Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acff69
Rayna Rampalli, Amy Smock, Elisabeth R. Newton, Kathryne J. Daniel, Jason L. Curtis
Abstract Recent space-based missions have ushered in a new era of observational astronomy, where high-cadence photometric light curves for thousands to millions of stars in the solar neighborhood can be used to test and apply stellar age-dating methods, including gyrochronology. Combined with precise kinematics, these data allow for powerful new insights into our understanding of the Milky Way’s dynamical history. Using TESS data, we build a series of rotation period measurement and confirmation pipelines and test them on 1560 stars across five benchmark samples: the Pleiades, Pisces–Eridanus, Praesepe, the Hyades, and field stars from the MEarth Project. Our pipelines’ recovery rates across these groups are, on average, 89%. We then apply these pipelines to 4085 likely single stars with TESS light curves in two interesting regions of Galactic action space. We identify 141 unique, rapidly rotating stars in highly eccentric orbits in the disk, some of which appear as rotationally young as the 120 Myr old Pleiades. Pending spectroscopic analysis to confirm their youth, this indicates that these stars were subject to fast-acting dynamical phenomena, the origin of which will be investigated in later papers in this series.
{"title":"Wrinkles in Time. I. Rapid Rotators Found in High-eccentricity Orbits","authors":"Rayna Rampalli, Amy Smock, Elisabeth R. Newton, Kathryne J. Daniel, Jason L. Curtis","doi":"10.3847/1538-4357/acff69","DOIUrl":"https://doi.org/10.3847/1538-4357/acff69","url":null,"abstract":"Abstract Recent space-based missions have ushered in a new era of observational astronomy, where high-cadence photometric light curves for thousands to millions of stars in the solar neighborhood can be used to test and apply stellar age-dating methods, including gyrochronology. Combined with precise kinematics, these data allow for powerful new insights into our understanding of the Milky Way’s dynamical history. Using TESS data, we build a series of rotation period measurement and confirmation pipelines and test them on 1560 stars across five benchmark samples: the Pleiades, Pisces–Eridanus, Praesepe, the Hyades, and field stars from the MEarth Project. Our pipelines’ recovery rates across these groups are, on average, 89%. We then apply these pipelines to 4085 likely single stars with TESS light curves in two interesting regions of Galactic action space. We identify 141 unique, rapidly rotating stars in highly eccentric orbits in the disk, some of which appear as rotationally young as the 120 Myr old Pleiades. Pending spectroscopic analysis to confirm their youth, this indicates that these stars were subject to fast-acting dynamical phenomena, the origin of which will be investigated in later papers in this series.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"138 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfca1
Dario Fadda, Jessica S. Sutter, Robert Minchin, Fiorella Polles
Abstract We present SOFIA observations with HAWC+ and FIFI-LS of the peculiar galaxy Arp 25, also known as NGC 2276 or UGC 3740, whose morphology is deformed by its impact with the intragroup medium of the NGC 2300 galaxy group. These observations show the first direct proof of the enhancement of [C ii ] emission due to shocks caused by ram pressure in a group of galaxies. By comparing the [C ii ] emission to UV attenuation, dust emission, PAH, and CO emission in different regions of the galaxy, we find a clear excess of [C ii ] emission along the impact front with the intragroup medium. We estimate that the shock due to the impact with the intragroup medium increases the [C ii ] emission along the shock front by 60% and the global [C ii ] emission by approximately 25% with respect to the predicted [C ii ] emission assuming only excitation caused by stellar radiation. This result shows the danger of interpreting [C ii ] emission as directly related to star formation since shocks and other mechanisms can significantly contribute to the total [C ii ] emission from galaxies in groups and clusters.
