| 1. |
- Adamo, Angela, 1981-, et al.
(författare)
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The ages and metallicities of the globular clusters in the Sparkler
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 525:1, s. L6-L10
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Tidskriftsartikel (refereegranskat)abstract
- JWST observations of the strongly lensed galaxy the Sparkler have revealed a population of gravitationally bound globular cluster (GC) candidates. Different analyses have resulted in broadly similar ages but significantly different metallicities, questioning the assembly history that has led to the formation of such a population. In this letter, we reanalyse the two sets of photometry available in the literature with the code MCMAME especially tailored to fit physical properties of GCs. We find the ages and metallicities from both data sets are consistent within 1σ uncertainties. A significant group of GCs is consistent with being old and metal poor ([Fe/H] ∼ −1.7). For this group, the ages do not converge, hence, we conclude that they are definitively older than 1 Gyr and can be as old as the age of the Universe. The remaining GCs have younger ages and a metallicity spread. The ages and metallicities distribution of GCs in the Sparkler are consistent with those observed in Local Group’s galaxies at similar lookback times. Comparing with predictions from E-MOSAICS simulations we confirm that the Sparkler GC population traces the self-enrichment history of a galaxy which might become a few times 109 M⊙ massive system at redshift z = 0.
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| 2. |
- Cabrera-Ziri, I., et al.
(författare)
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Searching for globular cluster chemical anomalies on the main sequence of a young massive cluster
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 495:1, s. 375-382
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Tidskriftsartikel (refereegranskat)abstract
- The spectroscopic and photometric signals of the star-to-star abundance variations found in globular clusters seem to be correlated with global parameters like the cluster's metallicity, mass, and age. Understanding this behaviour could bring us closer to the origin of these intriguing abundance spreads. In this work we use deep HST photometry to look for evidence of abundance variations in the main sequence of a young massive cluster NGC 419 (similar to 10(5) M-circle dot, similar to 1.4 Gyr). Unlike previous studies, here we focus on stars in the same mass range found in old globulars (similar to 0.75-1 M-circle dot), where light elements variations are detected. We find no evidence for N abundance variations among these stars in the Un - B and U - B colour-magnitude diagrams of NGC 419. This is at odds with the N variations found in old globulars like 47 Tuc, NGC 6352, and NGC 6637 with similar metallicity to NGC 419. Although the signature of the abundance variations characteristic of old globulars appears to be significantly smaller or absent in this young cluster, we cannot conclude if this effect is mainly driven by its age or its mass.
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| 3. |
- Della Bruna, Lorenza, et al.
(författare)
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Stellar feedback in M 83 as observed with MUSE II. Analysis of the H II region population : Ionisation budget and pre-SN feedback
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Context. Energy and momentum injected by young, massive stars into the surrounding gas play an important role in regulating further star formation and in determining the galaxy's global properties. Before supernovae begin to explode, stellar feedback consists of two main processes: radiation pressure and photoionisation.Aims. We study pre-supernova feedback and constrain the leakage of Lyman continuum (LyC) radiation in a sample of similar to 4700 H II regions in the nearby spiral galaxy M 83. We explore the impact that the galactic environment and intrinsic physical properties (metallicity, extinction, and stellar content) have on the early phases of H II region evolution.Methods. We combined VLT/MUSE observations of the ionised gas with young star cluster physical properties derived from HST multiwavelength data. We identified H II regions based on their Hα emission, and cross-matched the sample with planetary nebulae and supernova remnants to assess contaminant sources and identify evolved H II regions. We also spectroscopically identified Wolf-Rayet (WR) stars populating the star-forming regions. We estimated the physical properties of the H II regions (luminosity, size, oxygen abundance, and electron density). For each H II region, we computed the pressure of ionised gas (Pion) and the direct radiation pressure (Pdir) acting in the region, and investigated how they vary with galactocentric distance, with the physical properties of the region, and with the pressure of the galactic environment (PDE). For a subset of similar to 500 regions, we also investigated the link