The Lyman Alpha Reference Sample. X. Predicting Lyα Output from Star-forming Galaxies Using Multivariate Regression*

Runnholm, Axel; Hayes, Matthew; Melinder, Jens; Rivera-Thorsen, T. Emil; Östlin, Göran; Cannon, John; Kunth, D.

doi:10.3847/1538-4357/ab7a91

Cited by 39 publications

(35 citation statements)

References 77 publications

(108 reference statements)

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“…It is well-understood that starburst regions, escaping Lyα photons, are often associated with dust (Atek et al 2009;Hayes 2015;Runnholm et al 2020). The distribution of these dust around starburst regions may be dense and/or porous, as also seen in the present study (see Fig.…”

Section: Discussionsupporting

confidence: 80%

SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$α$ emitter

Paswan,

Saha,

Leitherer

et al. 2021

Preprint

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Using Integral Field Unit (IFU) spectroscopy, we present here the spatially resolved morphologies of [SII]λ6717,6731/Hα and [SII]λ6717,6731/[OIII]λ5007 emission line ratios for the first time in a Blueberry Lyman-α emitter (BBLAE) at z ∼ 0.047. Our derived morphologies show that the extreme starburst region of the BBLAE, populated by young ( 10 Myr), massive Wolf-Rayet stars, is [SII]-deficient, while the rest of the galaxy is [SII]-enhanced. We infer that the extreme starburst region is density-bounded (i.e., optically thin to ionizing photons), and the rest of the galaxy is ionization-bounded − indicating a Blister-type morphology. We find that the previously reported small escape fraction (10%) of Lyα photons is from our identified densitybounded HII region of the BBLAE. This escape fraction is likely constrained by a porous dust distribution.We further report a moderate correlation between [SII]-deficiency and inferred Lyman Continuum (LyC) escape fraction using a sample of confirmed LyC leakers studied in the literature, including the BBLAE studied here. The observed correlation also reveals its dependency on the stellar mass and gas-phase metallicity of the leaky galaxies. Finally, the future scope and implications of our work are discussed in detail.

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Section: Discussionsupporting

confidence: 80%

SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$α$ emitter

Paswan,

Saha,

Leitherer

et al. 2021

Preprint

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“…In observations there is a large scatter between the starformation rate inferred from Lyα luminosity compared to UV based estimates (Santos et al 2020;Runnholm et al 2020). Typically, the median SFR estimate from Lyα exceeds that from UV measurements below ∼ 10 M /yr, but decreases above this value.…”

Section: Model Limitationsmentioning

confidence: 99%

The physical origins and dominant emission mechanisms of Lyman-alpha halos: results from the TNG50 simulation in comparison to MUSE observations

Byrohl,

Nelson,

Behrens

et al. 2020

Preprint

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Extended Lyman-alpha emission around galaxies and quasars at high redshift is now commonly detected through stacking as well as surrounding individual galaxies. Despite the increasing samples and the extensive characterization through surface brightness profiles, the physical origin of these Lyman-alpha halos (LAHs), as well as their relationships to galaxies, quasars, circumgalactic gas, and other environmental factors remains unclear. We present results from our new Lyman-alpha full radiative transfer code voroILTIS which runs directly on the unstructured Voronoi tessellation of cosmological hydrodynamical simulations. We use TNG50, the highest resolution run of the IllustrisTNG suite, and simulate LAHs from redshift z = 2 to z = 5, focusing on star-forming galaxies with 8.0 < log 10 (M /M ) < 10.5. We present the predictions for the stacked radial surface brightness profiles of Lyα as a function of galaxy mass and redshift. Comparison with data from the MUSE UDF at z > 3 reveals a promising level of agreement. We measure the correlations of LAH size and central brightness with galaxy properties, finding that at intermediate masses 8.5 ≤ log 10 (M /M ) ≤ 9.5, LAH sizes roughly double from z = 2 to z = 5. Finally, we decompose the profiles into contributions from different sources, namely diffuse emission from recombinations and de-excitations, and scattered photons from star-forming regions. In our simulations, we find rescattered photons from star-forming regions to be the major source in observed LAHs. Unexpectedly, we find that the flattening of LAH profiles at large radii becomes dominated by photons originating from other nearby, more massive halos, rather than diffuse emission itself.

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“…In the face of this complexity, it seems that the determination of leakiness based on indirect signposts can only be done on a statistical basis rather than for individual objects (cf. Runnholm et al 2020 for predicting Lyα radiation using multivariate regression). This reinforces the need for large samples, which was the −0.2) are LCEs, but only weak (albeit statistically significant) correlations are found with fesc (see Table 1).…”

Section: Implications For Escape Fractionsmentioning

confidence: 99%

The Low-redshift Lyman-continuum Survey: [S II]-deficiency and the leakage of ionizing radiation

Wang,

Heckman,

Amorín

et al. 2021

Preprint

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The relationship between galaxy characteristics and the reionization of the universe remains elusive, mainly due to the observational difficulty in accessing the Lyman continuum (LyC) at these redshifts. It is thus important to identify low-redshift LyC-leaking galaxies that can be used as laboratories to investigate the physical processes that allow LyC photons to escape. The weakness of the [S ii] nebular emission lines relative to typical star-forming galaxies has been proposed as a LyC predictor. In this paper, we show that the [S ii]-deficiency is an effective method to select LyC-leaking candidates using data from the Low-redshift LyC Survey, which has detected flux below the Lyman edge in 35 out of 66 star-forming galaxies with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope. We show that LyC leakers tend to be more [S ii]-deficient and that the fraction of their detections increases as [S ii]-deficiency becomes more prominent. Correlational studies suggest that [S ii]-deficiency complements other LyC diagnostics (such as strong Lyman-α emission and high [O iii]/[O ii]). Our results verify an additional technique by which reionization-era galaxies could be studied.

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The Lyman Alpha Reference Sample. X. Predicting Lyα Output from Star-forming Galaxies Using Multivariate Regression*

Cited by 39 publications

References 77 publications

SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$α$ emitter

SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$α$ emitter

The physical origins and dominant emission mechanisms of Lyman-alpha halos: results from the TNG50 simulation in comparison to MUSE observations

The Low-redshift Lyman-continuum Survey: [S II]-deficiency and the leakage of ionizing radiation

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