Pub Date : 2024-08-08DOI: 10.3390/galaxies12040047
P. Soffitta, E. Costa, Nicolas De Angelis, E. Del Monte, K. Desch, A. Di Marco, G. Di Persio, S. Fabiani, R. Ferrazzoli, Markus Gruber, Takahashi Hiromitsu, Saba Imtiaz, P. Kaaret, Jochen Kaminski, Dawoon E. Kim, F. Kislat, H. Krawczynski, F. La Monaca, Carlo Lefevre, Hemanth Manikantan, H. Marshall, R. Mikus̆incová, A. Morbidini, F. Muleri, S. O’Dell, T. Okajima, M. Pearce, Vladislavs Plesanovs, B. Ramsey, A. Ratheesh, A. Rubini, Shravan Vengalil Menon, M. Weisskopf
The Imaging X-ray Polarimetry Explorer (IXPE) has confirmed that X-ray polarimetry is a valuable tool in astronomy, providing critical insights into the emission processes and the geometry of compact objects. IXPE was designed to be sensitive in the 2–8 keV energy range for three primary reasons: (1) celestial X-ray sources are bright within this range, (2) the optics are effective, and (3) most sources across various classes were expected to exhibit some level of polarization. Indeed, IXPE is a great success, and its discoveries are necessitating the revision of many theoretical models for numerous sources. However, one of IXPE’s main limitations is its relatively narrow energy band, coupled with rapidly declining efficiency. In this paper, we will demonstrate the benefits of devising a mission focused on a broader energy band (0.1–79 keV). This approach leverages current technologies that align well with theoretical expectations and builds on the successes of IXPE.
成像 X 射线偏振探测仪（IXPE）证实，X 射线偏振探测仪是天文学中的一种宝贵工具，可提供有关发射过程和紧凑天体几何形状的重要见解。IXPE 被设计为在 2-8 keV 能量范围内具有灵敏度，主要有三个原因：(1) 天体 X 射线源在此范围内非常明亮，(2) 光学系统非常有效，(3) 不同类别的大多数源预计都会表现出一定程度的偏振。事实上，IXPE 是一个巨大的成功，它的发现使得许多理论模型必须对众多来源进行修正。然而，IXPE 的主要局限性之一是能带相对较窄，而且效率迅速下降。在本文中，我们将展示设计一个侧重于更宽能段（0.1-79 keV）的任务的好处。这种方法利用了与理论预期完全一致的现有技术，并以 IXPE 的成功为基础。
{"title":"Considerations on Possible Directions for a Wide Band Polarimetry X-ray Mission","authors":"P. Soffitta, E. Costa, Nicolas De Angelis, E. Del Monte, K. Desch, A. Di Marco, G. Di Persio, S. Fabiani, R. Ferrazzoli, Markus Gruber, Takahashi Hiromitsu, Saba Imtiaz, P. Kaaret, Jochen Kaminski, Dawoon E. Kim, F. Kislat, H. Krawczynski, F. La Monaca, Carlo Lefevre, Hemanth Manikantan, H. Marshall, R. Mikus̆incová, A. Morbidini, F. Muleri, S. O’Dell, T. Okajima, M. Pearce, Vladislavs Plesanovs, B. Ramsey, A. Ratheesh, A. Rubini, Shravan Vengalil Menon, M. Weisskopf","doi":"10.3390/galaxies12040047","DOIUrl":"https://doi.org/10.3390/galaxies12040047","url":null,"abstract":"The Imaging X-ray Polarimetry Explorer (IXPE) has confirmed that X-ray polarimetry is a valuable tool in astronomy, providing critical insights into the emission processes and the geometry of compact objects. IXPE was designed to be sensitive in the 2–8 keV energy range for three primary reasons: (1) celestial X-ray sources are bright within this range, (2) the optics are effective, and (3) most sources across various classes were expected to exhibit some level of polarization. Indeed, IXPE is a great success, and its discoveries are necessitating the revision of many theoretical models for numerous sources. However, one of IXPE’s main limitations is its relatively narrow energy band, coupled with rapidly declining efficiency. In this paper, we will demonstrate the benefits of devising a mission focused on a broader energy band (0.1–79 keV). This approach leverages current technologies that align well with theoretical expectations and builds on the successes of IXPE.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141926818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-18DOI: 10.3390/galaxies12040040
Michael Bowler
Flaring in the SS 433 microquasar is dominated by outbursts from material at distances from the centre of mass of the binary system comparable to the separation of the two components. This note completes a demonstration that ejected plasma leaves the system in the region of the L2 point, there overflowing the outer Roche lobe and giving rise to a spiral structure as it leaves the system as part of the local environment. It also provides a new measure of the mass ratio of the binary.
