Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5249
Collin T. Christy, Kate D. Alexander, Tanmoy Laskar, Noah Franz, Adelle J. Goodwin, Jeniveve Pearson, Edo Berger, Yvette Cendes, Ryan Chornock, Deanne L. Coppejans, Tarraneh Eftekhari, Raffaella Margutti, James C. A. Miller-Jones, Melanie Krips, Enrico Ramirez-Ruiz, David J. Sand, Richard Saxton, Manisha Shrestha and Sjoert van Velzen
We present a detailed radio study of the tidal disruption events (TDEs) AT 2020zso and AT 2021sdu. Both exhibit transient radio emission beginning shortly after optical discovery and persisting for several years. For AT 2020zso, we identify two distinct radio flares. The first is detected in the radio ∼22 days after the optical peak, reaching a maximum of ∼1 yr post-discovery before fading. The second flare appears ∼800 days after discovery and results in the brief presence of two distinct components in the radio spectra, providing strong evidence for physically separate outflows. Both flares are consistent with nonrelativistic outflows, with velocities of v ≈ 0.1–0.2c and energies of E ∼ 1049 erg, propagating through a Bondi-like circumnuclear medium. Our analysis supports a scenario in which the first outflow is accretion driven, launched while the TDE disk is accreting at a relatively high Eddington fraction, whereas the second outflow is associated with a transition to an advection-dominated accretion flow. In contrast, the radio emission from AT 2021sdu is best explained by a slower (v ≈ 0.03c), less energetic outflow (E ∼ 1048 erg), combined with diffuse, nonvariable host emission that becomes dominant ∼500 days after discovery. Assuming free expansion, we infer an outflow launch date preceding the optical discovery date. This suggests that the outflow may originate from either the unbound stellar debris ejected during disruption or, alternatively, from a decelerating outflow. Our findings demonstrate the diversity of outflow properties in TDEs and highlight the observational challenges of interpreting late-time radio variability in the presence of host galaxy contamination.
{"title":"Dichotomy in Long-lived Radio Emission from Tidal Disruption Events AT 2020zso and AT 2021sdu: Multicomponent Outflows versus Host Contamination","authors":"Collin T. Christy, Kate D. Alexander, Tanmoy Laskar, Noah Franz, Adelle J. Goodwin, Jeniveve Pearson, Edo Berger, Yvette Cendes, Ryan Chornock, Deanne L. Coppejans, Tarraneh Eftekhari, Raffaella Margutti, James C. A. Miller-Jones, Melanie Krips, Enrico Ramirez-Ruiz, David J. Sand, Richard Saxton, Manisha Shrestha and Sjoert van Velzen","doi":"10.3847/1538-4357/ae5249","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5249","url":null,"abstract":"We present a detailed radio study of the tidal disruption events (TDEs) AT 2020zso and AT 2021sdu. Both exhibit transient radio emission beginning shortly after optical discovery and persisting for several years. For AT 2020zso, we identify two distinct radio flares. The first is detected in the radio ∼22 days after the optical peak, reaching a maximum of ∼1 yr post-discovery before fading. The second flare appears ∼800 days after discovery and results in the brief presence of two distinct components in the radio spectra, providing strong evidence for physically separate outflows. Both flares are consistent with nonrelativistic outflows, with velocities of v ≈ 0.1–0.2c and energies of E ∼ 1049 erg, propagating through a Bondi-like circumnuclear medium. Our analysis supports a scenario in which the first outflow is accretion driven, launched while the TDE disk is accreting at a relatively high Eddington fraction, whereas the second outflow is associated with a transition to an advection-dominated accretion flow. In contrast, the radio emission from AT 2021sdu is best explained by a slower (v ≈ 0.03c), less energetic outflow (E ∼ 1048 erg), combined with diffuse, nonvariable host emission that becomes dominant ∼500 days after discovery. Assuming free expansion, we infer an outflow launch date preceding the optical discovery date. This suggests that the outflow may originate from either the unbound stellar debris ejected during disruption or, alternatively, from a decelerating outflow. Our findings demonstrate the diversity of outflow properties in TDEs and highlight the observational challenges of interpreting late-time radio variability in the presence of host galaxy contamination.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5702
Karl D. Gordon, Petia Yanchulova Merica-Jones, Geoffrey C. Clayton, Ralph Bohlin, Marjorie Decleir, Claire E. Murray and Luciana Bianchi
Dust extinction curves provide one of the main avenues to understanding the detailed nature of dust grains and accounting for the effects of dust on observations of many astrophysical objects. For the first time, spectroscopic ultraviolet (UV) extinction curves are measured in M33 expanding the sample of Local Group galaxies with such measurements to five. These curves are based on Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra and literature photometry from the UV to the near-infrared. The four measured curves show large variations in their UV shapes including their 2175 Å bump and UV slope strengths. The average extinction of these four sightlines is lower than the averages for other Local Group Galaxies and does not follow the Milky Way (MW) R(V)–dependent relationship. The variations between UV extinction shape parameters and gas-to-dust ratios for the M33 sightlines fall within the variations seen in the combined sample of UV extinction curves in the MW, Large and Small Magellanic Clouds, and M31. The correlation with gas-to-dust ratio is much stronger than the correlation with global metallicity. This strengthens the picture that local conditions like radiation field density and shocks dominate over global galaxy properties like metallicity in determining the wavelength dependence of dust extinction.
