Does mentoring frequency matter? Effects on dropout rates and average grades among university students Miguel A. Alonso García, Aitana González Ortiz de Zárate, Irene Aliagas, Ma Ángeles Gómez-Flechoso Evaluation and Program Planning, 2026 Mentoring programs are essential in supporting first-year university students by reducing dropout rates and enhancing grades. However, the optimal number of meetings has not been extensively explored. This article examines how the number of meetings influences outcomes across disciplines and demographics. Using a quasi-experimental approach with 9,063 students (4+ meetings, n =3,074; ≤3 meetings, n =2,958; 0 meetings, n =3,031), who belonged to different areas of study, we analyzed dropout rates and grades through chi-square tests, phi statistics, ANOVA, and Bonferroni adjustments. Results indicate that more meetings generally lead to lower dropout rates and higher grades. However, exceptions exist in Science and Engineering, ≤3 meetings were as effective as 4+ meetings at reducing dropouts; while in Arts, Humanities, Social, and Legal Sciences, they were equally effective at improving grades. These findings suggest institutions can optimize mentoring strategies by tailoring programs to specific student needs, improving educational outcomes and fostering success. • Four or more mentoring sessions significantly reduced dropout rates and improved academic performance, supporting the importance of intervention intensity in program design. • Three or fewer sessions proved more beneficial than no mentoring but were insufficient to reduce dropout across disciplines, highlighting the need for context-sensitive program adaptation. • In Arts, Humanities, and Social Sciences, three sessions were as effective as four or more for improving grades, illustrating the value of discipline-specific planning. • Mentoring had a positive effect on male students even with minimal contact, whereas female students only showed significant gains with four or more sessions, underscoring the importance of equity-driven program strategies.
Peer mentoring, university dropout and academic performance before, during, and after the pandemic in Spain Aitana González-Ortiz-de-Zárate, Miguel Aurelio Alonso-García, María de los Ángeles Gómez-Flechoso, Irene Aliagas Evaluation and Program Planning, 2025 Peer mentoring programs in higher education aim to facilitate student integration and enhance both retention and academic performance. This study investigated the effectiveness of a peer mentoring program at a Spanish university over five academic years (2018–19–2022–23), encompassing the COVID-19 pandemic. Employing a quasi-experimental posttest-only control group design, we analyzed data from 4962 students (mentees: n = 2481; controls: n = 2481). Statistical analyses included independent t-tests, Cohen's d, phi coefficient, chi-square tests, and two-way ANOVA. Results demonstrated significantly lower dropout rates and higher academic performance among mentees compared to controls across all study years. These positive effects were observed inconsistently across most of the studied student characteristics, including gender, study choice order, region of origin, and field of study. Furthermore, our findings supported the mediating role of academic performance in the relationship between peer mentoring and dropout. This research provides valuable empirical evidence that supports the theoretical frameworks on peer mentoring, student development, and successful integration within the context of higher education, particularly during times of crisis. • Positive impact of peer mentoring on university dropout and academic performance. • Effects remained consistent over five years, including the COVID-19 pandemic. • Impacts were inconsistent across gender, field of study, and other demographics. • Peer mentoring affected dropout directly and indirectly through academic performance.
Stellar tidal streams around nearby spiral galaxies with deep imaging from amateur telescopes David Martínez-Delgado, Michael Stein, Joanna D. Sakowska, M. Maurice Weigelt, Javier Román, Giuseppe Donatiello, Santi Roca-Fàbrega, Mischa Schirmer, Eva K. Grebel, Teymoor Saifollahi, Jeff Kanipe, M. Angeles Gómez-Flechoso, Mohammad Akhlaghi, Behnam Javanmardi, Gang Wu, Sepideh Eskandarlou, Dominik J. Bomans, Cristian Henkel, Adam Block, Mark Hanson, Johannes Schedler, Karel Teuwen, R. Jay GaBany, Alvaro Ibañez Perez, Ken Crawford, Wolfgang Promper, Manuel Jimenez, Sílvia Farràs-Aloy, Juan Miró-Carretero Astronomy and Astrophysics, 2025 Context. Tidal interactions between massive galaxies and their satellites are fundamental processes in a universe with a Λ cold dark matter (ΛCDM) cosmology, and they redistribute material into faint features that preserve records of past galactic interactions. While stellar streams in the Local Group impressively demonstrate satellite disruption, they do not constitute a statistically significant sample. Constructing a substantial catalog of stellar streams beyond the Local Group remains challenging due to the difficulties in obtaining sufficiently deep wide-field images of galaxies. Despite their potential to illuminate dark matter distribution and galaxy formation processes overall, stellar streams remain underutilized as cosmological probes. Aims. The Stellar Tidal Stream Survey (STSS) addresses this observational gap by leveraging amateur telescopes to obtain deep scientific-grade images of galactic outskirts capable of building a more statistically meaningful sample of stellar streams. Methods. Over the past decade, the STSS has acquired deep (up to surface brightness limit ∼28.3 mag/arcsec2 in the r-band) wide-field images of 16 nearby Milky Way analog galaxies using a coordinated network of robotic amateur telescopes, which enabled the survey to avoid the issues associated with “mosaicking” smaller images taken with a single professional telescope. Results. Our survey revealed a diverse range of previously unreported faint features related to dwarf satellite accretion, including stellar streams, shells, and umbrella-like structures. We serendipitously discovered an ultra-diffuse galaxy (NGC150-UDG1) that shows hints of tidal tails. Conclusions. The STSS demonstrates the suitability of modern amateur telescopes to detect and study faint, diffuse structures in large fields around nearby spiral galaxies. Their economic and accessibility advantages enable larger statistical samples with deep imaging, which are essential for testing galaxy formation models and constraining the frequency and properties of minor merger events in the local Universe.
