Atomic Lines Research Articles

The EDIBLES Survey

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 Å 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.

Zero energy bound states on nano atomic line defect in iron-based high temperature superconductors

Motivated by recent scanning tunneling microscopy experiments on Fe atomic line defect in iron-based high temperature superconductors, we explore the origin of the zero energy bound states near the endpoints of the line defect by employing the two-orbit four-band tight binding model. With increasing the strength of the Rashba spin–orbit coupling along the line defect, the zero energy resonance peaks move simultaneously forward to negative energy for s+− pairing symmetry, but split for s++ pairing symmetry. The superconducting order parameter correction due to As(Te, Se) atoms missing does not shift the zero energy resonance peaks. Such the zero energy bound states are induced by the weak magnetic order rather than the strong Rashba spin–orbit coupling on Fe atomic line defect.

A search for transient, monochromatic light in a 6-deg swath along the galactic plane

ABSTRACT We searched the Milky Way Plane along a 6-deg swath for pulses of monochromatic light as faint as 15th mag (V band) using a wide-field telescope equipped with a prism. Pulses with duration less than 1 s that occur more often than once every 10 min would be detected, and pulses arriving less frequently would be detected with proportionally lower probability. A ‘difference-image’ algorithm revealed 36 monochromatic sources. Subsequent assessment showed all were simply astrophysical objects emitting known atomic emission lines. No unexplainable monochromatic emission, pulsed or continuous, was detected. The detection threshold corresponds to an ∼70 GW laser having a diffraction-limited 10-m aperture 1 kpc away (depending on wavelength). Past all-sky optical and radio-wave surveys revealed thousands of unexpected objects exhibiting extraordinary spectral emission, but none were technological. Hypotheses of our Milky Way Galaxy teeming with advanced life must be demoted.

Observation of parabolic electron bands on superconductor LaRu2As2

Abstract Ru-based superconductor LaRu2As2 has been discovered exhibiting the highest critical temperature of ∼ 7.8 K among iron-free transition metal pnictides with the ThCr2Si2-type crystal structure. However, microscopic research on this novel superconducting material is still lacking. Here, we utilize scanning tunneling microscopy/spectroscopy to uncover the superconductivity and surface structure of LaRu2As2. Two distinct terminating surfaces are identified on the cleaved crystals, namely, the As surface and the La surface. Atomic missing line defects are observed on the La surface. Both surfaces exhibit a superconducting gap of ∼ 1.0 meV. By employing quasiparticle interference techniques, we observe standing wave patterns near the line defects on the La atomic plane. These patterns are attributed to quasiparticle scattering from two electron type parabolic bands.

Variations in Line Profiles of Atomic Transitions in RR Lyrae Stars

We have investigated the absorption shapes of atomic lines and Hα in RR Lyrae stars. We used the database of high-resolution spectra gathered with the Las Campanas Observatory du Pont Telescope, analyzing a set of about 2700 short exposure spectra of 17 RRab and 5 RRc variables. To increase the signal-to-noise ratio of the spectra for each star, we first coadded spectra in small photometric phase bins, and then coadded metallic line profiles in velocity space. The resulting line absorption shapes vary with photometric phase in a consistent manner for all RRab stars, while exhibiting no obvious phase-related variations for the RRc stars. We interpret these line profile variations in terms of velocity gradients in the photospheric layers that produce absorption line profiles. The Hα profiles are much broader, indicative of shock temperatures of order 100,000 K.

Emission Spectra of Uranium Particulates at High Temperature.

The emission spectrum of micron-scale uranium particulates at high temperatures in the ultraviolet, visible, and near-infrared spectral regions is investigated using a heterogeneous shock tube. Temperatures from 3000 to 9000 K are characterized in an inert argon environment and with incremental amounts of added oxygen. Atomic line spectra do not emerge above the continuum emission spectrum until between 4500 and 5000 K in pure argon, and 6100 and 6600 K in 1% oxygen. For 5% oxygen, however, the threshold for atomic emission drops below 3800 K. Uranium monoxide molecular emission in the strongest visible band at 595.4 nm is not observed at any condition. Uncertainties in particle temperature determination in high-temperature shock tube environments are discussed, and limitations to such measurements are presented, such as those from experimental factors such as the powder loading method and expected detection limits of uranium species in relevant conditions.

Brillouin spectroscopy via an atomic line monochromator.

