Rayleigh-Jeans Research Articles

Red Stellar Populations and Dust Extinction toward W3

We explore red stellar populations toward the W3 giant molecular cloud through the use of optical-to-infrared (IR) photometry and Gaia DR 3 data, simultaneously characterizing stellar content and properties of dust in the molecular medium. We use a Rayleigh–Jeans color excess method modified to de-redden stellar observations of both red giants (RGs) and OB stars, and construct an IR Hertzsprung–Russell diagram validated against the Besançon Galactic model. Taking advantage of the near-universal IR interstellar extinction law and precise Gaia measurements, we develop a method for obtaining the spectral classification, foreground extinction, and distance moduli of stars, validated by spectroscopically confirmed OB stars. We constrain the observed parallax and proper motion of OB stars in W3, demonstrating the importance of considering systematic effects in the parallax bias, and assign parallax- and proper-motion-based cloud membership to our stellar samples. While it has been assumed that all spectroscopic OB stars are inside the W3 cloud, we find evidence of seven background B stars and three potential runaway OB stars. The methods developed here, which are based on known stellar populations, enable us to identify 82 new OB candidates that are confidently within the cloud. We quantify several dust-to-dust empirical correlations, in particular the IR color excess E(H − [4.5]) and the optical depth τ 1 of submillimeter dust emission at 1 THz using RGs behind W3, measuring a best fit of E(H−[4.5])=(1.07±0.04)×103τ1,HOTT+(0.00±0.02)mag .

Nonconventional thermal states of interacting bosonic oligomers

There has recently been a growing effort to understand the physics and intricate dynamics of many-body and many-state (multimode) interacting bosonic systems in a comprehensive manner. For instance, in photonics, nonlinear multimode fibers are being intensely investigated nowadays due to their promise for ultrahigh-bandwidth and high-power capabilities. Similar prospects are being pursued in connection with magnon Bose-Einstein (BE) condensates, and ultracold atoms in periodic lattices for room-temperature quantum devices and quantum computation, respectively. While it is practically impossible to monitor the phase space of such complex systems (classically or quantum mechanically), thermodynamics has succeeded in predicting their thermal state: the Rayleigh-Jeans (RJ) distribution for classical fields and the BE distribution for quantum systems. These distributions are monotonic and promote either the ground state or the most excited mode. Here, we demonstrate the possibility to advance the participation of other modes in the thermal state of bosonic oligomers. The resulting nonmonotonic modal occupancies are described by a microcanonical treatment, while they deviate drastically from the RJ/BE predictions of canonical and grand-canonical ensembles. Our results provide a paradigm of ensemble equivalence violation and can be used for designing the shape of thermal states. Published by the American Physical Society 2024

Entropy Considerations in Stochastic Electrodynamics

The use of entropy concepts in the field of stochastic electrodynamics is briefly reviewed here. Entropy calculations that have been fully carried out to date are discussed in two main cases: first, where electric dipole oscillators interact with zero-point, or zero-point plus Planckian, or Rayleigh–Jeans radiation; and second, where only these radiation fields exist within a cavity. The emphasis here is on the first, more complicated, case, where both charged particles and radiation fields are present and interacting. Unlike the usual exposition on entropy in classical statistical mechanics, involving probabilistic notions of phase-space occupation, the calculations to date for both particles and fields, or for fields alone, follow the caloric entropy method, where the notions of heat flow, adiabatic surfaces, and isothermal conditions are utilized. Probability notions certainly still enter into the calculations, as the fields and charged particles interact stochastically together, following Maxwellian electrodynamics. Examples of phase-space calculations for harmonic oscillators and classical hydrogen atoms are carried out, emphasizing how much farther caloric entropy calculations have successfully gone.

