ULTRAVIOLET LUMINOSITY FUNCTIONS FROM 132 z ∼ 7 AND z ∼ 8 LYMAN-BREAK GALAXIES IN THE ULTRA-DEEP HUDF09 AND WIDE-AREA EARLY RELEASE SCIENCE WFC3/IR OBSERVATIONS

By R. Bouwens, G. Illingworth, P. Oesch, I. Labbé, M. Trenti, P. V. van Dokkum, M. Franx, M. Stiavelli, C. Carollo, D. Magee and 1 more. 2010

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We identify 73 z ∼ 7 and 59 z ∼ 8 candidate galaxies in the reionization epoch, and use this large 26–29.4 AB mag sample of galaxies to derive very deep luminosity functions to < − 18 AB mag and the star formation rate (SFR) density at z ∼ 7 and z ∼ 8 (just 800 Myr and 650 Myr after recombination, respectively). The galaxy sample is derived using a sophisticated Lyman-break technique on the full two-year Wide Field Camera 3/infrared (WFC3/IR) and Advanced Camera for Surveys (ACS) data available over the HUDF09 (∼29.4 AB mag, 5σ), two nearby HUDF09 fields (∼29 AB mag, 5σ, 14 arcmin2), and the wider area Early Release Science (∼27.5 AB mag, 5σ, ∼40 arcmin2). The application of strict optical non-detection criteria ensures the contamination fraction is kept low (just ∼7% in the HUDF). This very low value includes a full assessment of the contamination from lower redshift sources, photometric scatter, active galactic nuclei, spurious sources, low-mass stars, and transients (e.g., supernovae). From careful modeling of the selection volumes for each of our search fields, we derive luminosity functions for galaxies at z ∼ 7 and z ∼ 8 to < − 18 AB mag. The faint-end slopes α at z ∼ 7 and z ∼ 8 are uncertain but very steep at α = −2.01 ± 0.21 and α = −1.91 ± 0.32, respectively. Such steep slopes contrast to the local α ≳ −1.4 and may even be steeper than that at z ∼ 4 where α = −1.73 ± 0.05. With such steep slopes (α ≲ −1.7) lower luminosity galaxies dominate the galaxy luminosity density during the epoch of reionization. The SFR densities derived from these new z ∼ 7 and z ∼ 8 luminosity functions are consistent with the trends found at later times (lower redshifts). We find reasonable consistency with the SFR densities implied from reported stellar mass densities being only ∼40% higher at z < 7. This suggests that (1) the stellar mass densities inferred from the Spitzer Infrared Array Camera (IRAC) photometry are reasonably accurate and (2) that the initial mass function at very high redshift may not be very different from that at later times.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c392defff4538a5c2e02b77869b3ee4069360c55

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. C. Conroy
4. Richard S. Ellis
5. R. Dav'e
6. P. V. van Dokkum
7. R. Somerville
8. M. Franx