between the pressure terms and the properties of the cluster population (age, mass, and LyC flux). By comparing the LyC flux derived from Hα emission with the one modelled from their clusters and WRs, we furthermore constrained any escape of LyC radiation (fesc).Results. We find that Pion dominates over Pdir by at least a factor of 10 on average over the disk. Both pressure terms are strongly enhanced and become almost comparable in the central starburst region. In the disk (R ≥ 0.15Re), we observe that Pdir stays approximately constant with galactocentric distance. We note that Pdir is positively correlated with an increase in radiation field strength (linked to the negative metallicity gradient in the galaxy), while it decreases in low extinction regions, as is expected if the amount of dust to which the momentum can be imparted decreases. In addition, Pion decreases constantly for increasing galactocentric distances; this trend correlates with the decrease in extinction - indicative of more evolved and thus less compact regions - and with changes in the galactic environment (traced by a decrease in PDE). In general, we observe that H II regions near the centre are underpressured with respect to their surroundings, whereas regions in the rest of the disk are overpressured and hence expanding. We find that regions hosting younger clusters or those that have more mass in young star clusters have a higher internal pressure, indicating that clustered star formation likely plays a dominant role in setting the pressure. Finally, we estimate that only 13% of H II regions hosting young clusters and WR stars have fesc ≥ 0, which suggests that star formation taking place outside young clusters makes a non-negligible contribution to ionising H II regions.
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| 4. |
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| 5. |
- Della Bruna, Lorenza, et al.
(författare)
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Stellar feedback in M83 as observed with MUSE I. Overview, an unprecedented view of the stellar and gas kinematics and evidence of outflowing gas
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
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Tidskriftsartikel (refereegranskat)abstract
- Context. Young massive stars inject energy and momentum into the surrounding gas, creating a multi-phase interstellar medium (ISM) and regulating further star formation. The main challenge of studying stellar feedback proves to be the variety of scales spanned by this phenomenon, ranging from the immediate surrounding of the stars (H II regions, 10s pc scales) to galactic-wide kiloparsec scales.Aims. We present a large mosaic (3.8 × 3.8 kpc) of the nearby spiral galaxy M83, obtained with the MUSE instrument at ESO Very Large Telescope. The integral field spectroscopy data cover a large portion of the optical disk at a resolution of ∼20 pc, allowing the characterisation of single H II regions while sampling diverse dynamical regions in the galaxy.Methods. We obtained the kinematics of the stars and ionised gas, and compared them with molecular gas kinematics observed in CO(2-1) with the ALMA telescope array. We separated the ionised gas into H II regions and diffuse ionised gas (DIG) and investigated how the fraction of Hα luminosity originating from the DIG (fDIG) varies with galactic radius.Results. We observe that both stars and gas trace the galactic disk rotation, as well as a fast-rotating nuclear component (30″ ≃ 700 pc in diameter), likely connected to secular processes driven by the galactic bar. In the gas kinematics, we observe a stream east of the nucleus (50″ ≃ 1250 pc in size), redshifted with respect to the disk. The stream is surrounded by an extended ionised gas region (1000 × 1600 pc) with enhanced velocity dispersion and a high ionisation state, which is largely consistent with being ionised by slow shocks. We interpret this feature as either the superposition of the disk and an extraplanar layer of DIG, or as a bar-driven inflow of shocked gas. A double Gaussian component fit to the Hα line also reveals the presence of a nuclear biconic structure whose axis of symmetry is perpendicular to the bar. The two cones (20″ ≃ 500 pc in size) appear blue- and redshifted along the line of sight. The cones stand out for having an Hα emission separated by up to 200 km s−1 from that of the disk, and a high velocity dispersion ∼80–200 km s−1. At the far end of the cones, we observe that the gas is consistent with being ionised by shocks. These features had never been observed before in M83; we postulate that they are tracing a starburst-driven outflow shocking into the surrounding ISM. Finally, we obtain fDIG ∼ 13% in our field of view, and observe that the DIG contribution varies radially between 0.8 and 46%, peaking in the interarm region. We inspect the emission of the H II regions and DIG in ‘BPT’ diagrams, finding that in H II regions photoionisation accounts for 99.8% of the Hα flux, whereas the DIG has a mixed contribution from photoionisation (94.9%) and shocks (5.1%).
