0 Assigned ID: 4599 ----- Attempting Submission 1 (Wed May 24 20:28:09 GMT 2023) ----- HST Phase I Proposal 4599 successfully submitted. Receipt: # 4599-1 ----- Attempting Submission 2 (Wed May 24 21:45:27 GMT 2023) ----- HST Phase I Proposal 4599 successfully submitted. Receipt: # 4599-2 ----- Attempting Submission 3 (Wed May 24 22:05:15 GMT 2023) ----- We propose to leverage the HST archive in search for faint, close-in companions to all known ultracool dwarfs (UCD) previously imaged with HST with a post-processing technique. Our scientific goals are to (1) measure a robust close-in UCD multiplicity fraction at high angular resolution, (2) constrain the true peak of the UCD binary separation distribution, and (3) estimate the mass ratio distribution of the UCD population. To achieve unprecedented angular resolution The double-PSF technique has a proven record of detecting sub-pixel binaries, and it is adaptable and flexible across different instruments, pixel scales, and exposure times since it uses an empirical PSF from the image itself. Our proposal will effectively amount to be the largest high angular resolution survey ever carried out for UCD and revisit crucial measurements to piece together our understanding of brown dwarf formation. Prof. Daniella Bardalez Gagliuffi (PI, Amherst College) is an expert in the characterization of brown dwarf binary systems through near-infrared imaging and spectroscopy, as well as the study of ultracool populations to identify their formation mechanisms. She has experience with imaging photometry of binary systems (Bardalez Gagliuffi et al. 2015, AJ, 150, 163) following their identification as spectral binaries from unresolved, near-infrared spectra (Bardalez Gagliuffi et al. 2014, ApJ, 794, 173; Bardalez Gagliuffi et al. 2018, ApJ, 854, 101). Dr. Bardalez Gagliuffi also has expertise in population studies of ultracool dwarfs (Bardalez Gagliuffi et al. 2019, ApJ, 883, 205) and recently characterized one of the coldest brown dwarfs with HST/WFC3 photometry (Bardalez Gagliuffi et al. 2020, ApJ, 895, 145), as a Co-I on a successful HST program (GO 15468). Dr. Bardalez Gagliuffi will manage the program, lead the multiplicity analysis, interpretation of the data, and the publication efforts. Mr. Matthew De Furio (Co-PI, University of Michigan) is an expert in the identification of binary systems, particularly through the double-PSF technique. Mr. De Furio is the creator and developer of the double-PSF technique and has successfully applied it on archival HST images to identify binaries in the Orion Nebula Cluster (De Furio et al. 2019, ApJ, 886, 95). He is preparing a publication where this technique is applied on ultracool dwarfs (De Furio et al., in prep.). Mr. De Furio will lead the adaptation and application of the double-PSF technique to WFC3 and WFPC2 images, preparation of the code for publication, and the publication efforts. Dr. Clemence Fontanive (Co-I, University of Montreal) is an expert in spaced-based observations of extremely cold brown dwarfs and, as well as survey statistics and binary properties of substellar populations. She has extensive experience with astrometric and photometric HST observations of nearby late-type T and Y dwarfs (Fontanive et al. 2018, MNRAS, 479, 2702; Fontanive et al. 2021, MNRAS, 501, 911) and has three successful HST programs targeting low-mass brown dwarfs (GO 14686, GO 15201, GO 16229). Dr. Fontanive will contribute to the analysis and interpretation of the data, and support with publications of results. Prof. Michael Meyer (Co-I, University of Michigan) has over 30 years experience in infrared astronomy and instrumentation, and specific research expertise in star and planet formation, exoplanet discovery and characterization, and demographic studies of the initial mass function, multiple star, and exoplanet populations (e.g., Meyer et al. 2018, A&A, 612, 3; Meyer et al. 2008, ApJ, 673, 181).. He also has extensive experience in development of ground- and space-based instrumentation, including both the NIRCam and NIRISS instruments for the James Webb Space Telescope as well as high contrast imaging systems and spectrographs for 6-12 meter telescopes and next generation extremely large telescopes. Dr. Trent Dupuy (Co-I, University of Edinburgh) is an expert on ultracool dwarf binary observations both with HST and adaptive optics (e.g., Dupuy & Liu 2017 ApJS, 231, 15), including PSF-fitting of archival HST imaging using various imagers (WFPC2, NICMOS, ACS, WFC3). He supervised the student who built some of the PSF fitting analysis that was further developed and expanded by co-PI De Furio (Garcia, Dupuy et al. 2015, ApJ, 804, 65). He has extensive experience characterizing low-mass stars and brown dwarfs and helps maintain one of the largest community resources in this area (The UltracoolSheet has 3000+ objects and 1000+ references; https://doi.org/10.5281/zenodo.4169084). Stellar Physics and Stellar Types 0 Regular false false false false false false SUPPORTED