Spectral Fitting Research Articles

CANUCS: An Updated Mass and Magnification Model of A370 with JWST

We present an updated mass and magnification model of galaxy cluster A370 using new NIRCam, NIRISS, and NIRSpec data from the Canadian NIRISS Unbiased Cluster Survey (CANUCS). Using Lenstool and a combination of archival Hubble Space Telescope (HST) and MUSE data with new JWST data as constraints, we derive an improved gravitational lensing model and extract magnifications of background galaxies with uncertainties. Using our best fit model, we perform a search for new multiply imaged systems via predicted positions. We report no new multiply imaged systems with identifiable redshifts, likely due to already very deep HST and Spitzer data but confirm a z ∼ 8 multiply imaged system by measuring its redshift with NIRISS and NIRSpec spectra. We find that the overall shape of the critical curve for a source at z = 9.0 is similar to previous models of A370, with small changes. We investigate the z ∼ 8 galaxy with two images observable with an apparent magnitude in the F125W band of 26.0 ± 0.2 and 25.6 ± 0.1. After correcting for the magnifications of the images, 7.4−0.3+0.5 and 9.4−0.4+0.5 , we use spectral energy distribution fitting to find an intrinsic stellar mass of log(M */M ⊙) = 7.49−0.05+0.04 , intrinsic star formation rate of 2.8−0.3+0.4 M ⊙ yr−1, and M UV of −21.3 −0.2+0.2 , which is close to the knee of the luminosity function at that redshift. Our model, and corresponding magnification, shear, and convergence maps are available on request and will be made publicly available on MAST in a CANUCS data release (doi:10.17909/ph4n-6n76).

O2-Dependence of reactions of 1,2-dimethoxyethanyl and 1,2-dimethoxyethanylperoxy isomers

Reaction mechanisms of R˙ and ROO˙ radicals derived from low-temperature oxidation of 1,2-dimethoxyethane (CH3O(CH2)2OCH3) were investigated using speciation from multiplexed photoionization mass spectrometry (MPIMS) measurements via Cl-initiated oxidation, in conjunction with electronic structure calculations. The experiments were conducted at 5 bar, from 450 K – 650 K, and O2 concentrations from 1 · 1014 cm–3 – 6 · 1018 cm–3 to probe the effects on competing reaction channels of 1,2-dimethoxyethanyl (R˙) and 1,2-dimethoxyethanylperoxy (ROO˙) isomers. Several species were detected with photoionization spectral fitting – ethene, formaldehyde, methyl vinyl ether, and 2-methoxyacetaldehyde – and, as determined by electronic structure calculations, may form via unimolecular decomposition of 1,2-dimethoxyethanyl or 1,2-dimethoxyethanylperoxy. O2-dependent yield ratios show that the formation pathways for all species undergo a competition between O2-addition and unimolecular decomposition. Adiabatic ionization energies were also calculated and utilized along with exact mass determinations to infer contributions for other species derived exclusively from first- and second-O2-addition, including 1,2-dimethoxyethene, cyclic ethers, and dicarbonyls.In addition to species formed from conventional low-temperature oxidation pathways, an important conclusion is derived from the detection of species produced from an O2-addition step involving ĊH2CH2OCH3 (R˙′), which forms via prompt dissociation of the primary 1,2-dimethoxyethanyl radical (ĊH2O(CH2)2OCH3). Species derived from R˙′ + O2 – 1,3-dioxolane and methyl acetate – were detected at [O2] = 1.2 · 1017 cm–3 and formed on timescales parallel to the main R˙ + O2 reactions. In addition, ion signal at m/z 106 was detected and increased with O2 concentration from which connections are drawn to ketohydroperoxides produced by Q˙′OOH + O2. Detection of such species indicate that β-scission of 1,2-dimethoxyethanyl is sufficiently facile such that timescales of R˙′ + O2 compete with conventional R˙ + O2 pathways.

