Version 4, nearly done. Still tweaking figures. Assigned ID: 217 ----- Attempting Submission 1 (Thu Feb 23 21:10:12 GMT 2012) ----- HST Phase I Proposal 217 (cstars_apt.pdf.apt) successfully submitted. ----- Attempting Submission 2 (Fri Feb 24 22:01:31 GMT 2012) ----- HST Phase I Proposal 217 (cstars_apt.pdf.apt) successfully submitted. On Knox Long's advice, I have changed the exposure sequences ----- Attempting Submission 1 (Fri Jul 06 22:17:35 GMT 2012) ----- ----- Attempting Submission 2 (Tue Jul 31 19:17:24 GMT 2012) ----- 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. 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 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. COOL STARS 12 false 0.0 0.0 false false false false SUPPORTED GALAXY DISK SPIRAL 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). M31-DISK2 GSC2-N3300122890 J2000 J2000 16 < H mag < 21 WFC3/IR Imaging No No F153M WFC3/IR Imaging No No F139M WFC3/IR Imaging No No F127M WFC3/IR Imaging No No F098M 1343758105860 /Users/mboyer/MacProposals/HST2012/PhaseII/OP-cache/12862_v2-v01.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. -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 (Tic-Visit :proposal-id 12862 :visit-id "01" :proposal-version -1 :trans-version "20120604" :date "31-Jul-2012 14:08:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 1671264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12862 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12862 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2674 :al-overhead-at-end 0 :internal-dur-at-end 671 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3010 :pcs-gap 0 ) true 1 0 At dither position A At dither position A At dither position A At dither position A At dither position B At dither position B At dither position B At dither position B