The role of dissipation in the scaling relations of cosmological merger remnants

Covington, M. D.; Primack, Joel R.; Porter, Lauren; Croton, Darren J.; Somerville, Rachel S.; Dekel, Avishai

doi:10.1111/j.1365-2966.2011.18926.x

Cited by 43 publications

(62 citation statements)

References 83 publications

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“…In the case of 1:5 minor mergers with a less compact satellite (red solid line), we obtain a mass-size growth relation of re ∝M 2.4 with a similar or even larger exponent for both two-component 1:10 scenarios. Therefore we consider all minor merger models (1:5 and 1:10) with dark matter halos and the diffuse 1:10 mergers to be consistent with observations even in more realistic models, where dissipational effects would reduce the size growth Cox et al 2006;Hopkins et al 2008;Covington et al 2011). The size growth via major mergers is too slow to fit observational data.…”

Section: Evolution Of the Sizesmentioning

confidence: 89%

How do minor mergers promote inside-out growth of ellipticals, transforming the size, density profile and dark matter fraction?

Hilz

Naab

Ostriker

2013

Monthly Notices of the Royal Astronomical Society

270

288

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There is observational evidence for inside-out growth of giant elliptical galaxies since z 2 − 3, which is -in contrast to disk galaxies -not driven by in-situ star formation. Many of the ∼ 10 11 M ⊙ systems at high redshift have small sizes ∼ 1kpc and surface brightness profiles with low Sersic indices n. The most likely descendants at z = 0 have, on average, grown by a factor of two in mass and a factor of four in size, indicating r ∝ M α with α 2. They also have surface brightness profiles with n 5. This evolution can be qualitatively explained on the basis of two assumptions: compact ellipticals predominantly grow by collisionless minor (mass-ratio 1:10) or intermediate (mass-ratio 1:5) 'dry' mergers, and they are embedded in massive dark matter halos which support the stripping of merging satellite stars at large radii. We draw these conclusions from idealized collisionless mergers spheroidal galaxies -with and without dark matter -with mass ratios of 1:1, 1:5, and 1:10. The sizes evolve as r ∝ M α with α < 2 for mass-ratios of 1:1 (and 1:5 without dark matter halos) and , while doubling the stellar mass, the Sersic index increases from n ∼ 4 to n ∼ 5. For minor mergers of galaxies embedded in dark matter halos, the sizes grow significantly faster and the profile shapes change more rapidly. Surprisingly, already mergers with moderate massratios of 1:5, well motivated by recent cosmological simulations, give α ∼ 2.3 and after only two merger generations (∼ 40 per cent added stellar mass) the Sersic index has increased to n > 8 (n ∼ 5.5 without dark matter), reaching a final value of n = 9.5 after doubling the stellar mass. This is accompanied by a significant increase of the dark matter fraction (from ∼ 40 per cent to 70 per cent) within the stellar halfmass radius, driven by the strong size increase probing larger, dark matter dominated regions. For equal-mass mergers the effect is much weaker. We conclude that only a few intermediate mass-ratio mergers (∼ 3 − 5 with initial mass-ratios of 1:5) of galaxies embedded in massive dark matter halos can result in the observed concurrent inside-out growth and the rapid evolution in profile shapes. This process might explain the existence of present day giant ellipticals with sizes, r > 4kpc, high Sersic indices, n > 5, and a significant amount of dark matter within the half-light radius. Apart from negative stellar metallicity gradients such a 'minor' merger scenario also predicts significantly lower dark matter fractions for z ∼ 2 compact quiescent galaxies and their rare present day analogues.

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Section: Evolution Of the Sizesmentioning

confidence: 89%

How do minor mergers promote inside-out growth of ellipticals, transforming the size, density profile and dark matter fraction?

Hilz

Naab

Ostriker

2013

Monthly Notices of the Royal Astronomical Society

270

288

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“…Simulations predict that both gas-rich major mergers (Hopkins et al 2009a;Wuyts et al 2010) and disk instabilities (Dekel et al 2009b;Ceverino et al 2010) can form cSFGs by stochastically transforming only a fraction of the larger population of normal SFGs. This process effectively shifts those (larger) galaxies into a steeper mass-size relation (Covington et al 2008(Covington et al , 2011. Alternatively, very early phases of star formation could be dominated by strongly dissipational, but efficiently cold flow fed (Kereš et al 2005;Dekel et al 2009a;Oser et al 2010), processes.…”

