IF 3.2

Galaxies Pub Date : 2024-08-08 DOI: 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

{"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}

引用次数: 0

SS 433: Flares and L2 Overflow Spirals SS 433：喇叭口和 L2 溢流螺旋管

IF 3.2

Galaxies Pub Date : 2024-07-18 DOI: 10.3390/galaxies12040040

Michael Bowler

引用次数: 0

Planetary Nebulae Research: Past, Present, and Future 行星状星云研究：过去、现在和未来

IF 3.2

Galaxies Pub Date : 2024-07-17 DOI: 10.3390/galaxies12040039

Sun Kwok

{"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}

引用次数: 0

On the Making of IXPE 关于 IXPE 的制作

IF 3.2

Galaxies Pub Date : 2024-07-16 DOI: 10.3390/galaxies12040038

M. Weisskopf, B. Ramsey

引用次数: 0

Correlations between IR Luminosity, Star Formation Rate, and CO Luminosity in the Local Universe 局域宇宙中红外发光度、恒星形成率和 CO 发光度之间的相关性

IF 3.2

Galaxies Pub Date : 2024-07-08 DOI: 10.3390/galaxies12040037

M. Bonato, I. Baronchelli, Viviana Casasola, G. De Zotti, Leonardo Trobbiani, E. Ruli, Vidhi Tailor, Simone Bianchi

引用次数: 0

An Examination of the Very First Polarimetric X-ray Observations of Radio-Quiet Active Galactic Nuclei 对射电静止活动星系核的首次极坐标 X 射线观测的研究

IF 3.2

Galaxies Pub Date : 2024-07-02 DOI: 10.3390/galaxies12040035

F. Marin, V. Gianolli, A. Ingram, Dawoon E. Kim, A. Marinucci, D. Tagliacozzo, F. Ursini

{"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}

引用次数: 0

Wave-Particle Interactions in Astrophysical Plasmas 天体物理等离子体中的波粒相互作用

IF 2.5

Galaxies Pub Date : 2024-06-06 DOI: 10.3390/galaxies12030028

H. Pérez-de-Tejada

{"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}

引用次数: 0

ALMA Band 3 Source Counts: A Machine Learning Approach to Contamination Mitigation below 5 Sigma ALMA 波段 3 源计数：降低 5 西格玛以下污染的机器学习方法

IF 2.5

Galaxies Pub Date : 2024-05-20 DOI: 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

{"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}

引用次数: 0

High-Redshift Quasars at z≥3: Radio Variability and MPS/GPS Candidates z≥3的高红移类星体：射电变异性和MPS/GPS候选者

IF 2.5

Galaxies Pub Date : 2024-05-15 DOI: 10.3390/galaxies12030025

Y. Sotnikova, Alexander Mikhailov, T. Mufakharov, Tao An, Dmitry Kudryavtsev, M. Mingaliev, R. Udovitskiy, Anastasia Kudryashova, Vladislav Stolyarov, Tamara Semenova

{"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}

引用次数: 0

Doppler Tomography of the Circumstellar Disk of the Be Star κ Draconis Be 星 κ Draconis 的环状星盘多普勒断层扫描图

IF 2.5

Galaxies Pub Date : 2024-05-07 DOI: 10.3390/galaxies12030023

I. A. Gabitova, A. Miroshnichenko, S. Zharikov, A. Amantayeva, S. Khokhlov

{"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}

引用次数: 0

Galaxies最新文献