0 Assigned ID: 4899 ----- Attempting Submission 1 (Tue Nov 07 00:24:33 GMT 2023) ----- HST Phase I Proposal 4899 successfully submitted. Receipt: # 4899-1 ----- Attempting Submission 2 (Sun Nov 12 16:53:16 GMT 2023) ----- Submission of repeat visits 51-55, after HOPR. -1348849212 ----- Attempting Submission 1 (Thu Feb 15 22:35:46 GMT 2024) ----- ----- Attempting Submission 2 (Fri Mar 21 17:06:42 GMT 2025) ----- The globular clusters of Dragonfly 44 Ultra diffuse galaxies (UDGs) are large, low surface brightness objects that were first identified in significant numbers in the Coma cluster. One of the most striking aspects of the UDGs in Coma is that they appear to host many globular clusters, up to 7x the number that is expected from their luminosities. The record holder is Dragonfly 44, one of the largest and best-studied UDGs, with 74 clusters found in 3 orbit-depth HST data. The high globular cluster counts have been interpreted as evidence for overly massive dark matter halos, and also as an important clue to understand their formation. However, recently these results have been thrown in doubt, as a re-analysis of the same HST data found only 18 clusters in Dragonfly 44 and similar downward revisions for other UDGs. A special session at a UDG conference this summer indicated that these large differences can be traced to different assumptions and methodologies that are applied to relatively shallow data. Here we propose to obtain a definitive measurement of the globular cluster luminosity function in Dragonfly 44, making use of the superb long pass filters of WFC3/UVIS. A 13-orbit white light UVIS image reaches the equivalent point source depth of a 30-orbit ACS/F606W image, and we show with simulated data that we can securely identify clusters down to ~2 magnitudes below the peak of the luminosity function. This program will resolve an ongoing dispute that is hampering progress in the study of UDGs. It came to the fore in the summer of 2023, after the most recent regular proposal deadline. In visits 1-6 the galaxy will be observed with 4 dithered exposures in 2 orbits per visit. Visit 7 is a single orbit, with 2 exposures. In the reduction all 13 orbits, and 26 exposures, will be combined, so having 1 visit with only 2 exposures should not impact the quality of the reduction. (The alternative was to have 5 visits with 2 orbits and 1 visit with 3 orbits, but that could impact scheduling flexibility.) Visits 1-3 use F200LP, and visits 4-7 use F350LP. The size of the object is 10'', and the dither box size is 25''. This makes it possible to construct and subtract the local background. The sampling of the PSF will be fine, as each of the 7 visits will have a random subpixel offset with respect to the others. No post-flash is needed as the F200LP and F350LP filters provide more than enough counts per exposure. UPDATE for visits 51-55: Visits 1-7 all suffered from the same anomaly, loss of lock after the first exposure. The probability of this failure may have been increased due to the large 25'' dithers between exposures. Therefore, for repeat visits 51-55, the dither pattern was changed to the standard small offsets of WFC3-UVIS-DITHER-BOX. We are only using F350LP in these repeat observations, to ensure that we have a sufficient number of exposures in the same filter, should the anomaly re-occur. (F200LP and F350LP have to be drizzled separately, as they have slightly different sensitivity curves beyond 350 nm). The PI and the co-Is discovered Dragonfly 44 and wrote several of the key papers in this proposal, including the study that found 74 globular clusters. Co-I Danieli also obtained HST imaging for another globular cluster-rich UDG, and wrote a paper on that object. All the co-Is have substantial experience with analyzing HST data. Co-I Romanowsky is an expert on globular clusters, and Roberto Abraham developed several widely-used methods in galaxy modeling and morphology. While we are clearly representatives of one "camp" we are motivated by finding out the truth - Saifollahi et al. may well be right with their lower counts, and only the kind of data that are proposed here will provide a definitive answer. Galaxies 6 false false false false false false SUPPORTED GALAXY DWARF SPHEROIDAL YES J2000 J2000 WFC3/UVIS Imaging No No F200LP WFC3/UVIS Imaging No No F350LP POS-TARG BACKGROUND 25 LINE 25 false true 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1 false POS-TARG BACKGROUND 35 LINE false true 2 46.84 WFC3-UVIS-DITHER-LINE 2 false POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 3 false The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740149905000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "01" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:28.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740161239000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "02" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:29.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "02" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740172574000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "03" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:29.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "03" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740880910000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "04" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:30.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "04" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740665555000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "05" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:30.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "05" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "05" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. /private/var/folders/1h/tyyykvzs7fb_ym_0qdtzf6740000gn/T/OPVisit6732940182250650543.xml HOPR repeat of visit 01. (Tic-Visit :proposal-id 17598 :visit-id "51" :proposal-version -1 :trans-version "20241216" :date "21-Mar-2025 13:05:23.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "51" :obset-id "51" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "51" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "51" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. /private/var/folders/1h/tyyykvzs7fb_ym_0qdtzf6740000gn/T/OPVisit18147639019443398053.xml HOPR repeat of visit 02. (Tic-Visit :proposal-id 17598 :visit-id "52" :proposal-version -1 :trans-version "20241216" :date "21-Mar-2025 13:05:23.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "52" :obset-id "52" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "52" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "52" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. /private/var/folders/1h/tyyykvzs7fb_ym_0qdtzf6740000gn/T/OPVisit2050527681443731434.xml HOPR repeat of visit 03 (Tic-Visit :proposal-id 17598 :visit-id "53" :proposal-version -1 :trans-version "20241216" :date "21-Mar-2025 13:05:23.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "53" :obset-id "53" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "53" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "53" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. /Users/dokkum/RUNS/Prop/hst_cyc31m/df44/phase2/OP-cache/df44_hopr-v54.xml HOPR repeat of visit 04. (Tic-Visit :proposal-id 17598 :visit-id "54" :proposal-version -1 :trans-version "20241216" :date "21-Mar-2025 12:53:14.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "54" :obset-id "54" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "54" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "54" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. /Users/dokkum/RUNS/Prop/hst_cyc31m/df44/phase2/OP-cache/df44_hopr-v55.xml HOPR repeat of visit 05. (Tic-Visit :proposal-id 17598 :visit-id "55" :proposal-version -1 :trans-version "20241216" :date "21-Mar-2025 12:53:17.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "55" :obset-id "55" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "55" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "55" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740676923000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "06" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:31.0" :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 1154976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "06" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) (Tic-Orbit :proposal-id 17598 :visit-id "06" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.0. CASM was run in Phase II mode. 1740892196000 235.75793853946197 (Tic-Visit :proposal-id 17598 :visit-id "07" :proposal-version -1 :trans-version "20240604" :date "14-Jun-2024 12:20:31.0" :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 577488 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17598 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17598 :visit-id "07" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2652 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3032 :pcs-gap 0 ) true 1 0