| 1. |
- Fensch, Jeremy, et al.
(författare)
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Massive star cluster formation and evolution in tidal dwarf galaxies
- 2019
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The formation of globular clusters remains an open debate. Dwarf starburst galaxies are efficient at forming young massiveclusters with similar masses as globular clusters and may hold the key to understanding their formation.Aims.We study star cluster formation in a tidal debris - including the vicinity of three tidal dwarf galaxies - in a massive gas dominatedcollisional ring around NGC 5291. These dwarfs have physical parameters which differ significantly from local starbursting dwarfs.They are gas-rich, highly turbulent, have a gas metallicity already enriched up to half-solar, and are expected to be free of dark matter.The aim is to study massive star cluster formation in this as yet unexplored type of environment.Methods.We use imaging from theHubble Space Telescopeusing broadband filters covering the wavelength range from the near-ultraviolet to the near-infrared. We determine the masses and ages of the cluster candidates by using the spectral energy distribution-fitting code CIGALE, carefully considering age-extinction degeneracy effects on the estimation of the physical parameters.Results.We find that the tidal dwarf galaxies in the ring of NGC 5291 are forming star clusters with an average efficiency of∼40%,comparable to blue compact dwarf galaxies. We also find massive star clusters for which the photometry suggests that they wereformed at the very birth of the tidal dwarf galaxies and have survived for several hundred million years. Therefore our study showsthat extended tidal dwarf galaxies and compact clusters may be formed simultaneously. In the specific case observed here, the youngstar clusters are not massive enough to survive for a Hubble time. However one may speculate that similar objects at higher redshift,with higher star formation rate, might form some of the long lived globular clusters.Key words.galaxies: dwarf, galaxies: star clusters: general, galaxies: irregular, galaxies: star formation, galaxies: stellar content,galaxies: interactions
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| 2. |
- Fensch, Jeremy, et al.
(författare)
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Massive star cluster formation and evolution in tidal dwarf galaxies
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 628
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Tidskriftsartikel (refereegranskat)abstract
- Context. The formation of globular clusters remains an open debate. Dwarf starburst galaxies are efficient at forming young massive clusters with similar masses as globular clusters and may hold the key to understanding their formation. Aims. We study star cluster formation in a tidal debris, including the vicinity of three tidal dwarf galaxies, in a massive gas-dominated collisional ring around NGC 5291. These dwarfs have physical parameters that differ significantly from local starbursting dwarfs. They are gas rich, highly turbulent, their gas metallicity is already enriched up to half solar values, and they are expected to be free of dark matter. The aim is to study massive star cluster formation in this as yet unexplored type of environment. Methods. We used imaging from the Hubble Space Telescope using broadband filters that cover the wavelength range from the near-ultraviolet to the near-infrared. We determined the masses and ages of the cluster candidates by using the spectral energy distribution-fitting code CIGALE. We considered age-extinction degeneracy effects on the estimation of the physical parameters. Results. We find that the tidal dwarf galaxies in the ring of NGC 5291 are forming star clusters with an average efficiency of ∼40%, which is similar to blue compact dwarf galaxies. We also find massive star clusters for which the photometry suggests that they were formed at the very birth of the tidal dwarf galaxies. These clusters have survived for several hundred million years. Therefore our study shows that extended tidal dwarf galaxies and compact clusters may be formed simultaneously. In the specific case observed here, the young star clusters are not massive enough to survive for a Hubble time. However, it may be speculated that similar objects at higher redshift, with a higher star formation rate, might form some of the long-lived globular clusters.
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| 3. |
- Grisdale, Kearn, et al.
(författare)
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On the observed diversity of star formation efficiencies in Giant Molecular Clouds
- 2019
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:4, s. 5482-5491
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Tidskriftsartikel (refereegranskat)abstract
- Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) of the order of eff ~ 1 per cent with dispersions of ~0.5dex. The origin of this scatter in eff is still debated and difficult to reproduce with analytical models.We track the formation, evolution and destruction of GMCs in a hydrodynamical simulation of a Milky Way-like galaxy and by deriving cloud properties in an observationally motivated way, we measure the distribution of star formation efficiencies which are in excellent agreement with observations. We find no significant link between eff and any measured global property of GMCs (e.g. gas mass, velocity dispersion). Instead, a wide range of efficiencies exist in the entire parameter space. From the cloud evolutionary tracks, we find that each cloud follows a unique evolutionary path which gives rise to a wide diversity in all properties.We argue that it is this diversity in cloud properties, above everything else, that results in the dispersion of eff .
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| 4. |
- Ohlin, Loke, et al.
(författare)
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Supernovae feedback propagation: the role of turbulence
- 2019
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 485:3, s. 3887-3894
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Tidskriftsartikel (refereegranskat)abstract
- Modelling the propagation of supernova (SN) bubbles, in terms of energy, momentum, and spatial extent, is critical for simulations of galaxy evolution which do not capture these scales. To date, small-scale models of SN feedback predict that the evolution of above-mentioned quantities can be solely parametrized by average quantities of the surrounding gas, such as density. However, most of these studies neglect the turbulent motions of this medium. In this paper, we study the propagation and evolution of SNe in turbulent environments. We confirm that the time evolution of injected energy and momentum can be characterized by the average density. However, the details of the density structure of the interstellar medium play a crucial role in the spatial extent of the bubble, even at a given average density. We demonstrate that spherically symmetric models of SN bubbles do not model well their spatial extent, and therefore cannot not be used to design sub-grid models of SNe feedback at galactic and cosmological scales.
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| 5. |
- Pehlivan Rhodin, Nils Henrik, et al.
