Publications of the Astronomical Society of Australia最新文献

{"title":"Deblending overlapping galaxies in DECaLS using Transformer-Based algorithm: a method combining multiple bands and data types","authors":"Ran Zhang, Meng Liu, Zhenping Yi, Hao Yuan, Zechao Yang, Yude Bu, Xiaoming Kong, Chenglin Jia, Yuchen Bi, Yusheng Zhang","doi":"10.1017/pasa.2024.16","DOIUrl":"https://doi.org/10.1017/pasa.2024.16","url":null,"abstract":"In large-scale galaxy surveys, particularly deep ground-based photometric studies, galaxy blending was inevitable. Such blending posed a potential primary systematic uncertainty for upcoming surveys. Current deblenders predominantly depended on analytical modeling of galaxy profiles, facing limitations due to inflexible and imprecise models. We presented a novel approach, using a U-net structured Transformer-based network for deblending astronomical images, which we term the <jats:italic>CAT-deblender</jats:italic>. It was trained using both RGB and the <jats:italic>grz</jats:italic>-band images, spanning two distinct data formats present in the Dark Energy Camera Legacy Survey (<jats:italic>DECaLS</jats:italic>) database, including galaxies with diverse morphologies in the training dataset. Our method necessitated only the approximate central coordinates of each target galaxy, sourced from galaxy detection, bypassing assumptions on neighboring source counts. Post-deblending, our RGB images retained a high signal-to-noise peak, consistently showing superior structural similarity against ground truth. For multi-band images, the ellipticity of central galaxies and median reconstruction error for <jats:italic>r</jats:italic>-band consistently lie within ±0.025 to ±0.25, revealing minimal pixel residuals. In our comparison of deblending capabilities focused on flux recovery, our model showed a mere 1% error in magnitude recovery for quadruply blended galaxies, significantly outperforming SExtractor’s higher error rate of 4.8%. Furthermore, by cross-matching with the publicly accessible overlapping galaxy catalogs from the <jats:italic>DECaLS</jats:italic> database, we successfully deblended 433 overlapping galaxies. Moreover, we’ve demonstrated effective deblending of 63,733 blended galaxy images, randomly chosen from the <jats:italic>DECaLS</jats:italic> database.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140166158","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}

{"title":"HINORA, a method for detecting ring-like structures in 3D point distributions I: application to the Local Volume Galaxy catalogue","authors":"Edward Olex, Alexander Knebe, Noam I. Libeskind, Dmitry I. Makarov, Stefan Gottlöber","doi":"10.1017/pasa.2024.21","DOIUrl":"https://doi.org/10.1017/pasa.2024.21","url":null,"abstract":"We present a new method – called HINORA (HIgh-NOise RANdom SAmple Consensus) – for the identification of regular structures in 3D point distributions. Motivated by the possible existence of the so-called Council of Giants, i.e. a ring of twelve massive galaxies surrounding the Local Group in the Local Sheet with a radius of 3.75 Mpc, we apply HINORA to the Local Volume Galaxy catalogue confirming its existence. When varying the lower limit of K-band luminosity of the galaxy entering the catalogue, we further report on the existence of another ring-like structure in the Local Volume that now contains the MilkyWay and M31. However, this newly found structure is dominated by low-mass (satellite) galaxies. While we here simply present the novel method as well as its first application to observational data, follow-up work using numerical simulations of cosmic structure formation shall shed light into the origin of such regular patterns in the galaxy distribution. Further, the method is equally suited to identify similar (or even different) structures in various kinds of astrophysical data (e.g. locating the actual ‘baryonic-acoustic oscillation spheres’ in galaxy redshift surveys).","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140166030","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}

