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Abstract Single‐mode distributed feedback GaSb‐based interband cascade lasers with record emission beyond 6.1 µm are presented. The results are based on an epitaxial design with reduced resonant intersubband absorption in the valence band and rebalanced internally generated carriers. The epi‐down mounted 8 µm wide and 1 mm long laser chip is operated in continuous wave mode at room temperature and covers a bandwidth of over 20 nm with temperature and current tuning. At 25°C more than 4 mW of optical output power was measured.

Creation of controllable narrow-band emission sources for the mid- and longwavelength infrared ranges is one of the primary tasks of infrared technology. In this paper, we propose and demonstrate non-luminescent (thermal) magnetically controllable sources of infrared emission based on semiconductor magneto-optical photonic structures (MOPS). It is shown that interference effects cause narrow-band thermal emission spectrum of such sources, and magnetic field makes it possible to effectively control the spectral and amplitude characteristics of emissivity in the mid- and long-wavelength infrared range. Influence of the MOPS composition and design on the source emissive characteristics is studied. Using the obtained results, the designs of A³B5 semiconductor compounds based sources with dynamically tunable spectrum and amplitude modulation of emission are proposed. Theoretical modeling has shown the possibility of dynamic control of their emission parameters by achievable magnetic fields. Such sources may be used in environmental monitoring systems, medicine, forensics, infrared spectroscopy, etc. [ABSTRACT FROM AUTHOR]

The central regions of the Milky Way constitute a unique laboratory for a wide swath of astrophysical studies; consequently, the inner ∼400 pc have been the target of numerous large surveys at all accessible wavelengths. In this paper, we present a catalog of sources at 25 and 37 μ m located within all of the regions observed with the SOFIA/FORCAST instrument in the inner ∼200 pc of the Galaxy. The majority of the observations were obtained as part of the SOFIA Cycle 7 Galactic Center Legacy program survey, which was designed to complement the Spitzer/MIPS 24 μ m catalog in regions saturated in the MIPS observations. Due to the wide variety of source types captured by our observations at 25 and 37 μ m, we do not limit the FORCAST source catalog to unresolved point sources, or treat all sources as if they are pointlike sources. The catalog includes all detectable sources in the regions, resulting in a catalog of 950 sources, including point sources, compact sources, and extended sources. We also provide the user with metrics to discriminate between the source types.

The launch of Gaia in 2013 December ushered in a new era of space astrometry, allowing for fundamental reference research at an unprecedented level of precision. The international celestial reference frames in the radio band and the Gaia celestial reference frame in the optical band have been established and are consistent within several microarcseconds for axes orientation. To bridge the gap between the visual and radio bands, an infrared reference frame should be investigated. We present a study aimed at constructing an infrared reference frame using the observations from the AllWISE catalog. It is compared with Gaia DR3 for approximately 0.57 million extragalactic sources and for a full set of 273 million sources. Systematic differences in positions and proper motions, such as magnitude or color equations and vector spherical harmonics, are derived. These systematic differences are comparable to the random errors of AllWISE measurements and can be used to improve the AllWISE source positions and proper motions, making the AllWISE catalog a valuable all-sky reference frame in the infrared band. Our investigation of the AllWISE catalog reveals that extragalactic sources and stars exhibit different astrometric properties. The global difference between the extragalactic source reference frame and the stellar reference frames is found to be 8.6 mas and 13.7 mas for global rotation and glide amplitudes, respectively. Such internal inconsistency should be considered when using AllWISE as an infrared reference frame. Finally, we determine the orientation of the mean Galactic plane using the calibrated source distribution of the AllWISE catalog.

We present a comprehensive analysis of the post-outburst evolution of the FU Ori object HBC 722 in optical/near-infrared (NIR) photometry and spectroscopy. Using a modified viscous accretion disk model, we fit the outburst epoch spectral energy distribution to determine the physical parameters of the disk, including ${\dot{M}}_{\mathrm{acc}}={10}^{-4.0}\ {M}_{\odot }$ yr ^−1 , R _inner = 3.65 R _⊙ , i = 79°, and a maximum disk temperature of ${T}_{\max }=5700$ K. We then use a decade of optical/NIR spectra to demonstrate a changing accretion rate drives the visible-range photometric variation, while the NIR shows the outer radius of the active accretion disk expands outward as the outburst progresses. We also identify the major components of the disk system: a plane-parallel disk atmosphere in Keplerian rotation and a two-part warm disk wind that is collimated near the star and wide-angle at larger radii. The wind is traced by classic wind lines, and appears as a narrow, low-velocity, deep absorption component in several atomic lines spanning the visible spectrum and in the CO 2.29 μ m band. We compare the wind lines to those computed from wind models for other FU Ori systems and rapidly accreting young stellar disks and find a 4000–6000 K wind can explain the observed line profiles. Fitting the progenitor spectrum, we find M _* = 0.2 M _⊙ and ${\dot{M}}_{\mathrm{progenitor}}=7.8\times {10}^{-8}\ {M}_{\odot }\ {\mathrm{yr}}^{-1}$ . Finally, we discuss HBC 722 relative to V960 Mon, another FU Ori object we have previously studied in detail.

