Pub Date : 2025-02-25DOI: 10.1051/0004-6361/202451786
M. Manteiga, R. Santoveña, M. A. Álvarez, C. Dafonte, M. G. Penedo, S. Navarro, L. Corral
Context. The rapid expansion of large-scale spectroscopic surveys has highlighted the need to use automatic methods to extract information about the properties of stars with the greatest efficiency and accuracy, and also to optimise the use of computational resources.Aims. We developed a method based on generative adversarial networks (GANs) to disentangle the physical (effective temperature and gravity) and chemical (metallicity and overabundance of α elements with respect to iron) atmospheric properties in astronomical spectra. Using a projection of the stellar spectra, commonly called latent space, in which the contribution due to one or several main stellar physicochemical properties is minimised while others are enhanced, it was possible to maximise the information related to certain properties. This could then be extracted using artificial neural networks (ANNs) as regressors, with a higher accuracy than a reference method based on the use of ANNs that had been trained with the original spectra.Methods. Our model utilises auto-encoders, comprising two ANNs: an encoder and a decoder that transform input data into a low-dimensional representation known as latent space. It also uses discriminators, which are additional neural networks aimed at transforming the traditional auto-encoder training into an adversarial approach. This is done to reinforce the astrophysical parameters or disentangle them from the latent space. We describe our Generative Adversarial Networks for Disentangling and Learning Framework (GANDALF) tool in this article. It was developed to define, train, and test our GAN model with a web framework to show visually how the disentangling algorithm works. It is open to the community in Github.Results. We demonstrate the performance of our approach for retrieving atmospheric stellar properties from spectra using Gaia Radial Velocity Spectrograph (RVS) data from DR3. We used a data-driven perspective and obtained very competitive values, all within the literature errors, and with the advantage of an important dimensionality reduction of the data to be processed.
{"title":"Disentangling stellar atmospheric parameters in astronomical spectra using generative adversarial neural networks","authors":"M. Manteiga, R. Santoveña, M. A. Álvarez, C. Dafonte, M. G. Penedo, S. Navarro, L. Corral","doi":"10.1051/0004-6361/202451786","DOIUrl":"https://doi.org/10.1051/0004-6361/202451786","url":null,"abstract":"<i>Context<i/>. The rapid expansion of large-scale spectroscopic surveys has highlighted the need to use automatic methods to extract information about the properties of stars with the greatest efficiency and accuracy, and also to optimise the use of computational resources.<i>Aims<i/>. We developed a method based on generative adversarial networks (GANs) to disentangle the physical (effective temperature and gravity) and chemical (metallicity and overabundance of α elements with respect to iron) atmospheric properties in astronomical spectra. Using a projection of the stellar spectra, commonly called latent space, in which the contribution due to one or several main stellar physicochemical properties is minimised while others are enhanced, it was possible to maximise the information related to certain properties. This could then be extracted using artificial neural networks (ANNs) as regressors, with a higher accuracy than a reference method based on the use of ANNs that had been trained with the original spectra.<i>Methods<i/>. Our model utilises auto-encoders, comprising two ANNs: an encoder and a decoder that transform input data into a low-dimensional representation known as latent space. It also uses discriminators, which are additional neural networks aimed at transforming the traditional auto-encoder training into an adversarial approach. This is done to reinforce the astrophysical parameters or disentangle them from the latent space. We describe our Generative Adversarial Networks for Disentangling and Learning Framework (GANDALF) tool in this article. It was developed to define, train, and test our GAN model with a web framework to show visually how the disentangling algorithm works. It is open to the community in Github.<i>Results<i/>. We demonstrate the performance of our approach for retrieving atmospheric stellar properties from spectra using <i>Gaia<i/> Radial Velocity Spectrograph (RVS) data from DR3. We used a data-driven perspective and obtained very competitive values, all within the literature errors, and with the advantage of an important dimensionality reduction of the data to be processed.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"85 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143495181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202451706
H. C. Yu, J. Hong, M. D. Ding
Context. Stellar flares have an impact on habitable planets. To relate the observations of the Sun with those of stars, one needs to use a Sun-as-a-star analysis, that is, to degrade the resolution of the Sun to a single point. With the data of the Sun-as-a-star observations, a simulation of solar flares is required to provide a systemic clue for the Sun-as-a-star study.Aims. We aim to explore how the Sun-as-a-star spectrum varies with the flare magnitude and location based on a grid of solar flare models.Methods. Using 1D radiative hydrodynamics modeling and multi-thread flare assumption, we obtained the spectrum of a typical flare with an enhancement of chromospheric lines.Results. The Sun-as-a-star spectrum of the Hα line shows enhanced and shifted components, which are highly dependent on the flare magnitude and location. The equivalent width ΔEW is a good indicator of energy release. The bisector method can be used to diagnose the sign of the line-of-sight velocity in the flaring atmosphere. For both Hα and Hβ lines, the Sun-as-a-star spectrum of a limb flare tends to be wider and shows a dip in the line center. In particular, we propose two quantities to diagnose the magnitude and location of the stellar flares. Besides this, caution must be taken when calculating the radiation energy, since the astrophysical flux-to-energy conversion ratio is dependent on the flare location.
