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Cosmology with radio and optical surveys

Over the coming years cosmology will be transformed, with enormous amounts of new data being collected by radio and optical surveys like the Euclid satellite mission and the MeerKAT Large Area Synoptic Survey. I will describe important opportunities and challenges these surveys face, and also talk about synergies between them.

• Speaker: Alkistis Pourtsidou (University of Edinburgh)
• Monday 10 March 2025, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Louis Legrand.

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Title to be confirmed

Abstract not available

• Speaker: Adrien La Posta (University of Oxford)
• Tuesday 20 May 2025, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Louis Legrand.

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Title to be confirmed

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• Speaker: Cathryn Trott, Curtin University
• Thursday 03 April 2025, 10:00-11:00
• Venue: SPO room + online.
• Series: 21cm Discussion Group; organiser: Harry Bevins.

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GINAN Update

Abstract not available

• Speaker: Ravi Subrahmanyan, CSIRO
• Thursday 20 March 2025, 10:00-11:00
• Venue: SPO room + online.
• Series: 21cm Discussion Group; organiser: Harry Bevins.

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Environmental and ecological drivers of early animal evolution

In-person

The circumstances surrounding the origin and early evolution of animals have long been a controversial topic, hinging on a mismatch between molecular clock estimates and the fossil record for the timing of animal diversification, the enigmatic appearance of the oldest known complex macroscopic fossils, and the potentially biased and incomplete fossil record of the Precambrian. In recent years, the timing of the origin and early diversification of animals has become much clearer, as molecular clock estimates have largely converged with macrofossil, microfossil, and biomarker records. This alignment now allows for a much more focused search for ecological or environmental factors that may have triggered the rise of animals.

The stable carbon isotope record serves as the ultimate reflection of the interaction between ancient life and the environment, as well as perturbations in the carbon cycle. However, interpreting stable carbon isotope signatures in both carbonate minerals and organic matter within ancient rocks is fraught with uncertainties arising from biological processes, sedimentological conditions, and diagenetic influences. Consequently, our understanding of ancient palaeoenvironments and the carbon cycle remains significantly constrained by these uncertainties.

Rather than measuring bulk isotopic signals from rock samples, we can directly infer the signatures of specific groups of organisms that inhabited ancient palaeobasins by analysing the isotopic composition of their unique biomarkers. For instance, the isotopic composition of hopanes and steranes closely reflects that of bacteria and eukaryotic algae, respectively. Leveraging this approach, we can gain an unprecedented level of detail about both the composition of ancient ecosystems and past environmental changes.

• Speaker: Ilya Bobrovskiy (Organic Geochemistry, Helmholtz Centre for Geosciences)
• Thursday 06 March 2025, 11:00-12:00
• Venue: Battcock, Room F17.
• Series: LCLU Coffee Meetings; organiser: Paul B. Rimmer.

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arXiv:2503.00981v1 Announce Type: new Abstract: HD 45166 was recently reported to be a long-period binary comprising a B7V star and a highly magnetic ($\langle B \rangle = 43.0\pm0.5\,$kG) hot Wolf-Rayet-like component, dubbed as a quasi Wolf-Rayet (qWR) star in literature. While originally proposed to be a short-period binary, long-term spectroscopic monitoring suggested a 22.5 yr orbital period. With a derived dynamical mass of $2.03\pm0.44\,M_\odot$, the qWR component is the most strongly magnetized non-degenerate object ever detected and a potential magnetar progenitor. However, the long period renders the spectroscopic orbital solution and dynamical mass estimates uncertain, casting doubts on whether the qWR component is massive enough to undergo core-collapse. Here, we spatially resolve the HD 45166 binary using newly acquired interferometric data obtained with the GRAVITY instrument of the Very Large Telescope Interferometer. Due to the calibrator star being a binary as well, we implement a new approach for visibility calibration and test it thoroughly using archival GRAVITY data. The newly calibrated HD 45166 data reveal the unmistakable presence of a companion to the qWR component with an angular separation of $10.9\pm0.1$ mas (which translates to a projected physical separation of $10.8\pm0.4$ au), consistent with the long-period orbit. We obtain a model-independent qWR mass $M_{\rm qWR} = 1.96^{+0.74}_{-0.54}\,M_\odot$ using interferometric and spectroscopic data together. This observation robustly confirms that HD 45166 is truly a long-period binary, and provides an anchor point for accurate mass determination of the qWR component with further observations.

