Young supernova remnants (SNRs), especially ones like Cas A where heavy elements are still prominent, provide insights into SNe, the stars that produce them, and the galaxies where they reside. Here we propose to leverage and expand on existing Hubble ACS/WFC images of the iconic face-on spiral M101 by obtaining new [O III] data and [S II] images with WFC3 to identify and characterize the SNR population of M101. Deep H-alpha images of M101 already exist for 4 ACS fields, as does an extremely deep (1 Ms Chandra) X-ray study--important since many SNRs, including ALL of the known ejecta-dominated ones, are strong X-ray sources. While existing data have enabled exploration of SNRs previously identified from the ground, they do not allow identifications of new (and especially young) SNRs. We propose to observe these fields in [O III] (strongest line in ejecta-dominated SNRs) and [S II] (to provide the [S II]/H-alpha ratio diagnostic to distinguish SNRs from photoionized nebulae), plus adding one new field in these lines plus H-alpha. For a modest time investment, all the optical and X-ray diagnostics will be in hand to explore what we expect to be a rich population of young SNRs in the complex inner regions of the galaxy where HST resolution is most needed. Furthermore, ACS images in BVI also exist for these fields, so we will use CMD fitting to constrain the progenitor masses for many of these as we did for the SN 1957D remnant in M83. We will compare to other galaxies, especially M83 where the young SNRs appear to have evolved quickly beyond the ejecta-dominated stage. M101 and M83 differ in mean abundances and star formation rate areal density, providing contrasting conditions. In this program, we will obtain new [O III] and [S II] emission-line images or four fields in the galaxy M101 for which deep Halpha observations are in the archive (along with BVI broadband data). We will also observe one new field that fills in a hole in the spatial coverage from the existing four fields, and this field will be observed in Halpha as well as [O III] and [S II]. Both WFC3 and ACS have [O III] and Halpha filters and so in principle either could be used for these portions of our program. The WFC3, however, has the F673N filter necessary for obtaining the [S II] measurements we need. Based on the availability of postflash with WFC3 to mitigate CTE, we have decided to take all of the new data requested here with WFC3. The price we pay is a loss of some spatial coverage that we would obtain with the larger ACS field of view, but given that much of our science is driven by faint emission-line sources, we have decided to go with WFC3. In some sense, this will also simplify our data analysis on the back end, since all of the new data will be obtained with the same instrument. ACS B, V, I broadband data from archived program 9490 (Kuntz, PI) exist for the entire region of interest, and will be used to subtract the existing ACS Halpha data, and allow us to study the stellar component near each SNR. However, rather that attempt to use ACS data to subtract the new WFC3 data, we rwill observe WFC3 F547M continuum images as part of this program. This avoids alignment and PSF variation complications between ACS and WFC3 data. The exception is for one of the ACS fields where, because of time restrictions, we have not added the F547M, and will instead use the ACS data for subtractions. We also get somewhat less integration time in [O III] and [S II] on this field in order to fit into the 10 orbit allocation. We request modest matching of FoV position angle to the four existing ACS/WFC fields to maximize overlap. We do not require exact matching and assume a +/-10 degree latitude and modulo 180 degrees field rotations to provide significant flexibility in scheduling the new observations. The new field has a preferred orientation to maximize coverage of known SNRs in the region between two of the existing fields, and we allow modulo 90 degrees and +/-10 degrees for scheduling flexibility. In Phase II, we have positioned the WFC3 FOVs within the ACS footprints to cover regions of most interest. Hence, the positions do not agree exactly with those of the archival ACS fields. A thee-step pattern is used for most of these data, to cover the gap and inprove cosmic ray rejection. (A two-step pattern is used on the one field with shorter exposures.) POSTFLASH values are set on the exposures, based partly on ETC estimates of background and based partly on our earlier experience with cy19 program 12513 in M83. ISM IN EXTERNAL GALAXIES Default false false false false false SUPPORTED GALAXY SPIRAL ARM J2000 J2000 GALAXY SPIRAL ARM J2000 J2000 GALAXY SPIRAL ARM J2000 J2000 GALAXY SPIRAL ARM J2000 J2000 GALAXY SPIRAL ARM J2000 J2000 ACS/WFC Imaging No No F502N ACS/WFC Imaging No No F502N ACS/WFC Imaging No No F502N ACS/WFC Imaging No No F502N ACS/WFC Imaging No No F502N ACS/WFC Imaging No No F658N WFC3/UVIS Imaging No No F673N WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No F673N WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No F673N WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No F673N WFC3/UVIS Imaging No No F547M WFC3/UVIS Imaging No No F673N WFC3/UVIS Imaging No No F547M POS-TARG DITHER 1.635 LINE false false 3 86.84 WFC3-UVIS-DITHER-LINE-3PT 1 false POS-TARG DITHER 2.145 LINE false false 2 86.84 WFC3-UVIS-DITHER-LINE 2 false The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13361 :visit-id "01" :proposal-version -1 :trans-version "20130502" :date "24-Jun-2013 14:00:02.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 3464928 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13361 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13361 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3094 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13361 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3206 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13361 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3206 :al-overhead-at-end 122 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) false 3 0 The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13361 :visit-id "02" :proposal-version -1 :trans-version "20130502" :date "24-Jun-2013 14:00:03.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1154992 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13361 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13361 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3096 :al-overhead-at-end 122 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :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 13361 :visit-id "03" :proposal-version -1 :trans-version "20130502" :date "24-Jun-2013 14:00:05.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2598720 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13361 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13361 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3096 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13361 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3205 :al-overhead-at-end 124 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :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 13361 :visit-id "04" :proposal-version -1 :trans-version "20130502" :date "24-Jun-2013 14:00:07.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2598720 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13361 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13361 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3096 :al-overhead-at-end 122 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) (Tic-Orbit :proposal-id 13361 :visit-id "04" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3205 :al-overhead-at-end 124 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3430 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 21.2. 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