| 1. |
- Agertz, Oscar, et al.
(author)
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Vintergatan - i. The origins of chemically, kinematically, and structurally distinct discs in a simulated milky way-mass galaxy
- 2021
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:4, s. 5826-5845
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Journal article (peer-reviewed)abstract
- Spectroscopic surveys of the Milky Way's stars have revealed spatial, chemical, and kinematical structures that encode its history. In this work, we study their origins using a cosmological zoom simulation, VINTERGATAN, of a MilkyWay-mass disc galaxy. We find that in connection to the last major merger at z ∼ 1.5, cosmological accretion leads to the rapid formation of an outer, metal-poor, low-[α/Fe] gas disc around the inner, metal-rich galaxy containing the old high-[α/Fe] stars. This event leads to a bimodality in [α/Fe] over a range of [Fe/H]. A detailed analysis of how the galaxy evolves since z ∼ 1 is presented. We demonstrate the way in which inside-out growth shapes the radial surface density and metallicity profile and how radial migration preferentially relocates stars from the inner disc to the outer disc. Secular disc heating is found to give rise to increasing velocity dispersions and scale heights with stellar age, which together with disc flaring explains several trends observed in the MilkyWay, including shallower radial [Fe/H] profiles above the mid-plane.We show how the galaxy formation scenario imprints non-trivial mappings between structural associations (i.e. thick and thin discs), velocity dispersions, α-enhancements, and ages of stars; e.g. the most metal-poor stars in the low-[α/Fe] sequence are found to have a scale height comparable to old high-[α/Fe] stars. Finally, we illustrate how at low spatial resolution, comparable to the thickness of the galaxy, the proposed pathway to distinct sequences in [α/Fe]-[Fe/H] cannot be captured.
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| 2. |
- Andersson, Eric P., et al.
(author)
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INFERNO : Galactic winds in dwarf galaxies with star-by-star simulations including runaway stars
- 2023
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 521:2, s. 2196-2214
-
Journal article (peer-reviewed)abstract
- The formation and evolution of galaxies have proved sensitive to the inclusion of stellar feedback, which is therefore crucial to any successful galaxy model. We present INFERNO, a new model for hydrodynamic simulations of galaxies, which incorporates resolved stellar objects with star-by-star calculations of when and where the injection of enriched material, momentum, and energy takes place. INFERNO treats early stellar kinematics to include phenomena such as walkaway and runaway stars. We employ this innovative model on simulations of a dwarf galaxy and demonstrate that our physically motivated stellar feedback model can drive vigorous galactic winds. This is quantified by mass and metal loading factors in the range of 10–100, and an energy loading factor close to unity. Outflows are established close to the disc, are highly multiphase, spanning almost 8 orders of magnitude in temperature, and with a clear dichotomy between mass ejected in cold, slow-moving (T ≲ 5 × 104 K, v < 100 km s-1) gas and energy ejected in hot, fast-moving (T > 106 K, v > 100 km s-1) gas. In contrast to massive disc galaxies, we find a surprisingly weak impact of the early stellar kinematics, with runaway stars having little to no effect on our results, despite exploding in diffuse gas outside the dense star-forming gas, as well as outside the galactic disc entirely. We demonstrate that this weak impact in dwarf galaxies stems from a combination of strong feedback and a porous interstellar medium, which obscure any unique signatures that runaway stars provide.
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| 3. |
- Andersson, Eric P., et al.
