Simulations of the Milky Way’s Central Molecular Zone – II. Star formation

Sormani, Mattia C.; Treß, Robin G.; Glover, Simon C. O.; Klessen, Ralf S.; Battersby, Cara; Clark, Paul; Hatchfield, H Perry; Smith, Rowan J.

doi:10.1093/mnras/staa1999

Cited by 71 publications

(51 citation statements)

References 101 publications

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“…Comparison to Other Simulations -In our models the SN feedback alone induces a factor of ∼ 2 fluctuations of the SFR with timescale 40 Myr (see also Paper I). This appears consistent with the results of the global simulations of Sormani et al (2020) who found that the 4 Although the two spiral arm model seems to place the Sgr B2 complex and brick at the far side, the absorption and proper motion data strongly suggest that they are at the near side. Ridley et al (2017) reconciled this inconsistency by suggesting that those clouds are kinematically detached, jutting out of the nearside arm.…”

Section: Summary and Discussionsupporting

confidence: 88%

“…In global simulations of nuclear rings (e.g., Seo et al 2019;Armillotta et al 2019;Sormani et al 2020;Tress et al 2020), the inflow rate is naturally time variable and feedback is always active following star formation, so that it is difficult to discern what dominates in shaping the star formation history of nuclear rings. To separate the effects of feedback from those of the mass inflow, Moon et al (2021, hereafter Paper I) designed semiglobal models that focus on nuclear rings and nearby regions, handling the bar-driven mass inflows along dust lanes by gas streams through two nozzles located at the domain boundaries.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Varying Mass Inflows on Star Formation in Nuclear Rings of Barred Galaxies

Moon,

Kim,

Kim

et al. 2021

Preprint

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Observations indicate that the star formation rate (SFR) of nuclear rings varies considerably with time and is sometimes asymmetric rather than being uniform across a ring. To understand what controls temporal and spatial distributions of ring star formation, we run semi-global, hydrodynamic simulations of nuclear rings subject to time-varying and/or asymmetric mass inflow rates. These controlled variations in the inflow lead to variations in the star formation, while the ring orbital period (18 Myr) and radius (600 pc) remain approximately constant. We find that both the mass inflow rate and supernova feedback affect the ring SFR. An oscillating inflow rate with period ∆τ in and amplitude 20 causes large-amplitude (a factor of 5), quasi-periodic variations of the SFR, when ∆τ in 50 Myr. We find that the time-varying ISM weight and midplane pressure track each other closely, establishing an instantaneous vertical equilibrium. The measured time-varying depletion time is consistent with the prediction from self-regulation theory provided the time delay between star formation and supernova feedback is taken into account. The supernova feedback is responsible only for small-amplitude (a factor of ∼ 2) fluctuations of the SFR with a timescale 40 Myr. Asymmetry in the inflow rate does not necessarily lead to asymmetric star formation in nuclear rings. Only when the inflow rate from one dust lane is suddenly increased by a large factor, the rings undergo a transient period of lopsided star formation.

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Section: Summary and Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Effects of Varying Mass Inflows on Star Formation in Nuclear Rings of Barred Galaxies

Moon,

Kim,

Kim

et al. 2021

Preprint

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“…This dust-ridge is thought to be connected to the ionised ridge via a ring of material surrounding the Galactic Centre found in simulations (e.g. Sormani et al 2018;Dale et al 2019a;Kruijssen et al 2019a;Sormani et al 2020;Tress et al 2020) and extragalactic systems (e.g. Comerón et al 2010;Krieger et al 2020), which is maintained by the inflow of material from the bar (e.g.…”

Section: Introductionmentioning

confidence: 92%

Which feedback mechanisms dominate in the high-pressure environment of the central molecular zone?

