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.
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.
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.
We present MIRI/JWST medium-resolution spectroscopy (MRS) and imaging (MIRIM) of the lensed galaxy MACS1149-JD1 at a redshift of z = 9.1092 ± 0.0002, when the Universe was about 530 Myr old. We ...detect, for the first time, spatially resolved H α emission in a galaxy at a redshift above nine. The structure of the H α emitting gas consists of two clumps, S and N, carrying about 60% and 40% of the total flux, respectively. The total H α luminosity implies an instantaneous star-formation rate in the range of 3.2 ± 0.3 and 5.3 ± 0.4 M ⊙ yr −1 for sub-solar and solar metallicities. The ionizing photon production efficiency, log( ζ ion ), shows a spatially resolved structure with values of 25.55 ± 0.03; 25.47 ± 0.03; and 25.91 ± 0.09 Hz erg −1 for the integrated galaxy and clumps S and N, respectively. The H α rest-frame equivalent width, EW 0 (H α ), is 726 −182 +660 Å for the integrated galaxy, but it presents extreme values of 531 −96 +300 Å and ≥1951 Å for clumps S and N, respectively. The spatially resolved ionizing photon production efficiency is within the range of values measured in galaxies at a redshift above six and well above the canonical value (25.2 ± 0.1 Hz erg −1 ). The EW 0 (H α ) is a factor of two lower than the predicted value at z = 9.11 based on the extrapolation of the evolution of the EW 0 (H α ) with redshifts, ∝(1 + z ) 2.1 , including galaxies detected with JWST. The extreme difference of the EW 0 (H α ) for clumps S and N indicates the presence of a recent (< 5 Myr) stellar burst in clump N and a star formation over a larger period of time (e.g., ∼50 Myr) in clump S. The different ages of the stellar population place MACS1149-JD1 and clumps N and S at different locations in the log( ζ ion ) to EW 0 (H α ) plane and above the main relation defined from intermediate- and high-redshift ( z = 3 − 7) galaxies detected with JWST. Finally, clump S and N show very different H α kinematics, with velocity dispersions of 56 ± 4 km s −1 and 113 ± 33 km s −1 , likely indicating the presence of outflows or increased turbulence in clump N. The dynamical mass M dyn = (2.4 ± 0.5) × 10 9 M ⊙ , obtained from the size of the integrated H α ionized nebulae and its velocity dispersion, is within the range previously measured with the spatially resolved OIII88 μm line.
Dusty star-forming galaxies emit most of their light at far-infrared to millimeter wavelengths as their star formation is highly obscured. Far-infrared and millimeter observations have revealed their ...dust, neutral and molecular gas properties. The sensitivity of JWST at rest-frame optical and near-infrared wavelengths now allows the study of the stellar and ionized gas content. We investigate the spatially resolved distribution and kinematics of the ionized gas in GN20, a dusty star-forming galaxy at z = 4.0548. We present deep MIRI/MRS integral field spectroscopy of the near-infrared rest-frame emission of GN20. We detect spatially resolved Pa α , out to a radius of 6 kpc, distributed in a clumpy morphology. The star formation rate derived from Pa α (144 ± 9 M ⊙ yr −1 ) is only 7.7 ± 0.5% of the infrared star formation rate (1860 ± 90 M ⊙ yr −1 ). We attribute this to very high extinction ( A V = 17.2 ± 0.4 mag, or A V , mixed = 44 ± 3 mag), especially in the nucleus of GN20, where only faint Pa α is detected, suggesting a deeply buried starburst. We identify four, spatially unresolved, clumps in the Pa α emission. Based on the double peaked Pa α profile, we find that each clump consists of at least two sub-clumps. We find mass upper limits consistent with them being formed in a gravitationally unstable gaseous disk. The ultraviolet bright region of GN20 does not have any detected Pa α emission, suggesting an age of more than 10 Myr for this region of the galaxy. From the rotation profile of Pa α , we conclude that the gas kinematics are rotationally dominated and the v rot / σ m = 3.8 ± 1.4 is similar to low-redshift luminous infrared galaxies. From the Pa α kinematics, we cannot distinguish between a rotational profile of a large disk and a late stage merger mimicking a disk. We speculate that GN20 is in the late stage of a major merger, where the clumps in a large gas-rich disk are created by the major merger, while the central starburst is driven by the merger event.
Context.
The kinematics of galaxies provide valuable insights into their physics and assembly history. Kinematics are governed not only by the gravitational potential, but also by merger events and ...stellar feedback processes such as stellar winds and supernova explosions.
Aims.
We aim to identify what governs the kinematics in a sample of SDSS-selected nearby starburst galaxies, by obtaining spatially resolved measurements of the gas and stellar kinematics.
Methods.
We obtained near-infrared integral-field
K
-band spectroscopy with VLT/SINFONI for 15 compact starburst galaxies. We derived the integrated as well as spatially resolved stellar and gas kinematics. The stellar kinematics were derived from the CO absorption bands, and Pa
α
and Br
γ
emission lines were used for the gas kinematics.
Results.
Based on the integrated spectra, we find that the majority of galaxies have gas and stellar velocity dispersion that are comparable. A spatially resolved comparison shows that the six galaxies that deviate show evidence for a bulge or stellar feedback. Two galaxies are identified as mergers based on their double-peaked emission lines. In our sample, we find a negative correlation between the ratio of the rotational velocity over the velocity dispersion (
v
rot
/
σ
) and the star formation rate surface density.
Conclusions.
We propose a scenario where the global kinematics of the galaxies are determined by gravitational instabilities that affect both the stars and gas. This process could be driven by mergers or accretion events. Effects of stellar feedback on the ionised gas are more localised and detected only in the spatially resolved analysis. The mass derived from the velocity dispersion provides a reliable mass even if the galaxy cannot be spatially resolved. The technique used in this paper is applicable to galaxies at low and high redshift with the next generation of infrared-focussed telescopes (JWST and ELT).
Abstract
We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6
μ
m imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at
z
≃ 7–8. Out ...of a total of 58 galaxies at
z
≃ 7–8, we find 18 robust candidates (≃31%) for (H
β
+ O
iii
) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW
0
(H
β
+O
iii
) ≃87–2100 Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6
μ
m, indicating the simultaneous presence of a prominent H
α
emission line with EW
0
(H
α
) ≃200–3000 Å. This is the first time that H
α
emission can be detected in individual galaxies at
z
> 7. The H
α
line, when present, allows us to separate the contributions of H
β
and O
iii
to the (H
β
+O
iii
) complex and derive H
α
-based star formation rates (SFRs). We find that in most cases O
iii
/H
β
> 1. Instead, two galaxies have O
iii
/H
β
< 1, indicating that the NIRCam flux excess is mainly driven by H
β
. 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
log
10
(
ρ
SFR
H
α
/
(
M
⊙
yr
−
1
Mpc
−
3
)
)
≃
−
2.35
, which is about a quarter of the total value (
log
10
(
ρ
SFR
tot
/
(
M
⊙
yr
−
1
Mpc
−
3
)
)
≃
−
1.76
) at
z
≃ 7–8. Therefore, the strong H
α
emitters likely had a significant role in reionization.
PDF
![MIDIS: Strong (Hβ+[O iii]) ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "MIDIS: Strong (Hβ+[O iii]) and Hα Emitters at Redshift z ≃ 7–8 Unveiled with JWST NIRCam and MIRI Imaging in the Hubble eXtreme Deep Field")