{"title":"Large Variations Seen in First Ultraviolet Spectroscopic M33 Dust Extinction Curves","authors":"Karl D. Gordon, Petia Yanchulova Merica-Jones, Geoffrey C. Clayton, Ralph Bohlin, Marjorie Decleir, Claire E. Murray and Luciana Bianchi","doi":"10.3847/1538-4357/ae5702","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5702","url":null,"abstract":"Dust extinction curves provide one of the main avenues to understanding the detailed nature of dust grains and accounting for the effects of dust on observations of many astrophysical objects. For the first time, spectroscopic ultraviolet (UV) extinction curves are measured in M33 expanding the sample of Local Group galaxies with such measurements to five. These curves are based on Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra and literature photometry from the UV to the near-infrared. The four measured curves show large variations in their UV shapes including their 2175 Å bump and UV slope strengths. The average extinction of these four sightlines is lower than the averages for other Local Group Galaxies and does not follow the Milky Way (MW) R(V)–dependent relationship. The variations between UV extinction shape parameters and gas-to-dust ratios for the M33 sightlines fall within the variations seen in the combined sample of UV extinction curves in the MW, Large and Small Magellanic Clouds, and M31. The correlation with gas-to-dust ratio is much stronger than the correlation with global metallicity. This strengthens the picture that local conditions like radiation field density and shocks dominate over global galaxy properties like metallicity in determining the wavelength dependence of dust extinction.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5226
A. Archer, P. Bangale, J. T. Bartkoske, W. Benbow, J. H. Buckley, Y. Chen, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Errando, M. Escobar Godoy, S. Feldman, Q. Feng, S. Filbert, L. Fortson, A. Furniss, W. Hanlon, O. Hervet, C. E. Hinrichs, J. Holder, Z. Hughes, T. B. Humensky, M. Iskakova, W. Jin, M. N. Johnson, M. Kertzman, M. Kherlakian, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, S. Kundu, M. J. Lang, M. Lundy, G. Maier, C. McSorley, P. Moriarty, R. Mukherjee, W. Ning, S. O’Brien, M. Ohishi, R. A. Ong, A. Pandey, C. Poggemann, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, P. T. Reynolds, D. Ribeiro, L. Rizk, E. Roache, I. Sadeh, L. Saha, H. Salzmann, M. Santander, G. H. Sembroski, R. Shang, M. Splettstoesser, D. Tak, A. K. Talluri, I. Thoreson, J. V. Tucci, J. Valverde, D. A. Williams, S. L. Wong, T. Yoshikoshi and The VERITAS Collaboration
Significant gamma-ray emission between 1 TeV and 20 TeV from a point source, 1LHAASO J1219+2915, consistent with the location of the LINER/LLAGN galaxy NGC 4278 was recently reported by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These data were later split into active and quasi-quiet states, with most of the LHAASO significance coming from the active state (MJD 59449-59589). Subsequent analysis of Fermi-LAT and Swift-XRT observations have been used to explore the double-peaked broadband emission. Models of the spectral energy distribution (SED) are currently unconstrained due to the lack of contemporaneous multiwavelength data at either peak. Here, we report serendipitous observations of NGC 4278 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS), made possible by the contemporaneous observations of the nearby blazars 1ES 1218+304, 1ES 1215+303, and W Comae, each of which are located within 2° of NGC 4278. VERITAS did not detect any gamma-ray emission, and a flux upper limit was calculated. The flux upper limits constrain the photon spectrum of the quasi-quiet period, and together with Fermi-LAT, indicate a peak in the SED between 100 GeV and 2 TeV. We present an interpretation of the broadband SED that is based on acceleration of protons in the corona of the active galactic nuclei, followed by p–γ interactions and optically thin γ-ray emission. Within this framework, the implied neutrino signal is slightly below the current sensitivity of IceCube.
