I am a CONICET researcher at the Instituto de Astronomía y Física del Espacio (IAFE) in Buenos Aires, Argentina. My research focuses on using numerical simulations and deep learning to study how galaxies form and evolve.
I had the honor of contributing to a Congressional Report on Artificial Intelligence (AI) by the Biblioteca del Congreso de la Nación (BCN). The report explores AI’s transformative impact on Argentina, focusing on its use in health, scientific research, education, and governance. It also addresses critical issues such as data privacy, algorithmic bias, and cybersecurity, emphasizing the need for legislative updates to ensure ethical AI deployment.
Primordial black holes (PBHs) have been proposed as potential candidates for dark matter (DM) and have garnered significant attention in recent years. Our objective is to delve into the distinct impact of PBHs on gas properties and their potential role in shaping the cosmic structure. Specifically, we aim to analyze the evolving gas properties while considering the presence of accreting PBHs with varying monochromatic masses and in different quantities. By studying the feedback effects produced by this accretion, our final goal is to assess the plausibility of PBHs as candidates for DM. We develop a semi-analytical model which works on top of the CIELO hydrodynamical simulation around \(z\sim23\). This model enables a comprehensive analysis of the evolution of gas properties influenced by PBHs. Our focus lies on the temperature and hydrogen abundances, placing specific emphasis on the region closest to the halo center. We explore PBH masses of 1, 33, and 100\(M_\odot\), located within mass windows where a substantial fraction of DM could exist in the form of PBHs. We investigate various DM fractions composed of these PBHs (\(f_{\rm{PBH}}>10^{-4}\)).Our findings suggest that the existence of PBHs with masses of \(1~M_\odot\) and fractions greater than or equal to approximately \(10^{-2}\) would be ruled out due to the significant changes induced in gas properties. The same applies to PBHs with a mass of \(33~M_\odot\) and \(100~M_\odot\) and fractions greater than approximately \(10^{-3}\). These effects are particularly pronounced in the region nearest to the halo center, potentially leading to delayed galaxy formation within haloes.
Jara-Ferreira, F. ; Tissera, P. B. search by orcid ; Sillero, E. ; Rosas-Guevara, Y. search by orcid ; Pedrosa, S. E. ; De Rossi, M. E. ; Theuns, T. search by orcid ; Bignone, L.
The variations in metallicity and spatial patterns within star-forming regions of galaxies result from diverse physical processes unfolding throughout their evolutionary history, with a particular emphasis in recent events. Analysing MaNGA and \eagle~galaxies, we discovered an additional dependence of the mass-metallicity relation (MZR) on metallicity gradients (\(\nabla_{\rm (O/H)}\)). Two regimes emerged for low and high stellar mass galaxies, distinctly separated at approximately \(m_\odot > 10^{9.75}\). Low-mass galaxies with strong positive \(\nabla_{\rm (O/H)}\)~appear less enriched than the MZR median, while those with strong negative gradients are consistently more enriched in both simulated and observed samples. Interestingly, low-mass galaxies with strong negative \(\nabla_{\rm (O/H)}\)~exhibit high star-forming activity, regardless of stellar surface density or \(\nabla_{\rm (O/H)}\). In contrast, a discrepancy arises for massive galaxies between MaNGA and \eagle~datasets. The latter exhibit a notable anticorrelation between specific star formation rate and stellar surface density, independent of \(\nabla_{\rm (O/H)}\), while MaNGA galaxies show this trend mainly for strong positive \(\nabla_{\rm (O/H)}\). Further investigation indicates that galaxies with strong negative gradients tend to host smaller central black holes in observed datasets, a trend not replicated in simulations. These findings suggest disparities in metallicity recycling and mixing history between observations and simulations, particularly in massive galaxies with varying metallicity gradients. These distinctions could contribute to a more comprehensive understanding of the underlying physics.
