According to the current galaxy-formation paradigm, mergers and interactions play an important ro... more According to the current galaxy-formation paradigm, mergers and interactions play an important role in shaping present-day galaxies. The remnants of this merger activity can be used to constrain galaxy-formation models. In this work, we use a sample of 30 hydrodynamical simulations of Milky Way mass haloes, from the AURIGA project, to generate surface brightness maps and search for the brightest stream in each halo as a function of varying limiting magnitude. We find that none of the models shows signatures of stellar streams at $\mu _{r}^{\lim} \le 25$ mag arcsec−2. The stream detection increases significantly between 28 and 29 mag arcsec−2. Nevertheless, even at 31 mag arcsec−2, 13 per cent of our models show no detectable streams. We study the properties of the brightest streams progenitors (BSPs). We find that BSPs are accreted within a broad range of infall times, from 1.6 to 10 Gyr ago, with only 25 per cent accreted within the last 5 Gyrs; thus, most BSPs correspond to relati...
We explore a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in ... more We explore a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in simulations that form boxy/peanut (b/p) bulges. The morphology of bars and b/p’s vary for different mono-abundance populations, according to their kinematic properties, which are in turn set by the galaxy’s assembly history. We find that the Auriga galaxies which best reproduce the chemo-kinematic properties of the Milky Way bulge have a negligible fraction of ex-situ stars in the b/p region (< 1%), with flattened, thick disc-like metal-poor stellar populations, and with their last major merger occurring at tlookback > 12 Gyrs. This imposes an upper limit on the stellar mass ratio of subsequent mergers, which we find is broadly consistent with the recently proposed Gaia Sausage/Enceladus merger. The average fraction of ex-situ stars in the central regions of Auriga galaxies that form b/p’s is 3% – significantly lower than in those which do not form bars or b/p’s. While these centra...
Monthly Notices of the Royal Astronomical Society, 2021
ABSTRACTWe present a model to track the orbital evolution of ‘unresolved subhaloes’ (USHs) in cos... more ABSTRACTWe present a model to track the orbital evolution of ‘unresolved subhaloes’ (USHs) in cosmological simulations. USHs are subhaloes that are no longer distinguished by halo finders as self-bound overdensities within their larger host system due to limited mass resolution. These subhaloes would host ‘orphan galaxies’ in semi-analytic models of galaxy formation and evolution (SAMs). Predicting the evolution of the phase-space components of USHs is crucial for the adequate modelling of environmental processes, interactions, and mergers implemented in SAMs that affect the baryonic properties of orphan satellites. Our model takes into account dynamical friction drag, mass-loss by tidal stripping and merger with the host halo, involving three free parameters. To calibrate this model, we consider two DM-only simulations of different mass resolution (MultiDark simulations). The simulation with higher mass resolution (smdpl; $m_{\rm DM} = 9.6 \times 10^7\, h^{-1}\, \mathrm{M_{\odot }}...
Wepresent an updatedmodel for the evolution of the orbits of "orphan galaxies" to be us... more Wepresent an updatedmodel for the evolution of the orbits of "orphan galaxies" to be used in the SAG semi-analytical model of galaxy formation and evolution. In cosmological simulations, orphan galaxies are those satellite galaxies for which, due to limited mass resolution, halo finders lose track of their dark matter subhalos and can no longer be distinguished as selfbound overdensities within the larger host system. Since the evolution of orphans depends strongly on the orbit they describe within their host halo, a proper treatment of their evolution is crucial in predicting the distribution of subhalos and satellite galaxies. The model proposed takes into account the dynamical friction drag, mass loss by tidal stripping and a proximity merger criterion, also it is simple enough to be inexpensive from a computational point of view. To calibrate this model, we apply it onto a dark matter only simulation and compare the results with a high resolution simulation, considerin...
We study the chemical enrichment of elliptical galaxies using a semi-analytic model of galaxy for... more We study the chemical enrichment of elliptical galaxies using a semi-analytic model of galaxy formation combined with a cosmological N-body simula- tion of dark matter particles. In particular, we study the a-element abun- dances with respect to the iron content of galaxies. The main modification to the previous models (Cora 2006; Lagos et al. 2008; Tecce et al. 2010) was the implementation of a top heavy variable initial mass function with a theoretical basis (Weidner & Kroupa 2004, 2005, 2006; Weidner et al. 2011). We find that with a single initial mass function at all epochs the observed trend of [a/Fe] with the stellar mass of elliptical galaxies can be hardly reproduced. We propound that a top heavy integrated galactic mass function can be a plausible solution for this problem. FULL TEXT IN SPANISH
We use a model that combines N-body cosmological simulations of galaxy clusters and a semi-analyt... more We use a model that combines N-body cosmological simulations of galaxy clusters and a semi-analytic model of galaxy formation (SAG: Semi-analytical galaxies; Lagos, Cora & Padilla, 2008) in order to study the properties of galaxy progenitors, using the information provided by their stellar haloes, and surviving satellites at redshift z = 0. We model the formation of stellar haloes by
According to the current galaxy-formation paradigm, mergers and interactions play an important ro... more According to the current galaxy-formation paradigm, mergers and interactions play an important role in shaping present-day galaxies. The remnants of this merger activity can be used to constrain galaxy-formation models. In this work, we use a sample of 30 hydrodynamical simulations of Milky Way mass haloes, from the AURIGA project, to generate surface brightness maps and search for the brightest stream in each halo as a function of varying limiting magnitude. We find that none of the models shows signatures of stellar streams at $\mu _{r}^{\lim} \le 25$ mag arcsec−2. The stream detection increases significantly between 28 and 29 mag arcsec−2. Nevertheless, even at 31 mag arcsec−2, 13 per cent of our models show no detectable streams. We study the properties of the brightest streams progenitors (BSPs). We find that BSPs are accreted within a broad range of infall times, from 1.6 to 10 Gyr ago, with only 25 per cent accreted within the last 5 Gyrs; thus, most BSPs correspond to relati...
