The other side of Bulge Formation in a Lambda-CDM cosmology: Bulgeless Galaxies in the Local Universe

Abstract

We study the physical properties, formation histories, and environment of galaxies without a significant "classical" spheroidal component, as predicted by semi-analytical models of galaxy formation and evolution. This work is complementary to the analysis presented in De Lucia et al., (2011), where we focus on the relative contribution of various physical mechanisms responsible for bulge assembly in a Lambda-CDM cosmology. We find that the fraction of bulgeless galaxies is a strong decreasing function of stellar mass: they represent a negligible fraction of the galaxy population with M* > 10^12 Msun, but dominate at M* < 10^10 Msun. We find a clear dichotomy in this galaxy population, between central galaxies of low-mass dark matter haloes, and satellite galaxies in massive groups/clusters. We show that bulgeless galaxies are relatively young systems, that assemble most of their mass at low-redshift, but they can also host very old stellar populations. Since galaxy-galaxy mergers are assumed to lead to the formation of a spheroidal component, in our models these galaxies form preferentially in low-mass haloes that host a small number of satellites galaxies. We show that the adopted modelling for galaxy mergers represents a key ingredient in determining the actual number of bulgeless galaxies. Our results show that these galaxies are not a rare population in theoretical models: at z~0, galaxies with no classical bulge (but often including galaxies with the equivalent of pseudo-bulges) account for up to 14% of the galaxies with 10^11 < M*/Msun < 10^12.

Accepted for publication in MNRAS; updated version with additional comparisons with observations

References in corpus (11)

• Structural Properties of Pseudo-Bulges, Classical Bulges and Elliptical Galaxies: an SDSS Perspective
• Bulgeless Giant Galaxies Challenge our Picture of Galaxy Formation by Hierarchical Clustering
• The MORGANA model for the rise of galaxies and active nuclei
• The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach
• Properties of Bars and Bulges in the Hubble Sequence
• Demographics of Bulge Types within 11 Mpc and Implications for Galaxy Evolution
• The Dependence of Galaxy Formation on Cosmological Parameters: Can we distinguish the WMAP1 and WMAP3 Parameter Sets?
• Times, environments and channels of bulge formation in a LambdaCDM cosmology
• How galaxies lose their angular momentum
• The Millennium Galaxy Catalogue: Exploring the Color-Concentration Bimodality via Bulge-Disc Decomposition
• The UK Infrared Telescope M33 monitoring project. II. The star formation history in the central square kiloparsec

Cited by in corpus (4)

• Galaxy Zoo DECaLS: Detailed Visual Morphology Measurements from Volunteers and Deep Learning for 314,000 Galaxies
• The growth of disks and bulges during hierarchical galaxy formation. I: fast evolution vs secular processes
• Bulgeless galaxies in the COSMOS field: environment and star formation evolution at $z<1$
• Can AI Dream of Unseen Galaxies? Conditional Diffusion Model for Galaxy Morphology Augmentation