Publications of the Astronomical Society of Australia最新文献_第6页

Measuring the global 21-cm signal with the MWA-II: improved characterisation of lunar-reflected radio frequency interference 用MWA-II测量全球21厘米信号:改进月球反射射频干扰的特性

3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-11-08 DOI: 10.1017/pasa.2023.57

Himanshu Tiwari, Benjamin McKinley, Cathryn M. Trott, Nithyanandan Thyagarajan

{"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}

引用次数: 0

Inviscid protostellar disc ring formation and high density ring edges due to the ejection and subsequent infall of material onto a protostellar disc 无粘性原恒星盘环的形成和高密度环的边缘，这是由于物质的喷射和随后落入原恒星盘

3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-11-06 DOI: 10.1017/pasa.2023.55

Kurt Liffman

{"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}

引用次数: 0

Dynamical aspects of Galactic habitability in N-body simulations n体模拟中银河系可居住性的动力学方面

3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-11-06 DOI: 10.1017/pasa.2023.54

A. Mitrašinović, B. Vukotić, M. Micic, M. M. Ćirković

{"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}

引用次数: 0

Modelling repetition in zDM: a single population of repeating fast radio bursts can explain CHIME data zDM中的重复建模:一个重复的快速射电暴的单一种群可以解释CHIME数据

3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-10-26 DOI: 10.1017/pasa.2023.51

C.W. James

{"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}

引用次数: 0

Radio Galaxy Zoo: Tagging Radio Subjects using Text 无线电银河动物园:使用文本标记无线电主题

3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-10-16 DOI: 10.1017/pasa.2023.50

Dawei Chen, Vinay Kerai, Matthew J. Alger, O. Ivy Wong, Cheng Soon Ong

引用次数: 0

The Dawes Review 11: From young to old: The evolutionary path of Pulsar Wind Nebulae – CORRIGENDUM 道斯评论11:从年轻到年老:脉冲星风星云的演化路径-勘误表

IF 6.3 3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-08-31 DOI: 10.1017/pasa.2023.41

B. Olmi, N. Bucciantini

引用次数: 0

The Mopra Southern Galactic Plane CO Survey – data release 4– complete survey 莫普拉南银河面CO测量-数据发布4 -完整的测量

IF 6.3 3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-08-22 DOI: 10.1017/pasa.2023.44

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

引用次数: 0

A novel approach for variable star classification based on imbalanced learning 一种基于不平衡学习的变星分类新方法

IF 6.3 3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-08-09 DOI: 10.1017/pasa.2023.35

Jingyi Zhang, Yanxia Zhang, Zihan Kang, Changhua Li, Yihan Tao, Yongheng Zhao, Xue-bing Wu

{"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}

引用次数: 0

Evolved galaxies in high-density environments across 2.0 ≤ z < 4.2 using the ZFOURGE survey 通过ZFOURGE调查，在2.0≤z < 4.2的高密度环境中进化的星系

IF 6.3 3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-08-09 DOI: 10.1017/pasa.2023.42

Georgia R. Hartzenberg, M. Cowley, A. Hopkins, R. Allen

{"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}

引用次数: 0

Statistical analysis of kicked black holes from TNG300 simulation TNG300模拟中被踢黑洞的统计分析

IF 6.3 3区物理与天体物理

Publications of the Astronomical Society of Australia Pub Date : 2023-08-09 DOI: 10.1017/pasa.2023.45

M. Smole, M. Micic

{"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}

引用次数: 0