Methane retrieval from MethaneAIR using the CO2 proxy approach: a demonstration for the upcoming MethaneSAT mission

Abstract. Reducing methane (CH4) emissions from the oil and gas (O&G) sector is crucial for mitigating climate change in the near term. MethaneSAT is an upcoming satellite mission designed to monitor basin-wide O&G emissions globally, providing estimates of emission rates and helping identify the underlying processes leading to methane release in the atmosphere. MethaneSAT data will support advocacy and policy efforts by helping to track methane reduction commitments and targets set by countries and industries. Here, we introduce a CH4 retrieval algorithm for MethaneSAT based on the CO2 proxy method. We apply the algorithm to observations from the maiden campaign of MethaneAIR, an airborne precursor to the satellite that has similar instrument specifications. The campaign was conducted during winter 2019 and summer 2021 over three major US oil and gas basins. Analysis of MethaneAIR data shows that measurement precision is typically better than 2 % at a 20×20 m2 pixel resolution, exhibiting no strong dependence on geophysical variables, e.g., surface reflectance. We show that detector focus drifts over the course of each flight, likely due to thermal gradients that develop across the optical bench. The impacts of this drift on retrieved CH4 can mostly be mitigated by including a parameter that squeezes the laboratory-derived, tabulated instrument spectral response function (ISRF) in the spectral fit. Validation against coincident EM27/SUN retrievals shows that MethaneAIR values are generally within 1 % of the retrievals. MethaneAIR retrievals were also intercompared with retrievals from the TROPOspheric Monitoring Instrument (TROPOMI). We estimate that the mean bias between the instruments is 2.5 ppb, and the latitudinal gradients for the two data sets are in good agreement. We evaluate the accuracy of MethaneAIR estimates of point-source emissions using observations recorded over the Permian Basin, an O&G basin, based on the integrated-mass-enhancement approach coupled with a plume-masking algorithm that uses total variational denoising. We estimate that the median point-source detection threshold is 100–150 kg h−1 at the aircraft's nominal above-surface observation altitude of 12 km. This estimate is based on an ensemble of Weather Research and Forecasting (WRF) large-eddy simulations used to mimic the campaign's conditions, with the threshold for quantification set at approximately twice the detection threshold. Retrievals from repeated basin surveys indicate the presence of both persistent and intermittent sources, and we highlight an example from each case. For the persistent source, we infer emissions from a large O&G processing facility and estimate a leak rate between 1.6 % and 2.1 %, higher than any previously reported emission levels from a facility of its size. We also identify a ruptured pipeline that could increase total basin emissions by 2 % if left unrepaired; this pipeline was discovered 2 weeks before it was found by its operator, highlighting the importance of regular monitoring by future satellite missions. The results showcase MethaneAIR's capability to make highly accurate, precise measurements of methane dry-air mole fractions in the atmosphere, with a fine spatial resolution (∼ 20×20 m2) mapped over large swaths (∼ 100×100 km2) in a single flight. The results provide confidence that MethaneSAT can make such measurements at unprecedentedly fine scales from space (∼ 130×400 m2 pixel size over a target area measuring ∼ 200×200 km2), thereby delivering quantitative data on basin-wide methane emissions.

Jaxspec : A fast and robust Python library for X-ray spectral fitting

Inferring spectral parameters from X-ray data is one of the cornerstones of high-energy astrophysics, and is achieved using software stacks that have been developed over the last 20 years and more. However, as models get more complex and spectra are obtained with higher resolutions, these established software solutions become more feature-heavy, difficult to maintain and less efficient. We present jaxspec a Python package for performing this task quickly and robustly in a fully Bayesian framework. Based on the JAX ecosystem jaxspec allows the generation of differentiable likelihood functions compilable on core or graphical process units (GPUs), enabling the use of robust algorithms for Bayesian inference. We demonstrate the effectiveness of jaxspec samplers, in particular the no U-turn sampler, using a composite model and comparing what we obtain with the existing frameworks. We also demonstrate its ability to process high-resolution spectroscopy data using original methods by reproducing the results of the Hitomi collaboration on the Perseus cluster, while solving the inference problem using variational inference on a GPU. We obtain identical results when compared to other software and approaches, meaning that jaxspec provides reliable results while being $ 10$ times faster than existing alternatives. In addition, we show that variational inference can produce convincing results even on high-resolution data in less than 10 minutes on a GPU. With this package, we aim to pursue the goal of opening up X-ray spectroscopy to the existing ecosystem of machine learning and Bayesian inference, enabling researchers to apply new methods to solve increasingly complex problems in the best possible way. Our long-term ambition is the scientific exploitation of the data from the newAthena X-ray Integral Field Unit (X-IFU).