{"title":"VERITAS Observations Contemporaneous with the LHAASO Detection of NGC 4278","authors":"A. Archer, P. Bangale, J. T. Bartkoske, W. Benbow, J. H. Buckley, Y. Chen, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Errando, M. Escobar Godoy, S. Feldman, Q. Feng, S. Filbert, L. Fortson, A. Furniss, W. Hanlon, O. Hervet, C. E. Hinrichs, J. Holder, Z. Hughes, T. B. Humensky, M. Iskakova, W. Jin, M. N. Johnson, M. Kertzman, M. Kherlakian, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, S. Kundu, M. J. Lang, M. Lundy, G. Maier, C. McSorley, P. Moriarty, R. Mukherjee, W. Ning, S. O’Brien, M. Ohishi, R. A. Ong, A. Pandey, C. Poggemann, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, P. T. Reynolds, D. Ribeiro, L. Rizk, E. Roache, I. Sadeh, L. Saha, H. Salzmann, M. Santander, G. H. Sembroski, R. Shang, M. Splettstoesser, D. Tak, A. K. Talluri, I. Thoreson, J. V. Tucci, J. Valverde, D. A. Williams, S. L. Wong, T. Yoshikoshi and The VERITAS Collaboration","doi":"10.3847/1538-4357/ae5226","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5226","url":null,"abstract":"Significant gamma-ray emission between 1 TeV and 20 TeV from a point source, 1LHAASO J1219+2915, consistent with the location of the LINER/LLAGN galaxy NGC 4278 was recently reported by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These data were later split into active and quasi-quiet states, with most of the LHAASO significance coming from the active state (MJD 59449-59589). Subsequent analysis of Fermi-LAT and Swift-XRT observations have been used to explore the double-peaked broadband emission. Models of the spectral energy distribution (SED) are currently unconstrained due to the lack of contemporaneous multiwavelength data at either peak. Here, we report serendipitous observations of NGC 4278 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS), made possible by the contemporaneous observations of the nearby blazars 1ES 1218+304, 1ES 1215+303, and W Comae, each of which are located within 2° of NGC 4278. VERITAS did not detect any gamma-ray emission, and a flux upper limit was calculated. The flux upper limits constrain the photon spectrum of the quasi-quiet period, and together with Fermi-LAT, indicate a peak in the SED between 100 GeV and 2 TeV. We present an interpretation of the broadband SED that is based on acceleration of protons in the corona of the active galactic nuclei, followed by p–γ interactions and optically thin γ-ray emission. Within this framework, the implied neutrino signal is slightly below the current sensitivity of IceCube.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147709091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae563d
Zachary Burr, Mario Damiano, Vincent Kofman, Renyu Hu and Geronimo L. Villanueva
The detection and characterization of potentially habitable exoplanets is one of the chief goals of astrophysics for the coming decades. Imaging in reflected light is well suited for characterizing Earth-like planets, because much can be learned about these planets in this wavelength range (i.e., ∼0.3–2 μm). Several studies have been conducted to determine the abilities and limitations of reflectance spectroscopy, but most previous studies assumed a homogeneous atmospheric and surface composition. Here we investigate how heterogeneities in the atmosphere and surface of an Earth-like planet impact retrieval results. We extend the ExoReLℜ retrieval framework to include a step function for retrieving wavelength-varying surface albedo. We then use it to retrieve on visible to near-infrared spectra of realistic 3D Earth models with different surface features in view and varying cloud types/distributions synthesized with the Planetary Spectrum Generator. Including the ability to fit for wavelength-dependent albedo mitigates degeneracies that arise when using 1D models to analyze 3D planets, and we recover an Earth-like planet in all cases. We detect surface albedo steps at ∼0.7 and ∼1.1 μm despite clouds, both when significant lands are in view and when the spectra are averaged to account for a longer integration time. Our findings support the application of the vegetation red edge as a biosignature in the context of the Habitable Worlds Observatory. This study highlights the importance of considering a range of—particularly wavelength-dependent—surface albedos when using reflectance spectroscopy to characterize Earth-like exoplanets.