Brillouin spectrometers, used for characterizing material mechanical properties, traditionally employ etalons such as Fabry-Pérot interferometers and virtually imaged phased arrays (VIPA) that use spatial dispersion of the spectrum for measurement. Here, we introduce what we believe to be a novel approach to Brillouin spectroscopy using hot atomic vapors. Using laser induced circular dichroism of the rubidium D2 line in a ladder-type configuration, we developed a narrow-band monochromator for Brillouin analysis. Unlike etalon-based spectrometers, atomic line monochromators operate in free-space, facilitating Brillouin spectroscopy integration with microscopy instruments. We report the transmission and spectral resolution performances of the spectrometer and demonstrate Brillouin spectra measurements in liquids.

PDRs4All

Context. The James Webb Space Telescope (JWST) has captured the most detailed and sharpest infrared (IR) 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). Aims. We investigate the fundamental interaction of far-ultraviolet (FUV) 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. Methods. We utilized NIRCam and MIRI to obtain sub-arcsecond images over ~150″ and 42″ in key gas phase lines (e.g., Pa α, Br α, [FeII] 1.64 µm, H2 1−0 S(1) 2.12 µm, 0–0 S(9) 4.69 µm), aromatic and aliphatic infrared bands (aromatic infrared bands at 3.3–3.4 µm, 7.7, and 11.3 µm), dust emission, and scattered light. Their emission are powerful tracers of the IF and DF, FUV radiation field and density distribution. Using NIRSpec observations the fractional contributions of lines, AIBs, and continuum emission to our NIRCam images were estimated. A very good agreement is found for the distribution and intensity of lines and AIBs between the NIRCam and NIRSpec observations. Results. 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. The spatial distribution of the AIBs reveals that the PDR edge is steep and is followed by an extensive warm atomic layer up to the DF with multiple ridges. A complex, structured, and folded H0/H2 DF surface was traced by the H2 lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar as our observations show that a 3D “terraced” geometry is required to explain the JWST observations. 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. Conclusions. This study offers an unprecedented dataset to benchmark and transform PDR physico-chemical and dynamical models for the JWST era. A fundamental step forward in our understanding of the interaction of FUV photons with molecular clouds and the role of FUV irradiation along the star formation sequence is provided.

Conversion Factors for Physical Property Measurements in different Rest Frames Using a Revised Version of Relativity Theory Based on the Uniform Scaling Method

The history of the development of the Uniform Scaling Method is reviewed. It has its beginning with the Law of Causality and Newton’s First Law of Kinetics (Law of Inertia). On this basis it can be concluded that the rates of clocks do not change spontaneously, i.e. without the application of some external force. Since the ratio Q of the rates of any two such (inertial) clocks must therefore itself be a constant, it follows that whenever they are used to measure a specific time difference between two events, their respective results must always be in the same ratio: Δt’=Δt/Q. This relationship is referred to as Newtonian Simultaneity since it guarantees that if one of the clocks finds that the events occurred simultaneously (Δt’=0), the other must do so as well (Δt=0). A useful way to interpret Q is as a conversion factor between the different units of time employed in the two rest frames. If we assume that the value of the speed of light is the same in both rest frames, it follows that they must agree on the unit of speed, i.e. the conversion factor in this case is unity (Q0 ). It therefore follows that the conversion factor for the unit of distance must be exactly the same as that for time, namely also Q. This claim of the Uniform Scaling Method is thus seen to be in direct contradiction to the length contraction tenet of Einstein’s theory of relativity introduced in 1905. Experiments with accelerated electrons carried out by Bucherer in 1909 indicate that their inertial mass increase in direct proportion to γ (v) = (1-v2 c-2)-0.5 (v is the speed of the electrons and c = 299792458 ms-1 is the speed of light in free space), the same ratio as observed for the periods of atomic lines by Ives and Stilwell in 1938. Consistency therefore requires that the conversion factor for inertial mass is the same (Q) as for time. Since inertial mass, time and distance are the three fundamental quantities on which all other physical properties are defined (mks system), it follows that the conversion factor for any other property must be an integral multiple of Q. An analogous set of definitions can also be justified for the corresponding conversion factors in the same two rest frames caused by gravitational effects. In this case the conversion factors are always integral multiples of the quantity S, which therefore plays as analogous role as Q in kinetic scaling. Since experiments with circumnavigating atomic clocks carried out in 1971 by Hafele and Keating found that the two types of effects are completely independent of one another, it is therefore useful to define a product Z of the corresponding Q and S factors for each physical property, including those that are used to define the results of electromagnetic measurements. These total conversion factors are stored in Tables 1 and 2 of the manuscript. They are shown to guarantee that if a physical law is valid in one of the rest frames, it will also hold in the other. This relationship allows for an Addendum to Galileo’s Relativity Principle: The laws of physics are the same in all inertial rest frames, but the units in which their results are expressed can differ from one rest frame to another.

