Research Articles (Physics)

Permanent URI for this collectionhttps://hdl.handle.net/10566/726

Browse

Now showing 1 - 20 of 764

High precision, high time-cadence measurements of the MgII index of solar activity by the GOES-R Extreme Ultraviolet Irradiance Sensor 2: EUVS-C initial flight performance
(EDP Sciences, 2025) McClintock, William E; Snow, Martin; Eden, Thomas D; Eparvier, Francis G; Machol, Janet L; Woodraska, Donald L
EUVS-C is one component of the Extreme Ultraviolet Irradiance Sensor (EUVS) instrument. EUVS, together with the X-ray sensor (XRS), comprise the Extreme Ultraviolet and X-ray Irradiances Sen-sors (EXIS) investigation (Machol JL et al. 2020. The GOES-R series: a new generation of geostationary environmental satellites, pp. 233–242. https://doi.org/10.1016/B978-0-12-814327-8.00019-6) aboard the GOES-R satellite series, which includes GOES-16, -17, -18, and -19. From their vantage points in geostationary orbit, the EUVS-C instruments measure the solar MgII Index, also referred to as the MgII core-to-wing-ratio, which is a proxy for chromosphere activity and correlates with solar extreme ultraviolet (EUV) emission. MgII produces two bright chromosphere emission lines appearing in the sun’s spectrum at 279.55 nm and 280.71 nm (MgII k and h) that appear in the cores of their respective photospheric absorption lines. Measuring the ratio of emission from the core (chromospheric) to that from the wings (photo-spheric) provides an index that is relatively insensitive to changes in instrument performance. In 2005, Snow & McClintock used 0.1 nm resolution data to show that the intrinsic solar variability in the index (as opposed to instrument noise) is on the order of 0.2% on time scales of 5–10 min. EUVS-C is designed to exceed these performance requirements. A companion paper describes the instrument design and its pre-flight calibration. This paper describes the operational implementation of the algorithm that produces the Index, flight calibrations, and the initial instrument flight performance. Each EUVS-C currently operating (GOES-16, -18, and -19) is providing high time-cadence (3 s), high precision (1 part in 10 4 ) Index determinations. Spectral shifts arising from spacecraft orbital motion introduce a systematic 0.1% diurnal various operation in absolute index values. Additionally, wavelength-dependent radiometric responsivity degradation leads to a systematic increase in the reported index on a timescale of years at an average rate of 0.2% per year. These systematic effects can be mitigated with additional post-data processing.
Weighing neutrinos with 21cm intensity mapping at the SKAO
(Institute of Physics, 2026) Spinelli, Marta; Berti, Maria; Spinelli, Marta
We explore the constraining power of future 21cm intensity mapping (IM) observations at the SKAO, focusing primarily on the sum of neutrino masses, Σmν . We forecast observations of the 21cm IM auto-power spectrum as well as the 21cm IM and galaxy surveys cross-correlation power spectrum. We construct different synthetic data sets of observations for the 21cm IM observables in the redshift range 0 < z < 3. For galaxy clustering, we consider two stage-IV surveys to mimic a DESI-like and Euclid-like cross-correlation signal. We study the impact of assuming three different fiducial values for the sum of neutrino masses, i.e. Σmν = 0.06, 0.1, 0.4 eV, in the synthetic data sets. To investigate the constraining power of the forecasted 21cm observations, we build a likelihood code that will be made publicly available upon publication. The results of the analysis, obtained through Markov Chain Monte Carlo techniques, are promising. We find that the 21cm auto-power spectrum alone could provide an upper limit on the sum of neutrino masses of Σmν < 0.287 eV, at 95% confidence level, for the case of the lowest fiducial value of Σmν . This result is comparable to the upper limits provided by cosmic microwave background (CMB) observations alone. When combining the 21cm auto-power spectrum synthetic data set with Planck 2018 CMB measurements, we find a tighter upper limit of Σmν < 0.105 eV, which improves on the constraints from Planck alone. We obtain a similar result already at the level of 21cm and galaxy clustering cross-correlation power spectrum, whose detection is more easily achieved as they are less affected by systematic effects. Combining synthetic data sets with Planck 2018 data, we find the upper limits of Σmν < 0.116 eV and Σmν < 0.117 eV for the 21cm signal in cross-correlation with the DESI-like and Euclid-like surveys, respectively. These constraints are comparable to those obtained by combining Planck data with the 21cm auto-power spectrum synthetic data sets, thus supporting the case for 21cm cross-correlation detections.