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| 6. |
- Kamann, Sebastian, et al.
(författare)
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Exploring the role of binarity in the origin of the bimodal rotational velocity distribution in stellar clusters
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 508:2, s. 2302-2306
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Tidskriftsartikel (refereegranskat)abstract
- Many young- and intermediate-age massive stellar clusters host bimodal distributions in the rotation rates of their stellar populations, with a dominant peak of rapidly rotating stars and a secondary peak of slow rotators. The origin of this bimodal rotational distribution is currently debated and two main theories have been put forward in the literature. The first is that all/most stars are born as rapid rotators and that interacting binaries break a fraction of the stars, resulting in two populations. The second is that the rotational distribution is a reflection of the early evolution of pre-main sequence stars, in particular, whether they are able to retain or lose their protoplanetary discs during the first few Myr. Here, we test the binary channel by exploiting multi-epoch Very Large Telescope/MUSE observations of NGC 1850, an similar to 100 Myr massive cluster in the Large Magellanic Cloud, to search for differences in the binary fractions of the slow- and fast-rotating populations. If binarity is the cause of the rotational bimodality, we would expect that the slowly rotating population should have a much larger binary fraction than the rapid rotators. However, in our data we detect similar fractions of binary stars in the slow and rapidly rotating populations (5.9 +/- 1.1 and 4.5 +/- 0.6 per cent, respectively). Hence, we conclude that binarity is not a dominant mechanism in the formation of the observed bimodal rotational distributions.
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| 7. |
- Kamann, S., et al.
(författare)
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The effects of stellar rotation along the main sequence of the 100-Myr-old massive cluster NGC 1850
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 518:1, s. 1505-1521
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Tidskriftsartikel (refereegranskat)abstract
- Young star clusters enable us to study the effects of stellar rotation on an ensemble of stars of the same age and across a wide range in stellar mass and are therefore ideal targets for understanding the consequences of rotation on stellar evolution. We combine MUSE spectroscopy with HST photometry to measure the projected rotational velocities (Vsin i) of 2184 stars along the split main sequence and on the main sequence turn-off (MSTO) of the 100 Myr-old massive (10(5) M-circle dot) star cluster NGC 1850 in the Large Magellanic Cloud. At fixed magnitude, we observe a clear correlation between Vsin i and colour, in the sense that fast rotators appear redder. The average Vsin i values for stars on the blue and red branches of the split main sequence are similar to 100 km s(-1) and similar to 200 km s(-1), respectively. The values correspond to about 25 - 30 per cent and 50 - 60 per cent of the critical rotation velocity and imply that rotation rates comparable to those observed in field stars of similar masses can explain the split main sequence. Our spectroscopic sample contains a rich population of similar to 200 fast rotating Be stars. The presence of shell features suggests that 23 per cent of them are observed through their decretion discs, corresponding to a disc opening angle of 15 degrees. These shell stars can significantly alter the shape of the MSTO, hence care should be taken when interpreting this photometric feature. Overall, our findings impact our understanding of the evolution of young massive clusters and provide new observational constraints for testing stellar evolutionary models.
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| 8. |
- Kuruvanthodi, A., et al.