(författare)
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The nature of damped HI absorbers probed by cosmological simulations: satellite accretion and outflows
- 2019
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; , s. 3634-3634
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Tidskriftsartikel (refereegranskat)abstract
- We use cosmological hydrodynamic zoom simulations to study the neutral gas distributionin and around galaxies that gives rise to high column density HILyαabsorption (dampedLyαsystems (DLAs) and sub-DLAs) in background quasar spectra. Such simulations oftensacrifice numerical resolution for volume that affects the lower density galaxy halo gas,and simulations have difficulties reproducing the span of projected separations (b) betweenabsorbing clouds and their hosts. Our simulations produce (sub-)DLAs over the entire probedparameter space (b50 kpc and metallicity−4[M/H]0.5) at all redshifts (z∼0.4−3.0),enclosing spectroscopically confirmed absorber-galaxy pairs. Recovering (sub-)DLAs atb20−30 kpc from a massive host galaxy requires high numerical resolution and efficientfeedback, and we show that these lines-of-sight are associated with dwarf satellites in the mainhalo, stripped metal-rich gas, and outflows. HIdisc- and halo gas significantly contributesto (sub-)DLAs around galaxies. At large redshifts the halo plays an increasingly importantrole, while at 0.4
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| 6. |
- Renaud, Florent
(författare)
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3 things they don't tell you about star clusters
- 2019
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213. ; 14:351, s. 40-46
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Tidskriftsartikel (refereegranskat)abstract
- Dense stellar systems in general and star clusters in particular have recently regained the interest of the extragalactic and even cosmology communities, due to the role they could play as actors and probes of re-ionization, galactic archeology and the dark matter content of galaxies, among many others. In the era of the exploitation and the preparation of large stellar surveys (Gaia, APOGEE, 4MOST, WEAVE), of the detection of gravitational waves mostly originating from dense regions like the cores of clusters (Ligo, LISA), and in an always more holistic view of galaxy formation (HARMONI, Euclid, LSST†), a complete theory on the formation and evolution of clusters is needed to interpret the on-going and forthcoming data avalanche. In this context, the community carries an effort to model the aspects of star cluster formation and evolution in galactic and even cosmological context. However, it is not always easy to understand the caveats and the shortcuts taken in theories and simulations, and their implications on the conclusions drawn. I take the opportunity of this document to highlight three of these topics and discuss why some shortcuts taken by the community are or could be misleading.
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| 7. |
- Renaud, Florent, et al.
(författare)
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Three regimes of CO emission in galaxy mergers
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 621
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Tidskriftsartikel (refereegranskat)abstract
- The conversion factor αCO from the observable CO(1-0) luminosity to the mass of molecular gas is known to vary between isolated galaxies and some mergers, but the underlying reasons are not clearly understood. Thus, the value(s) of αCO that are to be adopted remain highly uncertain. To provide better constraints, we applied the large velocity gradient method to a series of hydrodynamical simulations of galaxies and derived the evolution of αCO. We report significant variations of αCO, and identify three distinct regimes: Disk galaxies, starbursts, and post-burst phases. We show that estimating the star formation rate over 20Myr smoothes out some of these differences, but still maintains a distinction between disks and starbursts. We find a tighter correlation of αCO with the gas depletion time than with star formation rate, but deviations are induced by the transitions to and from the starburst episodes. We conclude that αCO fluctuates because of both feedback energy and velocity dispersion. Identifying the phase of an interaction by classical means (e.g., morphology or luminosity) could then help to select the relevant conversion factor that is to be used and to obtain more accurate estimates of the molecular masses of galaxies.
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| 8. |
- Sanchez, Guillaume, et al.
(författare)
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Post-spreading deformation and associated magmatism along the Iberia-Morocco Atlantic margins : Insight from submarine volcanoes of the Tore-Madeira Rise
- 2019
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Ingår i: Marine Geology. - 0025-3227 .- 1872-6151. ; 407, s. 76-93
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Tidskriftsartikel (refereegranskat)abstract
- A new high-resolution bathymetric map combined with a regional Digital Elevation Model (DEM) analysis reveal the modalities of occurrence and emplacement of post-spreading magmatism along the NNE-SSW oriented, 1000 km long Tore-Madeira Rise (TMR) as well as its relationship with the activity of major fault systems including the Estremadura Fault System (ESF) and the Azores-Gibraltar Fracture Zone (AGFZ). Morphological and structural analysis of the bathymetric map were performed to map volcanic features such as eruptive cones, vents and fissures together with faults along the TMR. The new bathymetric map shows that the main NNW-SSE seamount alignment is formed by three structurally distinct volcanic massifs, the Tore, the Josephine and the Southern Volcanic Groups. The majority of the volcanoes of each group emplaced within or along specific portion of pre-existing faults (ESF and AGFZ) including splay fault, releasing bend, fault tips and interaction zones between different segments. Magmas were channelled into sub-vertical pre-existing lithospheric faults that acted as preferential pathways for the vertical magma ascent. Migration and final eruption of magma are controlled by the local stress variation induced by complex fault geometries, change in plate kinematics as well as strong shear zone anisotropy as suggested by the emplacement within localised areas of transtension. We conclude that post-spreading magma emplacement in the southern part of the Iberia margin was related to the development of a transtensional plate boundary between the Iberian and African Plate during the Late Cretaceous. More generally, our findings emphasize that the distribution of volcanism as the expression of the interaction between shallow plate tectonic and mantle processes should be included in plate kinematic reconstruction. This study also demonstrates that the accurate mapping of oceanic seafloor is pivotal to better understand tectono-magmatic evolution of volcanic seamount chains and geological processes in oceanic domains.
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