Analyzing JWST/NIRSpec Hydrogen Line Detections at TWA 27B: Constraining Accretion Properties and Geometry

Hydrogen lines from forming planets are crucial for understanding planet formation. However, the number of planetary hydrogen line detections is still limited. Recent JWST/NIRSpec observations have detected Paschen and Brackett hydrogen lines at TWA 27 B (2M1207b). Although classified as a planetary- mass companison (PMC) rather than a planet due to its large mass ratio to the central star, TWA 27 B’s hydrogen line emissions are expected to be same as the planetary one, given its small mass (≈5M J). We aim to constrain the accretion properties and accretion geometry of TWA 27 B, contributing to our understanding of hydrogen-line emission mechanisms common to both PMCs and planets. We conduct spectral fitting of four bright hydrogen lines (Pa-α, Pa-β, Pa-γ, Pa-δ) with an accretion-shock emission model tailored for forming planets. We estimate the mass accretion rate at Ṁ≈3×10−9MJyr−1 with our fiducial parameters, though this is subject to an uncertainty of up to factor of ten. Our analysis also indicates a dense accretion flow, n ≳ 1013 cm−3 just before the shock, implying a small accretion-shock filling factor f f on the planetary surface (f f ≲ 5 × 10−4). This finding suggests that magnetospheric accretion is occurring at TWA 27 B. Additionally, we carry out a comparative analysis of hydrogen-line emission color to identify the emission mechanism, but the associated uncertainties proved too large for definitive conclusions. This underscores the need for further high-precision observational studies to elucidate these emission mechanisms fully.

The effect of mass and morphology on the mass assembly of galaxies

The pace at which galaxies grew into their current stellar masses and how this growth is regulated is still not fully understood, nor is the role that morphology plays in this process. We applied full spectral fitting techniques with pyPipe3D to the MaNGA sample to obtain its star formation and stellar mass histories and used these to investigate the mass assembly of galaxies by measuring how their specific star formation correlates to their stellar mass at different look-back times. We find that the correlation between these two parameters was shallower in the past. Galaxies used to have similar mass doubling times and the current negative correlation between the specific star formation and M$_ is primarily due to more massive galaxies 'dropping' off the main sequence earlier than less massive ones. Additionally, selecting the galaxies into bins based on their present-day morphology shows a segregation in specific star formation rate (sSFR) that is maintained even at high look-back times, showing that the factors that determine which morphology a galaxy ends up in are in place at very early times. Similarly, selecting them based on their current star formation status shows that, on average, currently retired galaxies used to have slightly a higher sSFR before the drop-off, whereas galaxies that have continued to form stars until today had a lower sSFR initially. We compare our results to a set of cosmic surveys, finding partial agreement in our results with several of them, though with significant offsets in redshift. Finally, we discuss how our results fit with certain theoretical models on galaxy evolution as well as cosmological simulations.