(author)
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Pre-supernova feedback sets the star cluster mass function to a power law and reduces the cluster formation efficiency
- 2024
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In: Astronomy and Astrophysics. - 0004-6361. ; 681
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Journal article (peer-reviewed)abstract
- Context. The star cluster initial mass function is observed to have an inverse power law exponent around 2, yet there is no consensus on what determines this distribution, and why some variation is observed in different galaxies. Furthermore, the cluster formation efficiency (CFE) covers a range of values, particularly when considering different environments. These clusters are often used to empirically constrain star formation and as fundamental units for stellar feedback models. Detailed galaxy models must therefore accurately capture the basic properties of observed clusters to be considered predictive. Aims. We study how feedback mechanisms acting on different timescales and with different energy budgets affect the star cluster mass function and CFE. Methods. We use hydrodynamical simulations of a dwarf galaxy as a laboratory to study star cluster formation. We test different combinations of stellar feedback mechanisms, including stellar winds, ionizing radiation, and supernovae (SNe). Results. Each feedback mechanism affects the CFE and cluster mass function. Increasing the feedback budget by combining the different types of feedback decreases the CFE by reducing the number of massive clusters. Ionizing radiation is found to be especially influential. This effect depends on the timing of feedback initiation, as shown by comparing early and late feedback. Early feedback occurs from ionizing radiation and stellar winds with onset immediately after a massive star is formed. Late feedback occurs when energy injection only starts after the main-sequence lifetime of the most massive SN progenitor, a timing that is further influenced by the choice of the most massive SN progenitor. Late feedback alone results in a broad, flat mass function, approaching a log-normal shape in the complete absence of feedback. Early feedback, on the other hand, produces a power-law cluster mass function with lower CFE, albeit with a steeper slope than that usually observed.
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| 4. |
- Andersson, Eric P., et al.
(author)
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Runaway stars masquerading as star formation in galactic outskirts
- 2021
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In: Monthly Notices of the Royal Astronomical Society: Letters. - : Oxford University Press (OUP). - 1745-3925 .- 1745-3933. ; 502:1, s. 29-34
-
Journal article (peer-reviewed)abstract
- In the outskirts of nearby spiral galaxies, star formation is observed in extremely low gas surface densities. Star formation in these regions, where the interstellar medium is dominated by diffuse atomic hydrogen, is difficult to explain with classic star formation theories. In this letter, we introduce runaway stars as an explanation for this observation. Runaway stars, produced by collisional dynamics in young stellar clusters, can travel kiloparsecs during their main-sequence lifetime. Using galactic-scale hydrodynamic simulations including a treatment of individual stars, we demonstrate that this mechanism enables the ejection of young massive stars into environments where the gas is not dense enough to trigger star formation. This results in the appearance of star formation in regions where it ought to be impossible. We conclude that runaway stars are a contributing, if not dominant, factor to the observations of star formation in the outskirts of spiral galaxies.
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| 5. |
- Bílek, Michal, et al.
(author)
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The galactic acceleration scale is imprinted on globular cluster systems of early-type galaxies of most masses and on red and blue globular cluster subpopulations
- 2024
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In: Astronomy and Astrophysics. - 0004-6361. ; 682
-
Journal article (peer-reviewed)abstract
- Context. Globular clusters (GCs) carry information about the formation histories and gravitational fields of their host galaxies. It was found before that the radial profiles of the volume number density of GCs in GC systems (GCSs) follow broken power laws, while the breaks occur approximately at the a0 radii. These are the radii at which the gravitational fields of the galaxies equal the galactic acceleration scale a0 = 1.2 × 10-10 ms-2 known from the radial acceleration relation or the MOND theory of modified dynamics. Aims. Our main goals here are to explore whether the above results hold true for galaxies of a wider mass range and for the red and blue GC subpopulations. Methods. We exploited catalogs of photometric GC candidates in the Fornax galaxy cluster based on ground and space observations and a new catalog of spectroscopic GCs of NGC1399, the central galaxy of the cluster. For every galaxy, we obtained the parameters of the broken power-law density by fitting the on-sky distribution of the GC candidates, while allowing for a constant density of contaminants. The logarithmic stellar masses of our galaxy sample span 8.0-11.4 M⊙. Results. All investigated GCSs with a suficient number of members show broken power-law density profiles. This holds true for the total GC population and the blue and red subpopulations. The inner and outer slopes and the break radii agree well for the different GC populations. The break radii agree with the a0 radii typically within a factor of two for all GC color subpopulations. The outer slopes correlate better with the a0 radii than with the galactic stellar masses. The break radii of NGC1399 vary in azimuth, such that they are greater toward and against the direction to NGC1404, which tidally interacts with NGC1399.
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| 6. |
- Della Bruna, Lorenza, et al.
(author)
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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
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
-
Journal article (peer-reviewed)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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| 7. |
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| 8. |
- Della Bruna, Lorenza, et al.
(author)
-
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
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
-
Journal article (peer-reviewed)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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| 9. |
- Duc, Pierre-Alain, et al.
