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We present observations with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope (HST) of 11 Lyman continuum (LyC) leaking galaxies at redshifts, z, in the range 0.29–0.43, with oxygen abundances 12+log(O/H) = 7.64–8.16, stellar masses M⋆ ∼ 107.8–109.8 M⊙, and O32 = [O iii] λ5007/[O ii] λ3727 of ∼ 5–20 aiming to detect the C iii] λ1908 emission line. We combine these observations with the optical Sloan Digital Sky Survey (SDSS) spectra for the determination of carbon, nitrogen, and oxygen abundances. Our sample was supplemented by 31 galaxies from the literature, for which carbon, nitrogen, and oxygen abundances can be derived from the HST and SDSS spectra. These additional galaxies, however, do not have LyC observations. We find that log(C/O) for the entire sample at 12+log(O/H) 0.1, including LyC leakers, is systematically higher compared to the rest of the sample with lower metallicity. We find that log(C/O) slightly decreases with increasing M⋆ from ∼ −0.65 at M⋆ = 106 M⊙ to ∼ −0.80 at M⋆ = 109–1010 M⊙, whereas log(N/O) is considerably enhanced at M⋆ > 108 M⊙. The origin of these trends remains basically unknown. A possible solution would be to assume that the upper mass limit of the stellar initial mass function in more massive galaxies is higher. This would result in a higher production of oxygen and a larger fraction of massive stars with stellar wind polluting the interstellar medium with nitrogen.

International audience; We present the discovery and analysis of J1316+2614 at z = 3.6130, a UV-bright star-forming galaxy (MUV ≃ -24.7) with large escape of Lyman continuum (LyC) radiation. J1316+2614 is a young (≃10 Myr) star-forming galaxy with SFR ≃ 500 M⊙ yr-1 and a starburst mass of log(M⋆/M⊙) ≃ 9.7. It shows a very steep UV continuum, βUV = -2.59 ± 0.05, consistent with residual dust obscuration, E(B - V) ≃ 0. LyC emission is detected with high significance (≃17σ) down to 830 Å, for which a very high relative (absolute) LyC escape fraction $f_{\rm esc} \rm (LyC) \simeq 0.92$ (≃0.87) is inferred. The contribution of a foreground or active galactic nucleus contamination to the LyC signal is discussed, but is unlikely. J1316+2614 is the most powerful ionizing source known among the star-forming galaxy population, both in terms of production (QH ≍ 1056 s-1) and escape of ionizing photons ($f_{\rm esc} \rm (LyC) \approx 0.9$). Nebular emission in Ly α, H β, and other rest-frame optical lines are detected, but these are weak ($EW_{0} \rm [H\beta ] \simeq 35$ Å), with their strengths reduced roughly by $\simeq 90{{\ \rm per\ cent}}$. J1316+2614 is the first case known where the effect of large escape of ionizing photons on the strength of nebular lines and continuum emission is clearly observed. Gas inflows are detected in J1316+2614 from the blue-dominated peak Ly α emission (with a blue-to-red peak line ratio Iblue/Ired ≃ 3.7) and redshifted interstellar medium absorption (≃100 km s-1). Our results suggest that J1316+2614 is undergoing a gas compaction event, possibly representing a short-lived phase in the evolution of massive and compact galaxies, where strong gas inflows have triggered an extreme star formation episode and nearly 100 per cent LyC photons are escaping.

Most of the hydrogen in the intergalactic medium (IGM) was rapidly ionized at high-redshifts. While observations have established that reionization occurred, observational constraints on the emissivity of ionizing photons at high-redshift remains elusive. Here, we present a new analysis of the Low-redshift Lyman Continuum Survey (LzLCS) and archival observations, a combined sample of 89 star-forming galaxies at z~0.3 with Hubble Space Telescope observations of their ionizing continua (or Lyman Continuum, LyC). We find a strong (6$\sigma$ significant) inverse correlation between the continuum slope at 1550\r{A} (defined as F$_\lambda\propto\lambda^{\beta}$) and both the LyC escape fraction (f$_{esc}$) and f$_{esc}$ times the ionizing photon production efficiency ($\xi_{ ion}$). On average, galaxies with redder continuum slopes have smaller f$_{esc}$ than galaxies with bluer slopes due to higher dust attenuation. More than 5% (20%) of the LyC emission escapes galaxies with $\beta$, Comment: 14 pages plus appendix. Submitted to MNRAS. Comments encouraged

We present a joint analysis of the galaxy S04590 at z = 8.496 based on NIRSpec, NIRCam, and NIRISS observations obtained as part of the Early Release Observations program of the James Webb Space Telescope (JWST) and the far-infrared [C ii] 158 mu m emission line detected by dedicated Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the physical properties of S04590 from modeling of the spectral energy distribution (SED) and through the redshifted optical nebular emission lines detected with JWST/NIRSpec. The best-fit SED model reveals a low-mass (M-? = 10(7.2)-10(8) M-?) galaxy with a low oxygen abundance of derived from the strong nebular and auroral emission lines. Assuming that [C ii] effectively traces the interstellar medium, we estimate the total gas mass of the galaxy to be M-gas = (8.0 +/- 4.0) x 10(8) M-? based on the luminosity and spatial extent of [C ii]. This yields an exceptionally high gas fraction, f(gas) = M-gas/(M-gas + M-?) ? 90%, though one still consistent with the range expected for low metallicity. We further derive the metal mass of the galaxy based on the gas mass and gas-phase metallicity, which we find to be consistent with the expected metal production from Type II supernovae. Finally, we make the first constraints on the dust-to-gas (DTG) and dust-to-metal (DTM) ratios of galaxies in the epoch of reionization at z ? 6, showing overall low mass ratios of logDTG < -3.8 and logDTM < -0.5, though they are consistent with established scaling relations and in particular with those of the local metal-poor galaxy I Zwicky 18. Our analysis highlights the synergy between ALMA and JWST in characterizing the gas, metal, and stellar content of the first generation of galaxies., Carlsberg Foundation Reintegration Fellowship CF21-0103, VILLUM FONDEN through the Villum Experiment Programme, Carlsberg Foundation 17H06130, Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research (KAKENHI) NAS 5-03127, NAOJ ALMA Scientific Research, Association of Universities for Research in Astronomy, Inc., under NASA 2017-06B, Danmarks Grundforskningsfond CF20-0534 140

