Science Verification Data Research Articles

Full L- and M-band high resolution spectroscopy of the S CrA binary disks with VLT-CRIRES+

Context. The Cryogenic IR echelle Spectrometer (CRIRES) instrument at the Very Large Telescope (VLT) was in operation from 2006 to 2014. Great strides in characterizing the inner regions of protoplanetary disks were made using CRIRES observations in the L- and M-band at this time. The upgraded instrument, CRIRES+, became available in 2021 and covers a larger wavelength range simultaneously. Aims. Here, we present new CRIRES+ Science Verification data of the binary system S Coronae Australis (S CrA). We aim to characterize the upgraded CRIRES+ instrument for disk studies and provide new insight into the gas in the inner disk of the S CrA N and S systems. Methods. We analyze the CRIRES+ data taken in all available L- and M-band settings, providing spectral coverage from 2.9 to 5.5 μm. Results. We detect emission from 12CO (v = 1−0, v = 2−1, and v = 3−2), 13CO (v = 1−0), hydrogen recombination lines, OH, and H2O in the S CrA N disk. In the fainter S CrA S system, only the12 CO v = 1−0 and the hydrogen recombination lines are detected. The 12CO v = 1−0 emission in S CrA N and S shows two velocity components, a broad component coming from ~0.1 au in S CrA N and ~0.03 au in S CrA S and a narrow component coming from ~3 au in S CrA N and ~5 au in S CrA S. We fit local thermodynamic equilibrium slab models to the rotation diagrams of the two S CrA N velocity components and find that they have similar column densities (~8×1016−4×1017 cm−2), but that the broad component is coming from a hotter and narrower region. Conclusions. Two filter settings, M4211 and M4368, provide sufficient wavelength coverage for characterizing CO and H2O at ~5 μm, in particular covering low- and high-J lines. CRIRES+ provides spectral coverage and resolution that are crucial complements to low-resolution observations, such as those with JWST, where multiple velocity components cannot be distinguished.

The Fibre Resolved OpticAl and Near-Ultraviolet Czerny–Turner Imaging Spectropolarimeter (francis)

The solar physics community is entering a golden era that is ripe with next-generation ground- and space-based facilities, advanced spectral inversion techniques, and realistic simulations that are becoming more computationally streamlined and efficient. With ever-increasing resolving power stemming from the newest observational telescopes, it becomes more challenging to obtain (near-)simultaneous measurements at high spatial, temporal and spectral resolutions, while operating at the diffraction limit of these new facilities. Hence, in recent years there has been increased interest in the capabilities integral field units (IFUs) offer towards obtaining the trifecta of high spatial, temporal and spectral resolutions contemporaneously. To date, IFUs developed for solar physics research have focused on mid-optical and infrared measurements. Here, we present an IFU prototype that has been designed for operation within the near-ultraviolet to mid-optical wavelength range, which enables key spectral lines (e.g., Ca ii H/K, Hβ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$\\beta $\\end{document}, Sr ii, Na i D1/D2, etc.) to be studied, hence providing additional spectral coverage to the instrument suites developed to date. The IFU was constructed as a low-budget proof-of-concept for the upcoming 2 m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$2\ ext{ m}$\\end{document} class Indian National Large Solar Telescope and employs circular cross-section fibres to guide light into a Czerny–Turner configuration spectrograph, with the resulting spectra captured using a high quantum efficiency scientific CMOS camera. Mapping of each input fibre allows for the reconstruction of two-dimensional spectral images, with frame rates exceeding 20 s−1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$20\ ext{ s}^{-1}$\\end{document} possible while operating in a non-polarimetric configuration. Initial commissioning of the instrument was performed at the Dunn Solar Telescope, USA, during August 2022. The science verification data presented here highlights the suitability of fibre-fed IFUs operating at near-ultraviolet wavelengths for solar physics research. Importantly, the successful demonstration of this type of instrument paves the way for further technological developments to make a future variant suitable for upcoming ground-based and space-borne telescope facilities.