An all-sky catalogue of stellar reddening values

Context. When observing astronomical objects, we have to deal with extinction (i.e. the absorption and scattering of the emitted radiation by dust and gas between the source and the observer). Interstellar extinction depends on the location of the object and the wavelength. The different extinction laws describing these effects are difficult to estimate for a small sample of stars. Aims. Many sophisticated and automatic methods have recently been developed for estimating astrophysical parameters (age and metallicity, for example) depending on the reddening, which is normally treated as a free parameter within the corresponding estimations. However, many reddening values for stars have been published over the last few decades, most of which include observations in the ultraviolet, which are essential for a good estimation but are essentially no longer taken into account. Methods. We searched the literature through the end of 2022 for published independent reddening values of stellar objects based on various methods that exclude estimates from reddening maps. In addition, we present new reddening estimates based on the classical photometric indices in the Geneva, Johnson, and Strömgren-Crawford systems. These are based on well-established and reliable calibrations. Results. After a careful identification procedure and quality assessment of the data, we calculated the mean reddening values of 157 631 individual available measurements for 97 826 objects. We compared our results with the ones from recent automatic pipeline values, including those from the Gaia consortium. In addition, we chose star cluster members to compare their mean values with estimates for the corresponding aggregates. Within the different references, we find several statistically significant offsets and trends and discuss possible explanations for them. Conclusions. Our new catalogue can serve as a starting point for calibrating and testing automatic tools such as isochrone and spectral energy distribution fitting. Our sample covers the whole sky, including the Galactic field, star clusters, and Magellanic Clouds, and so can be used for a variety of astrophysical studies.

Tully-Fisher relation of late-type galaxies at 0.6 ≤ z ≤ 2.5

We present a study of the stellar and baryonic Tully-Fisher relation within the redshift range of 0.6 ≤ z ≤ 2.5, utilizing observations of star-forming galaxies. This dataset comprises of disk-like galaxies spanning a stellar mass range of 8.89 ≤ log(Mstar [M⊙]) ≤ 11.5, a baryonic mass range of 9.0 ≤ log(Mbar [M⊙]) ≤ 11.5, and a circular velocity range of 1.65 ≤ log(Vc [km/s]) ≤ 2.85. We estimated the stellar masses of these objects using spectral energy distribution fitting techniques, while the gas masses were determined via scaling relations. Circular velocities were directly derived from the rotation curves (RCs), after meticulously correcting for beam smearing and pressure support. Our analysis confirms that our sample adheres to the fundamental mass-size relations of galaxies and reflects the evolution of velocity dispersion in galaxies, in line with previous findings. This reaffirms the reliability of our photometric and kinematic parameters (i.e., Mstar and Vc), thereby enabling a comprehensive examination of the Tully-Fisher relation. To attain robust results, we employed a novel orthogonal likelihood fitting technique designed to minimize intrinsic scatter around the best-fit line, as required at high redshifts. For the stellar Tully-Fisher relation, we obtained a slope of α = 3.03 ± 0.25, an offset of β = 3.34 ± 0.53, and an intrinsic scatter of ζint = 0.08 dex. Correspondingly, the baryonic Tully-Fisher relation yielded α = 3.21 ± 0.28, β = 3.16 ± 0.61, and ζint = 0.09 dex. Our findings indicate a subtle deviation in the stellar and baryonic Tully-Fisher relation with respect to local studies, which is most likely due to the evolutionary processes governing disk formation.

Not-so-little Red Dots: Two Massive and Dusty Starbursts at z ∼ 5–7 Pushing the Limits of Star Formation Discovered by JWST in the COSMOS-Web Survey

We present the properties of two candidate massive (M ⋆ ∼ 1011 M ⊙) and dusty (A v > 2.5 mag) galaxies at z = 5–7 in the first 0.28 deg2 of the COSMOS-Web survey. One object is spectroscopically confirmed at z spec = 5.051, while the other has a robust z phot = 6.7 ± 0.3. Thanks to their extremely red colors (F277W–F444W ∼ 1.7 mag), these galaxies satisfy the nominal color selection for the widely studied “little red dot” (LRD) population with the exception of their spatially resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of spectral energy distribution fitting tools and star formation histories, we estimate the stellar masses to be log(M⋆)=11.32−0.15+0.07M⊙ and log(M⋆)=11.2−0.2+0.1M⊙ , respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of ϵ ⋆ ∼ 0.25 and ϵ ⋆ ∼ 0.5. Both are significantly higher than what is commonly observed in lower-z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high-z Lyman-Break Galaxies and some non-AGN-dominated LRDs, such “extended” LRDs represent another population that may require very efficient star formation at early times.

