Himanshu Tiwari, Benjamin McKinley, Cathryn M. Trott, Nithyanandan Thyagarajan
Abstract Radio interferometers can potentially detect the sky-averaged signal from the Cosmic Dawn (CD) and the Epoch of Reionisation (EoR) by studying the Moon as a thermal block to the foreground sky. The first step is to mitigate the Earth-based RFI reflections (Earthshine) from the Moon, which significantly contaminate the FM band ≈ 88 – 110 MHz, crucial to CD-EoR science. We analysed MWA phase-I data from 72 – 180 MHz at 40 kHz resolution to understand the nature of Earthshine over three observing nights. We took two approaches to correct the Earthshine component from the Moon. In the first method, we mitigated the Earthshine using the flux density of the two components from the data, while in the second method, we used simulated flux density based on an FM catalogue to mitigate the Earthshine. Using these methods, we were able to recover the expected Galactic foreground temperature of the patch of sky obscured by the Moon. We performed a joint analysis of the Galactic foregrounds and the Moon’s intrinsic temperature ( T Moon ) while assuming that the Moon has a constant thermal temperature throughout three epochs. We found T Moon to be at 184.4±2.6 K and 173.8±2.5 K using the first and the second methods, respectively, and the best-fit values of the Galactic spectral index ( α ) to be within the 5% uncertainty level when compared with the global sky models. Compared with our previous work, these results improved constraints on the Galactic spectral index and the Moon’s intrinsic temperature. We also simulated the Earthshine atMWA between November and December 2023 to find suitable observing times less affected by the Earthshine. Such observing windows act as Earthshine avoidance and can be used to perform future global CD-EoR experiments using the Moon with the MWA.
{"title":"Measuring the global 21-cm signal with the MWA-II: improved characterisation of lunar-reflected radio frequency interference","authors":"Himanshu Tiwari, Benjamin McKinley, Cathryn M. Trott, Nithyanandan Thyagarajan","doi":"10.1017/pasa.2023.57","DOIUrl":"https://doi.org/10.1017/pasa.2023.57","url":null,"abstract":"Abstract Radio interferometers can potentially detect the sky-averaged signal from the Cosmic Dawn (CD) and the Epoch of Reionisation (EoR) by studying the Moon as a thermal block to the foreground sky. The first step is to mitigate the Earth-based RFI reflections (Earthshine) from the Moon, which significantly contaminate the FM band ≈ 88 – 110 MHz, crucial to CD-EoR science. We analysed MWA phase-I data from 72 – 180 MHz at 40 kHz resolution to understand the nature of Earthshine over three observing nights. We took two approaches to correct the Earthshine component from the Moon. In the first method, we mitigated the Earthshine using the flux density of the two components from the data, while in the second method, we used simulated flux density based on an FM catalogue to mitigate the Earthshine. Using these methods, we were able to recover the expected Galactic foreground temperature of the patch of sky obscured by the Moon. We performed a joint analysis of the Galactic foregrounds and the Moon’s intrinsic temperature ( T Moon ) while assuming that the Moon has a constant thermal temperature throughout three epochs. We found T Moon to be at 184.4±2.6 K and 173.8±2.5 K using the first and the second methods, respectively, and the best-fit values of the Galactic spectral index ( α ) to be within the 5% uncertainty level when compared with the global sky models. Compared with our previous work, these results improved constraints on the Galactic spectral index and the Moon’s intrinsic temperature. We also simulated the Earthshine atMWA between November and December 2023 to find suitable observing times less affected by the Earthshine. Such observing windows act as Earthshine avoidance and can be used to perform future global CD-EoR experiments using the Moon with the MWA.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"42 S198","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135342275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 Discs of gas and dust are ubiquitous around protostars. Hypothetical viscous interactions within the disc are thought to cause the gas and dust to accrete onto the star. Turbulence within the disc is theorised to be the source of this disc viscosity. However, observed protostellar disc turbulence often appears to be small and not always conducive to disc accretion. In addition, theories for disc and planet evolution have difficulty in explaining the observed disc rings/gaps which form much earlier than expected. Protostellar accretion discs are observed to contain significant quantities of dust and pebbles. Observations also show that some of this material is ejected from near the protostar, where it travels to the outer regions of the disc. Such solid infalling material has a relatively small amount of angular momentum compared to the material in the disc. This infalling material lowers the angular momentum of the disc and should drive a radial flow towards the protostar. We show that the local radial accretion speed of the disc is proportional to the mass rate of infalling material onto the disc. Higher rates of infall onto the disc implies higher radial accretion disc speeds. As such, regions with high rates of infall of gas, dust, and pebbles onto the disc will produce gaps on relatively short timescales in the disc, while regions associated with relative low rates of infalling material will produce disc rings. As such, the inner edge of a disc gap will tend to have a higher surface density, which may enhance the probability of planet formation. In addition, the outer edge of a disc gap will act as a dust trap and may also become a site for planet formation. For the early Solar System, such a process may have collected O16-poor forsterite dust from the inner regions of the protosolar disc and O16-rich CAIs and AOAs from the inner edge regions of the protosolar disc, thereby constructing a region favourable to the formation of prechondritic planetesimals.
