Publications of the Astronomical Society of Australia最新文献

{"title":"Increasing the detectability of long-period and nulling pulsars in next-generation pulsar surveys","authors":"Garvit Grover, Ramesh Bhat, Samuel McSweeney","doi":"10.1017/pasa.2024.67","DOIUrl":"https://doi.org/10.1017/pasa.2024.67","url":null,"abstract":"<p>Recent discoveries of multiple long-period pulsars (periods <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240917131836263-0508:S1323358024000675:S1323358024000675_inline1.png\"><span data-mathjax-type=\"texmath\"><span>${sim}10,$</span></span></img></span></span>s or larger) are starting to challenge the conventional notion that coherent radio emission cannot be produced by objects that are below the many theorised death lines. Many of the past pulsar surveys and software have been prone to selection effects that restricted their sensitivities towards long-period and sporadically emitting objects. Pulsar surveys using new-generation low-frequency facilities are starting to employ longer dwell times, which makes them significantly more sensitive in detecting long-period or nulling pulsars. There have also been software advancements to aid more sensitive searches towards long-period objects. Furthermore, recent discoveries suggest that nulling may be a key aspect of the long-period pulsar population. We simulate both long-period and nulling pulsar signals, using the Southern-sky MWA Rapid Two-meter (SMART) survey data as reference and explore the detection efficacy of popular search methods such as the fast Fourier transform (FFT), fast-folding algorithm (FFA) and single pulse search (SPS). For FFT-based search and SPS, we make use of the PRESTO implementation, and for FFA we use RIPTIDE. We find RIPTIDE’s FFA to be more sensitive; however, it is also the slowest algorithm. PRESTO’s FFT, although faster than others, also shows some unexpected inaccuracies in detection properties. SPS is highly sensitive to long-period and nulling signals, but only for pulses with high intrinsic signal-to-noise ratios. We use these findings to inform current and future pulsar surveys that aim to uncover a large population of long-period or nulling objects and comment on how to make optimal use of these methods in unison.</p>","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"198 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267468","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":"Multi-band optical variability on diverse timescales of blazar 1E 1458.8+2249","authors":"Aykut Özdönmez, Murat Tekkeşinoğlu","doi":"10.1017/pasa.2024.59","DOIUrl":"https://doi.org/10.1017/pasa.2024.59","url":null,"abstract":"This study presents an analysis of the optical variability of the blazar 1E 1458.8+2249 on diverse timescales using multi-band observations, including observations in the optical BVRI bands carried out with the T60 and T100 telescopes from 2020 to 2023 and ZTF gri data from 2018 to 2023. On seven nights, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test, but no significant variability was found. The long-term light curve shows a variability behaviour in the optical BVRI bands with amplitudes of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline1.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>100% and in the gri bands with amplitudes of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline2.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>120%, including short-term variability of up to <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline3.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>1.1 mag. Correlation analysis revealed a strong correlation between the optical multi-band emissions without any time lag. From 62 nightly spectral energy distributions, we obtained spectral indices between 0.826 and 1.360, with an average of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline4.png\"/> <jats:tex-math> $1.128pm0.063$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. The relationships of both spectral indices and colour with respect to brightness indicate a mild BWB trend throughout the observation period, both intraday and long-term. We also performed a periodicity search using the weighted wavelet Z-transform and Lomb–Scargle methods. A recurrent optical emission pattern with a quasi-periodicity of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline5.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>340 days is detected in the combined V- and <jats:italic>R</jats:italic>-band light curves. The observational results indicate that the blazar 1E 1458.8+2249 has a complex variability, while emphasising the need for future observations to unravel its underlying mechanisms.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"1 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267617","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":"Imaging pulsar census of the galactic plane using MWA VCS data","authors":"S. Sett, M. Sokolowski, E. Lenc, N.D.R. Bhat","doi":"10.1017/pasa.2024.62","DOIUrl":"https://doi.org/10.1017/pasa.2024.62","url":null,"abstract":"Traditional pulsar surveys have primarily employed time-domain periodicity searches. However, these methods are susceptible to effects like scattering, eclipses, and orbital motion. At lower radio frequencies (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline1.png\"/> <jats:tex-math> $lesssim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>300 MHz), factors such as dispersion measure and pulse broadening become more prominent, reducing the detection sensitivity. On the other hand, image domain searches for pulsars are not limited by these effects and can extend the parameter space to regions inaccessible to traditional search techniques. Therefore, we have developed a pipeline to form 1-second full Stokes images from offline correlated high time-resolution data from the Murchison Widefield Array (MWA). This led to the development of image-based methodologies to identify new pulsar candidates. In this paper, we applied these methodologies to perform a low-frequency image-based pulsar census of the galactic plane (12 MWA observations, covering <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline2.