Survey of Near-infrared Diffuse Interstellar Bands in Y and J Bands. I. Newly Identified Bands

Abstract

We searched for diffuse interstellar bands (DIBs) in the 0.91 < λ < 1.33 μm region by analyzing the near-infrared (NIR) high-resolution (R = 20,000 and 28,000) spectra of 31 reddened early-type stars (0.04 < E(B − V) < 4.58) and an unreddened reference star. The spectra were collected using the WINERED spectrograph, which was mounted on the 1.3 m Araki telescope at Koyama Astronomical Observatory, Japan, in 2012–2016, and on the 3.58 m New Technology Telescope at La Silla Observatory, Chile, in 2017–2018. We detected 54 DIBs—25 of which are newly detected by this study—and eight DIB candidates. Using this updated list, the DIB distributions over a wide wavelength range, from optical to NIR, are investigated. The FWHM values of the NIR DIBs are found to be narrower than those of the optical DIBs, on average, which suggests that the DIBs at longer wavelengths tend to be caused by larger molecules. Assuming that the larger carriers are responsible for the DIBs at longer wavelengths, and have larger oscillator strengths, we found that the total column densities of the DIB carriers tend to decrease with increasing DIB wavelength. The candidate molecules and ions for the NIR DIBs are also discussed.

Iron Complexes as Potential Carriers of Diffuse Interstellar Bands: The Photodissociation Spectrum of Fe+(H2O) at Optical Wavelengths

“…Coupled cluster calculations were performed in Gaussian, 54 multireference calculations in Molpro. 55,56 We analyzed the sensitivity of electronic energies of sextet and quartet states to the active space size using MRCI calculations in active spaces from (7,6) to (9,11) and (7,11) and CASSCF calculations with active spaces from (7,11) to (7,16) and (9,15). While the energies of the lowest sextet states are reasonably converged already with the minimal active space of (7,6), the quartet states are deeply influenced by the size of the active space, notably, the 4 4 B 1 and 4 4 B 2 states in the experimental window.…”

“…They are ubiquitous not only toward reddened sight lines in the Milky Way but also toward sources in dust-harboring nearby galaxies − and even out to cosmological distances . About 600 DIBs have been detected over the past century, with the most recent detections being made in the near-infrared. , The focus on laboratory spectroscopy to find DIB carriers has been put on carbon compounds, mostly polycyclic aromatic hydrocarbons (PAHs), fueled by the identification of C 60 + as the only known DIB carrier to date. , The identification of DIBs in the near-infrared region, however, requires ever larger molecules to afford low-lying electronic transitions. As argued recently by Kappe et al, larger PAHs are difficult to form and tend to become more reactive with size, which reduces their overall abundance.…”

“… 6 About 600 DIBs have been detected over the past century, 7 with the most recent detections being made in the near-infrared. 8 , 9 The focus on laboratory spectroscopy to find DIB carriers has been put on carbon compounds, mostly polycyclic aromatic hydrocarbons (PAHs), fueled by the identification of C 60 + as the only known DIB carrier to date. 10 , 11 The identification of DIBs in the near-infrared region, however, requires ever larger molecules to afford low-lying electronic transitions.…”

WARP: The Data Reduction Pipeline for the WINERED Spectrograph

“…The high throughput and resolution of WINERED have advanced the observational studies of various astronomical objects: metallicities and chemical abundances of various types of stars (D'Orazi et al 2018;Kondo et al 2019;Jian et al 2020;Fukue et al 2021;Taniguchi et al 2021;Matsunaga et al 2022Matsunaga et al , 2023, the diffuse interstellar bands and interstellar molecules (Hamano et al 2019(Hamano et al , 2022, young stellar objects (Yasui et al 2019), AGN (Mizumoto et al 2024), luminous blue variable stars (Mizumoto et al 2018), quasars (Sameshima et al 2020) and comets (Shinnaka et al 2017).…”

A high-resolution study of near-IR diffuse interstellar bands, search for small-scale structure, time variability, and stellar features

“…Elyajouri et al (2017) confirmed several weak DIBs and found that the 1527 nm DIB is most abundant in diffuse interstellar clouds with low density and high ultraviolet radiation fields (known as σ-type clouds, with ζ-type clouds having opposite properties). Hamano et al (2022) looked at DIBs in the Y and J bands, postulating that DIBs at longer wavelengths are caused by larger molecules. Finally, Ebenbichler et al (2022) observed four stars at R = 100 000 with CRIRES to confirm 17 new DIBs and identify a possible 12 additional DIBs.…”