{"title":"Sun-as-a-star analysis of simulated solar flares","authors":"H. C. Yu, J. Hong, M. D. Ding","doi":"10.1051/0004-6361/202451706","DOIUrl":"https://doi.org/10.1051/0004-6361/202451706","url":null,"abstract":"<i>Context.<i/> Stellar flares have an impact on habitable planets. To relate the observations of the Sun with those of stars, one needs to use a Sun-as-a-star analysis, that is, to degrade the resolution of the Sun to a single point. With the data of the Sun-as-a-star observations, a simulation of solar flares is required to provide a systemic clue for the Sun-as-a-star study.<i>Aims.<i/> We aim to explore how the Sun-as-a-star spectrum varies with the flare magnitude and location based on a grid of solar flare models.<i>Methods.<i/> Using 1D radiative hydrodynamics modeling and multi-thread flare assumption, we obtained the spectrum of a typical flare with an enhancement of chromospheric lines.<i>Results.<i/> The Sun-as-a-star spectrum of the H<i>α<i/> line shows enhanced and shifted components, which are highly dependent on the flare magnitude and location. The equivalent width ΔEW is a good indicator of energy release. The bisector method can be used to diagnose the sign of the line-of-sight velocity in the flaring atmosphere. For both H<i>α<i/> and H<i>β<i/> lines, the Sun-as-a-star spectrum of a limb flare tends to be wider and shows a dip in the line center. In particular, we propose two quantities to diagnose the magnitude and location of the stellar flares. Besides this, caution must be taken when calculating the radiation energy, since the astrophysical flux-to-energy conversion ratio is dependent on the flare location.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202452268
Aaron C. Trigg, Rachael Stewart, Alex Van Kooten, Eric Burns, Matthew G. Baring, Dmitry D. Frederiks, Daniela Huppenkothen, Brendan O’Connor, Oliver J. Roberts, Zorawar Wadiasingh, George Younes, Narayana Bhat, Michael S. Briggs, Malte Busmann, Adam Goldstein, Daniel Gruen, Lei Hu, Chryssa Kouveliotou, Michela Negro, Antonella Palmese, Arno Riffeser, Lorenzo Scotton, Dmitry S. Svinkin, Peter Veres, Raphael Zöller
Magnetar giant flares (MGFs) are the extremely short, energetic transients originating from highly magnetized neutron stars. When observed in nearby galaxies, these rare events are nearly indistinguishable from cosmological short gamma-ray bursts. We present the analysis of GRB 231115A, a candidate extragalactic MGF observed by Fermi/GBM and localized by INTEGRAL to the starburst galaxy M82. This burst exhibits distinctive temporal and spectral characteristics, including a short duration and a high peak energy, consistent with known MGFs. Time-resolved analysis reveals rapid spectral evolution and a clear correlation between luminosity and spectral hardness, providing robust evidence of relativistic outflows. Archival Chandra data identified point sources within the GRB 231115A localization consistent with the theoretical maximum persistent emission luminosity, though no definitive counterpart was found. Simulations indicate that any transient emission associated with GRB 231115A would require energies exceeding those of typical magnetar bursts to be detectable by current instruments. While the tail of a MGF originating from outside of the Milky Way and its satellite galaxies has never been detected, analysis suggests that such emission could be observable at M82’s distance with instruments like Swift/XRT or NICER, though no tail was identified for this event. These findings underscore the need for improved follow-up strategies and technological advancements to enhance MGF detection and characterization.
