Pub Date : 2025-01-10DOI: 10.3847/2041-8213/ad9dde
Antonio Circiello, Alex McDaniel, Alex Drlica-Wagner, Christopher Karwin, Marco Ajello, Mattia Di Mauro and Miguel Á. Sánchez-Conde
Recent results from numerical simulations and models of galaxy formation suggest that recently discovered ultrafaint compact stellar systems (UFCSs) in the halo of the Milky Way (MW) may be some of the smallest and faintest galaxies. If this is the case, these systems would be attractive targets for indirect searches of weakly interacting massive particle dark matter (DM) annihilation due to their relative proximity and high expected DM content. In this study, we analyze 14.3 yr of γ-ray data collected by the Fermi-Large Area Telescope coincident with 26 UFCSs. No significant excess γ-ray emission is detected, and we present γ-ray flux upper limits for these systems. Assuming that the UFCSs are DM-dominated galaxies consistent with being among the faintest and least massive MW dwarf spheroidal (dSph) satellite galaxies, we derive the projected sensitivity for a DM annihilation signal. We find that observations of UFCSs have the potential to yield some of the most powerful constraints on DM annihilation, with sensitivity comparable to observations of known dSphs and the Galactic center. This result emphasizes the importance of precise kinematic studies of UFCSs to empirically determine their DM content.
{"title":"Evaluating the Potential to Constrain Dark Matter Annihilation with Fermi-LAT Observations of Ultrafaint Compact Stellar Systems","authors":"Antonio Circiello, Alex McDaniel, Alex Drlica-Wagner, Christopher Karwin, Marco Ajello, Mattia Di Mauro and Miguel Á. Sánchez-Conde","doi":"10.3847/2041-8213/ad9dde","DOIUrl":"https://doi.org/10.3847/2041-8213/ad9dde","url":null,"abstract":"Recent results from numerical simulations and models of galaxy formation suggest that recently discovered ultrafaint compact stellar systems (UFCSs) in the halo of the Milky Way (MW) may be some of the smallest and faintest galaxies. If this is the case, these systems would be attractive targets for indirect searches of weakly interacting massive particle dark matter (DM) annihilation due to their relative proximity and high expected DM content. In this study, we analyze 14.3 yr of γ-ray data collected by the Fermi-Large Area Telescope coincident with 26 UFCSs. No significant excess γ-ray emission is detected, and we present γ-ray flux upper limits for these systems. Assuming that the UFCSs are DM-dominated galaxies consistent with being among the faintest and least massive MW dwarf spheroidal (dSph) satellite galaxies, we derive the projected sensitivity for a DM annihilation signal. We find that observations of UFCSs have the potential to yield some of the most powerful constraints on DM annihilation, with sensitivity comparable to observations of known dSphs and the Galactic center. This result emphasizes the importance of precise kinematic studies of UFCSs to empirically determine their DM content.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"47 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968258","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 : 2025-01-10DOI: 10.3847/2041-8213/ada290
Ruslan Nakibov, Varvara Karteyeva, Igor Petrashkevich, Maksim Ozhiganov, Mikhail Medvedev and Anton Vasyunin
We present a new description of the 7.7 μm region towards the high-mass star-forming region IRAS 23385+6053 taken from the open James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer data. This area is commonly attributed to the ν4 deformation mode of methane ice. For the first time, gaseous and solid methane were analyzed simultaneously in IRAS 23385+6053. The band at 7.58–7.8 μm (1320–1280 cm−1) is interpreted as a wide solid absorption methane feature overlapped by the sharp features of the methane emission. We report the detection of gaseous methane and estimate its emitting area radius R, temperature T, and column density N as R = 2940 au, K, and cm−2, correspondingly. The ice content was analyzed with the laboratory spectra data set of methane in different molecular environments obtained on the Ice Spectroscopy Experimental Aggregate. We were able to describe the wide feature of solid methane with the following laboratory spectra: CH4 : CO2 = 1 : 5 (at K) and CH4 : H2O = 1 : 10 (at K) deposited at 6.7 K and warmed up at a rate of 0.5 K per minute. The derived column densities are (CO2) = cm−2 and (H2O) = cm−2. According to the best fit, solid methane is mostly surrounded by CO2 rather than H2O. The residual analysis reveals the unassigned region at 1283–1297 cm−1 (7.71–7.79 μm), which is tentatively assigned to nitrous oxide (N2O) in various environments.