Nonlinear defect theory of thermal relaxation in complex multimoded systems

We show that a single nonlinear defect can thermalize an initial excitation towards a Rayleigh-Jeans (RJ) state in complex multimoded systems. The thermalization can be hindered by disorder-induced localization phenomena, which drive the system into a metastable RJ state. It can differ dramatically from the thermal RJ and it involves only a (quasi)isolated set of prethermal modes whose density can be predicted using a renormalization group theory. Importantly, we establish a connection between the modal relaxation rates that dictate the dynamics towards (quasi)equilibrium and the Thouless conductance. This connection allows us to derive the whole modal relaxation rate distribution. Our results are relevant to photonics, optomechanics, and cold atoms. Published by the American Physical Society 2024

Why Observations at Mid-infrared Wavelengths Partially Mitigate M Dwarf Star Host Stellar Activity Contamination in Exoplanet Transmission Spectroscopy

Exoplanet atmosphere transmission spectroscopy for planets orbiting M dwarf stars faces significant challenges due to contamination from stellar magnetic features, i.e., spots and faculae. These features make the stellar surface inhomogeneous and introduce wavelength-dependent signals in the transmission spectrum that complicate its analysis. We identify and explain why using observations at infrared wavelengths greater than a few microns partially mitigates stellar contamination. At these wavelengths the intensity sensitivity to temperature weakens, with two significant consequences. First, the contribution of spots and faculae has a diminished effect because their flux contrast to the quiet-star regions lessens. Second, the star’s spectral features compress in magnitude, an outcome of spectral features being shaped by the star’s photospheric vertical temperature gradient. Both factors are due to the Planck function moving from exponential to linear in temperature toward mid-infrared (mid-IR) wavelengths (the “Rayleigh–Jeans tail”). In contrast to stellar spectra, the depth of the transmission spectroscopy features does not fundamentally vary with wavelength as it is primarily determined by the planet’s atmospheric scale height. The magnitude of reduction in stellar contamination is a factor of a few to several at mid-IR versus near-IR wavelengths, but whether or not this is enough to bypass stellar contamination ultimately depends on the spot coverage area. Nonetheless, the flattening of thermal emission spectral features at IR wavelengths is universal.

Dissipative Soliton Resonance: Adiabatic Theory and Thermodynamics

We present the adiabatic theory of dissipative solitons (DS) of complex cubic-quintic nonlinear Ginzburg–Landau equation (CQGLE). Solutions in the closed analytical form in the spectral domain have the shape of Rayleigh–Jeans distribution for a positive (normal) dispersion. The DS parametric space forms a two-dimensional (or three-dimensional for the complex quintic nonlinearity) master diagram connecting the DS energy and a universal parameter formed by the ratio of four real and imaginary coefficients for dissipative and non-dissipative terms in CQGLE. The concept of dissipative soliton resonance (DSR) is formulated in terms of the master diagram, and the main signatures of transition to DSR are demonstrated and experimentally verified. We show a close analogy between DS and incoherent (semicoherent) solitons with an ensemble of quasi-particles confined by a collective potential. It allows applying the thermodynamical approach to DS and deriving the conditions for the DS energy scalability.

Mapping dust in the giant molecular cloud Orion A

ABSTRACT The Sun is located close to the Galactic mid-plane, meaning that we observe the Galaxy through significant quantities of dust. Moreover, the vast majority of the Galaxy’s stars also lie in the disc, meaning that dust has an enormous impact on the massive astrometric, photometric and spectroscopic surveys of the Galaxy that are currently underway. To exploit the data from these surveys we require good three-dimensional maps of the Galaxy’s dust. We present a new method for making such maps in which we form the best linear unbiased predictor of the extinction at an arbitrary point based on the extinctions for a set of observed stars. This method allows us to avoid the artificial inhomogeneities (so-called ‘fingers of God’) and resolution limits that are characteristic of many published dust maps. Moreover, it requires minimal assumptions about the statistical properties of the interstellar medium. In fact, we require only a model of the first and second moments of the dust density field. The method is suitable for use with directly measured extinctions, such as those provided by the Rayleigh–Jeans colour excess method, and inferred extinctions, such as those provided by hierarchical Bayesian models like StarHorse. We test our method by mapping dust in the region of the giant molecular cloud Orion A. Our results indicate a foreground dust cloud at a distance of 350 pc, which has been identified in work by another author.