(författare)
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Search strategies for supermassive stars in young clusters and application to nearby galaxies
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 674
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Tidskriftsartikel (refereegranskat)abstract
- Context. Supermassive stars (SMSs) with masses M?10(3)-10(4)M(?) formed by runaway collisions in young, massive, and dense star clusters have been invoked as a possible solution to the problem of the presence of multiple stellar populations and peculiar abundance patterns observed in globular clusters (GCs). However, no such objects have been observed so far.Aims. We aim to develop observational strategies to search for SMSs hosted within young massive clusters (thought to be the precursors of GCs) using both photometric and spectroscopic observations. Such strategies could be applicable in a relatively general fashion.Methods. We used theoretical predictions of the spectra of SMSs and SMS-hosting clusters, together with predictions from standard simple stellar populations to examine their impact on color-color diagrams and on individual optical spectral lines (primarily hydrogen emission and absorption lines). As a first step, we applied our search strategies to a sample of about 3000 young star clusters (YSCs) from two nearby galaxies with multiband observations from the HST and optical integral-field spectroscopy obtained with MUSE on the Very Large Telescope.Results. We focus on models for SMSs with large radii (corresponding to T-eff ? 7000 K), which predict strong Balmer breaks, and construct proper color-color diagrams to select the corresponding SMS-hosting cluster candidates. We show that the spectrophotometric properties of these latter are similar to those of normal clusters with ages of a few hundred million years. However, the cluster SEDs show signs of composite stellar populations due to the presence of nebular lines (Ha and others). Examining the photometry, overall SEDs, and the spectra of approximately 100 clusters with strong Balmer breaks, we find several objects with peculiar SEDs, the presence of emission lines, or other peculiar signatures. After careful inspection of the available data, we do not find good candidates of SMS-hosting clusters. In most cases, the composite spectra can be explained by multiple clusters or H II regions inside the aperture covered by the spectra, by contamination from a planetary nebula or diffuse gas, or by improper background subtraction. Furthermore, most of our candidate clusters are too faint to host SMSs.Conclusions. We demonstrate a strategy to search for SMSs by applying it to a sample of YSCs in two nearby galaxies. Our method can be applied to larger samples and also extended to higher redshifts with existing and upcoming telescopes, and therefore should provide an important test for GC-formation scenarios invoking such extreme stars.
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| 9. |
- Martocchia, S., et al.
(författare)
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Leveraging HST with MUSE : II. Na-abundance variations in intermediate age star clusters
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:1, s. 1200-1211
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Tidskriftsartikel (refereegranskat)abstract
- Ancient (>10 Gyr) globular clusters (GCs) show chemical abundance variations in the form of patterns among certain elements, e.g. N correlates with Na and anticorrelates with O. Recently, N abundance spreads have also been observed in massive star clusters that are significantly younger than old GCs, down to an age of similar to 2Gyr. However, so far N has been the only element found to vary in such young objects. We report here the presence of Na abundance variations in the intermediate age massive star clusters NGC 416 (similar to 6.5Gyr old) and Lindsay 1 (similar to 7.5Gyr old) in the Small Magellanic Cloud, by combining Hubble Space Telescope (HST) and European Southern Observatory Very Large Telescope MUSE observations. Using HST photometry, we were able to construct 'chromosome maps' and separate subpopulations with different N content, in the red giant branch of each cluster. MUSE spectra of individual stars belonging to each population were combined, resulting in high signal-to-noise spectra representative of each population, which were compared to search for mean differences in Na. We find a mean abundance variation of Delta[Na/Fe] = 0.18 +/- 0.04 dex for NGC 416 and Delta[Na/Fe] = 0.24 +/- 0.05 dex for Lindsay 1. In both clusters, we find that the population that is enhanced in N is also enhanced in Na, which is the same pattern to the one observed in ancient GCs. Furthermore, we detect a bimodal distribution of core-helium-burning red clump (RC) giants in the UV colour-magnitude diagram of NGC 416. A comparison of the stacked MUSE spectra of the two RCs shows the same mean Na abundance difference between the two populations. The results reported in this work are a crucial hint that star clusters of a large age range share the same origin: they are the same types of objects, but only separated in age.
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| 10. |
- Masood, Talha Bin, et al.
(författare)
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An Overview of the Topology ToolKit
- 2021
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Ingår i: Topological Methods in Data Analysis and Visualization VI. - Cham : Springer. - 9783030835002 - 9783030834999 ; , s. 327-342
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Bokkapitel (refereegranskat)abstract
- This software paper gives an overview of the features supported by the Topology ToolKitTopology ToolKit (TTK), which is an  Open-sourceopen-source library for  Topological data analysistopological data analysis (TDA). TTK implements, in a generic and efficient way, a substantial collection of reference algorithms in TDA. Since its initial public release in 2017, both its user and developer bases have grown, resulting in a significant increase in the number of supported features. In contrast to the original paper introducing TTK [40] (which detailed the core algorithms and data structures of TTK), the purpose of this Softwaresoftware paper is to describe the list of features currently supported by TTK, ranging from image segmentation tools to advanced topological analysis of high-dimensional data, with concrete usage examples available on the TTK website [42].
