Observing the First Galaxies

Dunlop, James

doi:10.1007/978-3-642-32362-1_5

Cited by 58 publications

(52 citation statements)

References 327 publications

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“…For similar reasons the standard grain growth suffered by grains during their residence time in molecular clouds (MC) of contemporary galaxies cannot increase the amount of dust by considerable amounts . Thus, albeit quasar host galaxies show remarkably high dust masses (Beelen et al 2006;Micha lowski et al 2010), in general the dust-to-gas ratio towards highredshift rapidly decreases (Dunlop 2013) as also witnessed by the observed steepening of early galaxies UV spectra. This does not come as a complete surprise given that the average metallicity of the Universe increases with time.…”

Section: Motivationmentioning

confidence: 92%

The infrared-dark dust content of high redshift galaxies

Ferrara

Hirashita

Ouchi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a theoretical model aimed at explaining the IRX-β relation for high redshift (z > ∼ 5) galaxies. Recent observations (Capak et al. 2015;Bouwens et al. 2016) have shown that early Lyman Break Galaxies, although characterized by a large UV attenuation (e.g. flat UV β slopes), show a striking FIR deficit, i.e. they are "infrareddark". This marked deviation from the local IRX-β relation can be explained by the larger molecular gas content of these systems. While dust in the diffuse ISM attains relatively high temperatures (T d 45 K for typical size a = 0.1µm; smaller grains can reach T d > ∼ 60 K), a sizable fraction of the dust mass is embedded in dense gas, and therefore remains cold. If confirmed, the FIR deficit might represent a novel, powerful indicator of the molecular content of high-z galaxies which can be used to pre-select candidates for follow-up deep CO observations. Thus, high-z CO line searches with ALMA might be much more promising than currently thought.

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Section: Motivationmentioning

confidence: 92%

The infrared-dark dust content of high redshift galaxies

Ferrara

Hirashita

Ouchi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…On cosmological scales, outflows are thought to shape the faint-end of the galaxy luminosity function up to the highest redshifts at which galaxies can be observed (Bouwens et al 2014;Dunlop 2013). This complex network of physical processes is collectively known as "feedback".…”

Section: Introductionmentioning

confidence: 99%

ALMA suggests outflows in z ∼ 5.5 galaxies

Gallerani

Pallottini

Feruglio

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of 9 star-forming (SFR = 31 ± 20 M yr −1 ) z ∼ 5.5 galaxies for which the [CII]158µm line has been previously obtained with ALMA. We first fit each line with a Gaussian function and compute the residuals by subtracting the best fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterised by a flux excess of ∼ 0.5 mJy extended over ∼ 1000 km s −1 . Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the [CII] lines, signatures of starburst-driven outflows. We infer an average outflow rate oḟ M = 54±23 M yr −1 , providing a loading factor η =Ṁ/SFR = 1.7±1.3 in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydro-simulations of Dahlia, a z ∼ 6 galaxy (SFR ∼ 100 M yr −1 ) whose feedback-regulated star formation results into an outflow rateṀ ∼ 30 M yr −1 . The quality of the ALMA data is not sufficient for a detailed analysis of the [CII] line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the [CII] line in this sample are required to better characterise feedback at high-z and to understand the role of outflows in shaping early galaxy formation.

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“…In particular, the prominence of the Lyα line at λLyα = 1216Å (1 + z) allows for spectroscopic confirmation of redshift measurements of individual distant galaxies. Lyα sources are also a compelling probe of the cosmic dark ages leading up to reionization -see Dunlop (2013) for a perspective on high-z observations. Historically, Partridge & Peebles (1967a) determined that galaxies from the first billion years after the Big Bang would be powerful emitters of Lyα photons, though observations of these sources eluded us for longer than expected.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, going to higher redshifts introduces physical effects that compete in either strengthening or attenuating the Lyα signal (Latif et al 2011a,b;Dunlop 2013). On one hand, the intergalactic medium (IGM) becomes increasingly neutral at higher z, resulting in a more difficult escape for Lyα photons (Ono et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Ellis et al 2013), with the highest spectroscopically-confirmed source announced at z = 7.51 by Finkelstein et al (2013). Other records have been found using gamma-ray bursts (GRBs), active galactic nuclei (AGN), or (sub-)mm observations of redshifted thermal dust emission (Dunlop 2013). However, it is unclear how these other selection methods relate to Lyα predictions.…”

Section: Introductionmentioning

confidence: 99%

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The Lyman α signature of the first galaxies

Smith¹,

Safranek-Shrader²,

Bromm³

et al. 2015

Monthly Notices of the Royal Astronomical Society

101

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We present the Cosmic Lyman-α Transfer code (COLT), a massively parallel Monte-Carlo radiative transfer code, to simulate Lyman-α (Lyα) resonant scattering through neutral hydrogen as a probe of the first galaxies. We explore the interaction of centrally produced Lyα radiation with the host galactic environment. Lyα photons emitted from the luminous starburst region escape with characteristic features in the line profile depending on the density distribution, ionization structure, and bulk velocity fields. For example, anisotropic ionization exhibits a tall peak close to line centre with a skewed tail that drops off gradually. Idealized models of first galaxies explore the effect of mass, anisotropic H II regions, and radiation pressure driven winds on Lyα observables. We employ mesh refinement to resolve critical structures. We also post-process an ab initio cosmological simulation and examine images captured at various distances within the 1 Mpc 3 comoving volume. Finally, we discuss the emergent spectra and surface brightness profiles of these objects in the context of high-z observations. The first galaxies will likely be observed through the red damping wing of the Lyα line. Observations will be biased toward galaxies with an intrinsic red peak located far from line centre that reside in extensive H II super bubbles, which allows Hubble flow to sufficiently redshift photons away from line centre and facilitate transmission through the intergalactic medium. Even with gravitational lensing to boost the luminosity this preliminary work indicates that Lyα emission from stellar clusters within haloes of M vir < 10 9 M is generally too faint to be detected by the James Webb Space Telescope (JWST).

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Observing the First Galaxies

Cited by 58 publications

References 327 publications

The infrared-dark dust content of high redshift galaxies

The infrared-dark dust content of high redshift galaxies

ALMA suggests outflows in z ∼ 5.5 galaxies

The Lyman α signature of the first galaxies

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