A new technique for finding galaxies leaking Lyman-continuum radiation: [SII]-deficiency

Abstract

The source responsible for the reionization of the Universe is believed to be the population of star-forming galaxies at $z\sim 6$ to 12. The biggest uncertainty concerns the fraction of Lyman-continuum photons that actually escape from the galaxies. In recent years, several relatively small samples of "leaky" galaxies have been uncovered, and clues have begun to emerge as to both the indirect signposts of leakiness and of the conditions/processes that enable the escape of ionizing radiation. In this paper we present the results of a pilot program aimed to test a new technique for finding leaky galaxies---using the weakness of the [SII] nebular emission-lines relative to typical star-forming galaxies as evidence that the interstellar medium is optically-thin to the Lyman continuum. We use the Cosmic Origins Spectrograph on the Hubble Space Telescope to detect significant emerging flux below the Lyman edge in two out of three [SII]-weak star-forming galaxies at $z\sim 0.3$. We show that these galaxies differ markedly in their properties from the class of leaky "Green-Pea" galaxies at similar redshifts: our sample galaxies are more massive, more metal-rich, and less extreme in terms of their stellar population and the ionization state of the interstellar medium. Like the Green Peas, they have exceptionally high star-formation rates per unit area. They also share some properties with the known leaky galaxies at $z\sim 3$, but are significantly dustier. Our results validate a new way to identify local laboratories for exploring the processes that made it possible for galaxies to reionize the Universe.

arXiv commentAccepted for publication in ApJ. 17 pages, 8 figures, 8 tables

References in corpus (39)

• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• On the variation of the Initial Mass Function
• The Dust Content and Opacity of Actively Star-Forming Galaxies
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• Star Formation in the Milky Way and Nearby Galaxies
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• [O III]/[N II] as an Abundance Indicator at High Redshift
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Observational constraints on Cosmic Reionization
• The Cosmic Origins Spectrograph
• The Systematic Properties of the Warm Phase of Starburst-Driven Galactic Winds
• The Evolution of the Intergalactic Medium
• Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies
• Low-redshift Lyman continuum leaking galaxies with high [OIII]/[OII] ratios
• The Keck Lyman Continuum Spectroscopic Survey (KLCS): The Emergent Ionizing Spectrum of Galaxies at $z\sim 3$
• A Library of Theoretical Ultraviolet Spectra of Massive, Hot Stars for Evolutionary Synthesis
• The Characteristic Star Formation Histories of Galaxies at Redshifts z~2-7
• Lyman continuum leaking from the compact star-forming dwarf galaxy J0925+1403
• Extreme Feedback and the Epoch of Reionization: Clues in the Local Universe
• J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons
• Stellar velocity dispersions and emission line properties of SDSS-III/BOSS galaxies
• The Lyman-Continuum Photon Production Efficiency xi_{ion} of z~4-5 Galaxies from IRAC-based Halpha Measurements: Implications for the Escape Fraction and Cosmic Reionization
• A Local Clue to the Reionization of the Universe
• The Optical Depth of H II Regions in the Magellanic Clouds
• Direct Lyman continuum and Lyman-alpha escape observed at redshift 4
• Direct Detection of Lyman Continuum Escape from Local Starburst Galaxies with the Cosmic Origins Spectrograph
• Measuring the Physical Conditions in High-Redshift Star-Forming Galaxies: Insights from KBSS-MOSFIRE
• Accurately predicting the escape fraction of ionizing photons using restframe ultraviolet absorption lines
• Local Lyman Break Galaxy Analogs: The Impact of Massive Star-forming Clumps on the Interstellar Medium and the Global Structure of Young, Forming Galaxies
• New Insights on Ly-alpha and Lyman Continuum Radiative Transfer in the Greenest Peas
• Ionising the Intergalactic Medium by Star Clusters: The first empirical evidence
• Spectroscopic Measurements of the Far-Ultraviolet Dust Attenuation Curve at z~3
• Indirect Evidence for Escaping Ionizing Photons in Local Lyman Break Galaxy Analogs
• Ly$\alpha$-Lyman Continuum connection in 3.5 < z < 4.3 star-forming galaxies from the VUDS survey

Cited by in corpus (45)