Mightee/cosmos-3d: The discovery of three spectroscopically confirmed radio-selected star-forming galaxies at z = 4.9–5.6
(Oxford University Press, 2026) Jarvis M.J.; Saxena, Aayush; Varadaraj, Rohan G
Radio observations offer a dust-independent probe of star formation and active galactic nucleus (AGN) activity, but sufficiently deep data are required to access the cross-over luminosity between these processes at high redshift ((Formula presented)). We present three spectroscopically confirmed high-redshift radio sources (HzRSs) detected at 1.3 GHz at (Formula presented) –5.6, with radio luminosities spanning (Formula presented) –(Formula presented). These sources were first identified as high-redshift candidates through spectral energy distribution (SED) fitting of archival Hubble, James Webb Space Telescope (JWST) NIRCam + MIRI, and ground-based photometry, and then spectroscopically confirmed via the (Formula presented) emission line using wide-field slitless spectroscopy from JWST COSMOS-3D. The star formation rates (SFRs) measured from SED fitting, the (Formula presented) flux, and the 1.3 GHz luminosity, span (Formula presented) –(Formula presented), demonstrating broad agreement between these SFR tracers. We find that these three sources lie either on or 0.5–1.0 dex above the star-forming main sequence at (Formula presented) –6 and have undergone a recent burst of star formation. The sources have extended rest-ultraviolet (UV)/optical morphologies with no evidence for a dominant point source component, indicating that an AGN is unlikely to dominate their rest-UV and optical emission. Two of the sources have complex, multicomponent rest-frame UV/optical morphologies, suggesting that their starbursts may be triggered by merging activity. These HzRSs open up a new window towards probing radio emission powered by star formation alone at (Formula presented), representing a remarkable opportunity to begin tracing star formation, independent of dust, in the early Universe.
The Low-mass Dwarf Host Galaxy of Nonrepeating FRB 20230708A
(American Astronomical Society, 2026) Muller, August R.; Gordon, Alexa C.; Ryder, Stuart D.
We present Very Large Telescope/X-Shooter spectroscopy for the host galaxies of 12 fast radio bursts (FRBs) detected by the Australian SKA Pathfinder observed through the “Fast and Unbiased FRB Host Galaxy (FURBY)” Large Programme at the European Southern Observatory, which imposes strict selection criteria on the included FRBs and their host galaxies to produce a homogeneous and well-defined sample. We describe the data reduction and analysis of these spectra and report their redshifts, line-emission fluxes, and derived host properties. From the present sample, this paper focuses on the faint host of FRB 20230708A (m R = 22.53 ± 0.02) identified at low redshift (z = 0.1050). This indicates an intrinsically very low-luminosity galaxy (L ≈ 108 L ⊙), making it the lowest-luminosity nonrepeating FRB host to date by a factor of ∼3 and slightly dimmer than the lowest-luminosity host for repeating FRBs. Our spectral energy distribution fitting analysis reveals a low stellar mass (M * ≈ 108.0 M ⊙), low star formation rate (SFR ≈ 0.04M ⊙ yr−1), and very low metallicity(12 + log ( O / H) ∼ (8.0 − 8.3)), distinct from the more massive galaxies (log(M/M ⊙) ∼ 10) that are commonly identified for nonrepeating FRBs. Its discovery demonstrates that FRBs can arise in the faintest, metal-poor galaxies of the Universe. In turn, this suggests that at least one FRB progenitor channel must include stars (or their remnants) created in very low metallicity environments. This indicates better prospects for detecting FRBs from the high-z Universe where young, low-mass galaxies proliferate.