(author)
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Revisiting Stephan's Quintet with deep optical images
- 2018
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In: Monthly Notices of the Royal Astronomical Society: Letters. - : Oxford University Press (OUP). - 1745-3925 .- 1745-3933. ; 475:1, s. 40-44
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Journal article (peer-reviewed)
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| 10. |
- Ejdetjärn, Timmy, et al.
(author)
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From giant clumps to clouds - III. The connection between star formation and turbulence in the ISM
- 2022
-
In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 514:1, s. 480-496
-
Journal article (peer-reviewed)abstract
- Supersonic gas turbulence is a ubiquitous property of the interstellar medium. The level of turbulence, quantified by the gas velocity dispersion (sigma(g)), is observed to increase with the star formation rate (SFR) of a galaxy, but it is yet not established whether this trend is driven by stellar feedback or gravitational instabilities. In this work, we carry out hydrodynamical simulations of entire disc galaxies, with different gas fractions, to understand the origins of the SFR-sigma(g) relation. We show that disc galaxies reach the same levels of turbulence regardless of the presence of stellar feedback processes, and argue that this is an outcome of the way disc galaxies regulate their gravitational stability. The simulations match the SFR-sigma(g) relation up to SFRs of the order of tens of M-circle dot yr(-1) and sigma(g) similar to 50 km s(-1) in neutral hydrogen and molecular gas, but fail to reach the very large values (> 100 km s(-1)) reported in the literature for rapidly star-forming galaxies. We demonstrate that such high values of sigma(g) can be explained by ( 1) insufficient beam smearing corrections in observations and (2) stellar feedback being coupled to the ionized gas phase traced by recombination lines. Given that the observed SFR-sigma(g) relation is composed of highly heterogeneous data, with sigma(g) at high SFRs almost exclusively being derived from H alpha observations of high-redshift galaxies with complex morphologies, we caution against analytical models that attempt to explain the SFR-sigma(g) relation without accounting for these effects.
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| 11. |
- Ejdetjärn, Timmy
(author)
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The origin of the Hα line profiles in simulated disc galaxies
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Journal article (other academic/artistic)abstract
- Observations of ionised Hα gas in disc galaxies with high star formation rates have ubiquitous and significant line broadening with widths σHα≳50−100 km s−1. To understand whether this broadening reflects gas turbulence within the interstellar medium (ISM) of galactic discs, or arises from off-the-plane emission in mass-loaded galactic winds, we perform radiation hydrodynamic (RHD) simulations of isolated Milky Way-mass disc galaxies in a gas-poor (low-redshift) and gas rich (high-redshift) condition and create mock Hα emission line profiles. We find that the vast majority of the Hα emission is confined within the ISM, with extraplanar gas contributing mainly to the extended profile wings. This substantiates the \Halpha emission line as a tracer of mid-plane disc dynamics. We investigate the relative contribution of diffuse and dense Hα emitting gas, corresponding to DIG (ρ≲0.1 cm−3, T∼8 000 K) and HII regions (ρ≳10 cm−3, T∼10 000 K), respectively, and find that DIG contributes ≲10% of the total LHα. However, the DIG can reach upwards of σHα∼60−80 km s−1 while the HII regions are much less turbulent σHα∼10−40 km s−1. This implies that the σHα observed using the full Hα emission line is dependent on the relative Hα contribution from DIG/HII regions and a larger fDIG would shift σHα to higher values. Finally, we show that σHα evolves, in both the DIG and HII regions, with the galaxy gas fraction. Our high-redshift equivalent galaxy is roughly twice as turbulent, except for in the DIG which has a more shallow evolution.
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| 12. |
- Elie, Margaux, et al.
