KECK SPECTROSCOPY OF FAINT 3 < z < 8 LYMAN BREAK GALAXIES: EVIDENCE FOR A DECLINING FRACTION OF EMISSION LINE SOURCES IN THE REDSHIFT RANGE 6 < z < 8

By M. Schenker, D. Stark, Richard S. Ellis, Brant Robertson, J. Dunlop, R. McLure, Jean-Paul Kneib, J. Richard. 2011

243 citations recorded by the source corpus.

Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with the Wide Field Camera 3 on board the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star-forming galaxies with detectable Lyman alpha (Lyα) emission in the redshift range 6.3 < z < 8.8. Our earlier surveys with the DEIMOS spectrograph demonstrated a significant increase with redshift in the fraction of line emitting galaxies over the interval 4 < z < 6, particularly for intrinsically faint systems which dominate the luminosity density. Using the longer wavelength sensitivities of Low Resolution Imaging Spectrometer and NIRSPEC, we have targeted 19 Lyman break galaxies selected using recent WFC3/IR data whose photometric redshifts are in the range 6.3 < z < 8.8 and which span a wide range of intrinsic luminosities. Our spectroscopic exposures typically reach a 5σ sensitivity of <50 Å for the rest-frame equivalent width (EW) of Lyα emission. Despite the high fraction of emitters seen only a few hundred million years later, we find only two convincing and one possible line emitter in our more distant sample. Combining with published data on a further seven sources obtained using FORS2 on the ESO Very Large Telescope, and assuming continuity in the trends found at lower redshift, we discuss the significance of this apparent reversal in the redshift-dependent Lyα fraction in the context of our range in continuum luminosity. Assuming all the targeted sources are at their photometric redshift and our assumptions about the Lyα EW distribution are correct, we would expect to find so few emitters in less than 1% of the realizations drawn from our lower redshift samples. Our new results provide further support for the suggestion that, at the redshifts now being probed spectroscopically, we are entering the era where the intergalactic medium is partially neutral. With the arrival of more sensitive multi-slit infrared spectrographs, the prospects for improving the statistical validity of this result are promising.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e4f20af2ac53b4d572c8ca861162407e2bc49d3e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. G. Illingworth
5. P. V. van Dokkum
6. J. Dunlop
7. M. Franx
8. I. Labbé

