The profiles of several diffuse interstellar bands (DIBs) show substructures that resemble unresolved rotational bands of the electronic transitions of large molecules. Their profiles show clear variations along the lines of sight, probing different physical conditions. Analysis of variations in such profiles can constrain the sizes and geometries of the DIB carriers and the physical conditions of the interstellar environments in which they reside. We investigate the properties of rotational band contours for perpendicular transitions in planar, oblate symmetric top molecules and compare such contours to the observed profile of the lambda 6614 DIB. We examine the shapes of the profiles as a function of the model parameters: the rotational constant B in the ground state, the relative change in the rotational constant of the excited state Delta B, the Coriolis coupling constant zeta, the rotational excitation temperature T rot, and line width sigma. We determine which parameters can reproduce the overall triple-peak profile of the lambda 6614 DIB and the variations across different lines of sight. We find that the substructures in the lambda 6614 DIB can be reproduced with an oblate top with rotational constant B = (2.2 +/- 1.8) x 10-3 cm-1, Delta B = (-7.2 +/- 0.4) x 10-2%, and Coriolis coupling constant zeta = (2.9 +/- 0.1) x 10-1 cm-1. Thus, if the lambda 6614 DIB carrier conforms to an oblate symmetric top geometry, it is most likely to be a similar to 54C atom molecule. The profile variations correspond to changes in the rotational temperature from 81 to 92 K. We furthermore find that the intrinsic line width is a key parameter for each sightline and requires a range from 0.14 to 0.21 cm-1 (or 2.8 to 4.2 km s-1) across our sample to reproduce the observations. The intrinsic line width of the lambda 6614 DIB correlates with the width of the CH+ lines, suggesting an origin in the same environment. We conclude that the lambda 6614 DIB carrier resides in the same hot gas at low density that is probed by CH+.
Pits and skylights are circular to elliptical, rimless, steep-sided depressions on planetary surfaces formed through gravitational collapse, which are of interest for astrobiological investigation and future space exploration. This is due to their ability to signify the presence of, or allow access to, underground cave systems such as lava tubes. The Lunar Pit Atlas contains 16 such features situated within mare regions that were partly discovered via the automated PitScan tool, which was limited by searchable latitudes and data coverage. In order to search for pits and skylights within these unmapped regions, we have trained a series of Mask R-CNN (Region-based Convolutional Neural Network) models on various combinations of Lunar and Martian remote-sensing imagery to detect Lunar pits and skylights. The best-performing model, named ESSA (Entrances to Sub-Surface Areas), was trained upon all available training data with a ResNet50 backbone. During testing on imagery of the famous Mare Tranquillitatis Pit and self-produced mosaics of proposed lava tube collapses, ESSA achieved average F1-scores of 82.4 and 93.7% for the bounding boxes and predicted masks, respectively. Despite only having surveyed approximate to 1.92% of the Lunar maria, ESSA has detected two previously uncatalogued skylights: the South Marius Hills and Bel'kovich A Pits (SMHP and BAP)-which are possible candidates for cave entrances on the Moon.
Context.Mid-infrared emission features are important probes of the properties of ionized gas and hot or warm molecular gas, which are difficult to probe at other wavelengths. The Orion Bar photodissociation region (PDR) is a bright, nearby, and frequently studied target containing large amounts of gas under these conditions. Under the “PDRs4All” Early Release Science Program for JWST, a part of the Orion Bar was observed with MIRI integral field unit (IFU) spectroscopy, and these high-sensitivity IR spectroscopic images of very high angular resolution (0.2″) provide a rich observational inventory of the mid-infrared (MIR) emission lines, while resolving the HIIregion, the ionization front, and multiple dissociation fronts.Aims.We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST.Methods.The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths.Results.We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of HIrecombination lines arising from the ionized gas layer bordering the PDR. The HIline ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by HeIlines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the NeIII/NeII, SIV/SIII, and ArIII/ArIIratios trace the conditions in the ionized layer bordering the PDR, while FeIII/FeIIand NiIII/NiIIexhibit a different behavior, as there are significant contributions to FeIIand NiIIfrom the neutral PDR gas. We observe the pure-rotational H2lines in the vibrational ground state from 0–0S(1) to 0–0S(8), and in the first vibrationally excited state from 1–1S(5) to 1–1 S(9). We derive H2excitation diagrams, and for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (~700 K) component representative of an average gas temperature, and one nonthermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0–0 S (6) to S (8) lines.