{"title":"Solid and Gaseous Methane in IRAS 23385+6053 as Seen with Open JWST Data","authors":"Ruslan Nakibov, Varvara Karteyeva, Igor Petrashkevich, Maksim Ozhiganov, Mikhail Medvedev and Anton Vasyunin","doi":"10.3847/2041-8213/ada290","DOIUrl":"https://doi.org/10.3847/2041-8213/ada290","url":null,"abstract":"We present a new description of the 7.7 μm region towards the high-mass star-forming region IRAS 23385+6053 taken from the open James Webb Space Telescope Mid-Infrared Instrument Medium Resolution Spectrometer data. This area is commonly attributed to the ν4 deformation mode of methane ice. For the first time, gaseous and solid methane were analyzed simultaneously in IRAS 23385+6053. The band at 7.58–7.8 μm (1320–1280 cm−1) is interpreted as a wide solid absorption methane feature overlapped by the sharp features of the methane emission. We report the detection of gaseous methane and estimate its emitting area radius R, temperature T, and column density N as R = 2940 au, K, and cm−2, correspondingly. The ice content was analyzed with the laboratory spectra data set of methane in different molecular environments obtained on the Ice Spectroscopy Experimental Aggregate. We were able to describe the wide feature of solid methane with the following laboratory spectra: CH4 : CO2 = 1 : 5 (at K) and CH4 : H2O = 1 : 10 (at K) deposited at 6.7 K and warmed up at a rate of 0.5 K per minute. The derived column densities are (CO2) = cm−2 and (H2O) = cm−2. According to the best fit, solid methane is mostly surrounded by CO2 rather than H2O. The residual analysis reveals the unassigned region at 1283–1297 cm−1 (7.71–7.79 μm), which is tentatively assigned to nitrous oxide (N2O) in various environments.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939839","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 : 2025-01-10DOI: 10.3847/2041-8213/ada3d9
Xiao-Bin Chen, Kai Wang, Yi-Yun Huang, Hai-Ming Zhang, Shao-Qiang Xi, Ruo-Yu Liu and Xiang-Yu Wang
The supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster medium within the viral radius and external accretion shocks forming in the outer cold region well outside of the virial radius. Cosmic-ray (CR) electrons and/or protons accelerated by these shocks are expected to produce gamma rays through inverse-Compton scattering (ICS) or inelastic pp collisions, respectively. Recent studies have found a spatially extended GeV source within the virial radius, consistent with the internal shock origin. Here, we report the detection of a new GeV source at a distance of about 2 8 from the center of the Coma cluster through the analysis of 16.2 yr of Fermi-LAT data. The hard spectrum of the source, in agreement with the ICS origin, and its location in a large-scale filament of galaxies points to the external accretion shock origin. The gamma-ray (0.1−103 GeV) luminosity of the source, 1.4 × 1042 erg s−1, suggests that a fraction ~10−3 of the kinetic energy flux through the shock surface is transferred to relativistic CR electrons.
{"title":"Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock?","authors":"Xiao-Bin Chen, Kai Wang, Yi-Yun Huang, Hai-Ming Zhang, Shao-Qiang Xi, Ruo-Yu Liu and Xiang-Yu Wang","doi":"10.3847/2041-8213/ada3d9","DOIUrl":"https://doi.org/10.3847/2041-8213/ada3d9","url":null,"abstract":"The supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster medium within the viral radius and external accretion shocks forming in the outer cold region well outside of the virial radius. Cosmic-ray (CR) electrons and/or protons accelerated by these shocks are expected to produce gamma rays through inverse-Compton scattering (ICS) or inelastic pp collisions, respectively. Recent studies have found a spatially extended GeV source within the virial radius, consistent with the internal shock origin. Here, we report the detection of a new GeV source at a distance of about 2 8 from the center of the Coma cluster through the analysis of 16.2 yr of Fermi-LAT data. The hard spectrum of the source, in agreement with the ICS origin, and its location in a large-scale filament of galaxies points to the external accretion shock origin. The gamma-ray (0.1−103 GeV) luminosity of the source, 1.4 × 1042 erg s−1, suggests that a fraction ~10−3 of the kinetic energy flux through the shock surface is transferred to relativistic CR electrons.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939844","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 : 2025-01-10DOI: 10.3847/2041-8213/ad86c3
Zifan Lin, Saverio Cambioni and Sara Seager
Some exoplanets have much higher densities than expected from stellar abundances of planet-forming elements. There are two theories—metal-rich formation hypothesis and naked core hypothesis—that explain how formation and evolution can alter the compositions and structures of rocky planets to diverge from their primordial building blocks. Here we revisit the naked core hypothesis, which states that high-density planets are remnant cores of giant planets that remain in a fossil-compressed state, even after envelope loss. Using a planetary interior model and assuming energy-limited atmospheric escape, we show that a large fraction, if not all, of the iron–silicate core of a giant planet is molten during the planet's early evolution. Upon envelope loss, the molten part of the planets can rapidly rebound owing to low viscosity, resulting in a decrease in radius by at most 0.06%, if they had hydrogen/helium envelopes, or by at most 7%, if they had H2O envelopes, compared to self-compressed counterparts with the same core mass fraction. Based on our findings, we reject the hypothesis that all high-density exoplanets are naked cores with Kolmogorov–Smirnov p-value ≪0.05 for both envelope compositions. We find that some high-density exoplanets can still possibly be naked cores, but the probabilities are lower than ∼1/2 and ∼1/3 for the ice giant and gas giant scenario, respectively, in 95% of the cases. We conclude that most high-density exoplanets are unlikely to be remnant giant planet cores.
