25th edition of the Guillermo Haro Workshop

In this presentation I describe the original TOROS project and its goal of performing optical follow-ups of gravitational waves. TOROS stands for transient Optical Robotic Observatory of the South and its original goal was to install a wide field of view telescope in Cordon Macon, in the Argentine portion of the Atacama high plateau. I discuss some of its technical difficulties and the decision to install it at a different location on the Andes hills of southwestern Argentina. I discuss also the results of its recent commissioning and the plans for the future.

The initial configuration of magnetized accretion disks around rotating black holes plays a crucial role in determining the nonlinear evolution of the plasma. It triggers the development of magnetorotational instability (MRI), angular momentum transport, mass accretion, and magnetic flux accumulation near the event horizon—ultimately influencing the conditions for jet launching via the Blandford–Znajek mechanism. In this talk, I will explore how different initial disk and magnetic field configurations can lead to different outcomes: from powerful, collimated relativistic jets to weak or even absent outflows. I will also present results from 3D general relativistic magnetohydrodynamical (GRMHD) simulations combined with general relativistic radiative transfer (GRRT) calculations to study the radiative signatures of self-consistently launched jets. These results will be compared with recent multi-frequency VLBI observations from the Event Horizon Telescope (EHT) collaboration, including black hole shadow imaging and jet emission. Finally, I will briefly discuss future observational prospects and challenges in linking simulations to data.

By means of simultaneously solving the Einstein - Klein Gordon - Maxwell system of equations, with appropriate boundary conditions, we constructed compact objects such that they posses magnetic field but the total chargevis zero. I'll present some properties of such objects and discuss on the way to generate bonna fide electromagnetic and gravitational emmissions without any extra assumptions.

Galaxy formation simulations have advanced dramatically, yet code-to-code discrepancies remain stubbornly persistent—anyone running comparative tests knows this (e.g. feedback implementation may play a significant role). AGORA cuts through the noise with what our community desperately needed: apples-to-apples code comparisons: same initial conditions, shared physics and, to some degree, reproducibility. By specifying a cosmology, baryonic physics and feedback across mesh (e.g. ART, Enzo, RAMSES), SPH (Gadget, ChaNGa, GEAR) and hybrid codes like GIZMO and AREPO, we have mapped convergence regions (dark matter profiles) and divergence hotspots (disk and outflow properties) among others. We try to address why codes, in some cases, diverge. AGORA provides shared diagnostics, public datasets and a framework to compare the subgrid physics models of the different codes. Upcoming work will test all the codes to study the formation of dwarf galaxies and blobs formed at high redshift.

The long range character of gravity when compared to the other three fundamental forces implies that calculating the evolution of astronomical systems, from extra-solar planetary systems out to galactic scales and cosmology, crucially hinges upon a firm understanding of gravity at all scales. While GR, with Newtonian gravity as a low velocity limit, has been successfully tested directly under a very wide range of conditions, a number of anomalies appearing always in a low acceleration regime have been known for decades. This acceleration range lies many orders of magnitude beyond the reach of direct tests, and hence represents a region of parameter space where we do not know for a fact exactly how gravity works. The standard interpretation has been to add the ad hoc hypothesis of Dark Matter at galactic scales, and Dark Energy at cosmological ones. I shall review a couple of recent research areas where this low acceleration regime is being probed directly, finding consistent results indicating gravitational anomalies signaling the breakdown of GR in the low acceleration regime, in ways which can not be fixed through the standard addition of an undetected mass component. Relative velocities of wide binary stars have over the past couple of years revealed inconsistencies with GR on the same acceleration scales where Dark Matter is required at galactic scales, at locations where the vertical dynamics of stars in the Milky Way disk limit the presence of any Dark Matter component to many orders of magnitude below what would be required to understand the anomaly detected. Finally, the presence of systematically asymmetric tidal tails beyond statistical variance around star clusters in the Milky Way, show gravity in this same low acceleration regime is inconsistent with GR, as in the relevant low velocity regime, Newtonian gravity forces the expectation of symmetric tidal tails. Perhaps it is time to evolve beyond parameter fitting with undetectable entities and seriously consider the need to develop modified theories of gravity which are predictive and not simply descriptive.