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash

The Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7–8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca ii 397 nm (H line), Fe i 630 nm, and Ca ii 854 nm, scanning the region with a spatial sampling of 0.″041 and an average temporal cadence of 7.76 s, for a duration of 38.8 minutes. The slit moved southward across the plane of sky at 3.83 km s−1. The spectropolarimetric scans exhibit prominent oscillatory “ridge” structures that lie nearly perpendicular to the direction of slit motion (north to south). These ridges are visible in the maps of line intensity, central wavelength, line width, and both linear and circular polarization. Contemporaneous Atmospheric Imaging Assembly observations indicate that these ridges are purely temporal in character and are likely attributed to the familiar chromospheric 3 minute umbral oscillations. We observe in detail a steady umbral flash near the center of the sunspot umbra. Although bad seeing limited the spatial resolution, the unique high signal-to-noise ratio data enable us to estimate the shock Mach numbers (≈2), propagation speeds (≈9 km s−1), and their impacts on the longitudinal magnetic field (ΔB ≈ 50 G), gas pressure, and temperature (ΔT/T ≈ 0.1) of subshocks over 30 s. We also find evidence for rarefaction waves situated between neighboring wave train shocks. The Ca ii 854 nm line width is fairly steady throughout the umbral flash, except for a sharp 1.5 km s−1 dip immediately before, and a comparable spike immediately after, the passage of the shock front. This zigzag in line width is centered on the subshock and extends over 0.″4.

Searching for high-z DSFGs with NIKA2 and NOEMA

As the possible progenitors of passive galaxies at z=2-3, dusty starforming galaxies (DSFGs) at z>4 provide a unique perspective to study the formation, assembly, and early quenching of massive galaxies in the early Universe. The extreme obscuration in optical-IR makes (sub)mm spectral scans the most universal and unbiased way to confirm/exclude the high-z nature of candidate dusty star-forming galaxies. We present here the status of the NIKA2 Cosmological Legacy Survey (N2CLS), which is the deepest wide-area singledish survey in the millimeter searching for high-z DSFGs. We also introduce a joint-analysis method to effciently search for the spectroscopic redshift of high-z DSFGs with noisy spectra and photometric data and present its success in identifying the redshift of DSFGs found in NIKA2 science verification data.

Cross-checking SMBH mass estimates in NGC 6958 – I. Stellar dynamics from adaptive optics-assisted MUSE observations

ABSTRACT Supermassive black hole masses (MBH) can dynamically be estimated with various methods and using different kinematic tracers. Different methods have only been cross-checked for a small number of galaxies and often show discrepancies. To understand these discrepancies, detailed cross-comparisons of additional galaxies are needed. We present the first part of our cross-comparison between stellar- and gas-based MBH estimates in the nearby fast-rotating early-type galaxy NGC 6958. The measurements presented here are based on ground-layer adaptive optics-assisted Multi-Unit Spectroscopic Explorer (MUSE) science verification data at around 0${_{.}^{\prime\prime}}$6 spatial resolution. The spatial resolution is a key ingredient for the measurement and we provide a Gaussian parametrization of the adaptive optics-assisted point spread function for various wavelengths. From the MUSE data, we extracted the stellar kinematics and constructed dynamical models. Using an axisymmetric Schwarzschild technique, we measured an MBH of $(3.6^{+2.7}_{-2.4}) \times 10^8\,$M⊙ at 3σ significance taking kinematical and dynamical systematics (e.g. radially varying mass-to-light ratio) into account. We also added a dark halo, but our data do not allow us to constrain the dark matter fraction. Adding dark matter with an abundance matching prior results in a 25 per cent more massive black hole. Jeans anisotropic models return MBH of $(4.6^{+2.5}_{-2.7}) \times 10^8$ and $(8.6^{+0.8}_{-0.8}) \times 10^8\, \mathrm{M}_{\odot }$ at 3σ confidence for spherical and cylindrical alignments of the velocity ellipsoid, respectively. In a follow-up study, we will compare the stellar-based MBH with those from cold and warm gas tracers, which will provide additional constraints for the MBH for NGC 6958, and insights into assumptions that lead to potential systematic uncertainty.

