An Observational Pursuit for Population III Stars in a Lyα Emitter at
                    <i>z</i>
                    = 6.33 through He
                    <scp>ii</scp>
                    Emission

Nagao, Tohru; Motohara, Kentaro; Maiolino, R.; Marconi, A.; Taniguchi, Yoshiaki; Aoki, Kentaro; Ajiki, Masaru; Shioya, Yasuhiro

doi:10.1086/497135

Cited by 39 publications

(42 citation statements)

References 44 publications

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“…The 3σ upper limits for the N v emission are 5.7 × 10 −18 erg s −1 cm −2 and 6.9 × 10 −18 erg s −1 cm −2 for these two objects, assuming the same velocity widths as Lyα. However, we cannot completely rule out the possibility that one or both of these two objects are AGNs, since some high-z narrow-line radio galaxies show very weak N v compared with Lyα (e.g., De Breuck et al 2000;Nagao et al 2006; see also Malkan et al 1996).…”

Section: Resultsmentioning

confidence: 95%

“…Therefore our NB921-depressed i -dropout galaxy sample offers fascinating targets for observational searches for PopIII stars, which will be an important topic in the forthcoming decade (see, e.g., Jimenez & Haiman 2006). We have already searched for an observational signature in one of the NB921-depressed idropout galaxies, SDF J132440.6+273607 (#4; Nagao et al 2005b), through He iiλ1640 emission (see, e.g., Tumlinson & Shull 2000;Oh et al 2001;Schaerer 2002Schaerer , 2003. Although the He iiλ1640 emission was not detected in this object, similar observations will provide important constraints on theoretical PopIII models (e.g., Scannapieco et al 2003;Nagao et al 2005b).…”

Section: Implication For the Stellar Populationmentioning

confidence: 99%

“…The reason for adopting the selection criterion based on the sky noise is that one of our motivations in the photometric selection is to construct a sample of the target objects for our spectroscopic observations to find candidates for PopIII-hosting galaxies (see Nagao et al 2005b). Due to the limited observing time, we had to focus on convincing candidates, i.e., objects with a significant NB921 depression with respect to the sky error.…”

Section: The Success Rate Of the Nb921-depressed I -Dropout Selectionmentioning

confidence: 99%

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High-redshift Ly$\mathsf{\alpha}$ emitters with a large equivalent width

Nagao

Murayama

Maiolino

et al. 2007

A&A

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We report new follow-up spectroscopy of i -dropout galaxies with an NB921-band depression found in the Subaru Deep Field. The NB921-depressed i -dropout selection method is expected to select galaxies with large equivalent-width Lyα emission over a wide redshift range, 6.0 < ∼ z < ∼ 6.5. Two of four observed targets show a strong emission line with a clear asymmetric profile, identified as Lyα emitters at z = 6.11 and 6.00. Their rest-frame equivalent widths are 153 Å and 114 Å, which are lower limits on the intrinsic equivalent widths. Through our spectroscopic observations (including previous ones) of NB921-depressed i -dropout galaxies, we identified 5 galaxies in total with a rest-frame equivalent width larger than 100 Å at 6.0 < ∼ z < ∼ 6.5 out of 8 photometric candidates, which suggests that the NB921-depressed i -dropout selection method is possibly an efficient way to search for Lyα emitters with a large Lyα equivalent width, in a wider redshift range than with usual narrow-band excess techniques. By combining these findings with our previous observational results, we infer that the fraction of broad-band selected galaxies having a rest-frame equivalent width larger than 100 Å is significantly higher at z ∼ 6 (the cosmic age of ∼1 Gyr) than that at z ∼ 3 (∼2 Gyr), being consistent with the idea that the typical stellar population of galaxies is significantly younger at z ∼ 6 than that at z ∼ 3. The NB921-depressed i -dropout galaxies may be interesting candidates for hosts of massive, zero-metallicity Population III stars.

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Section: Resultsmentioning

confidence: 95%

Section: Implication For the Stellar Populationmentioning

confidence: 99%

Section: The Success Rate Of the Nb921-depressed I -Dropout Selectionmentioning

confidence: 99%

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High-redshift Ly$\mathsf{\alpha}$ emitters with a large equivalent width

Nagao

Murayama

Maiolino

et al. 2007

A&A

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“…However, some of our galaxies have SFR Lyα /SFR UV larger than 1. These galaxies could be in the very early phases of star formation activity, in which SFR UV values are underestimated (Schaerer 2000; see also Nagao et al 2004Nagao et al , 2005. Indeed by checking the best fit ages estimated from the multiwavelength SED, we see that most of these galaxies having SFR Lyα /SFR UV > 1 are extremely young, with ages of a few tens of Myr.…”

Section: Star Formation Ratesmentioning

confidence: 84%

The physical properties of Lyαemitting galaxies: not just primeval galaxies?