Barnes

Longmore

Dale

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Supernovae (SNe) dominate the energy and momentum budget of stellar feedback, but the efficiency with which they couple to the interstellar medium (ISM) depends strongly on how effectively early, pre-SN feedback clears dense gas from star-forming regions. There are observational constraints on the magnitudes and timescales of early stellar feedback in low ISM pressure environments, yet no such constraints exist for more cosmologically typical high ISM pressure environments. In this paper, we determine the mechanisms dominating the expansion of H ii regions as a function of size-scale and evolutionary time within the high-pressure (P/kB ∼ 107 − 8 K cm−3) environment in the inner 100 pc of the Milky Way. We calculate the thermal pressure from the warm ionised (PHII; 104 K) gas, direct radiation pressure (Pdir), and dust processed radiation pressure (PIR). We find that (1) Pdir dominates the expansion on small scales and at early times (0.01-0.1 pc; <0.1 Myr); (2) the expansion is driven by PHII on large scales at later evolutionary stages (>0.1 pc; >1 Myr); (3) during the first ≲ 1 Myr of growth, but not thereafter, either PIR or stellar wind pressure likely make a comparable contribution. Despite the high confining pressure of the environment, natal star-forming gas is efficiently cleared to radii of several pc within ∼ 2 Myr, i.e. before the first SNe explode. This ‘pre-processing’ means that subsequent SNe will explode into low density gas, so their energy and momentum will efficiently couple to the ISM. We find the H ii regions expand to a radius of ∼ 3pc, at which point they have internal pressures equal with the surrounding external pressure. A comparison with H ii regions in lower pressure environments shows that the maximum size of all H ii regions is set by pressure equilibrium with the ambient ISM.

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“…The emerging picture is therefore the following: most of the mass of the NSD formed shortly after the formation of the bar > 8 Gyr ago. Then, from 8 Gyr ago to the present day, the NSD has grown further at variable rates depending on the rate of SFR in the CMZ, which is regulated by the amount of fresh gas available through the bar-driven inflow and possibly by internal feedback cycles (for discussions on what controls the star formation rate in the CMZ see for example Kruĳssen et al 2014;Krumholz et al 2017;Armillotta et al 2019;Sormani et al 2020a;Moon et al 2021b,a).…”

Section: Formation and Evolution Of The Nsdmentioning

confidence: 99%

Jeans modelling of the Milky Way’s nuclear stellar disc

Sormani

Magorrian²,

Nogueras-Lara

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The nuclear stellar disc (NSD) is a flattened stellar structure that dominates the gravitational potential of the Milky Way at Galactocentric radii 30 ≲ R ≲ 300 pc. In this paper, we construct axisymmetric Jeans dynamical models of the NSD based on previous photometric studies and we fit them to line-of-sight kinematic data of APOGEE and SiO maser stars. We find that (i) the NSD mass is lower but consistent with the mass independently determined from photometry by Launhardt et al. (2002). Our fiducial model has a mass contained within spherical radius r = 100 pc of $M(r<100\, {\rm pc}) = 3.9 \pm 1 \times 10^8 \, \rm M_\odot$ and a total mass of $M_{\rm NSD} = 6.9 \pm 2 \times 10^8 \, \rm M_\odot$. (ii) The NSD might be the first example of a vertically biased disc, i.e. with ratio between the vertical and radial velocity dispersion σz/σR > 1. Observations and theoretical models of the star-forming molecular gas in the central molecular zone suggest that large vertical oscillations may be already imprinted at stellar birth. However, the finding σz/σR > 1 depends on a drop in the velocity dispersion in the innermost few tens of parsecs, on our assumption that the NSD is axisymmetric, and that the available (extinction corrected) stellar samples broadly trace the underlying light and mass distributions, all of which need to be established by future observations and/or modelling. (iii) We provide the most accurate rotation curve to date for the innermost 500 pc of our Galaxy.

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Simulations of the Milky Way’s Central Molecular Zone – II. Star formation

Cited by 71 publications

References 101 publications

Effects of Varying Mass Inflows on Star Formation in Nuclear Rings of Barred Galaxies

Effects of Varying Mass Inflows on Star Formation in Nuclear Rings of Barred Galaxies

Which feedback mechanisms dominate in the high-pressure environment of the central molecular zone?

Jeans modelling of the Milky Way’s nuclear stellar disc

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