Pub Date : 2025-03-24DOI: 10.3847/1538-4357/adb7ce
Tyler Schmaltz, Yue Hu and Alex Lazarian
Understanding the role of turbulence in shaping the interstellar medium (ISM) is crucial for studying star formation, molecular cloud evolution, and cosmic-ray propagation. Central to this is the measurement of the sonic Mach number (Ms), which quantifies the ratio of turbulent velocity to the sound speed. In this work, we introduce a convolutional-neural-network-(CNN)-based approach for estimating Ms directly from spectroscopic observations. The approach leverages the physical correlation between increasing Ms and the shock-induced small-scale fluctuations that alter the morphological features in intensity, velocity centroid, and velocity channel maps. These maps, derived from 3D magnetohydrodynamic turbulence simulations, serve as inputs for the CNN training. By learning the relationship between these structural features and the underlying turbulence properties, CNNs can predict Ms under various conditions, including different magnetic fields and levels of observational noise. The median uncertainty of the CNN-predicted Ms ranges from 0.5 to 1.5 depending on the noise level. While intensity maps offer lower uncertainty, channel maps have the advantage of predicting the 3D Ms distribution, which is crucial in estimating 3D magnetic field strength. Our results demonstrate that machine-learning-based tools can effectively characterize complex turbulence properties in the ISM.
{"title":"Estimating the Sonic Mach Number in the Interstellar Medium with Convolutional Neural Networks","authors":"Tyler Schmaltz, Yue Hu and Alex Lazarian","doi":"10.3847/1538-4357/adb7ce","DOIUrl":"https://doi.org/10.3847/1538-4357/adb7ce","url":null,"abstract":"Understanding the role of turbulence in shaping the interstellar medium (ISM) is crucial for studying star formation, molecular cloud evolution, and cosmic-ray propagation. Central to this is the measurement of the sonic Mach number (Ms), which quantifies the ratio of turbulent velocity to the sound speed. In this work, we introduce a convolutional-neural-network-(CNN)-based approach for estimating Ms directly from spectroscopic observations. The approach leverages the physical correlation between increasing Ms and the shock-induced small-scale fluctuations that alter the morphological features in intensity, velocity centroid, and velocity channel maps. These maps, derived from 3D magnetohydrodynamic turbulence simulations, serve as inputs for the CNN training. By learning the relationship between these structural features and the underlying turbulence properties, CNNs can predict Ms under various conditions, including different magnetic fields and levels of observational noise. The median uncertainty of the CNN-predicted Ms ranges from 0.5 to 1.5 depending on the noise level. While intensity maps offer lower uncertainty, channel maps have the advantage of predicting the 3D Ms distribution, which is crucial in estimating 3D magnetic field strength. Our results demonstrate that machine-learning-based tools can effectively characterize complex turbulence properties in the ISM.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677529","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 : 2025-03-24DOI: 10.3847/1538-4357/adbb53
Anna C. Childs, Alexa P. S. Hua, Rebecca G. Martin, Chao-Chin Yang, 朝欽 楊 and Aaron M. Geller
We identify observational signatures suggesting a history of dynamical instability in 26 out of 34 M-dwarf multi-planet systems containing no large planets. These systems may have primarily formed in a gas-rich environment, potentially hosted more planets, and were more compact. We extend previous simulations of the formation of the TRAPPIST-1 system to 100 Myr to test the stability of these systems without gas. We find that the absence of a strong mean motion resonance in the innermost planet pair and the absence of three-body resonances throughout the system are likely to result in the merging and ejection of planets after the gas disk disperses. The runs that experience such an instability tend to produce final systems with lower multiplicities, period ratios larger than two, increased orbital spacings, higher planetary angular momentum deficits, and slightly smaller mass ratios between adjacent planets. Remarkably, we find these same trends in the observations of M-dwarf multi-planet systems containing no large planets. Our work allows us to identify specific systems that may have experienced an instability, and it suggests that only ∼25% of these systems formed in their current observed state, while most systems were likely more compact and multiplicitous earlier in time. Previous research indicates that planets that have experienced a late-stage giant impact may potentially be more habitable than those that did not. With this in mind, we suggest systems around M-dwarfs that contain period ratios larger than two be given priority in the search for habitable worlds.
