Pub Date : 2021-06-11DOI: 10.1051/0004-6361/202140764
N. Mandarakas, D. Blinov, C. Casadio, V. Pelgrims, S. Kiehlmann, V. Pavlidou, K. Tassis
Context.Coherence in the characteristics of neighboring sources in 2D and 3D space may suggest the existence of large-scale cosmic structures, which are useful for cosmological studies. Numerous works have been conducted to detect such features in global scalesas well as in confined areas of the sky. However, results are often contradictory and their interpretation remains controversial. Aims.We investigate the potential alignment of parsec-scale radio jets in localized regions of the coordinates-redshift space. Methods.We use data from the Astrogeo VLBI FITS image database to deduce jet directions of radio sources. We perform the search for statistical alignments between nearby sources and explore the impact of instrumental biases. Results.We unveil four regions for which the alignment between jet directions deviates from randomness at a significance level of more than 5 sigma and is unlikely due to instrumental systematics. Intriguingly, their locations coincide with other known large-scale cosmic structures and/or regions of alignments. Conclusions.If the alignments found are the result of physical processes, the discovered regions may designate some of the largest structures known to date.
{"title":"Local alignments of parsec-scale AGN radiojets","authors":"N. Mandarakas, D. Blinov, C. Casadio, V. Pelgrims, S. Kiehlmann, V. Pavlidou, K. Tassis","doi":"10.1051/0004-6361/202140764","DOIUrl":"https://doi.org/10.1051/0004-6361/202140764","url":null,"abstract":"Context.Coherence in the characteristics of neighboring sources in 2D and 3D space may suggest the existence of large-scale cosmic structures, which are useful for cosmological studies. Numerous works have been conducted to detect such features in global scalesas well as in confined areas of the sky. However, results are often contradictory and their interpretation remains controversial. Aims.We investigate the potential alignment of parsec-scale radio jets in localized regions of the coordinates-redshift space. Methods.We use data from the Astrogeo VLBI FITS image database to deduce jet directions of radio sources. We perform the search for statistical alignments between nearby sources and explore the impact of instrumental biases. Results.We unveil four regions for which the alignment between jet directions deviates from randomness at a significance level of more than 5 sigma and is unlikely due to instrumental systematics. Intriguingly, their locations coincide with other known large-scale cosmic structures and/or regions of alignments. Conclusions.If the alignments found are the result of physical processes, the discovered regions may designate some of the largest structures known to date.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"115 11 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90231262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-09DOI: 10.1051/0004-6361/202140851
M. L. Corredoira, C. Gutiérrez
Aims. Dust in spiral galaxies produces emission in the far-infrared (FIR) and internal absorption in visible wavelengths. However, the relation of the two amounts is not trivial because optical absorption may saturate, but the FIR emission does not. Moreover, the volume concentration of dust plays a role in the relation of absorption and emission, which depends on the size of the galaxy. We explore the relation of these three quantities. Methods. In order to understand the geometrical problem, we developed a model of dust distribution. We also investigated the relation of the three variables with real data of spiral galaxies at z < 0.2 using the spectroscopic Sloan Digital Sky Survey (SDSS) and FIR AKARI survey. Internal absorptions were derived with two different methods: the ratio of emission lines Hα and Hβ, and a previously calibrated relation based on the color variations as a function of absolute magnitude and concentration index. Results. We find that in our low-z sample, the dependence of the average internal attenuation on galaxy size is negligible on average because of the relation of dust mass with size. It allows us to derive the internal attenuation of the galaxy, AV , even when we only know its FIR flux. This attenuation approximately depends on the inclination of the galaxy i as AV = γV log10 ( 1 cos i ) , where γV is a constant. We found that γV has a maximum value for galaxies of 1.45 ± 0.27 magnitudes. When similar properties of dust are assumed, a general expression can be used at any z: γV = (1.45 ± 0.27) f exp [−(1.0±0.6) fM ] M and fM = 7.6×10−6α−1.75 hR × ( FFIR 700 Jy )1.87 × fcosmol.(z); the dependence on the cosmological model is embedded in fcosmol.(z) = dL(z)(Mpc)(1+ z)(1.75η−1.87), where η = 2 for cosmologies following Etherington’s relation, dL is the luminosity distance, αhR is the angular size of the scalelength, and FFIR the flux at wavelength 100(1 + z) μm. Conclusions. For cases of nonsaturation ( f . 3.6), this might be used as a cosmological test because the factor fcosmol. at high z varies strongly in different cosmologies. Although the present-day sensitivity of FIR or millimeter surveys does not allow us to carry out this cosmological test within the standard model, it may be used in the future, when we can observe galaxies at z = 3− 5 with a sensitivity at ∼500 μm better than ∼ 10 μJy, for instance. For much lower z or different cosmological models, a test might be feasible at present.