In this work, we aim at investigating the morphology evolution of Milky Way mass-like dark matter haloes selected from the CIELO and IllustrisTNG Projects. The connection between halo shapes and their environment has been studied in previous works at z=0 but their connection remains yet to be fully understood. We focus on the evolution across cosmic time of the halo shapes and the relation with the infalling material, using hydrodynamical simulations. Our findings show that haloes tend to be more triaxial at earlier times as a consequence of stronger accretion in the direction of the filaments. As the haloes evolve towards a dominant isotropic accretion mode and relaxation, their shape at 20 percent of the virial mass becomes more spherical. In agreement with previous results, baryons have an important effect within the inner regions of the haloes, driving them from triaxial to rounder shapes. We also find a correlation between the strength of the quadrupole infalling mode and the degree of ellipticity of the haloes: as the filament strength decreases steadily with redshift, the haloes became more spherical and less elliptical.
Context. The morphological classification of galaxies is considered a relevant issue and can be approached from different points of
view. The increasing growth in the size and accuracy of astronomical data sets brings with it the need for the use of automatic methods
to perform these classifications.
Aims. The aim of this work is to propose and evaluate a method for automatic unsupervised classification of kinematic morphologies
of galaxies that yields a meaningful clustering and captures the variations of the fundamental properties of galaxies.
Methods. We obtain kinematic maps for a sample of 2064 galaxies from the largest simulation of the eagle project that mimics
integral field spectroscopy (IFS) images. These maps are the input of a dimensionality reduction algorithm followed by a clustering
algorithm. We analyse the variation of physical and observational parameters among the clusters obtained from the application of this
procedure to different inputs. The inputs studied in this paper are (a) line-of-sight velocity maps for the whole sample of galaxies
observed at fixed inclinations, (b) line-of-sight velocity, dispersion, and flux maps together for the whole sample of galaxies observed
at fixed inclinations, (c) line-of-sight velocity, dispersion, and flux maps together for two separate subsamples of edge-on galaxies with
similar amount of rotation, and (d) line-of-sight velocity, dispersion, and flux maps together for galaxies from different observation
angles mixed.
Results. The application of the method to solely line-of-sight velocity maps achieves a clear division between slow rotators (SRs) and
fast rotators (FRs) and can differentiate rotation orientation. By adding the dispersion and flux information at the input, low rotation
edge-on galaxies are separated according to their shapes and, at lower inclinations, the clustering using the three types of maps
maintains the overall information obtained using only the line-of-sight velocity maps. This method still produces meaningful groups
when applied to SRs and FRs separately, but, in the first case, the division into clusters is less clear than when the input includes a
variety of morphologies. When applying the method to a mixture of galaxies observed from different inclinations, we obtain results
that are similar to those in our previous experiments with the advantage that in this case the input is more realistic. In addition, our
method has proven to be robust to consistently classify the same galaxies viewed from different inclinations
Isabel Santos-Santos, Matías Gámez-Marín, Rosa Domínguez-Tenreiro, Patricia B. Tissera, Lucas Bignone, Susana E. Pedrosa, Héctor Artal, M.Ángeles Gómez-Flechoso, Víctor Rufo-Pastor, Francisco Martínez-Serrano, Arturo Serna
We use two zoom-in Lambda-CDM hydrodynamical simulations of massive disk galaxies to study the possible existence of fixed satellite groups showing a kinematically-coherent behaviour across evolution (angular momentum conservation and clustering). We identify three such groups in the two simulations, defining kinematically-coherent, time-persistent planes (KPPs) that last at least from virialization to z=0 (more than 7 Gyrs). This proves that orbital pole clustering is not necessarily set in at low redshift, representing a long-lived property of galaxy systems. KPPs are thin and oblate, represent ∼25−40% of the total number of satellites in the system, and are roughly perpendicular to their corresponding central disk galaxies during certain periods, consistently with Milky Way z=0 data. KPP satellite members are statistically distinguishable from satellites outside KPPs: they show higher specific orbital angular momenta, orbit more perpendicularly to the central disk galaxy, and have larger pericentric distances, than the latter. We numerically prove, for the first time, that KPPs and the best-quality positional planes share the same space configuration across time, such that KPPs act as `skeletons’ preventing the latter of being washed out in short timescales. In one of the satellite-host systems, we witness the late capture of a massive dwarf galaxy endowed with its own satellite system, also organized into a KPP configuration prior to its capture. We briefly explore the consequences this event has on the host’s KPP, and on the possible enhancement of the asymmetry in the number of satellites rotating in one sense or the opposite within the KPP.