{"title":"Predicting the Scaling Relations between the Dark Matter Halo Mass and Observables from Generalised Profiles I: Kinematic Tracers","authors":"A. Sullivan, C. Power, C. Bottrell","doi":"10.1017/pasa.2024.18","DOIUrl":"https://doi.org/10.1017/pasa.2024.18","url":null,"abstract":"We investigate the relationship between a dark matter halo’s mass profile and measures of the velocity dispersion of kinematic tracers within its gravitational potential. By predicting the scaling relation of the halo mass with the aperture velocity dispersion, <jats:italic>M</jats:italic><jats:sub>vir</jats:sub> – σ<jats:sub>ap</jats:sub>, we present the expected form and dependence of this halo mass tracer on physical parameters within our analytic halo model: parameterized by the halo’s negative inner logarithmic density slope, α, its concentration parameter, <jats:italic>c</jats:italic>, and its velocity anisotropy parameter, β. For these idealised halos, we obtain a general solution to the Jeans equation, which is projected over the line of sight and averaged within an aperture to form the corresponding aperture velocity dispersion profile. Through dimensional analysis, the <jats:italic>M</jats:italic><jats:sub>vir</jats:sub> – σap scaling relation is devised explicitly in terms of analytical bounds for these aperture velocity dispersion profiles: allowing constraints to be placed on this relation for motivated parameter choices. We predict the <jats:italic>M</jats:italic><jats:sub>200</jats:sub> – σ<jats:sub>ap</jats:sub> and <jats:italic>M</jats:italic><jats:sub>500</jats:sub> – σ<jats:sub>ap</jats:sub> scaling relations, each with an uncertainty of 60.5% and 56.2%, respectively. These halo mass estimates are found to be weakly sensitive to the halo’s concentration and mass scale, and most sensitive to the size of the aperture radius in which the aperture velocity dispersion is measured, the maximum value for the halo’s inner slope, and the minimum and maximum values of the velocity anisotropy. Our results show that a halo’s structural and kinematic profiles impose only a minor uncertainty in estimating its mass. Consequently, spectroscopic surveys aimed at constraining the halo mass using kinematic tracers can focus on characterising other, more complex sources of uncertainty and observational systematics.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140169600","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}

{"title":"s-process Enriched Evolved Binaries in the Galaxy and the Magellanic Clouds","authors":"Meghna Menon, Devika Kamath, Maksym Mohorian, Hans Van Winckel, Paolo Ventura","doi":"10.1017/pasa.2024.19","DOIUrl":"https://doi.org/10.1017/pasa.2024.19","url":null,"abstract":"Post-asymptotic giant branch stars (post-AGB) in binary systems, with typical orbital periods between ∼100 to ∼1000 days, result from a poorly understood interaction that terminates their precursory AGB phase. The majority of these binaries display a photospheric anomaly called ‘chemical depletion’, thought to arise froman interaction between the circumbinary disc and the post-AGB star, leading to the reaccretion of pure gas onto the star, devoid of refractory elements due to dust formation. In this paper, we focus on a subset of chemically peculiar binary post-AGBs in the Galaxy and the Magellanic Clouds (MCs). Our detailed stellar parameter and chemical abundance analysis utilising high-resolution optical spectra from VLT+UVES revealed that our targets span a <jats:italic>T</jats:italic><jats:sub>eff</jats:sub> of 4900 - 7250K and [Fe/H] of -0.5 - -1.57 dex. Interestingly, these targets exhibit a carbon ([C/Fe] ranging from 0.5 - 1.0 dex, dependant on metallicity) and <jats:italic>s</jats:italic>-process enrichment ([s/Fe]≥1dex) contrary to the commonly observed chemical depletion pattern. Using spectral energy distribution (SED) fitting and period-luminosity-colour (PLC) relation methods, we determine the luminosity of the targets (2700 – 8300 L<jats:sub>⊙</jats:sub>), which enables confirmation of their evolutionary phase and estimation of initial masses (as a function of metallicity) (1 - 2.5M<jats:sub>⊙</jats:sub>). In conjunction with predictions from dedicated ATON stellar evolutionary models, our results indicate a predominant intrinsic enrichment of carbon and <jats:italic>s</jats:italic>-process elements in our binary post-AGB targets. We qualitatively rule out extrinsic enrichment and inherited <jats:italic>s</jats:italic>-process enrichment from the host galaxy as plausible explanations for the observed overabundances. Our chemically peculiar subset of intrinsic carbon and <jats:italic>s</jats:italic>-process enriched binary post-AGBs also hints at potential variation in the efficiency of chemical depletion between stars with C-rich and O-rich circumbinary disc chemistries. However, critical observational studies of circumbinary disc chemistry, along with specific condensation temperature estimates in C-rich environments, are necessary to address gaps in our current understanding of disc-binary interactions inducing chemical depletion in binary post-AGB systems.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140166025","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}

