Alexander J Gordon, Annette M N Ferguson, Robert G Mann
Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionise the study of tidal features. However, the volume of data will prohibit visual inspection to identify features, thereby motivating a need to develop automated detection methods. This paper presents a visual classification of ∼2, 000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells, and diffuse. We trained a Convolutional Neural Network (CNN) to reproduce the assigned visual classifications using these labels. Evaluated on a testing set where galaxies with tidal features were outnumbered ∼1 : 10, our network performed very well and retrieved a median 98.7 ± 0.3, 99.1 ± 0.5, 97.0 ± 0.8, and $99.4^{+0.2}_{-0.6}$ per cent of the actual instances of arm, stream, shell, and diffuse features respectively for just 20percnt contamination. A modified version that identified galaxies with any feature against those without achieved scores of $0.981^{+0.001}_{-0.003}$, $0.834^{+0.014}_{-0.026}$, $0.974^{+0.008}_{-0.004}$, and $0.900^{+0.073}_{-0.015}$ for the accuracy, precision, recall, and F1 metrics, respectively. We used a Gradient-weighted Class Activation Mapping analysis to highlight important regions on images for a given classification to verify the network was classifying the galaxies correctly. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver.
{"title":"Uncovering Tidal Treasures: Automated Classification of faint tidal features in DECaLS Data","authors":"Alexander J Gordon, Annette M N Ferguson, Robert G Mann","doi":"10.1093/mnras/stae2169","DOIUrl":"https://doi.org/10.1093/mnras/stae2169","url":null,"abstract":"Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionise the study of tidal features. However, the volume of data will prohibit visual inspection to identify features, thereby motivating a need to develop automated detection methods. This paper presents a visual classification of ∼2, 000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells, and diffuse. We trained a Convolutional Neural Network (CNN) to reproduce the assigned visual classifications using these labels. Evaluated on a testing set where galaxies with tidal features were outnumbered ∼1 : 10, our network performed very well and retrieved a median 98.7 ± 0.3, 99.1 ± 0.5, 97.0 ± 0.8, and $99.4^{+0.2}_{-0.6}$ per cent of the actual instances of arm, stream, shell, and diffuse features respectively for just 20percnt contamination. A modified version that identified galaxies with any feature against those without achieved scores of $0.981^{+0.001}_{-0.003}$, $0.834^{+0.014}_{-0.026}$, $0.974^{+0.008}_{-0.004}$, and $0.900^{+0.073}_{-0.015}$ for the accuracy, precision, recall, and F1 metrics, respectively. We used a Gradient-weighted Class Activation Mapping analysis to highlight important regions on images for a given classification to verify the network was classifying the galaxies correctly. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"12 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
W J Cooper, H R A Jones, R L Smart, S L Folkes, J A Caballero, F Marocco, M C Gálvez Ortiz, A J Burgasser, J D Kirkpatrick, L M Sarro, B Burningham, A Cabrera-Lavers, P E Tremblay, C Reylé, N Lodieu, Z H Zhang, N J Cook, J F Faherty, D García-Álvarez, D Montes, D J Pinfield, A S Rajpurohit, J Shi
As part of our comprehensive, ongoing characterisation of the low-mass end of the main sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias to acquire low- and mid-resolution (R≈300 and R≈2500) optical spectroscopy of 53 late-M and L ultracool dwarfs. Most of these objects are known but poorly investigated and lacking complete kinematics. We measured spectral indices, determined spectral types (six of which are new) and inferred effective temperature and surface gravity from BT-Settl synthetic spectra fits for all objects. We were able to measure radial velocities via line centre fitting and cross correlation for 46 objects, 29 of which lacked previous radial velocity measurements. Using these radial velocities in combination with the latest Gaia DR3 data, we also calculated Galactocentric space velocities. From their kinematics, we identified two candidates outside of the thin disc and four in young stellar kinematic groups. Two further ultracool dwarfs are apparently young field objects: 2MASSW J1246467+402715 (L4β), which has a potential, weak lithium absorption line, and G 196–3B (L3β), which was already known as young due to its well-studied primary companion.