In this talk, I will present how axion-like particles (ALPs), with varying properties, can act as a dark matter medium in two distinct astrophysical settings: dwarf galaxies and pulsars. The first part of the study examines the self-gravitating dynamics of ALPs in the fuzzy dark matter regime and their influence on the rotation curves of dwarf galaxies. This analysis is based on high-resolution observations from the LITTLE THINGS catalogue. The second part explores the potential of pulsar polarimetry as an approach to test the electromagnetic couplings of ALPs. In this case, we make use of precision data from the Parkes Pulsar Timing Array and the European Pulsar Timing Array. Finally, I will discuss the constraints we have derived on ALPs in the low-mass regime, focusing on their couplings and mass. These findings help identify plausible parameter spaces where ALPs could account for the observed behavior of the dark matter medium in these environments.

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What are the main drivers in the evolution of galaxies? is one of the biggest open questions in Astronomy to date even though it is critical in every aspect of the evolving universe. This is because galaxy evolution is driven by a complex interplay of various processes and factors that affect the baryon cycle and shape the properties of galaxies over cosmic time. The interplay between several properties at multiple wavelengths, metals, cold gas, dust, environment, star formation rate in galaxies, and even magnetic fields, is mandatory to have a comprehensive understanding on how galaxies evolve. Metal-THINGS is obtaining IFU spectroscopy of a unique sample of 34 nearby galaxies from The HI Nearby Galaxy Survey (THINGS, Walter et al. 2008). One of the main characteristics of the THINGS galaxies is that they have been observed by multiple wavelengths. Metal-THINGS has already observed more than 130 nights with VIRUS-P (GCMS), and has fully mapped 25 galaxies from the THINGS survey. I will present the latest results of the Metal-THINGS survey focussing in the analysis of gas metallicity gradients (Vale et al. 2025, submitted), the reconstruction of the resolved Spectral Energy Distribution (SED) from UV to FIR (Garduño et al. 2023), effects of Ultra Luminous X-ray sources in galaxies (Lara-López et al. 2021), and the star formation rate in the rims of HI holes (Lara-López et al. 2023).

For about two dacades we have attempted to define homogeneous photometric scales for the metallicity and distance of globular clusters (GC), that are consistent with the sound spectroscopic approaches and the more recent parallax and proper motion results. To this end we emplyed the cluster member variable stars as indicators, mostly thr RR Lyrae variables but also the scondary indicators sucha as the SX Phoenicis variables (among th eblue stragglers) and the semi regular red giants (RG). In this talk I will summarize the strategies employed and the obtained results. I plan to briefly discuss the well known Oosterhoff dichotomy on evolutionary grounds, and the Oostheroff gap and its connection with possible extragalactic origin of some GCs.

Metallicities of galaxies at all redshifts are critical for deciphering a plethora of physical and evolutionary processes taking place among and inside galaxies, including star formation, stellar feedback and interstellar/intergalactic chemical enrichment. Studies of local star-forming galaxies (SFGs) can be performed at exquisite signal-to-noise and spatial resolution, which are not achievable at higher redshift. Therefore, these studies establish a baseline in understanding how gas and stellar properties evolve through cosmic time. I take advantage of the unique FUV spectroscopic capabilities of the Hubble Space Telescope, along with the high sensitivity in the MIR of the James Webb Space Telescope (JWST), and complement our space observations with those from several ground-based telescopes to investigate a sample of local galaxies, which span a wide range in morphological types, metallicities and star formation rates. The results from our metallicity studies of nearby (<100 Mpc) galaxies will be discussed with a dedicated focus on their stellar, neutral-gas, and ionized-gas components. I will show how using spectroscopic observations of star clusters and their nearby gas allows us to observe the chemical evolution of galaxies through a much larger window in both space and time. Lastly, I will present some of the most recent results from our JWST program where we carefully dissect the properties of the multiphase ISM on spatial scales of ~5 pc. I will close with a brief discussion on the implications these data have in the understanding of the processes that drive the evolution of galaxies.