Mapping dark matter on the celestial sphere with weak gravitational lensing

ABSTRACT Convergence maps of the integrated matter distribution are a key science result from weak gravitational lensing surveys. To date, recovering convergence maps has been performed using a planar approximation of the celestial sphere. However, with the increasing area of sky covered by dark energy experiments, such as Euclid, the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST), and the Nancy Grace Roman Space Telescope, this assumption will no longer be valid. We recover convergence fields on the celestial sphere using an extension of the Kaiser–Squires estimator to the spherical setting. Through simulations, we study the error introduced by planar approximations. Moreover, we examine how best to recover convergence maps in the planar setting, considering a variety of different projections and defining the local rotations that are required when projecting spin fields such as cosmic shear. For the sky coverages typical of future surveys, errors introduced by projection effects can be of the order of tens of percent, exceeding 50 per cent in some cases. The stereographic projection, which is conformal and so preserves local angles, is the most effective planar projection. In any case, these errors can be avoided entirely by recovering convergence fields directly on the celestial sphere. We apply the spherical Kaiser–Squires mass-mapping method presented to the public Dark Energy Survey science verification data to recover convergence maps directly on the celestial sphere.

Likelihood-free inference with neural compression of DES SV weak lensing map statistics

ABSTRACT In many cosmological inference problems, the likelihood (the probability of the observed data as a function of the unknown parameters) is unknown or intractable. This necessitates approximations and assumptions, which can lead to incorrect inference of cosmological parameters, including the nature of dark matter and dark energy, or create artificial model tensions. Likelihood-free inference covers a novel family of methods to rigorously estimate posterior distributions of parameters using forward modelling of mock data. We present likelihood-free cosmological parameter inference using weak lensing maps from the Dark Energy Survey (DES) Science Verification data, using neural data compression of weak lensing map summary statistics. We explore combinations of the power spectra, peak counts, and neural compressed summaries of the lensing mass map using deep convolution neural networks. We demonstrate methods to validate the inference process, for both the data modelling and the probability density estimation steps. Likelihood-free inference provides a robust and scalable alternative for rigorous large-scale cosmological inference with galaxy survey data (for DES, Euclid, and LSST). We have made our simulated lensing maps publicly available.

Evidence for Dense Gas Heated by the Explosion in Orion KL

Abstract We mapped the kinetic temperature structure of Orion KL in a ∼20″ (∼8000 au) sized region with para-H2CS 707 − 606, 726 − 625, and 725 − 624 making use of Atacama Large Millimeter/submillimeter Array Band 6 Science Verification data. The kinetic temperatures obtained with a resolution of 1.″65 × 1.″14 (∼550 au) are deduced by modeling the measured averaged velocity-integrated intensity ratios of para-H2CS 726 − 625/707 − 606 and 725 − 624/707 − 606 with a RADEX non-LTE model. The kinetic temperatures of the dense gas, derived from the para-H2CS line ratios at a spatial density of 107 cm−3, are high, ranging from 43 to >500 K with an unweighted average of ∼170 K. There is no evidence for internal sources playing an important role in the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump, and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecular filaments traced by H2CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive event which occurred several hundred years ago and greatly affected the energetics of the Orion KL region. Thus, with the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL are probably caused by shocks from the explosive event, leading to a dominant component of externally heated dense gas.

Discovery of a Supercluster Candidate at z ∼ 1.1

Abstract We report a promising candidate for a distant supercluster at z ∼ 1.1 in the Dark Energy Survey Science Verification data. We examine smoothed semi-3D galaxy density maps in various photo-z slices. Among several overdense regions, in this work we report the most significant one as having a 3σ overdensity at a redshift of ∼1.1, over a ∼160 Mpc scale, much larger than the regular cluster scale (several Mpc). The shape of the supercluster is not circular in the sky projection. Therefore, we regard the point of maximum overdensity as the center for quantitative measurements. Two different estimates suggest the mass of the supercluster to be , more than one order more massive than regular galaxy clusters. Except for protosuperclusters found with emission-line galaxies, this could be the most distant supercluster to date defined by regular galaxies. A spectroscopic confirmation would make this a very interesting object for cosmology. We discuss the possible implications of such a massive structure for ΛCDM cosmology.