{"title":"Most High-density Exoplanets Are Unlikely to Be Remnant Giant Planet's Cores","authors":"Zifan Lin, Saverio Cambioni and Sara Seager","doi":"10.3847/2041-8213/ad86c3","DOIUrl":"https://doi.org/10.3847/2041-8213/ad86c3","url":null,"abstract":"Some exoplanets have much higher densities than expected from stellar abundances of planet-forming elements. There are two theories—metal-rich formation hypothesis and naked core hypothesis—that explain how formation and evolution can alter the compositions and structures of rocky planets to diverge from their primordial building blocks. Here we revisit the naked core hypothesis, which states that high-density planets are remnant cores of giant planets that remain in a fossil-compressed state, even after envelope loss. Using a planetary interior model and assuming energy-limited atmospheric escape, we show that a large fraction, if not all, of the iron–silicate core of a giant planet is molten during the planet's early evolution. Upon envelope loss, the molten part of the planets can rapidly rebound owing to low viscosity, resulting in a decrease in radius by at most 0.06%, if they had hydrogen/helium envelopes, or by at most 7%, if they had H2O envelopes, compared to self-compressed counterparts with the same core mass fraction. Based on our findings, we reject the hypothesis that all high-density exoplanets are naked cores with Kolmogorov–Smirnov p-value ≪0.05 for both envelope compositions. We find that some high-density exoplanets can still possibly be naked cores, but the probabilities are lower than ∼1/2 and ∼1/3 for the ice giant and gas giant scenario, respectively, in 95% of the cases. We conclude that most high-density exoplanets are unlikely to be remnant giant planet cores.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939836","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 : 2025-01-10DOI: 10.3847/2041-8213/ada158
Abigail Moran, Lorenzo Sironi, Aviad Levis, Bart Ripperda, Elias R. Most and Sebastiaan Selvi
A variety of high-energy astrophysical phenomena are powered by the release—via magnetic reconnection—of the energy stored in oppositely directed fields. Single-fluid resistive magnetohydrodynamic (MHD) simulations with uniform resistivity yield dissipation rates that are much lower (by nearly 1 order of magnitude) than equivalent kinetic calculations. Reconnection-driven phenomena could be accordingly modeled in resistive MHD employing a nonuniform, “effective” resistivity informed by kinetic calculations. In this work, we analyze a suite of fully kinetic particle-in-cell (PIC) simulations of relativistic pair-plasma reconnection—where the magnetic energy is greater than the rest mass energy—for different strengths of the guide field orthogonal to the alternating component. We extract an empirical prescription for the effective resistivity, , where B0 is the reconnecting magnetic field strength, J is the current density, nt is the lab-frame total number density, e is the elementary charge, and c is the speed of light. The guide field dependence is encoded in α and p, which we fit to PIC data. This resistivity formulation—which relies only on single-fluid MHD quantities—successfully reproduces the spatial structure and strength of nonideal electric fields and thus provides a promising strategy for enhancing the reconnection rate in resistive MHD simulations.
