Galactosynthesis: halo histories, star formation and discs

Abstract

A B S T R A C TWe investigate the effects of a variety of ingredients that must enter into a realistic model for disc galaxy formation, focusing primarily on the Tully±Fisher (TF) relation and its scatter in several wavebands. In particular, we employ analytic distributions for halo formation redshifts and halo spins, empirical star formation rates and initial mass functions, realistic stellar populations, and chemical evolution of the gas. Our main findings are as follows. (a) The slope, normalization and scatter of the TF relation across various wavebands are determined largely by the parent halo properties as dictated by the initial conditions, but are also influenced by star formation in the disc. (b) TF scatter in this model is due primarily to the spread in formation redshifts. The scatter can be measurably reduced by chemical evolution, and also by the weak anticorrelation between peak height and spin. (c) Multiwavelength constraints can be important in distinguishing between models that appear to fit the TF relation in I or K. (d) Assuming passive disc evolution, successful models seem to require that the bulk of disc formation cannot occur too early z . 2±3 or too late z , 0X2Y and are inconsistent with high values of V 0 . (e) A simple, realistic model with the above ingredients, and fewer free parameters than typical semi-analytic models, can reasonably reproduce the observed z 0 TF relation in all bands (B, R, I and K), as well as the observed B-band surface brightness±magnitude relation. In such a model, the nearinfrared TF relation at z 1 is similar to that at z 0Y while bluer bands show a markedly steeper TF slope at high redshift, consistent with limited current data. The remarkable agreement with observations suggests that the amount of gas that is expelled or poured into a disc galaxy may be small (though small fluctuations might serve to align B-band predictions better with observations), and that the specific angular momentum of the baryons should roughly equal that of the halo; there is little room for angular momentum transfer. In Appendix A we present analytic fits to stellar population synthesis models.

Dynamical properties of a large young disk galaxy atz= 2.03

“…This nonevolution in near-IR z = 1 TFR was predicted by Buchalter et al (2001) and in the stellar mass z = 1 TFR by Portinari & Sommer-Larsen (2007). Our findings suggest that the K band TFR may not evolve out to redshift 2.…”

The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies

“…Given the distributions of halo spin parameters and of halo virial radii R vir , the implied distribution of disk scale lengths is in excellent agreement with observations (e.g., Dalcanton, Spergel, & Summers 1997;Mo, Mao, & White 1998;de Jong & Lacey 2000). This success has prompted many detailed studies of disk galaxy formation, always under the three assumptions listed above (van den Bosch 1998(van den Bosch , 2000(van den Bosch , 2002Jimenez et al 1998;Natarajan 1999;Heavens & Jimenez 1999;Buchalter, Jimenez, & Kamionkowski 2001). The standard picture of disk formation that has emerged from these studies has been remarkably successful in explaining a wide variety of observational properties of disk galaxies.…”

Scaling Relations of Spiral Galaxies

“…Besides the basic understanding of the slopes of galaxy scaling relations, the dependence of their scatter has also been addressed by many, especially for the VL relation (e.g., Aaronson & Mould 1983;Giraud 1986;Rhee 1996;Willick et al 1997;KFF02;Courteau et al 2003), and can be used to set realistic constraints on structure formation models (Courteau & Rix 1999, hereafter CR99;Heavens & Jimenez 1999;FAR00;NS00;V01;Buchalter et al 2001;Shen et al 2002;Gnedin et al 2006;D07). While various trends in the scatter of the blue VL relation have been discussed in the past, correlations of the near-infrared VL residuals with inclination, size, concentration, gas fraction, or farinfrared luminosity are few and inconclusive (Aaronson & Mould 1983;V01;P07).…”