(author)
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Designing NHC-Copper(I) Dipyridylamine Complexes for Blue Light-Emitting Electrochemical Cells
- 2016
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 8:23, s. 14678-14691
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Journal article (peer-reviewed)abstract
- This study presents the influence of various substituents on the photophysical features of heteroleptic copper(I) complexes bearing both N-heterocyclic carbene (NHC) and dipyridylamine (dpa = dipyridylamine skeleton corresponding to ligand L1) ligands. The luminescent properties have been compared to our recently reported archetypal blue emitting [Cu(IPr)(dpa)][PF6] complex. The choice of the substituents on both ligands has been guided to explore the effect of the electron donor/acceptor and "push-pull" on the emission wavelengths and photoluminescence quantum yields. A selection of the best candidates in terms of their photophysical features were applied for developing the first blue light emitting electrochemical cells (LECs) based on copper(I) complexes. The device analysis suggests that the main concern is the moderate redox stability of the complexes under high applied driving currents, leading to devices with moderate stabilities pointing to a proof-of-concept for further development. Nevertheless, under low applied driving currents the blue emission is stable, showing performance levels competitive to those reported for blue LECs baged on iridium(III) complexes. Overall, this work provides valuable guidelines to tackle the design of enhanced NHC copper complexes for lighting applications in the near future.
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| 13. |
- Elie, Margaux, et al.
(author)
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Role of the Bridging Group in Bis-Pyridyl Ligands : Enhancing Both the Photo- and Electroluminescent Features of Cationic (IPr) Cu-I Complexes
- 2017
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In: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 23:64, s. 16328-16337
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Journal article (peer-reviewed)abstract
- We report on the benefits of changing the bridging group X of bis-pyridyl ligands, that is, Py-X-Py where X is NH, CH2, C(CH3)(2), or PPh, on the photo-and electroluminescent properties of a new family of luminescent cationic H-heterocyclic carbene (NHC) copper(I) complexes. A joint experimental and theoretical study demonstrates that the bridging group affects the molecular conformation from a planar-like structure (X is NH and CH2) to a boat-like structure (X is C(CH3)(2) and PPh), leading to i) four-fold enhancement of the photoluminescence quantum yield (phi(em)) without affecting the thermally activated delayed fluorescence mechanism, and ii) one order of magnitude reduction of the ionic conductivity (sigma) of thin films. This leads to an overall enhancement of the device efficacy and luminance owing to the increased phi(em) and the use of low applied driving currents.
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| 14. |
- Fensch, Jeremy, et al.
(author)
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Massive star cluster formation and evolution in tidal dwarf galaxies
- 2019
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Other publication (other academic/artistic)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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| 15. |
- Fensch, Jeremy, et al.
(author)
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Massive star cluster formation and evolution in tidal dwarf galaxies
- 2019
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 628
-
Journal article (peer-reviewed)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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| 16. |
- Grisdale, Kearn, et al.
(author)
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On the observed diversity of star formation efficiencies in Giant Molecular Clouds
- 2019
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:4, s. 5482-5491
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Journal article (peer-reviewed)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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| 17. |
- Grisdale, Kearn, et al.
(author)
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Physical properties and scaling relations of molecular clouds: the effect of stellar feedback
- 2018
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 479:3, s. 3167-3180
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Journal article (peer-reviewed)abstract
- Using hydrodynamical simulations of entire galactic discs similar to the Milky Way (MW), reaching 4.6{ pc} resolution, we study the origins of observed physical properties of giant molecular clouds (GMCs). We find that efficient stellar feedback is a necessary ingredient in order to develop a realistic interstellar medium, leading to molecular cloud masses, sizes, velocity dispersions, and virial parameters in excellent agreement with MW observations. GMC scaling relations observed in the MW, such as the mass-size (M-R), velocity dispersion-size (σ-R), and the σ-RΣ relations, are reproduced in a feedback-driven ISM when observed in projection, with M∝R2.3 and σ∝R0.56. When analysed in 3D, GMC scaling relations steepen significantly, indicating potential limitations of our understanding of molecular cloud 3D structure from observations. Furthermore, we demonstrate how a GMC population's underlying distribution of virial parameters can strongly influence the scatter in derived scaling relations. Finally, we show that GMCs with nearly identical global properties exist in different evolutionary stages, where a majority of clouds being either gravitationally bound or expanding, but with a significant fraction being compressed by external ISM pressure, at all times.
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| 18. |
- Grisdale, Kearn, et al.