Despite the efforts made in recent decades to obtain more realistic stellar models, considerable uncertainties still remain due to our incomplete knowledge of some complex physical processes that occur within stars, such as mixing, mass loss, rotation, to name a few of them. Modeling these processes still relies on empirical calibrations and this has a significant impact on theoretical predictions such as masses, ages and abundance yields of stars and stellar populations, which we commonly use to answer fundamental questions in astrophysics. Mixing in the central regions is one of the most important processes because stars will never forget its effects in subsequent evolution. It can be the result of convective motions and microscopic diffusion but also of differential rotation. I will also discuss the effects of mixing at the base of the convective envelope and show its possible large impact on the evolution of more massive stars. Finally, I will review the most recent mass loss models and show how this quite debated phenomenon can strongly influence the yields and ultimate fate of intermediate-mass and massive stars.

Planetary nebulae (PNe) are gaseous envelopes ejected by low-intermediate mass stars (LIMS) at advanced stages of evolution, post-Asymptotic Giant Branch. The present ages of these stars are from one to several Gyrs. The study of these nebulae and their central stars is useful to analyze the physical processes in the warm photoionized gas and to test theories of stellar evolution of LIMS. In addition, PNe are good tracers of their parent population and have been used to measure the distances, kinematics and masses of the host galaxies and to analyze their chemical evolution. In this work I will present some results on PN abundance determinations in nearby galaxies showing how they can help to test stellar evolution models, to determine the initial mass of the stellar progenitors and to analyze the chemical evolution of galaxies. Also, the chemical gradients in some spiral galaxies, as obtained from PNe, are presented.

I will review the role of interacting massive binary stars on the spectrophotometric properties of stellar populations as a function of age and metallicity predicted by synthesis models. The most relevant differences with respect to single star models occur in the ultraviolet, including the number of H and He ionizing photons and supernova rates. This spectral range is now observable with JWST in distant galaxies and the use of appropriate models is fundamental for the correct interpretation of these observations.

I will discuss the High-Latitude Time Domain Survey with Roman and its power in discovering and characterizing transient sources, in particular type Ia supernovae and their importance in characterizing the dark energy of the Universe. I will present the work of my team in implementing a pixel-to-cosmology framework and describe the strategies users may adopt to interact with this dataset and software.

We present a new iterative deblending method to separate the host galaxy (HG) and their Active Galactic Nuclei (AGNs) emission with the use of Integral Field spectroscopic (IFS) data. The method decomposes the resolved HG emission from the unresolved AGN emission by modelling the two-dimensional surface brightness (SB) profile of the point-spread function (PSF) and the two-dimensional SB HG continuum simultaneously per each monochromatic slide. Our method does not require any prior information about the observed SB profile or a detailed fitting of the PSF, making it ideal for the automatic analysis of large galaxy samples. In this work, we test the quality of our method, its advantages, and its disadvantages. We test our method by using a set of IFS mock data cubes to quantify the reliability of our deblending process and further compare our method with the QDBLEND3D analysis tool. Furthermore, we applied our method to three data cubes selected from the MaNGA survey according to the dominance of either its HG or its AGN. We show that our deblending method is capable of disengaging the bright, non-resolved AGN emission from the HG continuum and its narrow emission lines. However, the decoupling depends on how well the IFS spatially resolves the PSF, and on the relative flux intensity of the HG-AGN. Therefore, the method is ideal for disentangling the bright-flux contribution from AGN-dominated spectra.

I'll talk about one of the SDSS-V surveys: Local Volume Mapper. I'll describe the data path, from the raw data to the final products.

Radio continuum imaging has been a key approach to trace the production of stars and the activity of supermassive black holes at redshifts 0<z<5 – a cosmic epoch marked by the dominant fraction of star formation that is obscured by dust. In recent years, our team has pushed the resolution and sensitivity limits of the Very Large Array (VLA) to obtain some of the deepest and sharpest radio continuum images ever obtained, providing unique constraints on the radio emission of galaxies at high redshifts. In this talk, I will present multi-frequency VLA radio surveys in the GOODS-N, CEERS and Abell2744 fields that reach sub-μJy sensitivity and sub-arcsecond resolution at 3-10 GHz. After summarizing the available data products, I will provide an overview of the different science topics that are being addressed with these data sets; such as the estimation of the cosmic star formation rate density of the universe from free-free radio emission, the most distant radio sources ever detected, and constraints on the radio emission of the so-called “little red dots” recently discovered in deep JWST images. Finally, I will highlight the imaging challenges faced to produce and characterize the aforementioned radio surveys, which will be key to obtain future SKA and ngVLA blind radio surveys.