{"title":"Retrieving the Red Edge on Earth-like Planets with Heterogeneous Clouds and Surfaces","authors":"Zachary Burr, Mario Damiano, Vincent Kofman, Renyu Hu and Geronimo L. Villanueva","doi":"10.3847/1538-4357/ae563d","DOIUrl":"https://doi.org/10.3847/1538-4357/ae563d","url":null,"abstract":"The detection and characterization of potentially habitable exoplanets is one of the chief goals of astrophysics for the coming decades. Imaging in reflected light is well suited for characterizing Earth-like planets, because much can be learned about these planets in this wavelength range (i.e., ∼0.3–2 μm). Several studies have been conducted to determine the abilities and limitations of reflectance spectroscopy, but most previous studies assumed a homogeneous atmospheric and surface composition. Here we investigate how heterogeneities in the atmosphere and surface of an Earth-like planet impact retrieval results. We extend the ExoReLℜ retrieval framework to include a step function for retrieving wavelength-varying surface albedo. We then use it to retrieve on visible to near-infrared spectra of realistic 3D Earth models with different surface features in view and varying cloud types/distributions synthesized with the Planetary Spectrum Generator. Including the ability to fit for wavelength-dependent albedo mitigates degeneracies that arise when using 1D models to analyze 3D planets, and we recover an Earth-like planet in all cases. We detect surface albedo steps at ∼0.7 and ∼1.1 μm despite clouds, both when significant lands are in view and when the spectra are averaged to account for a longer integration time. Our findings support the application of the vegetation red edge as a biosignature in the context of the Habitable Worlds Observatory. This study highlights the importance of considering a range of—particularly wavelength-dependent—surface albedos when using reflectance spectroscopy to characterize Earth-like exoplanets.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5815
Giovani H. Vicentin, Grzegorz Kowal, Elisabete M. de Gouveia Dal Pino and Alex Lazarian
We investigate the development of tearing-mode instability using the highest-resolution 2D magnetohydrodynamic simulations of reconnecting current sheets performed on a uniform grid, for Lundquist numbers of 103 ≤ S ≤ 5 × 105, reaching up to 65,5362 grid cells. We demonstrate a Sweet–Parker scaling of the reconnection rate Vrec ∼ S−1/2 up to Lundquist numbers S ∼ 104. For larger values of Lundquist number, between 2 × 104 ≤ S ≤ 2 × 105, plasmoid formation sets in, leading to a slight enhancement of the reconnection rate, Vrec ∼ S−1/3, consistent with the prediction from linear-tearing-mode-induced reconnection, indicating that reconnection remains resistivity-dependent and therefore slow. In this range of S-values, the plasmoids do not undergo a merger cascade, as they are rapidly advected out of the reconnection layer. Only for S > 2 × 105, we observe the nonlinear development of the tearing-mode instability, with plasmoid coalescence and a saturation of the reconnection rate at Vrec/VA ∼ 0.01. At such high S, however, the corresponding Reynolds number is large, reaching Re > 2000 even on scales comparable to the current-sheet thickness. We therefore conclude that, in astrophysical systems, it is essential to account for the dominant influence of turbulence and 3D effects in the reconnection process.