The study of radiation contamination in Roodepoort gold mine tailings using HPGe gamma spectroscopy
(Frontiers Media SA, 2026) Maleka, Peane P.; Ntshangase S. Sifiso; Majola N.T. Siyabonga
In this study, a coaxial HPGe high-resolution γ-detector was used to measure the γ-signals in soil samples collected from the Roodepoort Gold Tailings. There have been complaints about dust from the gold tailings, and the study aims to determine the level of contamination. The activity concentration of 238U ranged from 132.88 ± 4.68 to 1,421.46 ± 13.38, with a mean of 464.96 ± 2.08 Bq/kg. The activity concentration of 226Ra ranged from 130.19 ± 4.48 to 1,359.27 ± 13.83, with a mean of 425.28 ± 8.02 Bq/kg. The range of 232Th was from 5.27 ± 0.67 to 19.37 ± 1.98, with a mean of 11.20 ± 1.03 Bq/kg, and 40K activity ranged from 65.23 ± 15.29 to 264.11 ± 25.66, with a mean of 127.50 ± 21.85 Bq/kg. The findings showed that 238U and 226Ra activities exceeded the global average of 35 Bq/kg, while 232Th and 40K were below their respective limits. The radiological hazard indices exceeded recommended limits, making the tailings soil completely unsuitable for use as building materials, as this may have deleterious health effects on residents in the future.
Phantom crossing or dark interaction?
(Institute of Physics, 2026) Guedezounme, Sêcloka Lazare; Dinda, Bikash Ranjan.; Maartens, Roy
Recent results from DESI BAO measurements, together with Planck CMB and Pantheon+ data, suggest that there may be a 'phantom' phase (wde < -1) in the expansion of the Universe. This inference follows when the w0, wa parametrization for the dark energy equation of state wde is used to fit the data. Since phantom dark energy in general relativity is unphysical, we investigate the possibility that the phantom behaviour is not intrinsic, but effective — due to a non-gravitational interaction between dark matter and non-phantom dark energy. To this end, we assume a physically motivated thawing quintessence-like form of the intrinsic dark energy equation of state wde. Then we use a w0, wa model for the effective equation of state of dark energy. We find that the data favours a phantom crossing for the effective dark energy, but only at low significance. The intrinsic equation of state of dark energy is non-phantom, without imposing any non-phantom priors. A nonzero interaction is favoured at more than 3σ at z ∼ 0.3. The energy flows from dark matter to dark energy at early times and reverses at later times.
Radio frequency interference from radio navigation satellite systems: simulations and comparison to MeerKAT single-dish data
(Oxford University Press, 2026) Engelbrecht, Brandon Nicholas.; Santos, Mario G.; Fonseca, José; Li, Yichao; Wang, Jingying; Irfan, Melis O.; Harper, Stuart E.; Grainge, Keith J.B.; Bull, Philip; Carucci, Isabella P.; Cunnington, Steven D.; Pourtsidou, Alkistis; Spinelli, Marta; Wolz, Laura
Radio frequency interference (RFI) is emitted from various sources, terrestrial or orbital, and creates a nuisance for ground-based 21-cm experiments. In particular, single-dish observations will be highly susceptible to RFI due to their wide primary beam and sensitivity. This work aimed to simulate the contamination effects from the Radio Navigational Satellite System (RNSS) within the 1100-1350 (MHz) frequency band. The simulation can be divided into two parts: (i) satellite positioning, emission power, and the beam response on the telescope, and (ii) calibration of the satellite signals to data to improve the original model. We utilize previously observed single-dish L-band data from the Meer-Karoo Array Telescope (MeerKAT), which requires special calibration to account for regions contaminated by satellite-based RFI. We find that we can recreate the satellite contamination with high accuracy around its peak frequencies provided the satellite is not too close to the telescope's pointing direction. The simulation can predict satellite movements and signals for past and future observations, aiding in RFI avoidance and testing novel cleaning methods. The predicted signal sits below the noise in the target cosmology window in the L band (970-1015 MHz) making it difficult to confirm any out-of-band emission from satellites. However, in our simulations, this contamination still overwhelmed the 21-cm auto-power spectrum. Nevertheless, it is possible to detect the signal in cross-correlations after mild foreground cleaning. Whether such out of band contamination does exist will require further characterization of the satellite signals far away from their peak frequencies.
Identifying transient hosts in LSST’s deep drilling fields with galaxy catalogs
(American Astronomical Society, 2026) Joshua, Weston G.; Young, David R.; Smartt, Stephen J.; Nicholl, Matt; Jarvis, Matthew J.; Whittam, Imogen Helen.
The upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will enable astronomers to discover rare and distant astrophysical transients. Host-galaxy association is crucial for selecting the most scientifically interesting transients for follow-up. LSST deep drilling field (DDF) observations will detect distant transients occurring in galaxies below the detection limits of most all-sky catalogs. Here, we investigate the use of preexisting, field-specific catalogs for host identification in the DDFs and a ranking of their usefulness. We have compiled a database of 70 deep catalogs that overlap with the Rubin DDFs and constructed thin catalogs to be homogenized and combined for transient-host matching. A systematic ranking of their utility is discussed and applied based on the inclusion of information such as spectroscopic redshifts and morphological information. Utilizing this data against a Dark Energy Survey sample of supernovae with pre-identified hosts in the XMM-Large Scale Structure and the Extended Chandra Deep Field-South fields, we evaluate different methods for transient-host association in terms of both accuracy and processing speed. We also apply light data-cleaning techniques to identify and remove contaminants within our associations, such as diffraction spikes and blended galaxies where the correct host cannot be determined with confidence. We use a lightweight machine learning approach in the form of extreme gradient boosting to generate confidence scores in our contaminant selections and associated metrics. Finally, we discuss the computational expense of implementation within the LSST transient alert brokers, which will require efficient, fast-paced processing to handle the large stream of survey data.
Universality of r-process elemental abundances: a well-regulated conspiracy of astrophysical and nuclear properties
(Institute of Physics, 2026) Orce, José Nicolás
The isovector distribution of thousands of products of electric dipole (E1) matrix elements connecting the ground and first excited states through virtual excitations in the giant dipole resonance (GDR) region is presented for the first time in selected p and sd shell nuclei from 1ℏω shell-model calculations. A smaller nuclear dipole polarizability for the first excited level with respect to the ground state arises from the destructive contribution of off-diagonal E1 matrix elements. This results in a larger symmetry energy consistent with data from GDRs built on excited states of heavier nuclei at temperatures of 0.5 ⪅ T ⪅ 1 MeV and previous calculations of the temperature dependence of the symmetry energy in medium-mass nuclei within the quasiparticle random phase approximation and the shell-model Monte Carlo. The corresponding reduction of the binding energy in the Bethe-Weizsäcker semi-empirical mass formula yields a drop of radiative neutron capture rates and the shift of the neutron drip line towards the line of stability; in turn, providing a plausible explanation for the origin of the universality of elemental abundances by sharply constraining the reaction network flow for r-process nucleosynthesis.
The anisotropic expansion rate of the local universe and its covariant cosmographic interpretation
(Institute of Physics, 2026) Kalbouneh, Basheer; Marinoni, Christian; Maartens, Roy; Bel, Julien; Santiago, Jessica; Clarkson, Chris A.; Sarma, Maharshi; Virey, Jean Marc
Without making any assumption on the underlying geometry and metric of the local Universe, we provide a measurement of the expansion rate fluctuation field using the Cosmicflows-4 and Pantheon+ samples in the redshift range 0.01
High precision, high time-cadence measurements of the Mg II index of solar activity by the GOES-R Extreme ultraviolet irradiance sensor 1: EUVS-C design and preflight calibration
(EDP Sciences, 2025) McClintock, William E; Snow, Martin; Crotser, David; Eparvier, Francis G
EUVS-C is one component of the Extreme Ultraviolet Irradiance Sensor (EUVS) instrument. EUVS, together with the X-Ray Sensor (XRS), comprise the Extreme Ultraviolet and X-ray Irradiances Sensors (EXIS) investigation aboard the GOES-R satellite series, which includes GOES-16, -17, -18, and -19. From their vantage points in geostationary orbit, the EUVS-C instruments make high-precision (better than 1 part in 10 4 ), high-time-cadence (3 s) measurements of the solar Mg II Index with moderate (0.1 nm) spectral resolution. The index, also referred to as the Mg II core-to-wing ratio, is a proxy for chromosphere activity that correlates with solar extreme ultraviolet (EUV) irradiance. Mg II produces two bright chromosphere emission lines in the sun’s spectrum at 279.55 nm and 280.71 nm (Mg II k and h) that appear in the cores of their respective photospheric absorption lines. Measuring the ratio of emission from the core (chromospheric) to that from the wings (photospheric) provides an index that is relatively insensitive to changes in radiometric performance that often occur when scientific instruments observe the sun. EUVS-C design specifications were informed by earlier research reporting index variability of approximately 0.2% on time scales of 6–10 min, increasing to approximately 0.3% and approximately 0.55% for 30 and 80 min, respectively. This paper describes the EUVS-C instrument design and implementation, its ground calibration and characterization, and its anticipated measurement performance. A companion paper describes the initial EUVS-C flight measurement performance.
