The Merian survey: design, construction, and characterization of a filter set optimized to find dwarf galaxies and measure their dark matter halo properties with weak lensing
Johnson, Sean D.; Cai, Zheng; Lin, Xiaojing; Li, Mingyu; Leauthaud, Alexie; Li, Ting S.; Kelvin, Lee S.; Wasleske, Erik J.; Danieli, Shany; Peter, Annika H. G.; Huang, Song; Lupton, Robert; Li, Jiaxuan; Kado-Fong, Erin; Medina, Gustavo E.; Luo, Yifei; Greene, Jenny; Blanco, Diana; Wick, Joseph; Mintz, Abby; Guan, Runquan; Baldassare, Vivienne; Brooks, Alyson; Banerjee, Arka; Bhattacharyya, Joy; Chen, Xinjun; Gunn, Jim; Mace, Charlie; Read, Justin; Rosado, Rodrigo Córdova; Seifert, Allen
United States, China, Canada, India, United Kingdom
Abstract
The Merian survey is mapping ~ 850 deg2 of the Hyper Suprime-Cam Strategic Survey Program (HSC-SSP) wide layer with two medium-band filters on the 4-m Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory, with the goal of carrying the first high signal-to-noise (S/N) measurements of weak gravitational lensing around dwarf galaxies. This paper presents the design of the Merian filter set: N708 (λc = 7080 Å, Δλ = 275 Å) and N540 (λc = 5400 Å, Δλ = 210 Å). The central wavelengths and filter widths of N708 and N540 were designed to detect the $\rm H\alpha$ and $\rm [OIII]$ emission lines of galaxies in the mass range $8\lt \rm \log M_*/M_\odot \lt 9$ by comparing Merian fluxes with HSC broad-band fluxes. Our filter design takes into account the weak lensing S/N and photometric redshift performance. Our simulations predict that Merian will yield a sample of ~ 85 000 star-forming dwarf galaxies with a photometric redshift accuracy of σΔz/(1 + z) ~ 0.01 and an outlier fraction of $\eta =2.8~{{\ \rm per\ cent}}$ over the redshift range 0.058 < z < 0.10. With 60 full nights on the Blanco/Dark Energy Camera (DECam), the Merian survey is predicted to measure the average weak lensing profile around dwarf galaxies with lensing S/N ~32 within r < 0.5 Mpc and lensing S/N ~90 within r < 1.0 Mpc. This unprecedented sample of star-forming dwarf galaxies will allow for studies of the interplay between dark matter and stellar feedback and their roles in the evolution of dwarf galaxies.