{"title":"Inviscid protostellar disc ring formation and high density ring edges due to the ejection and subsequent infall of material onto a protostellar disc","authors":"Kurt Liffman","doi":"10.1017/pasa.2023.55","DOIUrl":"https://doi.org/10.1017/pasa.2023.55","url":null,"abstract":"Abstract Discs of gas and dust are ubiquitous around protostars. Hypothetical viscous interactions within the disc are thought to cause the gas and dust to accrete onto the star. Turbulence within the disc is theorised to be the source of this disc viscosity. However, observed protostellar disc turbulence often appears to be small and not always conducive to disc accretion. In addition, theories for disc and planet evolution have difficulty in explaining the observed disc rings/gaps which form much earlier than expected. Protostellar accretion discs are observed to contain significant quantities of dust and pebbles. Observations also show that some of this material is ejected from near the protostar, where it travels to the outer regions of the disc. Such solid infalling material has a relatively small amount of angular momentum compared to the material in the disc. This infalling material lowers the angular momentum of the disc and should drive a radial flow towards the protostar. We show that the local radial accretion speed of the disc is proportional to the mass rate of infalling material onto the disc. Higher rates of infall onto the disc implies higher radial accretion disc speeds. As such, regions with high rates of infall of gas, dust, and pebbles onto the disc will produce gaps on relatively short timescales in the disc, while regions associated with relative low rates of infalling material will produce disc rings. As such, the inner edge of a disc gap will tend to have a higher surface density, which may enhance the probability of planet formation. In addition, the outer edge of a disc gap will act as a dust trap and may also become a site for planet formation. For the early Solar System, such a process may have collected O16-poor forsterite dust from the inner regions of the protosolar disc and O16-rich CAIs and AOAs from the inner edge regions of the protosolar disc, thereby constructing a region favourable to the formation of prechondritic planetesimals.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135635347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
A. Mitrašinović, B. Vukotić, M. Micic, M. M. Ćirković
Abstract Recent studies of Galactic evolution revealed that the dynamics of the stellar component might be one of the key factors when considering galactic habitability. We run an N-body simulation model of the Milky Way, which we evolve for 10 Gyr, to study the secular evolution of stellar orbits and the resulting galactic habitability-related properties, i.e., the density of the stellar component and close stellar encounters. The results indicate that radial migrations are not negligible, even in a simple axisymmetric model with mild levels of dynamical heating, and that the net outward diffusion of the stellar component can populate galactic outskirts with habitable systems. Habitable environment is also likely even at sub-Solar galactocentric radii, because the rate of close encounters should not significantly degrade habitability. Stars that evolve from non-circular to stable nearly-circular orbits typically migrate outwards, settling down in a broad Solar neighborhood. The region between R ≈ 3 kpc and R ≈ 12 kpc represents the zone of radial mixing, which can blur the boundaries of the Galactic Habitable Zone, as it has been conventionally understood. The present-day stable population of the stars in the Solar neighborhood originates from this radial mixing zone, with most of the stars coming from the inner regions. The Solar system can be considered as a typical Milky Way habitable system because it migrated outwards from the metal-rich inner regions of the Disk and has a circular orbit in the present epoch. We conclude that the boundaries of the Galactic Habitable Zone cannot be sharply confined for a given epoch because of the mixing caused by the stellar migrations and secular evolution of stellar orbits.
