0 Assigned ID: 242 ----- Attempting Submission 1 (Thu Mar 05 16:17:49 GMT 2020) ----- HST Phase I Proposal 242 successfully submitted. Receipt: # 242-1 ----- Attempting Submission 2 (Fri Mar 06 16:23:39 GMT 2020) ----- HST Phase I Proposal 242 successfully submitted. Receipt: # 242-2 ----- Attempting Submission 3 (Fri Mar 06 18:55:28 GMT 2020) ----- PARALLELS SIGNIFICANTLY EXTEND ALIGNMENT TIME PARALLELS SIGNIFICANTLY EXTEND ALIGNMENT TIME PARALLELS SIGNIFICANTLY EXTEND ALIGNMENT TIME PARALLELS SIGNIFICANTLY EXTEND ALIGNMENT TIME PARALLELS SIGNIFICANTLY EXTEND ALIGNMENT TIME Re-submitting after resolving the merging rule problem. -178636194 ----- Attempting Submission 1 (Mon Jun 15 21:42:51 GMT 2020) ----- ----- Attempting Submission 2 (Mon Jun 22 17:30:57 GMT 2020) ----- ----- Attempting Submission 3 (Thu Jul 16 15:23:09 GMT 2020) ----- Re-submmitting after solvign teh merging rule problem Digging into the mystery of the Galactic globular clusters M22 and NGC1851 We propose to collect deep near-infrared (NIR) images of two peculiar Galactic globular clusters (GGCs), NGC1851 and M22, to explore the properties of their multiple stellar populations. These GGCs display multiple sequences along the red-giant and sub-giant branches in ultraviolet-optical color-magnitude diagrams (CMDs), and spectroscopy confirmed they host multiple stellar populations with different light- and heavy-element abundances and total content of CNO. How these populations originated is still a mystery. We plan to solve this puzzle by using NIR photometry of low-mass main-sequence (MS) stars: these are brighter in the NIR regime, and the lower part of the MS is more sensitive to heavy and light-element abundances in NIR compared to optical colors. We plan to compare the observed NIR CMDs to theoretical models that include new bolometric corrections taking into account different chemical patterns to characterize the chemical composition and population ratio of the different sub-populations in the GGCs. The presence of chemical inhomogeneities in MS stars similar to those found in the giant stars through spectroscopy will confirm their primordial origin. Furthermore, we will derive the mass function of each stellar sub-population and investigate for the presence of differences. The new NIR data will be combined with archival HST data to derive accurate proper motions for MS stars and to characterize the kinematical properties of the different sub-populations. This analysis will shed light on the origin of multiple populations in these very peculiar GGCs. This work is preparatory for studies with JWST that will allow us to apply the same technique to farther GGCs. The first 2-orbit visit is dedicated to M22. We want to collect a series of F110W and F160W exposures of a field at about 5 arcmin from the cluster center that overlaps with previous ACS observations. The ACS parallel is appromitaly centered on the cluster center and overlaps with prevuous WFC3 observaitons. That is why we need an ORIENT constrain. The F160W exposures are at the beginning and at the end of the orbits to mitigate the Heliume line background contamination. To achieve this, we also use a Non-Interruptible Sequence. We dither about ~ 8-10 pixels by using Pos-targs. The second 3-orbit visit is dedicated to NGC1851. We want to collect deep and short F110W and F160W exposures of a field at about 5 arcmin from the cluster center that overlaps with previous ACS observations. The ACS parallel is appromitaly centered on the cluster center and overlaps with prevuous WFC3 observaitons. That is why we need an ORIENT constrain. The F160W exposures are at the beginning and at the end of the orbits to mitigate the Heliume line background contamination. To achieve this, we also use a Non-Interruptible Sequence. We dither about ~ 8-10 pixels by using Pos-targs. We also add two parallel ACS F606W observations since we have some time left and since these extra exposures could improve the S/N and the depth of the current ACS F606W, F814W photometric catalog for the center of NGC1851. The PI, Dr. Calamida, is the deputy branch manager of the WFC3 team. They are also the Science Lead of the photometric calibration group and the user support lead. The PI has a deep and extensive knowledge of the WFC3 IR detector and its calibration and will be able to exploit the data in the most efficient way. Co-Is Dr. Gennaro and Dr. Anderson collaborate with the WFC3 team to improving the data quality for the IR detector. Dr. Anderson is also the author of the software ePSF (Anderson et al. 2008) to perform Point-spread function (PSF) photometry on HST images. PSFs for the F110W and F160W will be also provided by Dr. Anderson. Dr. Calamida and Dr. M. Monelli both have extensive experience in photometry by using HST data and will thus be in charge of the data reduction and the artificial star tests. Artificial star tests are essential to characterize the photometric uncertainties, the systematic errors, and the completeness of the catalogs. Dr. Cassisi, Dr. Pietrinferni and Dr. Salaris are experts in derivation of stellar population properties from the comparison of observed color-magnitdue diagrams and theoretical models and will be in charge of these tasks. Dr. Mastrobuono Battisti and Dr. Zocchi are expert in numerical simulations to formulate predictions of structural and kinematical properties of globular clusters. They will produce simulations for the formation scenarios of M22 and NGC~1851 that we will compare with the observartions. This comparison should allow us to better understand the origin and evolutionary history of these very peculiar globular clusters. 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