{"title":"Relation of internal attenuation, dust emission, and the size of spiral galaxies","authors":"M. L. Corredoira, C. Gutiérrez","doi":"10.1051/0004-6361/202140851","DOIUrl":"https://doi.org/10.1051/0004-6361/202140851","url":null,"abstract":"Aims. Dust in spiral galaxies produces emission in the far-infrared (FIR) and internal absorption in visible wavelengths. However, the relation of the two amounts is not trivial because optical absorption may saturate, but the FIR emission does not. Moreover, the volume concentration of dust plays a role in the relation of absorption and emission, which depends on the size of the galaxy. We explore the relation of these three quantities. Methods. In order to understand the geometrical problem, we developed a model of dust distribution. We also investigated the relation of the three variables with real data of spiral galaxies at z < 0.2 using the spectroscopic Sloan Digital Sky Survey (SDSS) and FIR AKARI survey. Internal absorptions were derived with two different methods: the ratio of emission lines Hα and Hβ, and a previously calibrated relation based on the color variations as a function of absolute magnitude and concentration index. Results. We find that in our low-z sample, the dependence of the average internal attenuation on galaxy size is negligible on average because of the relation of dust mass with size. It allows us to derive the internal attenuation of the galaxy, AV , even when we only know its FIR flux. This attenuation approximately depends on the inclination of the galaxy i as AV = γV log10 ( 1 cos i ) , where γV is a constant. We found that γV has a maximum value for galaxies of 1.45 ± 0.27 magnitudes. When similar properties of dust are assumed, a general expression can be used at any z: γV = (1.45 ± 0.27) f exp [−(1.0±0.6) fM ] M and fM = 7.6×10−6α−1.75 hR × ( FFIR 700 Jy )1.87 × fcosmol.(z); the dependence on the cosmological model is embedded in fcosmol.(z) = dL(z)(Mpc)(1+ z)(1.75η−1.87), where η = 2 for cosmologies following Etherington’s relation, dL is the luminosity distance, αhR is the angular size of the scalelength, and FFIR the flux at wavelength 100(1 + z) μm. Conclusions. For cases of nonsaturation ( f . 3.6), this might be used as a cosmological test because the factor fcosmol. at high z varies strongly in different cosmologies. Although the present-day sensitivity of FIR or millimeter surveys does not allow us to carry out this cosmological test within the standard model, it may be used in the future, when we can observe galaxies at z = 3− 5 with a sensitivity at ∼500 μm better than ∼ 10 μJy, for instance. For much lower z or different cosmological models, a test might be feasible at present.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"138 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79818127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-09DOI: 10.1051/0004-6361/202140438
Natalie Grasser, Sebastian Ratzenböck, J. Alves, J. Großschedl, S. Meingast, C. Zucker, Á. Hacar, C. Lada, A. Goodman, M. Lombardi, John C. Forbes, I. Bomze, Torsten Möller
Context. Young and embedded stellar populations are important probes of the star formation process. Their properties and the environments they create have the potential to a ff ect the formation of new planets. Paradoxically, we have a better census of nearby embedded young populations than of the slightly more evolved optically visible young populations. The high accuracy measurements and all-sky coverage of Gaia data are about to change this situation. Aims. This work aims to construct the most complete sample to date of young stellar objects (YSOs) in the ρ Oph region. Methods. We compile a catalog of 1114 Ophiuchus YSOs from the literature and cross-match it with the Gaia EDR3, Gaia -ESO, and APOGEE-2 surveys. We apply a multivariate classification algorithm to this catalog to identify new, co-moving population candidates. Results. We find 191 new high-fidelity YSO candidates in the Gaia EDR3 catalog belonging to the ρ Oph region. The new sources appear to be mainly ClassIII M stars and substellar objects and are less extincted than the known members, while we find that 28 of the previously unknown sources are YSOs with circumstellar disks (ClassI or ClassII). The analysis of the proper motion distri- bution of the entire sample reveals a well-defined bimodality, implying two distinct populations sharing a similar 3D volume. The first population comprises young stars’ clusters around the ρ Ophiuchi star and the main Ophiuchus clouds (L1688, L1689, L1709). In contrast, the second population is slightly older ( ∼ 10Myr), more dispersed, has a distinct proper motion, and is possibly from the Upper Sco group. The two populations are moving away from each other at about 4.1kms − 1 and will no longer overlap in about 4Myr. Finally, we flag 17 sources in the literature sample as likely impostors, which are sources that exhibit large deviations from the average properties of the ρ Oph population. Our results show the importance of accurate 3D space and motion information for improved stellar population analysis.