SS 433 微类星体的耀斑主要是来自距离双星系统质量中心的物质的爆发，其距离相当于两个组成部分的分离距离。本说明完成了一项论证，即喷出的等离子体在 L2 点区域离开系统，溢出外罗氏叶，并在离开系统时形成螺旋结构，成为当地环境的一部分。它还提供了双星质量比的新测量方法。
{"title":"SS 433: Flares and L2 Overflow Spirals","authors":"Michael Bowler","doi":"10.3390/galaxies12040040","DOIUrl":"https://doi.org/10.3390/galaxies12040040","url":null,"abstract":"Flaring in the SS 433 microquasar is dominated by outbursts from material at distances from the centre of mass of the binary system comparable to the separation of the two components. This note completes a demonstration that ejected plasma leaves the system in the region of the L2 point, there overflowing the outer Roche lobe and giving rise to a spiral structure as it leaves the system as part of the local environment. It also provides a new measure of the mass ratio of the binary.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141825154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-17DOI: 10.3390/galaxies12040039
Sun Kwok
We review the evolution of our understanding of the planetary nebulae phenomenon and their place in the scheme of stellar evolution. The historical steps leading to our current understanding of central star evolution and nebular formation are discussed. Recent optical imaging, X-ray, ultraviolet, infrared, millimeter wave, and radio observations have led to a much more complex picture of the structure of planetary nebulae. The optically bright regions have multiple shell structures (rims, shells, crowns, and haloes), which can be understood within the interacting winds framework. However, the physical mechanism responsible for bipolar and multipolar structures that emerged during the proto-planetary nebulae phase is yet to be identified. Our morphological classifications of planetary nebulae are hampered by the effects of sensitivity, orientation, and field-of-view coverage, and the fraction of bipolar or multipolar nebulae may be much higher than commonly assumed. The optically bright bipolar lobes may represent low-density, ionization-bounded cavities carved out of a neutral envelope by collimated fast winds. Planetary nebulae are sites of active synthesis of complex organic compounds, suggesting that planetary nebulae play a major role in the chemical enrichment of the Galaxy. Possible avenues of future advancement are discussed.
{"title":"Planetary Nebulae Research: Past, Present, and Future","authors":"Sun Kwok","doi":"10.3390/galaxies12040039","DOIUrl":"https://doi.org/10.3390/galaxies12040039","url":null,"abstract":"We review the evolution of our understanding of the planetary nebulae phenomenon and their place in the scheme of stellar evolution. The historical steps leading to our current understanding of central star evolution and nebular formation are discussed. Recent optical imaging, X-ray, ultraviolet, infrared, millimeter wave, and radio observations have led to a much more complex picture of the structure of planetary nebulae. The optically bright regions have multiple shell structures (rims, shells, crowns, and haloes), which can be understood within the interacting winds framework. However, the physical mechanism responsible for bipolar and multipolar structures that emerged during the proto-planetary nebulae phase is yet to be identified. Our morphological classifications of planetary nebulae are hampered by the effects of sensitivity, orientation, and field-of-view coverage, and the fraction of bipolar or multipolar nebulae may be much higher than commonly assumed. The optically bright bipolar lobes may represent low-density, ionization-bounded cavities carved out of a neutral envelope by collimated fast winds. Planetary nebulae are sites of active synthesis of complex organic compounds, suggesting that planetary nebulae play a major role in the chemical enrichment of the Galaxy. Possible avenues of future advancement are discussed.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141828411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-16DOI: 10.3390/galaxies12040038
M. Weisskopf, B. Ramsey
Drs. Weisskopf and Ramsey were the original Principal and Deputy Principal Investigators of the Imaging X-ray Polarimetry Explorer (IXPE). They outline the path to the development of IXPE and discuss the technical and programmatic history that led up to the mission, a partnership between the Italian Space Agency and NASA, and the first fully dedicated to imaging X-ray polarimetry in the 2–8 keV band. An admittedly biased, as seen through the eyes of the original and Deputy Principal Investigators, technical overview of the development of the historical and critical scientific instrumentation is provided. The outstanding, and often paradigm-shifting results are presented in the papers following this one.