We study the impact of the environment on galaxies as they fall in and orbit in the potential well of a Local Group (LG) analogue, following them with high cadence. The analysis is performed on eight disc satellite galaxies from the CIELO suite of hydrodynamical simulations. All galaxies have stellar masses within the range \([10^{8.1} - 10^{9.56}] M_{\odot}\)h−1. We measure tidal torques, ram pressure and specific star formation rates (sSFR) as a function of time, and correlate them with the amount of gas lost by satellites along their orbits. Stronger removal episodes occur when the disc plane is oriented perpendicular to the direction of motion. More than one peripassage is required to significantly modify the orientations of the discs with respect to the orbital plane. The gas removed during the interaction with the central galaxies may be also found opposite to the direction of motion, depending on the orbital configuration. Satellites are not totally quenched when the galaxies reach their first peripassage, and continue forming about 10% of the final stellar mass after this event. The fraction of removed gas is found to be the product of the joint action of tidal torque and ram pressure, which can also trigger new star formation activity and subsequent supernova feedback.
We analyse the evolution of the oxygen abundance gradient of star-forming galaxies with stellar mass M∗≥10\(^9\) M\(_\odot\) in the EAGLE simulation over the redshift range z = [0, 2.5]. We find that the median metallicity gradient of the simulated galaxies is close to zero at all z, whereas the scatter around the median increases with z. The metallicity gradients of individual galaxies can evolve from strong to weak and vice versa, since mostly low-metallicity gas accretes on to the galaxy, resulting in enhanced star formation and ejection of metal-enriched gas by energy feedback. Such episodes of enhanced accretion, mainly dominated by major mergers, are more common at higher z and hence contribute to increasing the diversity of gradients. For galaxies with negative metallicity gradients, we find a redshift evolution of ∼−0.03 dex kpc\(^{−1}\)/δz . A positive mass dependence is found at z ≤ 0.5, which becomes slightly stronger for higher redshifts and, mainly, for M∗<10\(^{9.5}\) M\(_\odot\) . Only galaxies with negative metallicity gradients define a correlation with galaxy size, consistent with an inside-out formation scenario. Our findings suggest that major mergers and/or significant gas accretion can drive strong negative or positive metallicity gradients. The first ones are preferentially associated with disc-dominated galaxies, and the second ones with dispersion-dominated systems. The comparison with forthcoming observations at high redshift will allow a better understanding of the potential role of metallicity gradients as a chemical probe of galaxy formation.
Observations show that the surface brightness of disc galaxies can be well-described by a single exponential (TI), up-bending (TIII) or down-bending (TII) profiles in the outskirts. Here we characterize the mass surface densities of simulated late-type galaxies from the EAGLE project according to their distribution of mono-age stellar populations, the star formation activity and angular momentum content. We find that the inner scale-lengths of TII galaxies correlate with their stellar spin parameter λ, while those with TI and TIII profiles show a correlation only for λ>0.35. The outer scale-lengths of TII and TIII discs show a positive trend with λ, albeit weaker for the latter. TII discs prefer fast rotator galaxies. With regards to the stellar age distribution, negative and U-shape age profiles are the most common for all disc types. Positive age profiles are determined by a more significant contributions of young stars in the central regions, which decrease rapidly in the outer parts. TII discs prefer relative higher contributions of old stars compared to other mono-age populations across the discs whereas TIII discs become progressively more dominated by intermediate age (2-6 Gyrs) stars for increasing radius. The change in slope of the age profiles is located after the break of the mass surface density. We find evidence of larger flaring for the old stellar populations in TI and TIII systems compared to TII. Overall, the relative distributions of mono-age stellar populations and the dependence of star formation on radius is found to modulate the different disc types and age profiles.