• Large Population of ALMA Galaxies at z>6 with Very High [OIII]88um to [CII]158um Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?
• The Low-Redshift Lyman Continuum Survey I: New, Diverse Local Lyman-Continuum Emitters
• The Low-Redshift Lyman Continuum Survey II: New Insights into LyC Diagnostics
• The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift
• The origin of the escape of Lyman alpha and ionizing photons in Lyman Continuum Emitters
• Optically-Thin Spatially-Resolved Mg II Emission Maps the Escape of Ionizing Photons
• The Low-Redshift Lyman Continuum Survey. Unveiling the ISM properties of low-$z$ Lyman continuum emitters
• Closing in on the sources of cosmic reionization: first results from the GLASS-JWST program
• Strong Lyman continuum emitting galaxies show intense CIV 1550 emission
• New Methods for Identifying Lyman Continuum Leakers and Reionization-Epoch Analogues
• The Low-redshift Lyman-continuum Survey: [S II]-deficiency and the leakage of ionizing radiation
• Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies
• Tracing Lyman-alpha and Lyman Continuum Escape in Galaxies with Mg II Emission
• The mass-metallicity relation at z~1-2 and its dependence on star formation rate
• MgII in the JWST Era: a Probe of Lyman Continuum Escape?
• Inferring the HII region escape fraction of ionizing photons from infrared emission lines in metal-poor star-forming dwarf galaxies
• Two Modes of LyC Escape From Bursty Star Formation: Implications for [C II] Deficits and the Sources of Reionization
• SPICE: the connection between cosmic reionisation and stellar feedback in the first galaxies
• Physics of Prodigious Lyman Continuum Leakers
• The Low-Redshift Lyman Continuum Survey: Optically Thin and Thick Mg II Lines as Probes of Lyman Continuum Escape
• Spectral Shapes of the Lya Emission from Galaxies. II. the influence of stellar properties and nebular conditions on the emergent Lya profiles
• Inferring the properties of the sources of reionization using the morphological spectra of the ionized regions
• Physical Properties of Massive Compact Starburst Galaxies with Extreme Outflows
• VLT/XShooter spectroscopy of Lyman Break Analogs: direct method O/H abundances and nitrogen enhancements
• No correlation of the Lyman continuum escape fraction with spectral hardness
• A bottom-up search for Lyman-continuum leakage in the Hubble Ultra Deep Field
• Linking Mg II and [O II] spatial distribution to ionizing photon escape in confirmed LyC leakers and non-leakers
• A systematic study of galactic outflows via fluorescence emission: implications for their size and structure
• Low-redshift Lyman Continuum Survey: Radio continuum properties of low-$z$ Lyman continuum emitters
• Lyman continuum leaker candidates among highly ionised, low-redshift dwarf galaxies selected from HeII
• Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe
• Linking UV spectral properties of MUSE Ly-alpha emitters at z>3 to Lyman continuum escape
• The Lyman-alpha and Continuum Origins Survey. I. Survey description and Ly$\alpha$ imaging
• The leakage of Lyman-continuum photons from a major merger at $z\sim 1$
• DIISC-II: Unveiling the Connections between Star Formation and ISM in the Extended Ultraviolet Disk of NGC 3344
• The Lyman-alpha and Continuum Origins Survey II: the connection between the escape of ionizing radiation and Lyman-alpha halos in star-forming galaxies
• The Importance of Dust Distribution in Ionizing-photon Escape: NIRCam and MIRI Imaging of a Lyman Continuum-emitting Galaxy at z ~ 3.8
• Ionizing Radiation Escape from Low-Redshift Galaxies and Its Connection to Cosmic Reionization
• Inferring the Distribution of the Ionising Photon Escape Fraction
• Detections of [C II] 158 $\mu$m and [O III] 88 $\mu$m in a Local Lyman Continuum Emitter, Mrk 54, and its Implications to High-redshift ALMA Studies
• Limits to Ionization-Parameter Mapping as a Diagnostic of HII Region Optical Depth
• The Ly$\alpha$ and Continuum Origins Survey. III. Investigating the Link between Galaxy Morphology, Merger Properties and LyC Escape
• SDSS-IV MaNGA: an observational evidence of density bounded region in a Lyman-$\alpha$ emitter
• A Lyman continuum analysis for $\sim 100$ galaxies at $z_{\text{spec}}\sim 3$ in the Abell 2744 Cluster Field
• Unveiling an old disk around a massive young leaking blueberry in SDSS-IV MaNGA