We present the average [C ii] 158 μm emission line sizes of UV-bright star-forming galaxies at z ∼ 7. Our results are derived from a stacking analysis of [C ii] 158 μm emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C ii] emission at z ∼ 7 has an effective radius r e of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≲ 6 galaxies. Additionally, we compared the average [C ii] size with 4 < z < 6 galaxies observed by the ALMA Large Program to INvestigate [C ii] at Early times (ALPINE). By analyzing [C ii] sizes of 4 < z < 6 galaxies in two redshift bins, we find an average [C ii] size of r e = 2.2 ± 0.2 kpc and r e = 2.5 ± 0.2 kpc for z ∼ 5.5 and z ∼ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C ii] 158 μm emitting regions at redshift between z ∼ 7 and z ∼ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.

Unusually high N/O abundance ratios were recently reported for a very compact, intensively star-forming object GN-z11 at $z=10.6$ from JWST/NIRSpec observations. We present an empirical comparison with the C, N, and O abundance ratios in Galactic globular clusters (GCs) over a large metallicity range. We show that hot hydrogen-burning nucleosynthesis within supermassive stars (SMS) formed through runaway collisions can consistently explain the observed abundances ratio in GN-z11 and in GCs. This suggests that a proto-globular cluster hosting a SMS could be at the origin of the strong N-enrichment in GN-z11. Our model predicts the behavior of N/O, C/O, and Ne/O ratios as a function of metallicity, which can be tested if high-$z$ objects similar to GN-z11 are detected with JWST in the future. Further studies and statistics will help differentiate the proto-GC scenario from the Wolf-Rayet scenario that we quantify with a population synthesis model, and shed more light on this peculiar object., Comment: Accepted by A&A Letters (revised version; in press)

While there is now a consensus that X-ray binaries (XRBs) are the dominant X-ray sources in the early Universe and play a significant role during the epoch of heating of the intergalactic medium (IGM), recent studies report contradicting results regarding their contribution in the nebular emission of local Universe galaxies. Ultraluminous X-ray sources (ULXs), which dominate the X-ray budget of normal galaxies, may be important interstellar-medium (ISM) ionizing sources. However, their output in the extreme UV (EUV) and soft--X-ray part of the spectrum remains observationally unconstrained. In this paper, we predict the ionizing and heating power from ULX populations under the geometrical beaming scenario, and three models describing the emission from super-critical accretion disks. We find that our theoretical spectra for ULX populations cannot (can) explain the HeII (NeV) emission observed in some galaxies, with their contribution being less (more) important than the underlying stellar population. Stochastic fluctuations in the number of ULXs may allow for equal contributions in the HeII emission, in a fraction of galaxies. We provide average spectra of ULX populations as an input to local, and early-Universe studies. We find that the soft--X-ray emission arising from super-critical accretion is significant for the heating of the IGM, and consistent with recent constraints from the 21-cm cosmic signal. Based on the dependence on the adopted compact-object (CO) mass and accretion model, we encourage efforts in modeling ULX spectra via simulations, and their combination with detailed binary population synthesis models., 8 pages. 6 figures, 1 table. This article has been accepted for publication in the Astronomy & Astrophysics journal. The full Table 1 will be made available via CDS

(abridged) Quantifying the ISM porosity to ionizing photons in nearby galaxies may improve our understanding of the mechanisms leading to Lyman Continuum photons leakage from galaxies. Primitive galaxies with low metal and dust content have been shown to host a more patchy and porous ISM than their high-metallicity counterparts. To what extent this peculiar structure contributes to the leakage of ionizing photons remains to be quantitatively studied. To address these questions we build a refined grid of models including density-bounded regions and a possible contribution of an X-ray source. Using MULTIGRIS, a new Bayesian code based on Monte Carlo sampling, we combine the models as sectors under various assumptions to extract the probability density distributions of the parameters and infer the corresponding escape fractions from H II regions (fesc,HII). We apply this new code to a sample of 39 well-know local starbursting dwarf galaxies from the Dwarf Galaxy Survey. We confirm previous results hinting at an increased porosity to ionizing photons of the ISM in low-metallicity galaxies and provide, for the first time, quantitative predictions for fesc,HII. The predicted fesc,HII for low-metallicity objects span a large range of values, up to 60%, while the values derived for more metal-rich galaxies are globally lower. We also examine the influence of other parameters on the escape fractions, and find that the specific star-formation rate correlates best with fesc,HII . Finally, we provide observational line ratios which could be used as tracers of the photons escaping from density-bounded regions. Although this multi-sector modelling remains too simple to fully capture the ISM complexity, it can be used to preselect galaxy samples with potential leakage of ionizing photons based on current and up-coming spectral data in unresolved surveys of local and high-redshift galaxies., 39 pages, 24 figures, accepted for publication in A&A

