The Lyman Alpha Reference Sample: Extended Lyman Alpha Halos Produced at Low Dust Content

Hayes, Matthew; Östlin, Göran; Schaerer, D.; Verhamme, Anne; Mas-Hesse, J. M.; Adamo, Angela; Atek, Hakim; Cannon, John; Duval, Florent; Guaita, L.; Herenz, Edmund Christian; Kunth, D.; Laursen, Peter; Melinder, Jens; Orlitová, Ivana; Otí-Floranes, H.; Sandberg, Andreas

doi:10.1088/2041-8205/765/2/l27

Cited by 151 publications

(208 citation statements)

References 39 publications

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“…Comparing this with fig. 3 from Hayes et al 2013, we confirm that this galaxy is comparable to this sample of local galaxies regarding Lyα/continuum extension in both absolute and relative scales of Lyα and continuum.…”

Section: Surface Brightness Profilessupporting

confidence: 81%

“…We compare this single exponential scale length with similar objects in the local Universe -the LARS (Hayes et al 2013) -a sample of local (z <0.18) star bursting galaxies. Hayes et al (2013) measure the Petrosian radius (R P20 ) -the radius at which the local surface brightness is 20 per cent the average surface brightness inside of R -of 14 local galaxies finding that these are generally substantially larger in Lyα than in the FUV.…”

Section: Surface Brightness Profilesmentioning

confidence: 99%

“…Hayes et al (2013) measure the Petrosian radius (R P20 ) -the radius at which the local surface brightness is 20 per cent the average surface brightness inside of R -of 14 local galaxies finding that these are generally substantially larger in Lyα than in the FUV. As in the case of the scale lengths, it is desirable to compare intrinsic (deconvolved from the PSF) R P20 values, which we estimate by converting the intrinsic scale lengths with R P20 = 3.62 r 0 .…”

Section: Surface Brightness Profilesmentioning

confidence: 99%

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A young star-forming galaxy at z = 3.5 with an extended Lyman α halo seen with MUSE

Patrício¹,

Richard²,

Verhamme

2015

Proc. IAU

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Spatially resolved studies of high-redshift galaxies, an essential insight into galaxy formation processes, have been mostly limited to stacking or unusually bright objects. We present here the study of a typical (L * , M = 6 × 10 9 M ) young lensed galaxy at z = 3.5, observed with Multi Unit Spectroscopic Explorer (MUSE), for which we obtain 2D resolved spatial information of Lyα and, for the first time, of C III] emission. The exceptional signal-to-noise ratio of the data reveals UV emission and absorption lines rarely seen at these redshifts, allowing us to derive important physical properties (T e ∼ 15600 K, n e ∼ 300 cm −3 , covering fraction f c ∼ 0.4) using multiple diagnostics. Inferred stellar and gas-phase metallicities point towards a low-metallicity object (Z stellar = ∼0.07 Z and Z ISM < 0.16 Z ). The Lyα emission extends over ∼10 kpc across the galaxy and presents a very uniform spectral profile, showing only a small velocity shift which is unrelated to the intrinsic kinematics of the nebular emission. The Lyα extension is approximately four times larger than the continuum emission, and makes this object comparable to low-mass LAEs at low redshift, and more compact than the Lyman-break galaxies and Lyα emitters usually studied at high redshift. We model the Lyα line and surface brightness profile using a radiative transfer code in an expanding gas shell, finding that this model provides a good description of both observables.Key words: techniques: imaging spectroscopy -galaxies: abundances -galaxies: highredshift -galaxies: individual: SMACSJ2031.8-4036. I N T RO D U C T I O NDuring the past few decades, our understanding of galaxy formation and evolution has made significant progress thanks to the hundreds of high-redshift (z > 3) galaxies which have been detected in dedicated observing campaigns (e.g. Shapley et al. 2003;Vanzella et al. 2009;Stark et al. 2013). The main spectral feature used to confirm the distances of these galaxies is the Lyα emission, since it E-mail: vera.patricio@univ-lyon1.fr (VP); johan.richard@univ-lyon1.fr (JR) is the brightest emission line we can observe in distant sources. Unfortunately, many of these objects are too faint to show any other emission line at rest-frame UV wavelengths or, even less likely, continuum and absorption lines, offering a limited picture of the characteristics of high-redshift galaxies. The complexity of the Lyα resonant process, which depends not only on the gas dynamics but also on gas density and dust content, also requires the observation of non-resonant lines in order to robustly probe the physical properties of such galaxies.Stacking techniques, which combine spectra or images of dozens or even hundreds of objects in order to increase signal-to-noise ratio (e.g.

