In this era of precision measurement of the parameters of the cosmological equation of state, constraining the present-day value of the Hubble constant remains a vital endeavor: uncertainties in H_0 couple directly to imprecision in the matter and dark energy contributions to the evolution of the universe (e.g., w, and w1). Starting with the HST Key Project more than a decade ago, the uncertainty in H_0 has been cut from over 10% to something approaching 3%. A major advance was made recently, leapfrogging Milky Way calibrations, by directly anchoring the infrared Cepheid Period-Luminosity (PL) relation to NGC 4258, the famous megamaser galaxy with a highly precise geometric distance. We propose to anchor the infrared PL relation of Mira variables to NGC 4258, providing the first-ever absolute extragalactic PL relation of such stars, opening a new avenue for precision H_0 efforts. In the infrared, Miras are comparable in absolute magnitude to Cepheids, and thus are direct complements to Cepheids within the same volume (up to ~25 Mpc). The principal advantage of Miras, however, is that they are ~20 times more numerous than Cepheids. Thus, a Mira-focused distance measurement study can cover 5% of the surface area of a Cepheid-focused study and achieve a comparable distance measurement accuracy. Over the 12 proposed visits with WFC3/F160W/F125W, and coupled with previous observations of the field, we expect to discover and characterize ~1000 Miras, accurately identifying periods <~ 550 days. This investment now should demonstrate significant observing efficiency increases for JWST if indeed Miras are found to be an acceptable replacement to Cepheids. We propose to observe approximately one epoch of one field in NGC 4258 per month throughout Cycle 21 (12 epochs total). The proposed observations will overlap with the full galaxy mosaic taken during Cycle 17 as part of program GO-11570 (PI: Riess), and we have selected the target field to also overlap with the "inner" ACS field of the Cycle 12 program GO-9810 (PI: Greenhill). These previous studies focused on discovering Cepheid variables do not offer the necessary time baseline for discovery of the longer-period Mira variables, which is the goal of the present proposal. However, selecting our target field to overlap with these earlier observations does provide additional epochs and will be of significant assistance in identifying Miras. All observations will be taken with the WFC3 instrument through the IR/F160W and IR/F125W filters. We will use the F160W light curves to measure the periods and mean magnitudes of the Mira variables. The F125W data is necessary for separating out the O-rich and C-rich Mira sub-populations. The first visit will comprise 2 orbits, one dedicated to a deep integration with F160W (4 x 702.939 secs) and the other with F125W (also 4 x 702.939 secs). This initial visit provides an epoch for the F160W light curves as well as the same-phase color-magnitude information for separating the Mira sub-populations. In the next 11 visits, each comprised of one orbit, we will obtain one shallow F125W exposure (1 x 352.835 secs) and one deep F160W integration (4 x 552.937 secs). Wherever an integration is composed of 4 exposures we use the WFC3-IR-DITHER-BOX-MIN dither pattern. The 11 one-orbit visits will flesh out the rest of the F160W Mira light curves, provide F125W light curves for the brightest Miras, and furnish data for a "phase-average" color-magnitude diagram. Because our visits must be spaced throughout the cycle, specifying roll angle restrictions is impractical. Our final dataset will have 12 epochs for each source within the inscribed circle and fewer epochs at larger radii from the field center (depending on how the fields of view overlap). The special scheduling requirements needed for this project are to space the 12 epochs as evenly as possible throughout the Cycle. Unfortunately, because of the Sun restriction, we can only observe the target from October 1, 2013 (start of the Cycle) to August 5, 2014 (baseline of ~10 months). The visit scheduling was run with the first visit fixed to be between October 1, 2013 and October 7, 2013 and then each subsequent visit occurring between 27 and 31 days after the preceding visit. To sample the full light curve of Mira variables we need to observe with a baseline at least as long as a typical Mira's period and with evenly spaced (although not identically spaced) epochs. This is necessary for recovering an accurate period and temporal mean magnitude for each light curve. The addition of the Cycle 17 data is very helpful in recovering periods longer than 1 year, but every possible advantage from scheduling strategy in the current Cycle should be cultivated. COSMOLOGY 12 false false false false false SUPPORTED GALAXY DISK J2000 J2000 WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F125W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "01" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2228336 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "01" :orbit-number 1 :pcs-time 241 :si-vis-utilization 3040 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) (Tic-Orbit :proposal-id 535 :visit-id "01" :orbit-number 2 :pcs-time 176 :si-vis-utilization 3040 :al-overhead-at-end 0 :internal-dur-at-end 538 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "02" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:47.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "02" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "03" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:48.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "03" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "04" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:49.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "04" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "05" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:51.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([07 After 06 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "06" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 16:38:16.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([07 After 06 by 27.0 to 31.0 days] [08 After 07 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "07" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:52.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "07" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([08 After 07 by 27.0 to 31.0 days] [09 After 08 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "08" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:53.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([09 After 08 by 27.0 to 31.0 days] [10 After 09 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "09" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:54.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "09" :obset-id "09" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "09" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([10 After 09 by 27.0 to 31.0 days] [11 After 10 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "10" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:54.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "10" :obset-id "10" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "10" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([11 After 10 by 27.0 to 31.0 days] [12 After 11 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "11" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:55.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "11" :obset-id "11" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "11" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0 Timing link suitability includes constraints ([12 After 11 by 27.0 to 31.0 days]) The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 535 :visit-id "12" :proposal-version -1 :trans-version "20130502" :date "28-Jun-2013 15:49:56.0" :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 1061936 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 535 :visit-id "12" :obset-id "12" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 535 :visit-id "12" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2820 :al-overhead-at-end 0 :internal-dur-at-end 481 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3377 :pcs-gap 0 ) false 1 0