Weisskopf 博士和 Ramsey 博士是成像 X 射线偏振探测仪（IXPE）最初的首席和副首席研究员。他们概述了 IXPE 的发展之路，并讨论了促成这项任务的技术和计划历史。IXPE 是意大利航天局和美国国家航空航天局（NASA）的合作项目，也是首个完全致力于 2-8 keV 波段成像 X 射线偏振测量的项目。通过原首席研究员和副首席研究员的视角，对具有历史意义的关键科学仪器的发展历程进行了技术概述，这无疑有失偏颇。在本论文之后的论文中将介绍杰出的、往往是改变范式的成果。
{"title":"On the Making of IXPE","authors":"M. Weisskopf, B. Ramsey","doi":"10.3390/galaxies12040038","DOIUrl":"https://doi.org/10.3390/galaxies12040038","url":null,"abstract":"Drs. Weisskopf and Ramsey were the original Principal and Deputy Principal Investigators of the Imaging X-ray Polarimetry Explorer (IXPE). They outline the path to the development of IXPE and discuss the technical and programmatic history that led up to the mission, a partnership between the Italian Space Agency and NASA, and the first fully dedicated to imaging X-ray polarimetry in the 2–8 keV band. An admittedly biased, as seen through the eyes of the original and Deputy Principal Investigators, technical overview of the development of the historical and critical scientific instrumentation is provided. The outstanding, and often paradigm-shifting results are presented in the papers following this one.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141640691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-08DOI: 10.3390/galaxies12040037
M. Bonato, I. Baronchelli, Viviana Casasola, G. De Zotti, Leonardo Trobbiani, E. Ruli, Vidhi Tailor, Simone Bianchi
We exploit the DustPedia sample of galaxies within approximately 40 Mpc, selecting 388 sources, to investigate the correlations between IR luminosity (LIR), the star formation rate (SFR), and the CO(1-0) luminosity (LCO) down to much lower luminosities than reached by previous analyses. We find a sub-linear dependence of the SFR on LIR. Below log(LIR/L⊙)≃10 or SFR≃1M⊙yr−1, the SFR/LIR ratio substantially exceeds the standard ratio for dust-enshrouded star formation, and the difference increases with decreasing LIR values. This implies that the effect of unobscured star formation overcomes that of dust heating by old stars, at variance with results based on the Planck ERCSC galaxy sample. We also find that the relations between the LCO and LIR or the SFR are consistent with those obtained at much higher luminosities.
{"title":"Correlations between IR Luminosity, Star Formation Rate, and CO Luminosity in the Local Universe","authors":"M. Bonato, I. Baronchelli, Viviana Casasola, G. De Zotti, Leonardo Trobbiani, E. Ruli, Vidhi Tailor, Simone Bianchi","doi":"10.3390/galaxies12040037","DOIUrl":"https://doi.org/10.3390/galaxies12040037","url":null,"abstract":"We exploit the DustPedia sample of galaxies within approximately 40 Mpc, selecting 388 sources, to investigate the correlations between IR luminosity (LIR), the star formation rate (SFR), and the CO(1-0) luminosity (LCO) down to much lower luminosities than reached by previous analyses. We find a sub-linear dependence of the SFR on LIR. Below log(LIR/L⊙)≃10 or SFR≃1M⊙yr−1, the SFR/LIR ratio substantially exceeds the standard ratio for dust-enshrouded star formation, and the difference increases with decreasing LIR values. This implies that the effect of unobscured star formation overcomes that of dust heating by old stars, at variance with results based on the Planck ERCSC galaxy sample. We also find that the relations between the LCO and LIR or the SFR are consistent with those obtained at much higher luminosities.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141667897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.3390/galaxies12040035
F. Marin, V. Gianolli, A. Ingram, Dawoon E. Kim, A. Marinucci, D. Tagliacozzo, F. Ursini
Active galactic nuclei (AGNs), either radio-quiet or radio-loud, had never been observed in X-ray polarized light until the advent of the Imaging X-ray Polarimetry Explorer (IXPE) in the end of 2021. This satellite opened a new observational window for studying supermassive black holes and their complex environment. In this regard, radio-quiet AGNs are probably better targets than radio-loud objects to probe accretion processes due to the lack of synchrotron emission from jets that can dilute the polarized signal from the central engine. Their relatively clean environment not only allows to detect and measure the X-ray polarization originating from the hot corona responsible for X-ray emission, but also to assess the geometry of the media immediately surrounding the supermassive black hole. Such geometrical measurements work just as well for characterizing the corona morphology in pole-on AGNs as it does for determining the three-dimensional shape of the circumnuclear cold obscurer (the so-called torus) in edge-on AGNs. In this review paper, we will return to each of the observations made by IXPE so far in the field of radio-quiet AGNs and highlight the fundamental contribution of X-ray polarimetry to our understanding of how light is emitted and how matter is shaped around supermassive black holes.