Extragalactic stellar tidal streams: Observations meet simulation Juan Miró-Carretero, María A. Gómez-Flechoso, David Martínez-Delgado, Andrew P. Cooper, Santi Roca-Fàbrega, Mohammad Akhlaghi, Annalisa Pillepich, Konrad Kuijken, Denis Erkal, Tobias Buck, Wojciech A. Hellwing, Sownak Bose, Giuseppe Donatiello, Carlos S. Frenk Astronomy and Astrophysics, 2025 Context. According to the well-established hierarchical framework for galaxy evolution, galaxies grow through mergers with other galaxies. The ΛCDM cosmological model predicts that the stellar halos of massive galaxies are rich in remnants resulting from minor mergers. Stellar Streams Legacy Survey (SSLS) has provided a first release of a catalogue with a statistically significant sample of stellar streams in the local Universe, detected in deep images from DESI Legacy Surveys and Dark Energy Survey (DES). Aims. The main objective is to compare observations of stellar tidal streams from the SSLS catalogue with predictions from state-of-the-art cosmological simulations regarding their abundance, up to a redshift of z < 0.02, according to the ΛCDM model. Methods. In particular, we used the outcome of cosmological simulations from Copernicus Complexio, TNG50 of the IllustrisTNG project, and Auriga to generate mock images of nearby halos and search for stellar streams. We compared the stream frequency and characteristics found in these images, as well as the results of a photometric analysis of the simulations data with DES observations. Results. We found a generally good agreement between the real images and the simulated ones regarding frequency and photometry of streams, while we found differences in the stream morphology between the observations and the simulations, and among the simulations themselves. By varying the sky background of the synthetic images to emulate different surface brightness limit levels, we were also able to obtain predictions for the detection rate of stellar tidal streams up to a surface brightness limit of 35 mag arcsec−2. Conclusions. The cosmological simulations predict that with an instrument akin to the one used in DES, it would be necessary to attain a surface brightness limit of 32 mag arcsec−2 in the r-band to achieve a frequency of up to ∼70% in the detection of stellar tidal streams around galaxies in the redshift range considered here.
Design and expert validation of a value-based indicator system for evaluating university peer mentoring programmes Marc Pérez Burriel, Esperanza Villar-Hoz, Sara Malo, Natàlia Cuenca-Balañà, Miguel Aurelio Alonso García, et al. Journal of Further and Higher Education, 2025 Widespread implementation of peer mentoring programmes in universities has produced mixed results – with some significant successes but also some disillusionment. These contradictory results suggest that mentoring operates in a context of systemic complexity, where multiple interconnected factors interact. One relevant aspect is the axiological dimension inherent in mentoring relationships and in negotiating the purpose and expectations of the various stakeholders involved in the process. The aim of this study is to design and validate a system of value-based indicators to evaluate the process and outcomes of a university peer mentoring program for first-year undergraduate students. The Delphi method was used for validation, with the participation of 24 experts, including seven former mentors, three university professors specialised in evaluation indicators, six experts in values and eight experts in university mentoring programmes. This methodology, which makes use of expert input, allowed us to refine the definitions of values and select the evaluation indicators that best reflected those values. From the study findings, we present a set of 41 value-based indicators based on seven core values. The results are discussed in relation to the theoretical model used and include both the limitations of the research and proposals for future studies. This study aims to contribute to the field by emphasising the importance of explicitly addressing the axiological dimension in mentoring programmes – an aspect often overlooked in mentoring research.