arXiv:2503.00981v1 Announce Type: new Abstract: HD 45166 was recently reported to be a long-period binary comprising a B7V star and a highly magnetic ($\langle B \rangle = 43.0\pm0.5\,$kG) hot Wolf-Rayet-like component, dubbed as a quasi Wolf-Rayet (qWR) star in literature. While originally proposed to be a short-period binary, long-term spectroscopic monitoring suggested a 22.5 yr orbital period. With a derived dynamical mass of $2.03\pm0.44\,M_\odot$, the qWR component is the most strongly magnetized non-degenerate object ever detected and a potential magnetar progenitor. However, the long period renders the spectroscopic orbital solution and dynamical mass estimates uncertain, casting doubts on whether the qWR component is massive enough to undergo core-collapse. Here, we spatially resolve the HD 45166 binary using newly acquired interferometric data obtained with the GRAVITY instrument of the Very Large Telescope Interferometer. Due to the calibrator star being a binary as well, we implement a new approach for visibility calibration and test it thoroughly using archival GRAVITY data. The newly calibrated HD 45166 data reveal the unmistakable presence of a companion to the qWR component with an angular separation of $10.9\pm0.1$ mas (which translates to a projected physical separation of $10.8\pm0.4$ au), consistent with the long-period orbit. We obtain a model-independent qWR mass $M_{\rm qWR} = 1.96^{+0.74}_{-0.54}\,M_\odot$ using interferometric and spectroscopic data together. This observation robustly confirms that HD 45166 is truly a long-period binary, and provides an anchor point for accurate mass determination of the qWR component with further observations.

arXiv:2503.00919v1 Announce Type: new Abstract: The Largest Cluster Statistics\,(LCS) analysis of the redshifted 21\,cm maps has been demonstrated to be an efficient and robust method for following the time evolution of the largest ionized regions\,(LIRs) during the Epoch of Reionization\,(EoR). The LCS can, in principle, constrain the reionization model and history by quantifying the morphology of neutral hydrogen\,(\HI) distribution during the different stages of the EoR. Specifically, the percolation transition of ionized regions, quantified and constrained via LCS, provides a crucial insight about the underlying reionization model. The previous LCS analysis of EoR 21\,cm maps demonstrates that the convolution of the synthesized beam of the radio interferometric arrays, e.g. SKA1-Low with the target signal, shifts the apparent percolation transition of ionized regions towards the lower redshifts. In this study, we present an optimal thresholding strategy to reduce this bias in the recovered percolation transition. We assess the robustness of LCS analysis of the 21\,cm maps in the presence of antenna-based gain calibration errors and instrumental noise for SKA1-Low. This analysis is performed using synthetic observations simulated by the \textsc{21cmE2E} pipeline, considering SKA1-Low AA4 configuration within a radius of 2\,km from the array centre. Our findings suggest that a minimum of $1500$\,hours of observation (SNR $\gtrapprox 3$) are required for the LCS analysis to credibly suppress the confusion introduced by thermal noise. Further, we also demonstrate that for a maximum antenna-based calibration error tolerance of $\sim 0.05\%$ (post calibration), the reionization history can be recovered in a robust and relatively unbiased manner using the LCS.

arXiv:2503.00919v1 Announce Type: new Abstract: The Largest Cluster Statistics\,(LCS) analysis of the redshifted 21\,cm maps has been demonstrated to be an efficient and robust method for following the time evolution of the largest ionized regions\,(LIRs) during the Epoch of Reionization\,(EoR). The LCS can, in principle, constrain the reionization model and history by quantifying the morphology of neutral hydrogen\,(\HI) distribution during the different stages of the EoR. Specifically, the percolation transition of ionized regions, quantified and constrained via LCS, provides a crucial insight about the underlying reionization model. The previous LCS analysis of EoR 21\,cm maps demonstrates that the convolution of the synthesized beam of the radio interferometric arrays, e.g. SKA1-Low with the target signal, shifts the apparent percolation transition of ionized regions towards the lower redshifts. In this study, we present an optimal thresholding strategy to reduce this bias in the recovered percolation transition. We assess the robustness of LCS analysis of the 21\,cm maps in the presence of antenna-based gain calibration errors and instrumental noise for SKA1-Low. This analysis is performed using synthetic observations simulated by the \textsc{21cmE2E} pipeline, considering SKA1-Low AA4 configuration within a radius of 2\,km from the array centre. Our findings suggest that a minimum of $1500$\,hours of observation (SNR $\gtrapprox 3$) are required for the LCS analysis to credibly suppress the confusion introduced by thermal noise. Further, we also demonstrate that for a maximum antenna-based calibration error tolerance of $\sim 0.05\%$ (post calibration), the reionization history can be recovered in a robust and relatively unbiased manner using the LCS.

