----- Submission 1 (Fri May 13 13:45:03 GMT 2005) ----- Phase II Proposal 10528 (ngc4402_ph2) successfully submitted. ----- Submission 2 (Fri May 13 13:45:32 GMT 2005) ----- Assigned ID: 703 ----- Submission 1 (Sat Jan 22 00:58:32 GMT 2005) ----- Ram Pressure Stripping and Dense Cloud Ablation in the Virgo Spiral NGC 4402 We propose to image in BVI with HST ACS the highly inclined Virgo cluster spiral galaxy NGC 4402, which is an outstanding example of a galaxy undergoing stripping of its ISM by an ICM-ISM interaction. Ground-based images at 0.5" resolution appear to show active dust stripping, triggered star formation, and ablation of dense molecular clouds by the ICM wind. The near side of NGC 4402 contains the leading edge of interaction, giving us a relatively unobscured view of the processes which occur as the ICM wind impacts the ISM. High resolution HST B-I images of dust in NGC 4402 can reveal the fate of giant molecular clouds during a stripping event, including whether clouds above some size get left behind as the rest of the ISM is stripped from around them, how decoupled clouds become ablated by the ICM wind, and how the survival time varies with cloud mass. We will identify and estimate the ages of stars and star clusters in the stripped outer disk and halo, and from the spatial distributions of the younger objects, constrain the stripping history of the galaxy. Its proximity, orientation, stage of evolution, and direction of travel through the ICM make NGC 4402 an outstanding subject for a detailed HST study of ICM-ISM stripping. An in-depth study of this galaxy will provide new insight into the physical processes of ISM-ICM interactions and give us greater understanding of cluster galaxy evolution, both in Virgo and at higher redshifts.
We propose to image NGC~4402 with ACS WFC in 3 bands: F435W (Johnson B), F606W (Broad V), and F814W (Broad I). The 202"x202" field of view of the WFC is well-suited for imaging the entire active stripping region of NGC 4402. It includes all the HI and H-alpha emission detected in the galaxy, which has a total extent of 160. In order to detect enough star clusters to be statistically meaningful, we need to reach ~3 magnitudes fainter than the peak of the globular cluster luminosity function in each of BVI. This is about the same depth which will allow us to detect enough isolated young stars to enable mapping of distinct concentrations. Going ~0.5 magnitude deeper in V than the other bands, and given the various constraints of HST, we have settled on the following request. To reach magnitudes of F435W (B)=27.8, F606W (V)=27.5, and F814W (I)=26.3 with a signal-to-noise of 10 requires integration times of 120, 40 and 40 minutes respectively, according to the Exposure Time Calculator. At 2 exposures per orbit, there are about 40 minutes of exposure time per orbit, given 52 minutes of visibility time at the low declination of Virgo, minus 5-6 minutes for guide star acquisition time and 6.5 minutes of overhead. This corresponds to 5 orbits. GALAXIES 12 false 0.0 false false false false false SUPPORTED GALAXY SPIRAL J2000 12 26 7.5000 +13 06 46.00 J2000 ACS/WFC Imaging No No F435W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W POS-TARG DITHER 3.011 LINE false false 3 85.28 ACS-WFC-DITHER-LINE 1 false /.lsd/hugh/proposals/hst_cycle14/cycle14/OP-cache/ngc4402_ph2-v01.xml (Tic-Visit :proposal-id 10528 :visit-id "01" :proposal-version -1 :trans-version "20050323" :date "11-May-2005 22:56:49.0" :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 3410688 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10528 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10528 :visit-id "01" :orbit-number 1 :pcs-time 367 :si-vis-utilization 2884 :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 3251 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10528 :visit-id "01" :orbit-number 2 :pcs-time 367 :si-vis-utilization 2884 :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 3251 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10528 :visit-id "01" :orbit-number 3 :pcs-time 367 :si-vis-utilization 2883 :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 3251 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10528 :visit-id "01" :orbit-number 4 :pcs-time 367 :si-vis-utilization 2883 :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 3251 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10528 :visit-id "01" :orbit-number 5 :pcs-time 367 :si-vis-utilization 2884 :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 3251 :pcs-gap 0 ) true 5 0 /tmp/OPVisit57651.xml