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>6 000 <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline3.png\"/> <jats:tex-math> $textrm{deg}^textrm{2}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> sky). This work focuses on the detection of the known pulsar population which were present in the observed region of the sky using both image-based and beamformed methods. This resulted in the detection of 83 known pulsars, with 16 pulsars found only in Stokes I images but not in periodicity searches applied in beamformed data. Notably, for 14 pulsars these are the first reported low-frequency detections. This underscores the importance of image-based searches for pulsars that may be undetectable in time-series data, due to scattering and/or dispersive smearing at low frequencies. This highlights the importance of low-frequency flux density measurements in refining pulsar spectral models and investigating the spectral turnover of pulsars at low frequencies.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"18 799 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267620","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":"High-time resolution GPU imager for FRB searches at low radio frequencies","authors":"Marcin Sokolowski, Gayatri Aniruddha, Cristian Di Pietrantonio, Chris Harris, Danny Price, Samuel McSweeney, Randall Bruce Wayth, Ramesh Bhat","doi":"10.1017/pasa.2024.46","DOIUrl":"https://doi.org/10.1017/pasa.2024.46","url":null,"abstract":"Fast Radio Bursts (FRBs) are millisecond dispersed radio pulses of predominately extra-galactic origin. Although originally discovered at GHz frequencies, most FRBs have been detected between 400 and 800 MHz. Nevertheless, only a handful of FRBs were detected at radio frequencies <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000468_inline1.png\"/> <jats:tex-math> $le$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>400 MHz. Searching for FRBs at low frequencies is computationally challenging due to increased dispersive delay that must be accounted for. Nevertheless, the wide field of view (FoV) of low-frequency telescopes – such as the the Murchison Widefield Array (MWA), and prototype stations of the low-frequency Square Kilometre Array (SKA-Low) – makes them promising instruments to open a low-frequency window on FRB event rates, and constrain FRB emission models. The standard approach, inherited from high-frequencies, is to form multiple tied-array beams to tessellate the entire FoV and perform the search on the resulting time series. This approach, however, may not be optimal for low-frequency interferometers due to their large FoVs and high spatial resolutions leading to a large number of beams. Consequently, there are regions of parameter space in terms of number of antennas and resolution elements (pixels) where interferometric imaging is computationally more efficient. Here we present a new high-time resolution imager <jats:italic>BLINK</jats:italic> implemented on modern graphical processing units (GPUs) and intended for radio astronomy data. The main goal for this imager is to become part of a fully GPU-accelerated FRB search pipeline. We describe the imager and present its verification on real and simulated data processed to form all-sky and widefield images from the MWA and prototype SKA-Low stations. We also present and compare benchmarks of the GPU and CPU code executed on laptops, desktop computers, and Australian supercomputers. The code is publicly available at <jats:uri xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"https://github.com/PaCER-BLINK-Project/imager\">https://github.com/PaCER-BLINK-Project/imager</jats:uri> and can be applied to data from any radio telescope.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"119 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267623","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":"Measuring the stellar and planetary parameters of the 51 Eridani system","authors":"Ashley Elliott, Tabetha Boyajian, Tyler Ellis, Kaspar von Braun, Andrew W. Mann, Gail Schaefer","doi":"10.1017/pasa.2024.40","DOIUrl":"https://doi.org/10.1017/pasa.2024.40","url":null,"abstract":"In order to study exoplanets, a comprehensive characterisation of the fundamental properties of the host stars – such as angular diameter, temperature, luminosity, and age, is essential, as the formation and evolution of exoplanets are directly influenced by the host stars at various points in time. In this paper, we present interferometric observations taken of directly imaged planet host 51 Eridani at the CHARA Array. We measure the limb-darkened angular diameter of 51 Eridani to be &lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline1.png\"/&gt; &lt;jats:tex-math&gt; $theta_mathrm{LD} = 0.450pm 0.006$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; mas and combining with the Gaia zero-point corrected parallax, we get a stellar radius of &lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline2.png\"/&gt; &lt;jats:tex-math&gt; $1.45 pm 0.02$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; R&lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline3.png\"/&gt; &lt;jats:tex-math&gt; $_{odot}$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt;. We use the PARSEC isochrones to estimate an age of &lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline4.png\"/&gt; &lt;jats:tex-math&gt; $23.2^{+1.7}_{-2.0}$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; Myr and a mass of &lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline5.png\"/&gt; &lt;jats:tex-math&gt; $1.550^{+0.006}_{-0.005}$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; M&lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline6.png\"/&gt; &lt;jats:tex-math&gt; $_{odot}$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt;. The age and mass agree well with values in the literature, determined through a variety of methods ranging from dynamical age trace-backs to lithium depletion boundary methods. We derive a mass of &lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline7.png\"/&gt; &lt;jats:tex-math&gt; $4.1pm0.4$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; M&lt;jats:inline-formula&gt; &lt;jats:alternatives&gt; &lt;jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline8.png\"/&gt; &lt;jats:tex-math&gt; $_mathrm{Jup}$ &lt;/jats:tex-math&gt; &lt;/jats:alternatives&gt; &lt;/jats:inline-formula&gt; for 51 Eri b using the Sonora ","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"8 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267619","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":"3D relativistic MHD simulations of the gamma-ray binaries","authors":"Maxim Barkov, Evgeniy Kalinin, Maxim Lyutikov","doi":"10.1017/pasa.2024.52","DOIUrl":"https://doi.org/10.1017/pasa.2024.52","url":null,"abstract":"In gamma-ray binaries neutron star is orbiting a companion that produces a strong stellar wind. We demonstrate that observed properties of ‘stellar wind’–‘pulsar wind’ interaction depend both on the overall wind thrust ratio, as well as more subtle geometrical factors: the relative direction of the pulsar’s spin, the plane of the orbit, the direction of motion, and the instantaneous line of sight. Using fully 3D relativistic magnetohydrodynamical simulations we find that the resulting intrinsic morphologies can be significantly orbital phase-dependent: a given system may change from tailward-open to tailward-closed shapes. As a result, the region of unshocked pulsar wind can change by an order of magnitude over a quarter of the orbit. We calculate radiation maps and synthetic light curves for synchrotron (X-ray) and inverse-Compton emission (GeV-TeV), taking into account <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000523_inline1.png\"/> <jats:tex-math> $gamma $ </jats:tex-math> </jats:alternatives> </jats:inline-formula>–<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000523_inline2.png\"/> <jats:tex-math> $gamma $ </jats:tex-math> </jats:alternatives> </jats:inline-formula> absorption. Our modelled light curves are in agreement with the phase-dependent observed light curves of LS5039.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"41 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269638","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":"The global structure of astrospheres: effect of Knudsen number","authors":"S.D. Korolkov, V.V. Izmodenov","doi":"10.1017/pasa.2024.44","DOIUrl":"https://doi.org/10.1017/pasa.2024.44","url":null,"abstract":"The interaction between stellar winds and the partially ionized local interstellar medium (LISM) is quite common in astrophysics. However, the main difficulty in describing the neutral components lies in the fact that the mean free path of an interstellar atom, l, can be comparable to the characteristic size of an astrosphere, L (i.e., the Knudsen number, which is equal to l/L, is approximately equal to 1, as in the case of the heliosphere). In such cases, a single-fluid approximation becomes invalid, and a kinetic description must be used for the neutral component. In this study, we consider a general astrosphere and use a kinetic-gas dynamics model to investigate how the global structure of the astrosphere depends on the Knudsen number. We present numerical results covering an extremely wide range of Knudsen numbers (from 0.0001 to 100). Additionally, we explore the applicability of single-fluid approaches for modeling astrospheres of various sizes. We have excluded the influence of interstellar and stellar magnetic fields in our model to make parametric study of the kinetic effects feasible. The main conclusion of this work is that, for large astrospheres (with a distance to the bow shock greater than 600 AU) a heated rarefied plasma layer forms in the outer shock layer near the astropause. The formation of this layer is linked to localized heating of the plasma by atoms (specifically, ENAs) that undergo charge exchange again behind the astropause. This process significantly alters the flow structure in the outer shock layer and the location of the bow shock, and it cannot be described by a single-fluid model. Additionally, this paper discusses how atoms weaken the bow shocks at near-heliospheric conditions.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"6 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608428","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":"On bursty star formation during cosmological reionization - how does it influence the baryon mass content of dark matter halos?","authors":"Anand Menon, Chris Power","doi":"10.1017/pasa.2024.39","DOIUrl":"https://doi.org/10.1017/pasa.2024.39","url":null,"abstract":"The baryon mass content (i.e. stellar and gas mass) of dark matter halos in the early Universe depends on both global factors - e.g. ionizing ultraviolet (UV) radiation background - and local factors - e.g. star formation efficiency and assembly history. We use a lightweight semi-analytical model to investigate how both local and global factors impact the halo baryon mass content at redshifts of <jats:italic>z</jats:italic> ≥ 5. Our model incorporates a time delay between when stars form and when they produce feedback of 0 ≤ <jats:italic>t<jats:sup>d</jats:sup></jats:italic>/Myr ≤ 30, which can drive bursts of star formation, and a mass and redshift dependent UV background, which captures the influence of