{"title":"Effective Resistivity in Relativistic Reconnection: A Prescription Based on Fully Kinetic Simulations","authors":"Abigail Moran, Lorenzo Sironi, Aviad Levis, Bart Ripperda, Elias R. Most and Sebastiaan Selvi","doi":"10.3847/2041-8213/ada158","DOIUrl":"https://doi.org/10.3847/2041-8213/ada158","url":null,"abstract":"A variety of high-energy astrophysical phenomena are powered by the release—via magnetic reconnection—of the energy stored in oppositely directed fields. Single-fluid resistive magnetohydrodynamic (MHD) simulations with uniform resistivity yield dissipation rates that are much lower (by nearly 1 order of magnitude) than equivalent kinetic calculations. Reconnection-driven phenomena could be accordingly modeled in resistive MHD employing a nonuniform, “effective” resistivity informed by kinetic calculations. In this work, we analyze a suite of fully kinetic particle-in-cell (PIC) simulations of relativistic pair-plasma reconnection—where the magnetic energy is greater than the rest mass energy—for different strengths of the guide field orthogonal to the alternating component. We extract an empirical prescription for the effective resistivity, , where B0 is the reconnecting magnetic field strength, J is the current density, nt is the lab-frame total number density, e is the elementary charge, and c is the speed of light. The guide field dependence is encoded in α and p, which we fit to PIC data. This resistivity formulation—which relies only on single-fluid MHD quantities—successfully reproduces the spatial structure and strength of nonideal electric fields and thus provides a promising strategy for enhancing the reconnection rate in resistive MHD simulations.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"82 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939837","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 : 2025-01-09DOI: 10.3847/2041-8213/ada1cc
Patrick Chi-Kit Cheong, 志杰 張, Tetyana Pitik, Luís Felipe Longo Micchi and David Radice
We present the first seconds-long 2D general relativistic neutrino magnetohydrodynamic simulations of accretion-induced collapse (AIC) in rapidly rotating, strongly magnetized white dwarfs (WDs), which might originate as remnants of double-WD mergers. This study examines extreme combinations of magnetic fields and rotation rates, motivated both by the need to address the limitations of 2D axisymmetric simulations and to explore the physics of AIC under rare conditions that, while yet to be observationally confirmed, may be consistent with current theoretical models and account for unusual events. Under these assumptions, our results demonstrate that, if realizable, such systems can generate relativistic jets and neutron-rich outflows with properties consistent with long gamma-ray bursts (LGRBs) accompanied by kilonovae, such as GRB 211211A and GRB 230307A. These findings highlight the potential role of AIC in heavy r-process element production and offer a framework for understanding rare LGRBs associated with kilonova emission. Longer-duration 3D simulations are needed to fully capture magnetic field amplification, resolve instabilities, and determine the fate of the energy retained by the magnetar at the end of the simulations.
{"title":"Gamma-Ray Bursts and Kilonovae from the Accretion-induced Collapse of White Dwarfs","authors":"Patrick Chi-Kit Cheong, 志杰 張, Tetyana Pitik, Luís Felipe Longo Micchi and David Radice","doi":"10.3847/2041-8213/ada1cc","DOIUrl":"https://doi.org/10.3847/2041-8213/ada1cc","url":null,"abstract":"We present the first seconds-long 2D general relativistic neutrino magnetohydrodynamic simulations of accretion-induced collapse (AIC) in rapidly rotating, strongly magnetized white dwarfs (WDs), which might originate as remnants of double-WD mergers. This study examines extreme combinations of magnetic fields and rotation rates, motivated both by the need to address the limitations of 2D axisymmetric simulations and to explore the physics of AIC under rare conditions that, while yet to be observationally confirmed, may be consistent with current theoretical models and account for unusual events. Under these assumptions, our results demonstrate that, if realizable, such systems can generate relativistic jets and neutron-rich outflows with properties consistent with long gamma-ray bursts (LGRBs) accompanied by kilonovae, such as GRB 211211A and GRB 230307A. These findings highlight the potential role of AIC in heavy r-process element production and offer a framework for understanding rare LGRBs associated with kilonova emission. Longer-duration 3D simulations are needed to fully capture magnetic field amplification, resolve instabilities, and determine the fate of the energy retained by the magnetar at the end of the simulations.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142937623","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 : 2025-01-09DOI: 10.3847/2041-8213/ada0bc
Mark Hammond, Claire Marie Guimond, Tim Lichtenberg, Harrison Nicholls, Chloe Fisher, Rafael Luque, Tobias G. Meier, Jake Taylor, Quentin Changeat, Lisa Dang, Hamish C. F. C. Hay, Oliver Herbort and Johanna Teske
The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.
