Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal redistribution

ABSTRACT Using a set of 15 high-resolution magnetohydrodynamic cosmological simulations of Milky Way formation, we investigate the origin of the baryonic material found in stars at redshift zero. We find that roughly half of this material originates from subhalo/satellite systems and half is smoothly accreted from the intergalactic medium. About $90 {{\ \rm per\ cent}}$ of all material has been ejected and re-accreted in galactic winds at least once. The vast majority of smoothly accreted gas enters into a galactic fountain that extends to a median galactocentric distance of ∼20 kpc with a median recycling time-scale of ∼500 Myr. We demonstrate that, in most cases, galactic fountains acquire angular momentum via mixing of low angular momentum, wind-recycled gas with high angular momentum gas in the circumgalactic medium (CGM). Prograde mergers boost this activity by helping to align the disc and CGM rotation axes, whereas retrograde mergers cause the fountain to lose angular momentum. Fountain flows that promote angular momentum growth are conducive to smooth evolution on tracks quasi-parallel to the disc sequence of the stellar mass-specific angular momentum plane, whereas retrograde minor mergers, major mergers, and bar-driven secular evolution move galaxies towards the bulge sequence. Finally, we demonstrate that fountain flows act to flatten and narrow the radial metallicity gradient and metallicity dispersion of disc stars, respectively. Thus, the evolution of galactic fountains depends strongly on the cosmological merger history and is crucial for the chemodynamical evolution of Milky-Way-sized disc galaxies.

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Galaxy Dynamics: Secular Evolution and Accretion

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311017522 ◽

2010 ◽

Vol 6 (S271) ◽

pp. 119-126 ◽

Cited By ~ 1

Author(s):

Francoise Combes

Keyword(s):

Angular Momentum ◽

Galaxy Evolution ◽

Resonant Scattering ◽

Relative Role ◽

Radial Migration ◽

Galaxy Dynamics ◽

Secular Evolution ◽

Minor Mergers ◽

Gas Accretion

AbstractRecent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation.

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Secular evolution in young galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314011478 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 375-375

Author(s):

Bruce G. Elmegreen

Keyword(s):

Angular Momentum ◽

Milky Way ◽

High Redshift ◽

Thick Disk ◽

High Dispersion ◽

Star Forming ◽

Secular Evolution ◽

Disk Mass ◽

High Fraction ◽

Gas Fractions

AbstractYoung galaxies viewed at high redshift have high turbulent velocities, high star formation rates, high gas fractions, and chaotic structures, suggesting wild instabilities during which giant gas clumps form and make stars in their dense regions, stir other disk stars and gas, and transport angular momentum outward with a resulting net mass flow inward (e.g., Ceverino et al.2010). At z=1.5, 40% of star-forming galaxies have significant clumps (Elmegreen et al.2007; Wuyts et al.2012), and in these, 10%-20% of the stellar mass is in clumps that last ~150 Myr (Elmegreen et al.2009; Wuyts et al.2012). The thick disk and bulge in modern galaxies could form in this phase. The similarity in the α/Fe ratio (Meléndez et al.2008), K-giant abundances (Bensby et al.2010) and ages for the Milky Way bulge and thick disk suggest they formed at the same time. High dispersion gas at z ~ 1.5 can do this because it makes the young disk thick and the SF clumps big enough to drive fast secular evolution (Elmegreen et al.2006; Genzel et al.2008; Bournaud et al.2009). Local analogues might be present in dynamically young galaxies like BCDs (Elmegreen et al.2012). The high fraction of z ~ 1.5 galaxies with massive clumps suggests clump formation is a long-lived phase and that clump torques should last ~ 1 Gyr or more even if individual clumps come and go on shorter timescales. Clump formation may cease when stars finally dominate the disk mass (Cacciato et al. 2012).

