The Impact of Strong Gravitational Lensing on Observed Lyman-Break Galaxy Numbers at 4<z<8 in the GOODS and the XDF Blank Fields

Abstract

Detection of Lyman-Break Galaxies (LBGs) at high-redshift can be affected by gravitational lensing induced by foreground deflectors not only in galaxy clusters, but also in blank fields. We quantify the impact of strong magnification in the samples of $B$, $V$, $i$, $z$ $\&$ $Y$ LBGs ($4\lesssim z\lesssim 8$) observed in the XDF and GOODS/CANDELS fields, by investigating the proximity of dropouts to foreground objects. We find that $\sim 6\%$ of bright LBGs ($m_{H_{160}}<26$) at $z\sim 7$ have been strongly lensed ($\mu >2$) by foreground objects. This fraction decreases from $\sim 3.5\%$ at $z\sim 6$ to $\sim 1.5\%$ at $z\sim 4$. Since the observed fraction of strongly lensed galaxies is a function of the shape of the luminosity function (LF), it can be used to derive Schechter parameters, $\alpha$ and $M_{\star }$, independently from galaxy number counts. Our magnification bias analysis yields Schechter-function parameters in close agreement with those determined from galaxy counts albeit with larger uncertainties. Extrapolation of our analysis to $z\gtrsim 8$ suggests that future surveys with JSWT, WFIRST and EUCLID should find excess LBGs at the bright-end, even if there is an intrinsic exponential cutoff of number counts. Finally, we highlight how the magnification bias measurement near the detection limit can be used as probe of the population of galaxies too faint to be detected. Preliminary results using this novel idea suggest that the magnification bias at $M_{UV}\sim -18$ is not as strong as expected if $\alpha \lesssim -1.7$ extends well below the current detection limits in the XDF. At face value this implies a flattening of the LF at $M_{UV}\gtrsim -16.5$. However, selection effects and completeness estimates are difficult to quantify precisely. Thus, we do not rule out a steep LF extending to $M_{UV}\gtrsim -15$.

Submitted to ApJ on 18/12/2014

References in corpus (17)

• EAZY: A Fast, Public Photometric Redshift Code
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• UltraVISTA: a new ultra-deep near-infrared survey in COSMOS
• The Cosmic Evolution Survey (COSMOS): Subaru Observations of the HST COSMOS Field
• z~7-10 Galaxies in the HUDF and GOODS fields, and their UV Luminosity Functions
• A Spectroscopic Survey of Redshift 1.4<z<3.0 Galaxies in the Goods-North Field: Survey Description, Catalogs, and Properties
• CARS: the CFHTLS-Archive-Research Survey; I. Five-band multi-colour data from 37 sq. deg. CFHTLS-Wide observations
• Hubble Frontier Fields First Complete Cluster Data: Faint Galaxies at $z\sim 5-10$ for UV Luminosity Functions and Cosmic Reionization
• Curvature in the scaling relations of early-type galaxies
• New Constraints on the Faint-end of the UV Luminosity Function at z~7-8 using the Gravitational Lensing of the Hubble Frontier Fields Cluster A2744
• The Evolution of the UV Luminosity Function from z ~ 0.75 to z ~ 2.5 using HST ERS WFC3/UVIS Observations
• The Luminosity Function at z~8 from 97 Y-band dropouts: Inferences About Reionization
• A catalog of mid-infrared sources in the Extended Groth Strip
• Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
• The discovery of a significant sample of massive galaxies at redshifts 5 < z < 6 in the UKIDSS Ultra Deep Survey Early Data Release
• The Evolving Faint-End of the Luminosity Function
• Ultra-faint high-redshift galaxies in the Frontier Fields

Cited by in corpus (14)

• A lack of evolution in the very bright-end of the galaxy luminosity function from z = 8-10
• Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
• The Brightest Galaxies at Cosmic Dawn from Scatter in the Galaxy Luminosity versus Halo Mass Relation
• COSMOS2020: UV selected galaxies at $z\ge 7.5$
• Revisiting the Lensed Fraction of High-Redshift Quasars
• The rapid transition from star-formation to AGN dominated rest-frame UV light at z ~ 4
• Galaxy Morphologies Revealed with Subaru HSC and Super-Resolution Techniques I: Major Merger Fractions of L_UV~3-15 L_UV* Dropout Galaxies at z~4-7
• A model for galaxy-galaxy strong lensing statistics in surveys
• Gravitational lensing modification of the high redshift galaxy luminosity function
• Velocity dispersion function evolution from strong lensing statistics
• Model-independent Reconstruction of UV Luminosity Function and Reionization Epoch
• Characterizing elusive, faint dusty star-forming galaxies: a lensed, optically undetected ALMA galaxy at z~3.3
• Galaxy-scale lens search in the PEARLS NEP TDF and CEERS JWST fields
• A quantitative assessment of completeness correction methods and public release of a versatile simulation code