{"title":"Shock Enhanced [C ii] Emission from the Infalling Galaxy Arp 25 <sup>∗</sup>","authors":"Dario Fadda, Jessica S. Sutter, Robert Minchin, Fiorella Polles","doi":"10.3847/1538-4357/acfca1","DOIUrl":"https://doi.org/10.3847/1538-4357/acfca1","url":null,"abstract":"Abstract We present SOFIA observations with HAWC+ and FIFI-LS of the peculiar galaxy Arp 25, also known as NGC 2276 or UGC 3740, whose morphology is deformed by its impact with the intragroup medium of the NGC 2300 galaxy group. These observations show the first direct proof of the enhancement of [C ii ] emission due to shocks caused by ram pressure in a group of galaxies. By comparing the [C ii ] emission to UV attenuation, dust emission, PAH, and CO emission in different regions of the galaxy, we find a clear excess of [C ii ] emission along the impact front with the intragroup medium. We estimate that the shock due to the impact with the intragroup medium increases the [C ii ] emission along the shock front by 60% and the global [C ii ] emission by approximately 25% with respect to the predicted [C ii ] emission assuming only excitation caused by stellar radiation. This result shows the danger of interpreting [C ii ] emission as directly related to star formation since shocks and other mechanisms can significantly contribute to the total [C ii ] emission from galaxies in groups and clusters.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"43 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfa77
Alisa Galishnikova, Alexander Philippov, Eliot Quataert
Abstract Low-collisionality plasma in a magnetic field generically develops anisotropy in its distribution function with respect to the magnetic field direction. Motivated by the application to radiation from accretion flows and jets, we explore the effect of temperature anisotropy on synchrotron emission. We derive analytically and provide numerical fits for the polarized synchrotron emission and absorption coefficients for a relativistic bi-Maxwellian plasma (we do not consider Faraday conversion/rotation). Temperature anisotropy can significantly change how the synchrotron emission and absorption coefficients depend on observing angle with respect to the magnetic field. The emitted linear polarization fraction does not depend strongly on anisotropy, while the emitted circular polarization does. We apply our results to black hole imaging of Sgr A* and M87* by ray tracing a GRMHD simulation and assuming that the plasma temperature anisotropy is set by the thresholds of kinetic-scale anisotropy-driven instabilities. We find that the azimuthal asymmetry of the 230 GHz images can change by up to a factor of 3, accentuating ( T ⊥ > T ∥ ) or counteracting ( T ⊥ < T ∥ ) the image asymmetry produced by Doppler beaming. This can change the physical inferences from observations relative to models with an isotropic distribution function, e.g., by allowing for larger inclination between the line of sight and spin direction in Sgr A*. The observed image diameter and the size of the black hole shadow can also vary significantly due to plasma temperature anisotropy. We describe how the anisotropy of the plasma can affect future multifrequency and photon ring observations. We also calculate kinetic anisotropy-driven instabilities (mirror, whistler, and firehose) for relativistically hot plasmas.
{"title":"Polarized Anisotropic Synchrotron Emission and Absorption and Its Application to Black Hole Imaging","authors":"Alisa Galishnikova, Alexander Philippov, Eliot Quataert","doi":"10.3847/1538-4357/acfa77","DOIUrl":"https://doi.org/10.3847/1538-4357/acfa77","url":null,"abstract":"Abstract Low-collisionality plasma in a magnetic field generically develops anisotropy in its distribution function with respect to the magnetic field direction. Motivated by the application to radiation from accretion flows and jets, we explore the effect of temperature anisotropy on synchrotron emission. We derive analytically and provide numerical fits for the polarized synchrotron emission and absorption coefficients for a relativistic bi-Maxwellian plasma (we do not consider Faraday conversion/rotation). Temperature anisotropy can significantly change how the synchrotron emission and