Context. Stellar feedback strongly affects the interstellar medium (ISM) of galaxies. Stellar feedback in the first galaxies likely plays a major role in enabling the escape of LyC photons, which ...contribute to the re-ionization of the Universe. Nearby starburst galaxies serve as local analogues allowing for a spatially resolved assessment of the feedback processes in these galaxies. Aims.We aim to characterize the feedback effects from the star clusters in the local high-redshift analogue ESO 338-IG04 on the ISM and compare the results with the properties of the most massive clusters. Methods. We used high quality VLT/MUSE optical integral field data to derive the physical properties of the ISM such as ionization, density, shocks, and performed new fitting of the spectral energy distributions of the brightest clusters in ESO 338-IG04 from HST imaging. Results.We find that ESO 338-IG04 has a large ionized halo which we detect to a distance of 9 kpc. We identify four Wolf-Rayet (WR) clusters based on the blue and red WR bump. We follow previously identified ionization cones and find that the ionization of the halo increases with distance. Analysis of the galaxy kinematics shows two complex outflows driven by the numerous young clusters in the galaxy. We find a ring of shocked emission traced by an enhanced O I/Hα ratio surrounding the starburst and at the end of the outflow. Finally we detect nitrogen enriched gas associated with the outflow, likely caused by the WR stars in the massive star clusters. Conclusions. Photoionization dominates the central starburst and sets the ionization structure of the entire halo, resulting in a density bounded halo, facilitating the escape of LyC photons. Outside the central starburst, shocks triggered by an expanding super bubble become important. The shocks at the end of the outflow suggest interaction between the hot outflowing material and the more quiescent halo gas.
ABSTRACT
We have used the capability of the Multi-Unit Spectroscopic Explorer (MUSE) instrument to explore the impact of stellar feedback at large scales in Haro 11, a galaxy under extreme starburst ...condition and one of the first galaxies where Lyman continuum (LyC) has been detected. Using H α, O iii λ5007, and O i λ6300 emission lines from deep MUSE observations, we have constructed a sequence of velocity-dependent maps of the H α emission, the state of the ionized gas, and a tracer of fast shocks. These allowed us to investigate the ionization structure of the galaxy in 50 km s−1 bins over a velocity range of −400 to 350 km s−1. The ionized gas in Haro 11 is assembled by a rich arrangement of structures, such as superbubbles, filaments, arcs, and galactic ionized channels, whose appearances change drastically with velocity. The central star-forming knots and the star-forming dusty arm are the main engines that power the strong mechanical feedback in this galaxy, although with different impact on the ionization structure. Haro 11 appears to leak LyC radiation in many directions. We found evidence of a kpc-scale fragmented superbubble that may have cleared galactic-scale channels in the ISM. Additionally, the Southwestern hemisphere is highly ionized in all velocities, hinting at a density bound scenario. A compact kpc-scale structure of lowly ionized gas coincides with the diffuse Lyα emission and the presence of fast shocks. Finally, we find evidence that a significant fraction of the ionized gas mass may escape the gravitational potential of the galaxy.
Local metal-poor galaxies stand as ideal laboratories for probing the properties of the interstellar medium (ISM) in chemically unevolved conditions. Detailed studies of this primitive ISM can help ...gain insights into the physics of the first primordial galaxies that may be responsible for the reionization. Quantifying the ISM porosity to ionizing photons in nearby galaxies may improve our understanding of the mechanisms leading to Lyman continuum photon leakage from galaxies. The wealth of infrared (IR) tracers available in local galaxies and arising from different ISM phases allows us to constrain complex models in order to estimate physical quantities.
ABSTRACT
Star formation is a clustered process that regulates the structure and evolution of galaxies. We investigate this process in the dwarf galaxy Haro 11, forming stars in three knots (A, B, and ...C). The exquisite resolution of HST imaging allows us to resolve the starburst into tens of bright star clusters. We derive masses between 105 and $10^7\, \rm M_{\odot }$ and ages younger than 20 Myr, using photometric modelling. We observe that the clustered star formation has propagated from knot C (the oldest) through knot A (in between) towards knot B (the youngest). We use aperture-matched ultraviolet and optical spectroscopy (HST + MUSE) to independently study the stellar populations of Haro 11 and determine the physical properties of the stellar populations and their feedback in 1-kpc diameter regions. We discuss these results in light of the properties of the ionized gas within the knots. We interpret the broad blue-shifted components of the optical emission lines as outflowing gas (vmax ∼ 400 km/s). The strongest outflow is detected in knot A with a mass rate of $\dot{M}_{\mathrm{ out}}\sim 10\, \rm M_{\odot }/yr$, 10 times higher than the star formation in the same region. Knot B hosts a young and not fully developed outflow, whereas knot C has likely been already evacuated. Because Haro 11 has properties similar to high-redshift unresolved galaxies, our work can additionally aid the understanding of star formation at high redshift, a window that will be opened by upcoming facilities.
