Mass-To-Light Ratio Of Ly Alpha Emitters: Implications Of Ly Alpha Surveys At Redshifts Z = 5.7, 6.5, 7, And 8.8
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We present a simple, relatively model-independent method to interpret the galaxy number count data at z > 6. The only free parameter is a mass-to->observed light> ratio, M-h/L-band, where M-h refers to the total mass of the host halo, and L-band refers to the observed luminosity of the source. For narrow-band surveys, L-band is simply related to the intrinsic Ly alpha luminosity with a survival fraction of Ly alpha photons, alpha(esc). The mass-to->bolometric light>, M-h/L-bol, can also be found, once the metallicity and initial mass function of stellar populations are given. We find constraints on the mass-to-light ratio of Ly-alpha emitters from 5.7 < z < 8.8 of (M-h/L-bol) (alpha(esc)epsilon(1)/gamma)(-1) = 21 - 38, 14 - 26, and 9 - 17 for Z = 0, 1150, and 1 2 D, respectively, where E is the duty cycle and 7 - 2 is the local shape of the cumulative luminosity function. Therefore, Lya emitters are consistent with either starburst galaxies (M-h/L-bol similar to 0.1 - 1) for reasonable values of the Lya survival fraction, alpha(esc)epsilon(1)/gamma similar to 0.01 -0.05, or normal populations (M-h/L-bol similar to 10) if a good fraction of Ly alpha photons survived. We find no evidence for the end of reionization from current survey observations. The data are consistent with no evolution of intrinsic properties of Lya emitters or neutral fraction in the intergalactic medium. We also show that the lack of detections at z = 8.8 does not rule out the high-z galaxies being the origin of the excess near infrared background.