{"title":"The rho Ophiuchi region revisited with Gaia EDR3. Two young populations, new members, and old impostors","authors":"Natalie Grasser, Sebastian Ratzenböck, J. Alves, J. Großschedl, S. Meingast, C. Zucker, Á. Hacar, C. Lada, A. Goodman, M. Lombardi, John C. Forbes, I. Bomze, Torsten Möller","doi":"10.1051/0004-6361/202140438","DOIUrl":"https://doi.org/10.1051/0004-6361/202140438","url":null,"abstract":"Context. Young and embedded stellar populations are important probes of the star formation process. Their properties and the environments they create have the potential to a ff ect the formation of new planets. Paradoxically, we have a better census of nearby embedded young populations than of the slightly more evolved optically visible young populations. The high accuracy measurements and all-sky coverage of Gaia data are about to change this situation. Aims. This work aims to construct the most complete sample to date of young stellar objects (YSOs) in the ρ Oph region. Methods. We compile a catalog of 1114 Ophiuchus YSOs from the literature and cross-match it with the Gaia EDR3, Gaia -ESO, and APOGEE-2 surveys. We apply a multivariate classification algorithm to this catalog to identify new, co-moving population candidates. Results. We find 191 new high-fidelity YSO candidates in the Gaia EDR3 catalog belonging to the ρ Oph region. The new sources appear to be mainly ClassIII M stars and substellar objects and are less extincted than the known members, while we find that 28 of the previously unknown sources are YSOs with circumstellar disks (ClassI or ClassII). The analysis of the proper motion distri- bution of the entire sample reveals a well-defined bimodality, implying two distinct populations sharing a similar 3D volume. The first population comprises young stars’ clusters around the ρ Ophiuchi star and the main Ophiuchus clouds (L1688, L1689, L1709). In contrast, the second population is slightly older ( ∼ 10Myr), more dispersed, has a distinct proper motion, and is possibly from the Upper Sco group. The two populations are moving away from each other at about 4.1kms − 1 and will no longer overlap in about 4Myr. Finally, we flag 17 sources in the literature sample as likely impostors, which are sources that exhibit large deviations from the average properties of the ρ Oph population. Our results show the importance of accurate 3D space and motion information for improved stellar population analysis.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"72 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89522995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-09DOI: 10.1051/0004-6361/202140731
E. Forg'acs-Dajka, L. Dobos, I. Ballai
Aims. In this paper, we aim to study the time dependence of sunspot group areas in a large sample composed of various databases spanning over 130 years, used state-of-the-art statistical methods. Methods. For a carefully selected but unbiased sample, we use Bayesian modelling to fit the temporal evolution of the combined umbral and penumbral area of spot groups with a skew-normal function to determine the existence of any asymmetry in spot growth or decay. Our primary selection criteria guaranteed that only spot groups with a well-defined maximum area were taken into account. We also analysed the covariance of the resulting model parameters and their correlations with the physical parameters of the sunspots and the ongoing solar cycle. Results. Our results show that the temporal evolution of well-observed sunspot groups that reach at least 50 millionths of a solar hemisphere (MSH) at their maximum can be fitted surprisingly well with our model. Furthermore, we show significant asymmetry - described by a skew parameter of fitted curves - between the growing and decaying phases of analysed sunspot groups. In addition, we found a weak correlation between the values of skew parameters and the maximum area of sunspot groups and their hemispherical latitude.