{"title":"Extragalactic magnetar giant flare GRB 231115A: Insights from Fermi/GBM observations","authors":"Aaron C. Trigg, Rachael Stewart, Alex Van Kooten, Eric Burns, Matthew G. Baring, Dmitry D. Frederiks, Daniela Huppenkothen, Brendan O’Connor, Oliver J. Roberts, Zorawar Wadiasingh, George Younes, Narayana Bhat, Michael S. Briggs, Malte Busmann, Adam Goldstein, Daniel Gruen, Lei Hu, Chryssa Kouveliotou, Michela Negro, Antonella Palmese, Arno Riffeser, Lorenzo Scotton, Dmitry S. Svinkin, Peter Veres, Raphael Zöller","doi":"10.1051/0004-6361/202452268","DOIUrl":"https://doi.org/10.1051/0004-6361/202452268","url":null,"abstract":"Magnetar giant flares (MGFs) are the extremely short, energetic transients originating from highly magnetized neutron stars. When observed in nearby galaxies, these rare events are nearly indistinguishable from cosmological short gamma-ray bursts. We present the analysis of GRB 231115A, a candidate extragalactic MGF observed by <i>Fermi<i/>/GBM and localized by INTEGRAL to the starburst galaxy M82. This burst exhibits distinctive temporal and spectral characteristics, including a short duration and a high peak energy, consistent with known MGFs. Time-resolved analysis reveals rapid spectral evolution and a clear correlation between luminosity and spectral hardness, providing robust evidence of relativistic outflows. Archival <i>Chandra<i/> data identified point sources within the GRB 231115A localization consistent with the theoretical maximum persistent emission luminosity, though no definitive counterpart was found. Simulations indicate that any transient emission associated with GRB 231115A would require energies exceeding those of typical magnetar bursts to be detectable by current instruments. While the tail of a MGF originating from outside of the Milky Way and its satellite galaxies has never been detected, analysis suggests that such emission could be observable at M82’s distance with instruments like <i>Swift<i/>/XRT or NICER, though no tail was identified for this event. These findings underscore the need for improved follow-up strategies and technological advancements to enhance MGF detection and characterization.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"89 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202450514
M. Clara, M. S. Cunha, P. P. Avelino, T. L. Campante, S. Deheuvels, D. R. Reese
Context. Grid-based modelling techniques have enabled the determination of stellar properties with great precision. The emergence of mixed modes during the subgiant phase, whose frequencies are characterised by a fast evolution with age, can potentially enable a precise determination of stellar properties, a key goal for future missions such as PLATO. However, current modelling techniques often consider grids that lack the resolution to properly account for the fast mode frequency evolution, consequently requiring the use of interpolation algorithms to cover the parameter space in between the grid models when applying model-data comparison methods.Aims. We aim to reproduce the ℓ = 1 mode frequencies within the accuracy limits associated with the typical observational errors (∼0.1 μHz) through interpolation on a grid of subgiant models.Methods. With that aim, we used variations of a two-step interpolation algorithm that considered linear and cubic splines interpolation methods and different age proxies (physical age, scaled age, and central density).Results. The best results were obtained using an algorithm that considers cubic splines interpolation along tracks, linear interpolation across tracks, and central density ρc as the age proxy. This combination yielded, on average, an absolute error of 0.14 μHz but reached maximum absolute errors on the interpolated frequencies of 1.2 μHz for some models, which is an order of magnitude higher than the typical observational errors. Furthermore, we investigated the impact on the accuracy of the interpolation from changes in the physical properties of the stars, showing, in particular, how the addition of core overshoot can significantly affect the interpolation results.
{"title":"Seismic modelling of subgiant stars: Testing different grid interpolation methods","authors":"M. Clara, M. S. Cunha, P. P. Avelino, T. L. Campante, S. Deheuvels, D. R. Reese","doi":"10.1051/0004-6361/202450514","DOIUrl":"https://doi.org/10.1051/0004-6361/202450514","url":null,"abstract":"<i>Context.<i/> Grid-based modelling techniques have enabled the determination of stellar properties with great precision. The emergence of mixed modes during the subgiant phase, whose frequencies are characterised by a fast evolution with age, can potentially enable a precise determination of stellar properties, a key goal for future missions such as PLATO. However, current modelling techniques often consider grids that lack the resolution to properly account for the fast mode frequency evolution, consequently requiring the use of interpolation algorithms to cover the parameter space in between the grid models when applying model-data comparison methods.<i>Aims.<i/> We aim to reproduce the <i>ℓ<i/> = 1 mode frequencies within the accuracy limits associated with the typical observational errors (∼0.1 μHz) through interpolation on a grid of subgiant models.<i>Methods.<i/> With that aim, we used variations of a two-step interpolation algorithm that considered linear and cubic splines interpolation methods and different age proxies (physical age, scaled age, and central density).<i>Results.<i/> The best results were obtained using an algorithm that considers cubic splines interpolation along tracks, linear interpolation across tracks, and central density <i>ρ<i/><sub>c<sub/> as the age proxy. This combination yielded, on average, an absolute error of 0.14 μHz but reached maximum absolute errors on the interpolated frequencies of 1.2 μHz for some models, which is an order of magnitude higher than the typical observational errors. Furthermore, we investigated the impact on the accuracy of the interpolation from changes in the physical properties of the stars, showing, in particular, how the addition of core overshoot can significantly affect the interpolation results.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"19 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202452758
Alexandra Kozyreva, Andrea Caputo, Petr Baklanov, Alexey Mironov, Hans-Thomas Janka
The fortunate proximity of the Type II supernova (SN) 2023ixf has allowed astronomers to follow its evolution from almost the moment of the collapse of the progenitor’s core. SN 2023ixf can be explained as an explosion of a massive star with an energy of 0.7 × 1051 erg but with a greatly reduced envelope mass, probably because of binary interaction. In our radiative-transfer simulations, the SN ejecta of 6 M⊙ interact with circumstellar matter (CSM) of (0.55–0.83) M⊙ extending to 1015 cm, which results in a light curve (LC) peak matching that of SN 2023ixf. The origin of this required CSM might be gravity waves originating from convective shell burning, which could enhance wind-like mass loss during the late stages of stellar evolution. The steeply rising low-luminosity flux during the first hours after observationally confirmed non-detection, however, cannot be explained by the collision of the energetic SN shock with the CSM. Instead, we consider it as a precursor that we can fit by the emission from (0.5–0.9) M⊙ of matter that was ejected with an energy of ∼1049 erg a fraction of a day before the main shock of the SN explosion reached the surface of the progenitor. The source of this energy injection into the outermost shell of the stellar envelope could also be dynamical processes related to the convective activity in the progenitor’s interior or envelope. Alternatively, the early rise of the LC could point to the initial breakout of a highly non-spherical SN shock or of fast-moving asymmetrically ejected matter that was swept out well ahead of the SN shock, potentially in a low-energy, nearly relativistic jet. We also discuss that pre-SN outbursts and LC precursors can be used to study or to constrain energy deposition in the outermost stellar layers by the decay of exotic particles, such as axions, which could be produced simultaneously with neutrinos in the newly formed hot neutron star. A careful analysis of the earliest few hours of the LCs of SNe can reveal elusive precursors and provide a unique window onto the surface activity of massive stars during their core collapse. This can greatly improve our understanding of stellar physics and consequently also offer new tools for searching for exotic particles.