arXiv:2502.18651v2 Announce Type: replace Abstract: In this second paper on the variability survey of central stars of planetary nebulae (CSPNe) using ZTF, we focus on the 11 long-timescale variables with variability timescales ranging from months to years. We also present preliminary analyses based on spectroscopic and/or photometric follow-up observations for six of them. Among them is NGC 6833, which shows a 980 day periodic variability with strange characteristics: 'triangle-shaped' brightening in $r$, $i$, and WISE bands but almost coincidental shallow dips in the $g$-band. We speculate this to be a wide but eccentric binary with the same orbital period. Long-period near-sinusoidal variability was detected in two other systems, NGC 6905 and Kn 26, with periods of 700 days and 230 days, respectively, making them additional wide-binary candidates. The latter also shows a short period at 1.18 hours which can either be from a close inner binary or pulsational origin. We present CTSS 2 and PN K 3-5 which show brightening and significant reddening over the whole ZTF baseline. A stellar model fit to the optical spectrum of CTSS 2 reveals it to be one of the youngest post-AGB CSPN known. Both show high-density emission-line cores. These appear to be late thermal pulse candidates, currently evolving towards the AGB phase, though alternative explanations are possible. We then present recent HST/COS ultraviolet spectroscopy of the known wide-binary candidate LoTr 1 showing that the hot star is a spectroscopic twin of the extremely hot white dwarf in UCAC2 46706450. We think that the long photometric period of 11 years is the binary orbital period. Finally, we briefly discuss the ZTF light curves of the remaining variables, namely Tan 2, K 3-20, WHTZ 3, Kn J1857+3931, and IPHAS J1927+0814. With these examples, we present the effectiveness of the von Neumann statistics and Pearson Skew-based metric space in searching for long-timescale variables.

arXiv:2502.18651v2 Announce Type: replace Abstract: In this second paper on the variability survey of central stars of planetary nebulae (CSPNe) using ZTF, we focus on the 11 long-timescale variables with variability timescales ranging from months to years. We also present preliminary analyses based on spectroscopic and/or photometric follow-up observations for six of them. Among them is NGC 6833, which shows a 980 day periodic variability with strange characteristics: 'triangle-shaped' brightening in $r$, $i$, and WISE bands but almost coincidental shallow dips in the $g$-band. We speculate this to be a wide but eccentric binary with the same orbital period. Long-period near-sinusoidal variability was detected in two other systems, NGC 6905 and Kn 26, with periods of 700 days and 230 days, respectively, making them additional wide-binary candidates. The latter also shows a short period at 1.18 hours which can either be from a close inner binary or pulsational origin. We present CTSS 2 and PN K 3-5 which show brightening and significant reddening over the whole ZTF baseline. A stellar model fit to the optical spectrum of CTSS 2 reveals it to be one of the youngest post-AGB CSPN known. Both show high-density emission-line cores. These appear to be late thermal pulse candidates, currently evolving towards the AGB phase, though alternative explanations are possible. We then present recent HST/COS ultraviolet spectroscopy of the known wide-binary candidate LoTr 1 showing that the hot star is a spectroscopic twin of the extremely hot white dwarf in UCAC2 46706450. We think that the long photometric period of 11 years is the binary orbital period. Finally, we briefly discuss the ZTF light curves of the remaining variables, namely Tan 2, K 3-20, WHTZ 3, Kn J1857+3931, and IPHAS J1927+0814. With these examples, we present the effectiveness of the von Neumann statistics and Pearson Skew-based metric space in searching for long-timescale variables.

arXiv:2404.16261v3 Announce Type: replace Abstract: Over twenty years ago, Type Ia Supernovae (SNIa) observations revealed an accelerating Universe expansion, suggesting a significant dark energy presence, often modelled as a cosmological constant, \( \Lambda \). Despite its pivotal role in cosmology, the standard $\Lambda$CDM model remains largely underexplored in the redshift range between distant SNIa and the Cosmic Microwave Background (CMB). This study harnesses the James Webb Space Telescope's advanced capabilities to extend the Hubble flow mapping across an unprecedented redshift range, from \( z \approx 0 \) to \( z \approx 7.5 \). Using a dataset of 231 HII galaxies and extragalactic HII regions, we employ the \(\text{L}-\sigma\) relation that correlates the luminosity of Balmer lines with their velocity dispersion, to define a competitive technique for measuring cosmic distances. This approach allows the mapping of the Universe expansion history over more than 12 billion years, covering 95\% of its age. Our analysis, using Bayesian inference, constrains the parameter space $\lbrace h, \Omega_m, w_0\rbrace = \lbrace 0.731\pm0.039, 0.302^{+0.12}_{-0.069}, -1.01^{+0.52}_{-0.29}\rbrace $ (statistical) for a flat Universe. Our results provide new insights into cosmic evolution and imply a lack of change in the photo-kinematical properties of the young massive ionizing clusters in HII galaxies across most of the history of the Universe.