在成像 X 射线偏振探测卫星（IXPE）于 2021 年底问世之前，人们从未用 X 射线偏振光观测过射电安静或射电响亮的活动星系核（AGN）。这颗卫星为研究超大质量黑洞及其复杂环境打开了一扇新的观测窗口。在这方面，射电安静的AGN可能是比射电响亮的天体更好的探测吸积过程的目标，因为它们缺乏喷流的同步辐射，而喷流会稀释来自中央引擎的偏振信号。它们的环境相对干净，不仅可以探测和测量来自热日冕的 X 射线偏振，还可以评估紧靠超大质量黑洞周围介质的几何形状。这种几何测量方法既可用于描述极上 AGN 的日冕形态，也可用于确定边缘 AGN 的环核冷遮挡物（即所谓的环状物）的三维形状。在这篇综述论文中，我们将回顾 IXPE 迄今在射电静止 AGN 领域进行的每一次观测，并强调 X 射线偏振测量法对我们了解光是如何发射的以及超大质量黑洞周围物质是如何形成的这一基本贡献。
{"title":"An Examination of the Very First Polarimetric X-ray Observations of Radio-Quiet Active Galactic Nuclei","authors":"F. Marin, V. Gianolli, A. Ingram, Dawoon E. Kim, A. Marinucci, D. Tagliacozzo, F. Ursini","doi":"10.3390/galaxies12040035","DOIUrl":"https://doi.org/10.3390/galaxies12040035","url":null,"abstract":"Active galactic nuclei (AGNs), either radio-quiet or radio-loud, had never been observed in X-ray polarized light until the advent of the Imaging X-ray Polarimetry Explorer (IXPE) in the end of 2021. This satellite opened a new observational window for studying supermassive black holes and their complex environment. In this regard, radio-quiet AGNs are probably better targets than radio-loud objects to probe accretion processes due to the lack of synchrotron emission from jets that can dilute the polarized signal from the central engine. Their relatively clean environment not only allows to detect and measure the X-ray polarization originating from the hot corona responsible for X-ray emission, but also to assess the geometry of the media immediately surrounding the supermassive black hole. Such geometrical measurements work just as well for characterizing the corona morphology in pole-on AGNs as it does for determining the three-dimensional shape of the circumnuclear cold obscurer (the so-called torus) in edge-on AGNs. In this review paper, we will return to each of the observations made by IXPE so far in the field of radio-quiet AGNs and highlight the fundamental contribution of X-ray polarimetry to our understanding of how light is emitted and how matter is shaped around supermassive black holes.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141686978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-06DOI: 10.3390/galaxies12030028
H. Pérez-de-Tejada
Dissipation processes derived from the kinetic theory of gases (shear viscosity and heat conduction) are employed to examine the solar wind that interacts with planetary ionospheres. The purpose of this study is to estimate the mean free path of wave-particle interactions that produce a continuum response in the plasma behavior. Wave-particle interactions are necessary to support the fluid dynamic interpretation that accounts for the interpretation of various features measured in a solar wind–planet ionosphere region; namely, (i) the transport of solar wind momentum to an upper ionosphere in the presence of a velocity shear, and (ii) plasma heating produced by momentum transport. From measurements conducted in the solar wind interaction with the Venus ionosphere, it is possible to estimate that in general terms, the mean free path of wave-particle interactions reaches λH ≥ 1000 km values that are comparable to the gyration radius of the solar wind particles in their Larmor motion within the local solar wind magnetic field. Similar values are also applicable to conditions measured by the Mars ionosphere and in cometary plasma wakes. Considerations are made in regard to the stochastic trajectories of the plasma particles that have been implied from the measurements made in planetary environments. At the same time, it is as possible that the same phenomenon is applicable to the interaction of stellar winds with the ionosphere of exoplanets, and also in regions where streaming ionized gases reach objects that are subject to rotational motion in other astrophysical problems (galactic flow–plasma interactions, black holes, etc.).