Method for the production of a compact source of atomic line spectra in the vacuum ultraviolet

Atomic emission spectra provide a means to identify and to gain insight into the electronic structure of emitting or absorbing matter. Detailed procedures are provided for the construction of low-pressure electrodeless discharge lamps that yield targeted emission in the vacuum ultraviolet for the spectroscopic study of water vapor and halogen species aboard an array of airborne observation platforms in the upper atmosphere, as well as in laboratory environments. While specific to the production of Lyman-alpha, atomic chlorine, and atomic bromine emissions in this study, the configuration of the lamps and their interchangeability with respect to operation lend these procedures to constructing sources engaging a wide selection of atomic and molecular spectra with straightforward modifications. The features and limitations of each type of lamp are discussed, as well as methods to improve spectral purity and factors affecting operational lifetime.

Dried Blood Spots and Miniaturized Ultrasonic Nebulization Microplasma Optical Emission Spectrometry for Point-of-Care Testing of Blood Lithium.

Despite the significant importance of blood lithium (Li) detection in the treatment of bipolar disorder (BD), its point-of-care testing (POCT) remains a great challenge due to tedious sample preparation and the use of large-footprint atomic spectrometers. Herein, a system coupling dried blood spots (DBS) with a point discharge optical emission spectrometer equipped with a miniaturized ultrasonic nebulizer (MUN-μPD-OES) was developed for POCT of blood Li. Three microliters of whole blood were used to prepare a dried blood spot on a piece of filter paper to which 10 μL of eluent (1% (v/v) formic acid and 0.05% (v/v) Triton-X) was added. Subsequently, the paper was placed onto the vibrating steel membrane of the ultrasonic nebulizer and powered on to generate aerosol. The aerosol was directly introduced to the μPD-OES for quantification of Li by monitoring its atomic emission line at 670.8 nm. The proposed method minimized matrix interference caused by high levels of salts and protein. It is worth noting that the MUN suitably matches the needs of DBS sampling and can provide aerosolized introduction of Li into the assembled μPD-OES, thus eliminating all tedious sample preparation and the need for a commercial atomic spectrometer. Calibration response is linear in the therapeutic range and a limit of detection (LOD) of 1.3 μg L-1 is well below the Li minimum therapeutic concentration (2800 μg L-1). Li in mouse blood was successfully detected in real-time using MUN-μPD-OES after intraperitoneal injection of lithium carbonate, confirming that the system holds great potential for POCT of blood Li for patients with BD.

Circumnuclear Multiphase Gas in the Circinus Galaxy. VI. Detectability of Molecular Inflow and Atomic Outflow

Recent submillimeter observations have revealed signs of parsec-scale molecular inflow and atomic outflow in the nearest Seyfert 2 galaxy, the Circinus galaxy. To verify the gas kinematics suggested by these observations, we performed molecular and atomic line transfer calculations based on a physics-based 3D radiation-hydrodynamic model, which has been compared with multiwavelength observations in this paper series. The major-axis position–velocity diagram (PVD) of CO(3–2) reproduces the observed faint emission at the systemic velocity, and our calculations confirm that this component originates from failed winds falling back to the disk plane. The minor-axis PVD of [C i](3 P 1–3 P 0), when created using only the gas with positive radial velocities, presents a sign of blueshifted and redshifted offset peaks similar to those in the observation, suggesting that the observed peaks indeed originate from the outflow, but that the model may lack outflows as strong as those in the Circinus galaxy. Similar to the observed HCN(3–2), the similar dense-gas tracer HCO+(3–2) can exhibit nuclear spectra with inverse P-Cygni profiles with ∼0.5 pc beams, but the line shape is azimuthally dependent. The corresponding continuum absorbers are inflowing clumps at 5–10 pc from the center. To detect significant absorption with a high probability, the inclination must be fairly edge-on (≳85°), and the beam size must be small (≲1 pc). These results suggest that HCN or HCO+ and [C i] lines are effective for observing parsec-scale inflows and outflows, respectively.

One-dimensional temperature measurement of gases based on femtosecond laser-extended electrode discharge spectroscopy (FEEDS)

Temperature, and hence thermometry techniques, are critical for characterizing gaseous flows and flames. Therefore, it is always attractive to develop new thermometry techniques to satisfy different demands. Here, we propose a thermometry technique for one-dimensional gas temperature measurements based on femtosecond laser-extended electrode discharge spectroscopy (FEEDS). By FEEDS measurements in gas flows containing hydrogen, we found that the temperature of the gas flow has a strong correlation with the full width at half maximum (FWHM) of the atomic hydrogen line at 656 nm, and this correlation is monotonic in the temperature range we measured, i.e., the temperature of gas flows can be extracted by measuring this FWHM. We applied this technique to methane/air gas mixtures and realized temperature measurements in the range of 300–1806 K with an error of ∼50 K. Also, we found that the technique has the capability to achieve one-dimensional measurements; more importantly, we found that changes in the stoichiometric ratio of the gas mixture do not affect the temperature measurements. Finally, we applied this technique to a premixed methane/air jet flame.

