arXiv subjects

A. Coulais

Publications and source records attributed to A. Coulais.

At least 19 recordsLinked to original sources

arXiv2026

The evolution of the mid-infrared spectrum of SN 1987A observed with the JWST/MIRI-MRS

Supernova (SN) 1987A provides a unique laboratory for investigating many aspects of SN physics and evolution. An observation at Day 12927 (35.4 yr) since the explosion with the Mid-Infrared Instrument (MIRI) Medium Resolution Spectrometer (MRS) on the James Webb Space Telescope (JWST) provided the first spatially resolved spectroscopic study of SN 1987A in the mid-IR, yielding insights into the evolution of dust, the ejecta, the equatorial ring (ER), and shocks in the system. Here we present a second epoch with MIRI/MRS at Day 13311 (36.4 yr) allowing the mid-IR spatially resolved spectroscopic temporal evolution of SN 1987A to be probed for the first time. Analysis of the ER-dominated dust continuum showed little evolution between Days 12927 and 13311. However, a spatial analysis reveals the inner ER to be fading while the outermost regions are brightening. Broad ejecta emission lines detected at Day 12927 are evolving rapidly, driven by the recent onset of the ejecta/equatorial ring interaction in the northeast and southwest of the ER. Most lines from the ER show no change during the 384 days between the epochs, though some such as [Ne II] and [Ar II] have faded. We identify mid-IR H2 emission associated with the ejecta for the first time. Using the near- and mid-IR [Fe II] lines as density and temperature diagnostics of the ejecta in the interaction region we find it likely that the dense inner Fe-rich ejecta has now reached the reverse shock. Continued monitoring of SN 1987A is essential to observe the evolving ejecta/ER interaction and dust components.

astro-ph.HE↗

arXiv2025

Detection of CO$_2$, CO, and H$_2$O in the atmosphere of the warm sub-Saturn HAT-P-12b

The chemical composition of warm gas giant exoplanet atmospheres (with Teq < 1000 K) is not well known due to the lack of observational constraints. HAT-P-12 b is a warm, sub-Saturn-mass transiting exoplanet that is ideal for transmission spectroscopy. One transit of HAT-P-12 b was observed with JWST NIRSpec in the 2.87--5.10 $μ$m range with a resolving power of $\sim$1000. The JWST data are combined with archival observations from HST WFC3 covering the 1.1--1.7 $μ$m range. The data were analysed using two data reduction pipelines and two atmospheric retrieval tools. Atmospheric simulations using chemical forward models were performed. CO2, CO, and H2O are detected at 12.2, 4.1, and 6.0 $σ$ confidence, respectively. Their volume mixing ratios are consistent with an atmosphere of $\sim10\times$ solar metallicity and production of CO2 by photochemistry. CH4 is not detected and seems to be lacking, which could be due to a high intrinsic temperature with strong vertical mixing or other phenomena. SO2 is also not detected and its production seems limited by low upper atmosphere temperatures ($\sim$500 K at $P<10^{-3}$ bar derived from one-dimensional retrievals), insufficient to produce it in detectable quantities ($\gtrsim$ 800 K required according to photochemical models). Retrievals indicate the presence of clouds between 2 and 269 mbar. This study points towards an atmosphere for HAT-P-12 b that could be enriched in carbon and oxygen with respect to its host star. When including the production of CO2 via photochemistry, an atmospheric metallicity that is close to Saturn's can explain the observations. Metallicities inferred for other gas giant exoplanets based on their CO2 mixing ratios may need to account for its photochemical production pathways. This may impact studies on mass-metallicity trends and links between exoplanet atmospheres, interiors, and formation history.