Detection of hydroxyacetone in protostar IRAS 16293-2422 B

Hydroxyacetone (CH3COCH2OH) is one of the smallest molecules that contain both hydroxyl and carbonyl group on neighboring carbon atoms. This steric configuration is characteristic of saccharides and determines their biochemical activity. The attempt to search for hydroxyacetone toward the massive star formation region Sagittarius B2(N) was unsuccessful. Here we report the first detection of CH3COCH2OH in the solar-type protostar IRAS 16293–2422 B, using the Atacama Large Millimeter Array science verification data at Band 4. In a total of 11 unblended transitions of CH3COCH2OH with upper level energies ranging from 86 to 246 K are identified. From our local thermodynamic equilibrium analysis, we derived that the rotational temperature of CH3COCH2OH is 160±21 K and the column density is (1.2±1.0) ×1016 cm−2, which results in a fractional abundance of 7×10−10 with respect to molecular hydrogen. In this work, we present the identification of CH3COCH2OH in IRAS 16293–2422 B and propose a simple formation mechanism. The unambiguous identification of hydroxyacetone may provide the basis for future study of the origin and evolution of saccharides in the interstellar medium.

Centre-to-Limb Brightness Variations from the Atacama Large Millimeter-Submillimeter Array (ALMA) Full-Disk Solar Images

Science Verification (SV) data of solar observations with the Atacama Large Millimeter-submillimeter Array (ALMA) telescope have been released to the scientific community. Understanding the centre-to-limb brightness function is necessary to compare features in full-disk images. Our goals are to find the empirical centre-to-limb brightness functions in two available spectral bands and create flattened images with centre-to-limb brightness variations removed. We used a second-order polynomial fit of the cosine of incidence angle to data points as a function of radial distance to the centre of the solar disk. The method also includes iterative removal of outliers based on the inter-quartile range. Fitting functions for all available images proved to describe the data adequately with comparatively small errors in the fitting coefficients. In both bands we found brightening towards the limb, which is a consequence of the increase in electron temperature with radial distance in this region of the solar atmosphere. This study found that the brightness temperature $[T_{\mathrm{b}}]$ of an active region has about 180 K difference between estimates with and without the limb brightening at radial distance ${\approx}\,0.75~\mbox{R}_{\odot }$ in Band 6. We also made flattened images with limb brightening removed. The limb-brightening effect in ALMA images is significant enough (of the order of 10% for Band 3 and about 15% in Band 6) that it cannot be neglected in further analyses. Since the effect of the side lobes was not included in this study, these values probably represent the lower limit of the limb brightening. The shape of the limb-brightening function can also be used to constrain electron densities and temperatures in various layers of the solar atmosphere.

Hierarchical Modeling and Statistical Calibration for Photometric Redshifts

Abstract The cosmological exploitation of modern photometric galaxy surveys requires both accurate (unbiased) and precise (narrow) redshift probability distributions derived from broadband photometry. Existing methodologies do not meet these requirements. Standard template fitting delivers interpretable models and errors, but lacks the flexibility to learn inaccuracies in the observed photometry or spectral templates. Machine learning addresses those issues, but requires representative training data, and the resulting models and uncertainties cannot be interpreted in the context of a physical model or outside of the training data. We present a hierarchical modeling approach simultaneously addressing the issues of flexibility, interpretability, and generalization. It combines template fitting with flexible (machine-learning-like) models to correct the spectral templates, model their redshift distributions, and recalibrate the photometric observations. By optimizing the full posterior distribution of the model and solving for its (thousands of) parameters, one can perform a global statistical calibration of the data and the spectral energy distribution (SED) model. We apply this approach to the public Dark Energy Survey Science Verification data and show that it provides more accurate and compact redshift posterior distributions than existing methods, as well as insights into residual photometric and SED systematics. The model is causal and makes predictions for future data (e.g., additional photometric bandpasses), and its internal parameters and components are interpretable. This approach does not formally require the training data to be complete or representative; in principle, it can even work in regimes in which few or no spectroscopic redshifts are available.

The Southern Photometric Local Universe Survey (S-PLUS): improved SEDs, morphologies, and redshifts with 12 optical filters

ABSTRACT The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300 deg2 of the celestial sphere in 12 optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k × 9.2k e2v detector with 10 $\rm {\mu m}$ pixels, resulting in a field of view of 2 deg2 with a plate scale of 0.55 arcsec pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30°, 8000 deg2) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/[OII], Ca H + K, H δ, G band, Mg b triplet, H α, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z < 0.4, thus producing a 3D map of the local Universe over a volume of more than $1\, (\mathrm{Gpc}/h)^3$. The final S-PLUS catalogue will also enable the study of star formation and stellar populations in and around the Milky Way and nearby galaxies, as well as searches for quasars, variable sources, and low-metallicity stars. In this paper we introduce the main characteristics of the survey, illustrated with science verification data highlighting the unique capabilities of S-PLUS. We also present the first public data release of ∼336 deg2 of the Stripe 82 area, in 12 bands, to a limiting magnitude of r = 21, available at datalab.noao.edu/splus.

