Abstract:

We analyse the evolutionary history of galaxies formed in a hierarchical scenario consistent with the concordance Lambda cold dark matter (CDM) model focusing on the study of the relation between their chemical and dynamical properties. Our simulations consistently describe the formation of the structure and its chemical enrichment within a cosmological context. Our results indicate that the luminosity–metallicity and the stellar mass–metallicity (LZR and MZR) relations are naturally generated in a hierarchical scenario. Both relations are found to evolve with redshift. In the case of the MZR, the estimated evolution is weaker than that deduced from observational works by approximately 0.10 dex. We also determine a characteristic stellar mass, Mc ≈ 3 × 1010 M⊙, which segregates the simulated galaxy population into two distinctive groups and which remains unchanged since z ∼ 3, with a very weak evolution of its metallicity content. The value and role played by Mc is consistent with the characteristic mass estimated from the SDSS galaxy survey by Kauffmann et al. Our findings suggest that systems with stellar masses smaller than Mc are responsible for the evolution of this relation at least from z ≈ 3. Larger systems are stellar dominated and have formed more than 50 per cent of their stars at z 2, showing very weak evolution since this epoch. We also found bimodal metallicity and age distributions from z ∼ 3, which reflects the existence of two different galaxy populations. Although SN feedback may affect the properties of galaxies and help to shape the MZR, it is unlikely that it will significantly modify Mc since, from z = 3 this stellar mass is found in systems with circular velocities larger than 100 km s −1

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Tissera, Patricia Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Scannapieco, Cecilia. Gobierno de la Republica Federal de Alemania. Max Planck Institut Fur Astrophysik; Alemania. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Abstract:

We study the contribution of the first galaxies to the far-infrared/sub-millimeter (FIR/sub-mm) extragalactic background light (EBL) by implementing an analytical model for dust emission. We explore different dust models, assuming different grain size distributions and chemical compositions. According to our findings, observed re-radiated emission from dust in dwarf-size galaxies at z~10 would peak at a wavelength of 500μm with observed fluxes of 10^(-3)− 10^(−2) nJy, which is below the capabilities of current observatories. In order to be detectable, model sources at these high redshifts should exhibit luminosities of >10^(12) L_sun, comparable to that of local ultra-luminous systems. The FIR/sub-mm EBL generated by primeval galaxies peaks at 500μm, with an intensity ranging from 10^(−4) to 10^(−3) nW m^(−2) sr^(−1), depending on dust properties. These values are ~ 3 − 4 orders of magnitude below the absolute measured cosmic background level, suggesting that the first galaxies would not contribute significantly to the observed FIR/sub-mm EBL. Our model EBL exhibits a strong correlation with the dust-to-metal ratio, where we assume a fiducial value of D = 0.005, increasing almost proportionally to it. Thus, measurements of the FIR/sub-mm EBL could provide constraints on the amount of dust in the early Universe. Even if the absolute signal from primeval dust emission may be undetectable, it might still be possible to obtain information about it by exploring angular fluctuations at 500μm, close to the peak of dust emission from the first galaxies.

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Bromm, Volker. University Of Texas At Austin; Estados Unidos

Abstract:

In this work, we show that when supernova Ia (SN Ia) data sets are used to put constraints on the free parameters of inhomogeneous models, certain extra information regarding the light-curve fitter used in the supernovae Ia luminosity fluxes processing should be taken into account. We found that the size of the void as well as other parameters of these models might be suffering extra degenerations or additional systematic errors due to the fitter. A recent proposal to relieve the tension between the results from Planck satellite and SNe Ia is re-analyzed in the framework of these subjects.

Author affiliation: Bengochea, Gabriel Roman. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Abstract:

We study the mass–metallicity relation of galactic systems with stellar masses larger than 109M⊙h−1 in Λ cold dark matter scenarios by using chemical hydrodynamical simulations. We find that this relation arises naturally as a consequence of the formation of the structure in a hierarchical scenario. The hierarchical building-up of the structure determines a characteristic stellar mass at Mc≈ 1010.2M⊙h−1 which exhibits approximately solar metallicities from z≈ 3 to z= 0. This characteristic mass separates galactic systems into two groups with massive ones forming most of their stars and metals at high redshift. We find evolution in the zero point and slope of the mass–metallicity relation driven mainly by the low-mass systems which exhibit the larger variations in the chemical properties. Although stellar mass and circular velocity are directly related, the correlation between circular velocity and metallicity shows a larger evolution with redshift because of the combination of chemical evolution and cosmology. The dispersion found in both relations is a function of the stellar mass and reflects the different dynamical history of evolution of the systems.