{"title":"Do Plasmoids Induce Fast Magnetic Reconnection in Well-resolved Current Sheets in 2D Magnetohydrodynamic Simulations?","authors":"Giovani H. Vicentin, Grzegorz Kowal, Elisabete M. de Gouveia Dal Pino and Alex Lazarian","doi":"10.3847/1538-4357/ae5815","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5815","url":null,"abstract":"We investigate the development of tearing-mode instability using the highest-resolution 2D magnetohydrodynamic simulations of reconnecting current sheets performed on a uniform grid, for Lundquist numbers of 103 ≤ S ≤ 5 × 105, reaching up to 65,5362 grid cells. We demonstrate a Sweet–Parker scaling of the reconnection rate Vrec ∼ S−1/2 up to Lundquist numbers S ∼ 104. For larger values of Lundquist number, between 2 × 104 ≤ S ≤ 2 × 105, plasmoid formation sets in, leading to a slight enhancement of the reconnection rate, Vrec ∼ S−1/3, consistent with the prediction from linear-tearing-mode-induced reconnection, indicating that reconnection remains resistivity-dependent and therefore slow. In this range of S-values, the plasmoids do not undergo a merger cascade, as they are rapidly advected out of the reconnection layer. Only for S > 2 × 105, we observe the nonlinear development of the tearing-mode instability, with plasmoid coalescence and a saturation of the reconnection rate at Vrec/VA ∼ 0.01. At such high S, however, the corresponding Reynolds number is large, reaching Re > 2000 even on scales comparable to the current-sheet thickness. We therefore conclude that, in astrophysical systems, it is essential to account for the dominant influence of turbulence and 3D effects in the reconnection process.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5934
A. Berklas and J. C. Pober
Detection and analysis of the cosmic 21 cm signal of neutral hydrogen has long been considered the most promising route towards exploration of the Epoch of Reionization (EoR). 21CMMC, a Markov Chain Monte Carlo sampler of the seminumerical simulation code 21cmFAST, has already been used in conjunction with published upper limits on the 21 cm signal from the Murchison Widefield Array, the Low Frequency Array, and the Hydrogen Epoch of Reionization Array to constrain the astrophysics of the EoR. Here, we investigate the extent to which analysis of the EoR performed using 21CMMC is dependent on the underlying seminumerical model. We used 21cmFAST to simulate two datasets of 21 cm light-cones that differ only in the algorithm used to identify ionized regions (the so-called “bubble-finding” algorithm). We then tested 21CMMC’s ability to return key astrophysical parameters when using the different bubble-finding algorithms. We find that the performance of 21CMMC depends sensitively on the agreement between the astrophysical model of our mock data and the model used for sampling. This result has important implications for the analysis of the 21 cm signal performed using 21CMMC and further motivates investigation into model-independent analysis techniques for 21 cm EoR data.
{"title":"Exploring the Model Dependence of MCMC-based 21 cm Power Spectrum Parameter Constraints","authors":"A. Berklas and J. C. Pober","doi":"10.3847/1538-4357/ae5934","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5934","url":null,"abstract":"Detection and analysis of the cosmic 21 cm signal of neutral hydrogen has long been considered the most promising route towards exploration of the Epoch of Reionization (EoR). 21CMMC, a Markov Chain Monte Carlo sampler of the seminumerical simulation code 21cmFAST, has already been used in conjunction with published upper limits on the 21 cm signal from the Murchison Widefield Array, the Low Frequency Array, and the Hydrogen Epoch of Reionization Array to constrain the astrophysics of the EoR. Here, we investigate the extent to which analysis of the EoR performed using 21CMMC is dependent on the underlying seminumerical model. We used 21cmFAST to simulate two datasets of 21 cm light-cones that differ only in the algorithm used to identify ionized regions (the so-called “bubble-finding” algorithm). We then tested 21CMMC’s ability to return key astrophysical parameters when using the different bubble-finding algorithms. We find that the performance of 21CMMC depends sensitively on the agreement between the astrophysical model of our mock data and the model used for sampling. This result has important implications for the analysis of the 21 cm signal performed using 21CMMC and further motivates investigation into model-independent analysis techniques for 21 cm EoR data.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5236
Wenbo Wu, Yuqin Chen, Jianhui Lian, Martín López-Corredoira, Chengdong Li, Xianhao Ye, C. Allende Prieto, Xiang-Xiang Xue, Gang Zhao, Jingkun Zhao, David S. Aguado, Jonay I. González Hernández and Rafael Rebolo
This study explores the density profile of the stellar disk, radially and azimuthally, based on approximately 8.4 million red clump stars selected from Gaia Bp/Rp spectra. After correcting for selection effects and distance uncertainties, we fit the vertical stellar density profile of the Galactic disk with a two-component model consisting of geometrically thin and thick disks. Our derived density profile shows several breaks radially: (1) a steep exponent inside R ∼ 3 kpc; (2) a nearly flat plateau from R ∼ 3 to ∼7 kpc; (3) an exponential decline beyond the solar radius to around 13 kpc; (4) a sharper exponential drop-off beyond R ∼ 13 kpc. The parameters of these four main components depend on ϕ to some extent. The variation of the termination radius of the first component suggests an interaction with the bar/bulge. Besides the typical flaring at R > 6.4 kpc, we find that the thin disk also exhibits a similar and smooth thickening/flaring feature toward the Galactic center at R < 6.4 kpc. The observed inner flaring may indicate heating effects introduced by the Galactic bar, since R = 6.4 kpc lies close to the corotation radius where the bar’s dynamical influence becomes significant. Additionally, we identify a localized density bump in the region 5 < R < 7 kpc and −30° < ϕ < 15°, where a corresponding metallicity bump is also visible near the Galactic plane. This density/metallicity bump may be related to the recently reported bimodal distribution of the guiding radius of super metal-rich stars in the solar vicinity through radial migration.