{"title":"Wave-Particle Interactions in Astrophysical Plasmas","authors":"H. Pérez-de-Tejada","doi":"10.3390/galaxies12030028","DOIUrl":"https://doi.org/10.3390/galaxies12030028","url":null,"abstract":"Dissipation processes derived from the kinetic theory of gases (shear viscosity and heat conduction) are employed to examine the solar wind that interacts with planetary ionospheres. The purpose of this study is to estimate the mean free path of wave-particle interactions that produce a continuum response in the plasma behavior. Wave-particle interactions are necessary to support the fluid dynamic interpretation that accounts for the interpretation of various features measured in a solar wind–planet ionosphere region; namely, (i) the transport of solar wind momentum to an upper ionosphere in the presence of a velocity shear, and (ii) plasma heating produced by momentum transport. From measurements conducted in the solar wind interaction with the Venus ionosphere, it is possible to estimate that in general terms, the mean free path of wave-particle interactions reaches λH ≥ 1000 km values that are comparable to the gyration radius of the solar wind particles in their Larmor motion within the local solar wind magnetic field. Similar values are also applicable to conditions measured by the Mars ionosphere and in cometary plasma wakes. Considerations are made in regard to the stochastic trajectories of the plasma particles that have been implied from the measurements made in planetary environments. At the same time, it is as possible that the same phenomenon is applicable to the interaction of stellar winds with the ionosphere of exoplanets, and also in regions where streaming ionized gases reach objects that are subject to rotational motion in other astrophysical problems (galactic flow–plasma interactions, black holes, etc.).","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141378700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-20DOI: 10.3390/galaxies12030026
I. Baronchelli, M. Bonato, G. De Zotti, Viviana Casasola, Michele Delli Veneri, Fabrizia Guglielmetti, E. Liuzzo, Rosita Paladino, Leonardo Trobbiani, Martin Zwaan
We performed differential number counts down to 4.25 sigma using ALMA Band 3 calibrator images, which are known for their high dynamic range and susceptibility to various types of contamination. Estimating the fraction of contaminants is an intricate process due to correlated non-Gaussian noise, and it is often compounded by the presence of false positives generated during the cleaning phase. In addition, calibrator extensions further complicate the counting of background sources. In order to address these challenges, our strategy employs a machine learning-based approach utilizing the UMLAUT algorithm. UMLAUT assigns a value to each detection, and it considers how likely it is for there to be a genuine background source or a contaminant. With respect to this goal, we provide UMLAUT with eight observational input parameters, each automatically weighted using a gradient descent method. Our methodology significantly improves the precision of differential number counts, thus surpassing conventional techniques, including visual inspection. This study contributes to a better understanding of radio sources, particularly in the challenging sub-5 sigma regime, within the complex context of a high dynamic range of ALMA calibrator images.
