We investigate the effects of source confusion expected in observations with GREX-PLUS, a JAXA L-class space infrared telescope mission candidate with a wide-field infrared camera covering 2-8 um with a field of view of 0.50 deg^2. For the deep imaging band near 4 um, we calculate the GREX-PLUS PSF and ghost based on the latest optical design, and consider two representative imaging performance cases with PSF FWHM values of 0.9 and 1.2 arcsec. We construct simulated GREX-PLUS images at different depths by convolving JWST NIRCam imaging data from JADES, GLASS, CEERS, and COSMOS-Web with the PSF+ghost kernel. Comparing the limiting magnitudes estimated from random aperture photometry using the same aperture sizes, we find that the simulated GREX-PLUS images are shallower than the original JWST images, with larger deviations for deeper original JWST images. This likely reflects unresolved faint sources and extended PSF+ghost wings from bright sources, which elevate background fluctuations in blank regions. Nevertheless, the limiting magnitudes continue to improve with increasing integration time down to 27 mag, without a clear plateau at depths comparable to the planned GREX-PLUS deep survey, although the improvement becomes progressively less efficient toward longer integrations. Based on Monte Carlo simulations, we estimate detection completeness and correct the number counts for magnitude bias and incompleteness, finding that confusion-induced blending can reduce the completeness even at magnitudes well above the nominal 5-sigma depth. The completeness-corrected number counts agree well with the JWST-based number counts down to around the detection limit. Overall, our results suggest that statistical studies of faint galaxies remain feasible for GREX-PLUS; however, survey planning should account for less efficient depth improvement toward longer integrations due to source confusion.

Diffuse far-infrared synchrotron emission filling the northern inner lobe of the radio galaxy Centaurus A is investigated with the Spectral and Photometric Imaging Receiver onboard the Herschel observatory at its three photometric bands. The far-infrared flux density spatially integrated over the lobe is measured as S-v= 1 . 63 +/- 0 . 05 Jy at the wavelength of 500 & micro;m ( the frequency of 600 GHz). A comparison between the far-infrared spectral index derived with Herschel (alpha = 1 . 32 +/- 0 . 19 ) and the radio index (alpha = 0 . 66 +/- 0 . 04 ) suggests a spectral break between these frequency ranges. The change of the spectral index through the break is indicated to be consistent with that of the standard cooling break (Delta alpha = 0 . 5 ) predicted for particle acceleration under the continuous energy injection condition. A broken power-law model incorporating the standard cooling break yields the break frequency as nu(b )= 218 +/- 83 GHz. From the measured cooling break frequency, the magnetic field of the northern inner lobe is evaluated as B less than or similar to 100 & micro;G. It is quantitatively estimated that the adiabatic cooling puts only a minor impact on the derived magnetic field. This magnetic field is higher than that under the minimum-energy condition by more than a factor of 5. In addition, the derived magnetic field of the lobe is suggested to be at least by a factor of 4 stronger than that of the inner-jet region implied in the previous very-high-energy gamma-ray study. Even if the line-of-sight orientation of the lobe is considered in its possible extreme case, the magnetic field is found to be reduced only by a factor of 2, and the above arguments about the strong magnetic field basically holds. The science impact of this result is discussed from the viewpoints of jet energetics, and of ultra-high energy cosmic rays.