We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of seven compact low-mass star-forming galaxies at redshifts, z,in the range 0.3161-0.4276, with various O3Mg2=[OIII]5007/MgII 2796+2803 and Mg2=MgII 2796/MgII 2803 emission-line ratios. We aim to study the dependence of leaking Lyman continuum (LyC) emission on the characteristics of MgII emission together with the dependences on other indirect indicators of escaping ionizing radiation. LyC emission with escape fractions fesc(LyC)=3.1-4.6 per cent is detected in four galaxies, whereas only 1sigma upper limits of fesc(LyC) in the remaining three galaxies were derived. A strong narrow Ly-alpha emission line with two peaks separated by Vsep~298-592 km/s was observed in four galaxies with detected LyC emission and very weak Ly-alpha emission is observed in galaxies with LyC non-detections. Our new data confirm the tight anti-correlation between fesc(LyC) and Vsep found for previous low-redshift galaxy samples. Vsep remains the best indirect indicator of LyC leakage among all considered indicators. It is found that escaping LyC emission is detected predominantly in galaxies with Mg2>1.3. A tendency of an increase of fesc(LyC) with increasing of both the O3Mg2 and Mg2 is possibly present. However, there is substantial scatter in these relations not allowing their use for reliable prediction of fesc(LyC)., 19 pages, 11 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society. arXiv admin note: substantial text overlap with arXiv:2103.01514

The [CII] 158$~\mu$m emission line represents so far one of the most profitable tools for the investigation of the high-redshift galaxies in the early Universe. Being one of the brightest cooling lines in the rest-frame far-infrared regime of star-forming galaxies, it has been successfully exploited as a tracer of star-formation rate (SFR) in local sources. The picture is more complex at higher redshifts, where its usability in this context is still under investigation. Recent results from the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) survey suggest that there is no (or weak) evolution of the L$\mathrm{_{[CII]}}$-SFR relation up to $z\sim6$ but their reliability is hampered by the presence of a large population of [CII] non-detected galaxies. In this work, we characterize the population of [CII] non-detections in ALPINE. By stacking their ALMA spectra, we obtain a signal detected at $\sim5.1\sigma$, resulting in a [CII] luminosity of $\mathrm{log(L_\mathrm{[CII]}}/\mathrm{L_{\odot}})$ $\sim7.8$. When combining this value with those from the [CII] detections, we find a $\mathrm{L_{[CII]}}$-SFR relation with a slope $b=1.14\pm0.11$, in agreement within the uncertainties both with the linear relation found in the local Universe, and with the previous findings from ALPINE at $z\sim5$. This suggests that the [CII] line can be considered a good tracer of star formation up to the distant Universe. Finally, we show that the galaxies of our sample that most deviate from the observed L$_\mathrm{[CII]}$-SFR relation could suffer from a less precise redshift estimation, perhaps artificially reducing their [CII] luminosity. In this respect, we claim that there is no evidence in favour of a deficit of [CII] content in high-z galaxies, in contrast with earlier studies., Comment: Accepted for publication in A&A. 10 pages, 5 figures

We present Lyman continuum (LyC) radiation escape fraction $f_{\rm{esc}}$ measurements for 183 spectroscopically confirmed star-forming galaxies in the redshift range $3.11 < z < 3.53$ in the \textit{Chandra} Deep Field South. We use ground-based imaging to measure $f_{\rm{esc}}$, and use ground- and space-based photometry to derive galaxy physical properties using spectral energy distribution (SED) fitting. We additionally derive [O III]+H$\beta$ 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, $f_{\rm{esc}}$ in the range $0.14-0.85$. From non-detections, we place $1\sigma$ upper limits of $f_{\rm{esc}}300$A. For candidate LyC leakers, we find a weak negative correlation between $f_{\rm{esc}}$ and galaxy stellar masses, no correlation between $f_{\rm{esc}}$ specific star-formation rates (sSFRs) and a positive correlation between $f_{\rm{esc}}$ and EW$_0$([O III]+H$\beta$). The weak/no correlations between stellar mass and sSFRs may be explained by misaligned viewing angles and/or non-coincident timescales of starburst activity and periods of high $f_{\rm{esc}}$. Alternatively, escaping radiation may predominantly occur in highly localised star-forming regions, or $f_{\rm{esc}}$ measurements may be impacted by stochasticity of the intervening neutral medium, obscuring any global trends with galaxy properties. These hypotheses have important consequences for models of reionisation.

Finding reliable indicators of Lyman continuum (LyC) photon leakage from galaxies is essential in order to infer their escape fraction in the epoch of reionisation, where direct measurements of LyC flux are impossible. To this end, here we investigate whether strong C IV $\lambda \lambda 1548,1550$ emission in the rest-frame UV spectra of galaxies traces conditions ripe for ample production and escape of LyC photons. We compile a sample of 19 star-forming galaxies in the redshift range $z=3.1-4.6$ from the VANDELS survey that exhibit strong C IV emission, producing a stacked spectrum where all major rest-UV emission lines are clearly detected. Best-fitting spectral energy distribution models containing both stellar and nebular emission suggest the need for low stellar metallicities ($Z=0.1-0.2\,Z_\odot$), young stellar ages ($\log(\rm{age/yr}) = 6.1-6.5$), a high ionisation parameter ($\log U = -2$) and little to no dust attenuation ($E(B-V)=0.00-0.01$). However, these models are unable to fully reproduce the observed C IV and He II line strengths. We find that the Ly$\alpha$ line in the stacked spectrum is strong and peaks close to the systemic velocity, features that are indicative of significant LyC photon leakage along the line-of-sight. The covering fractions of low-ionisation interstellar absorption lines are also low implying LyC escape fraction in the range $\approx 0.05-0.30$, with signatures of outflowing gas. Finally, C IV/C III] ratios of >0.75 for a subset of individual galaxies with reliable detections of both lines are also consistent with physical conditions that enable significant LyC leakage. Overall, we report that multiple spectroscopic indicators of LyC leakage are present in the stacked spectrum of strong C IV emitting galaxies, potentially making C IV an important tracer of LyC photon escape at $z>6$., Comment: 15 pages, 10 figures, published in MNRAS

Utilizing spectroscopic observations taken for the VIMOS Ultra-Deep Survey (VUDS), new observations from Keck/DEIMOS, and publicly available observations of large samples of star-forming galaxies, we report here on the relationship between the star formation rate (SFR) and the local environment ($\delta_{gal}$) of galaxies in the early universe ($2, Comment: v2, 24 pages, nine figures, accepted to A&A after minor changes to language and formatting