{"title":"SN 2023ixf: An average-energy explosion with circumstellar medium and a precursor","authors":"Alexandra Kozyreva, Andrea Caputo, Petr Baklanov, Alexey Mironov, Hans-Thomas Janka","doi":"10.1051/0004-6361/202452758","DOIUrl":"https://doi.org/10.1051/0004-6361/202452758","url":null,"abstract":"The fortunate proximity of the Type II supernova (SN) 2023ixf has allowed astronomers to follow its evolution from almost the moment of the collapse of the progenitor’s core. SN 2023ixf can be explained as an explosion of a massive star with an energy of 0.7 × 10<sup>51<sup/> erg but with a greatly reduced envelope mass, probably because of binary interaction. In our radiative-transfer simulations, the SN ejecta of 6 M<sub>⊙<sub/> interact with circumstellar matter (CSM) of (0.55–0.83) M<sub>⊙<sub/> extending to 10<sup>15<sup/> cm, which results in a light curve (LC) peak matching that of SN 2023ixf. The origin of this required CSM might be gravity waves originating from convective shell burning, which could enhance wind-like mass loss during the late stages of stellar evolution. The steeply rising low-luminosity flux during the first hours after observationally confirmed non-detection, however, cannot be explained by the collision of the energetic SN shock with the CSM. Instead, we consider it as a precursor that we can fit by the emission from (0.5–0.9) M<sub>⊙<sub/> of matter that was ejected with an energy of ∼10<sup>49<sup/> erg a fraction of a day before the main shock of the SN explosion reached the surface of the progenitor. The source of this energy injection into the outermost shell of the stellar envelope could also be dynamical processes related to the convective activity in the progenitor’s interior or envelope. Alternatively, the early rise of the LC could point to the initial breakout of a highly non-spherical SN shock or of fast-moving asymmetrically ejected matter that was swept out well ahead of the SN shock, potentially in a low-energy, nearly relativistic jet. We also discuss that pre-SN outbursts and LC precursors can be used to study or to constrain energy deposition in the outermost stellar layers by the decay of exotic particles, such as axions, which could be produced simultaneously with neutrinos in the newly formed hot neutron star. A careful analysis of the earliest few hours of the LCs of SNe can reveal elusive precursors and provide a unique window onto the surface activity of massive stars during their core collapse. This can greatly improve our understanding of stellar physics and consequently also offer new tools for searching for exotic particles.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202451974
Gaoxiang Jin, Guinevere Kauffmann, Philip N. Best, Shravya Shenoy, Katarzyna Małek
The role of radio mode active galactic nuclei (AGN) feedback on galaxy evolution is still under debate. In this study we utilized a combination of radio continuum observations and optical integral field spectroscopic (IFS) data to explore the impact of radio AGN on the evolution of their host galaxies at global and subgalactic scales. We constructed a comprehensive radio-IFS sample comprising 5548 galaxies with redshift z < 0.15 by cross-matching the LOFAR Two-Metre Sky Survey (LoTSS) with the Mapping Nearby Galaxies at APO (MaNGA) survey. We revisited the tight linear radio continuum–star formation relation and quantify its intrinsic scatter, then used the relation to classify 616 radio-excess AGN with excessive radio luminosities over the values expected from their star formation rates. Massive radio AGN host galaxies are predominantly quiescent systems, but the quenching level shows no correlation with the jet luminosity. The mass assembly histories derived from the stellar population synthesis model fitting agree with the cosmological simulations incorporating radio-mode AGN feedback models. We observe that radio AGN hosts grow faster than a control sample of galaxies matched in stellar mass, and the quenching age (∼5 Gyr) is at larger lookback times than the typical radio jet age (< 1 Gyr). By stacking the spectra in different radial bins and comparing results for radio AGN hosts and their controls, we find emission line excess features in the nuclear region of radio AGN hosts. This excess is more prominent in low-luminosity, low-mass, and compact radio AGN. The [N II]/Hα ratios of the excessive emission line indicate that radio AGN or related jets are ionizing the surrounding interstellar medium in the vicinity of the nucleus. Our results support the scenario that the observed present-day radio AGN activity may help their host galaxies maintain quiescence through gas ionization and heating, but it is not responsible for the past quenching of their hosts.
