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Arxiv: All the Little Things in Abell 2744: >1000 Gravitationally Lensed Dwarf Galaxies at z=0-9 from JWST NIRCam Grism Spectroscopy Published: 10/2/2024 9:00:00 PM Updated: 10/2/2024 9:00:00 PM

Paper abstract: Dwarf galaxies hold the key to crucial frontiers of astrophysics, however,their faintness renders spectroscopy challenging. Here we present the JWSTCycle 2 survey, All the Little Things (ALT, PID 3516), which is designed toseek late-forming Pop III stars and the drivers of reionization at z~6-7.ALT has acquired the deepest NIRCam grism spectroscopy yet (7-27 hr), at JWST'smost sensitive wavelengths (3-4 \mum), covering the powerful lensing clusterAbell 2744. Over the same 30 arcmin^2, ALT's ultra-deep F070W+F090W imaging(~30 mag) enables selection of very faint sources at z>6. We demonstratethe success of ALT's novel ``butterfly" mosaic to solve spectral confusion andcontamination, and introduce the ``Allegro" method for emission lineidentification. By collecting spectra for every source in the field of view,ALT has measured precise (R~1600) redshifts for 1630 sources atz=0.2-8.5. This includes one of the largest samples of distant dwarfgalaxies: [1015, 475, 50] sources less massive than the SMC, Fornax, andSculptor with \log(M_{*}/M_{\odot})<[8.5, 7.5, 6.5]. We showcase ALT'sdiscovery space with: (i) spatially resolved spectra of lensed clumps ingalaxies as faint as M_{\rm{UV}}~-15; (ii) large-scale clustering --overdensities at z=[2.50, 2.58, 3.97, 4.30, 5.66, 5.77, 6.33] hosting massivegalaxies with striking Balmer breaks; (iii) small-scale clustering -- a systemof satellites around a Milky Way analog at z~6; (iv) spectroscopicallyconfirmed multiple images that help constrain the lensing model underlying allscience in this legacy field; (v) sensitive star-formation maps based ondust-insensitive tracers such as Pa\alpha; (vi) direct spectroscopicdiscovery of rare sources such as AGN with ionized outflows. These resultsprovide a powerful proof of concept for how grism surveys maximize thepotential of strong lensing fields.