{"title":"Observational Signatures of a Previous Dynamical Instability in Multi-planet M-dwarf Systems","authors":"Anna C. Childs, Alexa P. S. Hua, Rebecca G. Martin, Chao-Chin Yang, 朝欽 楊 and Aaron M. Geller","doi":"10.3847/1538-4357/adbb53","DOIUrl":"https://doi.org/10.3847/1538-4357/adbb53","url":null,"abstract":"We identify observational signatures suggesting a history of dynamical instability in 26 out of 34 M-dwarf multi-planet systems containing no large planets. These systems may have primarily formed in a gas-rich environment, potentially hosted more planets, and were more compact. We extend previous simulations of the formation of the TRAPPIST-1 system to 100 Myr to test the stability of these systems without gas. We find that the absence of a strong mean motion resonance in the innermost planet pair and the absence of three-body resonances throughout the system are likely to result in the merging and ejection of planets after the gas disk disperses. The runs that experience such an instability tend to produce final systems with lower multiplicities, period ratios larger than two, increased orbital spacings, higher planetary angular momentum deficits, and slightly smaller mass ratios between adjacent planets. Remarkably, we find these same trends in the observations of M-dwarf multi-planet systems containing no large planets. Our work allows us to identify specific systems that may have experienced an instability, and it suggests that only ∼25% of these systems formed in their current observed state, while most systems were likely more compact and multiplicitous earlier in time. Previous research indicates that planets that have experienced a late-stage giant impact may potentially be more habitable than those that did not. With this in mind, we suggest systems around M-dwarfs that contain period ratios larger than two be given priority in the search for habitable worlds.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677583","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 : 2025-03-24DOI: 10.3847/1538-4357/adba62
C. J. Anderson, P. Berger, T.-C. Chang, O. Doré, S. Brown, S. Levin and M. Seiffert
We present six nearly full-sky maps made from data taken by radiometers on the Juno satellite during its 5 yr flight to Jupiter. The maps represent integrated emission over ∼4% passbands spaced approximately in octaves between 600 MHz and 21.9 GHz. Long-timescale offset drifts are removed in all bands, and, for the two lowest-frequency bands, gain drifts are also removed from the maps via a self-calibration algorithm similar to the NPIPE pipeline used by the Planck Collaboration. We show that, after this solution is applied, statistical noise in the maps is consistent with thermal radiometer noise and expected levels of correlated noise on the gain and noise drift solutions. We verify our map solutions with several consistency tests and end-to-end simulations. We also estimate the level of systematic pixelization noise and polarization leakage via simulations.
{"title":"The Radio and Microwave Sky as Seen by Juno on its Mission to Jupiter","authors":"C. J. Anderson, P. Berger, T.-C. Chang, O. Doré, S. Brown, S. Levin and M. Seiffert","doi":"10.3847/1538-4357/adba62","DOIUrl":"https://doi.org/10.3847/1538-4357/adba62","url":null,"abstract":"We present six nearly full-sky maps made from data taken by radiometers on the Juno satellite during its 5 yr flight to Jupiter. The maps represent integrated emission over ∼4% passbands spaced approximately in octaves between 600 MHz and 21.9 GHz. Long-timescale offset drifts are removed in all bands, and, for the two lowest-frequency bands, gain drifts are also removed from the maps via a self-calibration algorithm similar to the NPIPE pipeline used by the Planck Collaboration. We show that, after this solution is applied, statistical noise in the maps is consistent with thermal radiometer noise and expected levels of correlated noise on the gain and noise drift solutions. We verify our map solutions with several consistency tests and end-to-end simulations. We also estimate the level of systematic pixelization noise and polarization leakage via simulations.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677582","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 : 2025-03-24DOI: 10.3847/1538-4357/adb7d9
Qi-Bin Sun, Sheng-Bang Qian, Li-Ying Zhu, Qin-Mei Li, Fu-Xing Li, Min-Yu Li and Ping Li
Dwarf novae (DNe) are semidetached binaries, where a white dwarf accretes material from a cool main-sequence companion via an accretion disk, and are known for their intermittent outbursts, making them key systems for studying accretion physics. The accumulation of large survey data sets has challenged traditional models, which assumed that the disk remains hot and cannot produce superoutbursts during the standstill of a Z Camelopardalis (Z Cam)-type DN and that superoutbursts require a mass ratio of q = M2/M1 ≤ 0.25–0.33. Here we report the detection of superoutbursts and positive superhumps (PSHs) during a standstill in the Z Cam-type star AT Cnc with a mass ratio larger than 0.33. Notably, the PSHs evolve gradually before the superoutburst begins, suggesting that an eccentric, precessing disk forms first, with the superoutburst occurring as the disk radius continues to expand. These findings provide the first detailed observational evidence of superoutbursts and PSHs occurring during standstill, offering important new insights into the classification of DNe and the underlying mechanisms of outbursts.
