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Register a new userCandidate Population III stellar complex at z=6.629 in the MUSE Deep Lensed Field
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We discovered a strongly lensed (mu >40) Lya emission at z=6.629 (S/N~18) in the MUSE Deep Lensed Field (MDLF) targeting the Hubble Frontier Field galaxy cluster MACS~J0416. Dedicated lensing simulations imply that the Lya emitting region necessarily crosses the caustic. The arc-like shape of the Lya extends 3 arcsec on the observed plane and is the result of two merged multiple images, each one with a de-lensed Lya luminosity L<~2.8 x 10^(40) erg/s arising from a confined region (< 150 pc effective radius). A spatially unresolved HST counterpart is barely detected at S/N~2 after stacking the near-infrared bands, corresponding to an observed(intrinsic) magnitude m_(1500)>~30.8(>~35.0). The inferred rest-frame Lya equivalent width is EWo > 1120 A if the IGM transmission is T(IGM)<0.5. The low luminosities and the extremely large Lya EWo match the case of a Population~III star complex made of several dozens stars (~ 10^4 Msun) which irradiate a HII region crossing the caustic. While the Lya and stellar continuum are among the faintest ever observed at this redshift, the continuum and the Lya emissions could be affected by differential magnification, possibly biasing the EWo estimate. The aforementioned tentative HST detection tend to favor a large EWo, making such a faint Pop~III candidate a key target for the James Webb Space Telescope and Extremely Large Telescopes.
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Context: A census of faint and tiny star forming complexes at high redshift is key to improving our understanding of reionizing sources, galaxy growth and the formation of globular clusters. Aims: We present the MUSE Deep Lensed Field (MDLF) program. Methods: We describe Deep MUSE observations of 17.1 hours integration on a single pointing over the Hubble Frontier Field galaxy cluster MACS~J0416. Results: We confirm spectroscopic redshifts for all 136 multiple images of 48 source galaxies at 0.9<z<6.2. Within those galaxies, we securely identify 182 multiple images of 66 galaxy components that we use to constrain our lens model. We identify 116 clumps belonging to background high-z galaxies; the majority of them are multiple images and span magnitude, size and redshift intervals of [-18,-10], [~400-3] parsec and 1<z<6.6, respectively, with the most magnified ones probing possible single gravitationally bound star clusters. The depth of the MDLF combined with lensing magnification lead us to reach a detection limit for unresolved emission lines of a few 10$^{-20}$ erg/s/cm2, after correction for lensing magnification. Ultraviolet high-ionization metal lines (and HeII1640) are detected with S/N>10 for individual objects down to de-lensed magnitude 28-30 suggesting that they are common in such faint sources. Conclusions:Deep MUSE observations, in combination with existing HST imaging, allowed us to:(1) confirm redshifts for extremely faint high-z sources;(2) peer into their internal clumps (down to 100-200 pc scale);(3) in some cases break down such clumps into bound star clusters (<20 pc scale);(4) double the number of constraints for the lens model,reaching an unprecedented set of 182 bona-fide multiple images and confirming up to 213 galaxy cluster members. These results demonstrate the power that JWST and future ELTs will have when combined to study gravitational telescopes.[abridged]
We present spatially resolved stellar kinematic maps, for the first time, for a sample of 17 intermediate redshift galaxies (0.2 < z < 0.8). We used deep MUSE/VLT integral field spectroscopic observations in the Hubble Deep Field South (HDFS) and Hubble Ultra Deep Field (HUDF), resulting from ~30h integration time per field, each covering 1x1 field of view, with ~0.65 spatial resolution. We selected all galaxies brighter than 25mag in the I band and for which the stellar continuum is detected over an area that is at least two times larger than the spatial resolution. The resulting sample contains mostly late-type disk, main-sequence star-forming galaxies with 10^8.5 - 10^10.5 Msun. Using a full-spectrum fitting technique, we derive two-dimensional maps of the stellar and gas kinematics, including the radial velocity V and velocity dispersion sigma. We find that most galaxies in the sample are consistent with having rotating stellar disks with roughly constant velocity dispersions and that the Vrms=sqrt{V^2+sigma^2} of the gas and stars, a scaling proxy for the galaxy gravitational potential, compare well to each other. These spatially resolved observations of intermediate redshift galaxies suggest that the regular stellar kinematics of disk galaxies that is observed in the local Universe was already in place 4 - 7 Gyr ago and that their gas kinematics traces the gravitational potential of the galaxy, thus is not dominated by shocks and turbulent motions. Finally, we build dynamical axisymmetric Jeans models constrained by the derived stellar kinematics for two specific galaxies and derive their dynamical masses. These are in good agreement (within 25%) with those derived from simple exponential disk models based on the gas kinematics. The obtained mass-to-light ratios hint towards dark matter dominated systems within a few effective radii.