作为对太阳邻近地区主序低质量末端进行全面、持续描述的一部分，我们利用 10.4 米加那利大望远镜上的 OSIRIS 仪器对 53 个晚 M 和晚 L 超冷矮星进行了中低分辨率（R≈300 和 R≈2500）光学光谱分析。这些天体中的大多数都是已知的，但研究较少，缺乏完整的运动学数据。我们测量了光谱指数，确定了光谱类型（其中六种是新的），并通过 BT-Settl 合成光谱拟合推断出所有天体的有效温度和表面重力。我们通过线中心拟合和交叉相关测量了 46 个天体的径向速度，其中 29 个天体以前没有测量过径向速度。利用这些径向速度和最新的盖亚 DR3 数据，我们还计算出了伽马中心空间速度。根据这些天体的运动学特征，我们确定了薄圆盘外的两个候选天体和年轻恒星运动组中的四个候选天体。另外两个超冷矮星显然是年轻的场天体：2MASSW J1246467+402715 (L4β)和 G 196-3B (L3β)。
{"title":"The Gaia Ultracool Dwarf Sample – IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs","authors":"W J Cooper, H R A Jones, R L Smart, S L Folkes, J A Caballero, F Marocco, M C Gálvez Ortiz, A J Burgasser, J D Kirkpatrick, L M Sarro, B Burningham, A Cabrera-Lavers, P E Tremblay, C Reylé, N Lodieu, Z H Zhang, N J Cook, J F Faherty, D García-Álvarez, D Montes, D J Pinfield, A S Rajpurohit, J Shi","doi":"10.1093/mnras/stae2102","DOIUrl":"https://doi.org/10.1093/mnras/stae2102","url":null,"abstract":"As part of our comprehensive, ongoing characterisation of the low-mass end of the main sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias to acquire low- and mid-resolution (R≈300 and R≈2500) optical spectroscopy of 53 late-M and L ultracool dwarfs. Most of these objects are known but poorly investigated and lacking complete kinematics. We measured spectral indices, determined spectral types (six of which are new) and inferred effective temperature and surface gravity from BT-Settl synthetic spectra fits for all objects. We were able to measure radial velocities via line centre fitting and cross correlation for 46 objects, 29 of which lacked previous radial velocity measurements. Using these radial velocities in combination with the latest Gaia DR3 data, we also calculated Galactocentric space velocities. From their kinematics, we identified two candidates outside of the thin disc and four in young stellar kinematic groups. Two further ultracool dwarfs are apparently young field objects: 2MASSW J1246467+402715 (L4β), which has a potential, weak lithium absorption line, and G 196–3B (L3β), which was already known as young due to its well-studied primary companion.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"32 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xuejian Shen, Mark Vogelsberger, Josh Borrow, Yongao Hu, Evan Erickson, Rahul Kannan, Aaron Smith, Enrico Garaldi, Lars Hernquist, Takahiro Morishita, Sandro Tacchella, Oliver Zier, Guochao Sun, Anna-Christina Eilers, Hui Wang
We investigate galaxy sizes at redshift z ≳ 6 with the cosmological radiation-magneto-hydrodynamic simulation suite thesan(-hr). These simulations simultaneously capture reionization of the large-scale intergalactic medium and resolved galaxy properties. The intrinsic sizes ($r^{ast }_{1/2}$) of simulated galaxies increase moderately with stellar mass at $M_{ast } lesssim 10^{8}{, rm M_odot }$ and decrease fast at larger masses, resulting in a hump feature at $M_{ast }sim 10^{8}{, rm M_odot }$ that is insensitive to redshift. Low-mass galaxies are in the initial phase of size growth and are better described by a spherical shell model with feedback-driven outflows competing with the cold inflowing gas streams. In contrast, massive galaxies fit better with the disk formation model. They generally experience a phase of rapid compaction and gas depletion, likely driven by internal disk instability rather than external processes. We identify four compact quenched galaxies in the (95.5 cMpc)3 volume of thesan-1 at z ≃ 6 and their quenching follows reaching a characteristic stellar surface density akin to the massive compact galaxies at cosmic noon. Compared to observations, we find that the median UV effective radius ($R^{rm UV}_{rm eff}$) of simulated galaxies is at least three times larger than the observed ones at $M_{ast }lesssim 10^{9}{, rm M_odot }$ or MUV ≳ −20 at 6 ≲ z ≲ 10. The population of compact galaxies ($R^{rm UV}_{rm eff}lesssim 300, {rm pc}$) galaxies at $M_{ast }sim 10^{8}{, rm M_odot }$ is missing in our simulations. This inconsistency persists across many other cosmological simulations with different galaxy formation models and demonstrates the potential of using galaxy morphology to constrain physics of galaxy formation at high redshifts.