{"title":"Superoutbursts and Positive Superhumps Occurred during the Standstill of a Z Cam-type Dwarf Nova","authors":"Qi-Bin Sun, Sheng-Bang Qian, Li-Ying Zhu, Qin-Mei Li, Fu-Xing Li, Min-Yu Li and Ping Li","doi":"10.3847/1538-4357/adb7d9","DOIUrl":"https://doi.org/10.3847/1538-4357/adb7d9","url":null,"abstract":"Dwarf novae (DNe) are semidetached binaries, where a white dwarf accretes material from a cool main-sequence companion via an accretion disk, and are known for their intermittent outbursts, making them key systems for studying accretion physics. The accumulation of large survey data sets has challenged traditional models, which assumed that the disk remains hot and cannot produce superoutbursts during the standstill of a Z Camelopardalis (Z Cam)-type DN and that superoutbursts require a mass ratio of q = M2/M1 ≤ 0.25–0.33. Here we report the detection of superoutbursts and positive superhumps (PSHs) during a standstill in the Z Cam-type star AT Cnc with a mass ratio larger than 0.33. Notably, the PSHs evolve gradually before the superoutburst begins, suggesting that an eccentric, precessing disk forms first, with the superoutburst occurring as the disk radius continues to expand. These findings provide the first detailed observational evidence of superoutbursts and PSHs occurring during standstill, offering important new insights into the classification of DNe and the underlying mechanisms of outbursts.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677532","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 : 2025-03-24DOI: 10.3847/1538-4357/adba59
Apurba Bera, Clancy W. James, Mark M. McKinnon, Ronald D. Ekers, Tyson Dial, Adam T. Deller, Keith W. Bannister, Marcin Glowacki and Ryan M. Shannon
Fast radio bursts (FRBs) are highly energetic events of short-duration intense radio emission, the origin of which remains elusive. Polarization of the FRB signals carries information about the emission source as well as the magnetoionic media the signal passes through before reaching terrestrial radio telescopes. Currently known FRBs show a diverse range of polarization, sometimes with complex features, making it challenging to describe them in a unified model. FRB 20230708A and FRB 20210912A are two bright and highly polarized (apparently) one-off FRBs detected in the Commensal Real-time ASKAP Fast Transients survey with the Australian Square Kilometre Array Pathfinder (ASKAP) that exhibit time-dependent conversion between linear and circular polarizations as well as intraburst (apparent) variation of the Faraday rotation measure. We investigate the intraburst temporal evolution of the polarization state of radio emission in these two events using the Poincaré sphere representation and find that the trajectories of the polarization state are well described by great circles on the Poincaré sphere. These polarization features may be signatures of a transition between two partially coherent orthogonal polarization modes or propagation through a birefringent medium. We find that the observed variations of the polarization states of these two FRBs are qualitatively consistent with a magnetospheric origin of the bursts and the effects of propagation through a birefringent medium with linearly polarized modes located close to the emission source—likely in the outer magnetosphere or near-wind region of a neutron star.