We report on the discovery of ionised gas filaments in the circum-galactic halo of the extremely metal-poor compact starburst SBS 0335-052E in a 1.5 h integration with the MUSE integral-field ...spectrograph. We detect these features in Hα and O iii emission down to a limiting surface-brightness of 5 × 10-19 erg s-1 cm-2 arcsec-2. The filaments have projected diameters of 2.1 kpc and extend more than 9 kpc to the north and north-west from the main stellar body. We also detect extended nebular He ii λ4686 emission that brightens towards the north-west at the rim of a starburst driven super-shell. We also present a velocity field of the ionised gas. The filaments appear to connect seamlessly in velocity space to the kinematical disturbances caused by the shell. Similar to high-z star-forming galaxies, the ionised gas in this galaxy is dispersion dominated. We argue that the filaments were created via feedback from the starburst and that these ionised structures in the halo may act as escape channels for Lyman continuum radiation in this gas-rich system.
ABSTRACT
We use high quality VLT/MUSE data to study the kinematics and the ionized gas properties of Haro 11, a well-known starburst merger system and the closest confirmed Lyman continuum leaking ...galaxy. We present results from integrated line maps, and from maps in three velocity bins comprising the blueshifted, systemic, and redshifted emission. The kinematic analysis reveals complex velocities resulting from the interplay of virial motions and momentum feedback. Star formation happens intensively in three compact knots (knots A, B, and C), but one, knot C, dominates the energy released in supernovae. The halo is characterized by low gas density and extinction, but with large temperature variations, coincident with fast shock regions. Moreover, we find large temperature discrepancies in knot C, when using different temperature-sensitive lines. The relative impact of the knots in the metal enrichment differs. While knot B is strongly enriching its closest surrounding, knot C is likely the main distributor of metals in the halo. In knot A, part of the metal enriched gas seems to escape through low density channels towards the south. We compare the metallicities from two methods and find large discrepancies in knot C, a shocked area, and the highly ionized zones, that we partially attribute to the effect of shocks. This work shows, that traditional relations developed from averaged measurements or simplified methods, fail to probe the diverse conditions of the gas in extreme environments. We need robust relations that include realistic models where several physical processes are simultaneously at work.
Aims/hypothesis
We examined the effects of serum insulin levels on vagal control over the heart and tested the hypothesis that higher fasting insulin levels are associated with lower vagal control. ...We also examined whether experimentally induced increases in insulin by beta cell secretagogues, including glucagon-like peptide-1 (GLP-1), will decrease vagal control.
Methods
Respiration and ECGs were recorded for 130 healthy participants undergoing clamps. Three variables of cardiac vagal effects (the root mean square of successive differences rMSSD in the interbeat interval of the heart rate IBI, heart-rate variability HRV caused by peak-valley respiratory sinus arrhythmia pvRSA, and high-frequency power HF) and heart rate (HR) were obtained at seven time points during the clamps, characterised by increasing levels of insulin (achieved by administering insulin plus glucose, glucose only, glucose and GLP-1, and glucose and GLP-1 combined with arginine).
Results
Serum insulin level was positively associated with HR at all time points during the clamps except the first-phase hyperglycaemic clamp. Insulin levels were negatively correlated with variables of vagal control, reaching significance for rMSSD and log
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HF, but not for pvRSA, during the last four phases of the hyperglycaemic clamp (hyperglycaemic second phase, GLP-1 first and second phases, and arginine). These associations disappeared when adjusted for age, BMI and insulin sensitivity. Administration of the beta cell secretagogues GLP-1 and arginine led to a significant increase in HR, but this was not paired with a significant reduction in HRV measures.
Conclusion/interpretation
Experimentally induced hyperinsulinaemia is not correlated with cardiac vagal control or HR when adjusting for age, BMI and insulin sensitivity index. Our findings suggest that exposure to a GLP-1 during hyperglycaemia leads to a small acute increase in HR but not to an acute decrease in cardiac vagal control.