Pentericci¹,

Grazian²,

Fontana³

et al. 2008

A&A

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Aims. We have analyzed a sample of Lyman break galaxies from z ∼ 3.5 to z ∼ 6 selected from the GOODS-S field as B, V, and i-dropouts, and with spectroscopic observations showing that they have the Lyα line in emission. Our main aim is to investigate their physical properties and their dependence on the emission line characteristic and to shed light on the relation between galaxies with Lyα emission and the general LBG population. Methods. The objects were selected from their optical continuum colors and then spectroscopically confirmed by the GOODS collaboration and other campaigns. From the public spectra we derived the main properties of the Lyα emission such as total flux and rest frame EW. We then used complete photometry, from U band to mid-infrared from the GOODS-MUSIC database, and through standard spectro-photometric techniques we derived the physical properties of the galaxies, such as total stellar mass, stellar ages, star formation rates, and dust content. Finally we investigated the relation between emission line and physical properties. Results. Although most galaxies are fit by young stellar populations, a small but non negligible fraction has SEDs that cannot be represented well by young models and require considerably older stellar component, up to ∼1 Gyr. There is no apparent relation between age and EW: some of the oldest galaxies have high line EW, and should be also selected in narrow-band surveys. Therefore not all Lyα emitting galaxies are primeval galaxies in the very early stages of formation, as is commonly assumed. We also find a range of stellar populations, with masses from 5 × 10 8 M to 5 × 10 10 M and SFR from few to 60 M yr −1 . Although there is no net correlation between mass and EW, we find a significant lack of massive galaxies with high EW, which could be explained if the most massive galaxies were either dustier and/or if they contained more neutral gas than less massive objects. Finally we find that more than half of the galaxies contain small but non negligible amounts of dust: the mean E(B − V) derived from the SED fit and the EW are well-correlated, although with a large scatter, as already found at lower redshift.

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“…With the detection of other emission lines and/or a recognisable continuum, a spectrum can however provide a rich source of information about physical conditions and chemical composition. Of particular interest for the identification of primordial starforming objects are the so-called "dual-emitters": sources that emit both Lyα and the He ii line at 1640 Å (Dawson et al 2004;Nagao et al 2005;Ouchi et al 2008) which are interpreted as very metal-poor nebulae ionized by massive, hot and presumably metal-free stars. So far, intermediate band imaging surveys have not been very successful in discovering genuine, stellar-ionized H/He ii dual emitters ).…”

Section: Introductionmentioning

confidence: 99%

Ly$\mathsf{\alpha}$ emitters in the GOODS-S field

Raiter¹,

Fosbury

Teimoorinia

2010

A&A

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Context. The Great Observatories Origins Deep Survey (GOODS) has provided us with one of the deepest multi-wavelength views of the distant universe. The combination of multi-band photometry and optical spectroscopy has resulted in the identification of sources whose redshifts extend to values in excess of six. Amongst these distant sources are Lyα emitters whose nature must be deduced by clearly identifying the different components that contribute to the measured SED. Aims. From a sample of Lyα emitters in the GOODS-S field with uncontaminated photometry and optical (red) spectroscopy, we select a spatially compact object at a redshift of 5.563 (Lyα) that shows a second emission line, identified as N iv] 1486 Å. The SED is modelled in a way that accounts for both the N iv] line emission and the photometry in a self-consistent way.Methods. The photoionization code CLOUDY is used to calculate a range of nebular models as a function of stellar ionizing source temperature, ionization parameter, density and nebular metallicity. We compare the theoretical and observed magnitudes and search for the model parameters that also reproduce the observed N iv] luminosity and equivalent width.Results. A nebular model with a hot blackbody ionizing source of around 100 kK and a nebular metallicity of ∼5% of solar is able to fit the observed SED and, in particular, explain the large apparent Balmer break which is inferred from the pure stellar population model fitting conventionally applied to multi-band photometric observations. In our model, an apparent spectral break is produced by strong [O iii] 4959, 5007 Å emission falling in one of the IR bands (IRAC1 in this case). A lower limit on the total baryonic mass of a model of this type is 3.2 × 10 8 M . Conclusions. It is argued that objects with Lyα emission at high redshift that show an apparent Balmer break may have their SED dominated by nebular emission and so could possibly be identified with very young starbursting galaxies rather than massive evolved stellar populations. Detailed studies of these emission nebulae with large telescopes will provide a unique insight into very early chemical evolution.

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An Observational Pursuit for Population III Stars in a Lyα Emitter at z = 6.33 through He ii Emission

Cited by 39 publications

References 44 publications

High-redshift Ly$\mathsf{\alpha}$ emitters with a large equivalent width

High-redshift Ly$\mathsf{\alpha}$ emitters with a large equivalent width

The physical properties of Lyαemitting galaxies: not just primeval galaxies?

Ly$\mathsf{\alpha}$ emitters in the GOODS-S field

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