{"title":"The host galaxies of radio AGN: New views from combining LoTSS and MaNGA observations","authors":"Gaoxiang Jin, Guinevere Kauffmann, Philip N. Best, Shravya Shenoy, Katarzyna Małek","doi":"10.1051/0004-6361/202451974","DOIUrl":"https://doi.org/10.1051/0004-6361/202451974","url":null,"abstract":"The role of radio mode active galactic nuclei (AGN) feedback on galaxy evolution is still under debate. In this study we utilized a combination of radio continuum observations and optical integral field spectroscopic (IFS) data to explore the impact of radio AGN on the evolution of their host galaxies at global and subgalactic scales. We constructed a comprehensive radio-IFS sample comprising 5548 galaxies with redshift <i>z<i/> < 0.15 by cross-matching the LOFAR Two-Metre Sky Survey (LoTSS) with the Mapping Nearby Galaxies at APO (MaNGA) survey. We revisited the tight linear radio continuum–star formation relation and quantify its intrinsic scatter, then used the relation to classify 616 radio-excess AGN with excessive radio luminosities over the values expected from their star formation rates. Massive radio AGN host galaxies are predominantly quiescent systems, but the quenching level shows no correlation with the jet luminosity. The mass assembly histories derived from the stellar population synthesis model fitting agree with the cosmological simulations incorporating radio-mode AGN feedback models. We observe that radio AGN hosts grow faster than a control sample of galaxies matched in stellar mass, and the quenching age (∼5 Gyr) is at larger lookback times than the typical radio jet age (< 1 Gyr). By stacking the spectra in different radial bins and comparing results for radio AGN hosts and their controls, we find emission line excess features in the nuclear region of radio AGN hosts. This excess is more prominent in low-luminosity, low-mass, and compact radio AGN. The [N II]/H<i>α<i/> ratios of the excessive emission line indicate that radio AGN or related jets are ionizing the surrounding interstellar medium in the vicinity of the nucleus. Our results support the scenario that the observed present-day radio AGN activity may help their host galaxies maintain quiescence through gas ionization and heating, but it is not responsible for the past quenching of their hosts.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"65 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202453468
M. C. Baglio, F. Coti Zelati, A. K. Hughes, F. Carotenuto, S. Campana, D. de Martino, S. E. Motta, A. Papitto, N. Rea, D. M. Russell, D. F. Torres, A. Di Marco, F. La Monaca, S. Covino, S. Giarratana, G. Illiano, A. Miraval Zanon, K. Alabarta, P. D’Avanzo, M. M. Messa
We present a comprehensive study of the flaring mode of the transitional millisecond pulsar (tMSP) PSR J1023+0038 during its X-ray sub-luminous state, using strictly simultaneous X-ray, UV, optical, and radio observations. The X-ray flares exhibit UV and optical counterparts and coincide with the brightest radio flare observed in the past decade, reaching 1.2 mJy at 6 GHz and lasting ∼1 hour. During the flare, the optical polarisation drops from ≃1.4% to ≃0.5%, indicating the emergence of an unpolarised component. We propose that the thickening of the disc, which enlarges the shock region between the pulsar wind and the accretion flow and may drive the X-ray flaring observed in tMSPs, enhances the ionisation level of the disc, thereby generating an increased number of free electrons. These electrons could then be channelled by magnetic field lines into the jet. This increased jet mass-loading could drive the associated radio and optical variability. The radio spectral evolution during flares is consistent with synchrotron self-absorption in jet ejecta or internal shocks within the compact jet. We infer radio polarisation upper limits (< 8.7%, < 2.3%, and < 8.2%, before, during, and after the radio flare) that further support a compact jet origin but do not rule out discrete ejections. Our findings suggest that tMSPs could serve as essential laboratories for investigating jet-launching mechanisms, mainly because they operate under very low mass accretion rates. This accretion regime has not been explored before in the context of accretion-ejection coupling.