Santos-Santos, Isabel ; Domínguez-Tenreiro, Rosa ; Artal, Héctor ; Pedrosa, Susana E. ; Bignone, Lucas ; Martínez-Serrano, Francisco ; Gómez-Flechoso, M. Ángeles ; Tissera, Patricia B. ; Serna, Arturo
We address the “plane of satellites problem” by studying planar configurations around two disk galaxies with no late major mergers, formed in zoom-in hydro-simulations. Due to the current lack of good-quality kinematic data for M31 satellites, we use only positional information. So far, positional analyses of simulations are unable to find planes as thin and populated as the observed ones. We follow a novel systematic and detailed plane searching technique to study the properties and quality of planes of satellites, in both simulations or real data. In particular, (I) we extend the four-galaxy-normal density plot method (Pawlowski et al. 2013) in a way designed to efficiently identify high-quality planes (I.e., thin and populated) without imposing extra constraints on their properties, and (II), we apply it for the first time to simulations. Using zoom-in simulations allows us to mimic Milky Way/M31-like systems regarding the number of satellites involved as well as galactic disk effects. In both simulations, we find satellite planar configurations that are compatible, along given time intervals, with all of the spatial characteristics of observed planes identified using the same methodology. During most of these periods, planes are approximately perpendicular to the galactic disk. However, the fraction of co-orbiting satellites within them is, in general, low, suggesting time-varying satellite membership. We conclude that high-quality positional planes of satellites could be not infrequent in ΛCDM-formed disk galaxies with a quiet assembly history. Detecting kinematically coherent, time-persistent planes demands considering the full six-dimensional phase-space information of satellites.
We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, M20, Concentration, and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of \(\log_{10}(M_{*}/{M}_\odot)\) > 10 galaxies at z ∼ 0.05 in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large-scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in ILLUSTRIS-TNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.
We identify a simulated Milky Way analog in the EAGLE suite of cosmological hydrodynamical simulations. This galaxy not only shares similar global properties as the Milky Way, but was specifically selected because its merger history resembles that currently known for the Milky Way. In particular we find that this Milky Way analog has experienced its last significant merger (with a stellar mass ratio ∼0.2) at z ∼ 1.2. We show that this merger affected both the dynamical properties of the stars present at the time, contributing to the formation of a thick disk, and also leading to a significant increase in the star formation rate of the host. This object is thus particularly suitable for understanding the early evolutionary history of the Milky Way. It is also an ideal candidate for re-simulation with much higher resolution, as this would allow addressing a plethora of interesting questions such as, for example, the specific distribution of dark matter near the Sun.
Context. Understanding the formation and evolution of early-type, spheroid-dominated galaxies is an open question within the context of the hierarchical clustering scenario, particularly in low-density environments.
Aims: Our goal is to study the main structural, dynamical, and stellar population properties and assembly histories of field spheroid-dominated galaxies formed in a Λ-cold dark matter (Λ-CDM) scenario to assess to what extent they are consistent with observations.
Methods: We selected spheroid-dominated systems from a Λ-CDM simulation that includes star formation (SF), chemical evolution, and supernova feedback. The sample is made up of 18 field systems with MStar ≲ 6 × 10\(^{10}\) M\(_\odot\) that are dominated by the spheroid component. For this sample we estimated the fundamental relations of ellipticals and compared them with current observations.
