On the bright end of the UV luminosity functions of galaxies at z ∼0.6-1.2

Abstract

We derive the ultraviolet (UV) luminosity function (LF) of star-forming galaxies in the redshift range z = 0.6-1.2, in the rest-frame far-UV (1500 Å) wavelength. For this work, we are in particular interested in the bright end of the UV LF in this redshift range. Data from the XMM-Newton Optical Monitor (XMM-OM), near-UV (2410-3565 Å) observations over 1.5 deg2 of the Cosmic evolution survey (COSMOS) field are employed for this purpose. We compile a source list of 879 sources with UVW1AB in the range ∼21-24 mag from the wide-Area UVW1 image of the COSMOS field in the two bins 0.6 ≤ z ≤ 0.8 and 0.8 ≤ z ≤ 1.2. The M1500 for these sources lies in the interval [-19.10,-22.50]. We use the maximum likelihood to fit a Schechter function model to the unbinned data to estimate the parameters (faint-end slope, characteristic magnitude, and normalization) of the Schechter function. We find the shape of the LF to be consistent with the Schechter model, and the parameters are in fair agreement with other studies conducted using direct measurements of the 1500 Å flux. We see a brightening of the characteristic magnitude as we move from lower (0.7) to higher (1.0) redshift. The measures for luminosity density are within the error margins of past studies. We examine the brightest sources in our sample for the active galactic nucleus contribution. These sources are characterized by their spectral energy distributions, integrated infrared (IR) luminosities, and morphologies. We also explore their overlap with the brightest IR galaxies in a similar redshift range.