Modeling and analysis of KSnI3 perovskite solar cells yielding power conversion efficiency of 30.21%
(MDPI, 2025) Kheswa, Bonginkosi Vincent; Majola, Siyabonga Ntokozo Thandoluhle; Al-Dmour, Hmoud; Ndzane, Nolufefe Muriel; Makhathini, Lucky
KSnI3-based perovskite solar cells have attracted a lot of research interest due their unique electronic, optical, and thermal properties. In this study, we optimized the performance of various lead-free perovskite solar cell structures—specifically, FTO/Al–ZnO/KSnI3/rGO/Se, FTO/LiTiO2/KSnI3/rGO/Se, FTO/ZnO/KSnI3/rGO/Se, and FTO/SnO2/KSnI3/rGO/Se, using the SCAPS-1D simulation tool. The optimization focused on the thicknesses and dopant densities of the rGO, KSnI3, Al–ZnO, LiTiO2, ZnO, and SnO2 layers, the thickness of the FTO electrode, as well as the defect density of KSnI3. This yielded PCE values of 27.60%, 24.94%, 27.62%, and 30.21% for the FTO/Al–ZnO/KSnI3/rGO/Se, FTO/LiTiO2/KSnI3/rGO/Se, FTO/ZnO/KSnI3/rGO/Se, and FTO/SnO2/KSnI3/rGO/Se perovskite solar cell configurations, respectively. The FTO/SnO2/KSnI3/rGO/Se device is 7.43% more efficient than the FTO/SnO2/3C-SiC/KSnI3/NiO/C device, which is currently the highest performing KSnI3-based perovskite solar cell in the literature. Thus, our FTO/SnO2/KSnI3/rGO/Se perovskite solar cell structure is now, by far, the most efficient PSC design. Its best performance is achieved under ideal conditions of a series resistance of 0.5 Ω cm2, a shunt resistance of 107 Ω cm2, and a temperature of 371 K.
Radio frequency interference from radio navigation satellite systems: simulations and comparison to MeerKAT single-dish data
(Oxford University Press, 2025) Engelbrecht, Brandon N; Santos, Mario G; Fonseca, José; Li, Yichao; Wang, Jingying; Irfan, Melis O; Harper, Stuart E; Grainge, Keith; Bull, Philip; Carucci, Isabella P; Cunnington, Steven; Pourtsidou, Alkistis; Spinelli, Marta; Wolz, Laura
Radio frequency interference (RFI) is emitted from various sources, terrestrial or orbital, and creates a nuisance for ground-based 21-cm experiments. In particular, single-dish observations will be highly susceptible to RFI due to their wide primary beam and sensitivity. This work aimed to simulate the contamination effects from the Radio Navigational Satellite System (RNSS) within the 1100-1350 (MHz) frequency band. The simulation can be divided into two parts: (i) satellite positioning, emission power, and the beam response on the telescope, and (ii) calibration of the satellite signals to data to improve the original model. We utilize previously observed single-dish L-band data from the Meer-Karoo Array Telescope (MeerKAT), which requires special calibration to account for regions contaminated by satellite-based RFI. We find that we can recreate the satellite contamination with high accuracy around its peak frequencies provided the satellite is not too close to the telescope's pointing direction. The simulation can predict satellite movements and signals for past and future observations, aiding in RFI avoidance and testing novel cleaning methods. The predicted signal sits below the noise in the target cosmology window in the L band (970-1015 MHz) making it difficult to confirm any out-of-band emission from satellites. However, in our simulations, this contamination still overwhelmed the 21-cm auto-power spectrum. Nevertheless, it is possible to detect the signal in cross-correlations after mild foreground cleaning. Whether such out of band contamination does exist will require further characterization of the satellite signals far away from their peak frequencies.
