Mass-to-light ratio of Ly alpha emitters: implications of Ly alpha surveys at redshifts z=5.7, 6.5, 7 and 8.8

作者：Fernandez Elizabeth R^*; Komatsu Eiichiro

来源：Monthly Notices of the Royal Astronomical Society, 2008, 384(4): 1363-1376.

DOI：10.1111/j.1365-2966.2007.12533.x

• galaxies : high-redshift
• cosmology : observations
• cosmology : theory
• early Universe
• infrared : galaxies

Using a simple method to interpret the luminosity function of Ly alpha emitters, we explore properties of Ly alpha emitters from 5.7 <= z <= 8.8 with various assumptions about metallicity and stellar mass spectra. We constrain 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 deduced, once the metallicity and stellar mass spectrum are given. The inferred M-h/L-bol is more sensitive to metallicity than to the mass spectrum. We find the following constraints on a mass-to-light ratio of Ly alpha emitters from 5.7 <= z <= 7: (M-h/L-bol)(alpha(esc)epsilon(1/gamma))(-1) = 21-38, 14-26 and 9-17 for Z = 0, 1/50 and 1 Z(circle dot), respectively, where epsilon is the 'duty cycle' of Ly alpha emitters and gamma similar to 2 is a local slope of the cumulative luminosity function, N(> L) proportional to L-gamma, to which the current data are sensitive. Only weak lower limits are obtained for z = 8.8. Therefore, Ly alpha emitters are consistent with either starburst galaxies (M-h/L-bol similar to 0.1-1) with a smaller Ly alpha 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, alpha(esc)epsilon 1/gamma similar to 0.5-1. We find no evidence for the end of reionization in the luminosity functions of Ly alpha emitters discovered in the current Ly alpha surveys, including recent discovery of one Ly alpha emitter at z = 7. The data are consistent with no evolution of intrinsic properties of Ly alpha emitters or neutral fraction in the intergalactic medium up to z = 7. No detection of sources at z = 8.8 does not yield a significant constraint yet. We also show that the lack of detection at z = 8.8 does not rule out the high-z galaxies being the origin of the excess near-infrared background.

• 出版日期2008-3-11