(author)
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The impact of stellar feedback on the density and velocity structure of the interstellar medium
- 2017
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 466:1, s. 1093-1110
-
Journal article (peer-reviewed)abstract
- We study the impact of stellar feedback in shaping the density and velocity structure of neutral hydrogen (H I) in disc galaxies. For our analysis, we carry out ~4.6 pc resolution N-body+adaptive mesh refinement hydrodynamic simulations of isolated galaxies, set up to mimic a Milky Way and a Large and Small Magellanic Cloud. We quantify the density and velocity structure of the interstellar medium using power spectra and compare the simulated galaxies to observedHI in local spiral galaxies from THINGS (TheHI Nearby Galaxy Survey). Our models with stellar feedback give an excellent match to the observed THINGS HI density power spectra. We find that kinetic energy power spectra in feedback-regulated galaxies, regardless of galaxy mass and size, show scalings in excellent agreement with supersonic turbulence (E(k) ∝ k-2) on scales below the thickness of the HI layer. We show that feedback influences the gas density field, and drives gas turbulence, up to large (kpc) scales. This is in stark contrast to density fields generated by large-scale gravity-only driven turbulence. We conclude that the neutral gas content of galaxies carries signatures of stellar feedback on all scales.
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| 19. |
- Guillard, Nicolas, et al.
(author)
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The impact of radiation feedback on the assembly of star clusters in a galactic context
- 2018
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In: Monthly Notices of the Royal Astronomical Society. - 0035-8711. ; 477:4, s. 5001-5010
-
Journal article (peer-reviewed)abstract
- Massive star clusters are observed in galaxies spanning a broad range of luminosities and types, and are assumed to form in dense gas-rich environments. Using a parsec-resolution hydrodynamical simulation of an isolated gas-rich low-mass galaxy, we discuss here the non-linear effects of stellar feedback on the properties of star clusters with a focus on the progenitors of nuclear clusters. Our simulation shows two categories of star clusters: those for which feedback expels gas leftovers associated with their formation sites, and those, in a denser environment, around which feedback fails to totally clear the gas. We confirm that radiation feedback (photoionization and radiative pressure) plays a more important role than Type II supernovae in destroying dense gas structures, and in altering or quenching the subsequent cluster formation. Radiation feedback also disturbs the cluster mass growth, by increasing the internal energy of the gas component to the point at which radiation pressure overcomes the cluster gravity. We discuss how these effects may depend on the local properties of the interstellarmedium, and also on the details of the subgrid recipes,which can affect the available cluster gas reservoirs, the evolution of potential nuclear cluster progenitors, and the overall galaxy morphology.
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| 20. |
- Ibata, Rodrigo, et al.
(author)
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Charting the Galactic Acceleration Field. I. A Search for Stellar Streams with Gaia DR2 and EDR3 with Follow-up from ESPaDOnS and UVES
- 2021
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In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 914:2
-
Journal article (peer-reviewed)abstract
- We present maps of the stellar streams detected in the Gaia Data Release 2 (DR2) and Early Data Release 3 (EDR3) catalogs using the STREAMFINDER algorithm. We also report the spectroscopic follow-up of the brighter DR2 stream members obtained with the high-resolution CFHT/ESPaDOnS and VLT/UVES spectrographs as well as with the medium-resolution NTT/EFOSC2 spectrograph. Two new stellar streams that do not have a clear progenitor are detected in DR2 (named Hrid and Gunnthra), and seven are detected in EDR3 (named Gaia-6 to Gaia-12). Several candidate streams are also identified. The software also finds very long tidal tails associated with the 15 globular clusters: NGC 288, NGC 1261, NGC 1851, NGC 2298, NGC 2808, NGC 3201, M68, omega Cen, NGC 5466, Palomar 5, M5, NGC 6101, M92, NGC 6397, and NGC 7089. These stellar streams will be used in subsequent contributions in this series to chart the properties of the Galactic acceleration field on similar to 100 pc to similar to 100 kpc scales.
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| 21. |
- Joshi, Gandhali D., et al.
(author)
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VINTERGATAN-GM : How do mergers affect the satellite populations of MW-like galaxies?