In Instrumentation

1. Richard S. Ellis
2. R. Bouwens
3. P. Oesch
4. M. Franx
5. G. Illingworth
6. P. V. van Dokkum
7. J. Dunlop
8. I. Labbé

Citations in the corpus

• Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA (2018, unknown): “…= 5.5. e Inferred from Y = 26.15 Reference Cu03: Cuby et al. (2003), R11: Richard et al. (2011), V11: Vanzella et al. (2011), O12: Ono et al. (2012), Sc12: Schenker et al. (2012), Sh12: Shibuya et al. (2012), W13: Willott et al. (2013), Maio15: Maiolino et al. (2015), W15: Willott et al. (2015),…”
• SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky (2017, background): “The studies of Lyα emitting fractions indicate xHI & 0.5 at z ∼ 7 (e.g., Pentericci et al. 2011; Schenker et al. 2012; Ono et al. 2012; Treu et al. 2012; Caruana et al. 2012; Caruana et al. 2014; Pentericci et al. 2014; Schenker et al. 2014).”
• UV-CONTINUUM SLOPES OF >4000 z ∼ 4–8 GALAXIES FROM THE HUDF/XDF, HUDF09, ERS, CANDELS-SOUTH, AND CANDELS-NORTH FIELDS (2013, background): “However, spectroscopic follow-up of current z ∼ 7-8 samples (e.g., Ono et al. 2012; Schenker et al. 2012; Pentericci et al. 2011; Caruana et al. 2012) seems to suggest that Lyα emission is quite rare in these sources (likely due to an increasingly neutral medium).”
• Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey (2019, background): “…circles are measurements from LBGs with confirmed z > 7 Lyα (Oesch et al. 2015; Roberts-Borsani et al. 2016; Stark et al. 2017; Zitrin et al. 2015; Song et al. 2016a; Finkelstein et al. 2013; Shibuya et al. 2012; Ono et al. 2012; Schenker et al. 2012; Vanzella et al. 2011; Laporte et al. 2017a).”
• NEW OBSERVATIONS OF z ∼ 7 GALAXIES: EVIDENCE FOR A PATCHY REIONIZATION (2014, background): “— Marginalized posterior distribution function of ǫ at z ∼ 7 based on a compilation of 68 z-dropouts with deep spectroscopic follow-up presented in this paper or taken from the literature (Pentericci et al. 2011; Ono et al. 2012; Schenker et al. 2012).”
• Spectroscopic detection of C iv λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies (2015, methodology): “A spectroscopic redshift (z = 7.045) was achieved via detection of Lyα at 9780 Å (Schenker et al. 2012).”
• Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, background): “This could be due to the Lyα damping absorption of partly neutral IGM (Pentericci et al. 2011; Vanzella et al. 2011; Ono et al. 2012; Schenker et al. 2012) or optically thick systems in the intervening IGM (Bolton & Haehnelt 2013).”
• The Universe Is Reionizing at z ∼ 7: Bayesian Inference of the IGM Neutral Fraction Using Lyα Emission from Galaxies (2017, background): “These data comprise 68 galaxies spanning UV magnitudes −22.75∼<Muv∼< − 17.8 and include 10 intrinsically faint objects gravitationally lensed behind the Bullet Cluster (Bradač et al. 2012) as well as observations in deep HST legacy fields (Fontana et al. 2010; Vanzella et al. 2011; Ono et al. 2012;”
• Lyα and C iii] emission in z = 7–9 Galaxies: accelerated reionization around luminous star-forming systems? (2016, methodology): “We search previous spectroscopic studies (e.g., Ono et al. 2012; Schenker et al. 2012; Finkelstein et al. 2013; Schenker et al. 2014; Pentericci et al. 2014) for galaxies with photometric redshifts above z ' 7 that are both luminous (MUV < −21) and have IRAC fluxes indicative of intense [OIII]+Hβ…”
• Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “However, at z > 6 the Lyα fraction decreases (Fontana et al. 2010; Stark, Ellis, & Ouchi 2011; Pentericci et al. 2011; Schenker et al. 2012; Ono et al. 2012; Caruana et al. 2012, 2013; Finkelstein et al. 2013; Pentericci et al. 2014; Schenker et al. 2014; Tilvi et al. 2014), in line with…”
• Lyα EMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS (2015, background): “…of reionization, weaker or less frequent Lyα emission may indicate a significant neutral hydrogen fraction in the IGM (Ota et al. 2010; Pentericci et al. 2011; Schenker et al. 2012; Treu et al. 2012, 2013), an increase in the escape fraction of ionizing photons, or both (Dijkstra et al. 2014).”
• Lyα EMISSION FROM A LUMINOUS z = 8.68 GALAXY: IMPLICATIONS FOR GALAXIES AS TRACERS OF COSMIC REIONIZATION (2015, background): “…Department of Physics, Durham University, South Road, Durham DH1 3LE, UK marked decline beyond z '6 in the visibility of Lymanalpha (Lyα) emission seen in continuum-selected galaxies (Stark et al. 2010; Fontana et al. 2010; Ono et al. 2012; Pentericci et al. 2011; Schenker et al. 2012, 2014).”
• NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, methodology): “Although Schenker et al. (2012a) and McLure et al. (2012) use the same data sets, their luminosity function determinations are based on different selection techniques.”
• Hydrogen Epoch of Reionization Array (HERA) (2016, background): “…the ionization state of the IGM from quasar proximity zones (Carilli et al. 2010; Bolton et al. 2011; Bosman & Becker 2015) and the demographics of Ly-α emitting galaxies (Fontana et al. 2010; Schenker et al. 2012; Treu et al. 2012; Dijkstra et al. 2014) is uncertain and highly modeldependent.”
• THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). I. SURVEY OVERVIEW AND FIRST DATA RELEASE (2015, background): “…of dropouts that are Lyα emitters increases steadily out to z ∼ 6 (e.g., Stark et al. 2011), while it declines significantly at z ∼ 7 and above (Kashikawa et al. 2006; Fontana et al. 2010; Pentericci et al. 2011; Clément et al. 2012; Ono et al. 2012; Schenker et al. 2012; Treu et al. 2012, 2013).”
• CRITICAL STAR FORMATION RATES FOR REIONIZATION: FULL REIONIZATION OCCURS AT REDSHIFT z ≈ 7 (2012, background): “Recent surveys of high-redshift galaxies and Lyα emitters (Bouwens et al. 2011a; Ouchi et al. 2010; Kashikawa et al. 2011; Ono et al. 2012; Schenker et al. 2012) infer an increasing IGM neutral fraction from the declining populations in the range z = 6–8.”