{"title":"Unusual Intraburst Variations of Polarization States in FRB 20210912A and FRB 20230708A: Effects of Plasma Birefringence?","authors":"Apurba Bera, Clancy W. James, Mark M. McKinnon, Ronald D. Ekers, Tyson Dial, Adam T. Deller, Keith W. Bannister, Marcin Glowacki and Ryan M. Shannon","doi":"10.3847/1538-4357/adba59","DOIUrl":"https://doi.org/10.3847/1538-4357/adba59","url":null,"abstract":"Fast radio bursts (FRBs) are highly energetic events of short-duration intense radio emission, the origin of which remains elusive. Polarization of the FRB signals carries information about the emission source as well as the magnetoionic media the signal passes through before reaching terrestrial radio telescopes. Currently known FRBs show a diverse range of polarization, sometimes with complex features, making it challenging to describe them in a unified model. FRB 20230708A and FRB 20210912A are two bright and highly polarized (apparently) one-off FRBs detected in the Commensal Real-time ASKAP Fast Transients survey with the Australian Square Kilometre Array Pathfinder (ASKAP) that exhibit time-dependent conversion between linear and circular polarizations as well as intraburst (apparent) variation of the Faraday rotation measure. We investigate the intraburst temporal evolution of the polarization state of radio emission in these two events using the Poincaré sphere representation and find that the trajectories of the polarization state are well described by great circles on the Poincaré sphere. These polarization features may be signatures of a transition between two partially coherent orthogonal polarization modes or propagation through a birefringent medium. We find that the observed variations of the polarization states of these two FRBs are qualitatively consistent with a magnetospheric origin of the bursts and the effects of propagation through a birefringent medium with linearly polarized modes located close to the emission source—likely in the outer magnetosphere or near-wind region of a neutron star.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"93 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677580","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 : 2025-03-24DOI: 10.3847/1538-4357/adb8dc
Lauren M. Foster, Laura C. Parker, Stephen Gwyn, Ian D. Roberts, James E. Taylor, Michael J. Hudson, Alan W. McConnachie and Thomas de Boer
Ram pressure stripping is a well-known environmental quenching mechanism that removes gas from galaxies infalling into groups and clusters. In some extreme examples of ram pressure stripping, galaxies with extended gas tails show evidence of enhanced star formation prior to quenching. In this work we use a sample of 5277 local satellite galaxies in which a stripped tail of gas has not necessarily been observed, to quantify the strength of ram-pressure-enhanced star formation and compare these results to a control sample of 8360 field galaxies. We use u-band imaging from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) as a star formation tracer and several metrics to quantify star formation asymmetry. We compare these results to environmental properties of the galaxy, such as their time since infall and host halo mass, to constrain the degree of ram-pressure-enhanced star formation as a function of environment. We find no significant differences between the satellite and the field samples. We further restrict our sample to galaxies which we most expect to be experiencing significant ram pressure but find no strong evidence of these galaxies having systematically enhanced star formation. Finally, we investigate the properties of the most asymmetric galaxies in our sample and again find no strong evidence of ram-pressure-induced star formation enhancement. We conclude that any star formation enhancement must be small for infalling galaxies, suggesting that this effect is either uncommon or short-lived.
{"title":"No Evidence of Asymmetrically Enhanced Star Formation in Infalling Galaxies in UNIONS","authors":"Lauren M. Foster, Laura C. Parker, Stephen Gwyn, Ian D. Roberts, James E. Taylor, Michael J. Hudson, Alan W. McConnachie and Thomas de Boer","doi":"10.3847/1538-4357/adb8dc","DOIUrl":"https://doi.org/10.3847/1538-4357/adb8dc","url":null,"abstract":"Ram pressure stripping is a well-known environmental quenching mechanism that removes gas from galaxies infalling into groups and clusters. In some extreme examples of ram pressure stripping, galaxies with extended gas tails show evidence of enhanced star formation prior to quenching. In this work we use a sample of 5277 local satellite galaxies in which a stripped tail of gas has not necessarily been observed, to quantify the strength of ram-pressure-enhanced star formation and compare these results to a control sample of 8360 field galaxies. We use u-band imaging from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) as a star formation tracer and several metrics to quantify star formation asymmetry. We compare these results to environmental properties of the galaxy, such as their time since infall and host halo mass, to constrain the degree of ram-pressure-enhanced star formation as a function of environment. We find no significant differences between the satellite and the field samples. We further restrict our sample to galaxies which we most expect to be experiencing significant ram pressure but find no strong evidence of these galaxies having systematically enhanced star formation. Finally, we investigate the properties of the most asymmetric galaxies in our sample and again find no strong evidence of ram-pressure-induced star formation enhancement. We conclude that any star formation enhancement must be small for infalling galaxies, suggesting that this effect is either uncommon or short-lived.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677581","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 : 2025-03-24DOI: 10.3847/1538-4357/ada287
Yanqin Wu, Kadin Worthen, Alexis Brandeker and Christine Chen
Chemical compositions of planets reveal much about their formation environments. Such information is well sought-after in studies of solar system bodies and extrasolar ones. Here, we investigate the composition of planetesimals in the β Pictoris debris disk by way of its secondary gas disk. We are stimulated by the recent JWST detection of an Ar ii emission line and aim to reproduce extensive measurements from the past four decades. Our photoionization model reveals that the gas has to be heavily enriched in C, N, O, and Ar (but not S and P), by a uniform factor of about 100 relative to other metals. Such an abundance pattern is both reminiscent of, and different from, that of Jupiter's atmosphere. The fact that Ar, the most volatile and therefore the hardest to capture into solids, is equally enriched as C, N, and O suggests that the planetesimals were formed in a very cold region (T ≤ 20–35 K), possibly with the help of entrapment if water ice is overabundant. In the debris disk phase, these volatiles are preferentially outgassed from the dust grains, likely via photodesorption. The debris grains must be “dirty” aggregates of icy and refractory clusters. Lastly, the observed strength of the Ar ii line can only be explained if the star β Pic (a young A6V star) has sizable chromospheric and coronal emissions, on par with those from the modern Sun. In summary, observations of the β Pic gas disk rewind the clock to reveal the formation environment of planetesimals.