Identifying transient hosts in LSST’s deep drilling fields with galaxy catalogs
(American Astronomical Society, 2026) Weston, J.G; Young, D.R; Smartt, S.J; Nicholl, M; Jarvis, Matt J; Whittam, Imogen H
The upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will enable astronomers to discover rare and distant astrophysical transients. Host-galaxy association is crucial for selecting the most scientifically interesting transients for follow-up. LSST deep drilling field (DDF) observations will detect distant transients occurring in galaxies below the detection limits of most all-sky catalogs. Here, we investigate the use of preexisting, field-specific catalogs for host identification in the DDFs and a ranking of their usefulness. We have compiled a database of 70 deep catalogs that overlap with the Rubin DDFs and constructed thin catalogs to be homogenized and combined for transient-host matching. A systematic ranking of their utility is discussed and applied based on the inclusion of information such as spectroscopic redshifts and morphological information. Utilizing this data against a Dark Energy Survey sample of supernovae with pre-identified hosts in the XMM-Large Scale Structure and the Extended Chandra Deep Field-South fields, we evaluate different methods for transient-host association in terms of both accuracy and processing speed. We also apply light data-cleaning techniques to identify and remove contaminants within our associations, such as diffraction spikes and blended galaxies where the correct host cannot be determined with confidence. We use a lightweight machine learning approach in the form of extreme gradient boosting to generate confidence scores in our contaminant selections and associated metrics. Finally, we discuss the computational expense of implementation within the LSST transient alert brokers, which will require efficient, fast-paced processing to handle the large stream of survey data.
Calibration-independent consistency test of BAO and SNIa data: update
(Institute of Physics, 2026) Dinda, Bikash R; Maartens, Roy; Clarkson, Chris
In a recent paper 2509.19899, we presented a new method to test the consistency between uncalibrated BAO and SNIa data through a common parameter, the Alcock-Paczynski variable. Using Gaussian Processes, we can determine if various datasets are consistent, independently of dark energy or modified gravity models, and of the sound horizon and SNIa peak magnitude. We found that the DES-Y5 SNIa data showed non-negligible tension with other datasets. However, the recent update DES-Dovekie removes this tension. We find that all uncalibrated data from DESI DR2 BAO and three SNIa datasets, Union3, Pantheon+, and DES-Dovekie, are consistent with each other within ∼ 1σ.
Forged by feedback: stellar properties of brightest group galaxies in cosmological simulations
(American Astronomical Society, 2026) Barré, Ruxin; Babul, Arif; Gozaliasl, Ghassem; Finoguenov, Alexis; Davé, Romeel; Padawer-Blatt, Aviv; Rennehan, Douglas; Saeedzadeh, Vida; Hough, Renier T; Quinn, Thomas R
We investigate how different galaxy formation models impact the stellar properties of brightest group galaxies (BGGs) in four cosmological simulations: Romulus, Simba, Simba-C, and Obsidian. The stellar masses, specific star formation rates, and mass-weighted stellar ages of the simulated BGGs are analyzed alongside those of observed BGGs from X-ray-selected galaxy groups in the Cosmic Evolution Survey (COSMOS) field. We find that the global properties and underlying evolutionary pathways of simulated BGG populations are strongly impacted by the strength and mechanism of their respective active galactic nucleus (AGN) feedback models, which play a critical role in regulating the growth of massive galaxies. Obsidian’s sophisticated three-regime AGN feedback model achieves the highest overall agreement with COSMOS observations, matching stellar property distributions, quenched fractions, and the evolution of star formation in increasingly massive systems. We find evidence suggesting that BGG populations of Obsidian and COSMOS undergo a gradual decline in star formation with stellar mass, in contrast to Simba and Simba-C, which display rapid quenching linked to the onset of powerful AGN jet feedback. By comparison, Romulus produces highly star-forming, under-quenched BGGs due to the inefficiency of its thermal AGN feedback in preventing cooling flows from fuelling BGG growth. The success of the Obsidian simulation demonstrates the importance of physically motivated subgrid prescriptions for realistically capturing the processes that shape BGGs and their dynamic group environments.