Background Identifying stars belonging to different classes is vital in order to build up statistical samples of different phases and pathways of stellar evolution. In the era of surveys covering billions of stars, an automated method of identifying these classes becomes necessary. Methods Many classes of stars are identified based on their emitted spectra. In this paper, we use a combination of the multi-class multi-label Machine Learning (ML) method XGBoost and the PySSED spectral-energy-distribution fitting algorithm to classify stars into nine different classes, based on their photometric data. The classifier is trained on subsets of the SIMBAD database. Particular challenges are the very high sparsity (large fraction of missing values) of the underlying data as well as the high class imbalance. We discuss the different variables available, such as photometric measurements on the one hand, and indirect predictors such as Galactic position on the other hand. Results We show the difference in performance when excluding certain variables, and discuss in which contexts which of the variables should be used. Finally, we show that increasing the number of samples of a particular type of star significantly increases the performance of the model for that particular type, while having little to no impact on other types. The accuracy of the main classifier is ∼0.7 with a macro F1 score of 0.61. Conclusions While the current accuracy of the classifier is not high enough to be reliably used in stellar classification, this work is an initial proof of feasibility for using ML to classify stars based on photometry.
C-terminal alpha-amidated peptides are attractive therapeutic targets, but preparative methods to access amidated pharmaceuticals are limited both on lab and manufacturing-scale. Here we report a straightforward and scalable approach to the C-terminal alpha-amidation of peptides and proteins from cysteine-extended polypeptide precursors. This amidation protocol consists of three highly efficient steps: 1) selective cysteine thiol substitution with a photolabel, 2) photoinduced decarboxylative elimination and 3) enamide cleavage by simple acidolysis or inverse electron demand Diels-Alder reaction. We provide a blueprint for applying this protocol to the semi-recombinant production of therapeutically relevant targets where gram scale C-terminal alpha-amidation is achieved in a photoflow reactor on a recombinantly prepared peptide YY analogue and a GLP-1/amylin co-agonist precursor peptide. Robust performance of this reaction cascade in flow highlights the potential of this chemistry to enable amidated drug leads to enter development that would not be viable on commercial scale using existing technology. C-terminal alpha-amidated peptides are attractive therapeutic targets, but preparative methods to access amidated pharmaceuticals are limited both on lab and manufacturing-scale. Here, the authors report a straightforward and scalable approach to the C-terminal alpha-amidation of peptides and proteins from cysteine-extended polypeptide precursors.
Mid-infrared emission features probe the properties of ionized gas, and hot or warm molecular gas. The Orion Bar is a frequently studied photodissociation region (PDR) containing large amounts of gas under these conditions, and was observed with the MIRI IFU aboard JWST as part of the "PDRs4All" program. The resulting IR spectroscopic images of high angular resolution (0.2") reveal a rich observational inventory of mid-IR emission lines, and spatially resolve the substructure of the PDR, with a mosaic cutting perpendicularly across the ionization front and three dissociation fronts. We extracted five spectra that represent the ionized, atomic, and molecular gas layers, and measured the most prominent gas emission lines. An initial analysis summarizes the physical conditions of the gas and the potential of these data. We identified around 100 lines, report an additional 18 lines that remain unidentified, and measured the line intensities and central wavelengths. The H I recombination lines originating from the ionized gas layer bordering the PDR, have intensity ratios that are well matched by emissivity coefficients from H recombination theory, but deviate up to 10% due contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni, and show how certain line ratios vary between the five regions. We observe the pure-rotational H$_2$ lines in the vibrational ground state from 0-0 S(1) to 0-0 S(8), and in the first vibrationally excited state from 1-1 S(5) to 1-1 S(9). We derive H$_2$ excitation diagrams, and approximate the excitation with one thermal (~700 K) component representative of an average gas temperature, and one non-thermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model for the Orion Bar PDR and highlight the differences with the observations.
