Rotational support of giant clumps in high-z disc galaxies

By D. Ceverino, A. Dekel, Nir Mandelker, Frédéric Bournaud, A. Burkert, R. Genzel, Joel R. Primack. 2011

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We address the internal support against total free-fall col lapse of the giant clumps that form by violent gravitational instability in high-z disc galaxies. Guidance is provided by an analytic model, where the proto-clumps are cut from a rotating disc and collapse to equilibrium while preserving angular momentum. This model predicts prograde clump rotation, which dominates the support if the clump has contracted to a surface-density contrast > ∼10. This is confirmed in hydro-AMR zoom-in simulations of galaxies in a cosmological context. In most high-z clumps, the centrifugal force dominates the support, R ≡ V 2 rot/V 2 circ > 0.5, where Vrot is the rotation velocity and the circular velocity Vcirc measures the potential well. The clump spin indeed tends to be in the sense of the global disc angular momentum, but substantial tilts are frequent, reflecting the highly wa rped nature of the high-z discs. Most clumps are in Jeans equilibrium, with the rest of the support provided by turbulence, partly driven by the gravitational instability itself. The general agreement between model and simulations indicates that angular-momentum loss or gain in most clumps is limited to a factor of two. Simulations of isolated gas-rich discs that resolve the clump substructure reveal that the cosmological simulations may overestimate R by ∼30%, but the dominance of rotational support at high z is not a resolution artifact. In turn, isolated gas-poor dis c simulations produce at z = 0 smaller gaseous non-rotating transient clouds, indicatin g that the difference in rotational support is associated with the fra ction of cold baryons in the disc. In our current cosmological simulations, the clump rotation velocity is typically more than twice the disc dispersion, Vrot ∼100kms −1 , but when beam smearing of >0.1 arcsec is imposed, the rotation signal is reduced to a small gradient of 6 30kms −1 kpc −1 across the clump. The velocity dispersion in the simulated clumps is comparable to the disc dispersion so it is expected to leave only a marginal signal for any beam smearing. Retrograde minor-merging galaxies could lead to massive clumps that do not show rotation even when marginally resolved. Testable predictions of the scenario as simulate d are that the mean stellar age of the clumps, and the stellar fraction, are declining linearl y with distance from the disc center.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b8e78e7203d2cbebcd22abc4464bc1102f4d2327

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Citations in the corpus

THE LONG LIVES OF GIANT CLUMPS AND THE BIRTH OF OUTFLOWS IN GAS-RICH GALAXIES AT HIGH REDSHIFT (2013, background): “Note that simulated molecular clouds in lowredshift galaxies were found to be short-lived and unvirialized even when only some of the feedback modes are included (e.g., Tasker 2011; Bournaud et al. 2010; Ceverino et al. 2012).”
Toy models for galaxy formation versus simulations (2013, methodology): “The galaxies MW04 and SFG1 were added to the study of giant clumps in VDI discs by Ceverino et al. (2012).”
Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets (2014, methodology): “Supernovae and stellar winds are implemented by local injection of thermal energy as in Ceverino & Klypin (2009); Ceverino, Dekel & Bournaud (2010); Ceverino et al. (2012).”
The Milky Way’s stellar disk (2013, background): “Alternatively, the disk could have been born with larger velocity dispersion than is typical at z ≈ 0 (Bournaud et al. 2009; Ceverino et al. 2012), or purely internal dynamical evolution due to radial migration may gradually thicken the disk (Schönrich & Binney 2009; Loebman et al. 2011; Minchev…”
The confinement of star-forming galaxies into a main sequence through episodes of gas compaction, depletion and replenishment (2015, background): “Specifically, these simulations trace the cosmological streams that feed galaxies at high redshift, including mergers and smooth flows, and they resolve the VDI that governs high-z disc evolution and bulge formation (Ceverino et al. 2010, 2012, 2015a; Mandelker et al. 2014).”
Radiative feedback and the low efficiency of galaxy formation in low-mass haloes at high redshift (2013, methodology): “…representing subgrid physics, include gas cooling by atomic hydrogen and helium, metal and molecular hydrogen cooling, and photoionization heating by a constant cosmological UV background with partial self-shielding, star formation and feedback, as described in Ceverino et al. (2010, 2012).”
Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge (2014, background): “…highly perturbed, with large transient features and in situ giant clumps (Noguchi 1999; Immeli et al. 2004; Genzel et al. 2006; Bournaud, Elmegreen & Elmegreen 2007; Genzel et al. 2008; Agertz, Teyssier & Moore 2009; Dekel, Sari & Ceverino 2009; Ceverino et al. 2010, 2012; Mandelker et al. 2014).”
The SINS/zC-SINF Survey of z ∼ 2 Galaxy Kinematics: SINFONI Adaptive Optics–assisted Data and Kiloparsec-scale Emission-line Properties (2018, background): “…externallydriven perturbations caused by non-axisymmetric substructures such as massive disk clumps, bars, and spiral arms, or induced by minor mergers and interactions (e.g., Bournaud et al. 2007; Genel et al. 2012; Ceverino et al. 2012), which may also be difficult to disentangle from each other.”
Star formation sustained by gas accretion (2014, background): “This non-trivial observational result is naturally accommodated within the gas accretion scenario (e.g., Ceverino et al. 2012, and Sect.”
Evolution of density profiles in high-z galaxies: compaction and quenching inside-out (2015, methodology): “Supernovae and stellar winds are implemented by local injection of thermal energy as in Ceverino & Klypin (2009); Ceverino et al. (2010) and Ceverino et al. (2012).”
Wet Disc Contraction to Galactic Blue Nuggets and Quenching to Red Nuggets (2013, background): “…in the form of large transient features and giant clumps (Noguchi 1999; Immeli et al. 2004b,a; Genzel et al. 2006; Bournaud, Elmegreen & Elmegreen 2007; Genzel et al. 2008; Dekel, Sari & Ceverino 2009; Agertz, Teyssier & Moore 2009; Ceverino, Dekel & Bournaud 2010; Ceverino et al. 2012).”
The Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: Compact Bulges, and the Rise and Fall of Massive Disks (2012, background): “…of today’s giant ellipticals are these high velocity dispersion, clumpy discs, in which star formation is fed by cold streams and minor mergers (e.g. Dekel, Sari & Ceverino 2009b; Ceverino, Dekel & Bournaud 2010; Ceverino et al. 2012) with the clumps eventually coalescing to form a spheroid.”
Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “Galaxies containing baryon mass of 1010–1011M typically form clumps of mass '108–109M (see [320,322,323]).”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, result): “It is interesting to compare in more detail our predicted covering fractions with the results of Fumagalli et al. (2014), who used AMR simulations from Ceverino et al. (2010), Ceverino et al. (2012), and Dekel et al. (2013).”