我们使用 ALMA 波段 3 校准图像进行了低至 4.25 sigma 的差分数字计数，众所周知，这些图像的动态范围很高，而且容易受到各种类型的污染。由于相关的非高斯噪声，估算污染物的比例是一个复杂的过程，而在清洁阶段产生的假阳性往往会使这一过程变得更加复杂。此外，校准器的扩展也使背景源的计数变得更加复杂。为了应对这些挑战，我们的策略采用了基于机器学习的 UMLAUT 算法。UMLAUT 会为每次检测分配一个值，并考虑存在真正背景源或污染物的可能性有多大。为此，我们为 UMLAUT 提供了八个观测输入参数，每个参数都使用梯度下降法自动加权。我们的方法大大提高了差分数字计数的精度，从而超越了包括目测在内的传统技术。这项研究有助于在高动态范围的 ALMA 校准图像的复杂背景下更好地了解射电源，尤其是具有挑战性的 5 sigma 以下的射电源。
{"title":"ALMA Band 3 Source Counts: A Machine Learning Approach to Contamination Mitigation below 5 Sigma","authors":"I. Baronchelli, M. Bonato, G. De Zotti, Viviana Casasola, Michele Delli Veneri, Fabrizia Guglielmetti, E. Liuzzo, Rosita Paladino, Leonardo Trobbiani, Martin Zwaan","doi":"10.3390/galaxies12030026","DOIUrl":"https://doi.org/10.3390/galaxies12030026","url":null,"abstract":"We performed differential number counts down to 4.25 sigma using ALMA Band 3 calibrator images, which are known for their high dynamic range and susceptibility to various types of contamination. Estimating the fraction of contaminants is an intricate process due to correlated non-Gaussian noise, and it is often compounded by the presence of false positives generated during the cleaning phase. In addition, calibrator extensions further complicate the counting of background sources. In order to address these challenges, our strategy employs a machine learning-based approach utilizing the UMLAUT algorithm. UMLAUT assigns a value to each detection, and it considers how likely it is for there to be a genuine background source or a contaminant. With respect to this goal, we provide UMLAUT with eight observational input parameters, each automatically weighted using a gradient descent method. Our methodology significantly improves the precision of differential number counts, thus surpassing conventional techniques, including visual inspection. This study contributes to a better understanding of radio sources, particularly in the challenging sub-5 sigma regime, within the complex context of a high dynamic range of ALMA calibrator images.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141119086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-15DOI: 10.3390/galaxies12030025
Y. Sotnikova, Alexander Mikhailov, T. Mufakharov, Tao An, Dmitry Kudryavtsev, M. Mingaliev, R. Udovitskiy, Anastasia Kudryashova, Vladislav Stolyarov, Tamara Semenova
We present a study of the radio variability of bright, S1.4≥100 mJy, high-redshift quasars at z≥3 on timescales of up to 30–40 yrs. The study involved simultaneous RATAN-600 measurements at the frequencies of 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2017–2020. In addition, data from the literature were used. We have found that the variability index, VS, which quantifies the normalized difference between the maximum and minimum flux density while accounting for measurement uncertainties, ranges from 0.02 to 0.96 for the quasars. Approximately half of the objects in the sample exhibit a variability index within the range from 0.25 to 0.50, which is comparable to that observed in blazars at lower redshifts. The distribution of VS at 22.3 GHz is significantly different from that at 2.3–11.2 GHz, which may be attributed to the fact that a compact AGN core dominates at the source’s rest frame frequencies greater than 45 GHz, leading to higher variability indices obtained at 22.3 GHz (the VS distribution peaks around 0.4) compared to the lower frequencies (the VS distribution at 2.3 and 4.7 GHz peaks around 0.1–0.2). Several source groups with distinctive variability characteristics were found using the cluster analysis of quasars. We propose seven new candidates for gigahertz-peaked spectrum (GPS) sources and five new megahertz-peaked spectrum (MPS) sources based on their spectrum shape and variability features. Only 6 out of the 23 sources previously reported as GPS demonstrate a low variability level typical of classical GPS sources (VS<0.25) at 4.7–22.3 GHz. When excluding the highly variable peaked-spectrum blazars, we expect no more than 20% of the sources in the sample to be GPS candidates and no more than 10% to be MPS candidates.