Context: There have been many attempts to identify families of diffuse interstellar bands (DIBs) with perfectly correlating band strengths. Although major efforts have been made to classify broadly based DIB families and important insights have been gained, no family has been identified with sufficient accuracy or statistical significance to prove that a series of selected DIBs originates from the same carrier. This can be attributed in part to the exclusive use of equivalent widths to establish DIB families. Aims: In a change of strategy, we search for DIBs that are highly correlated in both band strength and profile shape. This approach increases the chance of correlating DIBs being members of one family and originating from the same carrier molecule. We also search for correlations between DIB profile families and atomic interstellar lines, with the goal of further chemically constraining possible DIB carriers. Methods: We adapted the well-known method of time-series alignment to perform a spectral alignment; that is, DIB alignment. In a second step, we analysed the alignment results using a clustering analysis. This method required a statistically significant data set of DIB sight lines. The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) data were perfectly suited for this application. Results: We report eight DIB families with correlating strengths and profiles, as well as four previously unreported DIBs in the visual range, found using DIB alignment. All profile family members show Pearson correlation coefficients in band strength higher than 0.9. In particular, we report the 6614 - 6521 AA DIB pair, in which both DIBs show the same triple-peak substructure and an unprecedented band strength Pearson correlation coefficient of 0.9935. The presented approach opens up new perspectives that can guide the laboratory search for DIB carriers.
Stellar atmosphere modelling predicts the luminosity and temperature of a star, together with parameters such as the effective gravity and the metallicity, by reproducing the observed spectral energy distribution. Most observational data comes from photometric surveys, using a variety of passbands. We herein present the Python Stellar Spectral Energy Distribution (PySSED) routine, designed to combine photometry from disparate catalogues, fit the luminosity and temperature of stars, and determine departures from stellar atmosphere models such as infrared or ultraviolet excess. We detail the routine's operation, and present use cases on both individual stars, stellar populations, and wider regions of the sky. PySSED benefits from fully automated processing, allowing fitting of arbitrarily large datasets at the rate of a few seconds per star.
To optimally exploit past and current space missions there is a growing need for the development of new tools capable of processing and analysing large amounts of heterogeneous data sets. Artificial Intelligence (AI) is a powerful tool that is becoming more common in remote sensing applications and Big Data from space. A main challenge for their exploitation is the combination of data sets from different (spectral-imaging) instruments to produce high-quality products. The focus of this work is to develop data fusion tools for the Sentinel 2 and 3 missions from the EU Copernicus program. We propose two approaches, with different datasets, to tackle this challenge, where we try to solve, without any ground truth available, combining multi-spectral imagery with a spatial resolution factor difference of 30 while reconstructing a result with almost twice the spectral definition.
The JWST has captured the most detailed and sharpest infrared images ever taken of the inner region of the Orion Nebula, the nearest massive star formation region, and a prototypical highly irradiated dense photo-dissociation region (PDR). We investigate the fundamental interaction of far-ultraviolet photons with molecular clouds. The transitions across the ionization front (IF), dissociation front (DF), and the molecular cloud are studied at high-angular resolution. These transitions are relevant to understanding the effects of radiative feedback from massive stars and the dominant physical and chemical processes that lead to the IR emission that JWST will detect in many Galactic and extragalactic environments. Due to the proximity of the Orion Nebula and the unprecedented angular resolution of JWST, these data reveal that the molecular cloud borders are hyper structured at small angular scales of 0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are observed such as ridges, waves, globules and photoevaporated protoplanetary disks. At the PDR atomic to molecular transition, several bright features are detected that are associated with the highly irradiated surroundings of the dense molecular condensations and embedded young star. Toward the Orion Bar PDR, a highly sculpted interface is detected with sharp edges and density increases near the IF and DF. This was predicted by previous modeling studies, but the fronts were unresolved in most tracers. A complex, structured, and folded DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a complete view of the PDR, all the way from the PDR edge to the substructured dense region, and this allowed us to determine, in detail, where the emission of the atomic and molecular lines, aromatic bands, and dust originate.