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| 11. |
- Saracino, S., et al.
(författare)
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A black hole detected in the young massive LMC cluster NGC 1850
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 511:2, s. 2914-2924
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Tidskriftsartikel (refereegranskat)abstract
- We report on the detection of a black hole (NGC 1850 BH1) in the ∼100-Myr-old massive cluster NGC 1850 in the Large Magellanic Cloud. It is in a binary system with a main-sequence turn-off star (4.9 ± 0.4 M⊙), which is starting to fill its Roche lobe and is becoming distorted. Using 17 epochs of Very Large Telescope/Multi-Unit Spectroscopic Explorer observations, we detected radial velocity variations exceeding 300 km s−1 associated with the target star, linked to the ellipsoidal variations measured by the fourth phase of the Optical Gravitational Lensing Experiment in the optical bands. Under the assumption of a semidetached system, the simultaneous modelling of radial velocity and light curves constrains the orbital inclination of the binary to 38° ± 2°, resulting in a true mass of the unseen companion of 11.1+2.1−2.4M⊙11.1−2.4+2.1M⊙. This represents the first direct dynamical detection of a black hole in a young massive cluster, opening up the possibility of studying the initial mass function and the early dynamical evolution of such compact objects in high-density environments.
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| 12. |
- Saracino, S., et al.
(författare)
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A closer look at the binary content of NGC 1850
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 526:1, s. 299-322
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Tidskriftsartikel (refereegranskat)abstract
- Studies of young clusters have shown that a large fraction of O-/early B-type stars are in binary systems, where the binary fraction increases with mass. These massive stars are present in clusters of a few Myr, but gradually disappear for older clusters. The lack of detailed studies of intermediate-age clusters has meant that almost no information is available on the multiplicity properties of stars with M < 4M⊙. In this study we present the first characterization of the binary content of NGC 1850, a 100 Myr-old massive star cluster in the Large Magellanic Cloud, relying on a VLT/MUSE multi-epoch spectroscopic campaign. By sampling stars down to M = 2.5 M⊙, we derive a close binary fraction of 24 ± 5 per cent in NGC 1850, in good agreement with the multiplicity frequency predicted for stars of this mass range. We also find a trend with stellar mass (magnitude), with higher mass (brighter) stars having higher binary fractions. We modelled the radial velocity curves of individual binaries using THE JOKER and constrained the orbital properties of 27 systems, ∼17 per cent of all binaries with reliable radial velocities in NGC 1850. This study has brought to light a number of interesting objects, such as four binaries showing mass functions f(M) > 1.25 M⊙. One of these, star #47, has a peculiar spectrum, explainable with the presence of two discs in the system, around the visible star and the dark companion, which is a black hole candidate. These results confirm the importance and urgency of studying the binary content of clusters of any age.
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| 13. |
- Saracino, S., et al.
(författare)
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Leveraging HST with MUSE - I. Sodium abundance variations within the 2-Gyr-old cluster NGC 1978
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 498:3, s. 4472-4480
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Tidskriftsartikel (refereegranskat)abstract
- Nearly all of the well-studied ancient globular clusters (GCs), in the Milky Way and in nearby galaxies, show star-to-star variations in specific elements (e.g. He, C, N, O, Na, and Al), known as 'multiple populations' (MPs). However, MPs are not restricted to ancient clusters, with massive clusters down to similar to 2 Gyr showing signs of chemical variations. This suggests that young and old clusters share the same formation mechanism but most of the work to date on younger clusters has focused on N variations. Initial studies even suggested that younger clusters may not host spreads in other elements beyond N (e.g. Na), calling into question whether these abundance variations share the same origin as in the older GCs. In this work, we combine Hubble Space Telescope (HST) photometry with Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) spectroscopy of a large sample of red giant branch (RGB) stars (338) in the Large Magellanic Cloud cluster NGC 1978, the youngest globular to date with reported MPs in the form of N spreads. By combining the spectra of individual RGB stars into N-normal and N-enhanced samples, based on the 'chromosome map' derived from HST, we search for mean abundance variations. Based on the NaD line, we find a Na difference of Delta[Na/Fe] = 0.07 +/- 0.01 between the populations. While this difference is smaller than typically found in ancient GCs (which may suggest a correlation with age), this result further confirms that the MP phenomenon is the same, regardless of cluster age and host galaxy. As such, these young clusters offer some of the strictest tests for theories on the origin of MPs.