During our spectroscopic survey of central stars of faint planetary nebulae (PNe), we found that the nucleus of Abell 57 exhibits strong nebular emission lines. Using synthetic narrowband images, we show that the emission arises from an unresolved compact emission knot (CEK) coinciding with the hot (90,000 K) central star. Thus Abell 57 belongs to the rare class of “EGB 6-type” PNe, characterized by dense emission cores. Photometric data show that the nucleus exhibits a near-infrared excess, due to a dusty companion body with the luminosity of an M0 dwarf but a temperature of ∼1800 K. Emission-line analysis reveals that the CEK is remarkably dense (electron density ∼ 1.6 × 10 ^7 cm ^−3 ), and has a radius of only ∼4.5 au. The CEK suffers considerably more reddening than the central star, which itself is more reddened than the surrounding PN. These puzzles may suggest an interaction between the knot and central star; however, Hubble Space Telescope imaging of EGB 6 itself shows that its CEK lies more than ∼125 au from the PN nucleus. We discuss a scenario in which a portion of the asymptotic giant branch wind that created the PN was captured into a dust cloud around a distant stellar companion; this cloud has survived to the present epoch, and has an atmosphere photoionized by radiation from the hot central star. However, in this picture EGB 6-type nuclei should be relatively common, yet they are actually extremely rare; thus they may arise from a different transitory phenomenon. We suggest future observations of Abell 57 that may help unravel its mysteries.

We present our sixth set of results from our mid-infrared imaging survey of Milky Way Giant H ii regions with our detailed analysis of NGC 3603, the most luminous giant H ii (GH ii ) region in the Galaxy. We used imaging data from the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) at 20 and 37 μ m, which mapped the central ∼8.′5 × 8.′5 infrared-emitting area of NGC 3603 at a spatial resolution of ≲3″. Utilizing these SOFIA data in conjunction with multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, we investigate the physical nature of individual infrared sources and subcomponents within NGC 3603. For individual compact sources, we used the multiwavelength photometry data to construct spectral energy distributions (SEDs) and fit them with massive young stellar object (MYSO) SED models, and find 14 sources that are likely to be MYSOs. We also detect dust emission from the 3 massive proplyd candidates, as well as from the disk and outflow of the evolved blue supergiant, Sher 25. Utilizing multiwavelength data, we derived luminosity-to-mass ratio and virial parameters for the star-forming clumps within NGC 3603, estimating their relative ages and finding that NGC 3603 is an older GH ii region overall, compared to our previously studied GH ii regions. We discuss how NGC 3603, which we categorize as a cavity-type GH ii region, exhibits a more modest number of MYSOs and molecular clumps when compared to the distributed-type GH ii regions that share similar Lyman continuum photon rates.

We study the properties of galaxies hosting mid-infrared outbursts in the context of a catalog of 500,000 galaxies from the Sloan Digital Sky Survey. We find that nuclear obscuration, as inferred by the surrounding dust mass, does not correlate with host galaxy type, stellar properties (e.g., total mass and mean age), or with the extinction of the host galaxy as estimated by the Balmer decrement. This implies that nuclear obscuration may not be able to explain any overrepresentation of tidal disruption events in particular host galaxies. We identify a region in the galaxy catalog parameter space that contains all unobscured tidal disruption events but only harbors ≲11% of the mid-infrared outburst hosts. We find that mid-infrared outburst hosts appear more centrally concentrated and have higher galaxy Sérsic indices than galaxies hosting active galactic nuclei (AGNs) selected using the Baldwin–Phillips–Terlevich classification. We thus conclude that the majority of mid-infrared outbursts are not hidden tidal disruption events but are instead consistent with being obscured AGN that are highly variable, such as changing-look AGN.

We present James Webb Space Telescope (JWST) imaging of NGC 7469 with the Near-Infrared Camera and the Mid-InfraRed Instrument. NGC 7469 is a nearby, z = 0.01627, luminous infrared galaxy that hosts both a Seyfert Type-1.5 nucleus and a circumnuclear starburst ring with a radius of ∼0.5 kpc. The new near-infrared (NIR) JWST imaging reveals 66 star-forming regions, 37 of which were not detected by Hubble Space Telescope (HST) observations. Twenty-eight of the 37 sources have very red NIR colors that indicate obscurations up to A _v ∼ 7 and a contribution of at least 25% from hot dust emission to the 4.4 μ m band. Their NIR colors are also consistent with young (

Nanophotonic engineering of light–matter interaction at subwavelength scale allows thermal radiation that is fundamentally different from that of traditional thermal emitters and provides exciting opportunities for various thermal-photonic applications. We propose a new kind of integrated and electrically controlled thermal emitter that exploits layered metamaterials with lithography-free and dielectric/metallic nanolayers. We demonstrate both theoretically and experimentally that the proposed concept can create a strong photonic bandgap in the visible regime and allow small impedance mismatch at the infrared wavelengths, which gives rise to optical features of significantly enhanced emissivity at the broad infrared wavelengths of 1.4–14 μm as well as effectively suppressed emissivity in the visible region. The electrically driven metamaterial devices are optically and thermally stable at temperatures up to ∼800 K with electro-optical conversion efficiency reaching ∼30%. We believe that the proposed high-efficiency thermal emitters will pave the way toward integrated infrared light source platforms for various thermal-photonic applications and particularly provide a novel alternative for cost-effective, compact, low glare, and energy-efficient infrared heating.