{"title":"Dynamical aspects of Galactic habitability in N-body simulations","authors":"A. Mitrašinović, B. Vukotić, M. Micic, M. M. Ćirković","doi":"10.1017/pasa.2023.54","DOIUrl":"https://doi.org/10.1017/pasa.2023.54","url":null,"abstract":"Abstract Recent studies of Galactic evolution revealed that the dynamics of the stellar component might be one of the key factors when considering galactic habitability. We run an N-body simulation model of the Milky Way, which we evolve for 10 Gyr, to study the secular evolution of stellar orbits and the resulting galactic habitability-related properties, i.e., the density of the stellar component and close stellar encounters. The results indicate that radial migrations are not negligible, even in a simple axisymmetric model with mild levels of dynamical heating, and that the net outward diffusion of the stellar component can populate galactic outskirts with habitable systems. Habitable environment is also likely even at sub-Solar galactocentric radii, because the rate of close encounters should not significantly degrade habitability. Stars that evolve from non-circular to stable nearly-circular orbits typically migrate outwards, settling down in a broad Solar neighborhood. The region between R ≈ 3 kpc and R ≈ 12 kpc represents the zone of radial mixing, which can blur the boundaries of the Galactic Habitable Zone, as it has been conventionally understood. The present-day stable population of the stars in the Solar neighborhood originates from this radial mixing zone, with most of the stars coming from the inner regions. The Solar system can be considered as a typical Milky Way habitable system because it migrated outwards from the metal-rich inner regions of the Disk and has a circular orbit in the present epoch. We conclude that the boundaries of the Galactic Habitable Zone cannot be sharply confined for a given epoch because of the mixing caused by the stellar migrations and secular evolution of stellar orbits.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"2020 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135636955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 Regardless of whether or not all fast radio bursts (FRBs) repeat, those that do form a population with a distribution of rates. This work considers a power-law model of this population, with rate distribution Φ r ∼ R γ r between R min and R max . The zDM code is used to model the probability of detecting this population as either apparently once-off or repeat events as a function of redshift, z , and dispersion measure, DM. I demonstrate that in the nearby Universe, repeating sources can contribute significantly to the total burst rate. This causes an apparent deficit in the total number of observed sources (once-off and repeaters) relative to the distant Universe that will cause a bias in FRB population models. Thus instruments with long exposure times should explicitly take repetition into account when fitting the FRB population. I then fit data from The Canadian Hydrogen Intensity Mapping Experiment (CHIME). The relative number of repeat and apparently once-off FRBs, and their DM, declination, and burst rate distributions, can be well-explained by 50–100% of CHIME single FRBs being due to repeaters, with R max > 0.75 day –1 above 10 39 erg, and This result is surprisingly consistent with follow-up studies of FRBs detected by the Australian Square Kilometre Array Pathfinder (ASKAP). Thus the evidence suggests that CHIME and ASKAP view the same repeating FRB population, which is responsible not just for repeating FRBs, but the majority of apparently once-off bursts. For greater quantitative accuracy, non-Poissonian arrival times, second-order effects in the CHIME response, and a simultaneous fit to the total FRB population parameters, should be treated in more detail in future studies.