absorption coefficients depend on observing angle with respect to the magnetic field. The emitted linear polarization fraction does not depend strongly on anisotropy, while the emitted circular polarization does. We apply our results to black hole imaging of Sgr A* and M87* by ray tracing a GRMHD simulation and assuming that the plasma temperature anisotropy is set by the thresholds of kinetic-scale anisotropy-driven instabilities. We find that the azimuthal asymmetry of the 230 GHz images can change by up to a factor of 3, accentuating ( T ⊥ > T ∥ ) or counteracting ( T ⊥ < T ∥ ) the image asymmetry produced by Doppler beaming. This can change the physical inferences from observations relative to models with an isotropic distribution function, e.g., by allowing for larger inclination between the line of sight and spin direction in Sgr A*. The observed image diameter and the size of the black hole shadow can also vary significantly due to plasma temperature anisotropy. We describe how the anisotropy of the plasma can affect future multifrequency and photon ring observations. We also calculate kinetic anisotropy-driven instabilities (mirror, whistler, and firehose) for relativistically hot plasmas.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"81 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135411685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfe6d
Kuldeep Singh, Steffy Sara Varghese, Frank Verheest, Ioannis Kourakis
Abstract The Magnetospheric Multiscale Spacecraft (MMS) has detected the signature of electrostatic solitary waves (ESWs) occurring in the reconnection jet site of the Earth’s magnetotail (Liu et al.). These observations have motivated us to explore the mechanism underlying the formation of fast- and slow-mode ion-acoustic solitary waves in the magnetotail region. To this end, we have formulated a three-component magnetized plasma model consisting of nonthermal electrons and two cold ion beams streaming parallel and antiparallel to the magnetic field, respectively. In this work, we have examined the existence conditions for ion-acoustic subsonic waves in a suprathermal space plasma comprising two counterstreaming (drifting) ion beams interacting with a suprathermal electron background. An exact (nonperturbative) nonlinear technique has been adopted to examine the role of the beam velocity and the spectral index on the evolution of subsonic waves. Linear analysis reveals that subsonic waves are unstable when the beam velocity is lower than a threshold value; hence in this regime, only conventional supersonic (fast) waves are formed. On the other hand, when the beam velocity exceeds the threshold, either supersonic or subsonic waves may exist. The combined impact of the beam velocity and electron superthermality on the characteristics of subsonic solitary waves has been analyzed. Our results are shown to be in good agreement with observations of slow ESWs by the MMS spacecraft. Our findings will help to unfold the so-far unexplored dynamical characteristics of subsonic waves that may occur in the reconnection site of Earth’s magnetotail.
磁层多尺度航天器(MMS)探测到地球磁尾重联喷流部位发生的静电孤立波(ESWs)特征(Liu et al.)。这些观察结果促使我们探索磁尾区快速和慢模离子声孤立波形成的机制。为此，我们建立了一个由非热电子和两个冷离子束组成的三组分磁化等离子体模型，它们分别与磁场平行和反平行。在这项工作中，我们研究了由两个逆流(漂移)离子束与超热电子背景相互作用组成的超热空间等离子体中离子声亚音速波的存在条件。采用精确(非摄动)非线性技术研究了波束速度和谱指数对亚音速演化的影响。线性分析表明，当波束速度低于阈值时，亚音速不稳定;因此，在这种情况下，只形成常规的超音速(快)波。另一方面，当光束速度超过阈值时，可能存在超音速或亚音速波。分析了束流速度和电子超热度对亚音速孤立波特性的综合影响。我们的结果与MMS航天器对慢速ESWs的观测结果很好地吻合。我们的发现将有助于揭示迄今为止尚未探索的亚音速波的动力学特征，这些亚音速波可能发生在地球磁尾的重连点。
{"title":"On the Existence of Subsonic Solitary Waves Associated with Reconnection Jets in Earth’s Magnetotail","authors":"Kuldeep Singh, Steffy Sara Varghese, Frank Verheest, Ioannis Kourakis","doi":"10.3847/1538-4357/acfe6d","DOIUrl":"https://doi.org/10.3847/1538-4357/acfe6d","url":null,"abstract":"Abstract The Magnetospheric Multiscale Spacecraft (MMS) has detected the signature of electrostatic solitary waves (ESWs) occurring in the reconnection jet site of the Earth’s magnetotail (Liu et al.). These observations have motivated us to explore the mechanism underlying the formation of fast- and slow-mode ion-acoustic solitary waves in the magnetotail region. To this end, we have formulated a