arXiv:2404.16261v3 Announce Type: replace Abstract: Over twenty years ago, Type Ia Supernovae (SNIa) observations revealed an accelerating Universe expansion, suggesting a significant dark energy presence, often modelled as a cosmological constant, \( \Lambda \). Despite its pivotal role in cosmology, the standard $\Lambda$CDM model remains largely underexplored in the redshift range between distant SNIa and the Cosmic Microwave Background (CMB). This study harnesses the James Webb Space Telescope's advanced capabilities to extend the Hubble flow mapping across an unprecedented redshift range, from \( z \approx 0 \) to \( z \approx 7.5 \). Using a dataset of 231 HII galaxies and extragalactic HII regions, we employ the \(\text{L}-\sigma\) relation that correlates the luminosity of Balmer lines with their velocity dispersion, to define a competitive technique for measuring cosmic distances. This approach allows the mapping of the Universe expansion history over more than 12 billion years, covering 95\% of its age. Our analysis, using Bayesian inference, constrains the parameter space $\lbrace h, \Omega_m, w_0\rbrace = \lbrace 0.731\pm0.039, 0.302^{+0.12}_{-0.069}, -1.01^{+0.52}_{-0.29}\rbrace $ (statistical) for a flat Universe. Our results provide new insights into cosmic evolution and imply a lack of change in the photo-kinematical properties of the young massive ionizing clusters in HII galaxies across most of the history of the Universe.

arXiv:2503.00636v1 Announce Type: new Abstract: We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of Planck. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at $z < 3$; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from Rubin of overlapping sky.

arXiv:2503.00636v1 Announce Type: new Abstract: We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of Planck. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at $z < 3$; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from Rubin of overlapping sky.

arXiv:2503.00113v1 Announce Type: new Abstract: The integral-field unit mode of the Near-Infrared Spectrograph (NIRSpec+IFU) mounted on the James Webb Space Telescope has now enabled kinematic studies of smaller and less massive compact stellar systems in which to search for central massive black holes (BHs) than ever before. We present here the first such detection using NIRSpec+IFU in its highest resolution (R~2700) mode. We report a $3\sigma$ detection of a central black hole with mass ${\cal M}_{BH}=2.2\pm1.1\times10^6\,M_\odot$ in UCD736 orbiting within the Virgo galaxy cluster based on Schwarzschild's modeling of the 1D kinematic profile. The presence of such a massive BH strongly argues against a globular cluster origin of this UCD, and rather suggests a tidally stripped formation route from a former $\gtrsim10^9\,M_\odot$ dwarf galaxy host. Two other methods produce results consistent with Schwarzschild's modelling, but can only provide upper-limits on ${\cal M}_{BH}$. This represents the detection of a BH in the most compact ($r_h\approx15\,{\rm pc}$) stellar system to date, with a ${\cal M}_{BH}$ corresponding to ~9 percent of the system's stellar mass, roughly in line with previously reported UCD BH detections and comparable to the BH detected in the compact elliptical galaxy NGC4486B.

arXiv:2503.00113v1 Announce Type: new Abstract: The integral-field unit mode of the Near-Infrared Spectrograph (NIRSpec+IFU) mounted on the James Webb Space Telescope has now enabled kinematic studies of smaller and less massive compact stellar systems in which to search for central massive black holes (BHs) than ever before. We present here the first such detection using NIRSpec+IFU in its highest resolution (R~2700) mode. We report a $3\sigma$ detection of a central black hole with mass ${\cal M}_{BH}=2.2\pm1.1\times10^6\,M_\odot$ in UCD736 orbiting within the Virgo galaxy cluster based on Schwarzschild's modeling of the 1D kinematic profile. The presence of such a massive BH strongly argues against a globular cluster origin of this UCD, and rather suggests a tidally stripped formation route from a former $\gtrsim10^9\,M_\odot$ dwarf galaxy host. Two other methods produce results consistent with Schwarzschild's modelling, but can only provide upper-limits on ${\cal M}_{BH}$. This represents the detection of a BH in the most compact ($r_h\approx15\,{\rm pc}$) stellar system to date, with a ${\cal M}_{BH}$ corresponding to ~9 percent of the system's stellar mass, roughly in line with previously reported UCD BH detections and comparable to the BH detected in the compact elliptical galaxy NGC4486B.

The best chance to see as many as possible will be after sunset on Wednesday and Thursday.

Nature, Published online: 03 March 2025; doi:10.1038/d41586-025-00670-7

The touchdown is a much-needed win for NASA’s partnerships with commercial space companies.

The second-ever commercial landing on the moon comes amid a flurry of lunar exploration activity that will see around a dozen missions this year alone