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Accretion Onto the Milky Way: The Smith Cloud

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007171 ◽

2015 ◽

Vol 11 (S315) ◽

pp. 9-12

Author(s):

Felix J. Lockman

Keyword(s):

Dark Matter ◽

Angular Momentum ◽

Stellar Population ◽

Milky Way ◽

Galactic Plane ◽

Dwarf Galaxy ◽

Dark Matter Halo ◽

Ionized Gas ◽

Gas Accretion

AbstractActive gas accretion onto the Milky Way is observed in an object called the Smith Cloud, which contains several million solar masses of neutral and warm ionized gas and is currently losing material to the Milky Way, adding angular momentum to the disk. It is several kpc in size and its tip lies 2 kpc below the Galactic plane. It appears to have no stellar counterpart, but could contain a stellar population like that of the dwarf galaxy Leo P. There are suggestions that its existence and survival require that it be embedded in a dark matter halo of a few 108 solar masses.

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Gaia EDR3 Proper Motions of Milky Way Dwarfs. II Velocities, Total Energy, and Angular Momentum

The Astrophysical Journal ◽

10.3847/1538-4357/ac27a8 ◽

2021 ◽

Vol 922 (2) ◽

pp. 93

Author(s):

Francois Hammer ◽

Jianling Wang ◽

Marcel S. Pawlowski ◽

Yanbin Yang ◽

Piercarlo Bonifacio ◽

...

Keyword(s):

Angular Momentum ◽

Total Energy ◽

Large Scale ◽

Milky Way ◽

Radial Velocities ◽

Proper Motions ◽

Satellite Systems ◽

Angular Momenta ◽

Total Energies ◽

Mass Profile

Abstract Here we show that precise Gaia EDR3 proper motions have provided robust estimates of 3D velocities, angular momentum, and total energy for 40 Milky Way dwarfs. The results are statistically robust and are independent of the Milky Way mass profile. Dwarfs do not behave like long-lived satellites of the Milky Way because of their excessively large velocities, angular momenta, and total energies. Comparing them to other MW halo populations, we find that many are at first passage, ≤2 Gyr ago, i.e., more recent than the passage of Sagittarius, ∼4–5 Gyr ago. We suggest that this is in agreement with the stellar populations of all dwarfs, for which we find that a small fraction of young stars cannot be excluded. We also find that dwarf radial velocities contribute too little to their kinetic energy when compared to satellite systems with motions only regulated by gravity, and some other mechanism must be at work such as ram pressure. The latter may have preferentially reduced radial velocities when dwarf progenitors entered the halo until they lost their gas. It could also explain why most dwarfs lie near their pericenter. We also discover a novel large-scale structure perpendicular to the Milky Way disk, which is made by 20% of dwarfs orbiting or counter-orbiting with the Sagittarius dwarf.

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Rotation of classical bulges during secular evolution of barred galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314005936 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 329-329

Author(s):

Kanak Saha ◽

Ortwin Gerhard

Keyword(s):

Angular Momentum ◽

Milky Way ◽

Disk Galaxies ◽

Barred Galaxies ◽

Secular Evolution ◽

Low Mass ◽

Fast Rotating

AbstractBar driven secular evolution plays a key role in changing the morphology and kinematics of disk galaxies, leading to the formation of rapidly rotating boxy/peanut bulges. If these disk galaxies also hosted a preexisting classical bulge, how would the secular evolution influence the classical bulge, and also the observational properties.We first study the co-evolution of a bar and a preexisting non-rotating low-mass classical bulge such as might be present in galaxies like the Milky Way. It is shown with N-body simulations that during the secular evolution, such a bulge can gain significant angular momentum emitted by the bar through resonant and stochastic orbits. Thereby it transforms into a cylindrically rotating, anisotropic and triaxial object, embedded in the fast rotating boxy bulge that forms via disk instability (Saha et al. 2012). The composite boxy/peanut bulge also rotates cylindrically.We then show that the growth of the bar depends only slightly on the rotation properties of the preexisting classical bulge. For the initially rotating small classical bulge, cylindrical rotation in the resulting composite boxy/peanut bulge extends to lower heights (Saha & Gerhard 2013). More massive classical bulges also gain angular momentum emitted by the bar, inducing surprisingly large rotational support within about 4 Gyrs (Saha et al. in prep).