{"title":"Mapping the Milky Way with Gaia Bp/Rp Spectra. IV. The Broken and Asymmetric Density Profile of the Stellar Disk Traced by a Large Sample of Red Clumps","authors":"Wenbo Wu, Yuqin Chen, Jianhui Lian, Martín López-Corredoira, Chengdong Li, Xianhao Ye, C. Allende Prieto, Xiang-Xiang Xue, Gang Zhao, Jingkun Zhao, David S. Aguado, Jonay I. González Hernández and Rafael Rebolo","doi":"10.3847/1538-4357/ae5236","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5236","url":null,"abstract":"This study explores the density profile of the stellar disk, radially and azimuthally, based on approximately 8.4 million red clump stars selected from Gaia Bp/Rp spectra. After correcting for selection effects and distance uncertainties, we fit the vertical stellar density profile of the Galactic disk with a two-component model consisting of geometrically thin and thick disks. Our derived density profile shows several breaks radially: (1) a steep exponent inside R ∼ 3 kpc; (2) a nearly flat plateau from R ∼ 3 to ∼7 kpc; (3) an exponential decline beyond the solar radius to around 13 kpc; (4) a sharper exponential drop-off beyond R ∼ 13 kpc. The parameters of these four main components depend on ϕ to some extent. The variation of the termination radius of the first component suggests an interaction with the bar/bulge. Besides the typical flaring at R > 6.4 kpc, we find that the thin disk also exhibits a similar and smooth thickening/flaring feature toward the Galactic center at R < 6.4 kpc. The observed inner flaring may indicate heating effects introduced by the Galactic bar, since R = 6.4 kpc lies close to the corotation radius where the bar’s dynamical influence becomes significant. Additionally, we identify a localized density bump in the region 5 < R < 7 kpc and −30° < ϕ < 15°, where a corresponding metallicity bump is also visible near the Galactic plane. This density/metallicity bump may be related to the recently reported bimodal distribution of the guiding radius of super metal-rich stars in the solar vicinity through radial migration.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae523e
Eunsuk Seo, Hyunmi Song, Lucia Guaita, Kyoung-Soo Lee, Eric Gawiser, Robin Ciardullo, Arjun Dey, Seok-Jun Chang, Nicole Firestone, Stephen Gwyn, Ho Seong Hwang, Sungryong Hong, Sang Hyeok Im, Woong-Seob Jeong, Jaehyun Lee, Seong-Kook Lee, Chanbom Park, Vandana Ramakrishnan, Marcin Sawicki, Yujin Yang and Ann Zabludoff
We investigated Lyman-continuum (LyC) emission from Lyman-alpha emitters (LAEs) at z = 4.5, identified in the One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey. Of the 7498 LAEs (4101 in COSMOS and 3397 in XMM-LSS), we excluded LAEs that are either likely low-z objects or contaminated by neighboring sources. Additional background modeling process with thorough quality assessments leaves a final sample of 851 galaxies. We then performed forced photometry on u/u*-band images from the CFHT large area u-band deep survey to measure their LyC fluxes. This represents the largest sample of z = 4.5 LAEs searched for such a purpose. Within this sample, we identified 12 “gold” and 39 “silver” LyC-emitting candidates, with LyC fluxes detected of >3σ and between 2σ and 3σ, respectively, in the range of 5.16–55.29 nJy. No LyC signal is detected in the weighted mean stack of the final sample (0.20 ± 0.37 nJy). Given the UVC magnitudes of LAEs in our sample, the expected LyC emission is likely below the detection limit even when stacking the full sample of ODIN LAEs. Nevertheless, having a large sample of LAEs remains valuable for identifying individual LyC leaker candidates. Among the gold and silver candidates, the LyC flux appears to correlate positively with UVC flux and negatively with Lyα equivalent width, although the correlations are weak. A larger sample of LyC leakers will allow a more robust confirmation of these trends and provide better insights into their physical origins.