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| 14. |
- Saracino, S., et al.
(författare)
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Updated radial velocities and new constraints on the nature of the unseen source in NGC1850 BH1
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 521:2, s. 3162-3171
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Tidskriftsartikel (refereegranskat)abstract
- A black hole candidate orbiting a luminous star in the Large Magellanic Cloud young cluster NGC 1850 (∼100 Myr) has recently been reported based on radial velocity and light-curve modelling. Subsequently, an alternative explanation has been suggested for the system: a bloated post-mass transfer secondary star (Minitial ∼ 4–5 M⊙ and Mcurrent ∼ 1–2 M⊙) with a more massive, yet luminous companion (the primary). Upon reanalysis of the MUSE spectra, we found that the radial velocity variations originally reported were underestimated (K2, revised = 176 ± 3 km s−1 versus K2, original = 140 ± 3 km s−1) because of the weighting scheme adopted in the full-spectrum fitting analysis. The increased radial velocity semi-amplitude translates into a system mass function larger than previously deduced (frevised = 2.83 M⊙versus foriginal = 1.42 M⊙). By exploiting the spectral disentangling technique, we place an upper limit of 10 per cent of a luminous primary source to the observed optical light in NGC1850 BH1, assuming that the primary and secondary are the only components contributing to the system. Furthermore, by analysing archival near-infrared data, we find clues to the presence of an accretion disc in the system. These constraints support a low-mass post-mass transfer star but do not provide a definitive answer whether the unseen component in NGC1850 BH1 is indeed a black hole. These results predict a scenario where, if a primary luminous source of mass M ≥ 4.7 M⊙ is present in the system (given the inclination and secondary mass constraints), it must be hidden in a optically thick disc to be undetected in the MUSE spectra
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| 15. |
- Sirressi, Mattia, et al.
(författare)
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CLusters in the UV as EngineS (CLUES). I. Survey Presentation and FUV Spectral Analysis of the Stellar Light
- 2022
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 164:5
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Tidskriftsartikel (refereegranskat)abstract
- The CLusters in the Uv as EngineS (CLUES) survey is a Cosmic Origins Spectrograph (COS) campaign aimed at acquiring the 1130–1770 Å rest-frame spectroscopy of very young (<20 Myr) and massive (>104 M⊙) star clusters in galaxies that are part of the Hubble treasury program Legacy ExtraGalactic UV Survey. In this first paper of a series, we describe the CLUES sample consisting of 20 young star clusters and report their physical properties as derived by both multiwavelength photometry and far-UV (FUV) spectroscopy with Hubble Space Telescope. Thanks to the synergy of the two different data sets, we build a coherent picture of the diverse stellar populations found in each region (with sizes of 40–160 pc). We associate the FUV-brightest stellar population to the central targeted star cluster and the other modeled population to the diffuse stars that are included in the COS aperture. We observe better agreement between photometric and spectroscopic ages for star clusters younger than 5 Myr. For clusters older than 5 Myr, photometry and spectroscopy measurements deviate, with the latter producing older ages, due to the degeneracy of photometric models. FUV spectroscopy enables us to better constrain the stellar metallicities, a parameter that optical colors are insensitive to. Finally, the derived E(B − V) are quite similar, with a tendency for FUV spectroscopy to favor solutions with higher extinctions. The recovered masses are in agreement within a factor of 2 for all of the clusters.
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| 16. |
- Sirressi, Mattia, 1995-, et al.