{"title":"Reliable Detections of Atmospheres on Rocky Exoplanets with Photometric JWST Phase Curves","authors":"Mark Hammond, Claire Marie Guimond, Tim Lichtenberg, Harrison Nicholls, Chloe Fisher, Rafael Luque, Tobias G. Meier, Jake Taylor, Quentin Changeat, Lisa Dang, Hamish C. F. C. Hay, Oliver Herbort and Johanna Teske","doi":"10.3847/2041-8213/ada0bc","DOIUrl":"https://doi.org/10.3847/2041-8213/ada0bc","url":null,"abstract":"The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936844","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 : 2025-01-09DOI: 10.3847/2041-8213/ada150
Mengting Ju, Xin Wang, Tucker Jones, Ivana Barišić, Themiya Nanayakkara, Kevin Bundy, Claude-André Faucher-Giguère, Shuai Feng, Karl Glazebrook, Alaina Henry, Matthew A. Malkan, Danail Obreschkow, Namrata Roy, Ryan L. Sanders, Xunda Sun, Tommaso Treu and Qianqiao Zhou
The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from the MSA-3D survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST’s diffraction limit and a high spectral resolution of R ≃ 2700. The metallicity gradients measured in our galaxy sample range from −0.03 to 0.02 dex kpc−1. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at z ∼ 1 with small intrinsic scatter of 0.02 dex kpc−1. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more “disky.” This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution.
{"title":"MSA-3D: Metallicity Gradients in Galaxies at z ∼ 1 with JWST/NIRSpec Slit-stepping Spectroscopy","authors":"Mengting Ju, Xin Wang, Tucker Jones, Ivana Barišić, Themiya Nanayakkara, Kevin Bundy, Claude-André Faucher-Giguère, Shuai Feng, Karl Glazebrook, Alaina Henry, Matthew A. Malkan, Danail Obreschkow, Namrata Roy, Ryan L. Sanders, Xunda Sun, Tommaso Treu and Qianqiao Zhou","doi":"10.3847/2041-8213/ada150","DOIUrl":"https://doi.org/10.3847/2041-8213/ada150","url":null,"abstract":"The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from the MSA-3D survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST’s diffraction limit and a high spectral resolution of R ≃ 2700. The metallicity gradients measured in our galaxy sample range from −0.03 to 0.02 dex kpc−1. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at z ∼ 1 with small intrinsic scatter of 0.02 dex kpc−1. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more “disky.” This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939840","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 : 2025-01-09DOI: 10.3847/2041-8213/ada1d0
Bryce T. Bolin, Larry Denneau, Laura-May Abron, Robert Jedicke, Kristin Chiboucas, Carl Ingebretsen and Brian C. Lemaux
Minimoons are asteroids that become temporarily captured by the Earth–Moon system. We present the discovery of 2024 PT5, a minimoon discovered by the Asteroid Terrestrial-impact Last Alert System Sutherland telescope on 2024 August 7. The minimoon with heliocentric semimajor axis, a ~ 1.01 au, and perihelion, q ~ 0.99 au, became captured by the Earth–Moon system on 2024 September 29 and left on 2024 November 25 UTC. Visible g, r, i, and Z spectrophotometry was obtained using Gemini North/Gemini Multi-Object Spectrograph on 2024 September 27. The color indices are g − r = 0.58 ± 0.04, r − i = 0.29 ± 0.04, and i − Z = −0.27 ± 0.06, and the spectrum best matches lunar rock samples followed by S-complex asteroids. Assuming an albedo of 0.21 and using our measured absolute magnitude of 28.64 ± 0.04, 2024 PT5 has a diameter of 5.4 ± 1.2 m. We also detect variations in the lightcurve of 2024 PT5 with a 0.28 ± 0.07 mag amplitude and a double-peaked period of ~2600 ± 500 s. We improve the orbital solution of 2024 PT5 with our astrometry and estimate the effect of radiation pressure on its deriving an area-to-mass ratio of 7.02 ± 2.05 × 10−5 m2 kg−1, implying a density of ~3.9 ± 2.1 g cm−3, compatible with having a rocky composition. If we assume 2024 PT5 is from the near-Earth object (NEO) population, its most likely sources are resonances in the inner Main Belt when we compare its orbit with the NEO population model though this does not exclude a lunar origin.
