Discovery Of Lyman Break Galaxies At Z Similar To 7 From The Zfourge Survey




Tilvi, Vithal
Papovich, Casey
Tran, K. V. H.
Labbe, I.
Spitler, L. R.
Straatman, C. M. S.
Persson, S. E.
Monson, A.
Glazebrook, K.
Quadri, R. F.

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Star-forming galaxies at redshiftsz > 6 are likely responsible for the reionization of the universe, and it is important to study the nature of these galaxies. We present three candidates for z similar to 7 Lyman break galaxies (LBGs) from a 155 arcmin(2) area in the CANDELS/COSMOS field imaged by the deep FourStar Galaxy Evolution (zFourGE) survey. The FourStar medium-band filters provide the equivalent of R similar to 10 spectroscopy, which cleanly distinguishes between z similar to 7 LBGs and brown dwarf stars. The distinction between stars and galaxies based on an object's angular size can become unreliable even when using Hubble Space Telescope imaging; there exists at least one very compact z similar to 7 candidate (FWHM similar to 0.5-1 kpc) that is indistinguishable from a point source. The medium-band filters provide narrower redshift distributions compared with broadband-derived redshifts. The UV luminosity function derived using the three z similar to 7 candidates is consistent with previous studies, suggesting an evolution at the bright end (MUV similar to -21.6 mag) from z similar to 7 to z similar to 5. Fitting the galaxies' spectral energy distributions, we predict Ly alpha equivalent widths for the two brightest LBGs, and find that the presence of a Ly alpha line affects the medium-band flux thereby changing the constraints on stellar masses and UV spectral slopes. This illustrates the limitations of deriving LBG properties using only broadband photometry. The derived specific star-formation rates for the bright LBGs are similar to 13 Gyr(-1), slightly higher than the lower-luminosity LBGs, implying that the star-formation rate increases with stellar mass for these galaxies.



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Tilvi, Vithal, C. Papovich, K-VH Tran, I. Labb�, L. R. Spitler, C. M. S. Straatman, S. E. Persson et al. "Discovery of Lyman Break Galaxies at z~ 7 from the zFourGE Survey." The Astrophysical Journal, Vol. 768, No. 1 (May., 2013): 56.