{"title":"The thesan project: galaxy sizes during the epoch of reionization","authors":"Xuejian Shen, Mark Vogelsberger, Josh Borrow, Yongao Hu, Evan Erickson, Rahul Kannan, Aaron Smith, Enrico Garaldi, Lars Hernquist, Takahiro Morishita, Sandro Tacchella, Oliver Zier, Guochao Sun, Anna-Christina Eilers, Hui Wang","doi":"10.1093/mnras/stae2156","DOIUrl":"https://doi.org/10.1093/mnras/stae2156","url":null,"abstract":"We investigate galaxy sizes at redshift z ≳ 6 with the cosmological radiation-magneto-hydrodynamic simulation suite thesan(-hr). These simulations simultaneously capture reionization of the large-scale intergalactic medium and resolved galaxy properties. The intrinsic sizes ($r^{ast }_{1/2}$) of simulated galaxies increase moderately with stellar mass at $M_{ast } lesssim 10^{8}{, rm M_odot }$ and decrease fast at larger masses, resulting in a hump feature at $M_{ast }sim 10^{8}{, rm M_odot }$ that is insensitive to redshift. Low-mass galaxies are in the initial phase of size growth and are better described by a spherical shell model with feedback-driven outflows competing with the cold inflowing gas streams. In contrast, massive galaxies fit better with the disk formation model. They generally experience a phase of rapid compaction and gas depletion, likely driven by internal disk instability rather than external processes. We identify four compact quenched galaxies in the (95.5 cMpc)3 volume of thesan-1 at z ≃ 6 and their quenching follows reaching a characteristic stellar surface density akin to the massive compact galaxies at cosmic noon. Compared to observations, we find that the median UV effective radius ($R^{rm UV}_{rm eff}$) of simulated galaxies is at least three times larger than the observed ones at $M_{ast }lesssim 10^{9}{, rm M_odot }$ or MUV ≳ −20 at 6 ≲ z ≲ 10. The population of compact galaxies ($R^{rm UV}_{rm eff}lesssim 300, {rm pc}$) galaxies at $M_{ast }sim 10^{8}{, rm M_odot }$ is missing in our simulations. This inconsistency persists across many other cosmological simulations with different galaxy formation models and demonstrates the potential of using galaxy morphology to constrain physics of galaxy formation at high redshifts.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"12 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J Pelle, C R Argüelles, F L Vieyro, V Crespi, C Millauro, M F Mestre, O Reula, F Carrasco
Current images of the supermassive black hole (SMBH) candidates at the center of our Galaxy and M87 have opened an unprecedented era for studying strong gravity and the nature of relativistic sources. Very-long-baseline interferometry (VLBI) data show images consistent with a central SMBH within General Relativity (GR). However, it is essential to consider whether other well-motivated dark compact objects within GR could produce similar images. Recent studies have shown that dark matter (DM) halos modeled as self-gravitating systems of neutral fermions can harbor very dense fermionic cores at their centers, which can mimic the spacetime features of a black hole (BH). Such dense, horizonless DM cores can satisfy the observational constraints: they can be supermassive and compact and lack a hard surface. We investigate whether such cores can produce similar observational signatures to those of BHs when illuminated by an accretion disk. We compute images and spectra of the fermion cores with a general-relativistic ray tracing technique, assuming the radiation originates from standard α disks, which are self-consistently solved within the current DM framework. Our simulated images possess a central brightness depression surrounded by a ring-like feature, resembling what is expected in the BH scenario. For Milky Way-like halos, the central brightness depressions have diameters down to ∼35 μas as measured from a distance of approximately 8 kpc. Finally, we show that the DM cores do not possess photon rings, a key difference from the BH paradigm, which could help discriminate between the models.
{"title":"Imaging fermionic dark matter cores at the center of galaxies","authors":"J Pelle, C R Argüelles, F L Vieyro, V Crespi, C Millauro, M F Mestre, O Reula, F Carrasco","doi":"10.1093/mnras/stae2152","DOIUrl":"https://doi.org/10.1093/mnras/stae2152","url":null,"abstract":"Current images of the supermassive black hole (SMBH) candidates at the center of our Galaxy and M87 have opened an unprecedented era for studying strong gravity and the nature of relativistic sources. Very-long-baseline interferometry (VLBI) data show images consistent with a central SMBH within General Relativity (GR). However, it is essential to consider whether other well-motivated dark compact objects within GR could produce similar images. Recent studies have shown that dark matter (DM) halos modeled as self-gravitating systems of neutral fermions can harbor very dense fermionic cores at their centers, which can mimic the spacetime features of a black hole (BH). Such dense, horizonless DM cores can satisfy the observational constraints: they can be supermassive and compact and lack a hard surface. We investigate whether such cores can produce similar observational signatures to those of BHs when illuminated by an accretion disk. We compute images and spectra of the fermion cores with a general-relativistic ray tracing technique, assuming the radiation originates from standard α disks, which are self-consistently solved within the current DM framework. Our simulated images possess a central brightness depression surrounded by a ring-like feature, resembling what is expected in the BH scenario. For Milky Way-like halos, the central brightness depressions have diameters down to ∼35 μas as measured from a distance of approximately 8 kpc. Finally, we show that the DM cores do not possess photon rings, a key difference from the BH paradigm, which could help discriminate between the models.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"1 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruth M E Kelly, Denis González-Caniulef, Silvia Zane, Roberto Turolla, Roberto Taverna
Magnetars are neutron stars that host huge, complex magnetic fields which require supporting currents to flow along the closed field lines. This makes magnetar atmospheres different from those of passively cooling neutron stars because of the heat deposited by backflowing charges impinging on the star surface layers. This particle bombardment is expected to imprint the spectral and, even more, the polarisation properties of the emitted thermal radiation. We present solutions for the radiative transfer problem for bombarded plane-parallel atmospheres in the high magnetic field regime. The temperature profile is assumed a priori, and selected in such a way to reflect the varying rate of energy deposition in the slab (from the impinging currents and/or from the cooling crust). We find that thermal X–ray emission powered entirely by the energy released in the atmosphere by the magnetospheric back–bombardment is linearly polarised and X-mode dominated, but its polarisation degree is significantly reduced (down to 10%–50%) when compared with that expected from a standard atmosphere heated only from the cooling crust below. By increasing the fraction of heat flowing in from the crust the polarisation degree of the emergent radiation increases, first at higher energies (∼10 keV) and then in the entire soft X-ray band. We use our models inside a ray-tracing code to derive the expected emission properties as measured by a distant observer and compare our results with recent IXPE observations of magnetar sources.