Author affiliation: Tissera, Patricia Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Scannapieco, Cecilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Abstract:

We analyse a sample of 52 000 Milky Way (MW) type galaxies drawn from the publicly available galaxy catalogue of the Millennium Simulation with the aim of studying statistically the differences and similarities of their properties in comparison to our Galaxy. Model galaxies are chosen to lie in haloes with maximum circular velocities in the range 200–250 km s−1 and to have bulge-to-disc ratios similar to that of the MW. We find that model MW galaxies formed ‘quietly’ through the accretion of cold gas and small satellite systems. Only ≈12 per cent of our model galaxies experienced a major merger during their lifetime. Most of the stars formed ‘in situ’, with only about 15 per cent of the final mass gathered through accretion. Supernovae (SNe) and active galactic nuclei (AGN) feedback play an important role in the evolution of these systems. At high redshifts, when the potential wells of the MW progenitors are shallower, winds driven by SNe explosions blow out a large fraction of the gas and metals. As the systems grow in mass, SNe feedback effects decrease and AGN feedback takes over, playing a more important role in the regulation of the star formation activity at lower redshifts. Although model MW galaxies have been selected to lie in a narrow range of maximum circular velocities, they nevertheless exhibit a significant dispersion in the final stellar masses and metallicities. Our analysis suggests that this dispersion results from the different accretion histories of the parent dark matter haloes. Statistically, we also find evidences to support the MW as a typical Sb/Sc galaxy in the same mass range, providing a suitable benchmark to constrain numerical models of galaxy formation.

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Tissera, Patricia Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: De Lucia, Gabriella. Max-Planck-Institut fur Astrophysik,; Alemania

Author affiliation: Kauffmann, Guinevere. Max-Planck-Institut fur Astrophysik; Alemania

Abstract:

The evolution of the metal content of galaxies and its relations to other global properties [such as total stellar mass (M*), circular velocity, star formation rate (SFR), halo mass, etc.] provides important constraints on models of galaxy formation. Here we examine the evolution of metallicity scaling relations of simulated galaxies in the Galaxies-Intergalactic Medium Interaction Calculation suite of cosmological simulations. We make comparisons to observations of the correlation of gas-phase abundances with M* (the mass-metallicity relation, MZR), as well as with both M* and SFR or gas mass fraction (the so-called 3D fundamental metallicity relations, FMRs). The simulated galaxies follow the observed local MZR and FMRs over an order of magnitude in M*, but overpredict the metallicity of massive galaxies (log M* > 10.5), plausibly due to inefficient feedback in this regime. We discuss the origin of the MZR and FMRs in the context of galactic outflows and gas accretion. We examine the evolution of mass-metallicity relations defined using different elements that probe the three enrichment channels (SNII, SNIa, and AGB stars). Relations based on elements produced mainly by SNII evolve weakly, whereas those based on elements produced preferentially in SNIa/AGB exhibit stronger evolution, due to the longer timescales associated with these channels. Finally, we compare the relations of central and satellite galaxies, finding systematically higher metallicities for satellites, as observed. We show this is due to the removal of the metal poor gas reservoir that normally surrounds galaxies and acts to dilute their gas-phase metallicity (via cooling/accretion onto the disk), but is lost due to ram pressure stripping for satellites.

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Theuns, T.. University Of Durham. Dep.of Physics; Reino Unido

Author affiliation: Font, A. S.. John Moores University; Reino Unido

Author affiliation: Mccarthy, I. G.. John Moores University; Reino Unido

Abstract:

We developed a Monte Carlo code to generate long-duration gamma-ray burst (LGRB) events within cosmological hydrodynamical simulations consistent with the concordance Λ cold dark matter model. As structure is assembled, LGRBs are generated in the substructure that formed galaxies today. We adopted the collapsar model so that LGRBs are produced by single, massive stars at the final stage of their evolution. We found that the observed properties of the LGRB host galaxies (HGs) are reproduced if LGRBs are also required to be generated by low-metallicity stars. The low-metallicity condition imposed on the progenitor stars of LGRBs selects a sample of HGs with mean gas abundances of 12 + log O/H ~ 8.6. For z < 1 the simulated HGs of low-metallicity LGRB progenitors tend to be faint, slow rotators with high star formation efficiency, compared with the general galaxy population, in agreement with observations. At higher redshift, our results suggest that larger systems with high star formation activity could also contribute to the generation of LGRBs from low-metallicity progenitors since the fraction of low-metallicity gas available for star formation increases for all systems with look-back time. Under the hypothesis of our LGRB model, our results support the claim that LGRBs could be unbiased tracers of star formation at high redshifts.

Author affiliation: Nuza, Sebastian Ernesto. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Tissera, Patricia Beatriz. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Pellizza González, Leonardo Javier. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: Garcia Lambas, Diego Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomia Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomia Teórica y Experimental; Argentina

Author affiliation: Scannapieco, Cecilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Author affiliation: de Rossi, Maria Emilia. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina