From Rings to Bulges: Evidence for Rapid Secular Galaxy Evolution at z ~ 2 from Integral Field Spectroscopy in the SINS Survey

By R. Genzel, A. Burkert, N. Bouché, G. Cresci, N. F. Förster Schreiber, A. Shapley, K. Shapiro, L. Tacconi, P. Buschkamp, A. Cimatti and 15 more. 2008

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We present Hα integral field spectroscopy of well-resolved, UV/optically selected z ∼ 2 star-forming galaxies as part of the SINS survey with SINFONI on the ESO VLT. Our laser guide star adaptive optics and good seeing data show the presence of turbulent rotating star-forming outer rings/disks, plus central bulge/inner disk components, whose mass fractions relative to the total dynamical mass appear to scale with the [N II]/Hα flux ratio and the star formation age. We propose that the buildup of the central disks and bulges of massive galaxies at z ∼ 2 can be driven by the early secular evolution of gas-rich proto-disks. High-redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid “cold” accretion flows along the filaments of the cosmic web. As a result, dynamical friction and viscous processes proceed on a timescale of <1 Gyr, at least an order of magnitude faster than in z ∼ 0 disk galaxies. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short timescales of the stellar buildup observed in massive galaxies at z ∼ 2.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

• Compaction and quenching of high-z galaxies in cosmological simulations: blue and red nuggets (2014, background): “While the massive starforming discs of stellar mass∼ 1011M⊙ extend to effective radii of several kpc (Elmegreen et al. 2007; Genzel et al. 2006, 2008), the quenched spheroids of a similar mass have effective radii of order 1 kpc (Carollo et al. 2013; van der Wel et al. 2014).”
• The mean star formation rate of X-ray selected active galaxies and its evolution from z~2.5: results from PEP-Herschel (2012, background): “SF galaxies typically have large gas fractions and high turbulent line-widths (Genzel et al. 2008; Förster Schreiberet al. 2009; Daddi et al. 2010; Tacconi et al. 2010).”
• Toy models for galaxy formation versus simulations (2013, background): “This massive penetration is in general agreement with earlier estimates based on the MareNostrum simulation with lower resolution (Dekel et al. 2009; Danovich et al. 2012) and with the high SFR observed in massive galaxies at z ∼ 2 (Genzel et al. 2008, 2011).”
• The SINS/zC-SINF Survey of z ∼ 2 Galaxy Kinematics: SINFONI Adaptive Optics–assisted Data and Kiloparsec-scale Emission-line Properties (2018, methodology): “…with prominent star-forming ring strongly dominated by one bright large clump although stellar light and mass at faint levels is detected around the kinematic center based on the near-IR HST data (Genzel et al. 2008; Förster Schreiber et al. 2011a; Genzel et al. 2014a; Tacchella et al. 2015b).”
• PACS Evolutionary Probe (PEP) – a Herschel key program (2011, background): “At z∼2, objects with the same star formation rates can be on the main sequence (Daddi et al. 2007a) and are often not interacting/merging but massive, turbulent disks with star formation spread out over several kpc (e.g. Genzel et al. 2008, Shapiro et al. 2008, Förster Schreiber et al. 2009).”
• ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: SURVEY DESCRIPTION (2016, background): “Note that typical selections of main sequence galaxies for CO follow–up usually target stellar masses Mstar > 10 10 M and star formation rates SFR> 50 M yr −1 (e.g. Daddi et al. 2008, Tacconi et al. 2008, Genzel et al. 2008, Tacconi et al. 2012, Daddi et al. 2015, Genzel et al. 2015).”
• Evidence for strong dynamical evolution in disc galaxies through the last 11 Gyr. GHASP VIII – a local reference sample of rotating disc galaxies for high‐redshift studies (2009, methodology): “…quantified by a “beam smearing parameter” B, ratio between the optical galactic radius (D25/2) and the seeing FWHM. Actual observations generally lead to a B parameter lower or equal to 2-3 without AO (e.g. Förster Schreiber et al. 2006) or even B>∼6 when using AO (e.g. Genzel et al. 2008).”
• GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR FORMATION RATE, THE METALLICITY–MASS–STAR-FORMATION RATE RELATION, AND THE STELLAR CONTENT OF HALOS (2013, background): “…mass growth timescale rsSFR-1 at 1010 M from observations (Equation 2), the observed molecular gas depletion timescale τgas (from Daddi et al 2007b, Genzel et al 2008 and references therein), the Hubble timescale τH, i.e. the local age of the Universe, and finally the timescales on which the…”
• Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, methodology): “Taken at face value, our simple equilibrium model therefore should not apply to those galaxies either, as they most likely are still in the phase of rapid mass growth through merging and accretion of massive cold Page 11 of 18 clouds (Genzel et al. 2008; Elmegreen et al. 2009b).”
• 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, methodology): “Interestingly, Genzel et al. (2008) found in contrast evidence for a connection between central dynamical mass concentration and maturity of the stellar population, with theratio of dynamical mass enclosed withinr ≈ 3 and 10 kpc increasing with older stellar age and higher inferred metallicity of…”
• THE IMPACT OF COLD GAS ACCRETION ABOVE A MASS FLOOR ON GALAXY SCALING RELATIONS (2009, background): “…properties, our detailed understanding of individual SFGs has also improved greatly thanks to spatially resolved kinematic studies of the ionized gas in z ∼ 2 SFGs (e.g. SINS survey, Förster Schreiber et al. 2006, 2009; Genzel et al. 2006, 2008; Shapiro et al. 2008, 2009; Cresci et al. 2009).”
• The ATLAS3D project – XX. Mass–size and mass–σ distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2012, background): “…by giant gas clumps (Elmegreen et al. 2007; Genzel et al. 2011), have high gas fractions (Daddi et al. 2010; Tacconi et al. 2010), possess large velocity dispersion and are dominated by turbulent motions (Förster Schreiber et al. 2006, 2009; Genzel et al. 2006, 2008; Law et al. 2012).”
• Self-regulated star formation in galaxies via momentum input from massive stars (2011, methodology): “This morphology resembles the clumpy systems observed at z ∼ 2–3 (Tacconi et al. 2006; Genzel et al. 2008; Law et al. 2009).”
• An analytic model of angular momentum transport by gravitational torques: from galaxies to massive black holes (2010, background): “And in high redshift, gas-rich disk galaxies, the sinking of massive star-forming clumps may produce analogous strong gravitational torques (Bournaud et al. 2007; Genzel et al. 2008).”
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, background): “The central regions tend to be redder, at z ∼ 1–4 often surrounded by bluer ‘clumps’, which by comparison to the gas maps can be identified as large star-forming regions, resembling observed galaxies (Genzel et al. 2008; Elmegreen et al. 2009; Cameron et al. 2011; Förster Schreiber et al. 2011).”
• CONSTRAINTS ON THE ASSEMBLY AND DYNAMICS OF GALAXIES. I. DETAILED REST-FRAME OPTICAL MORPHOLOGIES ON KILOPARSEC SCALE OF z ∼ 2 STAR-FORMING GALAXIES (2010, methodology): “′′145 with ellipticity of 0.08 (or FWHM of 0.”
• Structural and Star-forming Relations since z ∼ 3: Connecting Compact Star-forming and Quiescent Galaxies (2015, background): “These galaxies resemble the quiescent population at the same redshift but are radically different from other SFGs that have irregular and clumpy appearances (Elmegreen et al. 2004; Genzel et al. 2008; Guo et al. 2015).”
• Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations (2012, background): “These mechanisms include minor mergers, disk instabilities and bars, supernova explosions or the infall of recycled gas returned to the interstellar medium (e.g. Wada 2004; Martini 2004; Jogee 2006; Genzel et al. 2008; Dekel et al. 2009; Johansson et al. 2009; Ciotti et al. 2010).”
• THE KMOS3D SURVEY: DESIGN, FIRST RESULTS, AND THE EVOLUTION OF GALAXY KINEMATICS FROM 0.7 ⩽ z ⩽ 2.7 (2014, methodology): “Additionally, we fit the approximation for the velocity dispersion in a thick disk (σ02; Genzel et al. 2008; Cresci et al. 2009) to the dispersion profile with a constant level of intrinsic dispersion, σ01, added in quadrature as described by; σ02(r) = vrot(r)hz r , (A2) σmod(r) = √ σ201 + σ02(r) 2.”