{"title":"ODIN: Searching for LyC Emission from Lyα Emitters at z = 4.5 in the E-COSMOS and XMM-LSS Fields","authors":"Eunsuk Seo, Hyunmi Song, Lucia Guaita, Kyoung-Soo Lee, Eric Gawiser, Robin Ciardullo, Arjun Dey, Seok-Jun Chang, Nicole Firestone, Stephen Gwyn, Ho Seong Hwang, Sungryong Hong, Sang Hyeok Im, Woong-Seob Jeong, Jaehyun Lee, Seong-Kook Lee, Chanbom Park, Vandana Ramakrishnan, Marcin Sawicki, Yujin Yang and Ann Zabludoff","doi":"10.3847/1538-4357/ae523e","DOIUrl":"https://doi.org/10.3847/1538-4357/ae523e","url":null,"abstract":"We investigated Lyman-continuum (LyC) emission from Lyman-alpha emitters (LAEs) at z = 4.5, identified in the One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey. Of the 7498 LAEs (4101 in COSMOS and 3397 in XMM-LSS), we excluded LAEs that are either likely low-z objects or contaminated by neighboring sources. Additional background modeling process with thorough quality assessments leaves a final sample of 851 galaxies. We then performed forced photometry on u/u*-band images from the CFHT large area u-band deep survey to measure their LyC fluxes. This represents the largest sample of z = 4.5 LAEs searched for such a purpose. Within this sample, we identified 12 “gold” and 39 “silver” LyC-emitting candidates, with LyC fluxes detected of >3σ and between 2σ and 3σ, respectively, in the range of 5.16–55.29 nJy. No LyC signal is detected in the weighted mean stack of the final sample (0.20 ± 0.37 nJy). Given the UVC magnitudes of LAEs in our sample, the expected LyC emission is likely below the detection limit even when stacking the full sample of ODIN LAEs. Nevertheless, having a large sample of LAEs remains valuable for identifying individual LyC leaker candidates. Among the gold and silver candidates, the LyC flux appears to correlate positively with UVC flux and negatively with Lyα equivalent width, although the correlations are weak. A larger sample of LyC leakers will allow a more robust confirmation of these trends and provide better insights into their physical origins.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5957
Yangyu Liu, Jinhua Shen, Xu Yang, Shuai Gu, Jianping Li and Haisheng Ji
Using high-resolution photospheric and chromospheric observations taken by the Goode Solar Telescope, we studied two groups of bidirectional plasma jets occurring in active region NOAA 13110. Supplementary observations are also provided by Solar Dynamics Observatory’s Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager. From the photospheric observations and magnetograms, the two successive bidirectional plasma jets were initially located in the vicinity of the polarity inversion lines and at the intersection of the umbra and penumbra of the sunspot, followed by magnetic flux emergence and cancellation. As the cool filamentary threads are continuously emerging from the lower chromosphere and interact with overlying horizontal magnetic loops, it leads to the bidirectional jets, erupting outflow plasmoids, and heating coronal magnetic loops. We find that the bidirectional jets extended from the central excitation location in opposite directions, at the speed of about dozens of km s−1. For the first jet, the initial brightening first appears in 304 Å, about 30 s earlier than the Hα observations, indicating that magnetic reconnection takes place in the transition region. Meanwhile, the initial reconnection for the second jet occurs simultaneously in Hα and 304 Å, showing the recurrent eruptions. These observations confirm that the bidirectional plasma jets can be generated by magnetic reconnection between the rising filamentary threads or material and the overlying horizontal magnetic loops. Our results provide new insights into the generation of the bidirectional plasma jets and reconnection-based coronal heating.