磁星是中子星，它拥有巨大而复杂的磁场，需要支持电流沿着封闭的磁场线流动。这使得磁星大气层与被动冷却的中子星大气层不同，因为逆流电荷撞击到恒星表层会沉积热量。这种粒子轰击预计会影响辐射热的光谱特性，甚至偏振特性。我们提出了高磁场条件下轰击平面平行大气的辐射传递问题的解决方案。温度曲线是先验假定的，其选择方式反映了板坯中能量沉积的变化率（来自撞击流和/或来自冷却地壳）。我们发现，完全由大气层中磁层反轰击释放的能量驱动的热 X 射线辐射是线性偏振的，以 X 模式为主，但与仅由下面冷却的地壳加热的标准大气层的辐射相比，其偏振程度显著降低（降至 10%-50%）。通过增加从地壳流入的热量，出现的辐射的极化程度会增加，首先是在较高能量（∼10 keV），然后是整个软 X 射线波段。我们在射线追踪代码中使用我们的模型，推导出远处观测者测量到的预期辐射特性，并将我们的结果与最近对磁星源的 IXPE 观测结果进行比较。
{"title":"X-ray polarisation signatures in bombarded magnetar atmospheres","authors":"Ruth M E Kelly, Denis González-Caniulef, Silvia Zane, Roberto Turolla, Roberto Taverna","doi":"10.1093/mnras/stae2163","DOIUrl":"https://doi.org/10.1093/mnras/stae2163","url":null,"abstract":"Magnetars are neutron stars that host huge, complex magnetic fields which require supporting currents to flow along the closed field lines. This makes magnetar atmospheres different from those of passively cooling neutron stars because of the heat deposited by backflowing charges impinging on the star surface layers. This particle bombardment is expected to imprint the spectral and, even more, the polarisation properties of the emitted thermal radiation. We present solutions for the radiative transfer problem for bombarded plane-parallel atmospheres in the high magnetic field regime. The temperature profile is assumed a priori, and selected in such a way to reflect the varying rate of energy deposition in the slab (from the impinging currents and/or from the cooling crust). We find that thermal X–ray emission powered entirely by the energy released in the atmosphere by the magnetospheric back–bombardment is linearly polarised and X-mode dominated, but its polarisation degree is significantly reduced (down to 10%–50%) when compared with that expected from a standard atmosphere heated only from the cooling crust below. By increasing the fraction of heat flowing in from the crust the polarisation degree of the emergent radiation increases, first at higher energies (∼10 keV) and then in the entire soft X-ray band. We use our models inside a ray-tracing code to derive the expected emission properties as measured by a distant observer and compare our results with recent IXPE observations of magnetar sources.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"54 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pavan Uttarkar, Ryan M Shannon, Marcus E Lower, Pravir Kumar, Danny C Price, A T Deller, K Gourdji
Fast Radio Bursts (FRBs) are short-timescale transients of extragalactic origin. The number of detected FRBs has grown dramatically since their serendipitous discovery from archival data. Some FRBs have also been seen to repeat. The polarimetric properties of repeating FRBs show diverse behaviour and, at times, extreme polarimetric morphology, suggesting a complex magneto-ionic circumburst environment for this class of FRB. The polarimetric properties such as circular polarisation behaviour of FRBs are crucial for understanding their surrounding magnetic-ionic environment. The circular polarisation previously observed in some of the repeating FRB sources has been attributed to propagation effects such as generalised Faraday rotation (GFR), where conversion from linear to circular polarisation occurs due to the non-circular modes of transmission in relativistic plasma. The discovery burst from the repeating FRB 20180301A showed significant frequency-dependent circular polarisation behaviour, which was initially speculated to be instrumental due to a sidelobe detection. Here we revisit the properties given the subsequent interferometric localisation of the burst, which indicates that the burst was detected in the primary beam of the Parkes/Murriyang 20-cm multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to model the GFR effect, which is independent of the total polarised flux parameter. Using the GFR model we show that the rotation measure (RM) estimated is two orders of magnitude smaller and opposite sign (∼28 rad m−2) than the previously reported value. We interpret the implication of the circular polarisation on its local magnetic environment and reinterpret its long-term temporal evolution in RM.