The authors demonstrate a high‐speed 8.5‐μm quantum cascade laser (QCL) with room temperature continuous wave (CW) operation. The maximum output power of 141 mW is obtained at 20°C. The parasitic capacitance of the device is decreased from 36.6 to 7.1 pF by monolithic integrating a π‐shape metal contact electrode. This results in an increase in the −3 dB RF modulation bandwidth from 870 MHz to 4.5 GHz compared with the conventional electrode configuration. [ABSTRACT FROM AUTHOR]

We have used the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to obtain the first spatially resolved, mid-infrared images of IIZw096, a merging luminous infrared galaxy (LIRG) at z = 0.036. Previous observations with the Spitzer Space Telescope suggested that the vast majority of the total IR luminosity ( L _IR ) of the system originated from a small region outside of the two merging nuclei. New observations with JWST/MIRI now allow an accurate measurement of the location and luminosity density of the source that is responsible for the bulk of the IR emission. We estimate that 40%–70% of the IR bolometric luminosity, or 3–5 × 10 ^11 L _⊙ , arises from a source no larger than 175 pc in radius, suggesting a luminosity density of at least 3–5 × 10 ^12 L _⊙ kpc ^−2 . In addition, we detect 11 other star-forming sources, five of which were previously unknown. The MIRI F1500W/F560W colors of most of these sources, including the source responsible for the bulk of the far-IR emission, are much redder than the nuclei of local LIRGs. These observations reveal the power of JWST to disentangle the complex regions at the hearts of merging, dusty galaxies.

With its unprecedented sensitivity and spatial resolution, the James Webb Space Telescope (JWST) has opened a new window for time-domain discoveries in the infrared. Here we report observations in the only field that has received four epochs (spanning 126 days) of JWST NIRCam observations in Cycle 1. This field is toward MACS J0416.1−2403, which is a rich galaxy cluster at redshift z = 0.4 and is one of the Hubble Frontier Fields. We have discovered 14 transients from these data. Twelve of these transients happened in three galaxies (with z = 0.94, 1.01, and 2.091) crossing a lensing caustic of the cluster, and these transients are highly magnified by gravitational lensing. These 12 transients are likely of a similar nature to those previously reported based on the Hubble Space Telescope (HST) data in this field, i.e., individual stars in the highly magnified arcs. However, these 12 could not have been found by HST because they were too red and too faint. The other two transients are associated with background galaxies ( z = 2.205 and 0.7093) that are only moderately magnified, and they are likely supernovae. They indicate a demagnified supernova surface density, when monitored at a time cadence of a few months to a ∼3–4 μ m survey limit of AB ∼28.5 mag, of ∼0.5 arcmin ^−2 integrated to z ≈ 2. This survey depth is beyond the capability of HST but can be easily reached by JWST.

We present in this paper mid-infrared (5–8 μ m) spectroscopy toward the massive young binary W3 IRS 5, using the Echelon Cross Echelle Spectrograph (EXES) spectrometer in high-resolution mode ( R ∼ 50,000) from the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA). Many (∼180) ν _2 = 1–0 and (∼90) ν _2 = 2–1 absorption rovibrational transitions are identified. Two hot components over 500 K and one warm component of 190 K are identified through Gaussian fittings and rotation diagram analysis. Each component is linked to a CO component identified in the IRTF/iSHELL observations ( R = 88,100) through their kinematic and temperature characteristics. Revealed by the large scatter in the rotation diagram, opacity effects are important, and we adopt two curve-of-growth analyses, resulting in column densities of ∼10 ^19 cm ^−2 . In one analysis, the model assumes a foreground slab. The other assumes a circumstellar disk with an outward-decreasing temperature in the vertical direction. The disk model is favored because fewer geometry constraints are needed, although this model faces challenges as the internal heating source is unknown. We discuss the chemical abundances along the line of sight based on the CO-to-H _2 O connection. In the hot gas, all oxygen not locked in CO resides in water. In the cold gas, we observe a substantial shortfall of oxygen and suggest that the potential carrier could be organics in solid ice.

We study the evolution of the FU Ori object V960 Mon since its outburst, using available multiwavelength photometric time series over 8 yr, complemented by several epochs of moderate-dispersion spectrophotometry. We find that the source fading can be well-described by a decrease in the temperature of the inner disk, which results from a combination of decreasing accretion rate and increasing inner disk radius. We model the system with a disk atmosphere model that produces the observed variations in multiband photometry (this paper) and high-resolution spectral lines (a companion paper).

Although episodic star formation (SF) has been suggested for nearby SF regions, a panoramic view of the recent episodic SF history in the solar neighborhood is still missing. By uniformly constraining the slope α of infrared spectral energy distributions (SEDs) of young stellar objects (YSOs) in the 13 largest Gould’s Belt (GB) protoclusters surveyed by the Spitzer Space Telescope, we have constructed a cluster-averaged histogram of α representing the YSO evolution lifetime as a function of the α value. Complementary to the traditional SED classification scheme ( 0 , i , f , ii , and iii ) that is based on different α values, a staging scheme (A, B, C, D, and E) of SED evolution is proposed on the basis of the α statistical features that can be better matched to the physical stages of disk dissipation and giant planet formation. This has also allowed us to unravel the fluctuations of SF rate (SFR) in the 3 Myr history of these GB protoclusters. Diverse evolutionary patterns such as single peaks, double peaks, and ongoing acceleration of SFR are revealed. The SFR fluctuations are between 20% and 60% (∼40% on average) and no dependence on the average SFR or the number of SFR episodes is found. However, spatially close protoclusters tend to have similar SFR fluctuation trends, indicating that the driving force of the fluctuations should be at size scales beyond the typical cluster sizes of several parsecs.