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arXiv2025

JWST/MIRI observations of the young TWA 27 system: hydrocarbon disk chemistry, silicate clouds, evidence for a CPD

The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) enables the characterisation of young self-luminous gas giants at previously inaccessible wavelengths, revealing physical processes in gas, dust, and clouds. We characterise the young planetary system TWA 27 (2M1207) in the mid-infrared (MIR), studying the atmosphere and disk spectra of the M9 brown dwarf TWA 27A and its L6 planetary-mass companion TWA 27b. We obtained data with the MIRI Medium Resolution Spectrometer (MRS) from 4.9 to 20 um, and MIRI Imaging in the F1000W and F1500W filters. We applied high-contrast imaging methods to extract the companion's spectral energy distribution up to 15 um at 0.78 arcsec separation and a contrast of 60. Combining these with published JWST/NIRSpec spectra, we analysed the 1-20 um range using self-consistent atmospheric grids and 0D slab models for molecular disk emission. The atmosphere of TWA 27A is well fitted by a BT-SETTL model with Teff 2780 K, log g 4.3, plus a 740 K blackbody for the inner disk rim. The disk shows at least 11 organic molecules, with no water or silicate dust emission detected. The atmosphere of TWA 27b is matched by a Teff 1400 K low-gravity model with extinction, best fit by the ExoREM grid. MIRI spectra and photometry for TWA 27b reveal a silicate cloud absorption feature between 8-10 um and significant (>5 sigma) infrared excess at 15 um consistent with circumplanetary disk emission. These MIRI observations provide new insights into TWA 27, revealing diverse features to study the formation and evolution of circumplanetary disks and young dusty atmospheres.

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arXiv2025

A crude but efficient pipeline for JWST MIRI imager : the case of sn1987A

Most of the space projects or large observatories do have official tools like simulators, end-to-end pipelines developed during years by a large team of contributors. They are like {\em cathedrals}. In this paper, we show that very simplistic code using basic operators provided by high level language like GDL allows to write quickly high quality code to process raw data into scientifically validated outputs. This is {\em bazaar}. In this paper we argument why we consider large infrastructure should be designed to allow small ones to benefit from it and allow to graft better alternative processing at very low cost.

astro-ph.IM↗

arXiv2025

GDL 1.1, a smart and green language

GDL, a free interpreter for the IDL language, continues to develop smoothly, driven by feedback and requests from an increasingly active and growing user base, especially since GDL was made available on GitHub. Among the most notable features introduced in recent years are stable Widgets; extensive testing on M1, M2, and M3 processors; excellent computational performance (including OpenMP support) demonstrated across a comprehensive benchmark; simplified compilation and installation processes; and the availability of SHMMAP and Bridge functions, which enable concurrent GDL runs on shared RAM in HPC environments. As developers of GDL, we believe this language holds a valuable place in today's world, where efficiency and low-power computing are essential. GDL (not to mention IDL), written in C/C++, demonstrates exceptional efficiency in "real-world" benchmarks, making it one of the few interpreted languages that can truly be considered "green." Moreover, it is likely the only interpreter accompanied by a vast collection of free, well-tested, and proven astronomical procedures developed by colleagues over the years. GDL also stands out for its suitability for long-term projects, thanks to its stable and reliable syntax.

astro-ph.IM↗

arXiv2024

Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A

The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy finding narrow infrared emission lines of argon and sulphur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.

astro-ph.HE↗

arXiv2024

Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS

Supernova (SN) 1987A is the nearest supernova in $\sim$400 years. Using the {\em JWST} MIRI Medium Resolution Spectrograph, we spatially resolved the ejecta, equatorial ring (ER) and outer rings in the mid-infrared 12,927 days after the explosion. The spectra are rich in line and dust continuum emission, both in the ejecta and the ring. Broad emission lines (280-380~km~s$^{-1}$ FWHM) seen from all singly-ionized species originate from the expanding ER, with properties consistent with dense post-shock cooling gas. Narrower emission lines (100-170~km~s$^{-1}$ FWHM) are seen from species originating from a more extended lower-density component whose high ionization may have been produced by shocks progressing through the ER, or by the UV radiation pulse associated with the original supernova event. The asymmetric east-west dust emission in the ER has continued to fade, with constant temperature, signifying a reduction in dust mass. Small grains in the ER are preferentially destroyed, with larger grains from the progenitor surviving the transition from SN into SNR. The ER is fit with a single set of optical constants, eliminating the need for a secondary featureless hot dust component. We find several broad ejecta emission lines from [Ne~{\sc ii}], [Ar~{\sc ii}], [Fe~{\sc ii}], and [Ni~{\sc ii}]. With the exception of [Fe~{\sc ii}]~25.99$μ$m, these all originate from the ejecta close to the ring and are likely being excited by X-rays from the interaction. The [Fe~{\sc ii}]~5.34$μ$m to 25.99$μ$m line ratio indicates a temperature of only a few hundred K in the inner core, consistent with being powered by ${}^{44}$Ti decay.

