This is a re-submission: changed reference frame to GSC II. ----- Submission 1 (Tue May 09 18:19:25 GMT 2006) ----- Phase II Proposal 10843 (cgcg) successfully submitted. ----- Submission 2 (Fri May 12 00:05:05 GMT 2006) ----- Assigned ID: 188 ----- Submission 1 (Fri Jan 27 04:31:35 GMT 2006) ----- Deep Imaging of Extremely Metal-Poor Galaxies Conflicting evidence exists regarding whether the most metal-poor and actively star-forming galaxies in the local universe such as I Zw 18 contain evolved stars. We propose to help settle this issue by obtaining deep ACS/HRC U, narrow-V, I, and H-alpha images of nine nearby (z < 0.01) extremely metal-poor (12 + O/H < 7.65) galaxies selected from the Sloan Digital Sky Survey. These objects are only marginally resolved from the ground and appear uniformly blue, strongly motivating HST imaging. The continuum images will establish: 1.) If underlying populations of evolved stars are present, by revealing the objects' colors on scales ~10 pc, and 2.) The presence of any faint tidal features, dust lanes, and globular or super star clusters, all of which constrain the objects' evolutionary states. The H-alpha images, in combination with ground-based echelle spectroscopy, will reveal 1.) Whether the objects are producing "superwinds" that are depleting them of their metals; ground-based images of some of them indeed show large halos of ionized gas, and 2.) The correspondence of their nebular and stellar emission on scales of a few parsecs, which is important for understanding the "feedback" process by which supernovae and stellar winds regulate star formation. One of the sample objects, CGCG 269-049, lies only ~2 Mpc away, allowing the detection of individual red giant stars in it if any are present. We have recently obtained Spitzer images and spectra of this galaxy to determine its dust content and star formation history, which will complement the proposed HST observations. [NOTE: THIS PROPOSAL WAS REDUCED TO FIVE ORBITS, AND ONLY ONE OF THE ORIGINAL TARGETS, CGCG 269-049, AFTER THE PHASE I REVIEW]
We have been awarded five orbits to image the galaxy CGCG 269-049 using the Advanced Camera for Surveys. We will image the galaxy in the broad-band filters F330W, F550M, and F814W with the High Resolution Channel, and with the F658N filter using the Wide Field Channel. This is because the H-alpha emission of the galaxy may extend further than the HRC field of view. UNRESOLVED STELLAR POPULATIONS 12 false 0.0 false false false false false SUPPORTED GALAXY DWARF COMPACT STARBURST Sloan g = 15.87 SDSSJ121546.56+522313.9 J2000 12 15 46.5600 +52 23 13.90 J2000 ACS/HRC RampFilter No No FR656N ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F550M ACS/HRC Imaging No No F814W ACS/HRC RampFilter No No FR656N ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F550M ACS/HRC Imaging No No F814W ACS/HRC RampFilter No No FR656N ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F550M ACS/HRC Imaging No No F814W ACS/HRC RampFilter No No FR656N ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F550M ACS/HRC Imaging No No F814W ACS/HRC RampFilter No No FR656N ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F550M ACS/WFC Imaging No No F814W ACS/HRC RampFilter No No FR656N ACS/HRC RampFilter No No FR656N ACS/HRC RampFilter No No FR656N ACS/HRC RampFilter No No FR656N POS-TARG DITHER 0.198 LINE false false 2 44.28 ACS-HRC-DITHER-LINE 1 false POS-TARG DITHER 3.011 LINE false false 2 85.28 ACS-WFC-DITHER-LINE 2 false (Tic-Visit :proposal-id 10843 :visit-id "01" :proposal-version -1 :trans-version "20060322" :date "11-May-2006 18:04:47.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 3500704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10843 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Obset :proposal-id 10843 :visit-id "01" :obset-id "A1" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10843 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2842 :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 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10843 :visit-id "01" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2832 :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 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10843 :visit-id "01" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2812 :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 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10843 :visit-id "01" :orbit-number 4 :pcs-time 355 :si-vis-utilization 2832 :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 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10843 :visit-id "01" :orbit-number 5 :pcs-time 355 :si-vis-utilization 2842 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 5 0 /tmp/OPVisit21228.xml