Monthly Notices of the Royal Astronomical Society最新文献_第2页

Uncovering Tidal Treasures: Automated Classification of faint tidal features in DECaLS Data 发现潮汐宝藏：DECaLS 数据中微弱潮汐特征的自动分类

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2169

Alexander J Gordon, Annette M N Ferguson, Robert G Mann

{"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}

引用次数: 0

The Gaia Ultracool Dwarf Sample – IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs 盖亚超冷矮星样本 - IV.盖亚晚M矮星和L矮星的 GTC/OSIRIS 光学光谱

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2102

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

{"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}

引用次数: 0

The thesan project: galaxy sizes during the epoch of reionization Thesan 项目：再电离时代的星系大小

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2156

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

{"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}

引用次数: 0

Imaging fermionic dark matter cores at the center of galaxies 成像星系中心的费米暗物质核心

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2152

J Pelle, C R Argüelles, F L Vieyro, V Crespi, C Millauro, M F Mestre, O Reula, F Carrasco

{"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}

引用次数: 0

X-ray polarisation signatures in bombarded magnetar atmospheres 轰击磁星大气中的 X 射线极化特征

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2163

Ruth M E Kelly, Denis González-Caniulef, Silvia Zane, Roberto Turolla, Roberto Taverna

{"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}

引用次数: 0

Towards solving the origin of circular polarisation in FRB 20180301A 努力解决 FRB 20180301A 中圆形极化的起源问题

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2159

Pavan Uttarkar, Ryan M Shannon, Marcus E Lower, Pravir Kumar, Danny C Price, A T Deller, K Gourdji

{"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}

引用次数: 0

Predicting gravitational wave signals from BPASS White Dwarf Binary and Black Hole Binary populations of a Milky Way-like galaxy model for LISA 为 LISA 预测类似银河系模型的 BPASS 白矮星双星和黑洞双星群体的引力波信号

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2154

P Tang, J J Eldridge, R Meyer, A Lamberts, G Boileau, W G J van Zeist

{"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}

引用次数: 0

Low surface brightness dwarf galaxies and their globular cluster populations around the low-density environment of our closest S0 NGC 3115 距离我们最近的 S0 NGC 3115 低密度环境周围的低表面亮度矮星系及其球状星团群

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2161

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

{"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}

引用次数: 0

Modelling hydrogen-deficient carbon stars in MESA— The effects of total mass and mass ratio 模拟 MESA 中的缺氢碳星--总质量和质量比的影响

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2149

Courtney L Crawford, Nikita Nikultsev, Geoffrey C Clayton, Patrick Tisserand, Jamie Soon, May G Pedersen

{"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}

引用次数: 0

Deep learning the intergalactic medium using lyman-alpha forest at 4 ≤ z ≤ 5 利用 4 ≤ z ≤ 5 的莱曼-阿尔法森林深度学习星系间介质

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-18 DOI: 10.1093/mnras/stae2153

Fahad Nasir, Prakash Gaikwad, Frederick B Davies, James S Bolton, Ewald Puchwein, Sarah E I Bosman

{"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}

引用次数: 0