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We present a first look at the MRS observations of the nucleus of the nearby galaxy M83, taken with MIRI on board JWST. The observations show a rich set of emission features from the ionized gas, warm molecular gas, and dust. To begin dissecting the complex processes in this part of the galaxy, we divide the observations into four different regions. We find that the strength of the emission features varies strongly from region to region, with the southeast region displaying the weakest features tracing the dust continuum and interstellar medium (ISM) properties. Comparison between the cold molecular gas traced by the 12CO (1–0) transition with the Atacama Large Millimeter/submillimeter Array and the H2 S(1) transition shows a similar spatial distribution. This is in contrast to the distribution of the much warmer H2 emission from the S(7) transition found to be concentrated around the optical nucleus. We use the rotational emission lines and model the H2 excitation to estimate a total molecular gas mass accounting for the warm H2 component of M (>50 K) H 2 = 67.90 (±5.43) × 106 M ⊙. We compare this value to the total gas mass inferred by probing the cold H2 gas through the 12CO (1–0) emission, M (CO) H 2 = 17.15 × 106 M ⊙. We estimate that ∼75% of the total molecular gas mass is contained in the warm H2 component. We also identify [O iv ] 25.89 μ m and [Fe ii ] 25.99 μ m emission. We propose that the diffuse [Fe ii ] 25.99 μ m emission might be tracing shocks created during the interactions between the hot wind produced by the starburst and the much cooler ISM above the galactic plane. More detailed studies are needed to confirm such a scenario. [ABSTRACT FROM AUTHOR]

I summarize the rich variety of talks and posters at this meeting, Young massive star clusters. Initial conditions and environments, which concentrated on young massive clusters (YMCs) and, in particular, the initial conditions required for their formation and survival as well as the importance of their environments. [ABSTRACT FROM AUTHOR]

The exact nature of the interaction between hot, fast-flowing star-cluster winds and the surrounding clumpy interstellar medium (ISM) in starburst galaxies has very few observational constraints. Besides furthering our knowledge of ISM dynamics, detailed observations of ionised gas at the very roots of large-scale outflows are required to place limits on the current generation of high-resolution galactic wind models. To this end, we conduct a detailed investigation of the ionised gas environment surrounding the young star clusters in the starburst galaxy NGC1569. Using high spatial and spectral-resolution Gemini/GMOS integral-field unit observations, we accurately characterise the line-profile shapes of the optical nebular emission lines and find a ubiquitous broad (∼300 km s−1) component underlying a bright narrower component. By mapping the properties of the individual line components, we find correlations that suggest that the broad component results from powerful cluster wind–gas clump interactions. We propose a model to explain the properties of the line components and the general turbulent state of the ISM. [ABSTRACT FROM AUTHOR]

We present new spectral synthesis models for solar metallicity stellar populations, based on a library of stellar spectra that extends across near-IR wavelengths out to 2.4 µm at a resolution approaching 1000. We show that the spectra of massive star clusters in the starburst galaxy M 82 can be reproduced very well with these models. We compare near-IR spectroscopic ages with optical ages, and discuss the main sources of (systematic) errors that still affect those ages. [ABSTRACT FROM AUTHOR]

We present virial mass estimates of young massive clusters (YMCs) in the starburst galaxies NGC1140 and M83, determined from high spectral resolution VLT echelle spectroscopy and high spatial resolution Hubble Space Telescope imaging. The survivability of such clusters is important in testing the scenario that YMCs are potentially proto-globular clusters. As young clusters, they lie in the domain in which dynamical masses appear to overestimate true cluster masses, most likely due to the clusters not being virialised. We find that the dynamical mass of NGC1140-1 is approximately ten times greater than its photometric mass. We propose that the most likely explanation for this disparity is the crowded environment of NGC1140-1, rather than this being solely due to a lack of virial equilibrium. [ABSTRACT FROM AUTHOR]

The post-starburst region B in M82 and its massive star cluster component have been the focus of multiple studies, with reports that there is a large population of coeval clusters of age ∼1 Gyr, which were created with a Gaussian initial mass distribution. This is in disagreement with other studies of young star clusters, which invariably find a featureless power-law mass distribution. Here, we present Gemini-North optical spectra of seven star clusters in M82-B and show that their ages are all between 10 and 300 Myr (a factor of 3–100 younger than previous photometric results) and that their extinctions range between near zero and 4 mag ( A V). Using new HST ACS-HRC U-band observations we age date an additional ∼30 clusters whose ages/extinctions agree well with those determined from spectroscopy. Completeness tests show that the reported ‘turn-over’ in the luminosity/mass distributions is most likely an artefact, due to the resolved nature of the clusters. We also show that the radial velocities of the clusters are inconsistent with them belonging to a bound region. [ABSTRACT FROM AUTHOR]

The young resolved cluster NGC 346 in the SMC provides us with the opportunity to study the details of cluster formation and the efficiency of feedback mechanisms at low metallicity. I describe the latest results from a large-scale study of this cluster and its H II region N66. HST/ACS images reveal that NGC 346 is composed of a number of sub-clusters which appear to be coeval with ages of 3±1 Myr, strongly suggesting formation by the hierarchical fragmentation of a giant molecular cloud (Nota et al. 2006; Sabbi et al. 2007a). HST Hα images show that the central cluster and the sub-clusters still contain some of their residual gas. We present high resolution spectroscopy of the ionized gas, and find that it shows little evidence for gas motions. This suggests that, at the low SMC metallicity, the cluster O star winds are not powerful enough to sweep away the residual gas. Instead, we find that stellar radiation is the dominant process shaping the interstellar environment of NGC 346. [ABSTRACT FROM AUTHOR]