Results: The simulated spheroid galaxies have sizes that are in good agreement with observations. The bulges follow a Sersic law with Sersic indexes that correlate with the bulge-to-total mass ratios. The structural-dynamical properties of the simulated galaxies are consistent with observed Faber-Jackson, fundamental plane, and Tully-Fisher relations. However, the simulated galaxies are bluer and with higher star formation rates (SFRs) than the observed isolated early-type galaxies. The archaeological mass growth histories show a slightly delayed formation and more prominent inside-out growth mode than observational inferences based on the fossil record method.
Conclusions: The main structural and dynamical properties of the simulated spheroid-dominated galaxies are consistent with observations. This is remarkable since our simulation has not been calibrated to match them. However, the simulated galaxies are blue and star-forming, and with later stellar mass growth histories compared to observational inferences. This is mainly due to the persistence of extended discs in the simulations. The need for more efficient quenching mechanisms able to avoid further disc growth and SF is required in order to reproduce current observational trends.
We study the properties of long gamma-ray bursts (LGRBs) using a large-scale hydrodynamical cosmological simulation, the Illustris simulation. We determine the LGRB host populations under different thresholds for the LGRB progenitor metallicities, according to the collapsar model. We compare the simulated sample of LGRBs hosts with recent, largely unbiased, host samples: BAT6 and SHOALS. We find that at z < 1 simulated hosts follow the mass-metallicity relation and the fundamental metallicity relation simultaneously, but with a paucity of high-metallicity hosts, in accordance with observations. We also find a clear increment in the mean stellar mass of LGRB hosts and their star formation rate (SFR) with redshift up to z < 3 on account of the metallicity dependence of progenitors. We explore the possible origin of LGRBs in metal rich galaxies, and find that the intrinsic metallicity dispersion in galaxies could explain their presence. LGRB hosts present a tighter correlation between galaxy metallicity and internal metallicity dispersion compared to normal star-forming galaxies. We find that the Illustris simulations favours the existence of a metallicity threshold for LGRB progenitors in the range 0.3-0.6 Z\(_\odot\).
We study non-parametric morphologies of mergers events in a cosmological context, using the Illustris project. We produce mock g-band images comparable to observational surveys from the publicly available Illustris simulation idealized mock images at \(z=0\). We then measure non parametric indicators: asymmetry, Gini, M\(_{20}\), clumpiness and concentration for a set of galaxies with M\(_*\)>\(10^{10}\) M\(_\odot\). We correlate these automatic statistics with the recent merger history of galaxies and with the presence of close companions. Our main contribution is to assess in a cosmological framework, the empirically derived non-parametric demarcation line and average time-scales used to determine the merger rate observationally. We found that 98 per cent of galaxies above the demarcation line have a close companion or have experienced a recent merger event. On average, merger signatures obtained from the G−M\(_{20}\) criteria anticorrelate clearly with the elapsing time to the last merger event. We also find that the asymmetry correlates with galaxy pair separation and relative velocity, exhibiting the larger enhancements for those systems with pair separations d<50 h\(^{−1}\) kpc and relative velocities V<350 km s\(^{−1}\). We find that the G−M\(_{20}\) is most sensitive to recent mergers (∼0.14 Gyr) and to ongoing mergers with stellar mass ratios greater than 0.1. For this indicator, we compute a merger average observability time-scale of ∼0.2 Gyr, in agreement with previous results and demonstrate that the morphologically derived merger rate recovers the intrinsic total merger rate of the simulation and the merger rate as a function of stellar mass.
This year, I had the privilege of participating as a mentor in the NASA Space Apps Challenge, with the local event organized by CONAE, IBM, and CAECE. It was an inspiring experience to guide and support teams in Buenos Aires as they tackled real-world challenges. Over the course of 48 hours, participants worked on innovative solutions related to space exploration and Earth sciences. It was incredible to witness the creativity, collaboration, and passion of all participants.