{"title":"Time-dependent properties of sunspot groups. I. Lifetime and asymmetric evolution","authors":"E. Forg'acs-Dajka, L. Dobos, I. Ballai","doi":"10.1051/0004-6361/202140731","DOIUrl":"https://doi.org/10.1051/0004-6361/202140731","url":null,"abstract":"Aims. In this paper, we aim to study the time dependence of sunspot group areas in a large sample composed of various databases spanning over 130 years, used state-of-the-art statistical methods. \u0000Methods. For a carefully selected but unbiased sample, we use Bayesian modelling to fit the temporal evolution of the combined umbral and penumbral area of spot groups with a skew-normal function to determine the existence of any asymmetry in spot growth or decay. Our primary selection criteria guaranteed that only spot groups with a well-defined maximum area were taken into account. We also analysed the covariance of the resulting model parameters and their correlations with the physical parameters of the sunspots and the ongoing solar cycle. \u0000Results. Our results show that the temporal evolution of well-observed sunspot groups that reach at least 50 millionths of a solar hemisphere (MSH) at their maximum can be fitted surprisingly well with our model. Furthermore, we show significant asymmetry - described by a skew parameter of fitted curves - between the growing and decaying phases of analysed sunspot groups. In addition, we found a weak correlation between the values of skew parameters and the maximum area of sunspot groups and their hemispherical latitude.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"1 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85545753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-09DOI: 10.1051/0004-6361/201937241
N. MacDonald, K. Nishikawa
The underlying plasma composition of relativistic extragalactic jets remains largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to reproduce many of the observed macroscopic features of these outflows. The nonthermal synchrotron emission detected by very long baseline interferometric (VLBI) arrays, however, is a by-product of the kinetic-scale physics occurring within the jet, physics that is not modeled directly in most RMHD codes. This paper attempts to discern the radiative differences between distinct plasma compositions within relativistic jets using small-scale 3D relativistic particle-in-cell (PIC) simulations. We generate full Stokes imaging of two PIC jet simulations, one in which the jet is composed of an electron-proton ($e^{-}$-$p^{+}$) plasma (i.e., a normal plasma jet), and the other in which the jet is composed of an electron-positron ($e^{-}$-$e^{+}$) plasma (i.e., a pair plasma jet). We examined the differences in the morphology and intensity of the linear polarization (LP) and circular polarization (CP) emanating from these two jet simulations. We find that the fractional level of CP emanating from the $e^{-}$-$p^{+}$ plasma jet is orders of magnitude larger than the level emanating from an $e^{-}$-$e^{+}$ plasma jet of a similar speed and magnetic field strength. In addition, we find that the morphology of both the linearly and circularly polarized synchrotron emission is distinct between the two jet compositions. We also demonstrate the importance of slow-light interpolation and we highlight the effect that a finite light-crossing time has on the resultant polarization when ray-tracing through relativistic plasma.
{"title":"From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations","authors":"N. MacDonald, K. Nishikawa","doi":"10.1051/0004-6361/201937241","DOIUrl":"https://doi.org/10.1051/0004-6361/201937241","url":null,"abstract":"The underlying plasma composition of relativistic extragalactic jets remains largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to reproduce many of the observed macroscopic features of these outflows. The nonthermal synchrotron emission detected by very long baseline interferometric (VLBI) arrays, however, is a by-product of the kinetic-scale physics occurring within the jet, physics that is not modeled directly in most RMHD codes. This paper attempts to discern the radiative differences between distinct plasma compositions within relativistic jets using small-scale 3D relativistic particle-in-cell (PIC) simulations. We generate full Stokes imaging of two PIC