On the stellar masses of IRAC detected Lyman Break Galaxies at z ∼ 3

We present results of a large survey of the mid-infrared (mid-IR) properties of 248 Lyman Break Galaxies (LBGs) with confirmed spectroscopic redshift using deep Spitzer/Infrared Array Camera (IRAC) observations in six cosmological fields. By combining the new mid-IR photometry with optical and near-infrared observations, we model the spectral energy distributions (SEDs) employing a revised version of the Bruzual and Charlot synthesis population code that incorporates a new treatment of the thermal-pulsating asymptotic giant branch phase (CB07). Our primary aim is to investigate the impact of the AGB phase in the stellar masses of the LBGs, and compare our new results with previous stellar mass estimates. We investigate the stellar mass of the LBG population as a whole and assess the benefits of adding longer wavelengths to estimates of stellar masses for high-redshift galaxies. Based on the new CB07 code, we find that the stellar masses of LBGs are smaller on an average by a factor of similar to 1.4 compared to previous estimates. LBGs with 8 and/or 24 mu m detections show higher masses (M(*) similar to 10(11)M(circle dot)) than LBGs faint in the IRAC bands (M(*) similar to 10(9)M(circle dot)) . The ages of these massive LBGs are considerably higher than the rest of the population, indicating that they have been star forming for at least similar to 1 Gyr. We also show how the addition of the IRAC bands improves the accuracy of the estimated stellar masses and reduced the scatter on the derived mass-to-light ratios. In particular, we present a tight correlation between the 8 mu m IRAC band (rest-frame K for galaxies at z similar to 3) and the stellar mass. We calculate the number density of massive (M(*) > 10(11)M(circle dot)) LBGs and find it to be Phi = (1.12 +/- 0.4) x 10(-5) Mpc(-3), similar to 1.5 times lower than that found by previous studies. Finally, based on ultraviolet-corrected star formation rates (SFRs), we investigate the SFR-stellar mass correlation at z similar to 3, find it similar to the one observed at other redshifts and show that our data place the peak of the evolution of the specific SFR at z similar to 3.