We have a lot of exciting material to prepare and are looking forward to the challenge. Stay tuned for more updates as we get ready to explore the intersection of machine learning and astrophysics!
I gave a talk at the 63th meeting of the Argentinian Astronomical Society on the unsupervised optical morphologies of galaxies in the Eagle simulation (spanish only).
We received at Andrés Bello University visiting students from the Physical-Mathematical Study Association (“FMF”) based in Groningen, The Netherlands. Every other year they organize a large excursion abroad (“GBE”) for their members to a destination outside of Europe.
As part of their excursion, we gave them a tour of the campus, and a glimpse into our research.
I was invited to Lidia Matte school, near Santiago de Chile to speak about galaxies with students. This was part of a terrific program from CONICYT to link students and scientists.
Students at the astronomical observatory of the Colegio Nacional de Buenos Aires observed the partial solar eclipse and made pictures and mesurements. Congratulations to their teacher, Araceli Barrera for organizing this activity. It was very fun to participate.
This year, I had the privilege of participating as a mentor in the NASA Space Apps Challenge, with the local event organized by CONAE, IBM, and CAECE. It was an inspiring experience to guide and support teams in Buenos Aires as they tackled real-world challenges. Over the course of 48 hours, participants worked on innovative solutions related to space exploration and Earth sciences. It was incredible to witness the creativity, collaboration, and passion of all participants.
We received at Andrés Bello University visiting students from the Physical-Mathematical Study Association (“FMF”) based in Groningen, The Netherlands. Every other year they organize a large excursion abroad (“GBE”) for their members to a destination outside of Europe.
As part of their excursion, we gave them a tour of the campus, and a glimpse into our research.
I was invited to Lidia Matte school, near Santiago de Chile to speak about galaxies with students. This was part of a terrific program from CONICYT to link students and scientists.
Students at the astronomical observatory of the Colegio Nacional de Buenos Aires observed the partial solar eclipse and made pictures and mesurements. Congratulations to their teacher, Araceli Barrera for organizing this activity. It was very fun to participate.
I gave a talk at the 63th meeting of the Argentinian Astronomical Society on the unsupervised optical morphologies of galaxies in the Eagle simulation (spanish only).
I gave a talk at the 63th meeting of the Argentinian Astronomical Society on the unsupervised optical morphologies of galaxies in the Eagle simulation (spanish only).
We study the optical morphology of galaxies in a large-scale hydrodynamic cosmological simulation, the EAGLE simulation. Galaxy morphologies were characterized using non-parametric statistics (Gini, M20, Concentration, and Asymmetry) derived from mock images computed using a 3D radiative transfer technique and post-processed to approximate observational surveys. The resulting morphologies were contrasted to observational results from a sample of \(\log_{10}(M_{*}/{M}_\odot)\) > 10 galaxies at z ∼ 0.05 in the GAMA survey. We find that the morphologies of EAGLE galaxies reproduce observations, except for asymmetry values which are larger in the simulated galaxies. Additionally, we study the effect of spatial resolution in the computation of non-parametric morphologies, finding that Gini and Asymmetry values are systematically reduced with decreasing spatial resolution. Gini values for lower mass galaxies are especially affected. Comparing against other large-scale simulations, the non-parametric statistics of EAGLE galaxies largely agree with those found in ILLUSTRIS-TNG. Additionally, EAGLE galaxies mostly reproduce observed trends between morphology and star formation rate and galaxy size. Finally, We also find a significant correlation between optical and kinematic estimators of morphologies, although galaxy classification based on an optical or a kinematic criteria results in different galaxy subsets. The correlation between optical and kinematic morphologies is stronger in central galaxies than in satellites, indicating differences in morphological evolution.