MIGHTEE-H i: mass models and dark matter properties
(Oxford University Press, 2026) Ponomareva, Anastasia; Mancera-Piña, Pavel; Vărăşteanu, Andreea; Glowacki, Marcin; Desmond, Harry; Jarvis, Matthew; Yasin, Tariq; Heywood, Ian; Maddox, Natasha; Adams, Elizabeth; Baes, Maarten; Gebek, Andrea; Kurapati, Sushma; Maksymowicz-Maciata, Michalina; Oman, Kyle; Pan, Hengxing; Prandoni, Isabella; Rajohnson, Sambatriniaina; Ruffa, Ilaria; Spekkens, Kristine
Measuring galaxy rotation curves is critical for inferring the properties of dark-matter haloes in the Lambda cold dark matter ($\Lambda$CDM) paradigm. We present H i rotation curves and mass models for 20 galaxies from the MIGHTEE survey. Using extended H i kinematics, we construct resolved mass models that include stellar, gaseous, and dark-matter components. Stellar masses are derived using 3.6 $\mu$m imaging under fixed mass-to-light ratio ($\Upsilon _{*} = M/L$) assumptions and are complemented, for the first time for a H i-selected sample, by spatially resolved $M/L$, obtained from multiwavelength spectral energy distribution fitting. We examine the ratio of baryonic to observed rotation velocity ($V_{\rm bar}/V_{\rm obs}$) at the characteristic radius $R_{2.2}$. Adopting a fixed $\Upsilon _\star = 0.5\, M_\odot /L_\odot$ yields a clear dependence of $V_{2.2}/V_{\rm obs}$ on galaxy luminosity, while adopting $\Upsilon _\star = 0.2\, M_\odot /L_\odot$ substantially weakens this trend. In contrast, the resolved $M/L$ analysis preserves the luminosity dependence while modifying the stellar contribution on a galaxy-by-galaxy basis, providing a more accurate representation of the underlying relation. We model the dark-matter haloes using Navarro–Frenk–White profiles and find that the different assumptions for a fixed a $M/L$ systematically shift galaxies relative to the theoretical stellar-to-halo mass and baryonic-to-halo mass relations, while the spatially varying $M/L$ yields the closest agreement with theoretical benchmarks within $\Lambda$CDM. We therefore demonstrate that future investigations of the dark matter properties of galaxies using rotation curves need to account for varying $M/L$ across individual galaxy profiles and between galaxies in order to obtain accurate measurements of the dark matter, and therefore test $\Lambda$CDM.
COSMOS Spectroscopic Redshift Compilation (First Data Release): 488,000 Redshifts Encompassing Two Decades of Spectroscopy
(American Astronomical Society, 2025) Vaccari, Mattia; Khostovan, Ali Ahmad; Kartaltepe, Jeyhan S.
We present the COSMOS Spectroscopic Redshift Compilation encompassing ∼20 yr of spectroscopic redshifts within a 10 deg2 area centered on the 2 deg2 COSMOS legacy field. This compilation contains 487,666 redshifts of 266,284 unique objects from 138 individual programs up to z ∼ 8 with median stellar mass ∼108.4–1010 M⊙ (redshift dependent). Rest-frame NUVrJ colors and star formation rate–stellar mass correlations show that the compilation primarily contains low-to-intermediate-mass star-forming and massive, quiescent galaxies at z < 1.25 and mostly low-mass bursty star-forming galaxies at z > 2. Sources in the compilation cover a diverse range of environments, including protoclusters such as “Hyperion.” The full compilation is 50% spectroscopically complete by i ∼ 23.4 mag and Ks ∼ 21.6 mag; however, this is redshift dependent. Spatially, the compilation is >50% (>30%) complete within the central (outer) region limited to i < 24 mag and Ks < 22.5 mag, separately. We demonstrate how the compilation can be used to validate photometric redshifts and investigate calibration metrics. By training self-organizing maps on COSMOS2020/Classic and projecting the compilation onto it, we find key subpopulations currently lacking spectroscopic coverage, including z < 1 intermediate-mass quiescent and low-/intermediate-mass bursty star-forming galaxies, z ∼ 2 massive quiescent galaxies, and z > 3 massive star-forming galaxies. This highlights how combining self-organizing maps with our compilation can provide guidance for future spectroscopic observations to get a complete spectroscopic view of galaxy populations. Lastly, the compilation will undergo periodic data releases incorporating new spectroscopic redshifts and providing a lasting legacy resource for the community.