不管所有的快速射电暴(frb)是否都会重复，那些重复的射电暴会形成一个具有频率分布的种群。这项工作考虑了这个群体的幂律模型，其速率分布Φ r ~ r γ r在r min和r max之间。zDM代码用于模拟探测到这个群体的概率，作为红移，z和色散测量DM的函数，要么是明显的一次性事件，要么是重复事件。我证明了在附近的宇宙中，重复源可以显著地贡献总爆发率。这导致观测到的源(一次性和重复)的总数相对于遥远的宇宙明显不足，这将导致快速射电暴人口模型的偏差。因此，长曝光时间的仪器在拟合FRB种群时应明确考虑重复。然后，我拟合了加拿大氢强度测绘实验(CHIME)的数据。重复和明显一次性快速射电暴的相对数量，以及它们的DM、衰减和突发率分布，可以很好地解释为50-100%的CHIME单次快速射电暴是由重复器引起的，其中R max >这一结果与澳大利亚平方公里阵列探路者(ASKAP)探测到的快速射电暴的后续研究惊人地一致。因此，证据表明CHIME和ASKAP观测到的是相同的重复FRB群，这不仅是重复FRB的原因，也是大多数明显的一次性爆发的原因。为了获得更高的定量准确性，在未来的研究中应该更详细地处理非泊松到达时间、CHIME响应的二阶效应以及与FRB总体参数的同时拟合。
{"title":"Modelling repetition in zDM: a single population of repeating fast radio bursts can explain CHIME data","authors":"C.W. James","doi":"10.1017/pasa.2023.51","DOIUrl":"https://doi.org/10.1017/pasa.2023.51","url":null,"abstract":"Abstract Regardless of whether or not all fast radio bursts (FRBs) repeat, those that do form a population with a distribution of rates. This work considers a power-law model of this population, with rate distribution Φ r ∼ R γ r between R min and R max . The zDM code is used to model the probability of detecting this population as either apparently once-off or repeat events as a function of redshift, z , and dispersion measure, DM. I demonstrate that in the nearby Universe, repeating sources can contribute significantly to the total burst rate. This causes an apparent deficit in the total number of observed sources (once-off and repeaters) relative to the distant Universe that will cause a bias in FRB population models. Thus instruments with long exposure times should explicitly take repetition into account when fitting the FRB population. I then fit data from The Canadian Hydrogen Intensity Mapping Experiment (CHIME). The relative number of repeat and apparently once-off FRBs, and their DM, declination, and burst rate distributions, can be well-explained by 50–100% of CHIME single FRBs being due to repeaters, with R max > 0.75 day –1 above 10 39 erg, and This result is surprisingly consistent with follow-up studies of FRBs detected by the Australian Square Kilometre Array Pathfinder (ASKAP). Thus the evidence suggests that CHIME and ASKAP view the same repeating FRB population, which is responsible not just for repeating FRBs, but the majority of apparently once-off bursts. For greater quantitative accuracy, non-Poissonian arrival times, second-order effects in the CHIME response, and a simultaneous fit to the total FRB population parameters, should be treated in more detail in future studies.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134908928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Dawei Chen, Vinay Kerai, Matthew J. Alger, O. Ivy Wong, Cheng Soon Ong
Abstract RadioTalk is a communication platform that enabled members of the Radio Galaxy Zoo (RGZ) citizen science project to engage in discussion threads and provide further descriptions of the radio subjects they were observing in the form of tags and comments. It contains a wealth of auxiliary information which is useful for the morphology identification of complex and extended radio sources. In this paper, we present this new dataset, and for the first time in radio astronomy, we combine text and images to automatically classify radio galaxies using a multi-modal learning approach. We found incorporating text features improved classification performance which demonstrates that text annotations are rare but valuable sources of information for classifying astronomical sources, and suggests the importance of exploiting multi-modal information in future citizen science projects. We also discovered over 10,000 new radio sources beyond the RGZ-DR1 catalogue in this dataset.
{"title":"Radio Galaxy Zoo: Tagging Radio Subjects using Text","authors":"Dawei Chen, Vinay Kerai, Matthew J. Alger, O. Ivy Wong, Cheng Soon Ong","doi":"10.1017/pasa.2023.50","DOIUrl":"https://doi.org/10.1017/pasa.2023.50","url":null,"abstract":"Abstract RadioTalk is a communication platform that enabled members of the Radio Galaxy Zoo (RGZ) citizen science project to engage in discussion threads and provide further descriptions of the radio subjects they were observing in the form of tags and comments. It contains a wealth of auxiliary information which is useful for the morphology identification of complex and extended radio sources. In this paper, we present this new dataset, and for the first time in radio astronomy, we combine text and images to automatically classify radio galaxies using a multi-modal learning approach. We found incorporating text features improved classification performance which demonstrates that text annotations are rare but valuable sources of information for classifying astronomical sources, and suggests the importance of exploiting multi-modal information in future citizen science projects. We also discovered over 10,000 new radio sources beyond the RGZ-DR1 catalogue in this dataset.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136113861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
{"title":"The Dawes Review 11: From young to old: The evolutionary path of Pulsar Wind Nebulae – CORRIGENDUM","authors":"B. Olmi, N. Bucciantini","doi":"10.1017/pasa.2023.41","DOIUrl":"https://doi.org/10.1017/pasa.2023.41","url":null,"abstract":"11","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"22 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82534737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
K. Cubuk, M. Burton, C. Braiding, G. Wong, G. Rowell, N. Maxted, D. Eden, R. Z. E. Alsaberi, R. Blackwell, R. Enokiya, K. Feijen, M. Filipović, M. Freeman, S. Fujita, M. Ghavam, B. Gunay, B. Indermuehle, K. Hayashi, M. Kohno, T. Nagaya, A. Nishimura, K. Okawa, D. Rebolledo, D. Romano, H. Sano, C. Snoswell, N. Tothill, K. Tsuge, F. Voisin, Y. Yamane, S. Yoshiike
Abstract We present observations of the Mopra carbon monoxide (CO) survey of the Southern Galactic Plane, covering Galactic longitudes spanning $l = 250^{circ}$ ( $-110^{circ}$ ) to $l = 355^{circ}$ ( $-5^{circ}$ ), with a latitudinal coverage of at least $|b|<1^circ$ , totalling an area of $>$ 210 deg $^{2}$ . These data have been taken at 0.6 arcmin spatial resolution and 0.1 km s $^{-1}$ spectral resolution, providing an unprecedented view of the molecular gas clouds of the Southern Galactic Plane in the 109–115 GHz $J = 1-0$ transitions of $^{12}$ CO, $^{13}$ CO, C $^{18}$ O, and C $^{17}$ O.