Context. Three-dimensional (3D) distributions of the 862 nm diffuse interstellar band (DIB) carrier have been computed based on Gaia parallaxes and DIB catalogues, in parallel with 3D maps of dust extinction density. Three-dimensional maps provide local diagnostics and information on the distribution of structures in addition to line-of-sight (LOS) integrated quantities, and allow us to focus on poorly studied low-extinction areas. They make cross-matching with other catalogues possible through estimates of the DIB and extinction along any given path. Aims. We re-examined the relationships between the density of DIB carriers and the absorption and emission properties of spatially co-located dust. Along with laboratory identifications of carriers, these properties may shed light on the formation and evolution of this organic matter. They may also help to model dust emission and absorption properties in a more detailed way. Methods. We used the 3D maps of 862 nm DIBs and of dust extinction, as well as available DIB equivalent width (EW) catalogues and published measurements of parameters characterizing the dust extinction law and the dust emission. We studied the relationships between the extinction-normalized 862 nm DIB EW and the extinction level, the total-to-selective extinction ratio RV, and the dust far-IR emission spectral index beta. We re-visited the link between several DIBs and the UV absorption bump at 220 nm. Results. The ratio of the 862 nm DIB carrier density to the optical extinction density (DIBnorm862) is increasing in low-density clouds, confirming with local values the trend seen in the LOS data. In both cases, the coefficients of a fitted power law fall within the range of those measured towards SDSS high-latitude targets for 20 different bands, ranking this DIB among those with a high increase, above that of the broad 4430 & Aring; DIB. This is consistent with the recent measurement of a larger scale height above the Plane for the 862 nm DIB compared to that of the 4430 & Aring; DIB. Using map-integrated 862 nm DIB EWs and extinctions along the paths to APOGEE targets with published proxies R ' V for the total-to-selective extinction ratio, we found that, despite a large scatter, DIBnorm862 is positively correlated with R ' V for those stars with low to moderate extinctions (AV = 0.2 to 2-3 mag). Independently, using stars from the 862 nm DIB catalogue located outside the disk and for the same regime of extinction, DIBnorm862 is found to be globally anti-correlated with the Planck opacity spectral index beta. This is consistent with the observed anti-correlation between beta and R ' V. In the light of a recent result on the variability of the carbon/silicate ratio in dust grains as a source of this anti-correlation, it suggests that DIBnorm862 increases with the fraction of carbonaceous to silicate grains in the co-located dust, in agreement with the carbonaceous nature of DIB carriers and recent evidences for a spatial correlation between DIBnorm862 and the fluxes of carbon-rich ejecta of asymptotic giant branch (AGB) stars. At higher extinction both trends disappear, and there is evidence for a trend reversal. Regarding the link between the height of the 220 nm UV absorption bump and extinction-normalized EWs of DIBs, we found that two factors explain the absence of previous clear results: the correlation disappears when we move from sigma-type to zeta-type DIBs and/or from single-cloud LOSs to paths crossing multiple clouds distant from each other; zeta-type bands can be used to predict low and high values of the bump height, provided one adds a correcting factor linked to the ambient radiation field (e.g. the 5780/5797 DIB ratio). We show examples of simple models of the bump height based on the 5780 & Aring; band, the 5850 & Aring; band and the 5780/5797 DIB ratio. We also found an anti-correlation between DIBnorm and the width of the bump, which similarly disappears from sigma-type to zeta-type DIBs. This suggests that a fraction of the bump is generated outside the dense molecular clouds. Conclusions. There are complex relationships between DIBs and dust; however, massive measurements of DIBs and extinction and the derived 3D maps may provide some constraints on the density, the nature, and the contribution to extinction and emission of the co-located dust. This requires large stellar spectroscopic surveys and space-based measurements of UV extinction.