To better understand the ionizing properties of galaxies in the EoR, we investigate deep, rest-frame ultraviolet (UV) spectra of $\simeq 500$ star-forming galaxies at $3 \leq z \leq 5$ selected from the public ESO-VANDELS spectroscopic survey. The absolute ionizing photon escape fraction ($f_{\rm esc}^{\rm abs}$) is derived by combining absorption line measurements with estimates of the UV attenuation. The ionizing production efficiency ($\xi_{ion}$) is calculated by fitting the far-UV (FUV) stellar continuum of the VANDELS galaxies. We find that the $f_{\rm esc}^{\rm abs}$ and $\xi_{ion}$ parameters increase towards low-mass, blue UV-continuum slopes and strong Ly$\alpha$ emitting galaxies, and both are just slightly higher-than-average for the UV-faintest galaxies in the sample. Potential Lyman Continuum Emitters (LCEs) and selected Lyman Alpha Emitters (LAEs) show systematically higher $\xi_{ion}$ ($\log \xi_{ion}$ (Hz\erg) $\approx 25.38, 25.41$) than non-LCEs and non-LAEs ($\log \xi_{ion}$ (Hz\erg) $\approx 25.18, 25.14$) at similar UV magnitudes. This indicates very young underlying stellar populations ($\approx 10~{\rm Myr}$) at relatively low metallicities ($\approx 0.2~{\rm Z_{\odot}}$). The FUV non-ionizing spectra of potential LCEs is characterized by very blue UV slopes ($\leq -2$), enhanced Ly$\alpha$ emission ($\leq -25$A), strong UV nebular lines (e.g., high CIV1550/CIII]1908 $\geq 0.75$ ratios), and weak absorption lines ($\leq 1$A). The latter suggests the existence of low gas-column-density channels in the interstellar medium which enables the escape of ionizing photons. By comparing our VANDELS results against other surveys in the literature, our findings imply that the ionizing budget in the EoR was likely dominated by UV-faint, low-mass and dustless galaxies., Comment: 25 pages, 18 figures, 2 tables; accepted for publication in MNRAS on April 24, 2023

We present $10$ main-sequence ALPINE galaxies (log($M/M_{\odot}$) = 9.2-11.1 and ${\rm SFR}=23-190\,{\rm M_{\odot}\,yr^{-1}}$) at $z\sim4.5$ with optical [OII] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multi-wavelength sample at these redshifts, combining various measurements in the ultra-violet, optical, and far-infrared including [CII]$_{158{\rm ��m}}$ line emission and dust continuum from ALMA and H$��$ emission from Spitzer photometry. For the first time, this unique sample allows us to analyze the relation between [OII] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [OII]/[CII] and [OII]/\halpha luminosity ratios at $z\sim4.5$. The [OII]$-$SFR relation at $z\sim4.5$ cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around $50\%$ solar. To explain the measured dust-corrected luminosity ratios of $L[OII]/L[CII] \sim 0.98^{+0.21}_{-0.22}$ and $L[OII]/LHa \sim -0.22^{+0.13}_{-0.15}$ for our sample, ionization parameters $\log(U)< -2$ and electron densities $\log(\rm n_e / {\rm [cm^{-3}]}) \sim 2.5-3$ are required. The former is consistent with galaxies at $z\sim2-3$, however lower than at $z>6$. The latter may be slightly higher than expected given the galaxies' specific SFR. The analysis of this pilot sample suggests that typical log($ M/M_{\odot})$ > 9 galaxies at $z\sim4.5$ to have broadly similar ISM properties as their descendants at $z\sim2$ and suggest a strong evolution of ISM properties since the Epoch of Reionization at $z>6$., 14 pages, 8 figures, Accepted for publication to MNRAS

Gaseous flows inside and outside galaxies are key to understanding galaxy evolution, as they regulate their star formation activity across cosmic time. We study the ISM kinematics of 330 CIII or HeII emitters, using far-UV ISM absorption lines detected in the VANDELS spectra. These galaxies span a broad range of stellar masses M$_\ast$ from $10^8$ to $10^{11}$ M$_\odot$, and SFRs from 1 to 500 M$_\odot$/yr, in the redshift range between 2 and 5. We find that the bulk ISM velocity v$_{ism}$ is globally in outflow, with v$_{ism}$ of -60 $\pm$ 10 km/s for low ionization gas traced by SiII 1260 Angstrom, CII 1334, SiII 1526, and AlII 1670, and v$_{ism}$ of -160 $\pm$ 30 and -170 $\pm$ 30 km/s for higher ionization gas traced respectively by AlIII 1854-1862 and SiIV 1393-1402. Interestingly, BPASS models are able to better reproduce the stellar continuum around the SiIV doublet than other stellar population templates. For individual galaxies, $34\%$ of the sample has a positive ISM velocity shift, almost double the fraction reported at lower redshifts. Comparing v$_{ism}$ to the host galaxies properties, we find no significant correlations with M$_\ast$ or SFR, and only a marginally significant dependence (at $\sim 2\sigma$) on morphology-related parameters, with slightly higher velocities in galaxies of smaller size (probed by the equivalent radius), higher concentration, and higher SFR surface density. The outflows are consistent with models of accelerating, momentum-driven winds, with densities decreasing towards the outskirts. Our moderately lower ISM velocities compared to those found in similar studies at lower redshifts suggest that inflows and internal turbulence might play an increased role at $z>2$. We estimate mass outflow rates comparable to the SFRs of the galaxies, and an average escape velocity of 625 km/s, suggesting that most of the ISM will remain bound to the galaxy halo., Comment: 24 pages, 2 tables and 20 figures, accepted for publication in A&A. This replaces the submitted version posted before. Fig. A.2 replaced, Fig. A.1 updated, typos corrected. Language editing by A&A has been performed