The X-ray Imaging Spectroscopy Mission (XRISM) provides the best spectral resolution with which to study sulfur (S) K-shell photoabsorption features from the interstellar medium (ISM). For the first time, we demonstrate the high-signal detection of interstellar atomic S ii K-beta absorption in the spectrum of X-ray binaries (XRBs) 4U 1630-472 and GX 340$+$0. The persistence of this feature across multiple instruments, targets, and flux states implies that it is interstellar in nature. We measure the S ii K$\beta$ line centroid at $2470.8 \pm 1.1$ eV after including systematic uncertainties. We also find that the most recently published high-resolution S ii absorption template requires a systematic energy scale shift of $+7\!-\!8$ eV, which is comparable to the level of disagreement among various atomic modeling procedures. The XRISM 300 ks observation of GX 340$+$0 provides unprecedented signal-to-noise in the S K region, and we find evidence of residual absorption from solid S in the spectra of GX 340$+$0. Absorption templates from three Fe-S compounds, troilite (FeS), pyrrhotite (Fe$_7$S$_8$) and pyrite (FeS$_2$), provide equally good fits to the residuals. Even though we are not able to distinguish among these three compounds, they provide equal estimates for the abundance of S locked in dust grains. Having accounted for both the gaseous and solid S in the GX 340$+$0 sightline provides us with a direct measurement of S depletion, which is $40{\%} \pm 15\%$. Our depletion measurement provides an upper limit to the fraction of interstellar Fe bound in Fe-S compounds of ${<}25\%$, which is consistent with prior studies of Fe-S compounds via Fe L-shell absorption. Both XRBs in this study are at a distance of approximately 11 kpc and on the opposite side of the Galactic disk, suggesting that this value could represent the average S depletion of the Milky Way when integrated across all phases of the ISM.

It is presented that the Probe far-Infrared Mission for Astrophysics (PRIMA) has a high potential to study particle acceleration phenomena associated with jets emanating from active galactic nuclei. A special focus is put on hot spots of radio galaxies because they are widely regarded as the jet-terminal shock where particles are accelerated via the diffusive shock acceleration. To investigate the particle acceleration condition in the hot spots, it is of prime importance to evaluate their magnetic field strength. As a useful indicator of the magnetic field, we propose to adopt a synchrotron spectral feature called the cooling break, of which the frequency is determined by the mutual balance between the synchrotron radiative cooling and the adiabatic one. Referring to the standard physical parameter of the hot spots, the cooling break is expected to reside in or slightly below the far-infrared range covered with PRIMA. The feasibility of the PRIMA observations to measure the far-infrared flux density and to constrain their cooling break frequency is discussed for nearby well-studied hot spots. An affordable observational strategy with PRIMA is described. A possible application of the method to lobes of radio galaxies is also briefly discussed.

We discovered a hyperluminous dust-obscured galaxy with mysterious blue-excess emission (BlueDOG) in the rest-frame UV of its spectral energy distribution (SED) from a multiwavelength survey in the AKARI Deep Field - South (ADF-S). We present the results of SED analysis with multiwavelength photometric data and spectroscopic analysis, observed with Gemini-S/GMOS, FLAMINGOS-2, to explore the origin of blue-excess emission of a hyperluminous BlueDOG, ADFS-KMTDOG-102, at z = 2.6. The SED analysis shows that this BlueDOG is a highly massive system (log M _* / M _⊙ = 12.3) with substantial extinction. Additionally, the proportion of the old stellar population exceeds that of the young stellar population, which suggests stellar evolution cumulated from the early Universe. The mass of the supermassive black hole estimated using the extinction-corrected broad H α emission line yields log M _BH / M _⊙ = 10.2. We discuss the similarity between the BlueDOG and “Little Red Dots” (LRDs), recently discovered with the James Webb Space Telescope, showing SED shapes remarkably similar to those of LRDs. The UV emission line ratios indicate that the emission lines are primarily powered by the central active galactic nuclei (AGN). In contrast, the origin of the blue-excess UV continuum remains ambiguous, since both recent star formation and AGN-induced scattered light are viable explanations, based on the results from the SED fitting and scattered light modeling.

We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) and Mid-infrared Instrument integral field spectroscopy of the nearby blue compact dwarf II Zw 40, which has a low metallicity of 25% of solar. Leveraging the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec, we present robust detections of the 3.3 μ m polycyclic aromatic hydrocarbon (PAH) emission on 20 pc scales. The strength of the Pf δ emission relative to the 3.3 PAH feature is significantly stronger than typical higher-metallicity star-forming galaxies. We find that 3.3 μ m PAH emission is concentrated near the northern super star cluster and is cospatial with CO gas. A strong correlation exists between the 3.3/11.3 PAH ratio and radiation hardness probed by [Ne iii ]/[Ne ii ], providing evidence of photodestruction of PAH molecules in intense radiation environments. Our analysis shows that while the overall PAH fraction is lower in II Zw 40 than in higher-metallicity galaxies, the contribution of the 3.3 μ m PAH feature to the total PAH emission is higher. We propose that the PAH size distribution is fundamentally shaped by two competing mechanisms in low-metallicity environments: photodestruction and inhibited growth. Additionally, the high radiation field intensity in II Zw 40 suggests that multiphoton heating of PAHs may be an important effect. As one of the first spatially resolved studies of aromatic emission in a low-metallicity environment, our spectroscopic results offer practical guidance for future observations of the 3.3 μ m PAH feature in low-metallicity galaxies using JWST.

