The imprint of dark matter haloes on the size and velocity dispersion evolution of early-type galaxies. Issue 1 (12th March 2014)

• Record Type: Journal Article
• Authors: Posti, Lorenzo; Nipoti, Carlo; Stiavelli, Massimo; Ciotti, Luca
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 440:Issue 1(2014)
• Page Start: 610
• Page End: 623
• Publication Date: 2014-03-12
• Subjects: galaxies: evolution -- galaxies: formation -- galaxies: haloes -- dark matter; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stu301
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: Early-type galaxies (ETGs) are observed to be more compact, on average, at z ≳ 2 than at z ≃ 0, at fixed stellar mass. Recent observational works suggest that such size evolution could reflect the similar evolution of the host dark matter halo density as a function of the time of galaxy quenching. We explore this hypothesis by studying the distribution of halo central velocity dispersion (σ0 ) and half-mass radius ( r h ) as functions of halo mass M and redshift z, in a cosmological Λ cold dark matter N -body simulation. In the range 0 ≲ z ≲ 2.5, we find σ0 ∝ M 0.31-0.37 and r h ∝ M 0.28-0.32, close to the values expected for homologous virialized systems. At fixed M in the range 10 11 M⊙ ≲ M ≲ 5.5 × 10 14 M⊙ we find σ0 ∝ (1 + z ) 0.35 and r h ∝ (1 + z ) −0.7 . We show that such evolution of the halo scaling laws is driven by individual haloes growing in mass following the evolutionary tracks σ0 ∝ M 0.2 and r h ∝ M 0.6, consistent with simple dissipationless merging models in which the encounter orbital energy is accounted for. We compare the N -body data with ETGs observed at 0 ≲ z ≲ 3 by populating the haloes with a stellar component under simple but justified assumptions: the resulting galaxies evolve consistently with the observed ETGs up to z ≃ 2, but the model has difficulty in reproducing the fast evolution observed at z ≳ 2. We conclude that a substantial fraction of the size evolution of ETGs can be ascribed to a systematic dependence on redshift of the dark matter haloes structural properties.