Deep images and near-IR spectra of galaxies in the field of the lensing cluster SMACS J0723.3−7327 were recently taken as part of the Early Release Observations (EROs) program of the James Webb Space Telescope (JWST). Among these, two NIRSpec spectra of galaxies, at z = 7.7 and at z = 8.5, were obtained, revealing, for the first time, the rest-frame optical emission line spectra of galaxies in the epoch of reionization, including the detection of the important [O III]λ4363 auroral line (see JWST PR 2022-035). We present an analysis of the emission line properties of these galaxies, finding that these galaxies have a high excitation (as indicated by high ratios of [O III]λ5007/[O II] λ3727, [Ne III] λ3869/[O II] λ3727), strong [O III]λ4363, high equivalent widths, and other properties typical of low-metallicity star-forming galaxies. Using the direct method, we determined oxygen abundances of 12 + log(O/H)≈7.9 in two z = 7.7 galaxies and a lower metallicity of 12 + log(O/H)≈7.4 − 7.5 (∼5% solar) in the z = 8.5 galaxy using different strong line methods. More accurate metallicity determinations will require better data. With stellar masses estimated from spectral energy distribution (SED) fits, we find that the three galaxies lie close to or below the z ∼ 2 mass-metallicity relation. Overall, these first galaxy spectra at z ∼ 8 show a strong resemblance in their the emission line properties of galaxies in the epoch of reionization with those of relatively rare local analogs previously studied with the SDSS. Clearly, the first JWST observations demonstrate already the incredible power of spectroscopy to reveal the properties of galaxies in the early Universe.

arXiv:2111.11453v1, Mid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured Universe of mid- and far-IR photometry at 34 and 70 µm and low-resolution spectroscopy at 17−36 µm using the state-of-the-art SpectroPhotometric Realisations of Infrared-selected Targets at all-z (SPRITZ) simulation. This investigation is also compared to the expected performance of the Origins Space Telescope and the Galaxy Evolution Probe. The photometric view of the Universe of a SPICA-like mission could cover not only bright objects (e.g. LIR > 1012 L) up to z = 10, but also normal galaxies (LIR < 1011 L) up to z ∼ 4. At the same time, the spectroscopic observations of such mission could also allow us to estimate the redshifts and study the physical properties for thousands of star-forming galaxies and active galactic nuclei by observing the polycyclic aromatic hydrocarbons and a large set of IR nebular emission lines. In this way, a cold, 2.5-m size space telescope with spectro-photometric capability analogous to SPICA, could provide us with a complete three-dimensional (i.e. images and integrated spectra) view of the dust-obscured Universe and the physics governing galaxy evolution up to z ∼ 4., We acknowledge the whole SPICA Collaboration Team. LB, CG, LS and JAFO acknowledge financial support by the Agenzia Spaziale Italiana (ASI) under the research contract 2018-31-HH.0. AF and FC acknowledges the support from grant PRIN MIUR2017-20173ML3WW_001. MPS acknowledges support from the Comunidad de Madrid through the Atracción de Talento Investigador Grant 2018-T1/TIC11035 and PID2019-105423GA-I00 (MCIU/AEI/FEDER,UE). FJC acknowledges financial support from the Spanish Ministry MCIU under project RTI2018-096686-B-C21 (MCIU/AEI/FEDER/UE), cofunded by FEDER funds and from the Agencia Estatal de Investigación, Unidad de Excelencia Maria de Maeztu, ref. MDM-2017-0765.

HLA-A*29 and HLA-B*51 are associated with birdshot uveitis and Behçet's disease, respectively, and are used as a diagnostic criterion in patients with suspected disease, requiring their detection in diagnostic laboratories. While commercial tests for individual HLA alleles are available for other disease-associated HLA variants, no similar allele-specific assays are available for HLA-A*29 and HLA-B*51. Here, we report sequence-specific priming-polymerase chain reaction (SSP-PCR) methods for the detection of HLA-A*29 and HLA-B*51 using a single PCR reaction per allele. The assays were tested in 30 and 32 previously HLA-typed samples, respectively, representing >97% of HLA-A alleles and >93% of HLA-B alleles in a European population. A concordance of 100% was observed with previous typing results, validating these methods for use in a diagnostic or research context.

Understanding the ionizing spectrum of low-metallicity galaxies is of great importance for modeling and interpreting emission line observations of early/distant galaxies. Although a wide suite of stellar evolution, atmosphere, population synthesis, and photoionization models, taking many physical processes into account now exist, all models face a common problem: the inability to explain the presence of nebular HeII emission, which is observed in many low metallicity galaxies, both in UV and optical spectra. Several possible explanations have been proposed in the literature, including Wolf-Rayet (WR) stars, binaries, very massive stars, X-ray sources, or shocks. However, none has so far been able to explain the major observations. We briefly discuss the HeII problem, available empirical data, and observed trends combining X-ray, optical and other studies. We present a simple and consistent physical model showing that X-ray binaries could explain the long-standing nebular HeII problem. Our model, described in Schaerer et al. (2019), successfully explains the observed trends and strength of nebular HeII emission in large samples of low metallicity galaxies and in individual galaxies, which have been studied in detail and with multi-wavelength observations. Our results have in particular important implications for the interpretation of galaxy spectra in the early Universe, which will be obtained with upcoming and future facilities., 5 pages, 2 figures. Proceedings of IAU Symposium No. 352, 2019 "Uncovering early galaxy evolution in the ALMA and JWST era". Eds. E. da Cunha, J. Hodge, J. Afonso, L. Pentericci

The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color-magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color-magnitude diagrams to identify stars more massive than 14 M ☉, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