Some Interesting Facts About Planck’s Law of Blackbody Radiation

Introductory textbooks of Modern and Thermal Physics discuss the Planck radiation law as a backbone of the blackbody radiation spectrum. This law is used to explain the intensity of blackbody radiation as a function of either frequency or wavelength at a given temperature. In the introductory coursework, the Planck’s formula is also used to study other blackbody radiation laws such as Stefans–Boltzmann law, Wien’s Displacement law, Rayleigh–Jeans Law and Wien’s Distribution law. In this work, we highlight some interesting facts related to the total energy density, photon number density and average energy of photon of blackbody radiation. The main objective of this work is to focus on the lesser known features associated with physics of blackbody radiation. We believe that these simple analytic calculations may give very useful and interesting information about the Planck radiation law to the undergraduate students.

Transverse mode distribution in multimode diode-pumped Raman fiber laser

Raman lasers based on multimode graded-index fibers may generate high-quality (M2∼2) Stokes beams when pumped by highly multimode (M2>30) laser diodes. Here we, examine, both experimentally and theoretically, the energy distribution of the output Stokes beam across the principal quantum mode number n in a bent multimode fiber operating well above the Raman threshold. In contrast to Kerr spatial beam cleaning, leading to a Rayleigh–Jeans mode power distribution, in a multimode Raman fiber laser, we find that the output mode powers approach an exponential distribution. We introduce a coupled-mode equations model, including random linear coupling between neighboring mode groups, and obtain a good agreement between numerical simulations and experimental results. The model shows that, for typical mode coupling coefficients, the randomization of the mode power distribution is compensated by both nonlinear (Raman and Kerr) effects and linear filtering from the fs-inscribed fiber Bragg grating, both acting on the Stokes beam over successive round trips. When random coupling becomes the dominating factor, the mode power distribution of the Stokes beam tends to equipartition, similar to what is observed with large-size highly multimode beams of low intensity (and nonlinearity) in the absence of any filtering.

An improved method to measure 12C/13C and 14N/15N abundance ratios: revisiting CN isotopologues in the Galactic outer disc

ABSTRACT The variations of elemental abundance and their ratios along the Galactocentric radius result from the chemical evolution of the Milky Way discs. The $\rm ^{12}C/^{13}C$ ratio in particular is often used as a proxy to determine other isotopic ratios, such as $\rm ^{16}O/^{18}O$ and $\rm ^{14}N/^{15}N$. Measurements of $\rm ^{12}CN$ and $\rm ^{13}CN$ (or $\rm C^{15}N$) – with their optical depths corrected via their hyper-fine structure lines – have traditionally been exploited to constrain the Galactocentric gradients of the CNO isotopic ratios. Such methods typically make several simplifying assumptions (e.g. a filling factor of unity, the Rayleigh–Jeans approximation, and the neglect of the cosmic microwave background) while adopting a single average gas phase. However, these simplifications introduce significant biases to the measured $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$. We demonstrate that exploiting the optically thin satellite lines of 12CN constitutes a more reliable new method to derive $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$ from CN isotopologues. We apply this satellite-line method to new IRAM 30-m observations of 12CN, 13CN, and C15N N = 1 → 0 towards 15 metal-poor molecular clouds in the Galactic outer disc (Rgc > 12 kpc), supplemented by data from the literature. After updating their Galactocentric distances, we find that $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$ gradients are in good agreement with those derived using independent optically thin molecular tracers, even in regions with the lowest metallicities. We therefore recommend using optically thin tracers for Galactic and extragalactic CNO isotopic measurements, which avoids the biases associated with the traditional method.