astro-ph.HE↗

arXiv2024

JWST MIRI Imager Observations of Supernova SN 1987A

There exist very few mid-infrared (IR) observations of supernovae (SNe) in general. Therefore, SN 1987A, the closest visible SN in 400 years, gives us the opportunity to explore the mid-IR properties of SNe, the dust in their ejecta and surrounding medium, and to witness the birth of a SN remnant (SNR). The James Webb Space Telescope (JWST), with its high spatial resolution and extreme sensitivity, gives a new view on these issues. We report on the first imaging observations obtained with the Mid-InfraRed Instrument (MIRI). We build temperature maps and discuss the morphology of the nascent SNR. Our results show that the temperatures in the equatorial ring (ER) are quite non-uniform. This could be due to dust destruction in some parts of the ring, as had been assumed in some previous works. We show that the IR emission extends beyond the ER, illustrating the fact that the shock wave has now passed through this ring to affect the circumstellar medium on a larger scale. Finally, while sub-mm Atacama Large Millimeter Array (ALMA) observations have hinted at the location of the compact remnant of SN 1987A, we note that our MIRI data have found no such evidence.

astro-ph.SR↗

arXiv2023

Planck 2013 results X. Energetic particle effects: characterization, removal, and simulation

We describe the detection, interpretation, and removal of the signal resulting from interactions of high energy particles with the \Planck\ High Frequency Instrument (HFI). There are two types of interactions: heating of the 0.1\,K bolometer plate; and glitches in each detector time stream. The transient responses to detector glitch shapes are not simple single-pole exponential decays and fall into three families. The glitch shape for each family has been characterized empirically in flight data and these shapes have been used to remove glitches from the detector time streams. The spectrum of the count rate per unit energy is computed for each family and a correspondence is made to the location on the detector of the particle hit. Most of the detected glitches are from Galactic protons incident on the die frame supporting the micro-machined bolometric detectors. In the \Planck\ orbit at L2, the particle flux is around $5\,{\rm cm}^{-2}\,{\rm s}^{-1}$ and is dominated by protons incident on the spacecraft with energy $>$39\,MeV, at a rate of typically one event per second per detector. Different categories of glitches have different signatures in the time stream. Two of the glitch types have a low amplitude component that decays over nearly 1\,s. This component produces excess noise if not properly removed from the time-ordered data. We have used a glitch detection and subtraction method based on the joint fit of population templates. The application of this novel glitch subtraction method removes excess noise from the time streams. Using realistic simulations, we find that this method does not introduce signal bias into the \Planck\ data.

astro-ph.CO↗

arXiv2023

JWST NIRSpec observations of Supernova 1987A -- from the inner ejecta to the reverse shock