{"title":"Bidirectional Plasma Jets Driven by Magnetic Reconnection: Observations by GST and SDO","authors":"Yangyu Liu, Jinhua Shen, Xu Yang, Shuai Gu, Jianping Li and Haisheng Ji","doi":"10.3847/1538-4357/ae5957","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5957","url":null,"abstract":"Using high-resolution photospheric and chromospheric observations taken by the Goode Solar Telescope, we studied two groups of bidirectional plasma jets occurring in active region NOAA 13110. Supplementary observations are also provided by Solar Dynamics Observatory’s Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager. From the photospheric observations and magnetograms, the two successive bidirectional plasma jets were initially located in the vicinity of the polarity inversion lines and at the intersection of the umbra and penumbra of the sunspot, followed by magnetic flux emergence and cancellation. As the cool filamentary threads are continuously emerging from the lower chromosphere and interact with overlying horizontal magnetic loops, it leads to the bidirectional jets, erupting outflow plasmoids, and heating coronal magnetic loops. We find that the bidirectional jets extended from the central excitation location in opposite directions, at the speed of about dozens of km s−1. For the first jet, the initial brightening first appears in 304 Å, about 30 s earlier than the Hα observations, indicating that magnetic reconnection takes place in the transition region. Meanwhile, the initial reconnection for the second jet occurs simultaneously in Hα and 304 Å, showing the recurrent eruptions. These observations confirm that the bidirectional plasma jets can be generated by magnetic reconnection between the rising filamentary threads or material and the overlying horizontal magnetic loops. Our results provide new insights into the generation of the bidirectional plasma jets and reconnection-based coronal heating.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-16DOI: 10.3847/1538-4357/ae5223
Z. Gelles, A. Chael and E. Quataert
We analyze the polarization of optically thin, stationary, axisymmetric black hole jets at scales of order the light cylinder radius. Our work generalizes the face-on results of Z. Gelles et al. to arbitrary viewing inclination. Due to a combination of geometry and relativistic aberration, the polarization of the jet is not left–right symmetric, and the degree of asymmetry can shed light on both the viewing angle and the plasma bulk Lorentz factor. We show that there is always a radius in the jet at which the polarization angle transitions from azimuthal to radial; this radius is different along the spine and limb of the jet. We propose metrics that can be used to constrain the black hole spin, inclination angle, and plasma Lorentz factor from these polarimetric signatures, and we discuss the impact of limb brightening on these measurements. We anticipate that these polarimetric signatures can be studied with current or forthcoming data of M87, NGC 315, NGC 4261, Centaurus A, Cygnus A, and other systems. Observations of the polarization of the base of the counterjet in higher-inclination sources would provide a particularly promising probe of black hole spin.
{"title":"Signatures of Black Hole Spin and Plasma Acceleration in Jet Polarimetry. II. Off-axis Jets","authors":"Z. Gelles, A. Chael and E. Quataert","doi":"10.3847/1538-4357/ae5223","DOIUrl":"https://doi.org/10.3847/1538-4357/ae5223","url":null,"abstract":"We analyze the polarization of optically thin, stationary, axisymmetric black hole jets at scales of order the light cylinder radius. Our work generalizes the face-on results of Z. Gelles et al. to arbitrary viewing inclination. Due to a combination of geometry and relativistic aberration, the polarization of the jet is not left–right symmetric, and the degree of asymmetry can shed light on both the viewing angle and the plasma bulk Lorentz factor. We show that there is always a radius in the jet at which the polarization angle transitions from azimuthal to radial; this radius is different along the spine and limb of the jet. We propose metrics that can be used to constrain the black hole spin, inclination angle, and plasma Lorentz factor from these polarimetric signatures, and we discuss the impact of limb brightening on these measurements. We anticipate that these polarimetric signatures can be studied with current or forthcoming data of M87, NGC 315, NGC 4261, Centaurus A, Cygnus A, and other systems. Observations of the polarization of the base of the counterjet in higher-inclination sources would provide a particularly promising probe of black hole spin.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147702349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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