Constraining nuclear star cluster formation using MUSE-AO observations of the early-type galaxy FCC 47

Context. Nuclear star clusters (NSCs) are found in at least 70% of all galaxies, but their formation path is still unclear. In the most common scenarios, NSCs form in-situ from the galaxy’s central gas reservoir, through the merging of globular clusters (GCs), or through a combination of both.Aims. As the scenarios pose different expectations for angular momentum and stellar population properties of the NSC in comparison to the host galaxy and the GC system, it is necessary to characterise the stellar light, NSC, and GCs simultaneously. The large NSC (reff = 66 pc) and rich GC system of the early-type Fornax cluster galaxy FCC 47 (NGC 1336) render this galaxy an ideal laboratory to constrain NSC formation.Methods. Using Multi Unit Spectroscopic Explorer science verification data assisted by adaptive optics, we obtained maps for the stellar kinematics and stellar-population properties of FCC 47. We extracted the spectra of the central NSC and determined line-of-sight velocities of 24 GCs and metallicities of five.Results. The galaxy shows the following kinematically decoupled components (KDCs): a disk and a NSC. Our orbit-based dynamical Schwarzschild model revealed that the NSC is a distinct kinematic feature and it constitutes the peak of metallicity and old ages in FCC 47. The main body consists of two counter-rotating populations and is dominated by a more metal-poor population. The GC system is bimodal with a dominant metal-poor population and the total GC system mass is ∼17% of the NSC mass (∼7 × 108 M⊙).Conclusions. The rotation, high metallicity, and high mass of the NSC cannot be explained by GC-inspiral alone. It most likely requires additional, quickly quenched, in-situ formation. The presence of two KDCs likely are evidence of a major merger that has significantly altered the structure of FCC 47, indicating the important role of galaxy mergers in forming the complex kinematics in the galaxy-NSC system.

Galaxies in X-ray selected clusters and groups in Dark Energy Survey data – II. Hierarchical Bayesian modelling of the red-sequence galaxy luminosity function

Abstract Using ∼100 X-ray selected clusters in the Dark Energy Survey Science Verification data, we constrain the luminosity function (LF) of cluster red-sequence galaxies as a function of redshift. This is the first homogeneous optical/X-ray sample large enough to constrain the evolution of the LF simultaneously in redshift (0.1 < z < 1.05) and cluster mass ($13.5 \le \rm {log_{10}}(M_{200crit}) \sim \lt 15.0$). We pay particular attention to completeness issues and the detection limit of the galaxy sample. We then apply a hierarchical Bayesian model to fit the cluster galaxy LFs via a Schechter function, including its characteristic break (m*) to a faint end power-law slope (α). Our method enables us to avoid known issues in similar analyses based on stacking or binning the clusters. We find weak and statistically insignificant (∼1.9σ) evolution in the faint end slope α versus redshift. We also find no dependence in α or m* with the X-ray inferred cluster masses. However, the amplitude of the LF as a function of cluster mass is constrained to ${\sim } 20{{\ \rm per\ cent}}$ precision. As a by-product of our algorithm, we utilize the correlation between the LF and cluster mass to provide an improved estimate of the individual cluster masses as well as the scatter in true mass given the X-ray inferred masses. This technique can be applied to a larger sample of X-ray or optically selected clusters from the Dark Energy Survey, significantly improving the sensitivity of the analysis.

