Deficiency of Large Equivalent Width Lyα Emission in Luminous Lyman Break Galaxies at
                    <i>z</i>
                    ~ 5-6?

Ando, Masataka; Ohta, Kouji; Iwata, Ikuru; Akiyama, Masayuki; Aoki, Kentaro; Tamura, Naoyuki

doi:10.1086/505652

Cited by 115 publications

(167 citation statements)

References 43 publications

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“…Within the options discussed in this paper, this choice best describes the trend of increasing strength of Lyα with redshift as observed from spectroscopic surveys (e.g. Ando et al 2006;Ouchi et al 2008;Stark et al 2010), other studies (Blanc et al 2011;Hayes et al 2011), and our models that allow for varying Lyα strength ).…”

Section: Evolution Of the Physical Properties From Z ∼ 3 To Z ∼mentioning

confidence: 99%

Properties ofz~ 3–6 Lyman break galaxies

Barros

Schaerer

Stark

2014

A&A

156

205

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Context. To gain insight on the mass assembly and place constraints on the star formation history (SFH) of Lyman break galaxies (LBGs), it is important to accurately determine their properties. Aims. We estimate how nebular emission and different SFHs affect parameter estimation of LBGs.Methods. We present a homogeneous, detailed analysis of the spectral energy distribution (SED) of ∼1700 LBGs from the GOODS-MUSIC catalogue with deep multi-wavelength photometry from the U band to 8 μm to determine stellar mass, age, dust attenuation, and star formation rate. Using our SED fitting tool, which takes into account nebular emission, we explore a wide parameter space. We also explore a set of different star formation histories. Results. Nebular emission is found to significantly affect the determination of the physical parameters for the majority of z ∼ 3−6 LBGs. We identify two populations of galaxies by determining the importance of the contribution of emission lines to broadband fluxes. We find that ∼65% of LBGs show detectable signs of emission lines, whereas ∼35% show weak or no emission lines. This distribution is found over the entire redshift range. We interpret these groups as actively star-forming and more quiescent LBGs, respectively. We find that it is necessary to considerer SED fits with very young ages (<50 Myr) to reproduce some colours affected by strong emission lines. Other arguments favouring episodic star formation and relatively short star formation timescales are also discussed. Considering nebular emission generally leads to a younger age, lower stellar mass, higher dust attenuation, higher star formation rate, and a large scatter in the SFR-M relation. Our analysis yields a trend of increasing specific star formation rate with redshift, as predicted by recent galaxy evolution models. Conclusions. The physical parameters of approximately two thirds of high redshift galaxies are significantly modified when we account for nebular emission. The SED models, which include nebular emission shed new light on the properties of LBGs with numerous important implications.

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Section: Evolution Of the Physical Properties From Z ∼ 3 To Z ∼mentioning

confidence: 99%

Properties ofz~ 3–6 Lyman break galaxies

Barros

Schaerer

Stark

2014

A&A

156

205

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“…With the aim of understanding the different parameters governing the Lyα escape and observability, many studies, both observational and theoretical, have found an apparent variation of the Lyα strength with the UV luminosity (Shapley et al 2003;Ando et al 2006;Ouchi et al 2008;Verhamme et al 2008;Vanzella et al 2009;Pentericci et al 2009;Balestra et al 2010;Stark et al 2010;Schaerer et al 2011;Shimizu et al 2011). In particular, the data show a lack of high Lyα equivalent width in luminous LBGs.…”