Context. The Lyα line is an important diagnostic for star formation at high redshift, but interpreting its flux and line profile is difficult because of the resonance nature of Lyα. Trends between ...the escape of Lyα photons and dust and properties of the interstellar medium (ISM) have been found, but detailed comparisons between Lyα emission and the properties of the gas in local high-redshift analogs are vital for understanding the relation between Lyα emission and galaxy properties. Aims. For the first time, we can directly infer the properties of the ionized gas at the same location and similar spatial scales of the extended Lyα halo around the local Lyα emitter and Lyman-break galaxy analog ESO 338-IG04. Methods. We obtained VLT/MUSE integral field spectra. We used ionization parameter mapping of the S ii/O iii line ratio and the kinematics of Hα to study the ionization state and kinematics of the ISM of ESO 338-IG04. Results. The velocity map reveals two outflows, one toward the north, the other toward the south of ESO 338. The ionization parameter mapping shows that the entire central area of the galaxy is highly ionized by photons leaking from the H ii regions around the youngest star clusters. Three highly ionized cones have been identified, of which one is associated with an outflow detected in the Hα. We propose a scenario where the outflows are created by mechanical feedback of the older clusters, while the highly ionized gas is caused by the hard ionizing photons emitted by the youngest clusters. A comparison with the Lyα map shows that the (approximately bipolar) asymmetries observed in the Lyα emission are consistent with the base of the outflows detected in Hα. No clear correlation with the ionization cones is found. Conclusions. The mechanical and ionization feedback of star clusters significantly changes the state of the ISM by creating ionized cones and outflows. The comparison with Lyα suggests that especially the outflows could facilitate the escape of Lyα photons.
Context. The interplay between the formation of stars, stellar feedback and cloud properties strongly influences the star formation history of giant molecular clouds. The formation of massive stars ...leads to a variety of stellar clusters, ranging from low stellar density OB associations to dense, gravitationally bound starburst clusters. Aims. We aimed at identifying the massive stellar content and reconstructing the star formation history of the W51 giant molecular cloud. Methods. We performed near-infrared imaging and K-band spectroscopy of the massive stars in W51. We analysed the stellar populations using colour-magnitude and colour-colour diagrams and compared the properties of the spectroscopically identified stars with stellar evolution models. Results. We derive the ages of the different sub-clusters in W51 and, based on our spectroscopy derive an age for W51 of 3 Myr or less. The age of the P Cygni star LS1 and the presence of two still forming proto-clusters suggests that the star formation history of W51 is more complex than a single burst. Conclusions. We did not find evidence for triggered star formation and we concluded that the star formation in W51 is multi seeded. We finally concluded that W51 is an OB association where different sub-clusters form over a time span of at least 3–5 Myr.
Aims. The formation of massive stars remains poorly understood and little is known about their birth multiplicity properties. Here, we aim to quantitatively investigate the strikingly low ...radial-velocity dispersion measured for a sample of 11 massive pre- and near-main-sequence stars (sigma sub(1D)= 5.6 + or - 0.2 kms super(-1)) in the very young massive star forming region M17, in order to obtain first constraints on the multiplicity properties of young massive stellar objects. Methods. We compute the radial-velocity dispersion of synthetic populations of massive stars for various multiplicity properties and we compare the obtained sigma sub(1D) distributions to the observed value. We specifically investigate two scenarios: a low binary fraction and a dearth of short-period binary systems. Results. Simulated populations with low binary fractions (f sub(bin)= 0.12 sub(-0.09) super(+0.16)) or with truncated period distributions (P sub(cutoff)> 9 months) are able to reproduce the low sigma sub(1D) observed within their 68%-confidence intervals. Furthermore, parent populations with f sub(bin)> 0.42 or P sub(cutoff)< 47 d can be rejected at the 5%-significance level. Both constraints are in stark contrast with the high binary fraction and plethora of short-period systems in few Myr-old, well characterized OB-type populations. To explain the difference in the context of the first scenario would require a variation of the outcome of the massive star formation process. In the context of the second scenario, compact binaries must form later on, and the cut-off period may be related to physical length-scales representative of the bloated pre-main-sequence stellar radii or of their accretion disks. Conclusions. If the obtained constraints for the M17's massive-star population are representative of the multiplicity properties of massive young stellar objects, our results may provide support to a massive star formation process in which binaries are initially formed at larger separations, then harden or migrate to produce the typical (untruncated) power-law period distribution observed in few Myr-old OB binaries.
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