Very Blue UV-Continuum Slopes of Star-Forming Galaxies at z ～7 and the Evolution to z ～ 2-4

摘要

The new WFC3/IR instrument on HST enables us to survey the sky in the near-IR 40× more efficiently than ever before, permitting enormous strides in the identification and characteri-zation of galaxies at z≥ 7. Already, deep wide-area observations exist over some ～52 arcmin~2in the HUDF09 + FRS fields. With these data, we have been able to identify more than 60 z～7 galaxy candidates, more than 40 z～8 galaxy candidates, and even some possible z～9 galaxies over a 3 magnitude range in luminosity, adding significantly to the 20 - 30 z～7 candidates known prior to WFC3/IR. One of the most interesting observables to examine in these high redshift galaxies are the UV-continuum slopes. since it provides us with constraints on the dust content, metallicities. ages, and possibly escape fractions of low-mass star-forming galaxies at very early times. Here. I provide a brief summary of our findings on the UV-continuum slopes β of z ～ 7 galaxies from the early ultra-deep WFC3/IR data over the HUDF.