three-component magnetized plasma model consisting of nonthermal electrons and two cold ion beams streaming parallel and antiparallel to the magnetic field, respectively. In this work, we have examined the existence conditions for ion-acoustic subsonic waves in a suprathermal space plasma comprising two counterstreaming (drifting) ion beams interacting with a suprathermal electron background. An exact (nonperturbative) nonlinear technique has been adopted to examine the role of the beam velocity and the spectral index on the evolution of subsonic waves. Linear analysis reveals that subsonic waves are unstable when the beam velocity is lower than a threshold value; hence in this regime, only conventional supersonic (fast) waves are formed. On the other hand, when the beam velocity exceeds the threshold, either supersonic or subsonic waves may exist. The combined impact of the beam velocity and electron superthermality on the characteristics of subsonic solitary waves has been analyzed. Our results are shown to be in good agreement with observations of slow ESWs by the MMS spacecraft. Our findings will help to unfold the so-far unexplored dynamical characteristics of subsonic waves that may occur in the reconnection site of Earth’s magnetotail.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"33 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135412375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract It is proposed that the synchrotron emission from an internal shock with a decaying shock-generated magnetic field can account for the prompt emission of gamma-ray bursts (GRBs). Generally, a jet from the central engine of a GRB is launched with a significant magnetization, and thus there would be a background magnetic field, rather than only the shock-generated magnetic field, in the emission region. In this paper, we study the synchrotron emission of internal shocks with both a decaying shock-generated magnetic field and a nondecaying background magnetic field. It is found that a shoulder with spectral index −1/2 appears in the low-energy regime of the radiation spectrum. The shoulder becomes dominant by increasing the ratio of the background magnetic field energy to the initial value of the shock-generated magnetic field energy f B . Correspondingly, a radiation spectrum with two bumps or a plateau around the peak of the ν F ν − ν spectrum may appear. Owing to the decay of the shock-generated magnetic field, the radiation spectral morphology in the high-energy regime is not a power-law function even though a power-law distribution of electrons is injected. We apply our model to GRB 211211A, of which the hard main emission is suggested to originate from the synchrotron emission. Compared with the spectral fitting results with a Band function and the synchrotron emission from the standard straightforward internal shocks, our model presents a perfect fitting to the observations. The fitting results show that f B is around 0.41–0.99 for the hard main emission of this burst.
摘要提出了由内部激波与衰减激波磁场产生的同步辐射可以解释伽玛射线暴(GRBs)的提示发射。一般来说，从GRB中央发动机发射的射流具有明显的磁化强度，因此在发射区域会有背景磁场，而不仅仅是激波产生的磁场。在本文中，我们研究了内部激波在衰减的激波产生磁场和非衰减的背景磁场下的同步辐射。发现在辐射谱低能区出现一个谱指数为−1/2的肩。通过增加背景磁场能量与冲击产生的磁场能量f B的初始值之比，肩部占据主导地位。相应地，辐射谱在ν F ν−ν峰附近可能出现两个凸起或平台。由于激波产生的磁场的衰减，即使注入了电子的幂律分布，高能区域的辐射光谱形态也不是幂律函数。我们将该模型应用于GRB 211211A，认为GRB 211211A的硬主辐射来源于同步辐射。与带函数的光谱拟合结果和标准直接内激波的同步辐射相比，我们的模型与观测结果拟合得很好。拟合结果表明，该暴硬主发射的fb值约为0.41-0.99。
{"title":"Internal Shock with a Background Magnetic Field for the Prompt Emission of Gamma-Ray Bursts—A Case Study of GRB 211211A","authors":"Li Zhou, Da-Bin Lin, Xing Yang, Guo-Yu Li, Kuan Liu, Jing Li, En-Wei Liang","doi":"10.3847/1538-4357/acfede","DOIUrl":"https://doi.org/10.3847/1538-4357/acfede","url":null,"abstract":"Abstract It is proposed that the synchrotron emission from an internal shock with a decaying shock-generated magnetic field can account for the prompt emission of gamma-ray bursts (GRBs). Generally, a jet from the central engine of a GRB is launched with a significant magnetization, and thus there would be a background magnetic field, rather than only the shock-generated magnetic field, in the emission region. In this paper, we study the synchrotron emission of internal shocks with both a