153M none none none none 1 N/A CUM NGC224-DISK2 5 WFC3/IR MULTIAC IR F153M none none none none 1 N/A CUM NGC224-DISK2 6 WFC3/IR MULTIAC IR F098M none none none none 1 N/A CUM NGC224-DISK2 7 WFC3/IR MULTIAC IR F139M none none none none 1 N/A CUM NGC224-DISK2 8 WFC3/IR MULTIAC IR F127M none none none none 1 N/A CUM 12862( 3) - 31-Jul-2012 20:01:49 - [ 6] Summary Form for Proposal 12862 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=11, SAMP-SEQ=STEP50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.474, 0.424, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F098M, F127M, F139M, F153M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC224-DISK2 ------------------------------------------------------------------------------------------------------------------------------------