We used the Immersion GRating Infrared Spectrometer (IGRINS) to determine fundamental parameters for 61 K- and M-type young stellar objects (YSOs) located in the Ophiuchus and Upper Scorpius star-forming regions. We employed synthetic spectra and a Markov chain Monte Carlo approach to fit specific K -band spectral regions and determine the photospheric temperature ( T ), surface gravity ( $\mathrm{log}g$ ), magnetic field strength ( B ), projected rotational velocity ( $v\sin i$ ), and K -band veiling ( r _K ). We determined B for ∼46% of our sample. Stellar parameters were compared to the results from Taurus-Auriga and the TW Hydrae association presented in Paper I of this series. We classified all the YSOs in the IGRINS survey with infrared spectral indices from Two Micron All Sky Survey and Wide-field Infrared Survey Explorer photometry between 2 and 24 μ m. We found that Class II YSOs typically have lower $\mathrm{log}g$ and $v\sin i$ , similar B , and higher K -band veiling than their Class III counterparts. Additionally, we determined the stellar parameters for a sample of K and M field stars also observed with IGRINS. We have identified intrinsic similarities and differences at different evolutionary stages with our homogeneous determination of stellar parameters in the IGRINS YSO survey. Considering $\mathrm{log}g$ as a proxy for age, we found that the Ophiuchus and Taurus samples have a similar age. We also find that Upper Scorpius and TWA YSOs have similar ages, and are more evolved than Ophiuchus/Taurus YSOs.

We present deep near-infrared (NIR) imaging of Sh 2–209 (S209), a low-metallicity ([O/H] = −0.5 dex) H ii region in the Galaxy. From the NIR images, combined with astrometric data from Gaia EDR3, we estimate the distance to S209 to be 2.5 kpc. This is close enough to enable us to resolve cluster members clearly (≃1000 au separation) down to a mass-detection limit of ≃ 0.1 M _⊙ , and we have identified two star-forming clusters in S209, with individual cluster scales ∼1 pc. We employ a set of model luminosity functions to derive the underlying initial mass functions (IMFs) and ages for both clusters. The IMFs we obtained for both clusters exhibit slightly flat high-mass slopes (Γ ≃ −1.0) compared to the Salpeter IMF (Γ = −1.35), and their break mass of ≃0.1 M _⊙ is lower than those generally seen in the solar neighborhood (∼0.3 M _⊙ ). In particular, because the S209 main cluster is a star-forming cluster with a larger number of members (∼1500) than the number (∼100) in regions previously studied in such environments, it is possible for the first time to derive the IMF in a low-metallicity environment with high accuracy over the wide mass range of 0.1–20 M _⊙ .

Massive young stellar objects (MYSOs) play a crucial role in star formation. Given that MYSOs were previously identified based on the extended structure and the observational data for them is limited, screening the Wide-field Infrared Survey Explorer (WISE) objects showing green features (for the common coding of the 4.6 μ m band as the green channel in three-color composite WISE images) will yield more MYSO candidates. Using WISE images in the whole Galactic plane (0° < l < 360° and ∣ b ∣ < 2°), we identified sources with strong emissions at the 4.6 μ m band, then according to morphological features divided them into three groups. We present a catalog of 2135 WISE Green Objects (WGOs). 264 WGOs have an extended structure. 1366 WGOs show compact green features but without extended structure. 505 WGOs have neither extended structure nor green features, but the intensity at 4.6 μ m is numerically at least 4.5 times that of 3.4 μ m. According to the analysis of the coordinates of WGOs, we find WGOs are mainly distributed in ∣ l ∣ < 60°, coincident with the position of the giant molecular clouds in ∣ l ∣ > 60°. Matching results with various masers show that those three groups of WGOs are at different evolutionary stages. After crossmatching WGOs with published YSO survey catalogs, we infer that ∼50% of WGOs are samples of newly discovered YSOs. In addition, 1260 WGOs are associated with Hi-GAL sources, according to physical parameters estimated by spectral energy distribution fitting, of which 231 are classified as robust MYSOs and 172 as candidate MYSOs.

A mechanism of light absorption at THz frequencies in nematic liquid crystals based on intermolecular dynamics is proposed. In this mechanism, the energy conservation is supplied by acoustic phonons, whereas momentum conservation is provided by static spatial fluctuations of the director field. The mechanism predicts a continuous absorption spectrum in a broad frequency range. [ABSTRACT FROM AUTHOR]

Carbon-oxygen-self-interstitial complexes were investigated in silicon by means of Fourier transform infrared spectroscopy. Upon irradiation, the CiOi defect (C3) forms which for high doses attract self-interstitials (SiIs) leading to the formation of the CiOi(SiI) defect (C4) with two well-known related bands at 939.6 and 1024?cm-1. The bands are detectable in the spectra both in room temperature (RT) and liquid helium (LH) temperature. Upon annealing at 150?°C, these bands were transformed to three bands at 725, 952, and 973?cm-1, detectable only at LH temperatures. Upon annealing at 220?°C, these bands were transformed to three bands at 951, 969.5, and 977?cm-1, detectable both at RT and LH temperatures. Annealing at 280?°C resulted in the transformation of these bands to two new bands at 973 and 1024?cm-1. The latter bands disappear from the spectra upon annealing at 315?°C without the emergence of other bands in the spectra. Considering reaction kinetics and defect metastability, we developed a model to describe the experimental results. Annealing at 150?°C triggers the capturing of SiIs by the C4 defect leading to the formation of the CiOi(SiI)2 complex. The latter structure appears to be bistable: measuring at LH, the defect is in configuration CiOi(SiI)2 giving rise to the bands at 725, 952, and 973?cm-1, whereas on measurements at RT, the defect converts to another configuration CiOi(SiI)2* without detectable bands in the spectra. Possible structures of the two CiOi(SiI)2 configurations are considered and discussed. Upon annealing at 220?°C, additional SiIs are captured by the CiOi(SiI)2 defect leading to the formation of the CiOi(SiI)3 complex, which in turn on annealing at 280?°C converts to the CiOi(SiI)4 complex. The latter defect anneals out at 315?°C, without being accompanied in the spectra by the growth of new bands. [ABSTRACT FROM AUTHOR]