Euclid: Discovery of bright z ≃ 7 Lyman-break galaxies in UltraVISTA and Euclid COSMOS
(EDP Sciences, 2026) Jarvis, M.J; Varadaraj, R.G; Bowler, R.A.A
We present a search for z ≃ 7 Lyman-break galaxies using the 1.72 deg2 near-infrared (NIR) UltraVISTA survey in the COSMOS field, reaching 5σ depths in Y of 26.2. We incorporated deep Euclid optical and Euclid + Spitzer NIR imaging for a full spectral energy distribution (SED) fitting analysis. We found 289 candidate galaxies at 6.5 ≤ z ≤ 7.5 covering −22.6 ≤ MUV ≤ −20.2, faint enough to overlap with Hubble Space Telescope studies. We conducted a separate selection by including complementary Euclid performance verification imaging (reaching 5σ depths of 26.3), yielding 140 galaxies in 0.65 deg2, with 38 sources unique to this sample. We computed the rest-frame UV luminosity function (UV LF) from our samples, extending below the knee (M∗ = −21.14+0.28−0.25). We find that the shape of the UV LF is consistent with both a Schechter function and a double power law (DPL) at the magnitudes probed by this sample, with a DPL preferred at MUV < −22.5 when bright-end results are included. The UltraVISTA + Euclid sample provides a clean measurement of the LF due to the overlapping NIR filters identifying molecular absorption features in the SEDs of ultra-cool dwarf interlopers, and additional faint galaxies were recovered. A comparison with JWST LFs at z > 7 suggests a gentle evolution in the bright-end slope, although this is limited by a lack of robust bright-end measurements at z > 9. We forecast that in the Euclid Deep Fields, the removal of contaminant ultra-cool dwarfs as point sources will be possible at JE < 24.5. Finally, we present a high-equivalent-width Lyman-α emitter candidate identified by combining HSC, VISTA, and Euclid broadband photometry, highlighting the synergistic power these instruments will have in the Euclid Auxiliary Fields for identifying extreme sources in the epoch of reionisation.
Vz-GAL: Probing Cold Molecular Gas in Dusty Star-forming Galaxies at z = 1-6
(American Astronomical Society, 2026) Baker, Andrew J; Prajapati, Prachi; Riechers, Dominik
We present the first results of Vz-GAL, a high-redshift CO(J = 1-0) large survey with the Karl G. Jansky Very Large Array, targeting 92 Herschel-selected, infrared-luminous, dusty star-forming galaxies at redshifts 1-6. These sources are selected based on having redshifts and mid-/high-J CO transitions from the NOrthern Extended Millimeter Array z-GAL survey. We successfully detect CO(J = 1-0) emission in 90/92 galaxies at the expected positions and redshifts, including nine tentative detections at 2σ-3σ significance, and CO(J = 2-1) emission in 10 of these galaxies. The CO(J = 1-0) luminosities suggest apparent gas masses in the range μ M H 2 = (2-20) × 1011 (αCO/4.0) M⊙, which implies gas depletion times of 50-600 Myr. These timescales show similar spread as local ULIRGs, suggesting a self-regulatory mechanism that maintains a consistent star formation rate per unit gas mass in starbursts across redshifts. To quantify the contribution of “excitation correction” factors to gas mass estimates, we calculate median CO line brightness temperature ratios of r21 = 0.88 ± 0.25, r31 = 0.61 ± 0.22, r41 = 0.49 ± 0.15, r51 = 0.47 ± 0.13, and r61 = 0.28 ± 0.13. Accounting for these corrections results in a reduced scatter in “gas mass-star formation rate” relations. We also find a median log(Formula presented)for a subsample of 23 sources, consistent with the ratios derived for local star-forming galaxies. Together, our findings are in agreement with common conditions in the cold gas reservoirs among star-forming galaxies over a broad range in star formation modes, efficiencies, and scales.

Browse

Recent Submissions