FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS

By A. Dekel, R. Sari, D. Ceverino. 2009

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We present a simple theoretical framework for massive galaxies at high redshift, where the main assembly and star formation occurred, and report on the first cosmological simulations that reveal clumpy disks consistent with our analysis. The evolution is governed by the interplay between smooth and clumpy cold streams, disk instability, and bulge formation. Intense, relatively smooth streams maintain an unstable dense gas-rich disk. Instability with high turbulence and giant clumps, each a few percent of the disk mass, is self-regulated by gravitational interactions within the disk. The clumps migrate into a bulge in ≲10 dynamical times, or ≲0.5 Gyr. The cosmological streams replenish the draining disk and prolong the clumpy phase to several Gigayears in a steady state, with comparable masses in disk, bulge, and dark matter within the disk radius. The clumps form stars in dense subclumps following the overall accretion rate, ∼100 M☉ yr−1, and each clump converts into stars in ∼0.5 Gyr. While the clumps coalesce dissipatively to a compact bulge, the star-forming disk is extended because the incoming streams keep the outer disk dense and susceptible to instability and because of angular momentum transport. Passive spheroid-dominated galaxies form when the streams are more clumpy: the external clumps merge into a massive bulge and stir up disk turbulence that stabilize the disk and suppress in situ clump and star formation. We predict a bimodality in galaxy type by z ∼ 3, involving giant-clump star-forming disks and spheroid-dominated galaxies of suppressed star formation. After z ∼ 1, the disks tend to be stabilized by the dominant stellar disks and bulges. Most of the high-z massive disks are likely to end up as today's early-type galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Dependence of galaxy quenching on halo mass and distance from its centre (2012, background): “Combined with the accretion shutdown associated with halo mass, internal mechanisms related to the bulge and the central black hole may serve as the direct cause for shutdown in star formation (Dekel et al. 2009; Martig et al. 2009).”
The origin of discs and spheroids in simulated galaxies (2011, background): “This is intriguing, since it runs against recent proposals that ‘cold flows’, i.e. gas that gets accreted directly into the galaxy without going through the hot phase, might promote the formation of extended discs (e.g. Kereš et al. 2005; Brooks et al. 2009; Dekel et al. 2009).”
THE LONG LIVES OF GIANT CLUMPS AND THE BIRTH OF OUTFLOWS IN GAS-RICH GALAXIES AT HIGH REDSHIFT (2013, background): “…measured in boxes of (200 pc)3 clump formation in a turbulent medium has been studied in many works and is not detailed again here (Noguchi 1999; Immeli et al. 2004; Bournaud et al. 2007; Agertz et al. 2009; Dekel et al. 2009b; Ceverino et al. 2010; Genel et al. 2012a; Hopkins et al. 2012).”
MORPHOLOGICAL QUENCHING OF STAR FORMATION: MAKING EARLY-TYPE GALAXIES RED (2009, background): “…without star formation, (ii) rotational shear powering turbulence (Shore et al. 2003), (iii) interactions with small satellites, dark subhalos, or more generally clumpy infall (Dekel et al. 2009b), and (iv) the magnetorotational instability in magnetized disks (Sellwood & Balbus 1999).”
Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z ~ 2-3 galaxies (2009, background): “Minor mergers and cold stream gas accretion have emerged as a possible means of building disks, central bulges and elliptical galaxies from early star forming Lyman break galaxies (Dekel et al. 2009; Brooks et al. 2009).”
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): “Another scenario which can account for star formation quenching, whilst still being consistent with the existence of passive discs, is the model of violent disc instabilities (Dekel et al. 2009b; Ceverino et al. 2010; Cacciato, Dekel & Genel 2012).”
Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets (2014, background): “In the early disc phase, streams from the cosmic web, consisting of smooth gas and merging galaxies, continuously feed galactic discs (Birnboim & Dekel 2003; Kereš et al. 2005; Dekel & Birnboim 2006; Ocvirk, Pichon & Teyssier 2008; Kereš et al. 2009; Dekel et al. 2009; Danovich et al. 2012, 2014).”
THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽ z ⩽ 2.7 (2014, neutral): “…minor mergers, with star formation and gas recycling through the circum-galactic medium driven by stellar and AGN feedback (e.g., Bower et al. 2006; Dekel et al. 2009; Bouché et al. 2010; Dutton et al. 2010; Guo et al. 2010; Davé et al. 2012; Lilly et al. 2013; Vogelsberger et al. 2013; Dekel &…”
Evolution of density profiles in high-z galaxies: compaction and quenching inside-out (2015, background): “They showed that at every radius galaxies tend to be in a slowly evolving equilibrium state (as predicted in a cosmological setting by Dekel et al. 2009b and in Cacciato et al. 2012) and they explicitly predicted the formation of a central gas “hole” with an extended gas ring.”
Wet Disc Contraction to Galactic Blue Nuggets and Quenching to Red Nuggets (2013, background): “In phase (1), streams from the cosmic web, consisting of smooth gas and merging galaxies, continuously feed the discs (Birnboim & Dekel 2003; Kereš et al. 2005; Dekel & Birnboim 2006; Ocvirk, Pichon & Teyssier 2008; Kereš et al. 2009; Dekel et al. 2009).”
MINOR MERGERS AND THE SIZE EVOLUTION OF ELLIPTICAL GALAXIES (2009, methodology): “In fact, it seems of minor importance if the gas is funneled to the center through streams or mergers of extended gas dominated disks (see e.g. Robertson et al. 2006; Johansson et al. 2009a; Dekel et al. 2009) as long as it happens on a short timescale.”
CANDELS: CONSTRAINING THE AGN–MERGER CONNECTION WITH HOST MORPHOLOGIES AT z ∼ 2 (2011, background): “It may also be due to the rise of violent gravitational instabilities in disk galaxies due to the effects of rapid cold flow accretion (Dekel et al. 2009).”
METALLICITY GRADIENTS IN THE MILKY WAY DISK AS OBSERVED BY THE SEGUE SURVEY (2011, background): “Other recent work, however, has emphasized the importance of smooth gas accretion in the growth of disk galaxies (Brooks et al. 2009; Dekel et al. 2009), which can lead to a turbulent disk with high velocity dispersion as in scenario 3.”
A LINK BETWEEN STAR FORMATION QUENCHING AND INNER STELLAR MASS DENSITY IN SLOAN DIGITAL SKY SURVEY CENTRAL GALAXIES (2013, background): “If the growth in Σ1 is due to e.g., violent disk instabilities, the timescale for clumps in the disk to fall toward the center is of order tens of dynamical times (i.e., a few Gyr; Dekel et al. 2009).”
CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. II. PROPERTIES OF KILOPARSEC-SCALE CLUMPS IN REST-FRAME OPTICAL EMISSION OF z ∼ 2 STAR-FORMING GALAXIES (2011, background): “…gas-rich Toomre-unstable disks indicate that they can fragment into large and massive star-forming clumps (e.g., Noguchi 1999; Immeli et al. 2004a,b; Bournaud et al. 2007; Genzel et al. 2008; Dekel et al. 2009; Agertz et al. 2009; Ceverino et al. 2010; Aumer et al. 2010; Genel et al. 2010).”
On the origin of the galaxy star‐formation‐rate sequence: evolution and scatter (2009, methodology): “It has been argued that in haloes above this mass range at high redshifts (z 2), the cold gas accretion rates are dominated by cold streams penetrating the hot halo (Dekel et al. 2009).”
The properties of the star-forming interstellar medium at z = 0.84-2.23 from HiZELS : mapping the internal dynamics and metallicity gradients in high-redshift disc galaxies. (2012, background): “This is qualitatively similar to the numerical models of Dekel et al. (2009a) and where the ‘cold streams’ (which are most prevalent around z ∼ 2) penetrate the halo and intersect and deposit relatively unenriched gas on to the galaxy discs at ∼15 kpc (Dekel et al. 2009a; Dekel, Sari & Ceverino…”