We report the large effort which is producing comprehensive high-level young star cluster (YSC) catalogues for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry (from NUV to NIR), and derive their physical properties via spectral energy distribution fitting analyses. We use the nearby spiral galaxy NGC628 as a test case for demonstrating the impact that LEGUS will have on our understanding of the formation and evolution of YSCs and compact stellar associations within their host galaxy. Our analysis of the cluster luminosity function from the UV to the NIR finds a steepening at the bright end and at all wavelengths suggesting a dearth of luminous clusters. The cluster mass function of NGC628 is consistent with a power-law distribution of slopes $\sim -2$ and a truncation of a few times $10^5$ M$_\odot$. After their formation YSCs and compact associations follow different evolutionary paths. YSCs survive for a longer timeframe, confirming their being potentially bound systems. Associations disappear on time scales comparable to hierarchically organized star-forming regions, suggesting that they are expanding systems. We find mass-independent cluster disruption in the inner region of NGC628, while in the outer part of the galaxy there is little or no disruption. We observe faster disruption rates for low mass ($\leq$ $10^4$ M$_\odot$) clusters suggesting that a mass-dependent component is necessary to fully describe the YSC disruption process in NGC628., accepted for publication in ApJ; 27 pages; complete stellar cluster catalogues will be released in June 2017 at https://legus.stsci.edu

We study the Large Magellanic Cloud Papillon Nebula (N159-5), a conspicuous High Excitation Blob (HEB) lying in the star forming complex N159. Using JHK near-infrared photometry obtained at the ESO VLT with the ISAAC camera, we examine the stellar populations associated with the Papillon, tracing their history using stellar evolution models. Two populations are revealed: one composed of young, massive stars with an age ~ 3 Myr, and a second consisting of older lower mass stars of age spreading between 1 and 10 Gyr. We analyze the properties of those populations and discuss their significance in the context of N159. We also estimate that if the star at the center of the Papillon is single its initial mass is ~ 50 solar masses and it is affected by an extinction Av ~ 7 mag., Comment: Accepted in A&A 11 pages, 10 figures, 12 on-line material pages (= 1 table) Some figures have been replaced by jpeg versions to reduce the overall size

We present near infrared JHK imaging of the Small Magellanic Cloud compact H II region N81 using the ISAAC camera at the ESO Very Large Telescope (Antu). Our analysis of the stellar environment of this young massive star region reveals the presence of three new stellar populations in the surrounding field which are mainly composed of low mass stars. The main population is best fitted by evolutionary models for about 2 solar mass stars with an age of 1 Gyr. We argue that these populations are not physically associated with the H II region N81. Instead they are the result of a number of low mass star forming events through the depth of the SMC south of its Shapley's wing. The populations can rather easily be probed due to the low interstellar extinction in that direction., Comment: 11 pages, 5 figures, accepted for publication in A&A

We investigate the evolution of galaxy clustering for galaxies in the redshift range 2.0, Comment: 19 pages, 10 figures, submitted to A&A

We measured the sizes and morphological parameters of LARS galaxies in the continuum, Lya, and Ha 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. 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, Comment: Accepted date: Dec 19th, 2014. arXiv admin note: text overlap with arXiv:astro-ph/0311352

We rediscuss the temperature of O dwarfs based on new non-LTE line blanketed atmosphere models including stellar winds computed with the CMFGEN code of Hillier & Miller (1998). Compared to the latest calibration of Vacca et al. (1996), the inclusion of line blanketing leads to lower effective temperatures, typically by 4000 to 1500 K for O3 to O9.5 dwarf stars. The dependence of the Teff-scale on stellar and model parameters - such as mass loss, microturbulence, and metallicity - is explored, and model predictions are compared to optical observations of O stars. Even for an SMC metallicity we find a non-negligible effect of line blanketing on the Teff-scale. The temperature reduction implies downward revisions of luminosities by 0.1 dex and Lyman continuum fluxes Q0 by approximately 40% for dwarfs of a given spectral type., 6 pages, 4 figures. To be published in A&A

Using Hubble Space Telescope observations with STIS, we study the main exciting stars of N81, a high excitation compact Hii region in the Small Magellanic Cloud (SMC). These far UV observations are the first spectroscopic measurements of stars in such a region and reveal features characteristic of an O6-O8 stellar type. The astonishing weakness of their wind profiles and their sub-luminosity (up to ~ 2 mag fainter in Mv than the corresponding dwarfs) make these stars a unique stellar population in the Magellanic Clouds. Our analysis suggests that they are probably in the Hertzsprung-Russell diagram locus of a particularly young class of massive stars, the so-called Vz luminosity class, as they are arriving on the zero age main sequence., Comment: 9 pages, 3 figures

We review the properties of stellar populations and the interstellar medium (ISM) of various kinds of massive star forming regions (ranging from stellar clusters, Hii regions, super star clusters, etc. to distant starburst galaxies). The nature of their multi-wavelength spectra as well as the techniques used for their interpretation is are discussed. These objects play an important role in our understanding of star formation, interactions between stars and the ISM, and galaxy evolution among others.

In the course of our 870um APEX/LABOCA follow up of the Herschel Lensing Survey we have detected a source in AS1063 (RXC J2248.7-4431), that has no counterparts in any of the Herschel PACS/SPIRE bands, it is a Herschel 'drop-out' with S_870/S_500>0.5. The 870um emission is extended and centered on the brightest cluster galaxy suggesting either a multiply imaged background source or substructure in the Sunyaev-Zel'dovich (SZ) increment due to inhomogeneities in the hot cluster gas of this merging cluster. We discuss both interpretations with emphasis on the putative lensed source. Based on the observed properties and on our lens model we find that this source could be the first SMG with a moderate far infrared luminosity (L_FIR4. In deep HST observations we identified a multiply imaged z~6 source and we measured its spectroscopic redshift z=6.107 with VLT/FORS. This source could be associated with the putative SMG but it is most likely offset spatially by 10-30kpc and they could be interacting galaxies. With a FIR luminosity in the range [5-15]x10^{11} L_sol corresponding to a star formation rate in the range [80-260]M_sol/yr, this SMG would be more representative than the extreme starbursts usually detected at z>4. With a total magnification of ~25 it would open a unique window to the 'normal' dusty galaxies at the end of the epoch of reionization., accepted for publication in A&A

We present a first step towards complete stellar models for massive stars that treat the entire star including its wind. Our models are based on state-of-the art non-LTE atmospheric and interior modelling. The models yield the stellar evolution under the constraint of realistic atmospheres as well as line-blanketed continuum fluxes and H and He line profiles. We follow the evolution from OB to LBV, Ofpe/WN, and WR stars. We investigate the effect of line-blanketing during MS evolution. We adress the effect of an the extended atmosphere on the evolution and discuss the first results for WR stars.