Single metal-poor ultra compact dwarf galaxy at one kiloparsec distance from the low-mass elliptical galaxy FCC 47

Context. Photometric surveys of galaxy clusters have revealed a large number of ultra compact dwarfs (UCDs) around predominantly massive elliptical galaxies. Their origin is still debated as some UCDs are considered to be the remnant nuclei of stripped dwarf galaxies while others seem to mark the high-mass end of the star cluster population.Aims. We aim to characterize the properties of a UCD found at very close projected distance (rwproj= 1.1 kpc) from the centre of the low-mass (M ∼ 1010 M⊙) early-type galaxy FCC 47. This is a serendipitous discovery from MUSE adaptive optics science verification data. We explore the potential origin of this UCD as either a massive cluster or the remnant nucleus of a dissolved galaxy.Methods. We used archivalHubbleSpace Telescope data to study the photometric and structural properties of FCC 47-UCD1. In the MUSE data, the UCD is unresolved, but we used its spectrum to determine the radial velocity and metallicity.Results. The surface brightness of FCC 47-UCD1 is best described by a single King profile with low concentrationC = Rt/Rc ∼ 10 and large effective radius (reff = 24 pc). Its integrated magnitude and blue colour (Mg = −10.55 mag, (g − z) = 1.46 mag) combined with a metallicity of [M/H] = −1.12 ± 0.10 dex and an age > 8 Gyr obtained from the full fitting of the MUSE spectrum suggests a stellar population mass ofM* = 4.87 × 106 M⊙. The low S/N of the MUSE spectrum prevents detailed stellar population analysis. Due to the limited spectral resolution of MUSE, we can only give an upper limit on the velocity dispersion (σ < 17 km s−1), and consequently on its dynamical mass (Mdyn < 1.3 × 107 M⊙).Conclusions. The origin of the UCD cannot be constrained with certainty. The low metallicity, old age, and magnitude are consistent with a star cluster origin, whereas the extended size is consistent with an origin as the stripped nucleus of a dwarf galaxy with a initial stellar mass of a few 108 M⊙.

First Spectral Analysis of a Solar Plasma Eruption Using ALMA

Abstract The aim of this study is to demonstrate how the logarithmic millimeter continuum gradient observed using the Atacama Large Millimeter/submillimeter Array (ALMA) may be used to estimate optical thickness in the solar atmosphere. We discuss how using multiwavelength millimeter measurements can refine plasma analysis through knowledge of the absorption mechanisms. Here we use subband observations from the publicly available science verification (SV) data, while our methodology will also be applicable to regular ALMA data. The spectral resolving capacity of ALMA SV data is tested using the enhancement coincident with an X-ray bright point and from a plasmoid ejection event near active region NOAA12470 observed in Band 3 (84–116 GHz) on 2015 December 17. We compute the interferometric brightness temperature light curve for both features at each of the four constituent subbands to find the logarithmic millimeter spectrum. We compared the observed logarithmic spectral gradient with the derived relationship with optical thickness for an isothermal plasma to estimate the structures’ optical thicknesses. We conclude, within 90% confidence, that the stationary enhancement has an optical thickness between 0.02 ≤ τ ≤ 2.78, and that the moving enhancement has 0.11 ≤ τ ≤ 2.78, thus both lie near to the transition between optically thin and thick plasma at 100 GHz. From these estimates, isothermal plasmas with typical Band 3 background brightness temperatures would be expected to have electron temperatures of ∼7370–15300 K for the stationary enhancement and between ∼7440 and 9560 K for the moving enhancement, thus demonstrating the benefit of subband ALMA spectral analysis.

J-PLUS: A wide-field multi-band study of the M 15 globular cluster

Context. As a consequence of internal and external dynamical processes, Galactic globular clusters (GCs) have properties that vary radially. Wide-field observations covering the entire projected area of GCs out to their tidal radii (rtidal) can therefore give crucial information on these important relics of the Milky Way formation era. Aims. The Javalambre Photometric Local Universe Survey (J-PLUS) provides wide field-of-view (2 deg2) images in 12 narrow, intermediate and broad-band filters optimized for stellar photometry. Here we have applied J-PLUS data for the first time for the study of Galactic GCs using science verification data obtained for the very metal-poor ([Fe/H] ≈−2.3) GC M 15 located at ~10 kpc from the Sun. Previous studies based on spectroscopy found evidence of multiple stellar populations (MPs) through their different abundances of C, N, O, and Na. Our J-PLUS data provide low-resolution spectral energy distributions covering the near-UV to the near-IR, allowing us to instead search for MPs based on pseudo-spectral fitting diagnostics. Methods. We have built and discussed the stellar radial density profile (RDP) and surface brightness profiles (SBPs) reaching up to rtidal. Since J-PLUS FoV is larger than M 15’s rtidal, the field contamination can be properly taken into account. We also demonstrated the power of J-PLUS unique filter system by showing colour-magnitude diagrams (CMDs) using different filter combinations and for different cluster regions. Results. J-PLUS photometric quality and depth are good enough to reach the upper end of M 15’s main-sequence. CMDs based on the colours (u − z) and (J0378 − J0861) are found to be particularly useful to search for splits in the sequences formed by the upper red giant branch (RGB) and asymptotic giant branch (AGB) stars. We interpret these split sequences as evidence for the presence of MPs. Furthermore, we show that the (u − z) × (J0378 − g) colour–colour diagram allows us to distinguish clearly between field and M 15 stars, which is important to minimize the sample contamination. Conclusions. The J-PLUS filter combinations (u − z) and (J0378 − J0861), which are sensitive to metal abundances, are able to distinguish different sequences in the upper RGB and AGB regions of the CMD of M 15, showing the feasibility of identifying MPs without the need of spectroscopy. This demonstrates that the J-PLUS survey will have sufficient spatial coverage and spectral resolution to perform a large statistical study of GCs through multi-band photometry in the coming years.