Recent studies have reported a non evolution of galaxy ages at redshifts higher than z ∼ 2.5, as well as galaxies older than the Universe. In this work, a sample of galaxies from JWST and HST was analyzed via photometry to further understand this astronomical phenomenon. No prior cosmological parameters were assumed in the analysis, but the spectroscopic redshift. When compared to stellar population synthesis models, the results for mass-weighted galaxy ages indicate that the analyzed objects seem to be divided into two subsets. The results for the subset with the majority of objects (60% assuming a flat-ΛCDM cosmology) indicate an evolution of galaxy ages within the redshift range z=0.1-7.0, in the sense that higher redshift galaxies are younger than the Universe. Sources of systematic errors were discussed drawing into conclusion that degeneracies between reddening-age-metallicity, and/or AGN emission may explain the rest 40% of the galaxies with ages older than expected from a flat-ΛCDM cosmology.

The star formation and mass assembly history of the most massive gravitationally bound structures in the Universe - galaxy clusters - remain poorly constrained observationally, particularly due to the scarce number of galaxy proto-clusters at high redshifts (the progenitor structures of local clusters). At low redshifts, the identification of galaxy clusters is relatively straightforward given that virialized clusters show nearly always a large fraction of massive (M_star > 10^11 M_sun ) elliptical galaxies with suppressed star formation rates, and large reservoirs of hot gas in their intracluster medium that can be traced by diffuse X-ray Bremsstrahlung or by the Sunyaev-Zeldovich effect. Nevertheless, at higher redshifts, when these systems have not yet collapsed, their identification and characterization have proven challenging. Galaxy members of massive clusters are believed to have formed a large fraction of their stellar masses through short episodes of intense star formation at z>2, consistent with the redshifts and star formation histories of Dusty Star-Forming Galaxies (DSFGs). As a consequence, the high-redshift progenitors of local massive galaxy clusters might be identified as overdensities of these DSFGs. In this talk I will present different efforts made by our group members and collaborators, both observationally and through simulations, to search for and more efficiently identify high redshift progenitors of present-day massive galaxy clusters in near-future wide-area (sub-)mm wavelength surveys, particularly with the TolTEC camera on the 50m LMT.

We present a steady-state analytical model for pressure-regulated formation of molecular clouds (MC) and stars (SF) in gaseous galactic disks and apply it to the Milky Way (MW). MC formation depends on midplane pressure PISM and metallicity Z, and for galactocentric distances R ≥ 5 kpc, PISM(R) scales approximately linearly with molecular gas surface density Σmol(R). The molecularization of the cold neutral medium (CNM) is, as originally proposed by Franco & Cox, due to the opacity of small dust grains that protect the center of the cloud from dissociating radiation when the column density is Σd ≥ 5 (Z/Z) M☉pc-2. The H2 formation rate per hydrogen atom is F~10-15 (PISM/P☉)T100 1/2s-1, and the corresponding formation rate per unit area is Σmol+ ~ 5 x 10-2 (PISM/P☉)T100 1/2M☉ kpc-2 yr-1, where P☉ is the pressure at the solar circle and T100 = T/100 K is the temperature of the cloud. In equilibrium, this equals the molecular gas destruction rate Σmol- due to SF. Self-gravity sets in when the column density of a cloud reaches Σsg = Σsg, (PISM/P☉) 1/2, with Σsg, 30 M☉ pc-2. Given the distribution of PISM (R) and Z(R) in the MW, the SF process at 5≤ R≤ 11 kpc follows a two-step track: first, MCs form from CNM gas and then they form stars when self-gravity sets in. The resulting SFR surface density is ΣSFR(R) ≈ (1.6-4) ×10-3 (PISM/P☉) M☉ kpc-2yr-1 with an average SF efficiency of εsf~(3-8) × 10-2.

