The Evolution of the Faint End of the Uv Luminosity Function During the Peak Epoch of Star Formation *

Abstract

We present a robust measurement of the rest-frame UV luminosity function (LF) and its evolution during the peak epoch of cosmic star formation at 1 < z < 3. We use our deep near ultraviolet imaging from WFC3/UVIS on the Hubble Space Telescope (HST) and existing ACS/WFC and WFC3/IR imaging of three lensing galaxy clusters, Abell 2744 and MACSJ0717 from the Hubble Frontier Field survey and Abell 1689. Combining deep UV imaging and high magnification from strong gravitational lensing, we use photometric redshifts to identify 780 ultra-faint galaxies with M UV < −12.5 AB mag at 1 < z < 3. From these samples, we identified 5 new, faint, multiply imaged systems in A1689. We run a Monte Carlo simulation to estimate the completeness correction and effective volume for each cluster using the latest published lensing models. We compute the rest-frame UV LF and find the best-fit faint-end slopes of α = −1.56 ± 0.04, α = −1.72 ± 0.04 and α = −1.94 ± 0.06 at 1.0 < z < 1.6, 1.6 < z < 2.2 and 2.2 < z < 3.0, respectively. Our results demonstrate that the UV LF becomes steeper from z ∼ 1.3 to z ∼ 2.6 with no sign of a turnover down to M UV = −14 AB mag. We further derive the UV LFs using the Lyman break "dropout" selection and confirm the robustness of our conclusions against different selection methodologies. Because the sample sizes are so large, and extend to such faint luminosities, the statistical uncertainties are quite small, and systematic uncertainties (due to the assumed size distribution, for example), likely dominate. If we restrict our analysis to galaxies and volumes above > 50% completeness in order to minimize these systematics, we still find that the faint-end slope is steep and getting steeper with redshift, though with slightly shallower (less negative) values (α = −1.55 ± 0.06, −1.69 ± 0.07 and −1.79 ± 0.08 for z ∼ 1.3, 1.9 and 2.6, respectively). Finally, we conclude that the faint star-forming galaxies with UV magnitudes of −18.5 < M UV < −12.5 covered in this study, produce the majority (55%-60%) of the unobscured UV luminosity density at 1 < z < 3.

Paving the way for the JWST: witnessing globular cluster formation at z > 3

“…The detection of extremely faint galaxies at high redshift has been reported in the literature, with magnitudes as faint as MUV −14 both at redshift 2 − 3 (e.g., Alavi et al 2014Alavi et al , 2016 and 6 − 8 (e.g., Atek et al 2015;Livermore et al 2016;Bouwens et al 2015;Vanzella et al 2014;Bouwens et al 2016c). These systems are characterised by very low stellar masses, of the order of a few 10 6 solar masses (e.g., Karman et al 2016).…”

Stellar Mass Function of Active and Quiescent Galaxies via the Continuity Equation

“…Solid lines refer to the rendition from UV plus far-IR/sub-mm/radio data; dotted lines (only plotted at z ≈ 0 and 1) refer to the rendition from UV data (dust corrected according to standard prescriptions based on the UV slope). UV data (open symbols) are from van der Burg et al (2010;diamonds), Bouwens et al (2016Bouwens et al ( , 2017pentagons), inverse triangles), Cucciati et al (2012;triangles), Wyder et al (2005;spirals), Oesch et al (2010;crosses), Alavi et al (2016;asterisks); far-IR/sub-mm data from Gruppioni et al (2015;hexagons), Magnelli et al (2013;circles), Gruppioni et al (2013;squares), Lapi et al (2011;stars), and Cooray et al (2014;pacmans); radio data from Novak et al (2017;clovers). extinction law, but note that switching to a Small Magellanic Cloud (SMC) extinction law affects mildly the SFR function at the faint end (see also Sect.…”

The Frontier Fields: Survey Design and Initial Results

“…Additional HST WFC3 ultraviolet imaging (Alavi et al 2016) and grism spectroscopy (Schmidt et al 2014) are also being obtained for all the Frontier Field clusters. We continue to maintain a clearing-house website for public data links and Frontier Fields-related publications: www.stsci.edu/hst/campaigns/ frontier-fields/FF-Data.…”

“…Several complementary HST General Observer (GO) observing programs have been awarded to obtain deep WFC3/UV imaging (GO 13389, 14209; PI B. Siana; Alavi et al 2016), WFC3/IR grism spectroscopy (GO 13459; T. Treu), and target-of-opportunity follow-up of transient events (GO 13386, 13790, 14208;. Hundreds of multiply imaged background galaxies at all redshifts have permitted the construction of dark-matter maps of the clusters at unprecedented resolution to probe cluster substructure (e.g., Jauzac et al 2014Jauzac et al , 2015Wang et al 2015;Hoag et al 2016;Limousin et al 2016;Mohammed et al 2016; P. Natarajan 2017 in preparation), and will enable new cosmological constraints via angular scaling relations (e.g., Kneib & Natarajan 2011).…”