jet simulations, one in which the jet is composed of an electron-proton ($e^{-}$-$p^{+}$) plasma (i.e., a normal plasma jet), and the other in which the jet is composed of an electron-positron ($e^{-}$-$e^{+}$) plasma (i.e., a pair plasma jet). We examined the differences in the morphology and intensity of the linear polarization (LP) and circular polarization (CP) emanating from these two jet simulations. We find that the fractional level of CP emanating from the $e^{-}$-$p^{+}$ plasma jet is orders of magnitude larger than the level emanating from an $e^{-}$-$e^{+}$ plasma jet of a similar speed and magnetic field strength. In addition, we find that the morphology of both the linearly and circularly polarized synchrotron emission is distinct between the two jet compositions. We also demonstrate the importance of slow-light interpolation and we highlight the effect that a finite light-crossing time has on the resultant polarization when ray-tracing through relativistic plasma.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"405 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76701615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-09DOI: 10.1051/0004-6361/202140835
R. Cubarsi, M. Stojanović, S. Ninkovič
Context. In previous work, we showed how the planar and vertical eccentricities of disc stars, e and e′, could be used as indicators of the stars’ kinematic populations. For a local stellar sample drawn from the Gaia DR2 catalogue, these populations were represented geometrically in the eccentricity diagram, e′2 vs. e2, approximately separated by straight lines. Aims. In the current work, we propose a new relationship between the star’s perpendicular velocity and its vertical eccentricity, allowing for a reevaluation of the critical vertical eccentricity and maximum height, zmax, specific to each population component. Methods. We approximated the local potential function to be consistent with the actual shape of the curve that relates the maximum vertical speed of a star and its maximum height. The curve corresponds to a non-linear restoring vertical force, where the stiffness decreases with an increase in the maximum height. The constants involved in this fitting, together with the population velocity dispersions, determine the specific region for each population in the eccentricity diagram. Results. The new classification determines 88% of the sample is made up of thin disc stars and 9% of thick disc stars, whereby 3% of the stars have been relabelled, by providing thinner thin and thick discs. Nested thin disc subsamples allow us to estimate Strömberg’s asymmetric drift equation, leading to a heliocentric velocity of the circular orbit of Vc ≈ −12.9 km s−1, an absolute rotation velocity of Θc ≈ 227 km s−1, and a rotation component of the Galactocentric velocity of the Sun at Θ ≈ 240 km s−1. Conclusions. The thin disc stars of our local sample are characterised based on values 0 ≤ e ≤ 0.32, 0 ≤ e′ ≤ 0.09, and zmax = 0.7 kpc. Disc stars satisfy 0 ≤ e ≤ 0.44, 0 ≤ e′ ≤ 0.18, zmax = 1.5 kpc. The maximum vertical peculiar velocity for disc stars is found to be w0 = 115 km s−1. The assumed potential provides a stellar density of the disc vanishing at z0 = 1.8 kpc. The approximate behaviour in the local disc is that a small decrease in the stiffness is associated with a relative decrease in the limiting velocity, which produces a thinner disc and a loss of stars in the local cylinder, both in a similar proportion to the limiting velocity.
上下文。在之前的工作中，我们展示了盘状恒星的平面和垂直偏心率e和e '可以作为恒星运动种群的指标。对于从盖亚DR2星表中提取的一个本地恒星样本，这些恒星群在偏心率图中以几何方式表示，e ' 2对e2，大约用直线分开。目标在目前的工作中，我们提出了恒星垂直速度与其垂直偏心率之间的新关系，允许重新评估临界垂直偏心率和最大高度zmax，具体到每个人口组成部分。方法。我们将局部势函数近似为与恒星的最大垂直速度与其最大高度相关的曲线的实际形状一致。该曲线对应于非线性恢复垂直力，其中刚度随着最大高度的增加而减小。这种拟合所涉及的常数，连同种群速度的分散，决定了偏心图中每个种群的特定区域。结果。新的分类确定了88%的样本由薄盘星和9%的厚盘星组成，其中3%的恒星通过提供更薄的薄盘和厚盘被重新标记。嵌套的薄圆盘子样本使我们能够估计Strömberg的不对称漂移方程，从而得出Vc圆轨道的日心速度≈−12.9 km s−1，绝对自转速度Θc≈227 km s−1，以及太阳的银河系中心速度的旋转分量Θ≈240 km s−1。结论。我们本地样本的薄盘星的特征值为0≤e≤0.32,0≤e′≤0.09,zmax = 0.7 kpc。盘星满足0≤e≤0.44,0≤e′≤0.18,zmax = 1.5 kpc。盘状恒星的最大垂直特殊速度为w0 = 115 km s−1。假设的势能提供了在z0 = 1.8 kpc处消失的星盘密度。在局部圆盘上的近似行为是，刚度的小幅下降与极限速度的相对下降有关，这会产生更薄的圆盘和局部圆柱体中恒星的损失，两者与极限速度的比例相似。
