Constraining the luminosity function of faint undetected i-dropout galaxies

Abstract

We present a new technique to quantify the light contribution coming from the faint high redshift ($z\sim 6$) galaxies below the detection threshold of imaging data, set conventionally at S/N=4.5. We illustrate the technique with an application to Hubble Space Telescope Advanced Camera for Surveys images in the F775W and F850LP filters of the Ultra Deep Field parallel field NICP12. The aim of this analysis is to extend by a few magnitudes the faint end of the luminosity function at $z\sim 6$. After masking all the detected sources in the field we apply a Fast Fourier Transform to obtain the spatial power spectrum of the background signal. The power spectrum permits us to separate the background noise signal, the residuals due to the data reduction of the wide field, and the overall signal produced by faint galaxies. The ratio of the signal in the i_775 and z_850 bands is used to estimate the contribution of the faint i-dropout objects. We rely on extensive Monte Carlo simulations to characterize various sources of uncertainty and quantify the number of faint i-dropout galaxies in the field. The analysis allows us to put constraints on the luminosity function at $z\sim 6$ down to z_850= 30 mag, 2.5 mag fainter than with standard techniques on the same data. The data are consistent with a faint end slope of the luminosity function of $\alpha =-1.9$. Assuming a specific set of values for the clumping factor, escape fraction, and spectral energy distribution, we find that the $z\sim 6$ undetected galaxies down to z_850=30 mag could have driven cosmic reionization.

Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal. 11 pages, 17 figures

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Cited by in corpus (8)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• The z~6 Luminosity Function Fainter than -15 mag from the Hubble Frontier Fields: The Impact of Magnification Uncertainties
• The High-$z$ Universe Confronts Warm Dark Matter: Galaxy Counts, Reionization and the Nature of Dark Matter
• Extremely Small Sizes for Faint z~2-8 Galaxies in the Hubble Frontier Fields: A Key Input For Establishing their Volume Density and UV Emissivity
• The Host Halos of OI Absorbers in the Reionization Epoch
• The Impact of Strong Gravitational Lensing on Observed Lyman-Break Galaxy Numbers at 4<z<8 in the GOODS and the XDF Blank Fields
• The Effect of Surface Brightness Dimming in the Selection of High-z Galaxies
• Noise from Undetected Sources in Dark Energy Survey Images