CEERS MIRI Imaging: Data Reduction and Quality Assessment

The Cosmic Evolution Early Release Science Survey (CEERS), targeting the Extended Groth Strip extragalactic field, is one of the James Webb Space Telescope Director’s Discretionary Early Release Science programs. To date, all observations have been executed and include NIRCam/MIRI imaging and NIRSpec/NIRCam spectroscopic exposures. Here we discuss the MIRI imaging, which includes eight pointings, four of which provide deep imaging with the bluer bands (F560W and F770W) and four of which provide contiguous wavelength coverage in F1000W, F1280W, F1500W, and F1800W, where two of these also include coverage in F770W and F2100W. We present a summary of the data, data quality, and data reduction. The data reduction is based on the jwst calibration pipeline combined with custom modifications and additional steps designed to enhance the output quality, including improvements in astrometry and the removal of detector artifacts. We estimate the image depth of the reduced mosaics and show that these generally agree with expectations from the Exposure Time Calculator. We compare the MIRI F560W and F770W flux densities for bright sources to measurements from Spitzer/IRAC Ch3 (5.8 μm) and Ch4 (8.0 μm), and we find that they agree with systematic differences of <0.1 mag. For the redder MIRI bands, we assess their quality by studying the spectral energy distributions (SEDs) of Galactic stars. The SEDs are consistent with the expected Rayleigh–Jeans law with a deviation of ∼0.03 mag, indicating that the MIRI colors are reliable. We also discuss all publicly released data products (images and source catalogs), which are available on the CEERS website (https://ceers.github.io/).

Theory of localization-hindered thermalization in nonlinear multimode photonics

Our society’s appetite for ultra-high bandwidth communication networks and high-power optical sources, together with recent breakthroughs in mode multiplexing/demultiplexing schemes, forced the photonics community to reconsider the deployment of nonlinear multimode systems. These developments pose fundamental challenges stemming from the complexity of nonlinear mode-mode mixing by which they exchange energy in the process towards an equilibrium Rayleigh-Jeans (RJ) distribution. Here we develop a universal one-parameter scaling theory for the relaxation rates of out-of-equilibrium excitations towards their RJ thermal state. The theory predicts an exponential suppression of the rates with increasing disorder due to the formation of stable localization clusters resisting the nonlinear mode-mode interactions that tend to separate them. For low optical temperatures, the rates experience a crossover from linear to nonlinear temperature dependence which reflects a disorder-induced reorganization of the low frequency eigenmodes. Our theory will guide the design of nonlinear multimode photonic networks with tailored relaxation-scales.

X-Ray and Near-Infrared Observations of the Middle-aged Pulsar B1055–52, Its Multiwavelength Spectrum, and Proper Motion* * Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. Based also on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by

Previous observations of the middle-aged γ-ray, X-ray, and radio pulsar B1055–52 indicated some peculiarities, such as a suspected changing of the X-ray flux and spectral parameters, a large excess of the alleged thermal component of the UV spectrum over the Rayleigh–Jeans extension of the X-ray thermal spectrum, and a possible double break in the nonthermal spectral component between the optical and X-ray bands. We observed PSR B1055–52 with the XMM-Newton observatory in X-rays and the Hubble Space Telescope in near-infrared (NIR). The analysis of the XMM-Newton observations does not support the notion of long-term changes in the X-ray flux and broadband X-ray spectrum of the pulsar. Using an observing mode less affected by background noise than the previous XMM-Newton observations, we constrain the power-law (PL) spectral index as (F ν ∝ ν α ) in the energy band 3–10 keV. From the NIR–optical data we obtain a PL slope α O = −0.24 ± 0.10 for the color index E(B − V) = 0.03 mag. The slopes and fluxes of the NIR–optical and X-ray nonthermal spectra suggest that the NIR through X-ray emission can be described by the same PL and is generated by the same mechanism, unlike the pulsar’s γ-ray emission. The excess of the UV thermal component over the extension of the X-ray thermal component became smaller but did not disappear, indicating a nonuniformity of the bulk surface temperature. The NIR data also enable us to measure the proper motion accurately, with values μ α = 47.5 ± 0.7 mas yr−1 and μ δ = −8.7 ± 0.7 mas yr−1.