快速射电暴（FRBs）是源自河外星系的短时瞬变。自从从档案数据中偶然发现快速射电暴以来，探测到的快速射电暴数量急剧增加。有些 FRB 还出现了重复现象。重复出现的 FRB 的偏振特性表现出多种多样的行为，有时还会出现极端的偏振形态，这表明这类 FRB 处于复杂的磁电离环爆环境中。FRB的圆极化行为等极化特性对于了解其周围的磁电离环境至关重要。以前在一些重复 FRB 源中观测到的圆极化现象被归因于传播效应，如广义法拉第旋转（GFR），由于相对论等离子体中的非圆传输模式，线性极化会转换为圆极化。来自重复FRB 20180301A的发现脉冲串显示了显著的频率依赖性圆极化行为，最初推测这是由于侧射探测造成的。在此，我们重新审视了这一特性，因为随后的干涉定位表明，该爆发是在 Parkes/Murriyang 20 厘米多波束接收器的主波束中探测到的。我们开发了一种贝叶斯斯托克斯-Q、U 和 V 拟合方法来模拟 GFR 效应，它与总偏振通量参数无关。利用 GFR 模型，我们发现估计的旋转量（RM）比之前报告的值小两个数量级，且符号相反（∼28 rad m-2）。我们解释了圆极化对其局部磁环境的影响，并重新解释了其在RM中的长期时间演变。
{"title":"Towards solving the origin of circular polarisation in FRB 20180301A","authors":"Pavan Uttarkar, Ryan M Shannon, Marcus E Lower, Pravir Kumar, Danny C Price, A T Deller, K Gourdji","doi":"10.1093/mnras/stae2159","DOIUrl":"https://doi.org/10.1093/mnras/stae2159","url":null,"abstract":"Fast Radio Bursts (FRBs) are short-timescale transients of extragalactic origin. The number of detected FRBs has grown dramatically since their serendipitous discovery from archival data. Some FRBs have also been seen to repeat. The polarimetric properties of repeating FRBs show diverse behaviour and, at times, extreme polarimetric morphology, suggesting a complex magneto-ionic circumburst environment for this class of FRB. The polarimetric properties such as circular polarisation behaviour of FRBs are crucial for understanding their surrounding magnetic-ionic environment. The circular polarisation previously observed in some of the repeating FRB sources has been attributed to propagation effects such as generalised Faraday rotation (GFR), where conversion from linear to circular polarisation occurs due to the non-circular modes of transmission in relativistic plasma. The discovery burst from the repeating FRB 20180301A showed significant frequency-dependent circular polarisation behaviour, which was initially speculated to be instrumental due to a sidelobe detection. Here we revisit the properties given the subsequent interferometric localisation of the burst, which indicates that the burst was detected in the primary beam of the Parkes/Murriyang 20-cm multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to model the GFR effect, which is independent of the total polarised flux parameter. Using the GFR model we show that the rotation measure (RM) estimated is two orders of magnitude smaller and opposite sign (∼28 rad m−2) than the previously reported value. We interpret the implication of the circular polarisation on its local magnetic environment and reinterpret its long-term temporal evolution in RM.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"50 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P Tang, J J Eldridge, R Meyer, A Lamberts, G Boileau, W G J van Zeist
Galactic white dwarf binaries (WDBs) and black hole binaries (BHBs) will be gravitational wave (GW) sources for LISA. Their detection will provide insights into binary evolution and the evolution of our Galaxy through cosmic history. Here, we make predictions of the expected WDB and BHB population within our Galaxy. We combine predictions of the compact remnant binary populations expected by stellar evolution from the detailed Binary Population and Spectral Synthesis (BPASS) code, with a Milky Way analogue galaxy model from the Feedback In Realistic Environment (FIRE) simulations. We use PhenomA and legwork to simulate LISA observations. Both packages make similar predictions that on average four Galactic BHBs and 673 Galactic WDBs are above the signal-to-noise ratio (SNR) threshold of 7 after a four-year mission. We compare these predictions to earlier results using the Binary Star Evolution (BSE) code with the same FIRE model galaxy. We find that BPASS predicts a few more LISA observable Galactic BHBs and a twentieth of the Galactic WDBs. The differences are due to the different physical assumptions that have gone into the binary evolution calculations. These results indicate that the expected population of compact binaries that LISA will detect depends very sensitively on the binary population synthesis models used and thus observations of the LISA population will provide tight constraints on our modelling of binary stars. Finally, from our synthetic populations we have created mock LISA signals that can be used to test and refine data processing methods of the eventual LISA observations.