{"title":"Multi-band study of the flaring mode emission in the transitional millisecond pulsar PSR J1023+0038","authors":"M. C. Baglio, F. Coti Zelati, A. K. Hughes, F. Carotenuto, S. Campana, D. de Martino, S. E. Motta, A. Papitto, N. Rea, D. M. Russell, D. F. Torres, A. Di Marco, F. La Monaca, S. Covino, S. Giarratana, G. Illiano, A. Miraval Zanon, K. Alabarta, P. D’Avanzo, M. M. Messa","doi":"10.1051/0004-6361/202453468","DOIUrl":"https://doi.org/10.1051/0004-6361/202453468","url":null,"abstract":"We present a comprehensive study of the flaring mode of the transitional millisecond pulsar (tMSP) PSR J1023+0038 during its X-ray sub-luminous state, using strictly simultaneous X-ray, UV, optical, and radio observations. The X-ray flares exhibit UV and optical counterparts and coincide with the brightest radio flare observed in the past decade, reaching 1.2 mJy at 6 GHz and lasting ∼1 hour. During the flare, the optical polarisation drops from ≃1.4% to ≃0.5%, indicating the emergence of an unpolarised component. We propose that the thickening of the disc, which enlarges the shock region between the pulsar wind and the accretion flow and may drive the X-ray flaring observed in tMSPs, enhances the ionisation level of the disc, thereby generating an increased number of free electrons. These electrons could then be channelled by magnetic field lines into the jet. This increased jet mass-loading could drive the associated radio and optical variability. The radio spectral evolution during flares is consistent with synchrotron self-absorption in jet ejecta or internal shocks within the compact jet. We infer radio polarisation upper limits (< 8.7%, < 2.3%, and < 8.2%, before, during, and after the radio flare) that further support a compact jet origin but do not rule out discrete ejections. Our findings suggest that tMSPs could serve as essential laboratories for investigating jet-launching mechanisms, mainly because they operate under very low mass accretion rates. This accretion regime has not been explored before in the context of accretion-ejection coupling.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"50 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202453391
A. Bushi, A. Botteon, D. Dallacasa, R. J. van Weeren, T. Venturi, M. Brüggen, F. Gastaldello, S. Giacintucci
Context. Head-tail radio galaxies are characterized by a head, corresponding to an elliptical galaxy, and two radio jets sweeping back from the head, forming an extended structure behind the host galaxy that is moving through the intracluster medium (ICM). This morphology arises from the interaction between the diffuse radio-emitting plasma and the surrounding environment. Sometimes, in galaxy clusters, revived fossil plasma can be found, and it traces old active galactic nucleus ejecta with a very steep spectrum that has been re-energized through processes in the ICM, unrelated to the progenitor radio galaxy.Aims. We focus on the study of the central region of Abell 1775, a galaxy cluster in an unclear dynamical state at a redshift of z = 0.07203. It hosts two giant radio-loud elliptical galaxies, the head-tail radio galaxy that ‘breaks’ at the position of a cold front detected in the X-rays, filamentary revived fossil plasma, and central diffuse emission. This study aims to investigate and constrain the spectral properties and trends along the head-tail, as well as the revived fossil plasma, to better understand the formation process of the non-thermal phenomena in A1775.Methods. We make use of observations at three frequencies performed with LOFAR at 144 MHz, and new deep uGMRT observations at 400 MHz and at 650 MHz.Results. We observe an overall steepening along the tail of the head-tail radio galaxy. In the radio colour-colour diagram, ageing models reproduce the emission of the head-tail. An unexpected brightness increase at the head of the tail suggests a complex bending of the jets. We derived the equipartition magnetic field and minimum pressure along the tail. We recovered the structure of the revived fossil plasma, which appears as thin filaments with ultra-steep spectra.Conclusions. We show that high-sensitivity, high-resolution observations at low frequencies are essential for detecting the full extent of the tail, enabling a deeper spectral analysis and resolving the structure and spectral properties of revived fossil plasma.
{"title":"The head-tail radio galaxy and revived fossil plasma in Abell 1775","authors":"A. Bushi, A. Botteon, D. Dallacasa, R. J. van Weeren, T. Venturi, M. Brüggen, F. Gastaldello, S. Giacintucci","doi":"10.1051/0004-6361/202453391","DOIUrl":"https://doi.org/10.1051/0004-6361/202453391","url":null,"abstract":"<i>Context.<i/> Head-tail radio galaxies are characterized by a head, corresponding to an elliptical galaxy, and two radio jets sweeping back from the head, forming an extended structure behind the host galaxy that is moving through the intracluster medium (ICM). This morphology arises from the interaction between the diffuse radio-emitting plasma and the surrounding environment. Sometimes, in galaxy clusters, revived fossil plasma can be found, and it traces old active galactic nucleus ejecta with a very steep spectrum that has been re-energized through processes in the ICM, unrelated to the progenitor radio galaxy.