We present initial results from JWST NIRSpec integral field unit observations of the nearby Supernova (SN) 1987A. The observations provide the first spatially-resolved spectroscopy of the ejecta and equatorial ring (ER) over the 1-5 μm range. We construct 3D emissivity maps of the [Fe I] 1.443 μm line from the inner ejecta and the He I 1.083 μm line from the reverse shock (RS), where the former probes the explosion geometry and the latter traces the structure of the circumstellar medium. We also present a model for the integrated spectrum of the ejecta. The [Fe I] 3D map reveals a highly-asymmetric morphology resembling a broken dipole, dominated by two large clumps with velocities of ~2300 km/s. We also find evidence that the Fe-rich inner ejecta have started to interact with the RS. The RS surface traced by the He I line extends from just inside the ER to higher latitudes on both sides of the ER with a half-opening angle ~45 degrees, forming a bubble-like structure. The spectral model for the ejecta allows us to identify the many emission lines, including numerous H_2 lines. We find that the H_2 is most likely excited by far-UV emission, while the metal lines ratios are consistent with a combination of collisional excitation and recombination in the low-temperature ejecta. We also find several high-ionization coronal lines from the ER, requiring a temperature > 2 \times 10^6 K.

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arXiv2022

Candidate cosmic filament in the GJ526 field, mapped with the NIKA2 camera

Distinctive large-scale structures have been identified in the spatial distribution of optical galaxies up to redshift z ~ 1. In the more distant universe, the relationship between the dust-obscured population of star-forming galaxies observed at millimetre wavelengths and the network of cosmic filaments of dark matter apparent in all cosmological hydrodynamical simulations is still under study. Using the NIKA2 dual-band millimetre camera, we mapped a field of ~ 90 arcminutes^2 in the direction of the star GJ526 simultaneously in its 1.15-mm and 2.0-mm continuum wavebands to investigate the nature of the quasi-alignment of five sources found ten years earlier with the MAMBO camera at 1.2 mm. We find that these sources are not clumps of a circumstellar debris disc around this star as initially hypothesized. Rather, they must be dust-obscured star-forming galaxies, or sub-millimetre galaxies (SMGs), in the distant background. The new NIKA2 map at 1.15 mm reveals a total of seven SMGs distributed in projection on the sky along a filament-like structure crossing the whole observed field. Furthermore, we show that the NIKA2 and supplemental Herschel photometric data are compatible with a model of the spectral energy distributions (SEDs) of these sources when a common redshift of 2.5 and typical values of the dust parameters for SMGs are adopted. Hence, we speculate that these SMGs might be located in a filament of the distant `cosmic web'. The length of this candidate cosmic filament crossing the whole map is at least 4 cMpc (comoving), and the separations between sources are between 0.25 cMpc and 1.25 cMpc at this redshift, in line with expectations from cosmological simulations. Nonetheless, further observations to determine the precise spectroscopic redshifts of these sources are required to definitively support this hypothesis of SMGs embedded in a cosmic filament of dark matter.

astro-ph.CO↗

arXiv2021

Overdensity of SubMillimiter Galaxies in the GJ526 Field mapped with the NIKA2 Camera

Using the NIKA2 dual band millimeter camera installed on the IRAM30m telescope, we have mapped a relatively large field (~70 arcmin^2) in the direction of the star GJ526 to investigate the nature of the sources found with the MAMBO camera at 1.2 mm ten years earlier. We have found that they must be dust-obscured galaxies (SMGs) in the background beyond the star. The new NIKA2 map at 1.15 mm reveals additional sources and, in fact, an overdensity of SMGs predominantly distributed along a filament-like structure in projection on the sky across the whole observed field. We speculate this might be a cosmic filament at high redshift as revealed in cosmological hydrodynamical simulations. Measurement of spectroscopic redshifts of the SMGs in the candidate filament is required now for a definitive confirmation of the nature of the structure.

astro-ph.GA↗

arXiv2020

MIRISim: A Simulator for the Mid-Infrared Instrument on JWST

The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST), has imaging, four coronagraphs and both low and medium resolution spectroscopic modes . Being able to simulate MIRI observations will help commissioning of the instrument, as well as get users familiar with representative data. We designed the MIRI instrument simulator (MIRISim) to mimic the on-orbit performance of the MIRI imager and spectrometers using the Calibration Data Products (CDPs) developed by the MIRI instrument team. The software encorporates accurate representations of the detectors, slicers, distortions, and noise sources along the light path including the telescope's radiative background and cosmic rays. The software also includes a module which enables users to create astronomical scenes to simulate. MIRISim is a publicly available Python package that can be run at the command line, or from within Python. The outputs of MIRISim are detector images in the same uncalibrated data format that will be delivered to MIRI users. These contain the necessary metadata for ingestion by the JWST calibration pipeline.