We present a characterization of the close environment of GRB980425 based on 5-160mic spectro-imaging obtained with Spitzer. The Gamma-Ray Burst GRB980425 occurred in a nearby (z=0.0085) SBc-type dwarf galaxy, at a projected distance of 900pc from an HII region with strong signatures of Wolf-Rayet (WR) stars. While this "WR region" produces less than 5% of the B-band emission of the host, we find that it is responsible for 45+/-10% of the total infrared luminosity, with a maximum contribution reaching 75% at 25-30mic. This atypical property is rarely observed among morphologically-relaxed dwarves, suggesting a strong causal link with the GRB event. The luminosity of the WR region (L_8-1000mic=4.6x10^8 Lsol), the peak of its spectral energy distribution at, Comment: ApJ in press, 14 pages, 2 tables, 7 figures

In a paper submitted to A&A we present the first line blanketed hydrodynamic models of spherically expanding atmospheres of hot stars. This paper is complementary to the submitted paper. Here, we emphasize the advantages and the weak points of our approach and we present additional technical aspects.

Accurate physical parameters of newborn massive stars are essential ingredients to shed light on their formation, which is still an unsolved problem. The rare class of compact H II regions in the Magellanic Clouds (MCs), termed ``high-excitation blobs'' (HEBs), presents a unique opportunity to acquire this information. These objects (~ 4" to 10", ~ 1 to 3 pc, in diameter) harbor the youngest massive stars of the OB association/molecular cloud complexes in the MCs accessible through high-resolution near-IR and optical techniques. We present a brief overview of the results obtained with HST mainly on two HEBs, one in the LMC (N159-5) and the other in the SMC (N81)., 5 pages, to appear in the Proceedings of the 41st ESLAB Symposium "The Impact of HST on European Astronomy", 29 May to 1 June 2007, ESTEC, Noordwijk, Netherlands; eds. Guido De Marchi and Duccio Macchetto

We present a quantitative study of the stellar and wind properties of massive stars in the compact star forming region SMC-N81. Non-LTE spherically extended atmosphere models including line-blanketing have been computed with the code CMFGEN (Hillier & Miller 1998) and the analysis of UV STIS spectra lead to the following results: 1) The SMC-N81 components are young (~ 0-4 Myrs) O stars with Teff compatible with medium to late subtypes and with luminosities lower than average Galactic O dwarfs, rendering them possible ZAMS candidates; 2) The winds are extremely weak: the mass loss rates (~1e-8/1e-9 Msol/yr) and the modified wind momenta are 1 to 2 orders of magnitude lower than observed so far for Galactic stars, and are lower than the predictions of the most recent hydrodynamical models. The reasons for such weak winds are investigated with special emphasis on the modified wind momenta: 1) There may be a break-down of the wind momentum - luminosity relation (WLR) for dwarf stars at low luminosity (log L/Lsol < 5.5). However, reasons for such a breakdown remain unknown; 2) The slope of the WLR may be steeper at low metallicity. This is predicted by the radiation driven wind theory, but the current hydrodynamical simulations do not show any change of the slope at SMC metallicity. Moreover, there are indications that some Galactic objects have wind momenta similar to those of the SMC stars; 3) Decoupling in the atmosphere may lead to multicomponent winds, but various tests indicate that this is not likely to be the case for the SMC-N81 stars. Hence, the origin of the weakness of the wind observed in these objects remains unknown. We suggest that this weakness may be linked with the youth of these stars and represents possibly the onset of stellar winds in recently formed massive stars., 23 pages, 22 figures, A&A accepted

We present the N-band (8-13 micron) spectrum of the hidden compact radio super-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6m telescope. The spectrum is characterised by a rising continuum due to warm dust, a silicate absorption and a strong [SIV] line at 10.5 micron. Weaker lines of [ArIII] at 9.0 micron and [NeII] at 12.8 micron are also present. The continuum can be modeled by an optically thick emission from hot dust emission extinguished by a cold foreground dust screen and a silicate absorption feature with A_sil = 0.73+/-0.05 mag. We show how the spatial scale of the observations greatly determine the mid-IR appearance of NGC 5253 and the important implications that this has on the interpretation of line fluxes in terms of the properties (age, IMF, etc.) of the embedded cluster. We have modeled the observed line fluxes towards C2 using photoionisation models with the most recent spectral energy distributions available to describe the integrated properties of the stellar cluster. Strong constraints on the geometry based on high spatial resolution observations at different wavelengths -- near-IR (HST and Keck), mid-IR (TIMMI2) and radio (VLA) -- allows us to restrain the ionisation parameters to values logU >= -0.5 dex. This constraint on U lead to two possible solutions for the age and upper mass cutoff of C2: 1) a young (< 4 Myr) cluster with a "non-standard" IMF with a low upper mass cutoff Mup < 50 Msun, and 2) a cluster of ~5-6 Myr with a standard high upper mass cutoff (Mup \~ 100 Msun). Arguments in favour and against these two scenarios are presented. The origin of the [OIV] 25.9 micron emission measured by ISO and the possible presence of an intermediate mass black hole inside C2 are also addressed., 19 pages, 5 tables and 5 figures. Accepted for publication in A&A

Numerous agents of endogenous and exogenous origin damage DNA in our genome. There are several DNA-repair pathways that recognize lesions in DNA and remove them through a number of diverse reaction sequences. Defects in DNA-repair proteins are associated with several human hereditary syndromes, which show a marked predisposition to cancer. Although DNA repair is essential for a healthy cell, DNA-repair enzymes counteract the efficiency of a number of important antitumor agents that exert their cytotoxic effects by damaging DNA. DNA-repair enzymes are therefore also targets for drug design. DNA-repair processes differ greatly in their nature and complexity. Whereas some pathways only require a single enzyme to restore the original DNA sequence, others operate through the coordinated action of 30 or more proteins. Our understanding of the genetic, biochemical, and structural basis of DNA repair and related processes has increased dramatically over the past decade. This review summarizes the latest developments in this field.

