The evolution of disk galaxies

We study the evolution of disk galaxies using galaxy evolutionary models with initial and boundary conditions linked to the hierarchical formation scenario. Disks galaxies are modeled locally within growing cold dark matter halos and including a physical model for star formation. We focus our attention on predictions of the star formation history, size and surface brightness evolution and the evolution of the H- and B-band Tully-Fisher relations. Comparisons with available observational data are presented.Comment: To appear in "The Seventh Texas-Mexico Conference on Astrophysics: Flows, Blows, and Glows," eds. W. Lee & S. Torres-Peimbert, RevMexAA (Serie de Conferencias), in press (2000). 4 pages, 1 figur

On the Formation of Bulges and Elliptical Galaxies in the Cosmological Context

We study the formation of hot spheroidal systems within the frame of a scenario where galaxy formation and evolution is related to the gentle mass aggregation history and primordial angular momentum of protogalaxies, both defined by the cosmological initial conditions. We explore two cases: (1) the hot spheroidal system forms from the dynamical instabilities of the stellar disks, and (2) the spheroidal systems are formed during the dissipative collapse of the gas before falling to the disk in centrifugal equilibrium. In the former case a good agreement with observations for late type galaxies is found. In the second case, contrary to recent claims, we find that the tidal stability criterion is not easily reached. The gas that dissipatively collapses within the dark matter halos should be very clumpy, and the clumps very dense, in order to avoid the tidal destruction of the star formation unities.Comment: to appear in "Star Formation in Early-Type Galaxies", ASP Conf. Ser., eds. P. Carral & J. Cepa, paspconf.sty, LaTeX, 7 pages, 2 figure

Structure, dynamics and evolution of disk galaxies in a hierarchical formation scenario

Using galaxy evolutionary models in a hierarchical formation scenario, we predict the structure, dynamics and evolution of disk galaxies in a LCDM universe. Our models include star formation and hydrodynamics of the ISM. We find that the Tully-Fisher relation (TFR) in the I and H bands is an imprint of the mass-velocity relation of the cosmological dark halos. The scatter of the TFR originates mainly from the scatter in the dark halo structure and, to a minor extension, from the dispersion of the primordial spin parameter lambda. Our models allow us to explain why low and high surface brightness galaxies have the same TFR. The disk gas fractions predicted agree with the observations. The disks formed within the growing halos have nearly exponential surface brightness and flat rotation curves. Towards high redshifts, the zero-point of the TFR in the H band increases while in the B-band it slightly decreases.Comment: 3 pages, uses newpasp.sty, to appear in "Galaxy Dynamics from the Early Universe to the Present", ASP Conf. Series, F. Combes, G. Mamon & V. Charmandaris, ed

On the origin of the color Tully-Fisher and color-magnitude relations of disk galaxies

We propose and show that the dependence of the internal face-on dust absorption upon B-band luminosity reported by Wang & Heckman (1996) for a sample of late-type galaxies may explain the empirical color-magnitude and color Tully-Fisher relations of disk galaxies. Thus, in order to explain these relations, it is not necessary to evoke star formation and gas infall efficiencies dependent on the mass of the galaxy system. After applying the Wang & Heckman's luminosity-dependent extinction to hierarchical inside-out galaxy formation and evolution models where the star formation and gas infall efficiencies do not significantly depend on mass, we succesfully predict the observed Tully-Fisher relations in the H and B bands as well as the color-magnitude relation.Comment: 1 page. To appear in ``Cosmic Evolution and Galaxy Formation: Structure, Interactions and Feedback'', Eds. J.Franco, E.Terlevich, O.Lopez-Cruz, I.Aretxaga, ASP Conf. Serie

Physical processes behind the morphological Hubble sequence

The study of formation and evolution of galaxies is reviewed, making emphasis on the physical factors which are important to understand the origin of the galaxy Hubble sequence. We concentrate on predictions of the hierarchical Cold Dark Matter (CDM) scenario and the confrontation with observations. The mass assembling of the CDM halos, the baryonic processes within them, and the evolution of disks and spheroids are described. The successes and shortcomings are discussed. Disk evolution seems to be a quiescent and extended process driven by the cosmological initial conditions, while spheroids are formed probably in violent events, where several astrophysical processes are competing.Comment: 14 pages, 3 figures. Review paper to appear in "Galaxy Evolution: Theory and Observations", eds. V. Avila-Reese, C. Firmani, C. Frenk, & C. Allen, RevMexAA (SC), 17. Minor changes, references adde