cosmological reionization on gas accretion onto halos. We use statistically representative halo assembly histories and assume that the cosmological gas accretion rate is proportional to the halo mass accretion rate. Delayed (<jats:italic>t<jats:sup>d</jats:sup></jats:italic>&gt;0) feedback leads to oscillations in gas mass with cosmic time, behaviour that cannot be captured with instantaneous feedback (<jats:italic>t<jats:sup>d</jats:sup></jats:italic>=0). Highly efficient star formation drives stronger oscillations, while strong feedback impacts when oscillations occur; in contrast, inefficient star formation and weak feedback produce similar long-term behaviour to that observed in instantaneous feedback models. If the delayed feedback timescale is too long, a halo retains its gas reservoir but the feedback suppresses star formation. Our model predicts that lower mass systems (halo masses <jats:italic>m</jats:italic><jats:sub>h</jats:sub> ≤ 10<jats:sup>7</jats:sup>M<jats:sub>⊙</jats:sub>) at <jats:italic>z</jats:italic> ≤ 10 should be strongly gas deficient (<jats:italic>m</jats:italic>g → 0), whereas higher mass systems retain their gas reservoirs because they are sufficiently massive to continue accreting gas through cosmological reionization. Interestingly, in higher mass halos, the median <jats:italic>m</jats:italic><jats:sub>⋆</jats:sub>/(<jats:italic>m</jats:italic><jats:sub>⋆</jats:sub> + <jats:italic>m</jats:italic><jats:sub>g</jats:sub>) ≃ 0.01 – 0.05, but is a factor of 3-5 smaller when feedback is delayed. Our model does not include seed supermassive black hole feedback, which is necessary to explain massive quenched galaxies in the early Universe.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"136 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940649","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":"MOSEL survey: Unwrapping the Epoch of Reionization through mimic galaxies at Cosmic Noon","authors":"Ravi Jaiswar, Anshu Gupta, Elisabete da Cunha, Cathryn M. Trott, Anishya Harshan, Andrew Battisti, Ben Forrest","doi":"10.1017/pasa.2024.37","DOIUrl":"https://doi.org/10.1017/pasa.2024.37","url":null,"abstract":"The nature of the first galaxies that reionized the universe during the Epoch of Reionization (EoR) remains unclear. Attempts to directly determine spectral properties of these early galaxies are affected by both limited photometric constraints across the spectrum and by the opacity of the intergalactic medium (IGM) to the Lyman Continuum (LyC) at high redshift. We approach this by analysing properties of analogous extreme emission line galaxies (EELGs, [OIII]+Hbeta EW&gt; 400) at 2.5 &lt; <jats:italic>z</jats:italic> &lt; 4 from the ZFOURGE survey using the Multi-wavelength Analysis of Galaxy Physical Properties (MAGPHYS) SED fitting code. We compare these to galaxies at <jats:italic>z</jats:italic> &gt; 5.5 observed with the James Webb Space Telesope (JWST) with self-consistent spectral energy distribution fitting methodology. This work focuses on the comparison of their UV slopes (β<jats:italic>P</jats:italic>), ionizing photon production efficiencies ξ<jats:italic>ion</jats:italic>, star formation rates and dust properties to determine the effectiveness of this analogue selection technique. We report the median ionizing photon production efficiencies as <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000377_inline1.png\"/> for our ZFOURGE control, ZFOURGE EELG, JADES and CEERS samples respectively. ZFOURGE EELGs are 0.57 dex lower in stellar mass and have half the dust extinction, compared to their ZFOURGE control counterparts. They also have a similar specific star formation rates and β<jats:italic>P</jats:italic> to the <jats:italic>z</jats:italic> &gt; 5.5 samples. We find that EELGs at low redshift (2.5 &lt; <jats:italic>z</jats:italic> &lt; 4) are analogous to EoR galaxies in their dust attenuation and specific star formation rates. Their extensive photometric coverage and the accessibility of their LyC region opens pathways to infer stellar population properties in the EoR.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"25 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940871","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":"Reduced-resolution beamforming: lowering the computational cost for pulsar and technosignature surveys","authors":"D. C. Price","doi":"10.1017/pasa.2024.35","DOIUrl":"https://doi.org/10.1017/pasa.2024.35","url":null,"abstract":"In radio astronomy, the science output of a telescope is often limited by computational resources. This is especially true for transient and technosignature surveys that need to search high-resolution data across a large parameter space. The tremendous data volumes produced by modern radio array telescopes exacerbate these processing challenges. Here, we introduce a ‘reduced-resolution’ beamforming approach to alleviate downstream processing requirements. Our approach, based on post-correlation beamforming, allows sensitivity to be traded against the number of beams needed to cover a given survey area. Using the MeerKAT and Murchison Widefield Array telescopes as examples, we show that survey speed can be vastly increased, and downstream signal processing requirements vastly decreased, if a moderate sacrifice to sensitivity is allowed. We show the reduced-resolution beamforming technique is intimately related to standard techniques used in synthesis imaging. We suggest that reduced-resolution beamforming should be considered to ease data processing challenges in current and planned searches; further, reduced-resolution beamforming may provide a path to computationally-expensive search strategies previously considered infeasible.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"309 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940849","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}