This phase2 file converts the previously allocated ACS time into WFPC2 observations covering 4 orbits. ----- Submission 1 (Thu May 18 16:01:35 GMT 2006) ----- ----- Attempting Submission 2 (Wed May 09 16:26:13 GMT 2007) ----- Assigned ID: 427 ----- Submission 1 (Fri Jan 27 21:29:09 GMT 2006) ----- Morphology of a most spectactular Spitzer selected galaxy By using ground based sub-millimeter observations to followup Spitzer-selected galaxies, we have discovered a starburst dominated hyperluminous infrared galaxy. A mid-infrared spectrum obtained with Spitzer-IRS provides a redshift of z=1.325, which has been subsequently confirmed using both NIR spectroscopy at Keck, and sub-mm spectroscopy with IRAM and the CSO. By combining the Spitzer and ground based sub-mm data, we measure an integrated IR luminosity of 4 x 10^13 Lsun. This is the only such object found in the 9 square degree NDWFS survey, and hence is incredibly rare. The only other dusty galaxies this bright show strong evidence of AGN activity, but this source does not. One reason this object could be so bright is due to lensing, and indeed a foreground source spectroscopically confirmed at z=1.034 seems directly aligned with the target. However it is unlikely that the geometry of this galaxy-galaxy lensing system could support an amplification more than a factor of a few. Our IRAC images reveal very faint and red satellite systems near our target, hence another possibility is that the galaxy is so luminous because of merging induced star-formation activity. Morphology is the best way to discriminate between these hypotheses, and hence HST observations are essential since the scales on which the merging or lensing are occuring are much smaller than what can be resolved from the ground.
Simple 2 orbit observation (1 with ACS, one with NICMOS) to investigate the morphology of a unique, luminous, Spitzer selected galaxy. Based on previous experience with high-redshift IR luminous galaxies, we request LOWSKY conditions, and want to avoid the SAA. There is no constraint between when the ACS and NICMOS orbits are scheduled. ACS observations: We use a simple 4 point dither pattern (BOX). The object is centered in the middle of one the two ACS chips to ensure we get it and its immediate environment well away from the interchip gap. Since the 4 points should be sufficient to remove cosmic-rays, we set CR-SPLIT to "no". 4x437s exposures are used to fill the available time while avoiding the low-sky cutoff. NICMOS observations: We use the NIC2 aperture and a standard spiral dither pattern, with a spacing of 0.6375 arcseconds (8.5 pixels). We found that by setting NSAMP=6 and SAMP-SEQ=SPARS128, we could fill up most of the orbit while still avoiding the low-sky limit. We note that NSAMP=19,SPARS32 would result in 120 extra seconds of exposure time, but at the expense of potentially higher noise given the increased readout frequency. To avoid the SAA, we used (on advice from STSCI), the "GS ACQ SCENARIO: BASE1TNS" setting. Note: The nearest GSC2.2 guidestar (N13322216746) to the object we are studying does not overlap with our most recent I-band imaging. Likely proper motion is to blame. Although perhaps difficult to manage, the scientific impact of these observations would be strongest if made during the early June 2006 window, rather than waiting until February 2007 when it opens again. This would allow us to immediately publish it and other followup data we have collected using ground-based telescopes this past semester. UNRESOLVED STELLAR POPULATIONS 12 false 0.0 false false false false false false SUPPORTED GALAXY GRAVITATIONAL LENS STARBURST ULTRALUMINOUS IR GAL I=21, K=17 (Vega) BOOTES59 SHARC59 J2000 14 28 24.0700 +35 26 19.40 J2000 NIC2 Imaging No No F160W ACS/WFC Imaging No No F814W POS-TARG DITHER 0.559017 LINE 0.559017 false false 143.130096 4 26.56505 WFPC2-BOX 1 false POS-TARG DITHER DITHER 0.6735 NIC-XSTRIP-DITH false true 4 0 POS-TARG NIC-SPIRAL-DITH 0 2 false /private/tmp/OPVisit50792.xml This updated phase II converts the ACS observation originally planned for this target into a WFPC2 observation. We choose the PC camera for resolution, and apply a standard box-dither pattern. Each of the four orbits are identical except for modest (11 pixel on the PC CCD) shift to further mitigate bad pixel issues. Orientation is not a concern since we are concerned with the circular area within 15 arcsec of the target. Also, the PC coverage is more than sufficient to cover the NICMOS image already obtained as part of this project. 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