Extragalactic stellar tidal streams in the Dark Energy Survey Juan Miró-Carretero, David Martínez-Delgado, María A. Gómez-Flechoso, Andrew Cooper, Mohammad Akhlaghi, Giuseppe Donatiello, Konrad Kuijken, Dustin Lang, Dmitry Makarov, Seppo Laine, Santi Roca-Fàbrega Astronomy and Astrophysics, 2024 Context. Stellar tidal streams are a key tracer of galaxy evolution and have the potential to provide an indirect means for tracing dark matter. For the Local Group, many diffuse substructures have been identified and their link to galaxy evolution has been traced. However, the Local Group does not offer a statistically significant sample of stellar tidal streams. Thus, an analysis of a larger sample beyond the Local Group is required to better probe the frequency and characteristics of these streams to verify whether these properties are in agreement with the predictions of the ΛCDM model and its implementation in cosmological simulations, taking into account the impact of the baryonic physics modelling. Aims. The main scope of the Stellar Stream Legacy Survey is to obtain a statistically significant sample of stellar streams in the local Universe to be able to trace and study minor mergers and their contribution to galaxy evolution with respect to the ΛCDM theory. For that purpose, we are carrying out the first systematic survey of faint stellar debris from tidally disrupted dwarf satellites around nearby galaxies up to a distance of 100 Mpc. Methods. In this paper, we present a catalogue with the results of the first harvest of stellar tidal streams found by visual inspection in deep images of ∼700 galaxies from the Dark Energy Survey (DES). We also include, for the first time, a photometric characterisation of the streams obtained by measuring their surface brightnesses and colours. Results. We found a total of 63 streams in our sample at distances between 40 and 100 Mpc, including 58 that were not previously reported. We measured their average surface brightness for the g band, the r band and the z band, to be 28.35 ± 0.20, 27.81 ± 0.13, and 27.62 ± 0.09 mag arcsec−2, respectively. By applying a statistical analysis to our findings, we obtained a stream detection frequency of 9.1% ± 1.1% for the given surface brightness limit of the DES image sample, in agreement with previous studies. We identified stream progenitors in 5–14% of our stream sample, depending on the confidence level. Conclusions. The first catalogue of streams in the local Universe presented here will be complemented by future stream surveys within the Stellar Stream Legacy Survey and can be exploited in studies pertaining to galaxy evolution and cosmological models. In this work, we have learnt that the faintest measured stream surface brightness can be significantly brighter than the surface brightness limit of an image measured at the pixel level (in our case up to ∼1 mag arcsec−2 for the r band) mainly due to correlated noise present in the images.
The Origin of Kinematically Persistent Planes of Satellites as Driven by the Early Evolution of the Cosmic Web in ΛCDM Matías Gámez-Marín, Isabel Santos-Santos, Rosa Domínguez-Tenreiro, Susana E. Pedrosa, Patricia B. Tissera, M. Ángeles Gómez-Flechoso, Héctor Artal Astrophysical Journal, 2024 Kinematically persistent planes (KPPs) of satellites are fixed sets of satellites co-orbiting around their host galaxy, whose orbital poles are conserved and clustered across long cosmic time intervals. They play the role of “skeletons,” ensuring the long-term durability of positional planes. We explore the physical processes behind their formation in terms of the dynamics of the local cosmic web (CW), characterized via the so-called Lagrangian volumes (LVs) built up around two zoom-in, cosmological hydro-simulations of Milky Way–mass disk galaxy + satellites systems, where three KPPs have been identified. By analyzing the LV deformations in terms of the reduced tensor of inertia (TOI), we find an outstanding alignment between the LV principal directions and the KPP satellites’ orbital poles. The most compressive local mass flows (along the e ˆ 3 eigenvector) are strong at early times, feeding the so-called e ˆ 3 -structure, while the smallest TOI axis rapidly decreases. The e ˆ 3 -structure collapse marks the end of this regime and is the timescale for the establishment of satellite orbital pole clustering when the Universe is ≲4 Gyr old. KPP protosatellites aligned with e ˆ 3 are those whose orbital poles are either aligned from early times or have been successfully bent at e ˆ 3 -structure collapse. KPP satellites associated with e ˆ 1 tend to have early trajectories already parallel to e ˆ 3 . We show that KPPs can arise as a result of the ΛCDM-predicted large-scale dynamics acting on particular sets of protosatellites, the same dynamics that shape the local CW environment.