- 2024
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In: Monthly Notices of the Royal Astronomical Society. - 0035-8711. ; 528:2, s. 2346-2357
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Journal article (peer-reviewed)abstract
- We investigate the impact of a galaxy’s merger history on its system of satellites using the new VINTERGATAN-GM suite of zoom-in hydrodynamical simulations of Milky Way-mass systems. The suite simulates five realizations of the same halo with targeted ‘genetic modifications’ of a z ≈ 2 merger, but resulting in the same halo mass at z = 0. We find that differences in the satellite stellar mass functions last for 2.25−4.25 Gyr after the z ≈ 2 merger; specifically, the haloes that have undergone smaller mergers host up to 60 per cent more satellites than those of the larger merger scenarios. However, by z = 0 these differences in the satellite stellar mass functions have been erased. The differences in satellite numbers seen soon after the mergers are driven by several factors, including the timings of significant mergers (with M200c mass ratios >1:30 and bringing in M∗ ≥ 108 M☉ at infall), the masses and satellite populations of the central and merging systems, and the subsequent extended history of smaller mergers. The results persist when measured at fixed central stellar mass rather than fixed time, implying that a host’s recent merger history can be a significant source of scatter when reconstructing its dynamical properties from its satellite population.
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| 22. |
- Kraljic, Katarina, et al.
(author)
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Emergence and cosmic evolution of the Kennicutt- Schmidt relation driven by interstellar turbulence
- 2024
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In: Astronomy and Astrophysics. - 0004-6361. ; 682
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Journal article (peer-reviewed)abstract
- The scaling relations between the gas content and star formation rate of galaxies provide useful insights into the processes governing their formation and evolution. We investigated the emergence and the physical drivers of the global Kennicutt-Schmidt (KS) relation at 0:25 ≤ z ≤ 4 in the cosmological hydrodynamic simulation NewHorizon, capturing the evolution of a few hundred galaxies with a resolution down to 34 pc. The details of this relation vary strongly with the stellar mass of galaxies and the redshift. A power-law relation ΣSFR / Σa gas with a ≈ 1:4, like that found empirically, emerges at z ≈ 2..3 for the more massive half of the galaxy population. However, no such convergence is found in the lower-mass galaxies, for which the relation gets shallower with decreasing redshift. At galactic scales, the star formation activity correlates with the level of turbulence of the interstellar medium, quantified by the Mach number, rather than with the gas fraction (neutral or molecular), confirming the conclusions found in previous works. With decreasing redshift, the number of outliers with short depletion times diminishes, reducing the scatter of the KS relation, while the overall population of galaxies shifts toward low densities. Our results, from parsec-scale star formation models calibrated with local Universe physics, demonstrate that the cosmological evolution of the environmental (e.g., mergers) and internal conditions (e.g., gas fractions) conspire to shape the KS relation. This is an illustration of how the interplay of global and local processes leaves a detectable imprint on galactic-scale observables and scaling relations.
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| 23. |
- Marion, Ronan, et al.
(author)
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NHC Copper(I) Complexes Bearing Dipyridylamine Ligands: Synthesis, Structural, and Photoluminescent Studies
- 2014
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In: Inorganic Chemistry. - : American Chemical Society. - 0020-1669 .- 1520-510X. ; 53:17, s. 9181-9191
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Journal article (peer-reviewed)abstract
- We describe the synthesis of new cationic tricoordinated copper complexes bearing bidentate pyridine-type ligands and N-heterocyclic carbene as ancillary ligands. These cationic copper complexes were fully characterized by NMR, electrochemistry, X-ray analysis, and photophysical studies in different environments. Density functional theory calculations were also undertaken to rationalize the assignment of the electronic structure and the photophysical properties. These tricoordinated cationic copper complexes possess a stabilizing CH-pi interaction leading to high stability in both solid and liquid states. In addition, these copper complexes, bearing dipyridylamine ligands having a central nitrogen atom as potential anchoring point, exhibit very interesting luminescent properties that render them potential candidates for organic light-emitting diode applications.
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| 24. |
- Ohlin, Loke, et al.
(author)
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Supernovae feedback propagation: the role of turbulence
- 2019
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 485:3, s. 3887-3894
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Journal article (peer-reviewed)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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| 25. |
- Pehlivan Rhodin, Nils Henrik, et al.
(author)
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The nature of damped HI absorbers probed by cosmological simulations: satellite accretion and outflows
- 2019
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; , s. 3634-3634
-
Journal article (peer-reviewed)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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