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The Distribution of Bar Strengths in Disk Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921306005187 ◽

2006 ◽

Vol 2 (S235) ◽

pp. 81-81

Author(s):

R. Buta ◽

E. Laurikainen ◽

H. Salo ◽

J. H. Knapen ◽

D. L. Block

Keyword(s):

Angular Momentum ◽

Momentum Transfer ◽

Disk Galaxies ◽

Early Type ◽

Angular Momentum Transfer ◽

Secular Evolution ◽

Gas Accretion ◽

Early Type Galaxy

AbstractBars are the most important features that redistribute angular momentum and drive secular evolution in disk galaxies. We have derived the distribution of bar strengths in spirals and the Fourier properties of early-type galaxy bars in order to evaluate recent models of bar-halo angular momentum transfer and external gas accretion. A few results are presented here.

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The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa4017 ◽

2021 ◽

Author(s):

Myoungwon Jeon ◽

Volker Bromm ◽

Gurtina Besla ◽

Jinmi Yoon ◽

Yumi Choi

Keyword(s):

Milky Way ◽

Dwarf Galaxies ◽

Mass Resolution ◽

Explosion Energy ◽

High Carbon ◽

Cosmological Simulations ◽

Carbon Abundance ◽

The Absolute ◽

Zoom In

Abstract CEMP-no stars, a subset of carbon enhanced metal poor (CEMP) stars ($\rm [C/Fe]\ge 0.7$ and $\rm [Fe/H]\lesssim -1$) have been discovered in ultra-faint dwarf (UFD) galaxies, with Mvir ≈ 108 M⊙ and M* ≈ 103 − 104 M⊙ at z = 0, as well as in the halo of the Milky Way (MW). These CEMP-no stars are local fossils that may reflect the properties of the first (Pop III) and second (Pop II) generation of stars. However, cosmological simulations have struggled to reproduce the observed level of carbon enhancement of the known CEMP-no stars. Here we present new cosmological hydrodynamic zoom-in simulations of isolated UFDs that achieve a gas mass resolution of mgas ≈ 60 M⊙. We include enrichment from Pop III faint supernovae (SNe), with ESN = 0.6 × 1051 erg, to understand the origin of CEMP-no stars. We confirm that Pop III and Pop II stars are mainly responsible for the formation of CEMP and C-normal stars respectively. New to this study, we find that a majority of CEMP-no stars in the observed UFDs and the MW halo can be explained by Pop III SNe with normal explosion energy (ESN = 1.2 × 1051 erg) and Pop II enrichment, but faint SNe might also be needed to produce CEMP-no stars with $\rm [C/Fe]\gtrsim 2$, corresponding to the absolute carbon abundance of $\rm A(C)\gtrsim 6.0$. Furthermore, we find that while we create CEMP-no stars with high carbon ratio $\rm [C/Fe]\approx 3-4$, by adopting faint SNe, it is still challenging to reproduce CEMP-no stars with extreme level of carbon abundance of $\rm A(C)\approx 7.0-7.5$, observed both in the MW halo and UFDs.

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Effects of initial density profiles on massive star cluster formation in giant molecular clouds

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab491 ◽

2021 ◽

Author(s):

Yingtian Chen ◽

Hui Li ◽

Mark Vogelsberger

Keyword(s):

Angular Momentum ◽

Star Formation ◽

Molecular Clouds ◽

Globular Clusters ◽

Cluster Formation ◽

Initial Density ◽

Giant Molecular Clouds ◽

Density Profiles ◽

Stellar Feedback ◽

Gas Accretion

Abstract We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ‘hierarchically’ to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ‘accretion’ mode from centrally-concentrated clouds in the early Universe.