{"title":"Orbital eccentricities as indicators of stellar populations. II. Vertical velocity distribution from the Gaia DR2 catalogue","authors":"R. Cubarsi, M. Stojanović, S. Ninkovič","doi":"10.1051/0004-6361/202140835","DOIUrl":"https://doi.org/10.1051/0004-6361/202140835","url":null,"abstract":"Context. In previous work, we showed how the planar and vertical eccentricities of disc stars, e and e′, could be used as indicators of the stars’ kinematic populations. For a local stellar sample drawn from the Gaia DR2 catalogue, these populations were represented geometrically in the eccentricity diagram, e′2 vs. e2, approximately separated by straight lines. Aims. In the current work, we propose a new relationship between the star’s perpendicular velocity and its vertical eccentricity, allowing for a reevaluation of the critical vertical eccentricity and maximum height, zmax, specific to each population component. Methods. We approximated the local potential function to be consistent with the actual shape of the curve that relates the maximum vertical speed of a star and its maximum height. The curve corresponds to a non-linear restoring vertical force, where the stiffness decreases with an increase in the maximum height. The constants involved in this fitting, together with the population velocity dispersions, determine the specific region for each population in the eccentricity diagram. Results. The new classification determines 88% of the sample is made up of thin disc stars and 9% of thick disc stars, whereby 3% of the stars have been relabelled, by providing thinner thin and thick discs. Nested thin disc subsamples allow us to estimate Strömberg’s asymmetric drift equation, leading to a heliocentric velocity of the circular orbit of Vc ≈ −12.9 km s−1, an absolute rotation velocity of Θc ≈ 227 km s−1, and a rotation component of the Galactocentric velocity of the Sun at Θ ≈ 240 km s−1. Conclusions. The thin disc stars of our local sample are characterised based on values 0 ≤ e ≤ 0.32, 0 ≤ e′ ≤ 0.09, and zmax = 0.7 kpc. Disc stars satisfy 0 ≤ e ≤ 0.44, 0 ≤ e′ ≤ 0.18, zmax = 1.5 kpc. The maximum vertical peculiar velocity for disc stars is found to be w0 = 115 km s−1. The assumed potential provides a stellar density of the disc vanishing at z0 = 1.8 kpc. The approximate behaviour in the local disc is that a small decrease in the stiffness is associated with a relative decrease in the limiting velocity, which produces a thinner disc and a loss of stars in the local cylinder, both in a similar proportion to the limiting velocity.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"128 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74918268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-03DOI: 10.1051/0004-6361/202039571
M. Aoki, F. Primas, L. Pasquini, A. Weiss, M. Salaris, D. Carollo
Our aim was to determine the initial Li content of two clusters of similar metallicity but very different ages, the old open cluster NGC 2243 and the metal-rich globular cluster NGC 104. We compared the lithium abundances derived for a large sample of stars (from the turn-off to the red giant branch) in each cluster. For NGC 2243 the Li abundances are from the catalogues released by the Gaia-ESO Public Spectroscopic Survey, while for NGC 104 we measured the Li abundance using FLAMES/GIRAFFE spectra, which include archival data and new observations. We took the initial Li of NGC 2243 to be the lithium measured in stars on the hot side of the Li dip. We used the difference between the initial abundances and the post first dredge-up Li values of NGC 2243, and by adding this amount to the post first dredge-up stars of NGC~104 we were able to infer the initial Li of this cluster. Moreover, we compared our observational results to the predictions of theoretical stellar models for the difference between the initial Li abundance and that after the first dredge-up. The initial lithium content of NGC 2243 was found to be A(Li)_i = 2.85dex by taking the average Li abundance measured from the five hottest stars with the highest lithium abundance. This value is 1.69 dex higher than the lithium abundance derived in post first dredge-up stars. By adding this number to the lithium abundance derived in the post first dredge-up stars in NGC~104, we infer a lower limit of its initial lithium content of A(Li)_i= 2.30dex. Stellar models predict similar values. Therefore, our result offers important insights for further theoretical developments.