银河系白矮星双星（WDBs）和黑洞双星（BHBs）将成为 LISA 的引力波（GW）源。对它们的探测将有助于深入了解双星演化和我们银河系在宇宙历史中的演变。在这里，我们对银河系内预期的 WDB 和 BHB 数量进行了预测。我们将详细的双星种群和光谱合成（BPASS）代码对恒星演化所预期的紧凑残余双星种群的预测与现实环境反馈（FIRE）模拟中的银河系模拟模型结合起来。我们使用 PhenomA 和 legwork 模拟 LISA 观测。两个软件包都做出了类似的预测，即在四年的任务之后，平均有四个银河系黑洞和673个银河系WDB超过信噪比（SNR）阈值7。我们将这些预测结果与早先使用双星演化（BSE）代码和相同的FIRE模型星系得出的结果进行了比较。我们发现，BPASS 预测出了更多的 LISA 可观测到的银河 BHB 和二十分之一的银河 WDB。这些差异是由于双星演化计算中的物理假设不同造成的。这些结果表明，LISA 将探测到的紧凑双星的预期星群非常敏感地取决于所使用的双星星群合成模型，因此对 LISA 星群的观测将为我们的双星建模提供严格的约束。最后，我们根据合成星群创建了模拟 LISA 信号，可用于测试和改进最终 LISA 观测的数据处理方法。
{"title":"Predicting gravitational wave signals from BPASS White Dwarf Binary and Black Hole Binary populations of a Milky Way-like galaxy model for LISA","authors":"P Tang, J J Eldridge, R Meyer, A Lamberts, G Boileau, W G J van Zeist","doi":"10.1093/mnras/stae2154","DOIUrl":"https://doi.org/10.1093/mnras/stae2154","url":null,"abstract":"Galactic white dwarf binaries (WDBs) and black hole binaries (BHBs) will be gravitational wave (GW) sources for LISA. Their detection will provide insights into binary evolution and the evolution of our Galaxy through cosmic history. Here, we make predictions of the expected WDB and BHB population within our Galaxy. We combine predictions of the compact remnant binary populations expected by stellar evolution from the detailed Binary Population and Spectral Synthesis (BPASS) code, with a Milky Way analogue galaxy model from the Feedback In Realistic Environment (FIRE) simulations. We use PhenomA and legwork to simulate LISA observations. Both packages make similar predictions that on average four Galactic BHBs and 673 Galactic WDBs are above the signal-to-noise ratio (SNR) threshold of 7 after a four-year mission. We compare these predictions to earlier results using the Binary Star Evolution (BSE) code with the same FIRE model galaxy. We find that BPASS predicts a few more LISA observable Galactic BHBs and a twentieth of the Galactic WDBs. The differences are due to the different physical assumptions that have gone into the binary evolution calculations. These results indicate that the expected population of compact binaries that LISA will detect depends very sensitively on the binary population synthesis models used and thus observations of the LISA population will provide tight constraints on our modelling of binary stars. Finally, from our synthetic populations we have created mock LISA signals that can be used to test and refine data processing methods of the eventual LISA observations.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"23 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marco A Canossa-Gosteinski, Ana L Chies-Santos, Cristina Furlanetto, Charles J Bonatto, Rodrigo Flores-Freitas, William Schoenell, Michael A Beasley, Roderik Overzier, Basilio X Santiago, Adriano Pieres, Emílio J B Zanatta, Karla A Alamo-Martinez, Eduardo Balbinot, Anna B A Queiroz, Alan Alves-Brito
Understanding faint dwarf galaxies is fundamental to the development of a robust theory of galaxy formation on small scales. Since the discovery of a population of ultra diffuse galaxies (UDGs) rich in globular clusters (GCs) in Coma, an increasing number of studies on low surface brightness dwarf galaxies (LSBds) have been published in recent years. The most massive LSBds have been observed predominantly in groups and clusters, with properties displaying dependence on the environment. In this work, we use deep DECam imaging to systematically identify LSBds and their GC populations around the low-density environment of NGC 3115. We carefully analyse the structure and morphology of 24 candidates, 18 of which are reported for the first time. Most candidates exhibit red colours suggesting a connection between their colour and distance to NGC 3115. We followed up with Gemini GMOS imaging 9 LSBds to properly identify their GC populations. We derive lower limits for the number of GCs associated with each galaxy. Our analysis reveals that they occur around of the same loci of Fornax LSB dwarf GC systems. The relationship between the number of GCs and total mass provides a tool in which, by counting the GCs in these galaxies, we estimate an upper limit for the total mass of these LSB dwarfs, obtaining the mean value of ∼3.3 × 1010 M⊙. Our results align with expectations for dwarf-sized galaxies, particularly regarding the distribution and specific frequency of their GC systems.