Insight-HXMT, NICER, and NuSTAR Views to the Newly Discovered Black Hole X-Ray Binary Swift J151857.0–572147

The systematic properties are largely unknown for the black hole X-ray binary Swift J151857.0–572147 newly discovered in the 2024 outburst. The nature of a black hole can be completely defined by specifying the mass and dimensionless spin parameter. Therefore, accurate measurement of the two fundamental parameters is important for understanding the nature of black holes. The joint spectral fitting of a reflection component with simultaneous observations from Insight-HXMT, NICER, and NuSTAR reveals for the first time a black hole dimensionless spin of 0.84−0.26+0.17 and an inclination angle of 21.1−3.6+4.5 degrees for this system. Monitoring of the soft state by NICER results in disk flux and temperature following Fdisk∝Tin3.83±0.17 . For the standard thin disk, Ldisk≈4πRin2σTin4 , so the relationship between the flux and temperature of the disk we measured indicates that the inner radius of the disk is stable and the disk is in the innermost stable circular orbit. With an empirical relation built previously between the black hole outburst profile and the intrinsic power output, the source distance is estimated as 5.8 ± 2.5 kpc according to the outburst profile and peak flux observed by Insight-HXMT and NICER. Finally, a black hole mass of 3.67 ± 1.79–8.07 ± 4.20M ⊙ can be inferred from a joint diagnostic of the aforementioned parameters measured for this system. This system is also consistent with most black hole X-ray binaries with high spin and a mass in the range of 5–20 M ⊙.

Measurement of Stark-split beam and carbon charge exchange emissions for simultaneous B-field and temperature/rotation analysis at DIII-D.

A set of two newly designed, single-channel Czerny-Turner spectrometers has been deployed at the DIII-D tokamak for measurements of the motional Stark effect (MSE) split beam emission and the C6+ (CVI) carbon charge exchange recombination (CER) emission at high spectral (δλ = 0.13nm) and temporal (1-5kHz) resolution. High throughput optics (f/# = 2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. The MSE emission allows for spectral fitting of the magnitude and direction of the local B-field, while the carbon emission yields local ion temperature and toroidal rotation information. To reduce so-called Doppler broadening of the MSE emission, a new channel-specific variable lens-masking approach has been developed. Experimental data collected from the 2023 DIII-D experimental campaign demonstrate the signal quality and instrument fidelity for both diagnostic measurements. Moreover, initial CER data analysis shows a clear evolution of the toroidal rotation during edge localized modes. Initial progress on the advanced MSE model, including a new validated ray-trace model of the DIII-D collection optics, is shown via sensitivity analysis.

High-resolution Elemental Abundance Measurements of Cool JWST Planet Hosts Using AutoSpecFit: An Application to the Sub-Neptune K2-18b’s Host M Dwarf

We present an in-depth, high-resolution spectroscopic analysis of the M dwarf K2-18, which hosts a sub-Neptune exoplanet in its habitable zone. We show our technique to accurately normalize the observed spectrum, which is crucial for a proper spectral fitting. We also introduce a new automatic, line-by-line, model-fitting code, AutoSpecFit, which performs an iterative χ 2 minimization process to measure individual elemental abundances of cool dwarfs. We apply this code to the star K2-18, and measure the abundance of 10 elements: C, O, Na, Mg, Al, K, Ca, Sc, Ti, and Fe. We find these abundances to be moderately supersolar, except for Fe, with a slightly subsolar abundance. The accuracy of the inferred abundances is limited by the systematic errors due to uncertain stellar parameters. We also derive the abundance ratios associated with several planet-building elements such as Al/Mg, Ca/Mg, Fe/Mg, and (a solar-like) C/O = 0.568 ± 0.026, which can be used to constrain the chemical composition and the formation location of the exoplanet. On the other hand, the planet K2-18 b has attracted considerable interest, given the JWST measurements of its atmospheric composition. Early JWST studies reveal an unusual chemistry for the atmosphere of this planet, which is unlikely to be driven by formation in a disk of unusual composition. The comparison between the chemical abundances of K2-18 b from future JWST analyses and those of the host star can provide fundamental insights into the formation of this planetary system.