Fourier transform spectra of the four-membered heterocycle silacyclobutane (c-C3H8Si) were recorded in the far infrared region from 100 to 500 cm-1 with a maximum resolution of 0.000959 cm-1 using synchrotron radiation from the Canadian Light Source. The two fundamental bands observed in this region correspond to motions best described as the out-of-plane modes related to ring puckering (ν30) at ∼158 cm-1 and SiH2 rocking (ν29) at ∼410 cm-1. Both bands exhibit complex, dense spectral patterns that arise from ring inversion tunneling of the puckered SCB ring through a planar (C2v) intermediate configuration. Analysis of these patterns revealed rotation-vibration transitions between states of the same inversion symmetry as well as rotation-vibration-inversion transitions that connect states of different inversion symmetry. Infrared ground state combination differences from 1871 pairs of P and R branch transitions were used to accurately determine the spectroscopic parameters for the tunneling-doubled ground state based on a broad range of quantum levels. With the ground state energy levels well-determined, 8255 infrared transitions were assigned and analyzed to derive the band centers, rotational and centrifugal distortion constants for the inversion split ν29 and ν30 vibrational states. Comparison with the band centers predicted via DFT (B3LYP) and MP2 calculations [6-311++G(2d,2p)] suggests that anharmonic corrections found via perturbation theory typically agree within 2% when compared with the observed spectrum of SCB. [ABSTRACT FROM AUTHOR]

Single‐mode distributed feedback GaSb‐based interband cascade lasers with record emission beyond 6.1 µm are presented. The results are based on an epitaxial design with reduced resonant intersubband absorption in the valence band and rebalanced internally generated carriers. The epi‐down mounted 8 µm wide and 1 mm long laser chip is operated in continuous wave mode at room temperature and covers a bandwidth of over 20 nm with temperature and current tuning. At 25°C more than 4 mW of optical output power was measured. [ABSTRACT FROM AUTHOR]

We present ∼10–40 μ m SOFIA-FORCAST images of 11 isolated protostars as part of the SOFIA Massive (SOMA) Star Formation Survey, with this morphological classification based on 37 μ m imaging. We develop an automated method to define source aperture size using the gradient of its background-subtracted enclosed flux and apply this to build spectral energy distributions (SEDs). We fit the SEDs with radiative transfer models, developed within the framework of turbulent core accretion (TCA) theory, to estimate key protostellar properties. Here, we release the sedcreator python package that carries out these methods. The SEDs are generally well fitted by the TCA models, from which we infer initial core masses M _c ranging from 20–430 M _⊙ , clump mass surface densities Σ _cl ∼ 0.3–1.7 g cm ^−2 , and current protostellar masses m _* ∼ 3–50 M _⊙ . From a uniform analysis of the 40 sources in the full SOMA survey to date, we find that massive protostars form across a wide range of clump mass surface density environments, placing constraints on theories that predict a minimum threshold Σ _cl for massive star formation. However, the upper end of the m _* −Σ _cl distribution follows trends predicted by models of internal protostellar feedback that find greater star formation efficiency in higher Σ _cl conditions. We also investigate protostellar far-IR variability by comparison with IRAS data, finding no significant variation over an ∼40 yr baseline.

We show SiC substrate phonon-induced surface plasmon polariton (SPP) formation in epitaxial graphene grown on 4H-SiC, in SiC's restrahlen band (8-10 μm). By fitting measurement to theory, we extract thickness, momentum scattering time (τ), sheet carrier density (ns), and estimate carrier mobility. By showing that [formula], we argue that scattering is dominated by short-range interactions at the SiC/graphene interface. SPP formation finds application in nanophotonic devices for optical computing because of graphene's unique plasmonic properties. [ABSTRACT FROM AUTHOR]

The paper describes experiments revealing the anisotropy of the macroscopic dielectric response of poled lead zirconate titanate ceramics in the phonon frequency region. The results are discussed in terms of distinct polar phonon contributions and effective medium theory. The anisotropy probed in far-infrared experiments can be used to evaluate efficiency of the poling and/or depoling processes. [ABSTRACT FROM AUTHOR]

Time-resolved vibrational femtosecond spectroscopy is employed to investigate the photoinduced Wolff rearrangement reaction of diazonaphthoquinone (DNQ) dissolved in different solvents (methanol and water). DNQ is an important compound in commercial Novolak photoresists. Upon photoexcitation the ketene intermediate appears within 300 fs, indicating that the ketene is formed in a very fast concerted process involving N2 loss and rearrangement. The strong shift of the vibrational band, assigned to the ketene by density functional theory calculations and experimental infrared spectra, toward higher wavenumbers is attributed to vibrational cooling. The relaxation time depends on the solvent (10 ps in methanol and 3 ps in water). However, the spectroscopic data show that the indirect ketene formation via a carbene intermediate might also be involved in the reaction process contributing to the ketene formation on the 10 ps time scale. [ABSTRACT FROM AUTHOR]

