We make use of \textit{JWST} medium and broad-band NIRCam imaging, along with
ultra-deep MIRI $5.6 \rm \mu m$ imaging, in the Hubble eXtreme Deep Field (XDF)
to identify prominent line emitters at ...$z\simeq 7-8$. Out of a total of 58
galaxies at $z\simeq 7-8$, we find 18 robust candidates ($\simeq$31\%) for
(H$\beta$ + OIII) emitters, based on their enhanced fluxes in the F430M and
F444W filters, with EW$_{0}$(H$\beta$ +OIII) $\simeq 87 - 2100$ {\AA}. Among
these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux
excess at $5.6 \, \rm \mu m$, indicating the simultaneous presence of a
prominent H$\alpha$ emission line with EW$_{0}$(H$\alpha$) $\simeq 200-3000$
{\AA}. This is the first time that H$\alpha$ emission can be detected in
individual galaxies at $z>7$. The H$\alpha$ line, when present, allows us to
separate the contributions of H$\beta$ and OIII to the (H$\beta$ +OIII)
complex, and derive H$\alpha$-based star formation rates (SFRs). We find that
in most cases OIII/H$\beta > 1$. Instead, two galaxies have OIII/H$\beta <
1$, indicating that the NIRCam flux excess is mainly driven by H$\beta$. This
could potentially imply extremely low metallicities. Most prominent line
emitters are very young starbursts or galaxies on their way to/from the
starburst cloud. They make for a cosmic SFR density $\rm
log_{10}(\rho_{SFR_{H\alpha}}) \simeq -2.35$, which is about a quarter of the
total value ($\rm log_{10}(\rho_{SFR_{tot}}) \simeq -1.76$) at $z\simeq 7-8$.
Therefore, the strong H$\alpha$ emitters likely had a significant role in
reionization.
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 characterised 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.
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. We 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. We use high quality VLT/MUSE optical integral field data to derive the physical properties of the ISM such as ionization, density, shocks, and perform new fitting of the spectral energy distributions of the brightest clusters in ESO 338-IG04 from HST imaging. ESO 338-IG04 has a large ionized halo which we detect to a distance of 9 kpc. We identify 4 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 OI/H\(\alpha\) 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. Photo-ionization 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.
We have used the capability of the 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 Ha, OIII and OI emission lines from deep MUSE observations, we have constructed a sequence of velocity-dependent maps of the Ha emission, the state of the ionised gas and a tracer of fast shocks. These allowed us to investigate the ionisation structure of the galaxy in 50 kms^2 bins over a velocity range of -400 to 350 kms. The ionised gas in Haro 11 is assembled by a rich arrangement of structures, such as superbubbles, filaments, arcs and galactic ionised 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 ionisation 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 ionised in all velocities, hinting at a density bound scenario. A compact kpc-scale structure of lowly ionised gas coincides with the diffuse Lya emission and the presence of fast shocks. Finally, we find evidence that a significant fraction of the ionised gas mass may escape the gravitational potential of the galaxy.
We present the Hubble imaging Probe of Extreme Environments and Clusters (HiPEEC) survey. We fit HST NUV to NIR broadband and H\(\alpha\) fluxes, to derive star cluster ages, masses, extinctions and ...determine the star formation rate (SFR) of 6 merging galaxies. These systems are excellent laboratories to trace cluster formation under extreme gas physical conditions, rare in the local universe, but typical for star-forming galaxies at cosmic noon. We detect clusters with ages of 1-500 Myr and masses that exceed \(10^7\) M\(_\odot\). The recent cluster formation history and their distribution within the host galaxies suggest that systems like NGC34, NGC1614, NGC4194 are close to their final coalescing phase, while NGC3256, NGC3690, NGC6052 are at an earlier/intermediate stage. A Bayesian analysis of the cluster mass function in the age interval 1-100 Myr provides strong evidence in 4 of the 6 galaxies that an exponentially truncated power law better describes the observed mass distributions. For two galaxies, the fits are inconclusive due to low number statistics. We determine power-law slopes \(\beta \sim-1.5\) to \(-2.0\), and truncation masses, M\(_c\), between \(10^6\) and a few times \(10^7\) M\(_\odot\), among the highest values reported in the literature. Advanced mergers have higher M\(_c\) than early/intermediate merger stage galaxies, suggesting rapid changes in the dense gas conditions during the merger. We compare the total stellar mass in clusters to the SFR of the galaxy, finding that these systems are among the most efficient environments to form star clusters in the local universe.
The leakage of Lyman continuum photons from star forming galaxies is an elusive parameter. When observed, it provides a wealth of information on star formation in galaxies and the geometry of the ...interstellar medium, and puts constraints on the role of star forming galaxies in the reionization of the universe. H-alpha-selected galaxies at z~2 trace the highest star formation population at the peak of cosmic star formation history, providing a base for directly measuring Lyman continuum escape. Here we present this method, and highlight its benefits as well as caveats. We also use the method on 10 H-alpha emitters in the Chandra Deep Field South at z=2.2, also imaged with the Hubble Space Telescope in the ultraviolet. We find no individual Lyman continuum detections, and our stack puts a 5 sigma upper limit on the average absolute escape fraction of <24%, consistent with similar studies. With future planned observations, the sample sizes would rapidly increase and the method presented here would provide very robust constraints on the escape fraction.