Actuators are widely used in various mechanical products. However, there have been no actuators that can exhibit high actuation stresses and strains at cryogenic temperatures. Although shape memory alloys (SMAs) are attractive candidates for thermally driven actuators with high actuation stresses and strains, the operation of conventional SMAs is limited to a narrow temperature range near the room temperature. Here, we report the shape memory effect under tensile conditions with a high work output across a wide temperature range of 50–270 K in Cu-Al-Mn-based alloys. In addition, a mechanical heat switch using Cu-Al-Mn was designed for thermal insulation in space infrared telescope, and we demonstrated the operation at around 100 K. These results indicate that Cu-Al-Mn SMAs are potential cryogenic actuators with high actuation stress and strain that would contribute to the development of low temperature technologies in various fields including space astronomy, superconductivity, and liquefied gas industry. Conventional actuators cannot exhibit high performance at cryogenic temperatures. Shunsuke Sato and colleagues demonstrated that Cu-Al-Mn shape memory alloys can provide high work output from 50 K, showing their potential for use in low-temperature technology fields.

We present a 152 ks XRISM/Resolve observation of the persistently accreting Z source GX 340+0. Simultaneous observations also occurred with NuSTAR and NICER for 22.47 ks and 2.7 ks, respectively. The source covered the normal branch to the flaring branching during the observations. The data from all three missions were modeled concurrently for each spectral branch. The superior energy resolution of XRISM/Resolve reveals structure within the iron emission line complex regardless of spectral state. We model the reprocessed Fe K line with a reflection model tailored for thermal illumination of the accretion disk by a neutron star. The currently available model encompasses the broad components, but narrow emission features remain at the similar to 5% level. These remaining features may be described by the presence of an ionized plasma in the system as has been observed in the Z source Cygnus X-2, but subsequent updates to the reflection model code may be able to explain these features.

An unusual orbital element clustering of Kuiper belt objects (KBOs) has been observed. The most promising dynamic solution is the presence of a giant planet in the outer Solar system, Planet Nine. However, due to its extreme distance, intensive searches in optical have not been successful. We aim to find Planet Nine in the far-infrared, where it has the peak of the black body radiation, using the most sensitive all-sky far-infrared survey to date, AKARI . In contrast to optical searches, where the energy of reflected sunlight decreases by d 4 , thermal radiation in the infrared decreases with the square of the heliocentric distance d 2 . We search for moving objects in the AKARI Single Scan Detection List. We select sources from a promising region suggested by an N-body simulation from Millholland and Laughlin 2017: 30° < R.A. < 50° and –20° < Dec. < 20°. Known sources are excluded by cross-matching AKARI sources with 9 optical and infrared catalogues. Furthermore, we select sources with small background strength to avoid sources in the cirrus. Since Planet Nine is stationary in a timescale of hours but moves on a monthly scale, our primary strategy is to select slowly moving objects that are stationary in 24 hours but not in six months, using multiple single scans by AKARI. The selected slowly moving AKARI sources are scrutinised for potential contamination from cosmic rays. Our analysis reveals two possible Planet Nine candidates whose positions and flux are within the theoretical prediction ranges. These candidates warrant further investigation through follow-up observations to confirm the existence and properties of Planet Nine.