Background:Identifying stars belonging to different classes is vital in order to build up statistical samples of different phases and pathways of stellar evolution. In the era of surveys covering billions of stars, an automated method of identifying these classes becomes necessary. Methods:Many classes of stars are identified based on their emitted spectra. In this paper, we use a combination of the multi-class multi-label Machine Learning (ML) method XGBoost and the PySSED spectral-energy-distribution fitting algorithm to classify stars into nine different classes, based on their photometric data. The classifier is trained on subsets of the SIMBAD database. Particular challenges are the very high sparsity (large fraction of missing values) of the underlying data as well as the high class imbalance. We discuss the different variables available, such as photometric measurements on the one hand, and indirect predictors such as Galactic position on the other hand. Results:We show the difference in performance when excluding certain variables, and discuss in which contexts which of the variables should be used. Finally, we show that increasing the number of samples of a particular type of star significantly increases the performance of the model for that particular type, while having little to no impact on other types. The accuracy of the main classifier is ∼0.7 with a macro F1 score of 0.61. Conclusions:While the current accuracy of the classifier is not high enough to be reliably used in stellar classification, this work is an initial proof of feasibility for using ML to classify stars based on photometry.
We present JWST images of the well-known planetary nebula NGC 6720 (the Ring Nebula), covering wavelengths from 1.6 to 25 mu m. The bright shell is strongly fragmented with some 20 000 dense globules, bright in H-2, with a characteristic diameter of 0.2 arcsec and density n(H) similar to 10(5)-10(6) cm(-3). The shell contains a narrow ring of polycyclic aromatic hydrocarbon (PAH) emission. H-2 is found throughout the shell and also in the halo. H-2 in the halo may be located on the swept-up walls of a biconal polar flow. The central cavity is filled with high-ionization gas and shows two linear structures which we suggest are the edges of a biconal flow, seen in projection against the cavity. The central star is located 2 arcsec from the emission centroid of the cavity and shell. Linear features ('spikes') extend outward from the ring, pointing away from the central star. Hydrodynamical simulations reproduce the clumping and possibly the spikes. Around 10 low-contrast, regularly spaced concentric arc-like features are present; they suggest orbital modulation by a low-mass companion with a period of about 280 yr. A previously known much wider companion is located at a projected separation of about 15 000 au; we show that it is an M2-M4 dwarf. NGC 6720 is therefore a triple star system. These features, including the multiplicity, are similar to those seen in the Southern Ring Nebula (NGC 3132) and may be a common aspect of such nebulae.
(Abridged) We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the HII region to the atomic PDR (crossing the ionisation front (IF)), and the subsequent transition to the molecular PDR (crossing the dissociation front (DF)). We use high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science Program. The NIRSpec data reveal a forest of lines including, but not limited to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from H2, and ro-vibrational lines HD, CO, and CH+, most of them detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. We observe numerous smaller scale structures whose typical size decreases with distance from Ori C and IR lines from CI, if solely arising from radiative recombination and cascade, reveal very high gas temperatures consistent with the hot irradiated surface of small-scale dense clumps deep inside the PDR. The H2 lines reveal multiple, prominent filaments which exhibit different characteristics. This leaves the impression of a "terraced" transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star- and planet formation as well as galaxy evolution.
Over the past decades, libraries of stellar spectra have been used in a large variety of science cases, including as sources of reference spectra for a given object or a given spectral type. Despite the existence of large libraries and the increasing number of projects of large-scale spectral surveys, there is to date only one very high-resolution spectral library offering spectra from a few hundred objects from the southern hemisphere (UVES-POP) . We aim to extend the sample, offering a finer coverage of effective temperatures and surface gravity with a uniform collection of spectra obtained in the northern hemisphere. Between 2010 and 2020, we acquired several thousand echelle spectra of bright stars with the Mercator-HERMES spectrograph located in the Roque de Los Muchachos Observatory in La Palma, whose pipeline offers high-quality data reduction products. We have also developed methods to correct for the instrumental response in order to approach the true shape of the spectral continuum. Additionally, we have devised a normalisation process to provide a homogeneous normalisation of the full spectral range for most of the objects. We present a new spectral library consisting of 3256 spectra covering 2043 stars. It combines high signal-to-noise and high spectral resolution over the entire range of effective temperatures and luminosity classes. The spectra are presented in four versions: raw, corrected from the instrumental response, with and without correction from the atmospheric molecular absorption, and normalised (including the telluric correction).