In Instrumentation

1. C. Conroy
2. P. V. van Dokkum
3. P. Hopkins
4. Richard S. Ellis
5. M. Franx
6. L. Hernquist
7. R. Bouwens
8. R. Dav'e

Citations in the corpus

• THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS (2014, methodology): “They employ a novel probabilistic model that incorporates a wide range of data from high redshift SFRs (e.g., Bouwens et al. 2011, 2012; Bradley et al. 2012) to observations of recent star formation in the local universe (e.g., 21 Hα, UV, 24 µm; Salim et al. 2007; Kennicutt et al. 2008; Moustakas…”
• Galaxy UV-luminosity function and reionization constraints on axion dark matter (2014, background): “…dataset for constraining the contribution of galaxies to the reionisation of the universe through estimation of the rest-frame UV luminosity function over the the redshift range between z = 4 to z = 10 (Bouwens et al. 2014, 2011; Oesch et al. 2012; McLure et al. 2013; Lorenzoni et al. 2013).”
• CANDELS: THE CONTRIBUTION OF THE OBSERVED GALAXY POPULATION TO COSMIC REIONIZATION (2012, background): “We use the luminosity functions from Bouwens et al. (2007) forz= 4, 5 and 6; Bouwens et al. (2011c) forz= 7; Bradley et al. (2012) for z= 8 and Bouwens et al. (2011a) forz= 10.”
• UV-CONTINUUM SLOPES AT z  ∼  4–7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR–MAGNITUDE RELATIONSHIP FOR z ⩾ 4 STAR-FORMING GALAXIES (2011, methodology): “We will make use of the z ∼ 4, z ∼ 5, z ∼ 6, and z ∼ 7 LFs of Bouwens et al. (2007) and Bouwens et al. (2011b).”
• The rising star formation histories of distant galaxies and implications for gas accretion with time (2010, methodology): “Many studies have measured UV luminosity functions of galaxies from z ∼ 2 to z & 8 (e.g., Bouwens et al. 2004, 2006, 2010b,a; Reddy & Steidel 2009; Oesch et al. 2010b; McLure et al. 2010).”
• UV LUMINOSITY FUNCTIONS AT REDSHIFTS z ∼ 4 TO z ∼ 10: 10,000 GALAXIES FROM HST LEGACY FIELDS (2014, methodology): “From this fitting formula, we find strong evidence for significant evolution in the volume density φ∗ and α. Evolution in the characteristic luminosity M∗ may be present, but it is less significant than found previously (Bouwens et al. 2008, 2011), as we noted above.”
• The current status of galaxy formation (2012, background): “For example, nebular emission and dust extinction affect infrerred ages, and one cannot easily understand the blue continuum slopes oberved at high redshift and lower UV luminosities (Bouwens et al., 2011).”
• New Measurements of the Ionizing Ultraviolet Background over 2 < z < 5 and Implications for Hydrogen Reionization (2013, background): “…> 6 indicate that the global star formation rate density declines steeply with redshift over 6 < z < 12 (e.g., Ouchi et al. 2009; Castellano et al. 2010; Bunker et al. 2010; Bouwens et al. 2006, 2008, 2011, 2012; Oesch et al. 2010; McLure et al. 2010, 2013; Schenker et al. 2013; Ellis et al. 2013).”
• Faint high-redshift AGN in the Chandra deep field south: the evolution of the AGN luminosity function and black hole demography (2011, methodology): “We also considered 330 z > 6 galaxy candidates from the lists of Bouwens et al. (2006), Castellano et al. (2010), McLure et al. (2010), McLure et al. (2011), Bouwens et al. (2011), which are not included in the above two lists.”
• SPECTROSCOPIC CONFIRMATION OF THREE z-DROPOUT GALAXIES AT z = 6.844–7.213: DEMOGRAPHICS OF Lyα EMISSION IN z ∼ 7 GALAXIES (2011, methodology): “For example, the best-fit Schechter parameterization of the z = 7 luminosity function from Bouwens et al. (2011b) yields a space density 2.7×10−7 Mpc−3 for galaxies with MUV ≤ −21.81.”
• LENS MODELS AND MAGNIFICATION MAPS OF THE SIX HUBBLE FRONTIER FIELDS CLUSTERS (2014, methodology): “These surveys include the Hubble Deep Field (Williams et al. 1996), its successive iterations (Beckwith et al. 2006; Bouwens et al. 2011; Ellis et al. 2013; Illingworth et al. 2013), and the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS; Grogin et al. 2011; Koekemoer et al.…”
• CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY (2011, unknown): “The bright end of the UVLF of star-forming galaxies is evolving rapidly at 4 < z < 7 (e.g., Dickinson et al. 2004, Bouwens et al. 2007, 2008, 2011b), but the UV flux from these bright galaxies thus far appears insufficient to explain reionization.”
• LOWER-LUMINOSITY GALAXIES COULD REIONIZE THE UNIVERSE: VERY STEEP FAINT-END SLOPES TO THE UV LUMINOSITY FUNCTIONS AT z ⩾ 5–8 FROM THE HUDF09 WFC3/IR OBSERVATIONS (2011, methodology): “We assume the UV colors of the sources are distributed as found by Bouwens et al. (2011c).”
• Directly Observing the Galaxies Likely Responsible for Reionization (2016, background): “The faint end of the rest-frame ultraviolet (UV) luminosity function is steep (a ~ -2; Bouwens et al. 2011, 2015; McLure et al. 2013; Finkelstein et al. 2015), implying that the UV luminosity density—and therefore the ionizing photons responsible for the reionization of the universe—is dominated by…”
• THE BIRTH OF A GALAXY: PRIMORDIAL METAL ENRICHMENT AND STELLAR POPULATIONS (2010, methodology): “This value agrees with derived SFRs from z = 6 − 10 galaxy luminosity functions (e.g. Bouwens et al. 2011) and large-scale galaxy formation simulations (e.g. Schaye et al. 2010).”
• THE HST EXTREME DEEP FIELD (XDF): COMBINING ALL ACS AND WFC3/IR DATA ON THE HUDF REGION INTO THE DEEPEST FIELD EVER (2013, methodology): “The HUDF was observed as part of the HUDF09 program in 2009 (PI: Illingworth; e.g. Bouwens et al. 2011b) as one of the first set of images taken by the new infrared camera of WFC3.”
• ON THE LACK OF EVOLUTION IN GALAXY STAR FORMATION EFFICIENCY (2012, methodology): “At high redshifts, we include recent measurements of stellar masses and star formation rates to z = 8 (Bouwens et al. 2012, 2011; McLure et al. 2011; Bradley et al. 2012).”
• TOWARD A UNIFICATION OF STAR FORMATION RATE DETERMINATIONS IN THE MILKY WAY AND OTHER GALAXIES (2011, background): “Our understanding of galaxy activity and the growth of stellar mass throughout cosmic time depends critically on measurements of SFR (e.g., Madau et al. 1996; Bouwens et al. 2011).”
• THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z ∼ 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN (2012, methodology): “While the UDF09 collaboration has measured a faint-end slope of αz∼7 = −2.01 ± 0.21 (Bouwens et al. 2011) incorporating the UDF, parallel fields, and the ERS data, a competing determination utilizing the sizeluminosity relation measured from the UDF09 data and the CANDELS Deep+Wide surveys in three…”
• A HIGHLY CONSISTENT FRAMEWORK FOR THE EVOLUTION OF THE STAR-FORMING “MAIN SEQUENCE” FROM z ∼ 0–6 (2014, methodology): “…selection methods include: sBzK, used to select SFGs from 1.4 < z < 2.5 (D07; R11; K13); the Lyman break (Steidel et al. 1999; Stark et al. 2009; Bouwens et al. 2011; B12), used to select high-z Lyman-break galaxies (LBGs); and U − g vs. Mbol, or any other cut on the color-magnitude diagram…”