decaying shock-generated magnetic field and a nondecaying background magnetic field. It is found that a shoulder with spectral index −1/2 appears in the low-energy regime of the radiation spectrum. The shoulder becomes dominant by increasing the ratio of the background magnetic field energy to the initial value of the shock-generated magnetic field energy f B . Correspondingly, a radiation spectrum with two bumps or a plateau around the peak of the ν F ν − ν spectrum may appear. Owing to the decay of the shock-generated magnetic field, the radiation spectral morphology in the high-energy regime is not a power-law function even though a power-law distribution of electrons is injected. We apply our model to GRB 211211A, of which the hard main emission is suggested to originate from the synchrotron emission. Compared with the spectral fitting results with a Band function and the synchrotron emission from the standard straightforward internal shocks, our model presents a perfect fitting to the observations. The fitting results show that f B is around 0.41–0.99 for the hard main emission of this burst.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135456360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf5db
M. S. Nitschai, N. Neumayer, C. Clontz, M. Häberle, A. C. Seth, T.-O. Husser, S. Kamann, M. Alfaro-Cuello, N. Kacharov, A. Bellini, A. Dotter, S. Dreizler, A. Feldmeier-Krause, M. Latour, M. Libralato, A. P. Milone, R. Pechetti, G. van de Ven, K. Voggel, Daniel R. Weisz
Abstract Omega Centauri ( ω Cen) is the most massive globular cluster of the Milky Way and has been the focus of many studies that reveal the complexity of its stellar populations and kinematics. However, most previous studies have used photometric and spectroscopic data sets with limited spatial or magnitude coverage, while we aim to investigate it having full spatial coverage out to its half-light radius and stars ranging from the main sequence to the tip of the red giant branch. This is the first paper in a new survey of ω Cen that combines uniform imaging and spectroscopic data out to its half-light radius to study its stellar populations, kinematics, and formation history. In this paper, we present an unprecedented MUSE spectroscopic data set combining 87 new MUSE pointings with previous observations collected from guaranteed time observations. We extract spectra of more than 300,000 stars reaching more than 2 magnitudes below the main-sequence turnoff. We use these spectra to derive metallicity and line-of-sight velocity measurements and determine robust uncertainties on these quantities using repeat measurements. Applying quality cuts we achieve signal-to-noise ratios (S/Ns) of 16.47/73.51 and mean metallicity errors of 0.174/0.031 dex for the main-sequence stars (18 mag
{"title":"oMEGACat. I. MUSE Spectroscopy of 300,000 Stars within the Half-light Radius of ω Centauri","authors":"M. S. Nitschai, N. Neumayer, C. Clontz, M. Häberle, A. C. Seth, T.-O. Husser, S. Kamann, M. Alfaro-Cuello, N. Kacharov, A. Bellini, A. Dotter, S. Dreizler, A. Feldmeier-Krause, M. Latour, M. Libralato, A. P. Milone, R. Pechetti, G. van de Ven, K. Voggel, Daniel R. Weisz","doi":"10.3847/1538-4357/acf5db","DOIUrl":"https://doi.org/10.3847/1538-4357/acf5db","url":null,"abstract":"Abstract Omega Centauri ( ω Cen) is the most massive globular cluster of the Milky Way and has been the focus of many studies that reveal the complexity of its stellar populations and kinematics. However, most previous studies have used photometric and spectroscopic data sets with limited spatial or magnitude coverage, while we aim to investigate it having full spatial coverage out to its half-light radius and stars ranging from the main sequence to the tip of the red giant branch. This is the first paper in a new survey of ω Cen that combines uniform imaging and spectroscopic data out to its half-light radius to study its stellar populations, kinematics, and formation history. In this paper, we present an unprecedented MUSE spectroscopic data set combining 87 new MUSE pointings with previous observations collected from guaranteed time observations. We extract spectra of more than 300,000 stars reaching more than 2 magnitudes below the main-sequence