With the increasing number of ongoing space missions for Earth Observation (EO), there is a need to enhance data products by combining observations from various remote sensing instruments. We introduce a new Transformer-based approach for data fusion, achieving up to a 10- to-30-fold increase in the spatial resolution of our hyperspectral data. We trained the network on a synthetic set of Sentinel-2 (S2) and Sentinel-3 (S3) images, simulated from the hyperspectral mission EnMAP (30 m resolution), leading to a fused product of 21 bands at a 30 m ground resolution. The performances were calculated by fusing original S2 (12 bands, 10, 20, and 60 m resolutions) and S3 (21 bands, 300 m resolution) images. To go beyond EnMap’s ground resolution, the network was also trained using a generic set of non-EO images from the CAVE dataset. However, we found that training the network on contextually relevant data is crucial. The EO-trained network significantly outperformed the non-EO-trained one. Finally, we observed that the original network, trained at 30 m ground resolution, performed well when fed images at 10 m ground resolution, likely due to the flexibility of Transformer-based networks.
(Abridged) Mid-infrared observations of photodissociation regions (PDRs) are dominated by strong emission features called aromatic infrared bands (AIBs). The most prominent AIBs are found at 3.3, 6.2, 7.7, 8.6, and 11.2 $\mu$m. The most sensitive, highest-resolution infrared spectral imaging data ever taken of the prototypical PDR, the Orion Bar, have been captured by JWST. We provide an inventory of the AIBs found in the Orion Bar, along with mid-IR template spectra from five distinct regions in the Bar: the molecular PDR, the atomic PDR, and the HII region. We use JWST NIRSpec IFU and MIRI MRS observations of the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288). We extract five template spectra to represent the morphology and environment of the Orion Bar PDR. The superb sensitivity and the spectral and spatial resolution of these JWST observations reveal many details of the AIB emission and enable an improved characterization of their detailed profile shapes and sub-components. While the spectra are dominated by the well-known AIBs at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 $\mu$m, a wealth of weaker features and sub-components are present. We report trends in the widths and relative strengths of AIBs across the five template spectra. These trends yield valuable insight into the photochemical evolution of PAHs, such as the evolution responsible for the shift of 11.2 $\mu$m AIB emission from class B$_{11.2}$ in the molecular PDR to class A$_{11.2}$ in the PDR surface layers. This photochemical evolution is driven by the increased importance of FUV processing in the PDR surface layers, resulting in a "weeding out" of the weakest links of the PAH family in these layers. For now, these JWST observations are consistent with a model in which the underlying PAH family is composed of a few species: the so-called 'grandPAHs'.
Context. The carbonaceous macromolecules imprinting the numerous absorptions called diffuse interstellar bands (DIBs) in astronomical spectra are omnipresent in the Galaxy and beyond. They represent a considerable reservoir of organic matter. However, their chemical formulae, formation, and destruction sites remain unknown. Their spatial distribution and the local relation to other interstellar species is key to tracing their role in the lifecycle of organic matter. Aims. Volume density maps bring local instead of line-of-sight distributed information and allow for new diagnostics to be captured. We present the first large-scale volume (3D) density map of a DIB carrier and compare it with an equivalent map of interstellar dust. Methods. The DIB carrier map was obtained through hierarchical inversion of similar to 202 000 measurements of the 8621 nm DIB obtained with the Gaia-RVS instrument. It covers about 4000 pc around the Sun in the Galactic plane. We built a dedicated interstellar dust map based on the extinction towards the same target stars. Results. At the similar or equal to 50 pc resolution of the maps, the shape of the 3D DIB distribution is found to be remarkably similar to the 3D distribution of dust. On the other hand, the DIB-to-dust local density ratio increases in low-dust areas. It is also increasing away from the disk, however, the minimum ratio is found to be shifted above the Galactic plane to Z=similar or equal to+50pc. Finally, the average ratio is also surprisingly found to increase away from the Galactic Center. We suggest that the three latter trends may be indications of a dominant contribution of material from the carbon-rich category of dying giant stars to the formation of the carriers. Our suggestion is based on recent catalogs of asymptotic giant branch (AGB) stars and estimates of the mass fluxes of their C-rich and O-rich ejecta.