We explore a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in ... more We explore a sample of barred galaxies in the Auriga magneto-hydrodynamical cosmological zoom-in simulations that form boxy/peanut (b/p) bulges. The morphology of bars and b/p’s vary for different mono-abundance populations, according to their kinematic properties, which are in turn set by the galaxy’s assembly history. We find that the Auriga galaxies which best reproduce the chemo-kinematic properties of the Milky Way bulge have a negligible fraction of ex-situ stars in the b/p region (< 1%), with flattened, thick disc-like metal-poor stellar populations, and with their last major merger occurring at tlookback > 12 Gyrs. This imposes an upper limit on the stellar mass ratio of subsequent mergers, which we find is broadly consistent with the recently proposed Gaia Sausage/Enceladus merger. The average fraction of ex-situ stars in the central regions of Auriga galaxies that form b/p’s is 3% – significantly lower than in those which do not form bars or b/p’s. While these centra...
Monthly Notices of the Royal Astronomical Society, 2021
ABSTRACTWe present a model to track the orbital evolution of ‘unresolved subhaloes’ (USHs) in cos... more ABSTRACTWe present a model to track the orbital evolution of ‘unresolved subhaloes’ (USHs) in cosmological simulations. USHs are subhaloes that are no longer distinguished by halo finders as self-bound overdensities within their larger host system due to limited mass resolution. These subhaloes would host ‘orphan galaxies’ in semi-analytic models of galaxy formation and evolution (SAMs). Predicting the evolution of the phase-space components of USHs is crucial for the adequate modelling of environmental processes, interactions, and mergers implemented in SAMs that affect the baryonic properties of orphan satellites. Our model takes into account dynamical friction drag, mass-loss by tidal stripping and merger with the host halo, involving three free parameters. To calibrate this model, we consider two DM-only simulations of different mass resolution (MultiDark simulations). The simulation with higher mass resolution (smdpl; $m_{\rm DM} = 9.6 \times 10^7\, h^{-1}\, \mathrm{M_{\odot }}...
Wepresent an updatedmodel for the evolution of the orbits of "orphan galaxies" to be us... more Wepresent an updatedmodel for the evolution of the orbits of "orphan galaxies" to be used in the SAG semi-analytical model of galaxy formation and evolution. In cosmological simulations, orphan galaxies are those satellite galaxies for which, due to limited mass resolution, halo finders lose track of their dark matter subhalos and can no longer be distinguished as selfbound overdensities within the larger host system. Since the evolution of orphans depends strongly on the orbit they describe within their host halo, a proper treatment of their evolution is crucial in predicting the distribution of subhalos and satellite galaxies. The model proposed takes into account the dynamical friction drag, mass loss by tidal stripping and a proximity merger criterion, also it is simple enough to be inexpensive from a computational point of view. To calibrate this model, we apply it onto a dark matter only simulation and compare the results with a high resolution simulation, considerin...
We study the chemical enrichment of elliptical galaxies using a semi-analytic model of galaxy for... more We study the chemical enrichment of elliptical galaxies using a semi-analytic model of galaxy formation combined with a cosmological N-body simula- tion of dark matter particles. In particular, we study the a-element abun- dances with respect to the iron content of galaxies. The main modification to the previous models (Cora 2006; Lagos et al. 2008; Tecce et al. 2010) was the implementation of a top heavy variable initial mass function with a theoretical basis (Weidner & Kroupa 2004, 2005, 2006; Weidner et al. 2011). We find that with a single initial mass function at all epochs the observed trend of [a/Fe] with the stellar mass of elliptical galaxies can be hardly reproduced. We propound that a top heavy integrated galactic mass function can be a plausible solution for this problem. FULL TEXT IN SPANISH
We use a model that combines N-body cosmological simulations of galaxy clusters and a semi-analyt... more We use a model that combines N-body cosmological simulations of galaxy clusters and a semi-analytic model of galaxy formation (SAG: Semi-analytical galaxies; Lagos, Cora & Padilla, 2008) in order to study the properties of galaxy progenitors, using the information provided by their stellar haloes, and surviving satellites at redshift z = 0. We model the formation of stellar haloes by
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Papers by Ignacio Gargiulo