Accretion Geometry of GX 339–4 in the Hard State: AstroSat View

We perform broadband (0.7–100 keV) spectral analysis of five hard state observations of the low-mass black hole X-ray binary GX 339–4 taken by AstroSat during the rising phase of three outbursts from 2019 to 2022. We find that the outburst in 2021 was the only successful/full outburst, while the source was unable to make the transition to the soft state during the other two outbursts in 2019 and 2022. Our spectral analysis employs two different model combinations, requiring two separate Comptonizing regions and their associated reflection components and soft X-ray excess emission. The harder Comptonizing component dominates the overall bolometric luminosity, while the softer one remains relatively weak. Our spectral fits indicate that the disk evolves with the source luminosity, where the inner disk radius decreases with increasing luminosity. However, the disk remains substantially truncated throughout all the observations at the source luminosity of ∼2%–8%× of the Eddington luminosity. We note that our assumption of the soft X-ray excess emission as disk blackbody may not be realistic, and this kind of soft excess may arise due the nonhomogeneity in the disk/corona geometry. Our temporal analysis deriving the power density spectra suggests that the break frequency increases with the source luminosity. Furthermore, our analysis demonstrates a consistency between the inner disk radii estimated from the break frequency of the power density spectra and those obtained from the reflection modeling, supporting the truncated disk geometry in the hard state.

The Massive and Distant Clusters of WISE Survey 2: A Stacking Analysis Investigating the Evolution of Star Formation Rates and Stellar Masses in Groups and Clusters

The evolution of galaxies depends on their masses and local environments; understanding when and how environmental quenching starts to operate remains a challenge. Furthermore, studies of the high-redshift regime have been limited to massive cluster members, owing to sensitivity limits or small fields of view when the sensitivity is sufficient, intrinsically biasing the picture of cluster evolution. In this work, we use stacking to investigate the average star formation history of more than 10,000 groups and clusters drawn from the Massive and Distant Clusters of WISE Survey 2. Our analysis covers near-ultraviolet to far-infrared wavelengths, for galaxy overdensities at 0.5 ≲ z ≲ 2.54. We employ spectral energy distribution fitting to measure the specific star formation rates (sSFRs) in four annular apertures with radii between 0 and 1000 kpc. At z ≳ 1.6, the average sSFR evolves similarly to the field in both the core and the cluster outskirts. Between z¯=1.60 and z¯=1.35 , the sSFR in the core drops sharply, and it continues to fall relative to the field sSFR at lower redshifts. We interpret this change as evidence that the impact of environmental quenching dramatically increases at z ∼ 1.5, with the short time span of the transition suggesting that the environmental quenching mechanism dominant at this redshift operates on a rapid timescale. We find indications that the sSFR may decrease with increasing host halo mass, but lower-scatter mass tracers than the signal-to-noise ratio are needed to confirm this relationship.

Improvements in precision and accuracy of complex- relative to real-domain linear combination model spectral fitting not necessarily recovered by zero filling.