Dark Halos and Galaxy Evolution

We study the evolution of disk galaxies within the frame of the cold dark matter (CDM) cosmologies. The hydrodynamics of a centrifugally supported gaseous disk and the growth of a stellar disk are calculated in detail taking into account the energy balance of the ISM and the gravitational instabilities that concern gas and stars. The halo density profile is derived from the primordial cosmological conditions and its gravitational contraction produced by the disk is included. Several features of the spiral galaxies at different redshifts are predicted, and the main factors which influence on these features are found. A strong evidence is provided that the Tully-Fisher relation is an imprint of the primordial cosmological conditions.Comment: 8 pages, 6 eps figures, uses iopconf1.sty. To appear in proceedings of the Second International Workshop on Dark Matter in Astro and Particle Physics, eds. H.V.Klapdor-Kleingrothaus and L.Baudi

Properties and evolution of disk galaxies in a hierarchical formation scenario

We highlight some results from disk galaxy evolution models conceived within a cosmological context. When disk mergers and strong disk-halo feedback are omitted, several properties and correlations of disk galaxies seem to be related to initial conditions given by the CDM model, for example, the intensive galaxy properties, the disk Hubble sequence, and the Tully-Fisher relation in the infrared bands.Comment: 2 pages, to appear in "Galaxy Disks and Disk Galaxies," eds. J. G. Funes & E. M. Corsini (ASP Conference Series

Properties of disk galaxies in a hierarchical formation scenario

We used galaxy evolutionary models in a hierarchical inside-out formation scenario to study the origin of the main properties and correlations of disk galaxies. We found that most of these properties and correlations are the result of three (cosmological) initial factors and their dispersions: the virial mass, the halo mass aggregation history (MAH), and the angular momentum given through the spin parameter \lambda. The MAH determines mainly the halo structure and the color indexes while \lambda determines mainly the surface brightness and the bulge-to-disk ratio. We calculated star formation (SF) using a gravitational instability criterion and a self-regulation mechanism in the turbulent ISM. The efficiency of SF in this model is almost independent from the mass. We show that the luminosity-dependent dust absorption empirically determined by Wang & Heckman explains the observed color-magnitude and color Tully-Fisher (TF) relations without the necessity of introducing a mass-dependent SF efficiency. The disks in centrifugal equilibrium form within growing CDM halos with a gas accretion rate proportional to the MAH. The disks present exponential surface density and brightness profiles, negative radial color index gradients, and nearly flat rotation curves. We also calculated the secular formation of a bulge due to gravitational instabilities in the stellar disk. The intensive properties of our models agree with the observational data and the trends of the Hubble sequence are reproduced. The predicted infrared TF and luminosity-radius relations also agree with observations. The main shortcomings of our inside-out hierarchical models are the excessive radial color gradients and the dark halo dominion in the rotation curve decompositions.Comment: 24 pages, includes figures, uses rmaa.cls. Accepted for publication in RevMexAA, Vol. 36, No. 1 (April 2000

Disk galaxy formation and evolution: models up to intermediate redshifts

Making use of a seminumerical method we develop a scenario of disk galaxy formation and evolution in the framework of inflationary cold dark matter (CDM) cosmologies. Within the virializing dark matter halos, disks in centrifugal equilibrium are built-up and their galactic evolution is followed through an approach which considers the gravitational interactions among the galaxy components, the turbulence and energy balance of the ISM, the star formation (SF) process due to disk gravitational instabilities, the stellar evolution and the secular formation of a bulge. We find that the main properties and correlations of disk galaxies are determined by the mass, the hierarchical mass aggregation history and the primordial angular momentum. The models follow the same trends across the Hubble sequence than the observed galaxies. The predicted TF relation is in good agreement with the observations except for the standart CDM. While the slope of this relation remains almost constant up to intermediate redshifts, its zero-point decreases in the H-band and slightly increases in the B-band. A maximum in the SF rate for most of the models is attained at $z\sim 1.5-2.5$.Comment: 12 pages, 11 eps figures, uses paspconf.sty. To appear in 'Observational Cosmology: The Development of Galaxy Systems', eds. G.Giuricin, M.Mezzetti and P.Salucci, ASP Conf. Serie

Modelling Self-Interacting CDM Haloes with a Cosmological Boltzmann Code

We investigate the density profiles and evolution of weakly self-interacting cold dark matter haloes using a numerical code based on the collisional Boltzmann equation. This approach is alternative to N-body techniques in following the dynamical evolution of haloes in the cosmological context and taking into account particle self-interaction. The physical case with a cross section inversely proportional to the relative velocity of the colliding particles is modelled with an unprecedented resolution, spanning five orders of magnitude on the radius for each halo. The modelled haloes cover a mass range from dwarf galaxies to galaxy clusters. We find that for \sigma v_{100} \approx 10^{-24} cm^2/GeV, where \sigma is the cross section per unit mass and v_{100} is the collision velocity in units of 100 km/s, soft cores in good agreement with observations on galactic as well as on galaxy cluster scales are obtained. Remarkably, the observed nearly invariance of the halo central density with mass is reproduced.Comment: Submitted to MNRAS (September, 18). 5 pages, 4 figure