EVIDENCE FOR UBIQUITOUS HIGH-EQUIVALENT-WIDTH NEBULAR EMISSION IN z ∼ 7 GALAXIES: TOWARD A CLEAN MEASUREMENT OF THE SPECIFIC STAR-FORMATION RATE USING A SAMPLE OF BRIGHT, MAGNIFIED GALAXIES

By R. Smit, R. Bouwens, I. Labbé, Wei Zheng, L. Bradley, M. Donahue, D. Lemze, John Moustakas, Keiichi Umetsu, A. Zitrin and 23 more. 2013

161 citations recorded by the source corpus.

Growing observational evidence indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z ∼ 5–7 galaxies. This line emission makes z ∼ 5–7 galaxies appear more massive, with lower specific star-formation rates (sSFRs). However, corrections for this line emission have been difficult to perform reliably because of huge uncertainties on the strength of such emission at z ≳ 5.5. In this paper, we present the most direct observational evidence thus far for ubiquitous high-equivalent-width (EW) [O iii] + Hβ line emission in Lyman-break galaxies at z ∼ 7, and we present a strategy for an improved measurement of the sSFR at z ∼ 7. We accomplish this through the selection of bright galaxies in the narrow redshift window z ∼ 6.6–7.0 where the Spitzer/Infrared Array Camera (IRAC) 4.5 μm flux provides a clean measurement of the stellar continuum light, in contrast with the 3.6 μm flux, which is contaminated by the prominent [O iii] + Hβ lines. To ensure a high signal-to-noise ratio for our IRAC flux measurements, we consider only the brightest (H160 < 26 mag) magnified galaxies we have identified behind galaxy clusters. It is remarkable that the mean rest-frame optical color for our bright seven-source sample is very blue, [3.6]–[4.5] = −0.9 ± 0.3. Such blue colors cannot be explained by the stellar continuum light and require that the rest-frame EW of [O iii] + Hβ is greater than 637 Å for the average source. The four bluest sources from our seven-source sample require an even more extreme EW of 1582 Å. We can also set a robust lower limit of ≳ 4 Gyr−1 on the sSFR of our sample based on the mean spectral energy distribution.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/dd5f6da1b381ffcc2d2f373f879ef0a5f0b8b98b

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Citations in the corpus

Evolution of galaxy stellar masses and star formation rates in the eagle simulations (2014, background): “Note that these do not include corrections for nebular emission lines and hence may overestimate ρ∗ (e.g. Smit et al. 2014).”
The mass evolution of the first galaxies: stellar mass functions and star formation rates at 4 < z < 7 in the CANDELS GOODS-South field (2014, background): “This is especially important at z ∼ 6 and 7 where the impact of nebular emission is strongest (Smit et al. 2014; Stark et al. 2013; González et al. 2014).”
ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS (2016, background): “These corrections are well motivated based on observations of z ∼ 4-8 galaxies (Stark et al. 2013; Labbé et al. 2013; Marmol-Queralto et al. 2016; Smit et al. 2014, 2016; Rasappu et al. 2016) and lower the median inferred stellar mass for z > 3.8 galaxies in our sample by ∼0.1 dex.”
An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, background): “…of candidate of strong Hβ+[O iii] emitters has been identified at much higher redshift (z > 6.5) by looking at the Spitzer/IRAC excess in channels 1 or 2 (depending on redshift; Schaerer & de Barros 2010; Ono et al. 2012; Labbé et al. 2013; Smit et al. 2014, 2015; Roberts-Borsani et al. 2015).”
Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, result): “…of the line flux required to produce the measured IRAC flux excess, in the same manner as earlier studies (Shim et al. 2011; Stark et al. 2013; Smit et al. 2014, 2015a; Roberts-Borsani et al. 2016), The spectroscopic redshift was confirmed by Oesch et al. (2015) through detection of a strong…”
EVIDENCE FOR PopIII-LIKE STELLAR POPULATIONS IN THE MOST LUMINOUS Lyα EMITTERS AT THE EPOCH OF REIONIZATION: SPECTROSCOPIC CONFIRMATION (2015, background): “CR7 is detected in IRAC, with colors as expected for a z ∼ 6.6 source (Smit et al. 2014), likely due to contribution from strong nebular lines with EWs in excess of a few 100 Å in the rest-frame optical (see Figure 2).”
Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs (2018, background): “This is often the case for high redshift galaxies (e.g.,Bouwens et al. 2014; Smit et al. 2014; Bowler et al. 2015; Finkelstein et al. 2015; Oesch et al. 2014), and will be common for earlyuniverse galaxy populations to be studied by JWST (unless accompanied by observations made by ALMA).”
UniverseMachine: The correlation between galaxy growth and dark matter halo assembly from z = 0−10 (2018, unknown): “…Radio 2 Kajisawa et al. (2010) 0.5-3.5 UV/IR 0.03 I Schreiber et al. (2015) 0-4 FIR 1.75 IN Tomczak et al. (2016) 0.5-4 UV/IR 0.08 N Salmon et al. (2015) 3.5-6.5 SED 0.05 IN Smit et al. (2014) 6.6-7 SED 0.02 IN Labbe et al. (2012) 7.5-8.5 UV/IR 0.040 I McLure et al. (2011) 6-8.7 UV 0.0125 I Notes.”
Lyα EMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS (2015, background): “As a comparison, inferred emission line contamination of Spitzer/ IRAC photometry provides tentative evidence for similar WHα in star-forming galaxies at z ∼ 4–7 (Shim et al. 2011; Labbé et al. 2013; Stark et al. 2013; Smit et al. 2014).”
Identification of the brightest Lyα emitters at z = 6.6 : Implications for the evolution of the luminosity function in the reionization era (2015, background): “…or as a further evidence for the source being at z = 6.6, since at that redshift the [3.6] and [4.5] µm bands are contaminated in such a way that sources with strong nebular emission (EW > 1000 Å) are expected to have blue [3.6]− [4.5] colours (e.g. Stark et al. 2013; Smit et al. 2014a,b).”
THE EVOLUTION OF THE GALAXY REST-FRAME ULTRAVIOLET LUMINOSITY FUNCTION OVER THE FIRST TWO BILLION YEARS (2014, background): “Systems with lines such as these (i.e., EW[O III]>500Å) are rare locally, but appear to be more common at high redshift (e.g., van der Wel et al. 2011; Finkelstein et al. 2013; Smit et al. 2014).”