{"title":"High-Redshift Quasars at z≥3: Radio Variability and MPS/GPS Candidates","authors":"Y. Sotnikova, Alexander Mikhailov, T. Mufakharov, Tao An, Dmitry Kudryavtsev, M. Mingaliev, R. Udovitskiy, Anastasia Kudryashova, Vladislav Stolyarov, Tamara Semenova","doi":"10.3390/galaxies12030025","DOIUrl":"https://doi.org/10.3390/galaxies12030025","url":null,"abstract":"We present a study of the radio variability of bright, S1.4≥100 mJy, high-redshift quasars at z≥3 on timescales of up to 30–40 yrs. The study involved simultaneous RATAN-600 measurements at the frequencies of 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2017–2020. In addition, data from the literature were used. We have found that the variability index, VS, which quantifies the normalized difference between the maximum and minimum flux density while accounting for measurement uncertainties, ranges from 0.02 to 0.96 for the quasars. Approximately half of the objects in the sample exhibit a variability index within the range from 0.25 to 0.50, which is comparable to that observed in blazars at lower redshifts. The distribution of VS at 22.3 GHz is significantly different from that at 2.3–11.2 GHz, which may be attributed to the fact that a compact AGN core dominates at the source’s rest frame frequencies greater than 45 GHz, leading to higher variability indices obtained at 22.3 GHz (the VS distribution peaks around 0.4) compared to the lower frequencies (the VS distribution at 2.3 and 4.7 GHz peaks around 0.1–0.2). Several source groups with distinctive variability characteristics were found using the cluster analysis of quasars. We propose seven new candidates for gigahertz-peaked spectrum (GPS) sources and five new megahertz-peaked spectrum (MPS) sources based on their spectrum shape and variability features. Only 6 out of the 23 sources previously reported as GPS demonstrate a low variability level typical of classical GPS sources (VS<0.25) at 4.7–22.3 GHz. When excluding the highly variable peaked-spectrum blazars, we expect no more than 20% of the sources in the sample to be GPS candidates and no more than 10% to be MPS candidates.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140975726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-07DOI: 10.3390/galaxies12030023
I. A. Gabitova, A. Miroshnichenko, S. Zharikov, A. Amantayeva, S. Khokhlov
κ Draconis is a binary system with a classical Be star as the primary component. Its emission-line spectrum consists of hydrogen lines, notably the Hα line with peak intensity ratio (V/R) variations phase-locked with the orbital period P = 61.55 days. Among binaries demonstrating the Be phenomenon, κ Dra stands out as one of a few systems with a discernible mass of its secondary component. Based on more than 200 spectra obtained in 2014–2023, we verified the physical parameters and constructed the mass function. We used part of these data obtained in 2014–2021 to investigate regions in the circumstellar disk of the primary component that emit the Hα line using the Doppler tomography method. The results show that the disk has a non-uniform density distribution with a prominent enhancement at Vy ≈ 99 km s−1 and Vx≈−6 km s−1 that corresponds to a cloud-like source of the double-peaked Hα line profile. We argue that this enhancement’s motion is responsible for the periodic variations in the Hα V/R ratio, which is synchronised in orbital phase with the radial velocity (RV) of absorption lines from the atmosphere of the primary component.
κ Draconis 是一个双星系统，主成分是一颗经典的 Be 星。它的发射线光谱由氢线组成，特别是峰值强度比（V/R）变化与轨道周期 P = 61.55 天相位锁定的 Hα 线。在表现出 Be 现象的双星中，κ Dra 是少数几个次级成分质量可辨的系统之一。基于 2014-2023 年获得的 200 多条光谱，我们验证了物理参数并构建了质量函数。我们利用 2014-2021 年获得的部分数据，采用多普勒层析成像法研究了主成分周星盘中发射 Hα 线的区域。结果显示，星盘的密度分布并不均匀，在 Vy ≈ 99 km s-1 和 Vx≈-6 km s-1 处有明显的增强，对应于双峰 Hα 线剖面的云状源。我们认为，这种增强运动是造成 Hα V/R 比值周期性变化的原因，它在轨道相位上与来自主成分大气层的吸收线的径向速度（RV）同步。
{"title":"Doppler Tomography of the Circumstellar Disk of the Be Star κ Draconis","authors":"I. A. Gabitova, A. Miroshnichenko, S. Zharikov, A. Amantayeva, S. Khokhlov","doi":"10.3390/galaxies12030023","DOIUrl":"https://doi.org/10.3390/galaxies12030023","url":null,"abstract":"κ Draconis is a binary system with a classical Be star as the primary component. Its emission-line spectrum consists of hydrogen lines, notably the Hα line with peak intensity ratio (V/R) variations phase-locked with the orbital period P = 61.55 days. Among binaries demonstrating the Be phenomenon, κ Dra stands out as one of a few systems with a discernible mass of its secondary component. Based on more than 200 spectra obtained in 2014–2023, we verified the physical parameters and constructed the mass function. We used part of these data obtained in 2014–2021 to investigate regions in the circumstellar disk of the primary component that emit the Hα line using the Doppler tomography method. The results show that the disk has a non-uniform density distribution with a prominent enhancement at Vy ≈ 99 km s−1 and Vx≈−6 km s−1 that corresponds to a cloud-like source of the double-peaked Hα line profile. We argue that this enhancement’s motion is responsible for the periodic variations in the Hα V/R ratio, which is synchronised in orbital phase with the radial velocity (RV) of absorption lines from the atmosphere of the primary component.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141001982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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