Atomic line spectra and the conservation laws

By conservation of linear momentum an atom recoils after it de-excites by giving out a photon. The de-excitation energy is shared by the photon and the recoiling atom. There was no mention in textbooks of this recoil energy when discussing atomic line spectra. We illustrate why it is valid to assume that the de-excitation energy is the energy of the emitted photon in line spectra around the visible light region.

Application of helium line intensity ratio spectroscopy to xenon plasma in E × B Penning discharge

We propose the application of helium line intensity ratio spectroscopy in a low-pressure (0.3 mTorr) xenon E × B discharge with an electron temperature of ∼2 eV and a density of 1010−1011cm−3 . We successfully identified the helium atom line emissions at 388.9, 447.1, 501.6, 504.8, and 706.5 nm with helium pressures of up to ∼20 mTorr. The measured electron temperature, density, and I−V characteristics of the discharge remained almost constant in all helium pressures in the present experiment, indicating the suitability of the helium gas as a diagnostic gas. The results of helium line intensity ratio spectroscopy using the line emissions at 388.9, 447.1, and 504.8 nm showed fair agreement with the Langmuir probe measurement. Considering the trade-off relationship between the disturbance introduced by the helium gas and the signal-to-noise ratio, we conclude that a helium pressure of approximately 4 mTorr (approximately 13 times the partial pressure of xenon) represents the optimal pressure range for the application of the helium line emission intensity ratio method to this xenon plasma. It is found that the use of the line emissions at 501.6 and 706.5 nm result in a significant disturbance in the helium line intensity ratio method due to the radiation trapping effect.

Shocks, clouds, and atomic outflows in active galactic nuclei hosting relativistic jets

Context. A number of observations have revealed atomic and/or molecular lines in active galaxies hosting jets and outflows. Line widths indicate outward motions of hundreds to a few thousands of kilometers per second. They appear to be associated with the presence of radio emission in Gigahert-peaked spectrum (GPS) and/or compact steep spectrum (CSS) sources, with linear sizes of ≤10 kpc. Numerical simulations have shown that the bow shocks triggered by relativistic jets in their host galaxies drive ionization and turbulence in the interstellar medium (ISM). However, the presence of atomic lines requires rapid recombination of ionized gas, which appears challenging to explain from the physical conditions revealed thus far based on numerical simulations of powerful jets. Aims. The aim of this paper is to provide a global framework to explain the presence of lines in terms of jet and shock evolution and to fix the parameter space where the atomic and molecular outflows might occur. Methods. This parameter space is inspired by numerical simulations and basic analytical models of jet evolution as a background. Results. Our results show that a plausible general explanation involves momentum transfer and heating to the interstellar medium gas by jet triggered shocks within the inner kiloparsecs. The presence of post-shock atomic gas is possible in the case of shocks interacting with dense clouds that remain relatively stable after the shock passage. Conclusions. According to our results, current numerical simulations cannot reproduce the physical conditions to explain the presence of atomic and molecular outflows in young radio sources. However, I show that these outflows might occur in low-power jets at all scales and I predict a trend towards powerful jets showing lines at CSS scales, when clouds have cooled to recombination temperatures.

Medium-resolution 0.97–5.3 μm Spectra of Very Young Benchmark Brown Dwarfs with NIRSpec on Board the James Webb Space Telescope

Spectra of young benchmark brown dwarfs with well-known ages are vital to characterize other brown dwarfs, for which ages are in general not known. These spectra are also crucial to test atmospheric models, which have the potential to provide detailed information about the atmospheres of these objects. However, to test atmospheric models optimally, medium-resolution, long-wavelength-coverage spectra with well-understood uncertainties are ideal, such as the spectra provided by the NIRSpec instrument on board the James Webb Space Telescope. In this paper, we present medium-resolution JWST/NIRSpec spectra of two young brown dwarfs, TWA 28 (M9.0) and TWA 27A (M9.0), and one planetary-mass object, TWA 27B (L6.0), members of the TW Hydrae Association (age ∼ 10 Myr). We show the richness of the atomic lines and molecular bands present in the spectra. All objects show signs of a circumstellar disk, via a near-infrared excess and/or via emission lines. We matched a set of cloudless atmospheric spectra (ATMO), and cloudy atmospheric spectra (BT-Settl) to our NIRSpec spectra, and analyzed which wavelength ranges and spectral features both models reproduce best. Both models derive consistent parameters for the three sources, and predict the existence of CH4 at 3.35 μm in TWA 27B. Nonetheless, in contrast to other slightly older objects with similar spectral type, like PSO 318.5–22 and VHS 1256b, this feature is not present in the spectrum of TWA 27B. The lack of the CH4 feature might suggest that the L–T transition of very young dwarfs starts at later spectral types than for older brown dwarfs.