We present new high spectral resolution Very Large Telescope (VLT)/UV–Visual Echelle Spectrograph (UVES) spectroscopy and archival Hubble Space Telescope ( HST)/Space Telescope Imaging Spectrograph (STIS) imaging and spectroscopy of the giant H ii region Tol 89 in NGC 5398. From optical and ultraviolet (UV) HST images, we find that the star-forming complex as a whole contains at least seven young compact massive clusters. We resolve the two brightest optical knots, A and B, into five individual young massive clusters along our slit, A1–4 and B1, respectively. From UV spectral modelling using thestarburst99 code of Leitherer et al., and nebular Hβ equivalent widths in the optical, we derive ages that are consistent with the formation of two separate burst events, of and <3 Myr for knots A (A1–4) and B (B1), respectively. A Large Magellanic Cloud (LMC) metallicity is measured for both knots from a nebular line analysis, while nebular He ii 4686 is observed in knot B and perhaps in knot A. We detect underlying broad wings on the strongest nebular emission lines indicating velocities up to 600 km s−1. From UV and optical spectroscopy, we estimate that there are ∼95 early WN stars and ∼35 early WC stars in Tol 89-A, using empirical template spectra of LMC Wolf–Rayet (WR) stars from Crowther & Hadfield, with the WC population confined to cluster A2. Remarkably, we also detect a small number of approximately three mid WNs in the smallest (mass) cluster in Tol 89-A, A4, whose spectral energy output in the UV is entirely dominated by the WN stars. From the strength of nebular Hβ, we obtain N(O) ∼ 690 and 2800 for knots A and B, respectively, which implies N(WR)/ N(O) ∼ 0.2 for knot A. We also employ a complementary approach usingstarburst99 models, in which the O star content is inferred from the stellar continuum, and the WR population is obtained from spectral synthesis of optical WR features using the grids from Smith et al. We find reasonable agreement between the two methods for the O star content and the N(WR)/ N(O) ratio but find that the WR subtype distribution is in error in thestarburst99 models, with far too few WN stars being predicted. We attribute this failure to the neglect of rotational mixing in evolutionary models. Our various modelling approaches allow us to measure the cluster masses. We identify A1 as a super star cluster (SSC) candidate with a mass of . A total mass of is inferred for the ionizing sources within Tol 89-B. [ABSTRACT FROM AUTHOR]

Star formation in starbursts produces compact star clusters which extend in mass up to the super star clusters (SSCs) which resemble young globular clusters. Compact young massive star clusters (cYMCs) in turn cluster along with other young stars into starburst clumps. Using M82 as an example we briefly review how the presence of starburst clumps affects the evolution of the host galaxy. Extremely large telescopes (ELTs) will be essential for understanding how starburst clumps and their constituent star clusters evolve. In nearby systems their combination of sensitivity and angular resolution will allow us to explore the structures, kinematics, and abundances of cYMCs. For systems at cosmological distances the high surface brightnesses of the starburst clumps makes them prime gateways for exploring the early evolution of galaxies. [ABSTRACT FROM PUBLISHER]

Presents a grid for ionizing fluxes for stellar populations. Atmospheres; Stellar content; Galaxies.

We present high-dispersion echelle spectroscopy of the very luminous, young super star cluster (SSC) ‘F’ in M82, obtained with the 4.2-m William Herschel Telescope, for the purpose of deriving its dynamical mass and assessing whether it will survive to become an old globular cluster. In addition to the stellar lines, the spectrum contains complex Na iabsorption and broad emission lines from the ionized gas. We measure a stellar velocity dispersion of 13.4±0.7 km s[sup -1] and a projected half-light radius of 2.8±0.3 pc from archival HST/WFPC2 images, and derive a dynamical mass of 1.2±0.1×10[sup 6] M[sub ⊙], demonstrating that M82-F is a very massive, compact cluster. We determine that the current luminosity-to-mass ratio (L[sub V]/M)[sub ⊙] for M82-F is 45±13. Comparison with spectral synthesis models shows that (L[sub V]/M)[sub ⊙] is a factor of ∼ 5 higher than that predicted for a standard Kroupa initial mass function (IMF) at the well-determined age for M82-F of 60±20 Myr. This high value of (L[sub V]/M)[sub ⊙] indicates a deficit of low-mass stars in M82-F; the current mass function (MF) evidently is ‘top-heavy’. We find that a lower mass cut-off of 2–3 M[sub ⊙] is required to match the observations for a MF with a slope α=2.3. Since the cluster apparently lacks long-lived low-mass stars, it will not become an old globular cluster, but probably will dissolve at an age of ≤ 2 Gyr. We also derive updated luminosity-to-mass ratios for the younger SSCs NGC 1569A and 1705-1. For the first object, the observations are consistent with a slightly steeper MF (α=2.5), whereas for NGC 1705-1 the observed ratio requires the MF to be truncated near 2 M[sub ⊙] for a slope of α=2.3. We discuss the implications of our findings in the context of large-scale IMF variations; with the present data the top-heavy MF could reflect a local mass segregation effect during the birth of the cluster. M82-F probably formed in a dense molecular cloud; however, its high radial velocity with respect to the centre of M82 (∼-175 km s[sup -1]) suggests that it is on an eccentric orbit and now far from its birthplace, so the environment of its formation is unknown. [ABSTRACT FROM AUTHOR]

Examines the peculiar Galactic emission-line object NaSt1. Presence of reddened nebular spectrum with strong permitted and forbidden lines covering excitation; Determination of physical parameters and abundance from the nebular forbidden lines; Comparison of spectral appearance of NaSt1 with luminous emission-line objects.