{"title":"The Discovery and Characterization of Minimoon 2024 PT5","authors":"Bryce T. Bolin, Larry Denneau, Laura-May Abron, Robert Jedicke, Kristin Chiboucas, Carl Ingebretsen and Brian C. Lemaux","doi":"10.3847/2041-8213/ada1d0","DOIUrl":"https://doi.org/10.3847/2041-8213/ada1d0","url":null,"abstract":"Minimoons are asteroids that become temporarily captured by the Earth–Moon system. We present the discovery of 2024 PT5, a minimoon discovered by the Asteroid Terrestrial-impact Last Alert System Sutherland telescope on 2024 August 7. The minimoon with heliocentric semimajor axis, a ~ 1.01 au, and perihelion, q ~ 0.99 au, became captured by the Earth–Moon system on 2024 September 29 and left on 2024 November 25 UTC. Visible g, r, i, and Z spectrophotometry was obtained using Gemini North/Gemini Multi-Object Spectrograph on 2024 September 27. The color indices are g − r = 0.58 ± 0.04, r − i = 0.29 ± 0.04, and i − Z = −0.27 ± 0.06, and the spectrum best matches lunar rock samples followed by S-complex asteroids. Assuming an albedo of 0.21 and using our measured absolute magnitude of 28.64 ± 0.04, 2024 PT5 has a diameter of 5.4 ± 1.2 m. We also detect variations in the lightcurve of 2024 PT5 with a 0.28 ± 0.07 mag amplitude and a double-peaked period of ~2600 ± 500 s. We improve the orbital solution of 2024 PT5 with our astrometry and estimate the effect of radiation pressure on its deriving an area-to-mass ratio of 7.02 ± 2.05 × 10−5 m2 kg−1, implying a density of ~3.9 ± 2.1 g cm−3, compatible with having a rocky composition. If we assume 2024 PT5 is from the near-Earth object (NEO) population, its most likely sources are resonances in the inner Main Belt when we compare its orbit with the NEO population model though this does not exclude a lunar origin.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936846","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 : 2025-01-09DOI: 10.3847/2041-8213/ada427
Yi-Lun Du, Xiaojian Song and Xi Luo
We introduce a novel deep learning framework based on long short-term memory networks to predict galactic cosmic-ray spectra on a one-day-ahead basis by leveraging historical solar activity data, overcoming limitations inherent in traditional transport models. By flexibly incorporating multiple solar parameters, such as the heliospheric magnetic field, solar wind speed, and sunspot numbers, the model achieves accurate short-term and long-term predictions of cosmic-ray flux. The addition of historical cosmic-ray flux data significantly enhances prediction accuracy, allowing the model to capture complex dependencies between past and future flux variations. Additionally, the model reliably predicts full cosmic-ray spectra for different particle species, enhancing its utility for comprehensive space weather forecasting. Our approach offers a scalable, data-driven alternative to traditional physics-based methods, ensuring robust daily and long-term forecasts. This work opens avenues for advanced models that can integrate broader observational data, with significant implications for space weather monitoring and mission planning.
{"title":"Deep Learning the Forecast of Galactic Cosmic-Ray Spectra","authors":"Yi-Lun Du, Xiaojian Song and Xi Luo","doi":"10.3847/2041-8213/ada427","DOIUrl":"https://doi.org/10.3847/2041-8213/ada427","url":null,"abstract":"We introduce a novel deep learning framework based on long short-term memory networks to predict galactic cosmic-ray spectra on a one-day-ahead basis by leveraging historical solar activity data, overcoming limitations inherent in traditional transport models. By flexibly incorporating multiple solar parameters, such as the heliospheric magnetic field, solar wind speed, and sunspot numbers, the model achieves accurate short-term and long-term predictions of cosmic-ray flux. The addition of historical cosmic-ray flux data significantly enhances prediction accuracy, allowing the model to capture complex dependencies between past and future flux variations. Additionally, the model reliably predicts full cosmic-ray spectra for different particle species, enhancing its utility for comprehensive space weather forecasting. Our approach offers a scalable, data-driven alternative to traditional physics-based methods, ensuring robust daily and long-term forecasts. This work opens avenues for advanced models that can integrate broader observational data, with significant implications for space weather monitoring and mission planning.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936847","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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