In the era of big data and cloud storage and computing, new ways for scientists to approach their research are emerging, which impact directly how science progresses and discoveries are made. This development has led the European Space Agency (ESA) to establish a reference framework for space mission operation and exploitation by scientific communities: the ESA Datalabs (EDL). The guiding principle of the EDL concept is to move the user to the data and tools, and to enable users to publish applications (e.g. processors, codes, pipelines, analysis and visualisation tools) within a trusted environment, close to the scientific data, and permitting the whole scientific community to discover new science products in an open and FAIR approach.In this context we will present a proto-type science application (aka Sci-App) for the exploration and visualization of Mars and Venus using the SPICAM/V Level-2 data available from the ESA Planetary Science Archive (PSA). This demonstrator facilitates the extraction and compilation of scientific data from the PSA and ease their integration with other tools through VO interoperability thus increasing their scientific impact. The tool’s key modular functionalities are 1) interactive data query and retrieval (i.e. search archive metadata), 2) interactive visualisation (i.e. geospatial info of query results, data content display of spectra, atmospheric vertical profiles), 3) data manipulation (i.e. create local maps or data cubes), and 4) data analysis (in combination with other connected VO tools). The application allows users to select, visualise and analyse both Level 2A products, which consist of e.g. transmission and radiance spectra, and level 2B products, which consist of retrieved physical parameters, such as atmospheric aerosol properties and vertical density profiles for (trace) gases in the Martian or Venusian atmosphere.Our goal is to deploy the (containerised) Sci-App to the EDL and similar initiatives for uptake by the space science community. In the future, we expect to incorporate access to other Mars/Venus atmospheric data sets, particularly the measurements obtained with the NOMAD and ACS instruments on the ExoMars Trace Gas Orbiter. The community can also use this application as a starting point for their own tool development for other data products/missions.
Diffuse interstellar bands comprise hundreds of absorption features in the ISM. Most DIBs are observed in the optical, but some are in the IR. We observed 76 early-type stars at R=50,000 and S/N ratios of several hundreds using CRIRES. We measure DIBs around 1318, 1527, 1561, 1565, 1567, 1574 and/or 1624 nm. We detect a total of 6 DIB features and 17 likely stellar features assisted by a CMFGEN model. We also measured the DIBs at 1318 and 1527 nm using X-shooter towards ten Ceph. variables with 3.2 < E(B-V) < 6.5 and 4 stars at low values of water vapour. Correlation coeffs. of 0.73-0.96 are found comparing NIRDIB eq. width vs. E(B-V) and with r > 0.8 when comparing the NIR and optical DIBs 5705, 5780, 6203, 6283 and 6269 A. The 5797 A DIB is less well correlated with the NIDIBs. The "C60+" DIB at 9632 A is not well correlated with the 1318 nm DIB. Partial correlation coefficients using E(B-V) as the covariate were also determined. For stars earlier than B2, the 1318 nm DIB is affected by an emission line on its blue wing, likely stellar in nature, although we cannot rule out interstellar/circumstellar origin for example caused by by a DIB in emission. The 1318 nm DIB has a red wing and is reasonably well fitted by two gaussians. Neither the component ratios nor separation are correlated with 5780/5797 or E(B-V). EW(1318 nm) correlates with HI with EW(1318 nm)/E(B-V) decreasing with f(H2). Five pairs of stars within 1 am show similar 1318 nm DIB profiles. Variation in 1318 nm is seen in HD 145501/145502 and HD 168607/168625 pairs. CRIRES data for 17 stars separated by 6-14 months and 2 X-shooter sightlines separated by 9.9 yr were analysed. No time-variability is detected in the 5780, 5797 A, 1318 nm or 1527 nm DIBs. Tentative time variation is observed in the C60+ DIBs at 9577 and 9632 A towards HD 183143 although very close to the noise level with confirmation required.