{"title":"Lithium in NGC 2243 and NGC 104","authors":"M. Aoki, F. Primas, L. Pasquini, A. Weiss, M. Salaris, D. Carollo","doi":"10.1051/0004-6361/202039571","DOIUrl":"https://doi.org/10.1051/0004-6361/202039571","url":null,"abstract":"Our aim was to determine the initial Li content of two clusters of similar metallicity but very different ages, the old open cluster NGC 2243 and the metal-rich globular cluster NGC 104. We compared the lithium abundances derived for a large sample of stars (from the turn-off to the red giant branch) in each cluster. For NGC 2243 the Li abundances are from the catalogues released by the Gaia-ESO Public Spectroscopic Survey, while for NGC 104 we measured the Li abundance using FLAMES/GIRAFFE spectra, which include archival data and new observations. We took the initial Li of NGC 2243 to be the lithium measured in stars on the hot side of the Li dip. We used the difference between the initial abundances and the post first dredge-up Li values of NGC 2243, and by adding this amount to the post first dredge-up stars of NGC~104 we were able to infer the initial Li of this cluster. Moreover, we compared our observational results to the predictions of theoretical stellar models for the difference between the initial Li abundance and that after the first dredge-up. The initial lithium content of NGC 2243 was found to be A(Li)_i = 2.85dex by taking the average Li abundance measured from the five hottest stars with the highest lithium abundance. This value is 1.69 dex higher than the lithium abundance derived in post first dredge-up stars. By adding this number to the lithium abundance derived in the post first dredge-up stars in NGC~104, we infer a lower limit of its initial lithium content of A(Li)_i= 2.30dex. Stellar models predict similar values. Therefore, our result offers important insights for further theoretical developments.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"1 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88322070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1051/0004-6361/202140375
Yong Zhao, D. Ni
Context. Earth-sized exoplanets have been discovered and characterized thanks to new developments in observational techniques, particularly those planets that may have a rocky composition that is comparable to terrestrial planets of the Solar System. Characterizing the interiors of rocky exoplanets is one of the main objectives in investigations of their habitability. Theoretical mass-radius relations are often used as a tool to constrain the internal structure of rocky exoplanets. But one mass-radius curve only represents a single interior structure and a great deal of computation time is required to obtain all possible interior structures that comply with the given mass and radius of a planet. Aims. We apply a machine-learning approach based on mixture density networks (MDNs) to investigate the interiors of rocky exoplanets. We aim to provide a well-trained MDN model to quickly and efficiently predict the interior structure of rocky exoplanets. Methods. We presented a training data set of rocky exoplanets with masses between 0.1 and 10 Earth masses based on three-layer interior models by assuming Earth-like compositions. This data set was then used to train the MDN model to predict the layer thicknesses and core properties of rocky exoplanets, where planetary mass, radius, and water content are inputs to the MDN. The performance of the trained MDN model was investigated in order to discern its predictive ability. Results. The MDN model is found to show good performance in predicting the layer thicknesses and core properties of rocky exoplanets through a comparison with the real solutions obtained by solving the interior models. We also applied the MDN model to the Earth and the super-Earth exoplanet LHS 1140b. The MDN predictions are in good agreement with the interior model solutions within the uncertainties of planetary mass and radius. More importantly, the MDN model takes a much shorter computational time compared to the cost of the interior model calculations, offering a convenient and powerful tool for quickly obtaining information on planetary interiors.
{"title":"Machine learning techniques in studies of the interior structure of rocky exoplanets","authors":"Yong Zhao, D. Ni","doi":"10.1051/0004-6361/202140375","DOIUrl":"https://doi.org/10.1051/0004-6361/202140375","url":null,"abstract":"Context. Earth-sized exoplanets have been discovered and characterized thanks to new developments in observational techniques, particularly those planets that may have a rocky composition that is comparable to terrestrial planets of the Solar System. Characterizing the interiors of rocky exoplanets is one of the main objectives in investigations of their habitability. Theoretical mass-radius relations are often used as a tool to constrain the internal structure of rocky exoplanets. But one mass-radius curve only represents a single interior structure and a great deal of computation time is required to obtain all possible interior structures that comply with the given mass and radius of a planet.