{"title":"Argon in β Pictoris–Entrapment and Release of Volatile in Disks","authors":"Yanqin Wu, Kadin Worthen, Alexis Brandeker and Christine Chen","doi":"10.3847/1538-4357/ada287","DOIUrl":"https://doi.org/10.3847/1538-4357/ada287","url":null,"abstract":"Chemical compositions of planets reveal much about their formation environments. Such information is well sought-after in studies of solar system bodies and extrasolar ones. Here, we investigate the composition of planetesimals in the β Pictoris debris disk by way of its secondary gas disk. We are stimulated by the recent JWST detection of an Ar ii emission line and aim to reproduce extensive measurements from the past four decades. Our photoionization model reveals that the gas has to be heavily enriched in C, N, O, and Ar (but not S and P), by a uniform factor of about 100 relative to other metals. Such an abundance pattern is both reminiscent of, and different from, that of Jupiter's atmosphere. The fact that Ar, the most volatile and therefore the hardest to capture into solids, is equally enriched as C, N, and O suggests that the planetesimals were formed in a very cold region (T ≤ 20–35 K), possibly with the help of entrapment if water ice is overabundant. In the debris disk phase, these volatiles are preferentially outgassed from the dust grains, likely via photodesorption. The debris grains must be “dirty” aggregates of icy and refractory clusters. Lastly, the observed strength of the Ar ii line can only be explained if the star β Pic (a young A6V star) has sizable chromospheric and coronal emissions, on par with those from the modern Sun. In summary, observations of the β Pic gas disk rewind the clock to reveal the formation environment of planetesimals.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"123 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677465","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 : 2025-03-24DOI: 10.3847/1538-4357/adb7d8
Wensi Wang, Rui Liu, Jiong Qiu, Jinhan Guo and Yuming Wang
The buildup of the preeruptive magnetic field configuration and the eruption onset mechanism are critical yet poorly understood in solar eruptions. Coronal structures like sigmoids and filaments have been identified as preeruptive magnetic structures; their associated preflare motions as well as preflare brightenings have been identified as precursor signatures, yet none of these definitively lead to eruptions, and the cause and effect is contentious. Most importantly, how the preeruptive coronal structure evolves with the photospheric magnetic field is elusive. Here we report the development of the photospheric nonneutralized electric current associated with the buildup of a preeruptive coronal structure observed as a bundle of hot low-lying coronal loops collectively taking a sigmoidal shape. The significant nonneutralized electric current appeared several hours ahead of the formation of the preeruptive structure. The buildup of the preeruptive structure in the corona was simultaneous with the gradual extension of the nonneutralized electric current in the photosphere. The synchronous evolution seemed to stop when intermittent brightening occurred along the preeruptive structure in the corona. The preflare brightening lasted for about 4 hr, with two ribbon-like structures matching the nonneutralized electric current. Eventually, the preeruptive structure evolved into a magnetic flux rope (MFR) and erupted. Quantitative measurements indicate that the significant nonneutralized electric current also flows through the footpoints of the erupting MFR, which are well identified by a pair of conjugate dimmings. The evolution of the photospheric nonneutralized electric current is demonstrated to signal the buildup of the preeruptive structure and the imminent eruption.