{"title":"The Mopra Southern Galactic Plane CO Survey – data release 4– complete survey","authors":"K. Cubuk, M. Burton, C. Braiding, G. Wong, G. Rowell, N. Maxted, D. Eden, R. Z. E. Alsaberi, R. Blackwell, R. Enokiya, K. Feijen, M. Filipović, M. Freeman, S. Fujita, M. Ghavam, B. Gunay, B. Indermuehle, K. Hayashi, M. Kohno, T. Nagaya, A. Nishimura, K. Okawa, D. Rebolledo, D. Romano, H. Sano, C. Snoswell, N. Tothill, K. Tsuge, F. Voisin, Y. Yamane, S. Yoshiike","doi":"10.1017/pasa.2023.44","DOIUrl":"https://doi.org/10.1017/pasa.2023.44","url":null,"abstract":"Abstract We present observations of the Mopra carbon monoxide (CO) survey of the Southern Galactic Plane, covering Galactic longitudes spanning \u0000$l = 250^{circ}$\u0000 ( \u0000$-110^{circ}$\u0000 ) to \u0000$l = 355^{circ}$\u0000 ( \u0000$-5^{circ}$\u0000 ), with a latitudinal coverage of at least \u0000$|b|<1^circ$\u0000 , totalling an area of \u0000$>$\u0000 210 deg \u0000$^{2}$\u0000 . These data have been taken at 0.6 arcmin spatial resolution and 0.1 km s \u0000$^{-1}$\u0000 spectral resolution, providing an unprecedented view of the molecular gas clouds of the Southern Galactic Plane in the 109–115 GHz \u0000$J = 1-0$\u0000 transitions of \u0000$^{12}$\u0000 CO, \u0000$^{13}$\u0000 CO, C \u0000$^{18}$\u0000 O, and C \u0000$^{17}$\u0000 O.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"85 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75917933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 The advent of time-domain sky surveys has generated a vast amount of light variation data, enabling astronomers to investigate variable stars with large-scale samples. However, this also poses new opportunities and challenges for the time-domain research. In this paper, we focus on the classification of variable stars from the Catalina Surveys Data Release 2 and propose an imbalanced learning classifier based on Self-paced Ensemble (SPE) method. Compared with the work of Hosenie et al. (2020), our approach significantly enhances the classification Recall of Blazhko RR Lyrae stars from 12% to 85%, mixed-mode RR Lyrae variables from 29% to 64%, detached binaries from 68% to 97%, and LPV from 87% to 99%. SPE demonstrates a rather good performance on most of the variable classes except RRab, RRc, and contact and semi-detached binary. Moreover, the results suggest that SPE tends to target the minority classes of objects, while Random Forest is more effective in finding the majority classes. To balance the overall classification accuracy, we construct a Voting Classifier that combines the strengths of SPE and Random Forest. The results show that the Voting Classifier can achieve a balanced performance across all classes with minimal loss of accuracy. In summary, the SPE algorithm and Voting Classifier are superior to traditional machine learning methods and can be well applied to classify the periodic variable stars. This paper contributes to the current research on imbalanced learning in astronomy and can also be extended to the time-domain data of other larger sky survey projects (LSST, etc.).