Aims. The aim of this work is to constrain the evolution of the fraction of Lya emitters among UV selected star forming galaxies at 2 25A to increase from 5% at z=2 to 30% at z=6, with the increase being relatively stronger beyond z=4. We observe no difference, for the narrow range of UV luminosities explored in this work, between the fraction of strong Lya emitters among galaxies fainter or brighter than M*, although the fraction for the FUV faint galaxies evolves faster, at 2, Comment: 12 pages, 6 figures, A&A in press

The results of deep long-slit spectroscopy of the extremely low-metallicity blue compact dwarf (BCD) galaxy SBS 0335-052 are presented. Down to intensity levels of 10^{-3 ... -4} of Hbeta, unprecedented for spectroscopy of extra-galactic giant H II regions, we detect numerous weak permitted and forbidden nebular lines in the brightest part of the galaxy. With varying degrees of confidence, the detections include lines of high-ionization ions like Fe^{4+} -Fe^{6+}, implying very hard ionizing radiation. Two broad emission features, possibly from Wolf-Rayet stars, and stellar He II 4200 absorption are seen in the same region. The large spatial extent of He II 4686 emission (implying the presence of sufficient ionizing photons with energies above 54 eV) and the spatial distribution of the electron temperature suggest that at least some part of the hard radiation is associated with shocks. Extended Halpha emission is detected over ~ 6 - 8 kpc, a much larger area than in previous studies, suggesting that hot ionized gas is spread out far away from the central ionizing clusters. This shows that nebular line and continuous emission can significantly modify the colours of these extended regions and must be taken into account in studies of the underlying stellar population., Comment: 5 pages, 3 Postscript figures, accepted for publication in the Astronomy and Astrophysics

High resolution imaging with the HST uncovers the so far hidden stellar content and the nebular features of the high excitation compact HII region N83B in the Large Magellanic Cloud (LMC). We discover that the HII region is powered by the most recent massive starburst in the OB association LH5 and the burst has created about 20 blue stars spread over ~30" on the sky (7.5 pc). Globally N83B displays a turbulent environment typical of newborn massive star formation sites. It contains an impressive ridge, likely created by a shock and a cavity with an estimated age of only ~30,000 yr, sculpted in the ionized gas by the powerful winds of massive stars. The observations bring to light two compact HII blobs, N83B-1 and N83B-2, and a small arc-nebula, N83B-3, lying inside the larger HII region. N83B-1, only ~2.8" (0.7 pc) across, is the brightest and most excited part of N83B. It harbors the presumably hottest star of the burst and is also strongly affected by dust with an extinction of Av=2.5 mag. The second blob, N83B-2, is even more compact, with a size of only ~1" (0.3 pc). All three features are formed in the border zone between the molecular cloud and the ionized gas possibly in a sequential process triggered by the ionization front of an older HII region. Our HST imaging presents an interesting and rare opportunity to observe details in the morphology of the star formation in very small spatial scales in the LMC which are in agreement with the concept of the fractal structure of molecular star forming clouds. A scenario which supports hierarchical massive star formation in the LMC OB association LH5 is presented., Comment: 13 pages, 7 figures. A version of the paper with higher quality images is available at http://wwwusr.obspm.fr/~heydari/projects/N83

We present a Wolf-Rayet wind model including clumping, which is assumed to be due to full-scale supersonic compressible turbulence as suggested by Moffat & Robert (1994). It is shown that clumping leads to a larger transfer of radiative to mechanical luminosity, which corresponds to a momentum ratio of (Ṁv ∞)/(L/c) = 12 for a typical WN5 star. We also show how clumping reduces the effects of line blanketing in spectral analyses.

We observed the ring galaxy NGC 7552 with the mid-infrared (MIR) instrument VISIR at an angular resolution of 0.3"- 0.4" and with the near-infrared (NIR) integral-field spectrograph SINFONI on the VLT, and complement these observations with data from ISO and Spitzer. The starburst ring is clearly detected at MIR wavelengths at the location of the dust-extincted, dark ring seen in HST observations. This "ring", however, is a rather complex annular region of more than 100 parsec width. We find a large fraction of diffuse [Ne II] and PAH emission in the central region that is not associated with the MIR peaks on spatial scales of \sim30 pc. We do not detect MIR emission from the nucleus of NGC 7552, which is very prominent at optical and NIR continuum wavelengths. However, we have identified nine unresolved MIR peaks within the ring. The average extinction of these peaks is A(V)=7.4 and their total infrared luminosity is L(IR) = 2.1*10^10 Lo. The properties of these peaks are typical for MIR-selected massive clusters found in other galaxies. The ages of the MIR-selected clusters are in the range of 5.9\pm0.3 Myr. The age spread among the clusters of 0.8 Myr is small compared to the travel time of \sim5.6 Myr for half an orbit within the starburst ring. We find no strong evidence for a scenario where the continuous inflow of gas leads to the ongoing formation of massive clusters at the contact points between galactic bar and starburst ring. Instead, it appears more likely that the gas density build up more gradually over larger ring segments, and that the local physical conditions govern cluster formation. We note that the fundamental limitation on the accurate derivation of cluster age, mass and IMF slope is the lack of higher angular resolution., 16 pages, 10 figures, accepted, to appear in A&A