In this talk I will discuss the pros and cons of the collapse and the turbulent model of molecular cloud dynamics and star formation, and what exactly the molecular clouds’ energy budget tells us; whether gravitational forces dominate over other sources of momentum, and what are the implications of the energy budget on the efficiency and rate of star formation. I will also show that the low values and the constancy of the “efficiency per free-fall time” arise naturally when clouds collapse. Our results imply that stellar feedback is the crucial ingredient to halt star formation, keeping the gas depletion time low on galactic levels. I will also show that the kinematic properties of young stars observed with Gaia are consistent with them being born from collapsing clouds rather than clouds supported by turbulence.

Using 2D simulations, we investigate how a non-accreting satellite on a fixed retrograde circular orbit affects the structure of the accretion disc in which it is embedded. We vary the satellite-to-primary mass ratio q, the disc viscosity ν, and the inner boundary conditions. A viscous criterion for gap opening is derived, which is broadly consistent with the simulations. We find a scaling relation of the gap depth with q and ν. Unlike the prograde case, the satellite is located at the gap's inner edge, resulting in a surface density at the satellite's orbital radius up to 20 times higher than at the gap's minimum. As the viscosity decreases, the gap depth increases, while the radial shift of the gap and the satellite's orbital radius decreases. Gap-opening satellites may drive radial motions in the disc, producing eccentric gaps. Positioned at the gap edge, satellites experience a rapidly fluctuating environment. Migrating satellites can develop orbital eccentricities comparable to the disc's aspect ratio. In a 3D simulation with q=0.01, the flow velocity exhibits a notorious vertical component in the gap's inner edge. A comparison between 2D and 3D simulations reveals a slight radial offset in gap position, resulting in a lower surface density at the perturber's orbital radius in the 3D simulation.

The Lockman Hole is an optimal region in the sky with the lowest Galactic line-of-sight column density (N_H=5.7x10^19 cm^-2). The Lockman-SpReSO project is a OSIRIS/GTC spectroscopic observational campaign of 1,144 objects (956 have Herschel far-infrared emission) observed within the central 24 x 24 arcmin^2 of the LH field. In this work, we present a detailed X-ray spectral analysis of the XMM-Newton counterparts from the Lockman-SpReSO project. We analyzed a total of 110 X-ray sources with a flux limit of 5 x 10^-16 erg s^-1 cm^-2 in the 0.3-10 keV band, selected through statistical cross-correlation (Likelihood ratio). 85% (93) of the sources were classified as AGNs based on their X-ray spectral properties, distributed over a large redshift range of z = 0.7-5. We used a set of absorbed power-law models to obtain absorbing column densities (N_H), rest-frame 2-10 keV luminosities (Lx), and iron line equivalent widths (EW_Fe). To account for upper-limits in our analysis, we employed a survival statistical method. We found that the fraction of obscured AGNs (N_H > 10^22, cm^-2) increases at higher redshifts, and both, obscured and unobscured AGNs presented an anti-correlation between Lx and EW_Fe possibly associated with the decreasing of the torus covering factor as the AGN luminosity increases. We used the XCLUMPY model to characterize and confirm the detection of 2 Compton-thick AGNs, both with N_H > 5 x 10^24 cm^-2 and z > 1. We found 10 bright AGNs that shows X-ray soft emission with average blackbody temperature of 𝑘𝑡 = 0.12 ± 0.02 𝑘𝑒𝑉, and 6 super-Eddington sources (i.e. lambda_Edd > 1). The resulting catalog of X-ray spectral parameters serves as a basis for further investigations into the properties of the AGN population within the Lockman-SpReSO project.

A significant fraction of gamma-ray sources are classified as Active Galactic Nuclei (AGN), which are among the most energetic phenomena in the universe. Most gamma-ray emitting AGNs are categorized as blazars or radio galaxies, both of which possess relativistic jets powered by supermassive black holes. There are many open questions in this field, such as the precise physical mechanisms that produce very high-energy emissions (VHE, >0.1 TeV) and their connections to high-energy neutrinos and cosmic-ray production.In this talk, we present various results and ongoing projects that utilize data from the Fermi Gamma-ray Space Telescope and the High Altitude Water Cherenkov (HAWC) gamma-ray observatory to enhance our understanding of this phenomenon. These projects include the characterization of the average VHE emission of AGN, fitting physical scenarios to their multiwavelength spectral energy distributions, and searching for new sources using years of accumulated data.