时域巡天的出现产生了大量的光变化数据，使天文学家能够用大尺度的样本来研究变星。然而，这也给时域研究带来了新的机遇和挑战。本文以Catalina survey Data Release 2中的变星分类为研究对象，提出了一种基于自同步集成(self -pace Ensemble, SPE)方法的不平衡学习分类器。与Hosenie et al.(2020)的工作相比，我们的方法显著提高了Blazhko RR Lyrae恒星的分类召回率，从12%提高到85%，混合模式RR Lyrae变量从29%提高到64%，分离双星从68%提高到97%，LPV从87%提高到99%。SPE在除RRab、RRc以及接触和半分离二进制之外的大多数变量类上都表现出相当好的性能。此外，结果表明SPE倾向于针对对象的少数类，而随机森林在寻找多数类方面更有效。为了平衡整体分类精度，我们构建了一个结合SPE和随机森林优势的投票分类器。结果表明，投票分类器可以在最小的准确性损失的情况下实现所有类的平衡性能。综上所述，SPE算法和投票分类器优于传统的机器学习方法，可以很好地应用于周期变星的分类。本文对当前天文学中不平衡学习的研究有一定的贡献，也可以推广到其他大型巡天项目(LSST等)的时域数据。
{"title":"A novel approach for variable star classification based on imbalanced learning","authors":"Jingyi Zhang, Yanxia Zhang, Zihan Kang, Changhua Li, Yihan Tao, Yongheng Zhao, Xue-bing Wu","doi":"10.1017/pasa.2023.35","DOIUrl":"https://doi.org/10.1017/pasa.2023.35","url":null,"abstract":"Abstract The advent of time-domain sky surveys has generated a vast amount of light variation data, enabling astronomers to investigate variable stars with large-scale samples. However, this also poses new opportunities and challenges for the time-domain research. In this paper, we focus on the classification of variable stars from the Catalina Surveys Data Release 2 and propose an imbalanced learning classifier based on Self-paced Ensemble (SPE) method. Compared with the work of Hosenie et al. (2020), our approach significantly enhances the classification Recall of Blazhko RR Lyrae stars from 12% to 85%, mixed-mode RR Lyrae variables from 29% to 64%, detached binaries from 68% to 97%, and LPV from 87% to 99%. SPE demonstrates a rather good performance on most of the variable classes except RRab, RRc, and contact and semi-detached binary. Moreover, the results suggest that SPE tends to target the minority classes of objects, while Random Forest is more effective in finding the majority classes. To balance the overall classification accuracy, we construct a Voting Classifier that combines the strengths of SPE and Random Forest. The results show that the Voting Classifier can achieve a balanced performance across all classes with minimal loss of accuracy. In summary, the SPE algorithm and Voting Classifier are superior to traditional machine learning methods and can be well applied to classify the periodic variable stars. This paper contributes to the current research on imbalanced learning in astronomy and can also be extended to the time-domain data of other larger sky survey projects (LSST, etc.).","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"9 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75239898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Georgia R. Hartzenberg, M. Cowley, A. Hopkins, R. Allen
Abstract To explore the role environment plays in influencing galaxy evolution at high redshifts, we study $2.0leq z<4.2$ environments using the FourStar Galaxy Evolution (ZFOURGE) survey. Using galaxies from the COSMOS legacy field with ${rm log(M_{*}/M_{odot})}geq9.5$ , we use a seventh nearest neighbour density estimator to quantify galaxy environment, dividing this into bins of low-, intermediate-, and high-density. We discover new high-density environment candidates across $2.0leq z<2.4$ and $3.1leq z<4.2$ . We analyse the quiescent fraction, stellar mass and specific star formation rate (sSFR) of our galaxies to understand how these vary with redshift and environment. Our results reveal that, across $2.0leq z<2.4$ , the high-density environments are the most significant regions, which consist of elevated quiescent fractions, ${rm log(M_{*}/M_{odot})}geq10.2$ massive galaxies and suppressed star formation activity. At $3.1leq z<4.2$ , we find that high-density regions consist of elevated stellar masses but require more complete samples of quiescent and sSFR data to study the effects of environment in more detail at these higher redshifts. Overall, our results suggest that well-evolved, passive galaxies are already in place in high-density environments at $zsim2.4$ , and that the Butcher–Oemler effect and SFR-density relation may not reverse towards higher redshifts as previously thought.