The classical T Tauri star CI Tau observed with SPIRou: magnetospheric accretion and planetary formation

ABSTRACT We report new observations of the classical T Tauri star CI Tau with the SPIRou near-infrared spectropolarimeter and velocimeter at the Canada–France–Hawaii Telescope (CFHT) in late 2019, 2020, and 2022, complemented with observations obtained with the ESPaDOnS optical spectropolarimeter at CFHT in late 2020. From our SPIRou and ESPaDOnS spectra, to which we applied least-squares deconvolution, we infer longitudinal fields clearly modulated with the 9-d rotation period of CI Tau. Using Zeeman–Doppler imaging, we reconstruct the large-scale magnetic topology, first from SPIRou data only in all three seasons, then from our 2020 SPIRou and ESPaDOnS data simultaneously. We find that CI Tau hosts a mainly axisymmetric poloidal field, with a 1 kG dipole slightly tilted to the rotation axis and dark spots close to the pole that coincide with the footpoints of accretion funnels linking the star to the inner disc. Our results also suggest that CI Tau accretes mass from the disc in a stable fashion. We further find that radial velocities (RVs) derived from atomic and CO lines in SPIRou spectra are both rotationally modulated, but with a much lower amplitude than that expected from the putative candidate planet CI Tau b. We confirm the presence of a RV signal at a period of 23.86 d reported in a separate analysis, but detect it clearly in CO lines only and not in atomic lines, suggesting that it likely traces a non-axisymmetric structure in the inner disc of CI Tau rather than a massive close-in planet.

Atmospheric pressure plasma jet: Green technology advancements for metals deposition potential

This study explored the utilization of an atmospheric pressure plasma jet (APPJ) for the deposition of metal layers, employing Ar + 2 % H2 as the working gas. The research focuses on three distinct metals - silver (Ag), copper (Cu), and nickel (Ni). Through the application of optical emission spectroscopy, significant peaks of Ar-related and hydrogen-alpha (Hα) species are observed, accompanied by atomic characteristic emission lines specific to Ag, Cu, and Ni, respectively. The XRD examination indicates the successful deposition of metal layers onto the substrates, a confirmation supported by the EDS line scan. Examination of the surface morphology reveals that the metal particles have clustered together, creating a porous structure. The resistivity measurement obtains the values of 5.18, 3.81, and 9.21 μΩ-cm for Ag, Cu, and Ni layers, respectively. Moreover, the paper presents a proposed mechanism for depositing metallic conductive layers using an atmospheric pressure plasma jet (APPJ), elucidating the complex processes inherent in this novel technique.

Satellite Hyperspectral Nighttime Light Observation and Identification with DESIS

The satellite imagery of nighttime lights (NTLs) has been studied to understand human activities, economic development, and more recently, the ecological impact of brighter night skies. The Visible Infrared Imaging Radiometer Suite (VIIRS) Day–Night Band (DNB) offers perhaps the most advanced nighttime imaging capabilities to date, but its large pixel size and single band capture large-scale changes in NTL while missing granular but important details, such as lighting type and brightness. To better understand individual NTL sources in a region, the spectra of nighttime lights captured by the DLR Earth Sensing Imaging Spectrometer (DESIS) were extracted and compared against near-coincident VIIRS DNB imagery. The analysis shows that DESIS’s finer spatial and spectral resolutions can detect individual NTL locations and types beyond what is possible with the DNB. Extracted night light spectra, validated against ground truth measurements, demonstrate DESIS’s ability to accurately detect and identify narrow-band atomic emission lines that characterize the spectra of high-intensity discharge (HID) light sources and the broader spectral features associated with different light-emitting diode (LED) lights. These results suggest the possible application of using hyperspectral data from moderate-resolution sensors to identify lamp construction details, such as illumination source type and light quality in low-light contexts. NTL data from DESIS and other hyperspectral sensors may improve the scientific understanding of light pollution, lighting quality, and energy efficiency by identifying, evaluating, and mapping individual and small groups of light sources.