We study non-parametric morphologies of mergers events in a cosmological context, using the Illustris project. We produce mock g-band images comparable to observational surveys from the publicly available Illustris simulation idealized mock images at \(z=0\). We then measure non parametric indicators: asymmetry, Gini, M\(_{20}\), clumpiness and concentration for a set of galaxies with M\(_*\)>\(10^{10}\) M\(_\odot\). We correlate these automatic statistics with the recent merger history of galaxies and with the presence of close companions. Our main contribution is to assess in a cosmological framework, the empirically derived non-parametric demarcation line and average time-scales used to determine the merger rate observationally. We found that 98 per cent of galaxies above the demarcation line have a close companion or have experienced a recent merger event. On average, merger signatures obtained from the G−M\(_{20}\) criteria anticorrelate clearly with the elapsing time to the last merger event. We also find that the asymmetry correlates with galaxy pair separation and relative velocity, exhibiting the larger enhancements for those systems with pair separations d<50 h\(^{−1}\) kpc and relative velocities V<350 km s\(^{−1}\). We find that the G−M\(_{20}\) is most sensitive to recent mergers (∼0.14 Gyr) and to ongoing mergers with stellar mass ratios greater than 0.1. For this indicator, we compute a merger average observability time-scale of ∼0.2 Gyr, in agreement with previous results and demonstrate that the morphologically derived merger rate recovers the intrinsic total merger rate of the simulation and the merger rate as a function of stellar mass.
Isabel Santos-Santos, Matías Gámez-Marín, Rosa Domínguez-Tenreiro, Patricia B. Tissera, Lucas Bignone, Susana E. Pedrosa, Héctor Artal, M.Ángeles Gómez-Flechoso, Víctor Rufo-Pastor, Francisco Martínez-Serrano, Arturo Serna
We use two zoom-in Lambda-CDM hydrodynamical simulations of massive disk galaxies to study the possible existence of fixed satellite groups showing a kinematically-coherent behaviour across evolution (angular momentum conservation and clustering). We identify three such groups in the two simulations, defining kinematically-coherent, time-persistent planes (KPPs) that last at least from virialization to z=0 (more than 7 Gyrs). This proves that orbital pole clustering is not necessarily set in at low redshift, representing a long-lived property of galaxy systems. KPPs are thin and oblate, represent ∼25−40% of the total number of satellites in the system, and are roughly perpendicular to their corresponding central disk galaxies during certain periods, consistently with Milky Way z=0 data. KPP satellite members are statistically distinguishable from satellites outside KPPs: they show higher specific orbital angular momenta, orbit more perpendicularly to the central disk galaxy, and have larger pericentric distances, than the latter. We numerically prove, for the first time, that KPPs and the best-quality positional planes share the same space configuration across time, such that KPPs act as `skeletons’ preventing the latter of being washed out in short timescales. In one of the satellite-host systems, we witness the late capture of a massive dwarf galaxy endowed with its own satellite system, also organized into a KPP configuration prior to its capture. We briefly explore the consequences this event has on the host’s KPP, and on the possible enhancement of the asymmetry in the number of satellites rotating in one sense or the opposite within the KPP.
Santos-Santos, Isabel ; Domínguez-Tenreiro, Rosa ; Artal, Héctor ; Pedrosa, Susana E. ; Bignone, Lucas ; Martínez-Serrano, Francisco ; Gómez-Flechoso, M. Ángeles ; Tissera, Patricia B. ; Serna, Arturo
We address the “plane of satellites problem” by studying planar configurations around two disk galaxies with no late major mergers, formed in zoom-in hydro-simulations. Due to the current lack of good-quality kinematic data for M31 satellites, we use only positional information. So far, positional analyses of simulations are unable to find planes as thin and populated as the observed ones. We follow a novel systematic and detailed plane searching technique to study the properties and quality of planes of satellites, in both simulations or real data. In particular, (I) we extend the four-galaxy-normal density plot method (Pawlowski et al. 2013) in a way designed to efficiently identify high-quality planes (I.e., thin and populated) without imposing extra constraints on their properties, and (II), we apply it for the first time to simulations. Using zoom-in simulations allows us to mimic Milky Way/M31-like systems regarding the number of satellites involved as well as galactic disk effects. In both simulations, we find satellite planar configurations that are compatible, along given time intervals, with all of the spatial characteristics of observed planes identified using the same methodology. During most of these periods, planes are approximately perpendicular to the galactic disk. However, the fraction of co-orbiting satellites within them is, in general, low, suggesting time-varying satellite membership. We conclude that high-quality positional planes of satellites could be not infrequent in ΛCDM-formed disk galaxies with a quiet assembly history. Detecting kinematically coherent, time-persistent planes demands considering the full six-dimensional phase-space information of satellites.