{"title":"Calculation of Astrophysical Reaction Rate and Uncertainty for T(d,n)4He using Bayesian Statistical Approach","authors":"Seyyed Soheil Esmaeili, Abbas Ghasemizad, Omid Naserghodsi","doi":"10.1017/pasa.2024.15","DOIUrl":"https://doi.org/10.1017/pasa.2024.15","url":null,"abstract":"One of the best methods to investigate and calculate a desired quantity using available limited data is the Bayesian statistical method, which has been recently entered the field of nuclear astrophysics and can be used to evaluate the astrophysical S-factors, the cross sections and, as a result, the nuclear reaction rates of Big Bang Nucleosynthesis. This study tries to calculate the astrophysical S-factor and the rate of reaction T(d,n)<jats:sup>4</jats:sup>He as an important astrophysical reaction with the help of this method in energies lower that electron repulsive barrier, and for this purpose, it uses the R-Software, which leads to improved results in comparison with the non-Bayesian methods for the mentioned reaction rate.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140125678","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}

{"title":"Are Odd Radio Circles phoenixes of powerful radio galaxies?","authors":"S. S. Shabala, P. M. Yates-Jones, L. A. Jerrim, R. J. Turner, M. G. H. Krause, R. P. Norris, B. S. Koribalski, M. Filipović, L. Rudnick, C. Power, R. M. Crocker","doi":"10.1017/pasa.2024.11","DOIUrl":"https://doi.org/10.1017/pasa.2024.11","url":null,"abstract":"Odd Radio Circles (ORCs) are a class of low surface brightness, circular objects approximately one arcminute in diameter. ORCs were recently discovered in the Australian Square Kilometre Array Pathfinder (ASKAP) data, and subsequently confirmed with follow-up observations on other instruments, yet their origins remain uncertain. In this paper, we suggest that ORCs could be remnant lobes of powerful radio galaxies, re-energised by the passage of a shock. Using relativistic hydrodynamic simulations with synchrotron emission calculated in post-processing, we show that buoyant evolution of remnant radio lobes is alone too slow to produce the observed ORC morphology. However, the passage of a shock can produce both filled and edge-brightnened ORC-like morphologies for a wide variety of shock and observing orientations. Circular ORCs are predicted to have host galaxies near the geometric centre of the radio emission, consistent with observations of these objects. Significantly offset hosts are possible for elliptical ORCs, potentially causing challenges for accurate host galaxy identification. Observed ORC number counts are broadly consistent with a paradigm in which moderately powerful radio galaxies are their progenitors.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140045394","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}

{"title":"Early Accretion Onset in Long-Period Isolated Pulsars","authors":"M.D. Afonina, A.V. Biryukov, S.B. Popov","doi":"10.1017/pasa.2024.12","DOIUrl":"https://doi.org/10.1017/pasa.2024.12","url":null,"abstract":"We model long-term magneto-rotational evolution of isolated neutron stars with long initial spin periods. This analysis is motivated by the recent discovery of young long-period neutron stars observed as periodic radio sources: PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. Our calculations demonstrate that for realistically rapid spin-down during the propeller stage isolated neutron stars with velocities ≲ 100 km s–1 and assumed long initial spin periods can reach the stage of accretion from the interstellar medium within at most a few billion years as they are born already at the propeller stage or sufficiently close to the critical period of the ejector-propeller transition. If neutron stars with long initial spin periods form a relatively large fraction of all Galactic neutron stars then the number of isolated accretors is substantially larger than it has been predicted by previous studies.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140007414","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}

{"title":"DARK SAGE: Next-generation semi-analytic galaxy evolution with multidimensional structure and minimal free parameters","authors":"Adam R. H. Stevens, Manodeep Sinha, Alexander Rohl, Mawson W. Sammons, Boryana Hadzhiyska, César Hernández-Aguayo, Lars Hernquist","doi":"10.1017/pasa.2024.14","DOIUrl":"https://doi.org/10.1017/pasa.2024.14","url":null,"abstract":"After more than five years of development, we present a new version of Dark Sage, a semi-analytic model (SAM) of galaxy formation that breaks the mould for models of its kind. Included among the major changes is an overhauled treatment of stellar feedback that is derived from energy conservation, operates on local scales, affects gas gradually over time rather than instantaneously, and predicts a mass-loading factor for every galaxy. Building on the model’s resolved angularmomentum structure of galaxies, we now consider the heating of stellar discs, delivering predictions for disc structure both radially and vertically. We add a further dimension to stellar discs by tracking the distribution of stellar ages in each annulus. Each annulus–age bin has its own velocity dispersion and metallicity evolved in the model. This allows Dark Sage to make structural predictions for galaxies that previously only hydrodynamic simulations could. We present the model as run on the merger trees of the highest-resolution gravity-only simulation of the MillenniumTNG suite. Despite its additional complexity relative to other SAMs, Dark Sage only has three free parameters, the least of any SAM, which we calibrate exclusively against the cosmic star formation history and the <jats:italic>z</jats:italic>=0 stellar and Hi mass functions using a particle-swarm optimisation method. The Dark Sage codebase, written in C and python, is publicly available at <jats:uri xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"https://github.com/arhstevens/DarkSage\">https://github.com/arhstevens/DarkSage</jats:uri>.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140007413","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}