We present the first high-resolution XRISM spectrum of the neutron star low-mass X-ray binary GX 340+0, revealing unprecedented detail in its emission and absorption features. The spectrum reveals a rich and complex Fe XXV Heα line profile and a P-Cygni profile from Ca XX. We use the state-of-the-art spectral synthesis code Cloudy to model the emission and absorption features in detail. Our analysis reveals multi-ionization and multi-velocity structures, where the combination of broad (∼ 800 km/s) and narrow (∼ 360 km/s) line components, along with rest-frame and blueshifted emission and absorption lines, accounts for the observed line profile complexity. We identify a modest ∼ 2735 km/s accretion disk wind exhibiting both absorption and emission features. We also detect a relativistic reflection feature in the spectrum, which we model using relxillNS - specifically designed to characterize X-ray reprocessing in accretion disks around neutron stars. Furthermore, we examine the detailed physics of the Fe XXV Heα complex, focusing on the forbidden-to-resonance line ratio under the influence of continuum pumping and optical depth effects.

We are promoting a design of high-dispersion immersion grating for the high-resolution mid-infrared spectrometer (HRS, resolving power R equivalent to lambda/Delta lambda approximate to 30,000 at lambda = 10 to 18 mu m), which will be mounted onboard the next-generation infrared space telescope, Galaxy Reionization EXplorer and PLanetary Universe Spectrometer (GREX-PLUS). Compared with conventional diffraction gratings, immersion gratings reduce optical path length and the collimated mean diameter by a factor of 1/n, where n is the refractive index of the immersion material. Achieving such high spectral dispersion requires the use of highly transparent optical materials characterized by low absorption coefficients (alpha <= 0.01 cm(-1)) at the instrument's operating temperature (T approximate to 20 K), to reduce instrumental background radiation. Cadmium Zinc Telluride (CdZnTe) has been identified as a promising candidate material, not only due to its low absorption coefficient but also due to its machinability. Recent transmittance measurements conducted by Maeshima et al. at cryogenic temperatures indicated that high-resistivity CdZnTe exhibits superior optical properties suitable for immersion gratings, in contrast to low-resistivity CdZnTe. To precisely determine the absorption coefficient of high-resistivity CdZnTe, we developed a cryogenic common-path double-beam transmittance measurement system with an original design. Utilizing a filament lamp placed within the vacuum chamber, combined with three bandpass filters, we achieved transmittance measurement precision better than 0.06% across a continuous temperature range from room temperature to 5.7 K. Employing recently published refractive index data, we derived absorption coefficients (alpha) at T approximate to 20 K of 0.00049, 0.00333, and 0.00251 cm(-1) for wavelengths of 10.6, 15.1, and 19.0 mu m, respectively. Notably, the absorption coefficient for high-resistivity CdZnTe exhibited minimal temperature dependence and remained consistently below 0.01 cm(-1), satisfying the stringent optical requirements for GREX-PLUS HRS. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Using data from the MIRIS Pa α Galactic Plane Survey (MIPAPS), we present a Pa α 1.87 μ m line image of the entire Galactic plane within the latitude range of −3° ≲ b ≲ +3°, revealing numerous Pa α features. Based on the MIPAPS Pa α image and the Wide-field Infrared Survey Explorer (WISE) H ii region catalog, we compile a catalog of 1489 Pa α emission-line sources in the Galactic plane within 90° ≤ ℓ ≤ 330°. By comparing our Pa α images with H α images constructed from the IPHAS and VPHAS+ survey data, we demonstrate the advantages of Pa α line observations. We identify 902 Pa α sources associated with H ii regions, and newly confirm 619 H ii region candidates as definitive H ii regions through Pa α or H α detections. We also identify 261 extended and 326 pointlike Pa α sources not included in the WISE catalog, most of which have H α counterparts in the IPHAS or VPHAS+ images. A search of the SIMBAD database indicates that these sources originate from diverse object types. By measuring Pa α and H α fluxes, we estimate the E ( B − V ) color excesses derived from extended emissions for 138 Pa α sources, showing good agreement with values obtained from spectrophotometry of ionizing stars in previous studies. Furthermore, we calculate total Lyman continuum luminosities for 42 Pa α sources, providing constraints on the distances to H ii regions and the spectral types of their ionizing stars. These results highlight the scientific potential of Pa α line observations and the benefits of combining multiple hydrogen recombination lines in exploring ionized regions.