(författare)
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CLusters in the Uv as EngineS (CLUES). II. Subkiloparsec-scale Outflows Driven by Stellar Feedback
- 2024
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Ingår i: Astronomical Journal. - 0004-6256 .- 1538-3881. ; 167:4
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the far-ultraviolet (1130−1770 Å rest frame) spectroscopy of 20 young (<50 Myr) and massive (>104M⊙) star clusters (YSCs) in 11 nearby star-forming galaxies. We probe the interstellar gas intervening along the line of sight, detecting several metal absorption lines of a wide range of ionization potentials, from 6.0 to 77.5 eV. Multiple-component Voigt fits to the absorption lines are used to study the kinematics of the gas. We find that nearly all targets in the sample feature gas outflowing from 30 up to 190 km s−1, often in both the neutral and ionized phases. The outflow velocities correlate with the underlying stellar population properties directly linked to the feedback: the mass of the YSCs, the photon production rate, and the instantaneous mechanical luminosity produced by stellar winds and supernovae. We detect a neutral inflow in four targets, which we interpret as likely not associated with the star cluster but tracing larger-scale gas kinematics. A comparison between the outflows' energy and that produced by the associated young stellar populations suggests an average coupling efficiency of 10% with a broad scatter. Our results extend the relation found in previous works between galactic outflows and the host galaxy star formation rate to smaller scales, pointing toward the key role that clustered star formation and feedback play in regulating galaxy growth.
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| 17. |
- Usher, Christopher, 1985-, et al.
(författare)
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Measuring M31 globular cluster ages and metallicities using both photometry and spectroscopy
- 2024
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Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 528:4, s. 6010-6024
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Tidskriftsartikel (refereegranskat)abstract
- The ages and metallicities of globular clusters play an important role not just in testing models for their formation and evolution but also in understanding the assembly history of their host galaxies. Here, we use a combination of imaging and spectroscopy to measure the ages and metallicities of globular clusters in M31, the closest massive galaxy to our own. We use the strength of the near-infrared calcium triplet spectral feature to provide a relatively age-insensitive prior on the metallicity when fitting stellar population models to the observed photometry. While the age–extinction degeneracy is an issue for globular clusters projected on to the disc of M31, we find generally old ages for globular clusters in the halo of M31 and in its satellite galaxy NGC 205 in line with previous studies. We measure ages for a number of outer halo globular clusters for the first time, finding that globular clusters associated with halo substructure extend to younger ages and higher metallicities than those associated with the smooth halo. This is in line with the expectation that the smooth halo was accreted earlier than the substructured halo.
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| 18. |
- Usher, Christopher, et al.
(författare)
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MUSE narrow field mode observations of the central kinematics of M15
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:2, s. 1680-1687
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Tidskriftsartikel (refereegranskat)abstract
- We present observations of the stellar kinematics of the centre of the core collapsed globular cluster M15 obtained with the MUSE integral field spectrograph on the Very Large Telescope operating in narrow field mode. Thanks to the use of adaptive optics, we obtain a spatial resolution of 0.1 arcsec and are able to reliably measure the radial velocities of 864 stars within 8 arcsec of the centre of M15, thus providing the largest sample of radial velocities ever obtained for the innermost regions of this system. Combined with previous observations of M15 using MUSE in wide field mode and literature data, we find that the central kinematics of M15 are complex with the rotation axis of the core of M15 offset from the rotation axis of the bulk of the cluster. While this complexity has been suggested by previous work, we confirm it at higher significance and in more detail.
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| 19. |
- Usher, Christopher, et al.
(författare)
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Rubin Observatory LSST Stars Milky Way and Local Volume Star Clusters Roadmap
- 2023
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Ingår i: Publications of the Astronomical Society of the Pacific. - 0004-6280 .- 1538-3873. ; 135:1049
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Tidskriftsartikel (refereegranskat)abstract
- The Vera C. Rubin Observatory will undertake the Legacy Survey of Space and Time, providing an unprecedented, volume-limited catalog of star clusters in the Southern Sky, including Galactic and extragalactic star clusters. The Star Clusters subgroup of the Stars, Milky Way and Local Volume Working Group has identified key areas where Rubin Observatory will enable significant progress in star cluster research. This roadmap represents our science cases and preparation for studies of all kinds of star clusters from the Milky Way out to distances of tens of megaparsecs.
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