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Section: Surface Brightness Profilessupporting

confidence: 81%

Section: Surface Brightness Profilesmentioning

confidence: 99%

Section: Surface Brightness Profilesmentioning

confidence: 99%

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A young star-forming galaxy at z = 3.5 with an extended Lyman α halo seen with MUSE

Patrício¹,

Richard²,

Verhamme

2015

Proc. IAU

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“…Instead, giant Lyα nebulae, powered by active galactic nuclei, have been studied by a few authors to assess the role of HI scattering and Lyα radiative transfer effects (e.g., Humphrey et al 2013a;Prescott et al 2015) Local starbursts (Overzier et al 2008(Overzier et al , 2009(Overzier et al , 2010Hayes et al 2013Hayes et al , 2014Petty et al 2014;Östlin et al 2014) are unique laboratories for studying the rest-frame UV in detail and optical light distribution, morphology, and to investigate the mechanisms, that allow Lyα photons to escape. In Östlin et al (2014, hereafter Paper I) we presented the Lyman alpha reference sample (LARS), which is composed of 14 star-forming galaxies at z < 0.2.…”

Section: Introductionmentioning

confidence: 99%

“…Throughout we adopt AB magnitudes and assume a ΛCDM cosmology of (H 0 , Ω m , Ω Λ ) = (70 km s −1 Mpc −1 , 0.3, 0.7) as in Hayes et al (2013Hayes et al ( , 2014.…”

Section: Introductionmentioning

confidence: 99%

The Lyman alpha reference sample

Guaita

Melinder

Hayes

et al. 2015

A&A

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Context. The transport of Lyα photons in galaxies is a complex process and the conditions under which Lyα photons manage to escape from certain galaxies is still under investigation. The Lyman alpha reference sample (LARS) is a sample of 14 local starforming galaxies, designed to study Lyα in detail and relate it to rest-frame UV and optical emission. Aims. With the aim of identifying rest-frame UV and optical properties, which are typical of Lyα emitters (LAEs, galaxies with EW(Lyα) > 20 Å) at both low and high redshift, we investigated the morphological properties of the LARS galaxies, in particular the ones that exhibit intense Lyα radiation. Methods. We measured sizes and morphological parameters in the continuum, Lyα, and Hα images. We studied morphology by using the Gini coefficient vs. M20 and asymmetry vs. concentration diagrams. We then simulated LARS galaxies at z ∼ 2 and 5.7, performing the same morphological measurements. We also investigated the detectability of LARS galaxies in current deep field observations. The subsample of LAEs within LARS (LARS-LAEs) was stacked to provide a comparison to stacking studies performed at high redshift. Results. LARS galaxies have continuum size, stellar mass, and rest-frame absolute magnitude typical of Lyman break analogues in the local Universe and also similar to 2 < z < 3 star-forming galaxies and massive LAEs. LARS optical morphology is consistent with the one of merging systems, and irregular or starburst galaxies. For the first time we quantify the morphology in Lyα images: even if a variety of intrinsic conditions of the interstellar medium can favour the escape of Lyα photons, LARS-LAEs appear small in the continuum, and their Lyα is compact. LARS galaxies tend to be more extended in Lyα than in the rest-frame UV. It means that Lyα photons escape by forming haloes around HII regions of LARS galaxies. Conclusions. The stack of LARS-LAE Lyα images is peaked in the centre, indicating that the conditions, which make a galaxy an LAE, tend to produce a concentrated surface brightness profile. On the other hand, the stack of all LARS galaxies is shallower and more extended. This can be caused by the variety of dust and HI amount and distribution, which produces a more complex, patchy, and extended profile, like the one observed for Lyman break galaxies that can contribute to the stack. We cannot identify a single morphological property that controls whether a galaxy emits a net positive Lyα flux. However, the LARS-LAEs have continuum properties consistent with merging systems.

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Revisiting the emission line source detection problem in integral field spectroscopic data

Herenz

2023

Astron Nachr

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We present a 3-dimensional matched filtering approach for the blind search of faint emission-line sources in integral-field spectroscopic datasets. The filter is designed to account for the spectrally rapidly varying background noise due to the telluric air glow spectrum. A software implementation of this matched filtering search is implemented in an updated version of the Line Source Detection Cataloguing tool (LSDCat2.0). Using public data from the MUSE-Wide survey we show how the new filter design provides higher detection significances for faint emission line sources buried in between atmospheric [OH]-bands at 𝜆 ≳ 7000 Å. We also show how, for a given source parameterization, the selection function of the improved algorithm can be derived analytically from the variances of the data. We verify this analytic solution against source insertion and recovery experiments in the recently released dataset of the MUSE eXtreme Deep Field (MXDF). We then illustrate how the selection function has to be rescaled for 3D emission line source profiles that are not fully congruent with the template. This procedure alleviates the construction of realistic selection functions by removing the need for computationally cumbersome source insertion and recovery experiments.

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The Lyman Alpha Reference Sample: Extended Lyman Alpha Halos Produced at Low Dust Content

Cited by 151 publications

References 39 publications

A young star-forming galaxy at z = 3.5 with an extended Lyman α halo seen with MUSE

A young star-forming galaxy at z = 3.5 with an extended Lyman α halo seen with MUSE

The Lyman alpha reference sample

Revisiting the emission line source detection problem in integral field spectroscopic data

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