High-resolution imaging of two lensed dusty star-forming galaxies

0 Assigned ID: 1208 ----- Attempting Submission 1 (Fri Apr 07 23:59:30 GMT 2017) ----- I am resubmitting the Phase II proposal with only the two approved orbits. To avoid confusing anyone, I have also modified the title, abstract, and proposal description so that they now only refer to a sample of two (rather than four) targets. Sorry again for not catching the duplication at the Phase I stage! -1282054022 ----- Attempting Submission 1 (Thu Jul 20 08:51:10 GMT 2017) ----- ----- Attempting Submission 2 (Thu Jul 27 06:59:31 GMT 2017) ----- High-resolution imaging of two lensed dusty star-forming galaxies Dusty star-forming galaxies (DSFGs) make significant contributions to the star formation history of the universe, but the same dust that powers their luminosity obscures much or all of the rest-UV and optical light that would allow easy study of their dynamical properties and evolutionary states. In this proposal, we request observations of two DSFGs that are among the brightest point sources in three-band mapping with the Atacama Cosmology Telescope (ACT), both of which show incontrovertible evidence of gravitational lensing. From HST imaging, we will extract information about the background sources and lens-plane structures and develop gravitational lens models, thereby gaining insights into the DSFGs' intrinsic sizes, morphologies, and gas masses and kinematics, and into the presence of substructure in the lens plane. This effort will be strengthened by the fact that both of our targets already have highly resolved mid-J CO mapping with the IRAM Northern Extended Millimeter Array; in these cases, each independent velocity channel serves as an independent probe of the lensing potential. We will use the F160W (~ H) filter on WFC3/IR to maximize sensitivity to the redshifted emission of the background DSFGs in our sample. We will use the standard WFC3-IR-DITHER-BOX-MIN pattern with four positions in order to optimally sample the PSF. The field of view of interest for each target will be well contained within the optimally sampled region. For both targets, there is good evidence for emission in this band from ground-based images. This evidence is clear for ACT-S-J2029+0120 (Roberts-Borsani et al. 2017), while there are hints of spatially extended emission in H-band imaging of ACT-S-J0116-0004. We estimated the range of surface brightness of the background lensed galaxy using H-band imaging from the VISTA Hemispheric Survey (VHS) for ACT-S-J0116-0004, and SDSS r-band and our own APO Ks-band image for ACT-S-J2029+0120. In each case, the lensed galaxy was modeled using Galfit (Peng et al. 2002, 2010). After the fit converged, the model was subtracted from the data and the residuals were used to estimate a mean and maximum surface brightness for the background galaxy. With estimated lens galaxy magnitudes in the range H = 14.6-17.6 and background galaxy surface brightnesses in the range 19.1-23.2 mag/arcsec^2 (Vega-relative), we need to ensure that the WFC3/IR images have adequate dynamic range, and are therefore using the STEP50 sequence with NSAMP = 11 to obtain eight 299.232s sub-exposures (via two executions of the four-position dither pattern). The resulting integration time per object (2393.856s) should yield a detection signal-to-noise ratio of >10 in a 5x5 pixel box for our faintest expected surface brightness value (23.2 mag/arcsec^2), based on the output of the WFC3/IR imaging ETC for a diffuse source with an elliptical galaxy spectrum and nominal background conditions. This depth will ensure high signal-to-noise over many square arcseconds of the background sources, as required by the proposal's scientific goals, and will allow even higher-S/N characterization of the main lensing galaxies and any satellites in their vicinities. Galaxies and the IGM 6 false false false false false false SUPPORTED GALAXY GRAVITATIONAL LENS HIGH REDSHIFT GALAXY Coordinates based on NOEMA imaging. The star nearest to the DSFG is farther away than our adopted dither pattern steps, so image persistence will not be a problem in the vicinity of our science target. J2000 J2000 J = 18.4, H = 17.6, Ks = 17.2 GALAXY GRAVITATIONAL LENS HIGH REDSHIFT GALAXY Target coordinates based on NOEMA imaging. The star nearest to the DSFG is farther away than our adopted dither pattern steps, and the nearest very bright star (2MASS J20295151+0120417, with J = 10.29, H = 10.032, K = 10.0) is 62" away near the edge of the FOV, so image persistence will not be a problem in the vicinity of our science target. J2000 J2000 J = 15.5, H = 14.6, Ks = 14.3 WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1

false

1501138574781 /private/var/folders/42/p5ksmrgn60l7hqm6xc4zzdxc0000gn/T/OPVisit5591675555539248560.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15160 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "27-Jul-2017 02:56:13.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 1671264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15160 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15160 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 671 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) true 1 0 1501138577163 /private/var/folders/42/p5ksmrgn60l7hqm6xc4zzdxc0000gn/T/OPVisit5481522268976666892.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15160 :visit-id "02" :proposal-version -1 :trans-version "20170613" :date "27-Jul-2017 02:56:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 1671264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15160 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15160 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2868 :al-overhead-at-end 0 :internal-dur-at-end 671 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3202 :pcs-gap 0 ) true 1 0