In my current research, I aim to better understand the formation and evolution of galaxies in the framework of the standard cosmological model, i.e., a Λ Cold Dark Matter Universe. In particular, I am passionate about the complex interplay between the baryonic physics of galaxies and the assembly of their host dark matter halos across cosmic time. I investigate the role of dark matter halos and their large-scale environment in shaping the stellar content of galaxies by combining detailed stellar population measurements with different halo characterizations and environmental metrics.
Baryonic properties across the
stellar-to-total dynamical mass relation
Scholz-Díaz, L.; Martín-Navarro, I; Falcón-Barroso, J; et al.
In the standard cosmological model, the assembly of galaxies is primarily driven by the growth of their host dark matter halos. At the center of these halos, however, baryonic processes take over, leading to the plethora of observed galaxy properties. The coupling between baryonic and dark matter physics is central to our understanding of galaxies and yet, it remains a challenge for theoretical models and observations. Here, we demonstrate that measured ages, metallicities, stellar angular momentum, morphology and star formation rates, correlate with both stellar and halo mass. Using dynamical modeling, we find that at fixed stellar mass, CALIFA galaxies become younger, more metal-poor and rotationally supported, have higher star formation rates and later-type morphologies as their total mass increases, with independent stellar and total masses measurements. These results indicate that the formation of galaxies and thus their baryonic properties do not vary with stellar mass alone, with halo mass also playing an important role.
Nat. Astron, 8, 648
The dark side of galaxy stellar populations II: The dependence on halo mass and on the scatter of the main sequence
Scholz-Díaz, L.; Martín-Navarro, I; Falcón-Barroso, J
Nearby galaxies are the end result of their cosmological evolution, which is predicted to be influenced by the growth of their host dark matter haloes. This co-evolution potentially leaves signatures in present-day observed galaxy properties, which might be essential to further understand how the growth and properties of galaxies are connected to those of their host haloes. In this work, we study the evolutionary histories of nearby galaxies both in terms of their host haloes and the scatter of the star-forming main sequence by investigating their time-resolved stellar populations using absorption optical spectra drawn from the Sloan Digital Sky Survey. We find that galaxy star-formation histories depend on the masses of their host haloes, and hence they shape the evolution of the star-forming main sequence over cosmic time. Additionally, we also find that the scatter around the z = 0 star-forming main sequence is not (entirely) stochastic, as galaxies with currently different star-formation rates have experienced, on average, different star-formation histories. Our findings suggest that dark matter haloes might play a key role in modulating the evolution of star formation in galaxies, and thus of the main sequence, and further demonstrate that galaxies at different evolutionary stages contribute to the observed scatter of this relation.
MNRAS, 518, 6325
The dark side of galaxy stellar populations I: The stellar-to-halo mass relation and the velocity dispersion - halo mass relation
Scholz-Díaz, L.; Martín-Navarro, I; Falcón-Barroso, J
The growth and properties of galaxies are thought to be closely connected to the ones of their host dark matter halos. Despite the importance of this so-called galaxy-halo connection, the potential role of dark matter halos in regulating observed galaxy properties remains yet to be fully understood. In this work, we derive the ages, metallicites and [Mg/Fe] abundances from optical spectra from the Sloan Digital Sky Survey of nearby central galaxies, and study them in terms of their host halos. We investigate how the scatter in the stellar-to-halo mass relation and the velocity dispersion - halo mass relation correlates with these stellar population parameters. In addition, we also study the differences when distinguishing between different galaxy morphologies and environments. We find that the ages and chemical enrichment of galaxies are not fully determined by their stellar masses or velocity dispersion, but also depend on the mass of the host halos. Our findings suggest that the velocity dispersion is the best proxy of the stellar population parameters with halo mass playing a secondary yet noticeable role. We interpret that the origin of the correlation between the scatter of these relations and the ages and metallicities might be related to different halo formation times.
MNRAS, 511, 4900
History of the gas fuelling star formation in EAGLE galaxies
Scholz-Díaz, L.; Sánchez Almeida, J.; Dalla Vecchia, C.
Theory predicts that cosmological gas accretion plays a fundamental role fuelling star formation in galaxies. However, a detailed description of the accretion process to be used when interpreting observations is still lacking. Using the state-of-the-art cosmological hydrodynamical simulation EAGLE, we work out the chemical inhomogeneities arising in the disk of galaxies due to the randomness of the accretion process. In low-mass systems and outskirts of massive galaxies, low metallicity regions are associated with enhanced star-formation, a trend that reverses in the centers of massive galaxies. These predictions agree with the relation between surface density of star formation rate and metallicity observed in the local spiral galaxies from the MaNGA survey. Then, we analyse the origin of the gas that produces stars at two key epochs, z = 0 and z = 2. The main contribution comes from gas already in the galaxy about 1 Gyr before stars are formed, with a share from external gas that is larger at high redshift. The accreted gas may come from major and minor mergers, but also as gravitationally unbound gas and from mergers with dark galaxies (i.e., haloes where more than 95 % of the baryon mass is in gas). We give the relative contribution of these sources of gas as a function of stellar mass (8 < log Mstar < 11). Even at z = 0, some low-mass galaxies form a significant fraction of their total stellar mass during the last Gyr from mergers with dark galaxies.
MNRAS, 505, 4655