{"title":"The Origin of a Preeruptive Magnetic Structure with Significant Nonneutralized Electric Current","authors":"Wensi Wang, Rui Liu, Jiong Qiu, Jinhan Guo and Yuming Wang","doi":"10.3847/1538-4357/adb7d8","DOIUrl":"https://doi.org/10.3847/1538-4357/adb7d8","url":null,"abstract":"The buildup of the preeruptive magnetic field configuration and the eruption onset mechanism are critical yet poorly understood in solar eruptions. Coronal structures like sigmoids and filaments have been identified as preeruptive magnetic structures; their associated preflare motions as well as preflare brightenings have been identified as precursor signatures, yet none of these definitively lead to eruptions, and the cause and effect is contentious. Most importantly, how the preeruptive coronal structure evolves with the photospheric magnetic field is elusive. Here we report the development of the photospheric nonneutralized electric current associated with the buildup of a preeruptive coronal structure observed as a bundle of hot low-lying coronal loops collectively taking a sigmoidal shape. The significant nonneutralized electric current appeared several hours ahead of the formation of the preeruptive structure. The buildup of the preeruptive structure in the corona was simultaneous with the gradual extension of the nonneutralized electric current in the photosphere. The synchronous evolution seemed to stop when intermittent brightening occurred along the preeruptive structure in the corona. The preflare brightening lasted for about 4 hr, with two ribbon-like structures matching the nonneutralized electric current. Eventually, the preeruptive structure evolved into a magnetic flux rope (MFR) and erupted. Quantitative measurements indicate that the significant nonneutralized electric current also flows through the footpoints of the erupting MFR, which are well identified by a pair of conjugate dimmings. The evolution of the photospheric nonneutralized electric current is demonstrated to signal the buildup of the preeruptive structure and the imminent eruption.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677531","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 : 2025-03-24DOI: 10.3847/1538-4357/adbbda
Hui Peng and Yu Yu
Fast radio bursts (FRBs), millisecond-duration radio transient events, possess the potential to serve as excellent cosmological probes. The FRB redshift distribution contains information about the FRB sources, providing key constraints on the types of engines. However, it is quite challenging to obtain the FRB redshifts due to the poor localization and the faintness of the host galaxies. This reality severely restricts the application prospects and study of the physical origins of FRBs. We propose that the clustering of observed FRBs can be an effective approach to address this issue without needing to accurately model dispersion measure (DM) contributions from the host galaxy and the immediate environment of the source. Using the clustering of 5 × 107 simulated FRBs from future observations with sensitivity similar to the second phase of the Square Kilometre Array, we show that in extragalactic DM space, the redshift distributions can be accurately reconstructed, and the mean redshift for FRBs between 384.8 and 1450.3 pc cm−3 can be constrained to ∼0.001 ± 0.003(1 + z). The results demonstrate the potential of FRB clustering to constrain redshift distributions and provide valuable insights into FRB source models and cosmological applications.
{"title":"Redshift Distributions of Fast Radio Bursts Inferred Using Clustering in Dispersion Measure Space","authors":"Hui Peng and Yu Yu","doi":"10.3847/1538-4357/adbbda","DOIUrl":"https://doi.org/10.3847/1538-4357/adbbda","url":null,"abstract":"Fast radio bursts (FRBs), millisecond-duration radio transient events, possess the potential to serve as excellent cosmological probes. The FRB redshift distribution contains information about the FRB sources, providing key constraints on the types of engines. However, it is quite challenging to obtain the FRB redshifts due to the poor localization and the faintness of the host galaxies. This reality severely restricts the application prospects and study of the physical origins of FRBs. We propose that the clustering of observed FRBs can be an effective approach to address this issue without needing to accurately model dispersion measure (DM) contributions from the host galaxy and the immediate environment of the source. Using the clustering of 5 × 107 simulated FRBs from future observations with sensitivity similar to the second phase of the Square Kilometre Array, we show that in extragalactic DM space, the redshift distributions can be accurately reconstructed, and the mean redshift for FRBs between 384.8 and 1450.3 pc cm−3 can be constrained to ∼0.001 ± 0.003(1 + z). The results demonstrate the potential of FRB clustering to constrain redshift distributions and provide valuable insights into FRB source models and cosmological applications.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677585","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 : 2025-03-24DOI: 10.3847/1538-4357/adb8e1