<i>Aims.<i/> We focus on the study of the central region of Abell 1775, a galaxy cluster in an unclear dynamical state at a redshift of <i>z<i/> = 0.07203. It hosts two giant radio-loud elliptical galaxies, the head-tail radio galaxy that ‘breaks’ at the position of a cold front detected in the X-rays, filamentary revived fossil plasma, and central diffuse emission. This study aims to investigate and constrain the spectral properties and trends along the head-tail, as well as the revived fossil plasma, to better understand the formation process of the non-thermal phenomena in A1775.<i>Methods.<i/> We make use of observations at three frequencies performed with LOFAR at 144 MHz, and new deep uGMRT observations at 400 MHz and at 650 MHz.<i>Results.<i/> We observe an overall steepening along the tail of the head-tail radio galaxy. In the radio colour-colour diagram, ageing models reproduce the emission of the head-tail. An unexpected brightness increase at the head of the tail suggests a complex bending of the jets. We derived the equipartition magnetic field and minimum pressure along the tail. We recovered the structure of the revived fossil plasma, which appears as thin filaments with ultra-steep spectra.<i>Conclusions.<i/> We show that high-sensitivity, high-resolution observations at low frequencies are essential for detecting the full extent of the tail, enabling a deeper spectral analysis and resolving the structure and spectral properties of revived fossil plasma.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"34 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202452217
Deaglan J. Bartlett, Marco Chiarenza, Ludvig Doeser, Florent Leclercq
Context.N-body simulations are computationally expensive and machine learning (ML) based emulation techniques have thus emerged as a way to increase their speed. Surrogate models are indeed fast, however, they are limited in terms of their trustworthiness due to potentially substantial emulation errors that current approaches are not equipped to correct.Aims. To alleviate this problem, we have introduced COmoving Computer Acceleration (COCA), a hybrid framework interfacing ML algorithm with an N-body simulator. The correct physical equations of motion are solved in an emulated frame of reference, so that any emulation error is corrected by design. Thus, we are able to find a solution for the perturbation of particle trajectories around the ML solution. This approach is computationally cheaper than obtaining the full solution and it is guaranteed to converge to the truth as the number of force evaluations is increased.Methods. Even though it is applicable to any ML algorithm and N-body simulator, we assessed this approach in the particular case of particle-mesh (PM) cosmological simulations in a frame of reference predicted by a convolutional neural network. In such cases, the time dependence is encoded as an additional input parameter to the network.Results. We find that COCA efficiently reduces emulation errors in particle trajectories, requiring far fewer force evaluations than running the corresponding simulation without ML. As a consequence, we were able to obtain accurate final density and velocity fields for a reduced computational budget. We demonstrate that this method exhibits robustness when applied to examples outside the range of the training data. When compared to the direct emulation of the Lagrangian displacement field using the same training resources, COCA’s ability to correct emulation errors results in more accurate predictions.Conclusions. Therefore, COCA makes N-body simulations cheaper by skipping unnecessary force evaluations, while still solving the correct equations of motion and correcting for emulation errors made by ML.
N体模拟计算成本高昂，因此基于机器学习（ML）的仿真技术应运而生，成为提高模拟速度的一种方法。代用模型的速度确实很快，但由于目前的方法无法纠正潜在的大量仿真错误，因此在可信度方面受到限制。为了缓解这一问题，我们引入了 COmoving Computer Acceleration (COCA)，这是一个将 ML 算法与 N-body 模拟器相结合的混合框架。正确的物理运动方程在仿真参照系中求解，因此任何仿真误差都能通过设计得到纠正。这样，我们就能找到围绕 ML 解法的粒子轨迹扰动解。这种方法的计算成本比获取完整解决方案更低，而且随着受力评估次数的增加，它还能保证收敛到真相。尽管这种方法适用于任何 ML 算法和 N-body 模拟器，我们还是在卷积神经网络预测的参照系中对粒子网格（PM）宇宙学模拟的特殊情况下评估了这种方法。在这种情况下，时间依赖性被编码为网络的附加输入参数。我们发现，COCA 能有效减少粒子轨迹的模拟误差，所需的力评估次数远远少于不使用 ML 的相应模拟。因此，我们能够以较少的计算预算获得精确的最终密度场和速度场。我们证明了这种方法在应用于训练数据范围之外的示例时表现出的鲁棒性。与使用相同训练资源直接模拟拉格朗日位移场相比，COCA 能够纠正模拟误差，从而获得更准确的预测结果。因此，COCA 通过跳过不必要的力评估，同时仍然求解正确的运动方程并纠正 ML 模拟错误，从而降低了 N 体模拟的成本。
{"title":"COmoving Computer Acceleration (COCA): N-body simulations in an emulated frame of reference","authors":"Deaglan J. Bartlett, Marco Chiarenza, Ludvig Doeser, Florent Leclercq","doi":"10.1051/0004-6361/202452217","DOIUrl":"https://doi.org/10.1051/0004-6361/202452217","url":null,"abstract":"<i>Context.N<i/>-body simulations are computationally expensive and machine learning (ML) based emulation techniques have thus emerged as a way to increase their speed. Surrogate models are indeed fast, however, they are limited in terms of their trustworthiness due to potentially substantial emulation errors that current approaches are not equipped to correct.<i>Aims.