| 1. |
- Andersson, Eric P., et al.
(författare)
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INFERNO : Galactic winds in dwarf galaxies with star-by-star simulations including runaway stars
- 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. 2196-2214
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Petersson, Jonathan, et al.
(författare)
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From starburst to quenching : merger-driven evolution of the star formation regimes in a shell galaxy
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 518:3, s. 3261-3273
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Tidskriftsartikel (refereegranskat)abstract
- Shell galaxies make a class of tidally distorted galaxies, characterized by wide concentric arc(s), extending out to large galactocentric distances with sharp outer edges. Recent observations of young massive star clusters in the prominent outer shell of NGC 474 suggest that such systems host extreme conditions of star formation. In this paper, we present a hydrodynamic simulation of a galaxy merger and its transformation into a shell galaxy. We analyse how the star formation activity evolves with time, location-wise within the system, and what are the physical conditions for star formation. During the interaction, an excess of dense gas appears, triggering a starburst, i.e. an enhanced star formation rate and a reduced depletion time. Star formation coincides with regions of high-molecular gas fraction, such as the galactic nucleus, spiral arms, and occasionally the tidal debris during the early stages of the merger. Tidal interactions scatter stars into a stellar spheroid, while the gas cools down and reforms a disc. The morphological transformation after coalescence stabilizes the gas and thus quenches star formation, without the need for feedback from an active galactic nucleus. This evolution shows similarities with a compaction scenario for compact quenched spheroids at high-redshift, yet without a long red nugget phase. Shells appear after coalescence, during the quenched phase, implying that they do not host the conditions necessary for in situ star formation. The results suggest that shell-forming mergers might be part of the process of turning blue late-type galaxies into red and dead early-types.
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| 3. |
- Rey, Martin P., et al.
(författare)
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VINTERGATAN-GM : The cosmological imprints of early mergers on Milky-Way-mass galaxies
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 521:1, s. 995-1012
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Tidskriftsartikel (refereegranskat)abstract
- We present a new suite of cosmological zoom-in hydrodynamical (≈ 20 pc spatial resolution) simulations of Milky-Way mass galaxies to study how a varying mass ratio for a Gaia-Sausage-Enceladus (GSE) progenitor impacts the z = 0 chemodynamics of halo stars. Using the genetic modification approach, we create five cosmological histories for a Milky-Way-mass dark matter halo (M200 ≈ 1012 M☉), incrementally increasing the stellar mass ratio of a z ≈ 2 merger from 1:25 to 1:2, while fixing the galaxy’s final dynamical, stellar mass, and large-scale environment. We find markedly different morphologies at z = 0 following this change in early history, with a growing merger resulting in increasingly compact and bulge-dominated galaxies. Despite this structural diversity, all galaxies show a radially biased population of inner halo stars like the Milky-Way’s GSE which, surprisingly, has a similar magnitude, age, [Fe/H], and [α/Fe] distribution whether the z ≈ 2 merger is more minor or major. This arises because a smaller ex-situ population at z ≈ 2 is compensated by a larger population formed in an earlier merger-driven starburst whose contribution to the GES can grow dynamically over time, and with both populations strongly overlapping in the [Fe/H] − [α/Fe] plane. Our study demonstrates that multiple high-redshift histories can lead to similar z = 0 chemodynamical features in the halo, highlighting the need for additional constraints to distinguish them, and the importance of considering the full spectrum of progenitors when interpreting z = 0 data to reconstruct our Galaxy’s past.
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| 4. |
- Romeo, Alessandro, 1961, et al.
(författare)
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The specific angular momentum of disc galaxies and its connection with galaxy morphology, bar structure, and disc gravitational instability
- 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. 1002-1021
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Tidskriftsartikel (refereegranskat)abstract
- The specific angular momenta (j equivalent to J/M) of stars (j(star)), gas (j(gas)), baryons as a whole (j(b)) and dark matter haloes (j(h)) contain clues of vital importance about how galaxies form and evolve. Using one of the largest samples of disc galaxies (S0-BCD) with high-quality rotation curves and near-infrared surface photometry, we perform a detailed comparative analysis of j that stretches across a variety of galaxy properties. Our analysis imposes tight constraints on the 'retained' fractions of specific angular momentum (j(star)/j(h), j(Hi)/j(h), and j(b)/j(h)), as well as on their systematic trends with mass fraction and galaxy morphology, thus on how well specific angular momentum is conserved in the process of disc galaxy formation and evolution. In particular, one of the most innovative results of our analysis is the finding that galaxies with larger baryon fractions have also retained larger fractions of their specific angular momentum. Furthermore, our analysis demonstrates how challenging it is to characterize barred galaxies from a gravitational instability point of view. This is true not only for the popular Efstathiou, Lake & Negroponte bar instability criterion, which fails to separate barred from non-barred galaxies in about 55 percent of the cases, but also for the mass-weighted Toomre parameter of atomic gas, < Q(HI)>, which succeeds in separating barred from non-barred galaxies, but only in a statistical sense.
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| 5. |
- Schinnerer, Eva, et al.
(författare)
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PHANGS-JWST First Results : Rapid Evolution of Star Formation in the Central Molecular Gas Ring of NGC 1365
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 944:2
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale bars can fuel galaxy centers with molecular gas, often leading to the development of dense ringlike structures where intense star formation occurs, forming a very different environment compared to galactic disks. We pair ∼0.″3 (30 pc) resolution new JWST/MIRI imaging with archival ALMA CO(2-1) mapping of the central ∼5 kpc of the nearby barred spiral galaxy NGC 1365 to investigate the physical mechanisms responsible for this extreme star formation. The molecular gas morphology is resolved into two well-known bright bar lanes that surround a smooth dynamically cold gas disk (R gal ∼ 475 pc) reminiscent of non-star-forming disks in early-type galaxies and likely fed by gas inflow triggered by stellar feedback in the lanes. The lanes host a large number of JWST-identified massive young star clusters. We find some evidence for temporal star formation evolution along the ring. The complex kinematics in the gas lanes reveal strong streaming motions and may be consistent with convergence of gas streamlines expected there. Indeed, the extreme line widths are found to be the result of inter-“cloud” motion between gas peaks; ScousePy decomposition reveals multiple components with line widths of 〈σ CO,scouse〉 ≈ 19 km s−1 and surface densities of 〈 Σ H 2 , scouse 〉 ≈ 800 M ⊙ pc − 2 , similar to the properties observed throughout the rest of the central molecular gas structure. Tailored hydrodynamical simulations exhibit many of the observed properties and imply that the observed structures are transient and highly time-variable. From our study of NGC 1365, we conclude that it is predominantly the high gas inflow triggered by the bar that is setting the star formation in its CMZ.
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