astro-ph.IM↗

arXiv2018

Atmospheric characterization of directly imaged exoplanets with JWST/MIRI

The Mid-Infrared instrument (MIRI) on board the James Webb Space Telescope will perform the first ever characterization of young giant exoplanets observed by direct imaging in the 5-28 microns spectral range. This wavelength range is key for both determining the bolometric luminosity of the cool known exoplanets and for accessing the strongest ammonia bands. In conjunction with shorter wavelength observations, MIRI will enable a more accurate characterization of the exoplanetary atmospheric properties. Here we consider a subsample of the currently known exoplanets detected by direct imaging and we discuss their detectability with MIRI, either using the coronagraphic or the spectroscopic modes. By using the Exo-REM atmosphere model we calculate the mid-infrared emission spectra of fourteen exoplanets, and we simulate MIRI coronagraphic or spectroscopic observations. Specifically we analyze four coronagraphic observational setups, which depend on (i) the target-star and reference-star offset (0, 3, 14 mas), (ii) the wave-front-error (130, 204 nm rms), (iii) the telescope jitter amplitude (1.6, 7 mas). We then determine the signal-to-noise and integration time values for the coronagraphic targets whose planet-to-star contrasts range from 3.9 to 10.1 mag. We conclude that all the MIRI targets should be observable with different degrees of difficulty, which depends on the final in-flight instrument performances. Furthermore, we test for detection of ammonia in the atmosphere of the coolest targets. Finally, we present the case of HR 8799 b to discuss what MIRI observations can bring to the knowledge of a planetary atmosphere, either alone or in combination with shorter wavelength observations.

astro-ph.EP↗

arXiv2018

Planck 2015 results. XXIV. Cosmology from Sunyaev-Zeldovich cluster counts

We present cluster counts and corresponding cosmological constraints from the Planck full mission data set. Our catalogue consists of 439 clusters detected via their Sunyaev-Zeldovich (SZ) signal down to a signal-to-noise ratio of 6, and is more than a factor of 2 larger than the 2013 Planck cluster cosmology sample. The counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. Taking advantage of the larger catalogue, we extend our analysis to the two-dimensional distribution in redshift and signal-to-noise. We use mass estimates from two recent studies of gravitational lensing of background galaxies by Planck clusters to provide priors on the hydrostatic bias parameter, $(1-b)$. In addition, we use lensing of cosmic microwave background (CMB) temperature fluctuations by Planck clusters as an independent constraint on this parameter. These various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of tension with those from the Planck analysis of primary fluctuations in the CMB; for the lowest estimated values of $(1-b)$ the tension is mild, only a little over one standard deviation, while it remains substantial ($3.7\,σ$) for the largest estimated value. We also examine constraints on extensions to the base flat $Λ$CDM model by combining the cluster and CMB constraints. The combination appears to favour non-minimal neutrino masses, but this possibility does little to relieve the overall tension because it simultaneously lowers the implied value of the Hubble parameter, thereby exacerbating the discrepancy with most current astrophysical estimates. Improving the precision of cluster mass calibrations from the current 10%-level to 1% would significantly strengthen these combined analyses and provide a stringent test of the base $Λ$CDM model.

astro-ph.CO↗

arXiv2017

Planck 2015 results. XX. Constraints on inflation

We present the implications for cosmic inflation of the Planck measurements of the cosmic microwave background (CMB) anisotropies in both temperature and polarization based on the full Planck survey. The Planck full mission temperature data and a first release of polarization data on large angular scales measure the spectral index of curvature perturbations to be $n_\mathrm{s} = 0.968 \pm 0.006$ and tightly constrain its scale dependence to $d n_s/d \ln k =-0.003 \pm 0.007$ when combined with the Planck lensing likelihood. When the high-$\ell$ polarization data is included, the results are consistent and uncertainties are reduced. The upper bound on the tensor-to-scalar ratio is $r_{0.002} < 0.11$ (95% CL), consistent with the B-mode polarization constraint $r< 0.12$ (95% CL) obtained from a joint BICEP2/Keck Array and Planck analysis. These results imply that $V(ϕ) \propto ϕ^2$ and natural inflation are now disfavoured compared to models predicting a smaller tensor-to-scalar ratio, such as $R^2$ inflation. Three independent methods reconstructing the primordial power spectrum are investigated. The Planck data are consistent with adiabatic primordial perturbations. We investigate inflationary models producing an anisotropic modulation of the primordial curvature power spectrum as well as generalized models of inflation not governed by a scalar field with a canonical kinetic term. The 2015 results are consistent with the 2013 analysis based on the nominal mission data.

astro-ph.CO↗

arXiv2016

Planck intermediate results. LII. Planet flux densities

Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the six Planck High Frequency Instrument frequency bands (100-857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates of the brightness of Jupiter and Saturn at the three frequencies of the Planck Low Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time-variability of these planets. The majority of the planet flux density estimates are limited by systematic errors, but still yield better than 1% measurements in many cases. Applying data from Planck HFI, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn's rings to the planet's total flux density suggests a best fit value for the spectral index of Saturn's ring system of $β_\mathrm{ring} = 2.30\pm0.03$ over the 30-1000 GHz frequency range. The average ratio between the Planck-HFI measurements and the adopted model predictions for all five planets (excluding Jupiter observations for 353 GHz) is 0.997, 0.997, 1.018, and 1.032 for 100, 143, 217, and 353 GHz, respectively. Model predictions for planet thermodynamic temperatures are therefore consistent with the absolute calibration of Planck-HFI detectors at about the three-percent-level. We compare our measurements with published results from recent cosmic microwave background experiments. In particular, we observe that the flux densities measured by Planck HFI and WMAP agree to within 2%. These results allow experiments operating in the mm-wavelength range to cross-calibrate against Planck and improve models of radiative transport used in planetary science.

astro-ph.EP↗

arXiv2016

Planck 2015 results. XXI. The integrated Sachs-Wolfe effect

This paper presents a study of the ISW effect from the Planck 2015 temperature and polarization data release. The CMB is cross-correlated with different LSS tracers: the NVSS, SDSS and WISE catalogues, and the Planck 2015 lensing map. This cross-correlation yields a detection at $4\,σ$, where most of the signal-to-noise is due to the Planck lensing and NVSS. In fact, the ISW effect is detected only from the Planck data (through the ISW-lensing bispectrum) at $\approx 3\,σ$, which is similar to the detection level achieved by combining the cross-correlation signal coming from all the catalogues. The ISW signal allow us to detect $Ω_Λ$ at more than $3\,σ$. This cross-correlation analysis is performed only with the Planck temperature data, since the polarization scales available in the 2015 release do not permit significant improvement of the CMB-LSS cross-correlation detectability. Nevertheless, polarization data is used to study the anomalously large ISW signal previously reported through the stacking of CMB features at the locations of known superstructures. We find that the current Planck polarization data do not exclude that this signal could be caused by the ISW effect. In addition, the stacking of the Planck lensing map on the locations of superstructures exhibits a positive cross-correlation with these large-scale structures. Finally, we have improved our previous reconstruction of the ISW temperature fluctuations by combining the information encoded in all the previously mentioned LSS tracers. In particular, we construct a map of the ISW secondary anisotropies and the corresponding uncertainties map, obtained from simulations. We also explore the reconstruction of the ISW anisotropies caused by the LSS traced by the 2MPZ survey by directly inverting the density field into the gravitational potential field.

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