\u0000Aims. We apply a machine-learning approach based on mixture density networks (MDNs) to investigate the interiors of rocky exoplanets. We aim to provide a well-trained MDN model to quickly and efficiently predict the interior structure of rocky exoplanets.\u0000Methods. We presented a training data set of rocky exoplanets with masses between 0.1 and 10 Earth masses based on three-layer interior models by assuming Earth-like compositions. This data set was then used to train the MDN model to predict the layer thicknesses and core properties of rocky exoplanets, where planetary mass, radius, and water content are inputs to the MDN. The performance of the trained MDN model was investigated in order to discern its predictive ability.\u0000Results. The MDN model is found to show good performance in predicting the layer thicknesses and core properties of rocky exoplanets through a comparison with the real solutions obtained by solving the interior models. We also applied the MDN model to the Earth and the super-Earth exoplanet LHS 1140b. The MDN predictions are in good agreement with the interior model solutions within the uncertainties of planetary mass and radius. More importantly, the MDN model takes a much shorter computational time compared to the cost of the interior model calculations, offering a convenient and powerful tool for quickly obtaining information on planetary interiors.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"7 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82906765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.1051/0004-6361/202040268
H. Gu, J. Cui, D. Niu, X. Wu, F. He, Yong Wei
{"title":"Non-thermal escape on Triton driven by atmospheric and ionospheric chemistry","authors":"H. Gu, J. Cui, D. Niu, X. Wu, F. He, Yong Wei","doi":"10.1051/0004-6361/202040268","DOIUrl":"https://doi.org/10.1051/0004-6361/202040268","url":null,"abstract":"","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"13 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74293013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-31DOI: 10.1051/0004-6361/202141452
R. Abbott, T. Abbott, F. Acernese, K. Ackley, C. Adams, N. Adhikari, R. Adhikari, V. Adya, C. Affeldt, D. Agarwal, M. Agathos, K. Agatsuma, N. Aggarwal, O. Aguiar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, A. Allocca, P. Altin, A. Amato, C. Anand, S. Anand, A. Ananyeva, S. Anderson, W. Anderson, M. Ando, T. Andrade, N. Andrés, S. Angelova, S. Ansoldi, J. Antelis, S. Antier, S. Appert, K. Arai, K. Arai, Y. Arai, S. Araki, A. Araya, M. Araya, J. Areeda, M. Arène, N. Aritomi, N. Arnaud, S. Aronson, K. Arun, H. Asada, Y. Asali, G. Ashton, Y. Aso, M. Assiduo, S. Aston, P. Astone, F. Aubin, C. Austin, S. Babak, F. Badaracco, M. Bader, C. Badger, S. Bae, Y. Bae, A. Baer, S. Bagnasco, Y. Bai, L. Baiotti, J. Baird, R. Bajpai, M. Ball, G. Ballardin, S. Ballmer, A. Balsamo, G. Baltus, S. Banagiri, D. Bankar, J. Barayoga, C. Barbieri, B. Barish, D. Barker, P. Barneo, F. Barone, B. Barr, L. Barsotti, M. Barsuglia, D. Barta, J. Bartlett, M. Barton, I. Bartos, R. Bassiri, A. Basti, M. Bawaj, J. Bayley, A. Bay
Intermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M , between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.
{"title":"Search for intermediate mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo","authors":"R. Abbott, T. Abbott, F. Acernese, K. Ackley, C. Adams, N. Adhikari, R. Adhikari, V. Adya, C. Affeldt, D. Agarwal, M. Agathos, K. Agatsuma, N. Aggarwal, O. Aguiar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, A. Allocca, P. Altin, A. Amato, C. Anand, S. Anand, A. Ananyeva, S. Anderson, W. Anderson, M. Ando, T. Andrade, N. Andrés, S. Angelova, S. Ansoldi, J. Antelis, S. Antier, S. Appert, K. Arai, K. Arai, Y. Arai, S. Araki, A. Araya, M. Araya, J. Areeda, M. Arène, N. Aritomi, N. Arnaud, S. Aronson, K. Arun, H. Asada, Y. Asali, G. Ashton, Y. Aso, M. Assiduo, S. Aston, P. Astone, F. Aubin, C. Austin, S. Babak, F. Badaracco, M. Bader, C. Badger, S. Bae, Y. Bae, A. Baer, S. Bagnasco, Y. Bai, L. Baiotti, J. Baird, R. Bajpai, M. Ball, G. Ballardin, S. Ballmer, A. Balsamo, G. Baltus, S. Banagiri, D. Bankar, J. Barayoga, C. Barbieri, B. Barish, D. Barker, P. Barneo, F. Barone, B. Barr, L. Barsotti, M. Barsuglia, D. Barta, J. Bartlett, M. Barton, I. Bartos, R. Bassiri, A. Basti, M. Bawaj, J. Bayley, A. Bay","doi":"10.1051/0004-6361/202141452","DOIUrl":"https://doi.org/10.1051/0004-6361/202141452","url":null,"abstract":"Intermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M , between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"50 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80013192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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