Olivia R. Cooper, Gabriel Brammer, Kasper E. Heintz, Sune Toft, Caitlin M. Casey, David J. Setton, Anna de Graaff, Leindert Boogaard, Nikko J. Cleri, Steven Gillman, Rashmi Gottumukkala, Jenny E. Greene, Bitten Gullberg, Michaela Hirschmann, Raphael E. Hviding, Erini Lambrides, Joel Leja, Arianna S. Long, Sinclaire M. Manning, Michael V. Maseda, Ian McConachie, Jed McKinney, Desika Narayanan, Sedona H. Price, Victoria Strait, Katherine A. Suess, Andrea Weibel and Christina C. Williams
The dearth of high-quality spectroscopy of dusty star-forming galaxies (DSFGs)—the main drivers of the assembly of dust and stellar mass at the peak of activity in the Universe—greatly hinders our ability to interpret their physical processes and evolutionary pathways. We present JWST/NIRSpec observations from RUBIES of four submillimeter-selected, Atacama Large Millimeter/submillimeter Array (ALMA)-detected DSFGs at cosmic noon, z ∼ 2.3–2.7. While photometry uniformly suggests vigorous ongoing star formation for the entire sample in line with canonical DSFGs, the spectra differ: one source has spectroscopic evidence of an evolved stellar population, indicating a recent transition to a post-starburst phase, while the remainder show strong spectroscopic signatures of ongoing starbursts. All four galaxies are infrared luminous (log10LIR/L⊙ > 12.4), massive (log10M⋆/M⊙ > 11), and very dust obscured (AV ∼ 3–4 ABmag). Leveraging detections of multiple Balmer and Paschen lines, we derive an optical attenuation curve consistent with Calzetti overall, yet an optical extinction ratio RV ∼ 2.5, potentially indicating smaller dust grains or differences in star-dust geometry. This case study provides some of the first detailed spectroscopic evidence that the DSFGs encompass a heterogeneous sample spanning a range of star formation properties and evolutionary stages, and illustrates the advantages of synergistic JWST and ALMA analysis of DSFGs.
{"title":"RUBIES: JWST/NIRSpec Resolves Evolutionary Phases of Dusty Star-forming Galaxies at z ∼ 2","authors":"Olivia R. Cooper, Gabriel Brammer, Kasper E. Heintz, Sune Toft, Caitlin M. Casey, David J. Setton, Anna de Graaff, Leindert Boogaard, Nikko J. Cleri, Steven Gillman, Rashmi Gottumukkala, Jenny E. Greene, Bitten Gullberg, Michaela Hirschmann, Raphael E. Hviding, Erini Lambrides, Joel Leja, Arianna S. Long, Sinclaire M. Manning, Michael V. Maseda, Ian McConachie, Jed McKinney, Desika Narayanan, Sedona H. Price, Victoria Strait, Katherine A. Suess, Andrea Weibel and Christina C. Williams","doi":"10.3847/1538-4357/adb8e1","DOIUrl":"https://doi.org/10.3847/1538-4357/adb8e1","url":null,"abstract":"The dearth of high-quality spectroscopy of dusty star-forming galaxies (DSFGs)—the main drivers of the assembly of dust and stellar mass at the peak of activity in the Universe—greatly hinders our ability to interpret their physical processes and evolutionary pathways. We present JWST/NIRSpec observations from RUBIES of four submillimeter-selected, Atacama Large Millimeter/submillimeter Array (ALMA)-detected DSFGs at cosmic noon, z ∼ 2.3–2.7. While photometry uniformly suggests vigorous ongoing star formation for the entire sample in line with canonical DSFGs, the spectra differ: one source has spectroscopic evidence of an evolved stellar population, indicating a recent transition to a post-starburst phase, while the remainder show strong spectroscopic signatures of ongoing starbursts. All four galaxies are infrared luminous (log10LIR/L⊙ > 12.4), massive (log10M⋆/M⊙ > 11), and very dust obscured (AV ∼ 3–4 ABmag). Leveraging detections of multiple Balmer and Paschen lines, we derive an optical attenuation curve consistent with Calzetti overall, yet an optical extinction ratio RV ∼ 2.5, potentially indicating smaller dust grains or differences in star-dust geometry. This case study provides some of the first detailed spectroscopic evidence that the DSFGs encompass a heterogeneous sample spanning a range of star formation properties and evolutionary stages, and illustrates the advantages of synergistic JWST and ALMA analysis of DSFGs.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677535","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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