Once in a blue stream: Detection of recent star formation in the NGC 7241 stellar stream with MEGARA David Martínez-Delgado, Santi Roca-Fàbrega, Armando Gil de Paz, Denis Erkal, Juan Miró-Carretero, Dmitry Makarov, Karina T. Voggel, Ryan Leaman, Walter Bolchin, Sarah Pearson, Giuseppe Donatiello, Evgenii Rubtsov, Mohammad Akhlaghi, M. Angeles Gomez-Flechoso, Samane Raji, Dustin Lang, Adam Block, Jesus Gallego, Esperanza Carrasco, María Luisa García-Vargas, Jorge Iglesias-Páramo, Sergio Pascual, Nicolas Cardiel, Ana Pérez-Calpena, Africa Castillo-Morales, Pedro Gómez-Alvarez Astronomy and Astrophysics, 2024 Aims. In this work we study the striking case of a narrow blue stream with a possible globular cluster-like progenitor around the NGC 7241 galaxy and its foreground dwarf companion. We want to figure out if the stream was generated by tidal interaction with NGC 7241 or if it first interacted with the foreground dwarf companion and later both fell together toward NGC 7241. Methods. We used four sets of observations, including a follow-up spectroscopic study of this stream based on data taken with the MEGARA instrument at the 10.4 m Gran Telescopio Canarias using the integral field spectroscopy mode, the Mount Lemmon 0.80 m telescope, the Telescopio Nazionale Galileo, the DESI Imaging Legacy surveys, and GALEX archival data. We also used high-resolution zoomed-in cosmological simulations. Results. Our data suggest that the compact object we detected in the stream is a foreground Milky Way halo star. Near this compact object we detect emission lines overlapping a less compact, bluer, and fainter blob of the stream that is clearly visible in both ultraviolet and optical deep images. From its heliocentric systemic radial velocity derived from the [O III]λ5007 Å lines (Vsyst = 1548.58 ± 1.80 km s−1) and new UV and optical broadband photometry, we conclude that this overdensity could be the actual core of the stream, with an absolute magnitude of Mg ∼ −10 and a g − r = 0.08 ± 0.11, consistent with a remnant of a low-mass dwarf satellite undergoing a current episode of star formation. From the width of the stream and assuming a circular orbit, we calculate that the progenitor mass can be typical of a dwarf galaxy, but it could also be substantially lower if the stream is on a very radial orbit or if it was created by tidal interaction with the companion dwarf instead of with NGC 7241. These estimates also suggest that this is one of the lowest mass streams detected to date beyond the Local Group. Finally, we find that blue stellar streams containing star formation regions are commonly predicted by high-resolution cosmological simulations of galaxies lighter than the Milky Way. This scenario is consistent with the processes explaining the bursty star formation history of some dwarf satellites, which are followed by a gas depletion and a fast quenching once they enter within the virial radius of their host galaxies for the first time. Thus, it is likely that the stream’s progenitor is undergoing a star formation burst comparable to those that have shaped the star formation history of several Local Group dwarfs in the last few gigayears.
Galactoseismology in cosmological simulations Vertical perturbations by dark matter, satellite galaxies, and gas B. García-Conde, T. Antoja, S. Roca-Fàbrega, F. Gómez, P. Ramos, N. Garavito-Camargo, M. A. Gómez-Flechoso Astronomy and Astrophysics, 2024 Context. Complex models recently became available for studying the dynamics of disk galaxies such as the Milky Way (MW). These models include the global dynamics from dwarf satellite galaxies, dark matter halo structure, gas infall, and stellar disks in a cosmological context. Aims. We use a MW model from a suite of high-resolution hydrodynamical cosmological simulations named GARROTXA to establish the relationship between the vertical disturbances seen in its galactic disk and multiple perturbations from the dark matter halo, satellites, and gas. Methods. We calculated the bending modes in the galactic disk in the last 6 Gyr of evolution. We computed the vertical acceleration exerted by dark matter and gas in order to quantify the impact of these components on the disk, and compared this with the bending behavior with Fourier analysis. Results. We find complex bending patterns at different radii and times, such as an inner retrograde mode with high frequency and an outer slower retrograde mode excited at different times. The amplitudes of these bending modes are highest during the early stages of formation of the thin disk (20 km s−1) and reach up to 8.5 km s−1 in the late disk evolution. We find that the infall of satellite galaxies leads to a tilt of the disk, and produces strong anisotropic gas accretion with a misalignment of 8° with subsequent star formation events and supernovae, creating significant vertical accelerations on the disk plane. The misalignment between the disk and the inner stellar and dark matter triaxial structure, which formed during the ancient assembly of the galaxy, also leads to a strong vertical acceleration of the stars. We also find dark matter subhalos that temporally coincide with the appearance of bending waves in certain periods. Conclusions. We conclude that several agents trigger the bending of the stellar disk and its phase spirals in this simulation, including satellite galaxies, dark subhalos, misaligned gaseous structures, and the inner dark matter profile. These phenomena coexist and influence each other, sometimes making it challenging to establish direct causality.