{"title":"Low surface brightness dwarf galaxies and their globular cluster populations around the low-density environment of our closest S0 NGC 3115","authors":"Marco A Canossa-Gosteinski, Ana L Chies-Santos, Cristina Furlanetto, Charles J Bonatto, Rodrigo Flores-Freitas, William Schoenell, Michael A Beasley, Roderik Overzier, Basilio X Santiago, Adriano Pieres, Emílio J B Zanatta, Karla A Alamo-Martinez, Eduardo Balbinot, Anna B A Queiroz, Alan Alves-Brito","doi":"10.1093/mnras/stae2161","DOIUrl":"https://doi.org/10.1093/mnras/stae2161","url":null,"abstract":"Understanding faint dwarf galaxies is fundamental to the development of a robust theory of galaxy formation on small scales. Since the discovery of a population of ultra diffuse galaxies (UDGs) rich in globular clusters (GCs) in Coma, an increasing number of studies on low surface brightness dwarf galaxies (LSBds) have been published in recent years. The most massive LSBds have been observed predominantly in groups and clusters, with properties displaying dependence on the environment. In this work, we use deep DECam imaging to systematically identify LSBds and their GC populations around the low-density environment of NGC 3115. We carefully analyse the structure and morphology of 24 candidates, 18 of which are reported for the first time. Most candidates exhibit red colours suggesting a connection between their colour and distance to NGC 3115. We followed up with Gemini GMOS imaging 9 LSBds to properly identify their GC populations. We derive lower limits for the number of GCs associated with each galaxy. Our analysis reveals that they occur around of the same loci of Fornax LSB dwarf GC systems. The relationship between the number of GCs and total mass provides a tool in which, by counting the GCs in these galaxies, we estimate an upper limit for the total mass of these LSB dwarfs, obtaining the mean value of ∼3.3 × 1010 M⊙. Our results align with expectations for dwarf-sized galaxies, particularly regarding the distribution and specific frequency of their GC systems.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"24 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Courtney L Crawford, Nikita Nikultsev, Geoffrey C Clayton, Patrick Tisserand, Jamie Soon, May G Pedersen
Hydrogen-deficient Carbon (HdC) stars are rare, low-mass, chemically peculiar, supergiant variables believed to be formed by a double white dwarf (DWD) merger, specifically of a Carbon/Oxygen- (CO-) and a Helium-white dwarf (He-WD). They consist of two subclasses– the dust-producing R Coronae Borealis (RCB) variables and their dustless counterparts the dustless HdCs (dLHdCs). Additionally, there is another, slightly cooler set of potentially related carbon stars, the DY Persei type variables which have some, but not conclusive, evidence of Hydrogen-deficiency. Recent works have begun to explore the relationship between these three classes of stars, theorizing that they share an evolutionary pathway (a DWD merger) but come from different binary populations, specifically different total masses (Mtot) and mass ratios (q). In this work, we use the mesa modelling framework that has previously been used to model RCB stars and vary the merger parameters, Mtot and q, to explore how those parameters affect the abundances, temperatures, and luminosities of the resultant post-merger stars. We find that lower Mtot and larger q’s both decrease the luminosity and temperatures of post-merger models to the region of the Hertzsprung-Russell Diagram populated by the dLHdCs. These lower Mtot and larger q models also have smaller oxygen isotopic ratios (16O/18O) which is consistent with recent observations of dLHdCs compared to RCBs. None of the models generated in this work can explain the existence of the DY Persei type variables, however this may arise from the assumed metallicity of the models.
缺氢碳星（HdC）是一种罕见的、低质量、化学性质奇特的超巨星变星，据信是由双白矮星（DWD）合并形成的，特别是由碳/氧白矮星（CO-）和氦白矮星（He-WD）合并形成的。它们包括两个亚类--产生尘埃的北冕座变星（RCB）和无尘的对应变星--无尘白矮星（dLHdCs）。此外，还有一组温度稍低的潜在相关碳星--DY Persei型变星，它们有一些缺氢的证据，但并不确凿。最近的研究已经开始探索这三类恒星之间的关系，理论上它们有着共同的演化路径（DWD合并），但来自不同的双星群，具体来说就是不同的总质量（Mtot）和质量比（q）。在这项工作中，我们使用了之前用于模拟 RCB 恒星的网格建模框架，并改变了合并参数 Mtot 和 q，以探索这些参数如何影响合并后恒星的丰度、温度和光度。我们发现，较低的Mtot和较大的q都会降低合并后模型的光度和温度，使其处于由dLHdCs填充的赫兹普朗-罗素图区域。这些较低的Mtot和较大的q模型的氧同位素比（16O/18O）也较小，这与最近观测到的dLHdCs与RCBs相比是一致的。这项工作中生成的模型都无法解释 DY Persei 型变星的存在，不过这可能是由于模型的假定金属性造成的。
{"title":"Modelling hydrogen-deficient carbon stars in MESA— The effects of total mass and mass ratio","authors":"Courtney L Crawford, Nikita Nikultsev, Geoffrey C Clayton, Patrick Tisserand, Jamie Soon, May G Pedersen","doi":"10.1093/mnras/stae2149","DOIUrl":"https://doi.org/10.1093/mnras/stae2149","url":null,"abstract":"Hydrogen-deficient Carbon (HdC) stars are rare, low-mass, chemically peculiar, supergiant variables believed to be formed by a double white dwarf (DWD) merger, specifically of a Carbon/Oxygen- (CO-) and a Helium-white dwarf (He-WD). They consist of two subclasses– the dust-producing R Coronae Borealis (RCB) variables and their dustless counterparts the dustless HdCs (dLHdCs). Additionally, there is another, slightly cooler set of potentially related carbon stars, the DY Persei type variables which have some, but not conclusive, evidence of Hydrogen-deficiency. Recent works have begun to explore the relationship between these three classes of stars, theorizing that they share an evolutionary pathway (a DWD merger) but come from different binary populations, specifically