{"title":"Evolved galaxies in high-density environments across 2.0 ≤ z < 4.2 using the ZFOURGE survey","authors":"Georgia R. Hartzenberg, M. Cowley, A. Hopkins, R. Allen","doi":"10.1017/pasa.2023.42","DOIUrl":"https://doi.org/10.1017/pasa.2023.42","url":null,"abstract":"Abstract To explore the role environment plays in influencing galaxy evolution at high redshifts, we study \u0000$2.0leq z<4.2$\u0000 environments using the FourStar Galaxy Evolution (ZFOURGE) survey. Using galaxies from the COSMOS legacy field with \u0000${rm log(M_{*}/M_{odot})}geq9.5$\u0000 , we use a seventh nearest neighbour density estimator to quantify galaxy environment, dividing this into bins of low-, intermediate-, and high-density. We discover new high-density environment candidates across \u0000$2.0leq z<2.4$\u0000 and \u0000$3.1leq z<4.2$\u0000 . We analyse the quiescent fraction, stellar mass and specific star formation rate (sSFR) of our galaxies to understand how these vary with redshift and environment. Our results reveal that, across \u0000$2.0leq z<2.4$\u0000 , the high-density environments are the most significant regions, which consist of elevated quiescent fractions, \u0000${rm log(M_{*}/M_{odot})}geq10.2$\u0000 massive galaxies and suppressed star formation activity. At \u0000$3.1leq z<4.2$\u0000 , we find that high-density regions consist of elevated stellar masses but require more complete samples of quiescent and sSFR data to study the effects of environment in more detail at these higher redshifts. Overall, our results suggest that well-evolved, passive galaxies are already in place in high-density environments at \u0000$zsim2.4$\u0000 , and that the Butcher–Oemler effect and SFR-density relation may not reverse towards higher redshifts as previously thought.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"71 1 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73016809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 Asymmetric emission of gravitational waves during mergers of black holes (BHs) produces a recoil kick, which can set a newly formed BH on a bound orbit around the centre of its host galaxy, or even completely eject it. To study this population of recoiling BHs we extract properties of galaxies with merging BHs from Illustris TNG300 simulation and then employ both analytical and numerical techniques to model unresolved process of BH recoil. This comparative analysis between analytical and numerical models shows that, on cosmological scales, numerically modelled recoiling BHs have a higher escape probability and predict a greater number of offset active galactic nuclei (AGN). BH escaped probability $>$ 40% is expected in 25 $%$ of merger remnants in numerical models, compared to 8 $%$ in analytical models. At the same time, the predicted number of offset AGN at separations ${>}5$ kpc changes from 58 $%$ for numerical models to 3 $%$ for analytical models. Since BH ejections in major merger remnants occur in non-virialised systems, static analytical models cannot provide an accurate description. Thus we argue that numerical models should be used to estimate the expected number density of escaped BHs and offset AGN.
{"title":"Statistical analysis of kicked black holes from TNG300 simulation","authors":"M. Smole, M. Micic","doi":"10.1017/pasa.2023.45","DOIUrl":"https://doi.org/10.1017/pasa.2023.45","url":null,"abstract":"Abstract Asymmetric emission of gravitational waves during mergers of black holes (BHs) produces a recoil kick, which can set a newly formed BH on a bound orbit around the centre of its host galaxy, or even completely eject it. To study this population of recoiling BHs we extract properties of galaxies with merging BHs from Illustris TNG300 simulation and then employ both analytical and numerical techniques to model unresolved process of BH recoil. This comparative analysis between analytical and numerical models shows that, on cosmological scales, numerically modelled recoiling BHs have a higher escape probability and predict a greater number of offset active galactic nuclei (AGN). BH escaped probability \u0000$>$\u0000 40% is expected in 25 \u0000$%$\u0000 of merger remnants in numerical models, compared to 8 \u0000$%$\u0000 in analytical models. At the same time, the predicted number of offset AGN at separations \u0000${>}5$\u0000 kpc changes from 58 \u0000$%$\u0000 for numerical models to 3 \u0000$%$\u0000 for analytical models. Since BH ejections in major merger remnants occur in non-virialised systems, static analytical models cannot provide an accurate description. Thus we argue that numerical models should be used to estimate the expected number density of escaped BHs and offset AGN.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"1 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89659003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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