The First JWST Spectral Energy Distribution of a Y Dwarf

We present the first JWST spectral energy distribution of a Y dwarf. This spectral energy distribution of the Y0 dwarf WISE J035934.06−540154.6 consists of low-resolution (λ/Δλ ∼100) spectroscopy from 1–12 μm and three photometric points at 15, 18, and 21 μm. The spectrum exhibits numerous fundamental, overtone, and combination rotational–vibrational bands of H2O, CH4, CO, CO2, and NH3, including the previously unidentified ν 3 band of NH3 at 3 μm. Using a Rayleigh–Jeans tail to account for the flux emerging at wavelengths greater than 21 μm, we measure a bolometric luminosity of 1.523 ± 0.090 × 1020 W. We determine a semiempirical effective temperature estimate of K using the bolometric luminosity and evolutionary models to estimate a radius. Finally, we compare the spectrum and photometry to a grid of atmospheric models and find reasonably good agreement with a model having T eff = 450 K, log g = 3.25 [cm s−2], and [M/H] = −0.3. However, the low surface gravity implies an extremely low mass of 1 M Jup and a very young age of 20 Myr, the latter of which is inconsistent with simulations of volume-limited samples of cool brown dwarfs.

Rayleigh–Jeans thermalization vs beam cleaning in multimode optical fibers

Classical nonlinear waves exhibit, as a general rule, an irreversible process of thermalization toward the Rayleigh–Jeans equilibrium distribution. On the other hand, several recent experiments revealed a remarkable effect of spatial organization of an optical beam that propagates through a graded-index multimode optical fiber (MMF), a phenomenon termed beam self-cleaning. Our aim here is to evidence the qualitative impact of disorder (weak random mode coupling) on the process of Rayleigh–Jeans thermalization by considering two different experimental configurations. In a first experiment, we launch speckle beams in a relatively long MMF. Our results report a clear and definite experimental demonstration of Rayleigh–Jeans thermalization through light propagation in MMFs, over a broad range of kinetic energy (i.e., degree of spatial coherence) of the injected speckle beam. In particular, the property of energy equipartition among the modes is clearly observed in the condensed regime. The experimental results also evidence the double turbulence cascade process: while the power flows toward the fundamental mode (inverse cascade), the energy flows toward the higher-order modes (direct cascade). In a 2nd experiment, a coherent laser beam is launched into a relatively short MMF length. It reveals an effect of beam cleaning driven by an incipient process of Rayleigh–Jeans thermalization. As discussed through numerical simulations, the fast process of Rayleigh–Jeans thermalization observed in the 1st experiment can be attributed due to a random phase dynamics among the modes, which is favored by the injection of a speckle beam and the increased impact of disorder in the long fiber system.

Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR.

A half-wave plate (HWP) is often used as a modulator to suppress systematic error in the measurements of cosmic microwave background (CMB) polarization. A HWP can also be used to measure circular polarization (CP) through its optical leakage from CP to linear polarization. The CP of the CMB is predicted from various sources, such as interactions in the Universe and extension of the standard model. Interaction with supernova remnants of population III stars is one of the brightest CP sources. Thus, the observation of the CP of CMB is a new tool for searching for population III stars. In this paper, we demonstrate the improved measurement of the leakage coefficient using the transmission measurement of an actual HWP in the laboratory. We measured the transmittance of linearly polarized light through the HWP used in Polarbear in the frequency range of 120-160GHz. We evaluate the properties of the HWP by fitting the data with a physical model using the Markov Chain Monte Carlo method. We then estimate the band-averaged CP leakage coefficient using the physical model. We find that the leakage coefficient strongly depends on the spectra of CP sources. We thus calculate the maximum fractional leakage coefficient from CP to linear polarization as 0.133 ± 0.009 in the Rayleigh-Jeans spectrum. The nonzero value shows that Polarbear has a sensitivity to CP. Additionally, because we use the bandpass of detectors installed in the telescope to calculate the band-averaged values, we also consider systematic effects in the experiment.