The Ly\(\alpha\) emission line is one of the main observables of galaxies at high redshift, but its output depends strongly on the neutral gas distribution and kinematics around the star-forming ...regions where UV photons are produced. We present observations of Ly\(\alpha\) and 21-cm HI emission at comparable scales with the goal to qualitatively investigate how the neutral interstellar medium (ISM) properties impact Ly\(\alpha\) transfer in galaxies. We have observed 21-cm HI at the highest angular resolution possible (~ 3" beam) with the VLA in two local galaxies from the Lyman Alpha Reference Sample. We contrast this data with HST Ly\(\alpha\) imaging and spectroscopy, and MUSE and PMAS ionized gas observations. In LARS08, high intensity Ly\(\alpha\) emission is co-spatial with high column density HI where dust content is the lowest. The Ly\(\alpha\) line is strongly redshifted, consistent with velocity redistribution which allows Ly\(\alpha\) escape from high column density neutral medium with low dust content. In eLARS01, high intensity Ly\(\alpha\) emission is located in regions of low column density HI, below the HI data sensitivity limit (\(<2\times10^{20}\,\)cm\(^{-2}\)). The perturbed ISM distribution with low column density gas in front of the Ly\(\alpha\) emission region plays an important role in the escape. In both galaxies, the faint Ly\(\alpha\) emission (\(\sim 1\times10^{-16}\)erg.s\(^{-1}\)cm\(^{-2}\)arcsec\(^{-2}\)) traces intermediate H\(\alpha\) emission regions where HI is found, regardless of the dust content. Dust seems to modulate, but not prevent, the formation of a faint Ly\(\alpha\) halo. This study suggests the existence of scaling relations between dust, H\(\alpha\), HI, and Ly\(\alpha\) emission in galaxies.
Thanks to decades of observations using HST, the structure of galaxies at redshift \(z>2\) has been widely studied in the rest-frame ultraviolet regime, which traces recent star formation from young ...stellar populations. But, we still have little information about the spatial distribution of the older, more evolved, stellar populations, constrained by the rest-frame infrared portion of galaxies' spectral energy distribution. We present the morphological characterization of a sample of 21 massive galaxies (\(\log(M_{\star}/M_{\odot})>9.5\)) at redshift \(3<z<5.5\). These galaxies are observed as part of the GTO program MIDIS with the Mid-Infrared Instrument (MIRI) onboard JWST. The deep MIRI 5.6~\(\mu\)m imaging allows us to characterize for the first time the rest-frame near-infrared structure of galaxies beyond cosmic noon, at higher redshifts than possible with NIRCam, tracing their older stellar populations. We derive the galaxies' non-parametric morphology and model the galaxies' light distribution with a Sérsic component. We find that at \(z>3\) massive galaxies show a smooth distribution of their rest-infrared light, strongly supporting the increasing number of regular disk galaxies already in place at early epochs. On the contrary, the ultraviolet structure obtained from HST observations is generally more irregular, catching the most recent episodes of star formation. Importantly, we find a segregation of morphologies across cosmic time, having massive galaxies at redshift \(z>4\) later-type morphologies compared to \(z\sim3\) galaxies. These findings suggest a transition phase in galaxy assembly and central mass build up already taking place at \(z\sim3-4\). MIRI provides unique information about the structure of the mature stellar population of high-redshift galaxies, unveiling that massive galaxies beyond cosmic noon are prevalently compact disk galaxies with smooth mass distribution.
We present MIRI/JWST medium-resolution spectroscopy (MRS) and imaging (MIRIM) of the lensed galaxy MACS1149-JD1 at a redshift of \(z\)=9.1092\(\pm\)0.0002 (Universe age about 530 Myr). We detect, for ...the first time, spatially resolved H\(\alpha\) emission in a galaxy at a redshift above nine. The structure of the H\(\alpha\) emitting gas consists of two clumps, S and N. The total H\(\alpha\) luminosity implies an instantaneous star-formation of 5.3\(\pm\)0.4 \(M_{\odot}\) yr\(^{-1}\) for solar metallicities. The ionizing photon production efficiency, \(\log(\zeta_\mathrm{ion})\), shows a spatially resolved structure with values of 25.55\(\pm\)0.03, 25.47\(\pm\)0.03, and 25.91\(\pm\)0.09 Hz erg\(^{-1}\) for the integrated galaxy, and clumps S and N, respectively. The H\(\alpha\) rest-frame equivalent width, EW\(_{0}\)(H\(\alpha\)), is 726\(^{+660}_{-182}\) Ángstrom for the integrated galaxy, but presents extreme values of 531\(^{+300}_{-96}\) Ángstrom and \(\geq\)1951 Ángstrom for clumps S and N, respectively. The spatially resolved ionizing photon production efficiency is within the range of values measured in galaxies at redshift above six, and well above the canonical value (25.2\(\pm\)0.1 Hz erg\(^{-1}\)). The extreme difference of EW\(_{0}\)(H\(\alpha\)) for Clumps S and N indicates the presence of a recent (<5 Myrs) burst in clump N and a star formation over a larger period of time (e.g., \(\sim\)50 Myr) in clump S. Finally, clump S and N show very different H\(\alpha\) kinematics with velocity dispersions of 56\(\pm\)4 km s\(^{-1}\) and 113\(\pm\)33 km s\(^{-1}\), likely indicating the presence of outflows or increased turbulence in the clump N. The dynamical mass, \(M_\mathrm{dyn}\)= (2.4\(\pm\)0.5)\(\times\)10\(^{9}\) \(M_{\odot}\), is within the range measured with the spatially resolved OIII88\(\mu\)m line.