I had the honor of contributing to a Congressional Report on Artificial Intelligence (AI) by the Biblioteca del Congreso de la Nación (BCN). The report explores AI’s transformative impact on Argentina, focusing on its use in health, scientific research, education, and governance. It also addresses critical issues such as data privacy, algorithmic bias, and cybersecurity, emphasizing the need for legislative updates to ensure ethical AI deployment.
We have a lot of exciting material to prepare and are looking forward to the challenge. Stay tuned for more updates as we get ready to explore the intersection of machine learning and astrophysics!
I had the honor of contributing to a Congressional Report on Artificial Intelligence (AI) by the Biblioteca del Congreso de la Nación (BCN). The report explores AI’s transformative impact on Argentina, focusing on its use in health, scientific research, education, and governance. It also addresses critical issues such as data privacy, algorithmic bias, and cybersecurity, emphasizing the need for legislative updates to ensure ethical AI deployment.
We have a lot of exciting material to prepare and are looking forward to the challenge. Stay tuned for more updates as we get ready to explore the intersection of machine learning and astrophysics!
I am honored to have received the Encouragement Award from the National Academy of Exact, Physical, and Natural Sciences (ANCEFN). This award recognizes the contributions of young professionals in Argentina, up to 40 years of age, in scientific and technological research. It’s a privilege to be acknowledged for my work, and I look forward to continuing my efforts in advancing our understanding of astronomy and science!
We study the properties of long gamma-ray bursts (LGRBs) using a large-scale hydrodynamical cosmological simulation, the Illustris simulation. We determine the LGRB host populations under different thresholds for the LGRB progenitor metallicities, according to the collapsar model. We compare the simulated sample of LGRBs hosts with recent, largely unbiased, host samples: BAT6 and SHOALS. We find that at z < 1 simulated hosts follow the mass-metallicity relation and the fundamental metallicity relation simultaneously, but with a paucity of high-metallicity hosts, in accordance with observations. We also find a clear increment in the mean stellar mass of LGRB hosts and their star formation rate (SFR) with redshift up to z < 3 on account of the metallicity dependence of progenitors. We explore the possible origin of LGRBs in metal rich galaxies, and find that the intrinsic metallicity dispersion in galaxies could explain their presence. LGRB hosts present a tighter correlation between galaxy metallicity and internal metallicity dispersion compared to normal star-forming galaxies. We find that the Illustris simulations favours the existence of a metallicity threshold for LGRB progenitors in the range 0.3-0.6 Z\(_\odot\).
We identify a simulated Milky Way analog in the EAGLE suite of cosmological hydrodynamical simulations. This galaxy not only shares similar global properties as the Milky Way, but was specifically selected because its merger history resembles that currently known for the Milky Way. In particular we find that this Milky Way analog has experienced its last significant merger (with a stellar mass ratio ∼0.2) at z ∼ 1.2. We show that this merger affected both the dynamical properties of the stars present at the time, contributing to the formation of a thick disk, and also leading to a significant increase in the star formation rate of the host. This object is thus particularly suitable for understanding the early evolutionary history of the Milky Way. It is also an ideal candidate for re-simulation with much higher resolution, as this would allow addressing a plethora of interesting questions such as, for example, the specific distribution of dark matter near the Sun.