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The mass of the Milky Way out to 100 kpc using halo stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3984 ◽

2020 ◽

Author(s):

Alis J Deason ◽

Denis Erkal ◽

Vasily Belokurov ◽

Azadeh Fattahi ◽

Facundo A Gómez ◽

...

Keyword(s):

Distribution Function ◽

Mass Concentration ◽

Milky Way ◽

Function Analysis ◽

Large Magellanic Cloud ◽

Systematic Bias ◽

Cosmological Simulations ◽

Halo Stars ◽

Systematic Effects ◽

Mass Estimate

Abstract We use a distribution function analysis to estimate the mass of the Milky Way out to 100 kpc using a large sample of halo stars. These stars are compiled from the literature, and the vast majority ($\sim \! 98\%$) have 6D phase-space information. We pay particular attention to systematic effects, such as the dynamical influence of the Large Magellanic Cloud (LMC), and the effect of unrelaxed substructure. The LMC biases the (pre-LMC infall) halo mass estimates towards higher values, while realistic stellar halos from cosmological simulations tend to underestimate the true halo mass. After applying our method to the Milky Way data we find a mass within 100 kpc of M( < 100kpc) = 6.07 ± 0.29(stat.) ± 1.21(sys.) × 1011M⊙. For this estimate, we have approximately corrected for the reflex motion induced by the LMC using the Erkal et al. model, which assumes a rigid potential for the LMC and MW. Furthermore, stars that likely belong to the Sagittarius stream are removed, and we include a 5% systematic bias, and a 20% systematic uncertainty based on our tests with cosmological simulations. Assuming the mass-concentration relation for Navarro-Frenk-White haloes, our mass estimate favours a total (pre-LMC infall) Milky Way mass of M200c = 1.01 ± 0.24 × 1012M⊙, or (post-LMC infall) mass of M200c = 1.16 ± 0.24 × 1012 M⊙ when a 1.5 × 1011M⊙ mass of a rigid LMC is included.

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Detecting the halo heating from AGN feedback with ALMA

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2945 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5134-5146 ◽

Cited By ~ 2

Author(s):

S Brownson ◽

R Maiolino ◽

M Tazzari ◽

S Carniani ◽

N Henden

Keyword(s):

Star Formation ◽

Correction Factor ◽

Spatial Scales ◽

Complex Structure ◽

Host Galaxy ◽

Cosmological Simulations ◽

Beam Attenuation ◽

Gas Accretion ◽

Marginal Detection ◽

Compact Sources

ABSTRACT The Sunyaev–Zel’dovich (SZ) effect can potentially be used to investigate the heating of the circumgalactic medium and subsequent suppression of cold gas accretion on to the host galaxy caused by quasar feedback. We use a deep ALMA observation of HE0515-4414 in band 4, the most luminous quasar known at the peak of cosmic star formation (z = 1.7), to search for the SZ signal tracing the heating of the galaxy’s halo. ALMA’s sensitivity to a broad range of spatial scales enables us to disentangle emitting compact sources from the negative, extended SZ signal. We obtain a marginal SZ detection (∼3.3σ) on scales of about 300 kpc (30–40 arcsec), at the 0.2 mJy level, 0.5 mJy after applying a correction factor for primary beam attenuation and flux that is resolved out by the array. We show that our result is consistent with a simulated ALMA observation of a similar quasar in the fable cosmological simulations. We emphasize that detecting an SZ signal is more easily achieved in the visibility plane than in the (inferred) images. We also confirm a marginal detection (3.2σ) of a potential SZ dip on smaller scales (<100 kpc) already claimed by other authors, possibly highlighting the complex structure of the halo heating. Finally, we use SZ maps from the fable cosmological simulations, convolved with ALMA simulations, to illustrate that band 3 observations are much more effective in detecting the SZ signal with higher significance, and discuss the optimal observing strategy.

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