different total masses (Mtot) and mass ratios (q). In this work, we use the mesa modelling framework that has previously been used to model RCB stars and vary the merger parameters, Mtot and q, to explore how those parameters affect the abundances, temperatures, and luminosities of the resultant post-merger stars. We find that lower Mtot and larger q’s both decrease the luminosity and temperatures of post-merger models to the region of the Hertzsprung-Russell Diagram populated by the dLHdCs. These lower Mtot and larger q models also have smaller oxygen isotopic ratios (16O/18O) which is consistent with recent observations of dLHdCs compared to RCBs. None of the models generated in this work can explain the existence of the DY Persei type variables, however this may arise from the assumed metallicity of the models.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"4 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fahad Nasir, Prakash Gaikwad, Frederick B Davies, James S Bolton, Ewald Puchwein, Sarah E I Bosman
Unveiling the thermal history of the intergalactic medium (IGM) at 4 ≤ z ≤ 5 holds the potential to reveal early onset He ii reionization or lingering thermal fluctuations from H i reionization. We set out to reconstruct the IGM gas properties along simulated Lyman-alpha forest data on pixel-by-pixel basis, employing deep neural networks. Our approach leverages the Sherwood-Relics simulation suite, consisting of diverse thermal histories, to generate mock spectra. Our convolutional and residual networks with likelihood metric predicts the Lyα optical depth-weighted density or temperature for each pixel in the Lyα forest skewer. We find that our network can successfully reproduce IGM conditions with high fidelity across range of instrumental signal-to-noise. These predictions are subsequently translated into the temperature-density plane, facilitating the derivation of reliable constraints on thermal parameters. This allows us to estimate temperature at mean cosmic density, T0 , with one sigma confidence, $delta {rm T_{rm 0}},$≲ 1000K, using only one 20h−1cMpc sightline (Δz ≃ 0.04) with a typical reionization history. Existing studies utilize redshift pathlength comparable to Δz ≃ 4 for similar constraints. We can also provide more stringent constraints on the slope (1σ confidence interval, δγ ≲ 0.1) of the IGM temperature-density relation as compared to other traditional approaches. We test the reconstruction on a single high signal-to-noise observed spectrum (20h−1cMpc segment), and recover thermal parameters consistent with current measurements. This machine learning approach has the potential to provide accurate yet robust measurements of IGM thermal history at the redshifts in question.
揭示 4 ≤ z ≤ 5 星系间介质（IGM）的热历史，有可能揭示早期开始的 He ii 再电离或 H i 再电离的残余热波动。我们开始利用深度神经网络，沿着模拟的莱曼-阿尔法森林数据，逐像素地重建IGM气体特性。我们的方法利用由不同热历史组成的 Sherwood-Relics 模拟套件来生成模拟光谱。我们的卷积和残差网络利用似然度量预测了 Lyα 森林串联图中每个像素的 Lyα 光学深度加权密度或温度。我们发现，在仪器信噪比范围内，我们的网络能够成功地高保真地再现 IGM 条件。这些预测随后被转化为温度-密度平面，从而有助于推导出可靠的热参数约束。这使得我们能够仅利用一条具有典型再电离历史的20h-1cMpc视线（Δz ≃0.04），以一个西格玛的置信度（$delta {rm T_{rm 0}}）来估计平均宇宙密度T0的温度。现有的研究利用与Δz ≃ 4相当的红移路径长度来获得类似的约束条件。与其他传统方法相比，我们还能对IGM温度-密度关系的斜率（1σ置信区间，δγ ≲0.1）提供更严格的约束。我们在单个高信噪比观测光谱（20h-1cMpc 段）上测试了重构，恢复的热参数与当前的测量结果一致。这种机器学习方法有可能为相关红移下的IGM热历史提供准确而稳健的测量结果。
{"title":"Deep learning the intergalactic medium using lyman-alpha forest at 4 ≤ z ≤ 5","authors":"Fahad Nasir, Prakash Gaikwad, Frederick B Davies, James S Bolton, Ewald Puchwein, Sarah E I Bosman","doi":"10.1093/mnras/stae2153","DOIUrl":"https://doi.org/10.1093/mnras/stae2153","url":null,"abstract":"Unveiling the thermal history of the intergalactic medium (IGM) at 4 ≤ z ≤ 5 holds the potential to reveal early onset He ii reionization or lingering thermal fluctuations from H i reionization. We set out to reconstruct the IGM gas properties along simulated Lyman-alpha forest data on pixel-by-pixel basis, employing deep neural networks. Our approach leverages the Sherwood-Relics simulation suite, consisting of diverse thermal histories, to generate mock spectra. Our convolutional and residual networks with likelihood metric predicts the Lyα optical depth-weighted density or temperature for each pixel in the Lyα forest skewer. We find that our network can successfully reproduce IGM conditions with high fidelity across range of instrumental signal-to-noise. These predictions are subsequently translated into the temperature-density plane, facilitating the derivation of reliable constraints on thermal parameters. This allows us to estimate temperature at mean cosmic density, T0 , with one sigma confidence, $delta {rm T_{rm 0}},$≲ 1000K, using only one 20h−1cMpc sightline (Δz ≃ 0.04) with a typical reionization history. Existing studies utilize redshift pathlength comparable to Δz ≃ 4 for similar constraints. We can also provide more stringent constraints on the slope (1σ confidence interval, δγ ≲ 0.1) of the IGM temperature-density relation as compared to other traditional approaches. We test the reconstruction on a single high signal-to-noise observed spectrum (20h−1cMpc segment), and recover thermal parameters consistent with current measurements. This machine learning approach has the potential to provide accurate yet robust measurements of IGM thermal history at the redshifts in question.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"33 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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