An imaging spectroscopic survey of the planetary nebula NGC 7009 with MUSE

Aims. The spatial structure of the emission lines and continuum over the 50″ extent of the nearby, O-rich, PN NGC 7009 (Saturn Nebula) have been observed with the MUSE integral field spectrograph on the ESO Very Large Telescope. This study concentrates on maps of line emission and their interpretation in terms of physical conditions. Methods. MUSE Science Verification data, in <0.6″ seeing, have been reduced and analysed as maps of emission lines and continuum over the wavelength range 4750–9350 Å. The dust extinction, the electron densities and temperatures of various phases of the ionized gas, abundances of species from low to high ionization and some total abundances are determined using standard techniques. Results. Emission line maps over the bright shells are presented, from neutral to the highest ionization available (He II and [Mn V]). For collisionally excited lines (CELs), maps of electron temperature (Te from [N II] and [S III]) and density (Ne from [S II] and [Cl III]) are available and for optical recombination lines (ORLs) temperature (from the Paschen jump and ratio of He I lines) and density (from high Paschen lines). These estimates are compared: for the first time, maps of the differences in CEL and ORL Te’s have been derived, and correspondingly a map of t2 between a CEL and ORL temperature, showing considerable detail. Total abundances of only He and O were formed, the latter using three ionization correction factors. However, the map of He/H is not flat, departing by ~2% from a constant value, with remnants corresponding to ionization structures. An integrated spectrum over an area of 2340 arcsec2 was also formed and compared to 1D photoionization models. Conclusions. The spatial variation of a range of nebular parameters illustrates the complexity of the ionized media in NGC 7009. These MUSE data are very rich with detections of hundreds of lines over areas of hundreds of arcsec2 and follow-on studies are outlined.

Chemical segregation of complex organic O-bearing species in Orion KL.

We investigate the chemical segregation of complex O-bearing species (including the largest and most complex ones detected to date in space) towards Orion KL, the closest high-mass star-forming region. The molecular line images obtained using the ALMA science verification data reveal a clear segregation of chemically related species depending on their different functional groups. We map the emission of 13CH3OH, HCOOCH3, CH3OCH3, CH2OCH2, CH3COOCH3, HCOOCH2CH3, CH3CH2OCH3, HCOOH, OHCH2CH2OH, CH3COOH, CH3CH2OH, CH3OCH2OH, OHCH2CHO, and CH3COCH3 with ~1.5″ angular resolution and provide molecular abundances of these species toward different gas components of this region. We disentangle the emission of these species in the different Orion components by carefully selecting lines free of blending and opacity effects. Possible effects in the molecular spatial distribution due to residual blendings and different excitation conditions are also addressed. We find that while species containing the C-O-C group, i.e. an ether group, exhibit their peak emission and higher abundance towards the compact ridge, the hot core south is the component where species containing a hydroxyl group (-OH) bound to a carbon atom (C-O-H) present their emission peak and higher abundance. This finding allows us to propose methoxy (CH3O-) and hydroxymethyl (-CH2OH) radicals as the major drivers of the chemistry in the compact ridge and the hot core south, respectively, as well as different evolutionary stages and prevailing physical processes in the different Orion components.