The net modal gain, optical loss, and transparency current of high-performance, narrow ridge waveguide interband cascade (IC) lasers have been measured using the Hakki–Paoli technique in the temperature range from T=78 to 270 K. In this temperature range, the optical loss of IC lasers increases from αw≈17 cm-1 at T=78 K to αw≈35 at T=270 K, the transparency current density rises from Itr=10 to 330 A/cm2, and the differential gain decreases from gd≈2.2 cm/A to gd≈0.06 cm/A with a characteristic temperature of T0=130 K. The implications of these observed characteristics for IC lasers are discussed. [ABSTRACT FROM AUTHOR]

Transitions between the spin-rotational levels of the FeH radical in the υ=0 level of the X 4Δ ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. Both pure rotational and fine-structure transitions have been observed; lambda-type doubling is resolved on all the observed transitions. The energy levels of FeH are strongly affected by the breakdown of the Born-Oppenheimer approximation and cannot be modeled accurately by an effective Hamiltonian. The data are therefore fitted to an empirical formula to yield term values and g factors for the various spin-rotational levels involved. Many of the resonances show a doubling that arises from the proton hyperfine structure. These splittings are analyzed in a similar manner. [ABSTRACT FROM AUTHOR]

The different adsorption processes and conformational structure of water molecules at a 0.1 M HClO[sub 4]/Pt(110) interface have been studied by using in-situ infrared-visible sum-frequency generation (SFG) spectroscopy. The O–H stretch resonance is found to be quite weak, while the Pt–H stretch mode arises rapidly in the hydrogen adsorption region and the total symmetric stretch mode ν[sub 1] of ClO[sub 4][sup -] anions dominates the resonant signal in the double layer region. In this work we provide the first spectroscopic evidence that hydrogens and ClO[sub 4][sup -] anions are more favored than water molecules, despite their significant dipole moment, in the competitive adsorption processes below the oxidation potential. Our SFG results suggest that, for a platinum in the 0.1 M HClO[sub 4] solution, most interfacial water molecules are not directly adsorbed but rather are present at the electrode surface as the constituents of hydration shells. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights • Analytical expression of the stored electromagnetic energy by thermal emitters. • Radiation Q-factor for polychromatic sources. • Tungsten-emitters exhibit broad spectral storage and radiative characteristics. • SiC-emitter spectra (radiated power and stored energy) have morphologic resonances. • Q-factor for a thermal emitter depends on its size, temperature, and material. Abstract We examine theoretically (based on fluctuational electrodynamics) the stored electromagnetic energy and radiated power by a spherical thermal emitter. Moreover, we propose a measure for the radiation quality Q -factor for a polychromatic source such as a thermal emitter. We consider that the thermal emitter is made of tungsten and silicon carbide and we study in detail how the aforementioned radiative quantities depend on size and temperature of the antenna. Particularly, we obtain the emissivity (ratio of spectral radiated power by emitter and that by an ideal blackbody), and the spectral density of stored electromagnetic energy normalized with respect to that of a blackbody. For a SiC-emitter, the emissivity and the normalized spectral stored density energy exhibit multiple narrow peaks associated with surface phonon-polariton and whispering gallery mode resonances; while for a W-antenna, high ohmic losses yield broad spectra of the aforementioned quantities (only an interband resonance appears). These spectra depend strongly on particle size; the corresponding unnormalized spectra are perturbed by the temperature. There is an optimal size of the antenna for which the emissivity is maximal; the aforementioned materials yield an emissivity larger than one. The radiation Q -factor decreases as particle radius and temperature increase, implying that the radiation efficiency of a thermal emitter increases as these parameters grow. The Q -factor for a W-antenna is smaller than that for a SiC-antenna (same size and temperature) for nano-scale particles, whereas, for micrometric particles, the opposite happens over a certain temperature range. Our work might have implications for infrared sources and thermophotovoltaics. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the physical associations between blended far-infrared (FIR)-emitting galaxies, in order to identify the level of line-of-sight projection contamination in the single-dish Herschel data. Building on previous work, and as part of the Herschel Extragalactic Legacy Project, we identify a sample of galaxies in the COSMOS field, which are found to be both FIR-bright (typically ∼15 mJy) and blended within the Herschel 250- $$\mu\mathrm{ m}$$ beam. We identify a spectroscopic or photometric redshift for each FIR-bright source. We conduct a joint probability distribution analysis on the redshift probability density functions to determine the fraction of the FIR sources with multiple FIR-bright counterparts that are likely to be found at consistent (Δ $$z$$ < 0.01) redshifts. We find that only three (0.4 per cent) of the pair permutations between counterparts are >50 per cent likely to be at consistent redshifts. A majority of counterparts (72 per cent) have no overlap in their redshift probability distributions whatsoever. This is in good agreement with the results of recent simulations, which indicate that single-dish observations of the FIR sky should be strongly contaminated by line-of-sight projection effects. We conclude that for our sample of 3.6- and 24- $$\mu\mathrm{ m}$$ selected, FIR-bright objects in the COSMOS field, the overwhelming majority of multicomponent FIR systems are line-of-sight projections within the 18.1-arcsec Herschel beam, rather than physical associations. [ABSTRACT FROM AUTHOR]