Section: Lyα Equivalent Width As a Function Of Uv Luminositymentioning

confidence: 99%

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

Atek

Kunth

Schaerer

et al. 2014

A&A

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Context. Among the different observational techniques used to select high-redshift galaxies, the hydrogen recombination line Lymanalpha (Lyα) is of particular interest because it gives access to the measurement of cosmological quantities such as the star formation rate (SFR) of distant galaxy populations. However, interpreting this line and calibrating such observables are still subject to serious uncertainties. Aims. In this context, it important to understand the mechanisms responsible for the attenuation of Lyα emission, and under what conditions the Lyα emission line can be used as a reliable star formation diagnostic tool. Methods. We used a sample of 24 Lyα emitters at z ∼ 0.3 with an optical spectroscopic follow-up to calculate the Lyα escape fraction and its dependence upon different physical properties. We also examined the reliability of Lyα as a SFR indicator. We combined these observations with a compilation of Lyα emitters selected at z = 0−0.3 from the literature to assemble a larger sample. Results. We confirm that the Lyα escape fraction clearly depends on the dust extinction following the relation f esc (Lyα) = C Lyα × 10 −0.4 E(B−V) k Lyα where k Lyα ∼ 6.67 and C Lyα = 0.22. However, the correlation does not follow the expected curve for a simple dust attenuation. A higher attenuation can be attributed to a scattering process, while f esc (Lyα) values that are clearly above the continuum extinction curve can be the result of various mechanisms that can lead to an enhancement of the Lyα output. We also observe that the strength of Lyα and the escape fraction appear unrelated to the galaxy metallicity. Regarding the reliability of Lyα as a SFR indicator, we show that the deviation of SFR(Lyα) from the true SFR (as traced by the UV continuum) is a function of the observed SFR(UV), which can be seen as the decrease in f esc (Lyα) with increasing UV luminosity. Moreover, we observe redshift dependence of this relationship, revealing the underlying evolution of f esc (Lyα) with redshift.

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“…Some studies have reported the inverse relationship between Lyα EW and UV luminosity (e.g., Shapley et al 2003;Ando et al 2006;Reddy et al 2008;Stark et al 2010), while others claimed that the relation is not obvious or there is no such relation (e.g., Nilsson et al 2009). Figure 3 shows the Lyα EW as a function of the continuum luminosity M 1300 for our sample.…”

Section: Spectral Propertiesmentioning

confidence: 99%

KECK SPECTROSCOPY OF LYMAN-BREAK GALAXIES AND ITS IMPLICATIONS FOR THE UV-CONTINUUM AND Lyα LUMINOSITY FUNCTIONS ATz> 6

Jiang

Egami

Kashikawa

et al. 2011

ApJ

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We present Keck spectroscopic observations of z > 6 Lyman-break galaxy (LBG) candidates in the Subaru Deep Field (SDF). The candidates were selected as i -dropout objects down to z = 27 AB magnitudes from an ultra-deep SDF z -band image. With the Keck spectroscopy we identified 19 LBGs with prominent Lyα emission lines at 6 z 6.4. The median value of the Lyα rest-frame equivalent widths (EWs) is ∼50 Å, with four EWs > 100 Å. This well-defined spectroscopic sample spans a UV-continuum luminosity range of −21.8 M UV −19.5 (0.6 ∼ 5 L * UV ) and a Lyα luminosity range of (0.3-3) × 10 43 erg s −1 (0.3-3 L * Lyα ). We derive the UV and Lyα luminosity functions (LFs) from our sample at z ∼ 6.2 after we correct for sample incompleteness. We find that our measurement of the UV LF is consistent with the results of previous studies based on photometric LBG samples at 5 < z < 7. Our Lyα LF is also generally in agreement with the results of Lyα-emitter surveys at z ∼ 5.7 and 6.6. This study shows that deep spectroscopic observations of LBGs can provide unique constraints on both the UV and Lyα LFs at z > 6.

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Deficiency of Large Equivalent Width Lyα Emission in Luminous Lyman Break Galaxies at z ~ 5-6?

Cited by 115 publications

References 43 publications

Properties ofz~ 3–6 Lyman break galaxies

Properties ofz~ 3–6 Lyman break galaxies

Influence of physical galaxy properties on Lyαescape in star-forming galaxies

KECK SPECTROSCOPY OF LYMAN-BREAK GALAXIES AND ITS IMPLICATIONS FOR THE UV-CONTINUUM AND Lyα LUMINOSITY FUNCTIONS ATz> 6

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