Galaxy formation as a cosmological tool – I. The galaxy merger history as a measure of cosmological parameters

Abstract

As galaxy formation and evolution over long cosmic time-scales depends to a large degree on the structure of the universe, the assembly history of galaxies is potentially a powerful approach for learning about the universe itself. In this paper we examine the merger history of dark matter halos based on the Extended Press-Schechter formalism as a function of cosmological parameters, redshift and halo mass. We calculate how major halo mergers are influenced by changes in the cosmological values of Ω m , Ω Λ , σ 8 , the dark matter particle temperature (warm vs. cold dark matter), and the value of a constant and evolving equation of state parameter w(z). We find that the merger fraction at a given halo mass varies by up to a factor of three for halos forming under the assumption of Cold Dark Matter, within different underling cosmological parameters. We find that the current measurements of the merger history, as measured through observed galaxy pairs as well as through structure, are in agreement with the concordance cosmology with the current best fit giving 1 − Ω m = Ω Λ = 0.84 +0.16 −0.17 . To obtain a more accurate constraint competitive with recently measured cosmological parameters from Planck and WMAP requires a measured merger accuracy of δf m ∼ 0.01, implying surveys with an accurately measured merger history over 2 -20 deg 2 , which will be feasible with the next generation of imaging and spectroscopic surveys such as Euclid and LSST.

Galaxy morphological classification in deep-wide surveys via unsupervised machine learning

“…Conselice et al 2008;Vulcani et al 2011) As shown in previous work (e.g. Conselice et al 2008;Ilbert et al 2010;Conselice et al 2014), there is a general trend for elliptical and S0/Sa fractions at a given stellar mass to increase towards lower redshifts. These systems increasingly dominate the number density at high stellar masses towards the present day (e.g.…”

Feedback and Feeding in the Context of Galaxy Evolution withSPICA: Direct Characterisation of Molecular Outflows and Inflows

“…While in the local Universe the most powerful molecular outflows are observed in AGN-dominated merger ULIRGs, analysis of deep Hubble fields based on structural parameters indicate a merger fraction of massive (> 10 10 M ⊙ ) galaxies increasing with redshift up to 10% at z = 1.2, implying that a typical present-day massive galaxy has undergone ∼ 1 major merger during the last ∼ 9 Gyr (Conselice et al 2009;Robaina et al 2010;Xu et al 2012). This merging rate is capable of explaining the build-up of the red sequence during the last ∼ 8 Gyr (Eliche-Moral et al 2010;Xu et al 2012;Prieto et al 2013), and it is in general concordance with the ΛCDM galaxy mass assembly model (Conselice et al 2014) 3 . Alternatively, smooth cold mode accretion of intergalactic gas, which is expected from simulations to be the main gas supply for star formation over cosmic times (e.g.…”

Selection bias in dynamically measured supermassive black hole samples: consequences for pulsar timing arrays

“…We also explore four different differential pair fractions (PFs) = (df /dq)M,z, extracted from (Bundy et al 2009;de Ravel et al 2009;López-Sanjuan et al 2012;Xu et al 2012) following the same procedure as in S13 (see also detailed description in Gerosa & Sesana 2015). We checked that those broadly match recent compilations of galaxy PFs from, e.g, Conselice et al (2014). Considering different MFs and PFs helps in folding into our computation possible systematic errors due to the specific samples and techniques adopted in each work.…”