In order to research the influence of different disturbance rejection rate (DRR) model, the model with different signal point and under a damping moment and spring torque are derived respectively. According to the models the characteristic of seeker and DRR are analyzed. And the relation of DRE and seeker dynamic is proposed. Then according to the different DRR model, the seeker tracking model with DRR is made up and analyzed. To research the influence on guidance loop, the parasitic loop with different DRR models is proposed and analyzed in frequency region, which can provide a reference unstable frequency for control system. Furthermore, a guidance loop with different parasitic loop of DRR is established, and the analysis shown that, the signal outputting point is an significant factor for miss distance in different disturbance torque. At last, a test method based on the guidance and control system is proposed which can show the characteristic of seeker model with parasitic loop effetely. [ABSTRACT FROM AUTHOR]

In this paper, we measure the far-infrared (FIR) and radio flux densities of a sample of 82 local gas-rich galaxies, including 70 'dwarf' galaxies ($$M_*\lt 10^9\, {\rm M_\odot }$$), from the Local Volume $${\rm H\, \small{I}}$$ Survey (LVHIS), which is close to volume limited. It is found that LVHIS galaxies hold a tight linear FIR-radio correlation (FRC) over four orders of magnitude ($$F_{\rm 1.4GHz} \propto F_{\rm FIR}^{1.00\pm 0.08}$$). However, for detected galaxies only, a trend of larger FIR-to-radio ratio with decreasing flux density is observed. We estimate the star formation rate by combining UV and mid-IR data using empirical calibration. It is confirmed that both FIR and radio emission are strongly connected with star formation but with significant non-linearity. Dwarf galaxies are found radiation deficient in both bands, when normalized by star formation rate. It urges a 'conspiracy' to keep the FIR-to-radio ratio generally constant. By using partial correlation coefficient in Pearson definition, we identify the key galaxy properties associated with the FIR and radio deficiency. Some major factors, such as stellar mass surface density, will cancel out when taking the ratio between FIR and radio fluxes. The remaining factors, such as $${\rm H\, \small{I}}$$ -to-stellar mass ratio and galaxy size, are expected to cancel each other due to the distribution of galaxies in the parameter space. Such cancellation is probably responsible for the 'conspiracy' to keep the FRC alive. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the stacked frequency spectrum of a large sample of galaxy clusters using Planck data, together with auxiliary data from the AKARI and IRAS missions. Our primary goal is to search for the imprint of relativistic corrections to the thermal Sunyaev–Zeldovich effect (tSZ) spectrum, which allow to measure the temperature of the intracluster medium. We remove Galactic and extragalactic foregrounds with a matched filtering technique, which is validated using simulations with realistic mock data sets. The extracted spectra show the tSZ signal at high significance and reveal an additional far-infrared (FIR) excess, which we attribute to thermal emission from the galaxy clusters themselves. This excess FIR emission from clusters is accounted for in our spectral model. We are able to measure the tSZ relativistic corrections at 2.2σ by constraining the mean temperature of our cluster sample to |$4.4^{+2.1}_{-2.0} \, \mathrm{keV}$|⁠. We repeat the same analysis on a subsample containing only the 100 hottest clusters, for which we measure the mean temperature to be |$6.0^{+3.8}_{-2.9} \, \mathrm{keV}$|⁠, corresponding to 2.0σ. The temperature of the emitting dust grains in our FIR model is constrained to ≃20 K, consistent with previous studies. Control for systematic biases is done by fitting mock clusters, from which we also show that using the non-relativistic spectrum for SZ signal extraction will lead to a bias in the integrated Compton parameter Y, which can be up to 14% for the most massive clusters. We conclude by providing an outlook for the upcoming CCAT-prime telescope, which will improve upon Planck with lower noise and better spatial resolution. [ABSTRACT FROM AUTHOR]

As no terahertz signal is transmitted through opaque materials, reflection terahertz time-domain spectroscopy is obviously the dedicated setup. On the other hand, optical properties of transparent and thick samples are extracted more accurately with transmission terahertz time-domain spectroscopy. In this paper, we report the intrinsic frontier above or below which it is preferable to use either reflection or transmission setup for probing with the best accuracy possible a given sample. [ABSTRACT FROM AUTHOR]

In this paper, we detail the retrieval methods developed for the analysis of the spectral data from the JIRAM experiment on board of the Juno NASA mission [1], operating in orbit around Jupiter since July 2016. Our focus is on the analysis of the thermal radiation in the 5 µm transparency window in regions of lesser cloud opacity (namely, hot-spots). Moving from the preliminary analysis presented in [2], a retrieval scheme has been developed and implemented as a complete end-to-end processing software. Performances in terms of fit quality and retrieval errors are discussed from tests on simulated spectra, while some example and issue from usage on actual Jupiter data are also discussed. Following the suggestion originally presented in [3] for the analysis of the data from the Near Infrared Mapping Spectrometer (NIMS) on board of the NASA Galileo spacecraft, the state vector to be retrieved has been drastically simplified on physically sounding basis, aiming mostly to distinguish between the 'deep' content of minor gaseous components (H 2 O, NH 3 , PH 3 ) and their relative humidity or fractional scale height in the upper troposphere. The retrieval code is based on a Bayesian scheme [4], complemented by simulated annealing method for most problematic cases. The key parameters retrievable from JIRAM individual spectra are the NH 3 and PH 3 deep contents, the H 2 O vapor relative humidity as well as the total aerosol opacity. Limitations related to the approximations of forward model methods are also assessed quantitatively. [ABSTRACT FROM AUTHOR]