turnoff. We use these spectra to derive metallicity and line-of-sight velocity measurements and determine robust uncertainties on these quantities using repeat measurements. Applying quality cuts we achieve signal-to-noise ratios (S/Ns) of 16.47/73.51 and mean metallicity errors of 0.174/0.031 dex for the main-sequence stars (18 mag <mag F 625 W < 22 mag) and red giant branch stars (16 mag <mag F 625 W < 10 mag), respectively. We correct the metallicities for atomic diffusion and identify foreground stars. This massive spectroscopic data set will enable future studies that will transform our understanding of ω Cen, allowing us to investigate the stellar populations, ages, and kinematics in great detail.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"14 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135510383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf8c3
Hang Gong, Ryan Urquhart, Alexandr Vinokurov, Yu Bai, Antonio Cabrera-Lavers, Sergei Fabrika, Liang Wang, Jifeng Liu
Abstract We have conducted long-slit spectroscopic observations and analyzed archival radio data for the ultraluminous X-ray source (ULX) NGC 4861 X-1. Our spectral line analysis unveils NGC 4861 X-1 as the fourth ULX situated within an X-ray photoionized nebula, following three previous findings made approximately two decades ago. Remarkably, we discover NGC 4861 X-1 also possesses a radio nebula emitting optically thin synchrotron radiation, which contradicts its X-ray photoionization and raises doubts about the four ULXs being a mere coincidence. Instead of gradually accumulating from different bands bit by bit, our multiband discovery is made all at once. Moreover, we tentatively perceive a faint continuum spectrum of the optical nebula. Further observations are needed to ascertain its radio structures and verify the optical continuum.
{"title":"Discovery of an X-Ray Photoionized Optical Nebula and a Radio Nebula Associated with the ULX NGC 4861 X-1","authors":"Hang Gong, Ryan Urquhart, Alexandr Vinokurov, Yu Bai, Antonio Cabrera-Lavers, Sergei Fabrika, Liang Wang, Jifeng Liu","doi":"10.3847/1538-4357/acf8c3","DOIUrl":"https://doi.org/10.3847/1538-4357/acf8c3","url":null,"abstract":"Abstract We have conducted long-slit spectroscopic observations and analyzed archival radio data for the ultraluminous X-ray source (ULX) NGC 4861 X-1. Our spectral line analysis unveils NGC 4861 X-1 as the fourth ULX situated within an X-ray photoionized nebula, following three previous findings made approximately two decades ago. Remarkably, we discover NGC 4861 X-1 also possesses a radio nebula emitting optically thin synchrotron radiation, which contradicts its X-ray photoionization and raises doubts about the four ULXs being a mere coincidence. Instead of gradually accumulating from different bands bit by bit, our multiband discovery is made all at once. Moreover, we tentatively perceive a faint continuum spectrum of the optical nebula. Further observations are needed to ascertain its radio structures and verify the optical continuum.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"5 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135516414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/ad00b8
Yunjing Wu, Zheng Cai, Jianan Li, Kristian Finlator, Marcel Neeleman, J. Xavier Prochaska, Bjorn H. C. Emonts, Shiwu Zhang, Feige Wang, Jinyi Yang, Ran Wang, Xiaohui Fan, Dandan Xu, Emmet Golden-Marx, Laura C. Keating, Joseph F. Hennawi
Abstract We report the first statistical analyses of [C ii ] and dust continuum observations in six strong O i absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [C ii ] emitter reported in Wu et al., we detect one O i -associated [C ii ] emitter in six fields. At redshifts of O i absorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s −1 . The averaged [C ii ]-detection upper limit is <0.06 Jy km s −1 (3 σ ), corresponding to the [C ii ] luminosity of L [C II ] < 5.8 × 10 7 L ⊙ and the [C ii ]-based star formation rate of SFR [C II ] <5.5 M ⊙ yr −1 . Cosmological simulations suggest that only ∼10 −2.5 [C ii ] emitters around O i absorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s −1 . If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side.