Disc-halo decomposition on rotationally supported star-forming galaxies (SFGs) at $z>1$ are often limited to massive galaxies ($M_star>10^{10}~M_odot$) and rely on either deep Integral Field Spectroscopy data or stacking analyses. We present a study of the dark matter (DM) content of 9 $zapprox1$ SFGs selected Using the brightest [OII] emitters in the deepest Multi-Unit Spectrograph Explorer (MUSE) field to date, namely the 140hr MUSE Extremely Deep Field, we perform disk-halo decompositions on 9 low-mass SFGs (with $10^{8.5}<M_star<10^{10.5}~M_odot$) using a novel 3D modeling approach, which together with the exquisite S/N allows us to measure individual rotation curves to $3times R_e$. The DM component primarily uses the generalized $alpha,beta,gamma$ profile from Di Cintio et al., or a Navarro-Frenk-White (NFW) profile. The disk stellar masses $M_star$ obtained from the [OII] disk-halo decomposition agree with the values inferred from the spectral energy distributions. While the rotation curves show diverse shapes, ranging from rising to declining at large radii, the DM fractions within the half-light radius $f_{rm DM}(<R_e)$ are found to be 60% to 95%, extending to lower masses (densities) the results of Genzel et al., who found low DM fractions in SFGs with $M_star>10^{10}~M_odot$. The DM halos show constant surface densities of $sim100~M_odot$ pc$^{-2}$. Half of the sample shows a strong preference for cored over cuspy DM profiles. The presence of DM cores appears to be related to galaxies with stellar-to-halo mass $log M_star/M_{rm vir}approx-2.5$. In addition, the cuspiness of the DM profiles is found to be a strong function of the recent star-formation activity. Both of these results are interpreted as evidence for feedback-induced core formation in the Cold Dark Matter context.
Star-forming galaxies have been found to follow a relatively tight relation between stellar mass ($M_{*}$) and star formation rate (SFR), dubbed the `star formation sequence. A turnover in the sequence has been observed, where galaxies with $M_{*} < 10^{10} {rm M}_{odot}$ follow a steeper relation than their higher mass counterparts, suggesting that the low-mass slope is (nearly) linear. In this paper, we characterise the properties of the low-mass end of the star formation sequence between $7 leq log M_{*}[{rm M}_{odot}] leq 10.5$ at redshift $0.11 < z < 0.91$. We use the deepest MUSE observations of the Hubble Ultra Deep Field and the Hubble Deep Field South to construct a sample of 179 star-forming galaxies with high signal-to-noise emission lines. Dust-corrected SFRs are determined from H$beta$ $lambda 4861$ and H$alpha$ $lambda 6563$. We model the star formation sequence with a Gaussian distribution around a hyperplane between $log M_{*}$, $log {rm SFR}$, and $log (1+z)$, to simultaneously constrain the slope, redshift evolution, and intrinsic scatter. We find a sub-linear slope for the low-mass regime where $log {rm SFR}[{rm M}_{odot}/{rm yr}] = 0.83^{+0.07}_{-0.06} log M_{*}[{rm M}_{odot}] + 1.74^{+0.66}_{-0.68} log (1+z)$, increasing with redshift. We recover an intrinsic scatter in the relation of $sigma_{rm intr} = 0.44^{+0.05}_{-0.04}$ dex, larger than typically found at higher masses. As both hydrodynamical simulations and (semi-)analytical models typically favour a steeper slope in the low-mass regime, our results provide new constraints on the feedback processes which operate preferentially in low-mass halos.
Massive early-type galaxies are believed to be the end result of an extended mass accretion history. The stars formed in situ very early on in the initial phase of the assembly might have originated from an extremely intense star formation burst, and may still be found within the cores of such galaxies today. We investigate the presence of a surviving high-$z$ compact progenitor component in the brightest galaxy of the Hydra I cluster, NGC 3311, by mapping its 2D kinematics and stellar population out to 2 effective radii, combining MUSE observations, extended EMILES models, and a newly developed parametric fully Bayesian framework using full-spectrum fitting. We present 2D maps and radial profiles of the stellar velocity dispersion, age, total metallicity, $alpha$-element, sodium abundance ([Na/Fe]), and the initial mass function (IMF) slope. All properties have significant gradients, confirming the existence of multiple structural components, including a young, metal-rich blue spot. We find that the component dominating the light budget of NGC 3311 within $Rlesssim 2.0$ kpc is the surviving $z=0$ analog of a high-$z$ compact core. This concentrated structure has a relatively small velocity dispersion ($sigma_*approx 180$ km s$^{-1}$), is very old (ages$gtrsim 11$ Gyr), metal-rich ([Z/H]$sim0.2$ and [Na/Fe]$sim0.4$), and has a bottom-heavy IMF (with slope $Gamma_bsim2.4$). In the outer region, stars become increasingly hotter, younger, metal and sodium poorer, $alpha$-element richer, and the IMF slope becomes Chabrier-like. The multiple structural components in NGC 3311 confirm the predictions from the two-phase formation scenario for NGC 3311. Interestingly, the outer stellar population has an overabundant [$alpha$/Fe], most likely because NGC 3311, located at the center of the galaxy cluster, accreted stars from rapidly quenched satellites.[Abridged]
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