Spatiotemporal mode decomposition of ultrashort pulses in linear and nonlinear graded-index multimode fibers

We develop a spatiotemporal mode decomposition technique to study the spatial and temporal mode power distribution of ultrashort pulses in long spans of graded-index multimode fiber, for different input laser conditions. We find that the beam mode power content in the dispersive pulse propagation regime can be described by the Bose–Einstein law, as a result of the process of power diffusion from linear and nonlinear mode coupling among nondegenerate mode groups. In the soliton regime, the output mode power distribution approaches the Rayleigh–Jeans law.

Thermalization of the Ablowitz-Ladik lattice in the presence of non-integrable perturbations.

We investigate the statistical mechanics of the photonic Ablowitz-Ladik lattice, the integrable version of the discrete nonlinear Schrödinger equation. In this regard, we demonstrate that in the presence of perturbations, the complex response of this system can be accurately captured within the framework of optical thermodynamics. Along these lines, we shed light on the true relevance of chaos in the thermalization of the Ablowitz-Ladik system. Our results indicate that when linear and nonlinear perturbations are incorporated, this weakly nonlinear lattice will thermalize into a proper Rayleigh-Jeans distribution with a well-defined temperature and chemical potential, in spite of the fact that the underlying nonlinearity is non-local and hence does not have a multi-wave mixing representation. This result illustrates that in the supermode basis, a non-local and non-Hermitian nonlinearity can in fact properly thermalize this periodic array in the presence of two quasi-conserved quantities.

Universality of light thermalization in multimoded nonlinear optical systems

Recent experimental studies in heavily multimoded nonlinear optical systems have demonstrated that the optical power evolves towards a Rayleigh–Jeans (RJ) equilibrium state. To interpret these results, the notion of wave turbulence founded on four-wave mixing models has been invoked. Quite recently, a different paradigm for dealing with this class of problems has emerged based on thermodynamic principles. In this formalism, the RJ distribution arises solely because of ergodicity. This suggests that the RJ distribution has a more general origin than was earlier thought. Here, we verify this universality hypothesis by investigating various nonlinear light-matter coupling effects in physically accessible multimode platforms. In all cases, we find that the system evolves towards a RJ equilibrium—even when the wave-mixing paradigm completely fails. These observations, not only support a thermodynamic/probabilistic interpretation of these results, but also provide the foundations to expand this thermodynamic formalism along other major disciplines in physics.

Dust Temperature Uncertainties Hamper the Inference of Dust and Molecular Gas Masses from the Dust Continuum Emission of Quiescent High-redshift Galaxies

Single flux density measurements at observed-frame submillimeter and millimeter wavelengths are commonly used to probe dust and gas masses in galaxies. In this Letter, we explore the robustness of this method to infer dust mass, focusing on quiescent galaxies, using a series of controlled experiments on four massive halos from the Feedback in Realistic Environments project. Our starting point is four star-forming central galaxies at seven redshifts between z = 1.5 and z = 4.5. We generate modified quiescent galaxies that have been quenched for 100 Myr, 500 Myr, or 1 Gyr prior to each of the studied redshifts by reassigning stellar ages. We derive spectral energy distributions for each fiducial and modified galaxy using radiative transfer. We demonstrate that the dust mass inferred is highly dependent on the assumed dust temperature, T dust, which is often unconstrained observationally. Motivated by recent work on quiescent galaxies that assumed T dust ∼ 25 K, we show that the ratio between dust mass and 1.3 mm flux density can be higher than inferred by up to an order of magnitude, due to the considerably lower dust temperatures seen in non-star-forming galaxies. This can lead to an underestimation of dust mass (and, when submillimeter flux density is used as a proxy for molecular gas content and gas mass). This underestimation is most severe at higher redshifts, where the observed-frame 1.3 mm flux density probes rest-frame wavelengths far from the Rayleigh–Jeans regime, and hence depends superlinearly on dust temperature. We fit relations between ratios of rest-frame far-infrared flux densities and mass-weighted dust temperature that can be used to constrain dust temperatures from observations and hence derive more reliable dust and molecular gas masses.