Star Formation at at z = 2.481 in the Lensed Galaxy SDSS J1110+6459. II. What is Missed at the Normal Resolution of the Hubble Space Telescope?

• Main Authors: Rigby, J. R. (Author), Johnson, T. L. (Author), Sharon, K. (Author), Whitaker, K. (Author), Gladders, M. D. (Author), Florian, M. (Author), Lotz, J. (Author), Wuyts, E. (Author), Bayliss, Matthew B (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: The American Astronomical Society, 2017-12-21T20:43:32Z.
• Subjects: Article
• Online Access: Get fulltext

 For lensed galaxy SGAS J111020.0+645950.8 at redshift z = 2.481, which is magnified by a factor of 28 ± 8, we analyze the morphology of star formation, as traced by rest-frame ultraviolet emission, in both the highly magnified source plane and simulations of how this galaxy would appear without lensing magnification. Were this galaxy not lensed, but rather drawn from a Hubble Space Telescope deep field, we would conclude that almost all its star formation arises from an exponential disk (Sérsic index of 1.0 ± 0.4) with an effective radius of r[subscript e]=2.7 ± 0.3 measured from two-dimensional fitting to F606W using Galfit, and r[subscript e]=1.9 ± 0.1 kpc measured by fitting a radial profile to F606W elliptical isophotes. At the normal spatial resolution of the deep fields, there is no sign of clumpy star formation within SGAS J111020.0+645950.8. However, the enhanced spatial resolution enabled by gravitational lensing tells a very different story; much of the star formation arises in two dozen clumps with sizes of r = 30-50 pc spread across the 7 kpc length of the galaxy. The color and spatial distribution of the diffuse component suggests that still-smaller clumps are unresolved. Despite this clumpy, messy morphology, the radial profile is still well-characterized by an exponential profile. In this lensed galaxy, stars are forming in complexes with sizes well below 100 pc; such sizes are wholly unexplored by surveys of galaxy evolution at 1 < z < 3.