There is growing observational and theoretical evidence to suggest that Ultra-Luminous X-ray sources (ULX) form preferentially in low metallicity environments. Here we propose a survey of 27 nearby (< 30Mpc) star-forming Extremely Metal Poor Galaxies (Z<5% solar). There are almost no X-ray observations of such low abundance galaxies (3 in the Chandra archive). These are the most metal-deficient galaxies known, and a logical place to find ULX if they favor metal-poor systems. We plan to test recent population synthesis models which predict that ULX should be very numerous in metal-poor galaxies. We will also test the hypothesis that ULX form in massive young star clusters, and ask for HST time to obtain the necessay imaging data.

The goal of the HST portion of this program is to obtain broad-band imaging in several filters in order to detect and constrain ages of star clusters in the ultra metal-poor galaxy sample studied here. Each galaxy is observed for a single orbit. Because many of the galaxies are quite small on the sky, we prefer to use sub-arrays with the WFC3, which allow faster readout times. We have selected pre-defined subarrays matched to the extent of each target. In a few cases we ask for loose orientation constraints to make sure that the outer portions of the galaxy are observed. The number of exposures that fit within an orbit depends primarily on the subarray. For the smallest subarray, we are able to get 8 exposures in an orbit, and here we include U band imaging, in addition to B, V, and I filters, which allows more quantitative determinations for the ages of star clusters. Galaxies observed with larger subarrays are observed in B, V, and I. We prefer the broad V (606W) over the narrower V filters that are available. This filter allows (nebular) line emission through, placing these clusters in a different portion of the 2 color diagram, which can be used as an additional age constraint, since objects with strong line emission have ages younger than ~10 Myr. We use a very basic dither strategy. We take 2 exposures per filter, and use POS-TARGs to move by 2 pixels in x and y. The goal of dithering here is not to improve resolution or to step over any gap, but rather for cosmic ray rejection and the rejection of hot pixels. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 12 false 0.0 0.0 false false false false false false SUPPORTED GALAXY STARBURST J2000 01 13 39.4000 +00 52 28.00 J2000 GALAXY STARBURST J2000 14 17 1.4000 +43 30 5.00 J2000 GALAXY STARBURST J2000 04 05 20.3530 -36 49 0.72 J2000 GALAXY STARBURST J2000 12 38 40.0000 +32 46 1.00 J2000 GALAXY STARBURST J2000 08 12 39.5290 +48 36 45.36 J2000 GALAXY STARBURST J2000 08 59 46.9200 +39 23 5.60 J2000 GALAXY STARBURST J2000 08 25 55.5220 +35 32 31.96 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 GALAXY STARBURST J2000 00 00 0.0000 +00 00 0.00 J2000 WFC3/UVIS Imaging No No F336W The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "01" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 13:59:47.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2903 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "03" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:01:31.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2977 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3310 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "05" :proposal-version -1 :trans-version "20080807" :date "23-Oct-2009 12:34:15.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3065 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3398 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "06" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:17:33.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2977 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3310 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "08" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:20:07.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2887 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "09" :proposal-version -1 :trans-version "20080807" :date "23-Oct-2009 12:34:18.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "09" :obset-id "09" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "09" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3181 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3517 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "10" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:37:04.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "10" :obset-id "10" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "10" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3195 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "11" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:39:31.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "11" :obset-id "11" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "11" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2903 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "12" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:43:04.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "12" :obset-id "12" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "12" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3119 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "14" :proposal-version -1 :trans-version "20080807" :date "23-Oct-2009 12:34:21.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "14" :obset-id "14" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "14" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2977 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3310 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "16" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:47:31.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "16" :obset-id "16" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "16" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2903 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "17" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:48:42.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "17" :obset-id "17" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "17" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2903 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3236 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "18" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:52:47.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "18" :obset-id "18" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "18" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3017 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3351 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "19" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:55:01.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "19" :obset-id "19" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "19" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2917 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3251 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "20" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:57:06.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "20" :obset-id "20" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "20" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3119 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "21" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 14:59:57.0" :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 844944 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "21" :obset-id "21" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "21" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2933 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12018 :visit-id "22" :proposal-version -1 :trans-version "20080807" :date "22-Oct-2009 15:01:54.0" :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 36624 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12018 :visit-id "22" :obset-id "22" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12018 :visit-id "22" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3119 :al-overhead-at-end 38 :internal-dur-at-end 79 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3453 :pcs-gap 0 ) true 1 0