THE THICK DISKS OF SPIRAL GALAXIES AS RELICS FROM GAS-RICH, TURBULENT, CLUMPY DISKS AT HIGH REDSHIFT

By Frédéric Bournaud, Bruce G. Elmegreen, M. Martig. 2009

243 citations recorded by the source corpus.

The formation of thick stellar disks in spiral galaxies is studied. Simulations of gas-rich young galaxies show formation of internal clumps by gravitational instabilities, clump coalescence into a bulge, and disk thickening by strong stellar scattering. The bulge and thick disks of modern galaxies may form this way. Simulations of minor mergers make thick disks too, but there is an important difference. Thick disks made by internal processes have a constant scale height with galactocentric radius, but thick disks made by mergers flare. The difference arises because in the first case, perpendicular forcing and disk-gravity resistance are both proportional to the disk column density, so the resulting scale height is independent of this density. In the case of mergers, perpendicular forcing is independent of the column density and the low-density regions get thicker; the resulting flaring is inconsistent with observations. Late-stage gas accretion and thin-disk growth are shown to preserve the constant scale heights of thick disks formed by internal evolution. These results reinforce the idea that disk galaxies accrete most of their mass smoothly and acquire their structure by internal processes, in particular through turbulent and clumpy phases at high redshift.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/35b3dbe19734b5d014d8652054855161b506a0e6

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In Astronomy and Astrophysics

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2. L. Hernquist
3. A. Dekel
4. R. Dav'e
5. R. Somerville
6. Volker Springel
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In Instrumentation

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7. T. Naab
8. P. V. van Dokkum

Citations in the corpus

• The age–metallicity structure of the Milky Way disc using APOGEE (2017, background): “Flaring has also been shown to arise as a result of satellite infall, which can be a stronger flaring agent than migrations (e.g. Bournaud et al. 2009).”
• Alpha element abundances and gradients in the Milky Way bulge from FLAMES-GIRAFFE spectra of 650 K giants (2011, background): “Particularly interesting, in the context of our results, are the scenarios in which both bulge and thick disk share a fast and early formation such as the scenario discussed in Bournaud et al. (2009) (see also Immeli et al. 2004).”
• Cool Gas in High-Redshift Galaxies (2013, methodology): “Their dynamical analysis is guided by numerical simulations of clumpy, turbulent disks, to allow for significant non– circular motions (Bournaud et al. 2009).”
• THE GENESIS OF THE MILKY WAY'S THICK DISK VIA STELLAR MIGRATION (2010, result): “Brook et al. (2004) and Bournaud et al. (2009) formed a thick disk in situ at high redshift during gas-rich mergers, where star formation is triggered by the rapid accretion of gas; this result is consistent with the thick disk forming through violent relaxation of the galactic potential.”
• THE MILKY WAY HAS NO DISTINCT THICK DISK (2011, background): “…the rate of minor mergers, the resilience of stellar disks to such mergers, and the importance of ‘internal’ heating mechanisms such as radial migration (Sellwood & Binney 2002) or turbulent, gravitationally unstable disk evolution (e.g., Bournaud et al. 2009; Förster Schreiber et al. 2009).”
• THE VERTICAL METALLICITY GRADIENT OF THE MILKY WAY DISK: TRANSITIONS IN [α/Fe] POPULATIONS (2014, background): “Brook et al. (2004, 2005) and Bournaud et al. (2009) propose that the thick disk may result from early accretion of gas-rich material.”
• EVOLVING GRAVITATIONALLY UNSTABLE DISKS OVER COSMIC TIME: IMPLICATIONS FOR THICK DISK FORMATION (2011, methodology): “In particular, the age-velocity dispersion-metallicity correlation of stars in the solar neighborhood (Nordström et al. 2004), might well be explained by means of gravitational instability in high redshift disks (Bournaud et al. 2009).”
• Vertical disc heating in Milky Way-sized galaxies in a cosmological context (2015, background): “…a thickened disc inherited their high velocity dispersions at birth from a turbulent, clumpy interstellar medium (ISM) during stages of heavy cosmological gas accretion at high redshift (Noguchi 1998; Bournaud et al. 2009), which is later followed by more quiescent evolution after redshift z = 1.”
• Estimating stellar birth radii and the time evolution of Milky Way’s ISM metallicity gradient (2018, background): “MCM13 argued that it was a combination of both stars born hot at high redshift (Bournaud et al. 2009; Forbes et al. 2012) and subsequent heating from mergers (Brook et al. 2004) that created the kinematically defined thick disk.”
• THE RELATIONSHIP BETWEEN MONO-ABUNDANCE AND MONO-AGE STELLAR POPULATIONS IN THE MILKY WAY DISK (2016, background): “…heating from infalling satellites (e.g., Villalobos and Helmi 2008; Quinn et al. 1993), turbulent gas-rich disk phase at high redshift (e.g., Bournaud et al. 2009; Forbes et al. 2012), massive gas-rich satellites (Brook et al. 2004, 2005), and accretion of satellite debris (Abadi et al.…”
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) (2007, unknown): “…in turn, fuel ever more sophisticated galactic dynamical and chemodynamical models (e.g., Chiappini et al. 2001, 2003; Sellwood & Binney 2002; Abadi et al. 2003; Bournaud et al. 2009; Schönrich & Binney 2009; Minchev & Famaey 2010; Bird et al. 2013; Minchev et al. 2013, 2014; Kubryk et al. 2014).”
• THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, methodology): “…these interactions may heat the disk to form a thick disk, but they are thought to also cause a significant flare whose exact properties are dependent on the encounter parameters (Quinn et al. 1993; Walker et al. 1996; Kazantzidis et al. 2008; Villalobos & Helmi 2008; Bournaud et al. 2009).”
• Radial migration does little for Galactic disc thickening (2012, background): “One possibility is that they were born thick at high redshift from the internal gravitational instabilities in gas-rich, turbulent, clumpy discs (Bournaud et al., 2009) or in the turbulent phase associated with numerous gas-rich mergers (Brook et al., 2004, 2005).”
• SHORT-LIVED STAR-FORMING GIANT CLUMPS IN COSMOLOGICAL SIMULATIONS OF z ≈ 2 DISKS (2010, background): “Second, numerical simulations, both of isolated unstable disks (Immeli et al. 2004a; Bournaud et al. 2007; Elmegreen et al. 2008; Bournaud et al. 2009) and of cosmologicalz ≈ 2 disks (Agertz et al. 2009; Ceverino et al. 2010), find the clumps to evolve in that fashion, and theoretical…”
• TRACING CHEMICAL EVOLUTION OVER THE EXTENT OF THE MILKY WAY'S DISK WITH APOGEE RED CLUMP STARS (2014, background): “Numerical simulations in which the early disk forms via a gas-rich merger (Brook et al. 2004), clumpy star-formation (Bournaud et al. 2009), or in situ star formation from a turbulent star-forming gas reservoir (e.g., Bird et al. 2013), all qualitatively match the relatively large velocity…”