Although the information obtained from in vivo proton magnetic resonance spectroscopy (1H MRS) presents a complex-valued spectrum, spectral quantification generally employs linear combination model (LCM) fitting using the real spectrum alone. There is currently no known investigation comparing fit results obtained from LCM fitting over the full complex data versus the real data and how these results might be affected by common spectral preprocessing procedure zero filling. Here, we employ linear combination modeling of simulated and measured spectral data to examine two major ideas: first, whether use of the full complex rather than real-only data can provide improvements in quantification by linear combination modeling and, second, to what extent zero filling might influence these improvements. We examine these questions by evaluating the errors of linear combination model fits in the complex versus real domains against three classes of synthetic data: simulated Lorentzian singlets, simulated metabolite spectra excluding the baseline, and simulated metabolite spectra including measured in vivo baselines. We observed that complex fitting provides consistent improvements in fit accuracy and precision across all three data types. While zero filling obviates the accuracy and precision benefit of complex fitting for Lorentzian singlets and metabolite spectra lacking baselines, it does not necessarily do so for complex spectra including measured in vivo baselines. Overall, performing linear combination modeling in the complex domain can improve metabolite quantification accuracy relative to real fits alone. While this benefit can be similarly achieved via zero filling for some spectra with flat baselines, this is not invariably the case for all baseline types exhibited by measured in vivo data.

Computer-assisted regional-residual gravity anomaly separation with regularized first- and second-order derivatives

The regional-residual separation of gravity anomalies in crustal and mineral exploration was a graphical-based procedure before the advent of fast digital computers and the need for more efficient algorithms to process large data sets. However, since requiring the supervision of an experienced interpreter, the results, once obtained with graphical procedures, are often accepted as second to none in producing anomalies with geologic significance. Numerical methods based on spectral filtering and robust polynomial fitting have worked in many scenarios but seem not fully effective in replicating in algorithms the kind of results once obtained with interpreter-assisted graphical methods. We develop a computer-assisted regional residual separation (CARRS) procedure implemented by a set of short MATLAB scripts; in many aspects, CARRS simulates the operations of former graphical methods but requires few decisions and minor handwork from the interpreter. CARRS applies robust polynomial fitting to points with a low horizontal gradient and a vertical second-order derivative; thus, selecting fitting points as a real interpreter would do with graphical approaches in outlining the regional field. A regularized procedure is used to calculate the stable first- and second-order derivatives. Companion MATLAB codes allow for the replication of our results and further exploration with different threshold levels to identify flat domain regions. CARRS is illustrated with airborne gravity data CPRM-1123, freely available to download. A data window of the residual field is used to analyze the distribution of cassiterite deposits in greisen zones of the Paleoproterozoic Velho Guilherme granites in the Amazon Craton, as their distribution appears in the observed gravity anomaly and its corresponding residual field.

Blueberry galaxies up to 200 Mpc and their optical and infrared properties

Context. Dwarf highly star-forming galaxies (SFGs) dominated the early Universe and are considered the main driver of its reionization. However, direct observations of these distant galaxies are mainly confined to rest-frame ultraviolet and visible light, limiting our understanding of their complete properties. Therefore, it is still paramount to study their local analogs, the green pea (GP) and blueberry (BB) galaxies. Aims. This work aims to expand our knowledge of BBs by identifying a new sample that is closer and in the southern sky. Methods. In addition to the already known BBs, this new sample will allow for a statistically significant study of their properties probed by visible and infrared (IR) light. By utilizing the HECATE catalog, which provides optical and IR photometry and characterization of galaxies, along with data from Pan-STARSS and SDSS, this study selects and analyzes a new sample of BBs. We employed spectral energy distribution fitting to derive homogeneous measurements of star-formation rates and stellar masses. Additionally, we measured emission-line fluxes, including He II λ4686, through spectral fitting. Results. Through this work, we identified 48 BBs, of which 40 were first recognized as such, with the nearest at 19 Mpc. Fourteen of the BBs are in the south sky. The BBs tend to be extremely IR red in both WISE W1 – W2 and W2 – W3 colors, distinguishing them from typical SFGs. Dwarf SFGs with higher specific star-formation rates tend to have redder IR colors. Conclusions. Blueberry galaxies stand out as the most intensely star-forming sources in the local Universe among dwarf galaxies. They are intrinsically bluer in visible light, redder in the infrared, and less massive. They also have higher specific star-formation rates, equivalent widths, lower metallicities, and the most strongly ionized interstellar medium compared to typical SFGs and GPs.

The CXSFIT spectral fitting code: Past, present and future.