<i/> To alleviate this problem, we have introduced COmoving Computer Acceleration (COCA), a hybrid framework interfacing ML algorithm with an <i>N<i/>-body simulator. The correct physical equations of motion are solved in an emulated frame of reference, so that any emulation error is corrected by design. Thus, we are able to find a solution for the perturbation of particle trajectories around the ML solution. This approach is computationally cheaper than obtaining the full solution and it is guaranteed to converge to the truth as the number of force evaluations is increased.<i>Methods.<i/> Even though it is applicable to any ML algorithm and <i>N<i/>-body simulator, we assessed this approach in the particular case of particle-mesh (PM) cosmological simulations in a frame of reference predicted by a convolutional neural network. In such cases, the time dependence is encoded as an additional input parameter to the network.<i>Results.<i/> We find that COCA efficiently reduces emulation errors in particle trajectories, requiring far fewer force evaluations than running the corresponding simulation without ML. As a consequence, we were able to obtain accurate final density and velocity fields for a reduced computational budget. We demonstrate that this method exhibits robustness when applied to examples outside the range of the training data. When compared to the direct emulation of the Lagrangian displacement field using the same training resources, COCA’s ability to correct emulation errors results in more accurate predictions.<i>Conclusions.<i/> Therefore, COCA makes <i>N<i/>-body simulations cheaper by skipping unnecessary force evaluations, while still solving the correct equations of motion and correcting for emulation errors made by ML.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"495 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-24DOI: 10.1051/0004-6361/202452347
Maria Cristina Fortuna, Andrej Dvornik, Henk Hoekstra, Nora Elisa Chisari, Marika Asgari, Maciej Bilicki, Catherine Heymans, Hendrik Hildebrandt, Koen Kuijken, Angus H. Wright, Ji Yao
We study the properties of luminous red galaxies (LRGs) selected from the fourth data release of the Kilo Degree Survey (KiDS-1000) via galaxy-galaxy lensing of the background galaxies from KiDS-1000. We used a halo model formalism to interpret our measurements and obtain estimates of the halo masses as well as the satellite fractions of the LRGs, resulting in halo masses of 2.7 × 1012h−1 M⊙ < Mh < 2.6 × 1013h−1 M⊙. We studied the strength of intrinsic alignments (IA) using the position-shape correlations as a function of LRG luminosity, where we used a double power law to describe the relation between luminosity and halo mass to allow for a comparison with previous works. Here, we directly linked the observed IA of the (central) galaxy to the mass of the hosting halo, which is expected to be a fundamental quantity in establishing the alignment. We find that the dependence of the IA amplitude on halo mass is described well by a single power law, with an amplitude of A = 5.74 ± 0.32 and slope of βM = 0.44 ± 0.04, in the range of 1.9 × 1012h−1 M⊙ < Mh < 3.7 × 1014h−1 M⊙. We also find that both red and blue galaxies from the source sample associated with the LRGs are randomly oriented, with respect to the LRGs, although our detection significance is limited by the uncertainty in our photometric redshifts.
{"title":"KiDS-1000: Weak lensing and intrinsic alignment around luminous red galaxies","authors":"Maria Cristina Fortuna, Andrej Dvornik, Henk Hoekstra, Nora Elisa Chisari, Marika Asgari, Maciej Bilicki, Catherine Heymans, Hendrik Hildebrandt, Koen Kuijken, Angus H. Wright, Ji Yao","doi":"10.1051/0004-6361/202452347","DOIUrl":"https://doi.org/10.1051/0004-6361/202452347","url":null,"abstract":"We study the properties of luminous red galaxies (LRGs) selected from the fourth data release of the Kilo Degree Survey (KiDS-1000) via galaxy-galaxy lensing of the background galaxies from KiDS-1000. We used a halo model formalism to interpret our measurements and obtain estimates of the halo masses as well as the satellite fractions of the LRGs, resulting in halo masses of 2.7 × 10<sup>12<sup/> <i>h<i/><sup>−1<sup/> M<sub>⊙<sub/> < <i>M<i/><sub>h<sub/> < 2.6 × 10<sup>13<sup/> <i>h<i/><sup>−1<sup/> M<sub>⊙<sub/>. We studied the strength of intrinsic alignments (IA) using the position-shape correlations as a function of LRG luminosity, where we used a double power law to describe the relation between luminosity and halo mass to allow for a comparison with previous works. Here, we directly linked the observed IA of the (central) galaxy to the mass of the hosting halo, which is expected to be a fundamental quantity in establishing the alignment. We find that the dependence of the IA amplitude on halo mass is described well by a single power law, with an amplitude of <i>A<i/> = 5.74 ± 0.32 and slope of <i>β<i/><sub><i>M<i/><sub/> = 0.44 ± 0.04, in the range of 1.9 × 10<sup>12<sup/> <i>h<i/><sup>−1<sup/> M<sub>⊙<sub/> < <i>M<i/><sub>h<sub/> < 3.7 × 10<sup>14<sup/> <i>h<i/><sup>−1<sup/> M<sub>⊙<sub/>. We also find that both red and blue galaxies from the source sample associated with the LRGs are randomly oriented, with respect to the LRGs, although our detection significance is limited by the uncertainty in our photometric redshifts.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143477637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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