Section: Number Density Of Compact Galaxiesmentioning

confidence: 99%

CANDELS: THE PROGENITORS OF COMPACT QUIESCENT GALAXIES ATz∼ 2

Barro

Faber

Pérez‐González

et al. 2013

ApJ

419

588

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We combine high-resolution Hubble Space Telescope/WFC3 images with multi-wavelength photometry to track the evolution of structure and activity of massive (M > 10 10 M ) galaxies at redshifts z = 1.4-3 in two fields of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We detect compact, star-forming galaxies (cSFGs) whose number densities, masses, sizes, and star formation rates (SFRs) qualify them as likely progenitors of compact, quiescent, massive galaxies (cQGs) at z = 1.5-3. At z 2, cSFGs present SFR = 100-200 M yr −1 , yet their specific star formation rates (sSFR ∼ 10 −9 yr −1 ) are typically half that of other massive SFGs at the same epoch, and host X-ray luminous active galactic nuclei (AGNs) 30 times (∼30%) more frequently. These properties suggest that cSFGs are formed by gas-rich processes (mergers or disk-instabilities) that induce a compact starburst and feed an AGN, which, in turn, quench the star formation on dynamical timescales (few 10 8 yr). The cSFGs are continuously being formed at z = 2-3 and fade to cQGs down to z ∼ 1.5. After this epoch, cSFGs are rare, thereby truncating the formation of new cQGs. Meanwhile, down to z = 1, existing cQGs continue to enlarge to match local QGs in size, while less-gas-rich mergers and other secular mechanisms shepherd (larger) SFGs as later arrivals to the red sequence. In summary, we propose two evolutionary tracks of QG formation: an early (z 2), formation path of rapidly quenched cSFGs fading into cQGs that later enlarge within the quiescent phase, and a late-arrival (z 2) path in which larger SFGs form extended QGs without passing through a compact state.

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“…In the major merger case, the merger remnant is a merger-driven bulge, containing all the stellar mass of the two progenitors, plus the newly formed stars when the cold gas mass available in the collision is bursted (see Lu et al 2014, Croton et al 2016). We develop a recipe for the structure of the remnant (or remmant bulge) in analogy with Hatton et al (2003) and Covington et al (2011), which we represent in Fig. (1) as the orbital R radius.…”

Section: Mergers On Spheroids and Major Mergersmentioning

confidence: 99%

“…A problem of theoretical models based on hierarchical clustering has been to produce galaxies with no evidence of merger-built components (Steinmetz & Navarro 2002, Kormendy & Kennicutt 2004, and to produce a realistic distribution of galaxy morphologies (Wilman et al 2013, Fontanot et al 2015. In addition, models do not in general predict the size of bulges and ellipticals (with the exception of Hatton et al 2003 andCovington et al 2011 who use a physical recipe to calculate the size of merger remnants). Correctly producing the size of galaxies is an important test for galaxy formation models, and historically one met with scarse success.…”

Section: Introductionmentioning

confidence: 99%

The growth of discs and bulges during hierarchical galaxy formation – I. Fast evolution versus secular processes

Tonini

Mutch

Croton

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a theoretical model for the evolution of mass, angular momentum and size of galaxy disks and bulges, and we implement it into the semi-analytic galaxy formation code SAGE. The model follows both secular and violent evolutionary channels, including smooth accretion, disk instabilities, minor and major mergers. We find that the combination of our recipe with hierarchical clustering produces two distinct populations of bulges: merger-driven bulges, akin to classical bulges and ellipticals, and instability-driven bulges, akin to secular (or pseudo-)bulges. The model mostly reproduces the mass-size relation of gaseous and stellar disks, the evolution of the mass-size relation of ellipticals, the Faber-Jackson relation, and the magnitude-colour diagram of classical and secular bulges. The model predicts only a small overlap of merger-driven and instability-driven components in the same galaxy, and predicts different bulge types as a function of galaxy mass and disk fraction. Bulge type also affects the star formation rate and colour at a given luminosity. The model predicts a population of merger-driven red ellipticals that dominate both the low-mass and high-mass ends of the galaxy population, and span all dynamical ages; merger-driven bulges in disk galaxies are dynamically old and do not interfere with subsequent evolution of the star-forming component. Instability-driven bulges dominate the population at intermediate galaxy masses, especially thriving in massive disks. The model green valley is exclusively populated by instability-driven bulge hosts. Through the present implementation the mass accretion history is perceivable in the galaxy structure, morphology and colours.

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The role of dissipation in the scaling relations of cosmological merger remnants

Cited by 43 publications

References 83 publications

How do minor mergers promote inside-out growth of ellipticals, transforming the size, density profile and dark matter fraction?

How do minor mergers promote inside-out growth of ellipticals, transforming the size, density profile and dark matter fraction?

CANDELS: THE PROGENITORS OF COMPACT QUIESCENT GALAXIES ATz∼ 2

The growth of discs and bulges during hierarchical galaxy formation – I. Fast evolution versus secular processes

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