Magnetically confined plasma experiments generate a wealth of spectroscopic data. The first step toward extracting physical parameters is to fit a spectral model to the often complex spectra. The CXSFIT (Charge eXchange Spectroscopy FITting) spectral fitting code was originally developed for fitting charge exchange spectra on JET from the late 1980s onward and has been further developed over decades to keep up with the needs of the users. The primary use is to efficiently fit a large number of spectra with many constrained Gaussian spectral lines of which the physical parameters can be coupled in a user-friendly manner. More recent additions to the code include time-dependent couplings between parameters, flexible background subtraction, and a non-linear coupling scheme between fit parameters. The latter was a pre-requisite for implementing Zeeman and motional Stark effect multiplets in the library of spectral features. The ability to save and replay "fit recipes," even when multiple iterations are required, has ensured the traceability of the results and is one of the keys to the longevity and success of the code. The code is also in use on other tokamaks (AUG, ST-40) and to fit data from other spectroscopic diagnostics on JET. In this paper, we document the current capabilities and philosophy behind the structure of the code, including some of the algorithms used to calculate spectral features numerically efficiently. We also provide an outline of how CXSFIT could be transferred into a framework that would be able to meet the spectral fitting requirements of future devices, such as ITER.

Identifying and Characterizing Infrared Excesses in the Spitzer Kepler Survey (SpiKeS)

We report our search for infrared excesses in the Spitzer/Infrared Array Camera survey of the Kepler field at 3.6 and 4.5 μm. The Spitzer Kepler Survey contains ∼190,000 targets, which we reduce to ∼117,000 targets after applying multiple filters to arrive at a high-quality sample for spectral energy distribution fitting. Of the ∼117,000, we find 11 Sun-like stars (T eff ∼ 6000 K) with infrared excesses of high significance (>4σ) ranging from 10% to 40% above the photosphere at 4.5 μm, which is characteristic of debris disk systems. Blackbody fits of the infrared excesses for the 11 debris disk candidates suggest dust temperatures of 400–1400 K. None of the candidates have reported exoplanet detections. High-quality 1–5 μm or longer spectra or photometry would be necessary to confirm the candidates as debris disk systems.

Understanding the unusual life of the Cartwheel galaxy using stellar populations

Collisional ring galaxies (RiGs) are the result of the impact between two galaxies, with one of them passing close to the centre of the other, piercing its gaseous and stellar disc. In this framework, the impact generates a shock wave front that propagates within the disc of the target galaxy soon after the encounter, producing a characteristic expanding ring-shaped structure. RiGs represent one of the most extreme environments in which we can study the physical properties of galaxies and the transformations they undergo during collisions. The paradigm RiG is the Cartwheel galaxy at z = 0.03. This galaxy has been the object of both theoretical and observational studies, but the details of the mechanisms that lead to its peculiar morphology of double rings with connecting spokes and to its physical properties are still far from clear. To shed light on the history of the Cartwheel galaxy, we performed a spatially resolved analysis as a function of galactocentric distance, exploiting spectroscopic data from VLT/MUSE observations combined with photometric data covering a large wavelength range, from the UV GALEX to the IR JWST/MIRI. Using full-index fitting of the stellar spectra, an analysis of the nebular emission, and joint full spectral and photometry fitting, we derived stellar ages, gas and stellar metallicities, and star formation histories (SFHs) in four spatially distinct regions of the galaxy. We find that, apart from the peculiar morphology, a large fraction of the Cartwheel galaxy is not affected by the recent impact from the companion bullet, and retains the characteristics of a typical spiral galaxy. On the contrary, the outer ring is strongly affected by the recent impact, and is completely dominated by stars formed not earlier than ∼400 Myr ago. Our picture suggests that the collision shock wave, while moving forward to the external region of the galaxy, drags the already formed stars, sweeping the inner areas outwards, as proposed by recent collision models. At the same time, the ages found in the external ring are older than the predicted timescale of the ring expansion after the collision.