The UV luminosity functions of Bright z>8 Galaxies: Determination from ~0.41 deg2 of HST Observations along ~sim 300 independent sightlines

Abstract

We determine the bright end of the rest-frame UV luminosity function (UVLF) at $z=8-10$ by selecting bright $z\gtrsim 8$ photometric candidates from the largest systematic compilation of HST (pure-)parallel observations to date, the Super-Brightest-of-Reionizing-Galaxies (SuperBoRG) data set. The data set includes $\sim 300$ independent sightlines from WFC3 observations, totalling $800-1300$ arcmin${}^2$ (depending on redshift). We identify 31 $z\gtrsim 8$ candidates via colour selection and photo-$z$ analysis with observed magnitude ($24.1<H_{160}<26.6$) and $1\sigma$ range probability of $58-95\%$ of being true high-z galaxies. Following detailed completeness and source recovery simulations, as well as modelling of interloper contamination, we derive rest-frame UVLFs at $z=8-10$ down to $M_{UV}\simeq -23$. We find that the bright end of the galaxy luminosity function can be described both by a Schechter and by a double power-law function, with our space-based large area determination showing some tentative discrepancies with the luminosity functions derived from ground-based observations at the same redshifts. We identify two possible explanations. The first is that the UVLF includes a substantial contribution from AGNs at magnitudes $M_{UV}<-22$. The UVLF we derive at $z=8$ is consistent with no evolution of the bright end from $z=6-7$ UVLFs that include AGNs. An alternative (and non-exclusive) possibility is that the dust content of the observed galaxies decreases with redshift, thereby countering the naturally expected decrease in the UV luminosity functions because of a decreased star formation rate with increasing redshift. Both scenarios raise interesting prospects to further understand galaxy formation in extreme objects during the epoch of reionisation.

11 pages, 9 figures. Accepted for publication in MNRAS

References in corpus (38)

• EAZY: A Fast, Public Photometric Redshift Code
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• UV Luminosity Functions at z~4, 5, and 6 from the HUDF and other Deep HST ACS Fields: Evolution and Star Formation History
• A Comprehensive Study on Galaxies at z~9-16 Found in the Early JWST Data: UV Luminosity Functions and Cosmic Star-Formation History at the Pre-Reionization Epoch
• Two Remarkably Luminous Galaxy Candidates at $z\approx 10-12$ Revealed by JWST
• The evolution of the galaxy UV luminosity function at redshifts z ~ 8-15 from deep JWST and ground-based near-infrared imaging
• New Determinations of the UV Luminosity Functions from z~9 to z~2 show a remarkable consistency with halo growth and a constant star formation efficiency
• Early results from GLASS-JWST. III: Galaxy candidates at z$\sim$9-15
• Dust in the reionization era: ALMA observations of a $z$=8.38 Galaxy
• The brightest galaxies at Cosmic Dawn
• A lack of evolution in the very bright-end of the galaxy luminosity function from z = 8-10
• Dust attenuation, dust emission, and dust temperature in galaxies at z>=5: a view from the FIRE-2 simulations
• A Census of the Bright z=8.5-11 Universe with the Hubble and Spitzer Space Telescopes in the CANDELS Fields
• The Luminosity Function at z~8 from 97 Y-band dropouts: Inferences About Reionization
• The UDF05 Follow-up of the HUDF: I. The Faint-End Slope of the Lyman-Break Galaxy Population at z~5
• Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
• Measurement of Galaxy Clustering at z~7.2 and the Evolution of Galaxy Bias from 3.8<z<8 in the XDF, GOODS-S AND GOODS-N
• Probing Cosmic Dawn : Ages and Star Formation Histories of Candidate $z\ge$9 Galaxies
• Early results from GLASS-JWST. XI: Stellar masses and mass-to-light ratio of z>7 galaxies
• First Light And Reionisation Epoch Simulations (FLARES) V: The redshift frontier
• Interpreting the Spitzer/IRAC Colours of 7<z<9 Galaxies: Distinguishing Between Line Emission and Starlight Using ALMA
• Constraining the physical properties of the first lensed $z\sim 10-16$ galaxy candidates with JWST
• Probing the Bright End of the Rest-Frame Ultraviolet Luminosity Function at z = 8-10 with Hubble Pure-Parallel Imaging
• Early results from GLASS-JWST. X: Rest-frame UV-optical properties of galaxies at 7 < z < 9
• Frontier Fields : Combining HST, VLT and Spitzer data to explore the $z$$\sim$8 Universe behind the lensing cluster MACS0416$-$2403
• HST imaging of the brightest z~8-9 galaxies from UltraVISTA: the extreme bright end of the UV luminosity function
• Dust formation, evolution, and obscuration effects in the very high-redshift universe
• The Physical Properties of Luminous $z\gtrsim 8$ Galaxies and Implications for the Cosmic Star Formation Rate Density From $\sim$0.35 deg${}^2$ of (Pure-)Parallel HST Observations
• Blue Rest-Frame UV-Optical Colors in z~8 Galaxies from GREATS: Very Young Stellar Populations at ~650 Myr of Cosmic Time
• Accounting for Cosmic Variance in Studies of Gravitationally-Lensed High-Redshift Galaxies in the Hubble Frontier Field Clusters
• The Brightest Galaxies at Cosmic Dawn from Scatter in the Galaxy Luminosity versus Halo Mass Relation
• COSMOS2020: UV selected galaxies at $z\ge 7.5$
• Characterization and modeling of contamination for Lyman break galaxy samples at high redshift
• SuperBoRG: Search for The Brightest of Reionizing Galaxies and Quasars in HST Parallel Imaging Data
• Beyond the Local Volume. I. Surface Densities of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields
• Beyond the Local Volume. II. Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields
• A massive interacting galaxy 510 million years after the Big Bang
• Unresolved z~8 point sources and their impact on the bright end of the galaxy luminosity function

Cited by in corpus (6)

• The THESAN-ZOOM project: Burst, quench, repeat -- unveiling the evolution of high-redshift galaxies along the star-forming main sequence
• The importance of stochasticity in determining galaxy emissivities and UV LFs during cosmic dawn and reionization
• The UV luminosity function at 0.6 < z < 1 from UVCANDELS
• ColdSIM predictions of [C II] emission in primordial galaxies
• Starlight from JWST: Implications for star formation and dark matter models
• The BoRG-$JWST$ Survey: Abundance and Mass-to-light Ratio of Luminous $z=7-9$ Galaxies from Independent Sight Lines with NIRSpec