Color selection of z > 9.5 galaxies (Section 3.2). Shown are the J ₁₂₅ − H ₁₆₀ colors of different types of galaxies as a function of their redshift. Star-forming galaxies are shown as solid blue lines. The lighter blue spectral energy distribution (SED) is reddened by E( B − V) =0.15 mag using a Calzetti et al. (2000) dust law. As the Lyα absorption due to intergalactic neutral hydrogen shifts into the J ₁₂₅ band, galaxies start to exhibit progressively redder colors beyond z ~ 8. A selection with J ₁₂₅ − H ₁₆₀ > 1.2 thus identifies galaxies at z 9.5. Strong Balmer and 4000 Å breaks in evolved z ~ 3 galaxies, combined with some dust obscuration can also result in very red J ₁₂₅ − H ₁₆₀ colors. The dashed lines correspond to more evolved galaxies dominated by progressively older stellar populations from the library of Coleman et al. (1980) as well as a 1 Gyr old single stellar population (SSP) from the library of Bruzual & Charlot (2003). Spitzer IRAC data provide a way to separate these different populations at intermediate and very high redshifts (see the text and Figure  3).