摘要本文首次对阿塔卡马大型毫米波/亚毫米波阵列(ALMA)获得的6个强毫米波吸收场再电离期末的[C ii]和尘埃连续体观测数据进行了统计分析。结合Wu等人报道的一个[C ii]发射器，我们在六个领域检测到一个O i相关的[C ii]发射器。在非检测场的O - i吸收体的红移中，在撞击参数为50 kpc和速度偏移在±200 km s - 1之间的范围内，没有发射体比我们的检测极限更亮。平均[C ii]探测上限为0.06 Jy km s−1 (3 σ)，对应于L [C ii] <的[C ii]光度;5.8 × 10.7 L⊙和SFR [Cⅱ]<5.5 M⊙yr−1的基于[Cⅱ]的恒星形成速率。宇宙学模拟表明，只有O i吸收器周围的~ 10−2.5 [C ii]发射器具有与我们的检测极限相当的SFR。虽然在六分之一的磁场中被发现，但从我们的ALMA观测中获得的发射器数量超过了数量级，这支持了导致金属富集的大质量星系的贡献是不可忽视的。此外，我们还发现了14个暂定的候选星系，它们在大撞击参数(>50 kpc)下的信噪比为≈4.3，并且在±600 km s−1以内具有较大的流出速度。如果这些探测在未来得到证实，那么在更大的距离上以更高的速度推动金属的机制需要从理论方面进一步探索。
{"title":"Searching for C ii Emission from the First Sample of z ∼ 6 O i Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array","authors":"Yunjing Wu, Zheng Cai, Jianan Li, Kristian Finlator, Marcel Neeleman, J. Xavier Prochaska, Bjorn H. C. Emonts, Shiwu Zhang, Feige Wang, Jinyi Yang, Ran Wang, Xiaohui Fan, Dandan Xu, Emmet Golden-Marx, Laura C. Keating, Joseph F. Hennawi","doi":"10.3847/1538-4357/ad00b8","DOIUrl":"https://doi.org/10.3847/1538-4357/ad00b8","url":null,"abstract":"Abstract We report the first statistical analyses of [C ii ] and dust continuum observations in six strong O i absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [C ii ] emitter reported in Wu et al., we detect one O i -associated [C ii ] emitter in six fields. At redshifts of O i absorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s −1 . The averaged [C ii ]-detection upper limit is <0.06 Jy km s −1 (3 σ ), corresponding to the [C ii ] luminosity of L [C II ] < 5.8 × 10 7 L ⊙ and the [C ii ]-based star formation rate of SFR [C II ] <5.5 M ⊙ yr −1 . Cosmological simulations suggest that only ∼10 −2.5 [C ii ] emitters around O i absorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s −1 . If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"53 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135564678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfd2f
Jongho Park, Keiichi Asada, Do-Young Byun
Abstract In this series of papers, we present new methods of frequency- and time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). In most existing calibration tools and pipelines, it has been assumed that instrumental polarization is constant over frequency within the instrument bandwidth and over time. The assumption is not always true and may prevent an accurate calibration, which can result in degradation of the quality of linear polarization images. In this paper, we present a method of frequency-dependent instrumental polarization calibration that is implemented in GPCAL, a recently developed polarization calibration pipeline. The method is tested using simulated data sets generated from real Very Long Baseline Array (VLBA) data. We present the results of applying the method to real VLBA data sets observed at 15 and 43 GHz. We were able to eliminate significant variability in cross-hand visibilities over frequency that is caused by frequency-dependent instrumental polarization. As a result of the calibration, linear polarization images were slightly to modestly improved as compared to those obtained without frequency-dependent instrumental polarization calibration. We discuss the reason for the minor impact of frequency-dependent instrumental polarization calibration on existing VLBA data sets and prospects for applying the method to future VLBI data sets, which are expected to provide very large bandwidths.