I will introduce dual and binary AGN by presenting key findings, physical processes, and relevant timescales. Also, I will address ideas relating to mergers as important drivers of galaxy evolution and their relevance as a natural channel for the formation of binary and dual AGN. We will review the current observational evidence for close binaries, duals, and triple AGN and discuss the implications and relevance for detecting these objects.

Using Sloan Digital Sky Survey spectra, we applied an automatic method to search for outflows in four large samples of active galactic nuclei (AGN) at low redshifts (z < 0.4), one of broad-line Seyfert type 1 (Sy1), and three of narrow-line separated into three spectral activity classes: radio-loud galaxies; radio-quiet Seyfert type 2 (Sy2); and LINERs. In general, the probability of detecting an OF decreases along the sequence Sy1→Sy2→LINER/ radio-loud galaxies and independently of the AGN class, the wind velocity, traced by W80, increases with the AGN luminosity. Moreover, W80 is systematically higher in radio-loud galaxies or any of the other AGN classes when detected in radio. These results support the idea that there are two main modes of production of outflow, the radiative mode dominant in radio-quiet AGN and the jet mode dominant in radio-loud galaxies, although both modes could also happen simultaneously at different levels. Our analysis revealed that, independently of the AGN spectral class, (1) galaxy hosts with outflows have systematically later morphological types and higher star formation rates (SFRs) than their counterparts without outflows, (2) they show no evidence of AGN quenching or triggering of star formation. These results are consistent with a scenario explaining the different AGN classes as consequences of different formation processes of galaxies: early-type galaxies (LINERs and radio-loud galaxies) formed bigger bulges and more massive SMBHs, exhausting their reservoir of gas more rapidly than late-type galaxies (Sy2 and Sy1), and thereby quenching their star formation and starving their SMBHs.

Low Surface Brightness Galaxies (LSBGs) constitute a substantial fraction of galaxies in the local Universe, being primarily bulge-less, late-type galaxies, bluer and more gas-rich than their high surface brightness counterparts (HSBG). In this talk I will explore the nature of these kind of galaxies, confronting the results of hydrodynamic cosmological simulations with large observational samples. We show that LSBGs span a wide range of stellar masses and tend to be more extended and less massive than their high surface brightness counterparts (HSBGs). Their distinct structural properties are closely linked to their higher specific angular momentum and halo spin parameters, which lead to suppressed central concentrations and lower-mass central black holes. We explore the environments of LSBGs, finding that while large-scale cosmic web structures do not play a dominant role, local environmental effects —such as those found in groups and clusters— strongly influence LSBG morphology and abundance. In particular, rotation-dominated LSBGs prefer low-density environments, whereas dispersion-dominated ones are more common in high-density regions, suggesting different evolutionary pathways driven by local interactions. Finally, we examine the incidence of stellar bars in LSBGs and find that their lower bar fraction, relative to HSBGs, can be attributed primarily to their higher spin and gas content. Interestingly, tidal interactions —while having limited impact overall— appear to enhance bar formation in LSBGs more than in HSBGs. These results offer a unified picture in which the internal properties of LSBGs, combined with local environmental influences, shape their structural and dynamical evolution.

We present some results about the interplay between the dynamics of galaxies in compact-like groups and their star formation history, by using a LCDM cosmological simulation. General trends noted, as well as specific examples of compact groups, are presented and compared with observations.

In this talk I will discuss the expectations of the Vera Rubin Observatory to discover about a hundred thousands of galaxy scale new lenses and how these systems will offer oportunities to constrain the dark matter microphyisics. I will present an example bases on realistic synthetic data, where we try to differentiate between two different models. I’ll also discuss other uses of strong lensing systems in cosmology.

In the dissipative interaction of two quantized fields it si shown how nonunitary transformations lead to non-Hermitian Hamiltonians and allow exact solution of the Schroedinger equation. It is also shown how to realize nonunitary transformations in waveguide arrays to produce your own non-Hermitian Hamiltonian.

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