Based on long-term spectral monitoring with high spectral resolution, the optical spectrum of the weak central star of the IR source RAFGL 5081 has been studied for the first time. The spectral type of the star is close to G5-8 II, and its effective temperature is T ≈ 5400 K. An unusual spectral phenomenon was discovered: splitting of the profiles of broad, stationary absorption lines of medium and low intensity. The heliocentric radial velocities V of all components of metal absorption lines, the Na I D lines, and the Hα line were measured for all the observation epochs. The constancy of the absorption lines rules out the possibility that the line splitting is due to binarity. The radial velocities of the wind components in the profiles of the Na I D and Hα lines reach −250 and −600 km/s, respectively. These profiles have narrow components, whose number, depth, and position vary with time. The time variability and multicomponent structure of the profiles of the Na I D and Hα lines indicates inhomogeneity and instability of the circumstellar envelope of RAFGL 5081. The presence of components with velocity V (IS) = −65 km/s in the Na I (1) lines provides evidence that RAFGL 5081 is located behind the Perseus arm, i.e, no closer than 2 kpc. It is noted that RAFGL 5081 is associated with the reflection nebula GN 02.44.7. [ABSTRACT FROM AUTHOR]

The Methanol Multibeam survey has produced the largest and most complete census of methanol and excited-state hydroxyl masers in the Galaxy to date. Observing the entire Galactic plane visible from the Southern hemisphere for 6668-MHz methanol and 6030/6035-MHz hydroxyl masers, to an rms sensitivity of 0.015 Jy km s-1, the survey has detected a total of 972 methanol maser sources, implying a total Galactic population of ~1290 sources with flux densities above the survey 3σ peak flux density limit of 0.51 Jy. We present here the statistical properties of the methanol detections of the survey, including distributions in flux density, variability and range of source velocities. The data suggest that the weaker masers exhibit greater variability. We also present an analysis of the Galactic distribution of 6668-MHz methanol masers. For the Galactic distribution, we present kinematic distance resolutions to an additional 202 sources to those published previously, and collate these with previous allocations, as well as exploring a recent Bayesian distance approach based on maser parallaxes to separately determine distances. We examine Galactic structure and determine the luminosity function of the Galactic population of methanol masers. We find that more luminous masers have an evenly distributed wide range of velocity widths compared with less luminous masers being dominated by narrow velocity ranges, with the implication that this may be tied to the evolution of the host protostar(s). We also see an indication that brighter sources are seen towards the arm origins. [ABSTRACT FROM AUTHOR]

Non-interferometric phase-space tomography is used to characterize the spatial coherence properties of scalar quasi-monochromatic partially coherent optical fields. Three sources were investigated and characteristic projections through the correlation functions determined. It was seen that a single-mode fibre-coupled source exhibited a much longer coherence length than a multi-mode fibre-coupled source. Both sources exhibited a high degree of symmetry. A collimated light emitted diode, on the other hand, was shown to have a short spatial coherence length and clear asymmetries were evident. [ABSTRACT FROM AUTHOR]

We give an introduction to several regularization schemes that deal with ultraviolet and infrared singularities appearing in higher-order computations in quantum field theories. Comparing the computation of simple quantities in the various schemes, we point out similarities and differences between them. [ABSTRACT FROM AUTHOR]

Atmospheric Infrared Sounder (AIRS) temperature profiles during the period 2003–2013 are used to examine the warm core structures and evolution characteristics associated with the formation and development of western North Pacific (WNP) tropical cyclones (TCs). The warm core with a steady 1.5-K warming in the layer of 500–300 hPa occurs 24 h prior to tropical storm formation. Apparent eye warming extends upward to upper troposphere and downward to near surface after tropical storm formation. TC intensity shows a robust positive correlation with the warm core strength and has a weaker but still significant positive correlation with the warm core height (the weaker correlation is primarily attributed to the scattered warm core heights of weak TCs). Future 24-h intensity change of TCs has little correlation with the warm core height while it has a significant negative correlation with the warm core strength. Weak to moderate warm core at 500–200 hPa may be a necessary but not sufficient initial condition for TC rapid intensification. AIRS-observed warm core structures, in combination with other environmental factors, have the potential to improve the prediction of tropical storm formation and rapid intensification of WNP TCs. [ABSTRACT FROM AUTHOR]

The AGN. I examine the average spectral energy distributions (SEDs) of two samples of the most powerful, unobscured quasi-stellar objects (QSOs) at 2

Hybrid materials in optoelectronic devices can generate new functionality or provide synergistic effects that enhance the properties of each component. Here, high-performance phototransistors with broad spectral responsivity in UV-vis-near-infrared (NIR) regions, using gold nanorods (Au NRs)-decorated n-type organic semiconductor and N, N′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) nanowires (NWs) are reported. By way of the synergistic effect of the excellent photo-conducting characteristics of single-crystalline BPE-PTCDI NW and the light scattering and localized surface plasmon resonances (LSPR) of Au NRs, the hybrid system provides new photo-detectivity in the NIR spectral region. In the UV-vis region, hybrid nanomaterial-based phototransistors exhibit significantly enhanced photo-responsive properties with a photo-responsivity ( R) of 7.70 × 105 A W−1 and external quantum efficiency (EQE) of 1.42 × 108% at the minimum light intensity of 2.5 µW cm−2, which are at least tenfold greater than those of pristine BPE-PTCDI NW-based ones and comparable to those of high-performance inorganic material-based devices. While a pristine BPE-PTCDI NW-based photodetector is insensitive to the NIR spectral region, the hybrid NW-based phototransistor shows an R of 10.7 A W−1 and EQE of 1.35 × 103% under 980 nm wavelength-NIR illumination. This work demonstrates a viable approach to high-performance photo-detecting systems with broad spectral responsivity. [ABSTRACT FROM AUTHOR]