Effectiveness of a Peer Mentoring on University Dropout and Academic Performance Miguel A. Alonso, Aitana González-Ortiz-de-Zárate, M. Ángeles Gómez-Flechoso, Marco Castrillón Psicologia Educativa, 2024 Mentoring programs have been proposed to reduce dropout and increase academic performance. We analyzed the effect of peer mentoring on university dropout and academic performance in the context of Spain. We applied a quasi-experimental posttest-only control group design with 3,774 students (mentees, n = 1,887; control, n = 1,887). Mentees had participated in a peer mentoring program. We apply the student’s t-test, Cohen’s d, phi statistic, and chi-square statistic. Mentees exhibited lower dropout than controls and showed higher academic performance regardless of the area of knowledge. Results support the implementation of mentoring programs in Spanish universities with the goal of reducing student dropout and increasing academic performance. The research provides empirical evidence for theory building in higher education studies, developmental relationships, and integration programs.
Hidden depths in the local Universe: The Stellar Stream Legacy Survey David Martínez-Delgado, Andrew P. Cooper, Javier Román, Annalisa Pillepich, Denis Erkal, Sarah Pearson, John Moustakas, Chervin F. P. Laporte, Seppo Laine, Mohammad Akhlaghi, Dustin Lang, Dmitry Makarov, Alejandro S. Borlaff, Giuseppe Donatiello, William J. Pearson, Juan Miró-Carretero, Jean-Charles Cuillandre, Helena Domínguez, Santi Roca-Fàbrega, Carlos S. Frenk, Judy Schmidt, María A. Gómez-Flechoso, Rafael Guzman, Noam I. Libeskind, Arjun Dey, Benjamin A. Weaver, David Schlegel, Adam D. Myers, Frank G. Valdes Astronomy and Astrophysics, 2023
A giant umbrella-like stellar stream around the tidal ring galaxy NGC 922 David Martínez-Delgado, Santi Roca-Fàbrega, Juan Miró-Carretero, Maria Angeles Gómez-Flechoso, Javier Romàn, Giuseppe Donatiello, Judy Schmidt, Dustin Lang, Mohammad Akhlaghi, Mark Hanson Astronomy and Astrophysics, 2023
Understanding planes of satellites I. Santos-Santos, H. Artal, R. Domínguez-Tenreiro, P. B. Tissera, S. E. Pedrosa, M. A. Gómez-Flechoso, C. B. Brook, L. Bignone, A. Serna Proceedings of the International Astronomical Union, 2019
Understanding planes of satellites Proceedings of the 13th Scientific Meeting of the Spanish Astronomical Society Highlights of Spanish Astrophysics X Sea 2018, 2018
DISCOVERY of AN ULTRA-DIFFUSE GALAXY in the PISCES-PERSEUS SUPERCLUSTER David Martínez-Delgado, Ronald Läsker, Margarita Sharina, Elisa Toloba, Jürgen Fliri, Rachael Beaton, David Valls-Gabaud, Igor D. Karachentsev, Taylor S. Chonis, Eva K. Grebel, Duncan A. Forbes, Aaron J. Romanowsky, J. Gallego-Laborda, Karel Teuwen, M. A. Gómez-Flechoso, Jie Wang, Puragra Guhathakurta, Serafim Kaisin, Nhung Ho Astronomical Journal, 2016
Ejemplos de análisis cuantitativo de imágenes de infrarrojos obtenidas por termografía activa para la detección de patologías de humedades Rehabend, 2014
The orbital distribution of satellite galaxies: Cosmological correlations and origin Proceedings of the 9th Scientific Meeting of the Spanish Astronomical Society Highlights of Spanish Astrophysics Vi Sea 2010, 2010
A comprehensive model for the Monoceros tidal stream J. Penarrubia, D. Martinez‐Delgado, H. W. Rix, M. A Gomez‐Flechoso, J. Munn, H. Newberg, E. F. Bell, B. Yanny, D. Zucker, E. K. Grebel Astrophysical Journal, 2005