X-ray properties of He ii λ 1640 emitting galaxies in VANDELS

Saxena, A.; Pentericci, L.; Schneider, R.; Amorín, R.; Bongiorno, A.; Calabró, Antonello; Castellano, M.; Cimatti, A.; Cullen, F.; Fontana, A.; Fynbo, J. P. U.; Hathi, N. P.; McLeod, D. J.; Talia, M.; Zamorani, G.

doi:10.1093/mnras/staa1805

Cited by 29 publications

(19 citation statements)

References 90 publications

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“…The sources detected in the Luo et al ( 2017) catalogue at 𝑧 3 are very likely to be AGN, owing to X-ray luminosities of > 10 42 erg s −1 at these redshifts (e.g. Magliocchetti et al 2020;Saxena et al 2020aSaxena et al , 2021. We identify and remove two sources with counterparts in the X-ray catalogue that are also classified as AGN in the catalogue and therefore, the total number of sources in our final sample comes to 183.…”

Section: Removing Possible Agnmentioning

confidence: 99%

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

Saxena,

Pentericci,

Ellis

et al. 2021

Preprint

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We present Lyman continuum (LyC) radiation escape fraction ( 𝑓 esc ) measurements for 183 spectroscopically confirmed starforming galaxies in the redshift range 3.11 < 𝑧 < 3.53 in the Chandra Deep Field South. We use ground-based imaging to measure 𝑓 esc , and use ground-and space-based photometry to derive galaxy physical properties using spectral energy distribution (SED) fitting. We additionally derive [O ] + H𝛽 equivalent widths (that fall in the observed 𝐾 band) by including nebular emission in the SED fitting. After removing foreground contaminants, we report the discovery of 11 new candidate LyC leakers, with absolute LyC escape fractions, 𝑓 esc in the range 0.07 − 0.52. Most galaxies in our sample (≈ 94%) do not show any LyC leakage, and we place 1𝜎 upper limits of 𝑓 esc < 0.07 through weighted averaging, where the Lyman-break selected galaxies have 𝑓 esc < 0.07 and 'blindly' discovered galaxies with no prior photometric selection have 𝑓 esc < 0.10. We additionally measure 𝑓 esc < 0.09 for extreme emission line galaxies in our sample with rest-frame [O ] + H𝛽 equivalent widths > 300 Å. For the candidate LyC leakers, we do not find a strong dependence of 𝑓 esc on their stellar masses and/or specific star-formation rates, and no correlation between 𝑓 esc and EW 0 ([O ] + H𝛽). We suggest that this lack of correlations may be explained by viewing angle and/or non-coincident timescales of starburst activity and periods of high 𝑓 esc . Alternatively, escaping radiation may predominantly occur in highly localised star-forming regions, thereby obscuring any global trends with galaxy properties. Both hypotheses have important consequences for models of reionisation.

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Section: Removing Possible Agnmentioning

confidence: 99%

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

Saxena,

Pentericci,

Ellis

et al. 2021

Preprint

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“…The studies of Schaerer et al (2019), Simmonds et al (2021), andLebouteiller et al (2017) claim that HMXB/ULX can explain strong He ii emission lines (cf. Saxena et al 2020 andSenchyna et al 2020), but whether a simple physical model can explain all the emission lines from a galaxy in a selfconsistent manner remains uncertain. There are also attempts to explain emission lines from EMPGs by non-uniform density in inter-stellar medium (ISM) (e.g., Berg et al 2021;Izotov et al 2021).…”

Section: Introductionmentioning

confidence: 99%

EMPRESS. VII. Ionizing Spectrum Shapes of Extremely Metal-Poor Galaxies: Uncovering the Origins of Strong HeII and the Impact on Cosmic Reionization

Umeda,

Ouchi,

Nakajima

et al. 2022

Preprint

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Strong high-ionization lines such as He ii of young galaxies are puzzling at high and low redshift. Although recent studies suggest the existence of non-thermal sources, whether their ionizing spectra can consistently explain multiple major emission lines remains a question. Here we derive the general shapes of the ionizing spectra for three local extremely metal-poor galaxies (EMPGs) that show strong He iiλ4686. We parameterize the ionizing spectra composed of a blackbody and power-law radiation mimicking various stellar and non-thermal sources. We use photoionization models for nebulae, and determine seven parameters of the ionizing spectra and nebulae by Markov Chain Monte Carlo methods, carefully avoiding systematics of abundance ratios. We obtain the general shapes of ionizing spectra explaining ∼ 10 major emission lines within observational errors with smooth connections from observed X-ray and optical continua. We find that an ionizing spectrum of one EMPG has a blackbody-dominated shape, while the others have convex downward shapes at > 13.6 eV, which indicate a diversity of the ionizing spectrum shapes. We confirm that the convex downward shapes are fundamentally different from ordinary stellar spectrum shapes, and that the spectrum shapes of these galaxies are generally explained by the combination of the stellar and ultra-luminous X-ray sources. Comparisons with stellar synthesis models suggest that the diversity of the spectrum shapes arises from differences in the stellar age. If galaxies at z 6 are similar to the EMPGs, high energy (> 54.4 eV) photons of the non-stellar sources negligibly contribute to cosmic reionization due to relatively weak radiation.

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“…However the role of X-ray binaries in the ionizing spectra of galaxies is still debated in the literature. Saxena et al (2020) have shown that He II emitters do not seem to differ from other star forming galaxies at z ∼ 3 in their hard X-ray luminosity, while some models (e.g. Simmonds et al 2021) suggest that they may well be responsible for observed He II emission lines, given certain assumptions.…”

Section: The Ionizing Spectra Of Galaxiesmentioning

confidence: 99%

New Insights into the Evolution of Massive Stars and Their Effects on Our Understanding of Early Galaxies

Eldridge¹,

Stanway²

2022

Preprint

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The observable characteristics and subsequent evolution of young stellar populations is dominated by their massive stars. As our understanding of those massive stars and the factors affecting their evolution improves, so our interpretation of distant, unresolved stellar systems can also advance. As observations increasingly probe the distant Universe, and the rare low metallicity starbursts nearby, so the opportunity arises for these two fields to complement one another, and lead to an improved conception of both stars and galaxies. Here we review the current state of the art in modelling of massive star dominated stellar populations, and discuss their applications and implications for interpreting the distant Universe. Our principle findings include:• Binary evolutionary pathways must be included to understand the stellar populations in early galaxies.

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X-ray properties of He ii λ 1640 emitting galaxies in VANDELS

Cited by 29 publications

References 90 publications

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $\mathbf{3.1 \lesssim z \lesssim 3.5}$

EMPRESS. VII. Ionizing Spectrum Shapes of Extremely Metal-Poor Galaxies: Uncovering the Origins of Strong HeII and the Impact on Cosmic Reionization

New Insights into the Evolution of Massive Stars and Their Effects on Our Understanding of Early Galaxies

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