The UV luminosity function at 0.6 < z < 1 from UVCANDELS

Abstract

UVCANDELS is a HST Cycle-26 Treasury Program awarded 164 orbits of primary ultraviolet (UV) F275W imaging and coordinated parallel optical F435W imaging in four CANDELS fields: GOODS-N, GOODS-S, EGS, and COSMOS, covering a total area of $\sim 426$ arcmin${}^2$. This is $\sim 2.7$ times larger than the area covered by previous deep-field space UV data combined, reaching a depth of about 27 and 28 ABmag ($5\ddot{I}ƒ$ in $0.2"$ apertures) for F275W and F435W, respectively. Along with the new photometric catalogs, we present an analysis of the rest-frame UV luminosity function (LF), relying on our UV-optimized aperture photometry method yielding a factor of $1.5\times$ increase than the H-isophot aperture photometry in the signal-to-noise ratios of galaxies in our F275W imaging. Using well tested photometric redshift measurements we identify 5810 galaxies at redshifts $0.6<z<1$, down to an absolute magnitude of $M_{\text{UV}}=-14.2$. In order to minimize the effect of uncertainties in estimating the completeness function, especially at the faint-end, we restrict our analysis to sources above $30\%$ completeness, which provides a final sample of 4726 galaxies at $-21.5<M_{\text{UV}}<-15.5$. We performed a maximum likelihood estimate to derive the best-fit parameters of the UV LF. We report a best-fit faint-end slope of $\hat{I}\pm =-1.359_{-0.041}^{+0.041}$ at $z\sim 0.8$. Creating sub-samples at $z\sim 0.7$ and $z\sim 0.9$, we observe a possible evolution of $\hat{I}\pm$ with redshift. The unobscured UV luminosity density at $M_{\text{UV}}<-10$ is derived as $\ddot{I}{}_{\text{UV}}=1.339_{-0.030}^{+0.027}(\times 10^{26}{\text{ergs/s/Hz/Mpc}}^3)$ using our best-fit LF parameters. The new F275W and F435 photometric catalogs from UVCANDELS have been made publicly available on the Barbara A. Mikulski Archive for Space Telescopes (MAST).

17 pages, 8 figures, Accepted for publication in ApJ