{"title":"Calibrating VLBI Polarization Data Using GPCAL. I. Frequency-dependent Calibration","authors":"Jongho Park, Keiichi Asada, Do-Young Byun","doi":"10.3847/1538-4357/acfd2f","DOIUrl":"https://doi.org/10.3847/1538-4357/acfd2f","url":null,"abstract":"Abstract In this series of papers, we present new methods of frequency- and time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). In most existing calibration tools and pipelines, it has been assumed that instrumental polarization is constant over frequency within the instrument bandwidth and over time. The assumption is not always true and may prevent an accurate calibration, which can result in degradation of the quality of linear polarization images. In this paper, we present a method of frequency-dependent instrumental polarization calibration that is implemented in GPCAL, a recently developed polarization calibration pipeline. The method is tested using simulated data sets generated from real Very Long Baseline Array (VLBA) data. We present the results of applying the method to real VLBA data sets observed at 15 and 43 GHz. We were able to eliminate significant variability in cross-hand visibilities over frequency that is caused by frequency-dependent instrumental polarization. As a result of the calibration, linear polarization images were slightly to modestly improved as compared to those obtained without frequency-dependent instrumental polarization calibration. We discuss the reason for the minor impact of frequency-dependent instrumental polarization calibration on existing VLBA data sets and prospects for applying the method to future VLBI data sets, which are expected to provide very large bandwidths.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"283 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acfed6
Eric Giunchi, Bianca M. Poggianti, Marco Gullieuszik, Alessia Moretti, Ariel Werle, Anita Zanella, Benedetta Vulcani, Stephanie Tonnesen, Daniela Calzetti, Callum Bellhouse, Claudia Scarlata, Cecilia Bacchini
Abstract We characterize the morphological properties of a statistically relevant sample of H α and UV young star-forming clumps and optical complexes, observed with the Hubble Space Telescope in six galaxies of the GASP sample undergoing ram pressure stripping. The catalogs comprise 2406 (323 in the tails) H α clumps, 3750 (899) UV clumps, and 424 tail optical complexes. About 15%–20% of the clumps and 50% of the complexes are resolved in size. We find that more than half of the complexes contain no H α clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps (0.27) than that for H α clumps (0.10) and does not correlate with almost any morphological property. This suggests that the clumps' number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, H α clumps, and UV clumps to a lesser extent, show a displacement from the complex center of 0.1–1 kpc, and in ∼60% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.
{"title":"Morphology of Star-forming Clumps in Ram-pressure Stripped Galaxies as Seen by HST","authors":"Eric Giunchi, Bianca M. Poggianti, Marco Gullieuszik, Alessia Moretti, Ariel Werle, Anita Zanella, Benedetta Vulcani, Stephanie Tonnesen, Daniela Calzetti, Callum Bellhouse, Claudia Scarlata, Cecilia Bacchini","doi":"10.3847/1538-4357/acfed6","DOIUrl":"https://doi.org/10.3847/1538-4357/acfed6","url":null,"abstract":"Abstract We characterize the morphological properties of a statistically relevant sample of H α and UV young star-forming clumps and optical complexes, observed with the Hubble Space Telescope in six galaxies of the GASP sample undergoing ram pressure stripping. The catalogs comprise 2406 (323 in the tails) H α clumps, 3750 (899) UV clumps, and 424 tail optical complexes. About 15%–20% of the clumps and 50% of the complexes are resolved in size. We find that more than half of the complexes contain no H α clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps (0.27) than that for H α clumps (0.10) and does not correlate with almost any morphological property. This suggests that the clumps' number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, H α clumps, and UV clumps to a lesser extent, show a displacement from the complex center of 0.1–1 kpc, and in ∼60% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"140 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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