{"title":"EMU/GAMA: A Technique for Detecting Active Galactic Nuclei in Low Mass Systems","authors":"Jahang Prathap, Andrew M. Hopkins, Aaron S. G. Robotham, Sabine Bellstedt, José Afonso, Ummee T. Ahmed, Maciej Bilicki, Malcolm N. Bremer, Sarah Brough, Michael J. I. Brown, Yjan Gordon, Benne W. Holwerda, Denis Leahy, Ángel R. López-Sánchez, Joshua R. Marvil, Tamal Mukherjee, Isabella Prandoni, Stanislav S. Shabala, Tessa Vernstrom, Tayyaba Zafar","doi":"10.1017/pasa.2024.9","DOIUrl":"https://doi.org/10.1017/pasa.2024.9","url":null,"abstract":"We propose a new method for identifying active galactic nuclei (AGN) in low mass (M<jats:sub>*</jats:sub> ≤ 10<jats:sup>10</jats:sup>M<jats:sub>⊙</jats:sub>) galaxies. This method relies on spectral energy distribution (SED) fitting to identify galaxies whose radio flux density has an excess over that expected from star formation alone. Combining data in the Galaxy and Mass Assembly (GAMA) G23 region from GAMA, Evolutionary Map of the Universe (EMU) early science observations, andWide-field Infrared Survey Explorer (WISE), we compare this technique with a selection of different AGN diagnostics to explore the similarities and differences in AGN classification. We find that diagnostics based on optical and near-infrared criteria (the standard BPT diagram, the WISE colour criterion, and the mass-excitation, or MEx diagram) tend to favour detection of AGN in high mass, high luminosity systems, while the “P<jats:sc>ro</jats:sc>S<jats:sc>pect</jats:sc>” SED fitting tool can identify AGN efficiently in low mass systems. We investigate an explanation for this result in the context of proportionally lower mass black holes in lower mass galaxies compared to higher mass galaxies and differing proportions of emission from AGN and star formation dominating the light at optical and infrared wavelengths as a function of galaxy stellar mass. We conclude that SED-derived AGN classification is an efficient approach to identify low mass hosts with low radio luminosity AGN.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139925851","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}

{"title":"Plane Polarization in Comptonization process : a Monte Carlo study","authors":"Nagendra Kumar","doi":"10.1017/pasa.2024.8","DOIUrl":"https://doi.org/10.1017/pasa.2024.8","url":null,"abstract":"High energies emissions observed in X-ray binaries (XRBs), active galactic nuclei (AGNs) are linearly polarized. The prominent mechanism for X-ray is the Comptonization process. We revisit the theory for polarization in Compton scattering with unpolarized electrons, and note that the (k×k′)-coordinate (in which, (k×k<jats:sup>′<jats:sup>) acts as a z-axis, here k and k<jats:sup>′</jats:sup> are incident and scattered photon momentum respectively) is more convenient to describe it. Interestingly, for a fixed scattering plane the degree of polarization PD after single scattering for random oriented low-energy unpolarized incident photons is ~0.3. At the scattering angle θ = 0 orθ≡ [0,25◦], the modulation curve of k</jats:sup>′</jats:sup> exhibits the same PD and PA (angle of polarization) of k, and even the distribution of projection of electric vector of k<jats:sup>′</jats:sup> (k<jats:sup>′</jats:sup>e) on perpendicular plane to the k indicates same (so, an essential criteria for detector designing). We compute the polarization state in Comptonization process using Monte Carlo methods with considering a simple spherical corona. We obtain the PD of emergent photons as a function of =-angle (or alternatively, the disk inclination angle i) on a meridian plane (i.e., the laws of darkening, formulated by Chandrasekhar, 1946) after single scattering with unpolarized incident photons. To explore the energy dependency we consider a general spectral parameter set corresponding to hard and soft states of XRBs, we find that for average scattering no. 〈N<jats:sub>sc</jats:sub>〉 ~1.1 the PD is independent of energy and PA ~ 90◦ (k<jats:sup>′</jats:sup><jats:sub>e</jats:sub> is parallel to the disk plane), and for hNsci ~5 the PD value is maximum for i = 45◦. We also compare the results qualitatively with observation of IXPE for five sources.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139589090","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}