Tamami I. Mori

Observations of the near- to Mid-infrared Unidentified Emission Bands in the Interstellar Medium of the Large Magellanic Cloud

We present the results of near- to mid-infrared slit spectroscopic observations (2.55-13.4 {mu}m) of the diffuse emission toward nine positions in the Large Magellanic Cloud with the infrared camera on board AKARI. The target positions are selected to cover a wide range of the intensity of the incident radiation field. The unidentified infrared bands at 3.3, 6.2, 7.7, 8.6, and 11.3 {mu}m are detected toward all the targets and ionized gas signatures; hydrogen recombination lines and ionic forbidden lines are detected toward three of them. We classify the targets into two groups: those without the ionized gas signatures (Group A) and those with the ionized signatures (Group B). Group A includes molecular clouds and photodissociation regions, whereas Group B consists of H II regions. In Group A, the band ratios of I{sub 3.3{mu}m}/I{sub 11.3{mu}m}, I{sub 6.2{mu}m}/I{sub 11.3{mu}m}, I{sub 7.7{mu}m}/I{sub 11.3{mu}m}, and I{sub 8.6{mu}m}/I{sub 11.3{mu}m} show positive correlation with the IRAS and AKARI colors, but those of Group B do not follow the correlation. We discuss the results in terms of the polycyclic aromatic hydrocarbon (PAH) model and attribute the difference to the destruction of small PAHs and an increase in the recombination due to the high electron density in Group morexa0» B. In the present study, the 3.3 {mu}m band provides crucial information on the size distribution and/or the excitation conditions of PAHs and plays a key role in the distinction of Group A from B. The results suggest the possibility of the diagram of I{sub 3.3{mu}m}/I{sub 11.3{mu}m} versus I{sub 7.7{mu}m}/I{sub 11.3{mu}m} as an efficient diagnostic tool to infer the physical conditions of the interstellar medium. «xa0less

OBSERVATIONAL STUDIES ON THE NEAR-INFRARED UNIDENTIFIED EMISSION BANDS IN GALACTIC H II REGIONS

Using a large collection of near-infrared spectra (2.5-5.4 μm) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a directors time program. In addition to the well known 3.3-3.6 μm features, most spectra show a relatively weak emission feature at 5.22 μm with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 μm band (previously reported). By careful analysis, we find good correlations between the 5.25 μm band and both the aromatic hydrocarbon feature at 3.3 μm and the aliphatic hydrocarbon features at around 3.4-3.6 μm. The present results give us convincing evidence that the astronomical 5.25 μm band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I {sub 3.4-3.6} {sub μm}/I {sub 3.3} {sub μm} decreases against the ratio of the 3.7 μm continuum intensity to the 3.3 μm band, I {sub cont,} {sub 3.7} {sub μm}/I {sub 3.3} {sub μm}, which is an indicator of themorexa0» ionization fraction of PAHs. The midinfrared color of I {sub 9} {sub μm}/I {sub 18} {sub μm} also declines steeply against the ratio of the hydrogen recombination line Brα at 4.05 μm to the 3.3 μm band, I {sub Brα}/I {sub 3.3} {sub μm}. These facts indicate possible dust processing inside or at the boundary of ionized gas.«xa0less

Search for the Infrared Emission Features from Deuterated Interstellar Polycyclic Aromatic Hydrocarbons

We report the results of a search for emission features from interstellar deuterated polycyclic aromatic hydrocarbons (PAHs) in the 4xa0μm region with the Infrared Camera (IRC) on board AKARI. No significant excess emission is seen in 4.3-4.7xa0μm in the spectra toward the Orion Bar and M17 after the subtraction of line emission from the ionized gas. A small excess of emission remains at around 4.4 and 4.65xa0μm, but the ratio of their intensity to that of the band emission from PAHs at 3.3-3.5xa0μm is estimated as 2%-3%. This is an order of magnitude smaller than the values previously reported and also those predicted by the model of deuterium depletion onto PAHs. Since the subtraction of the ionized gas emission introduces an uncertainty, the deuterated PAH features are also searched for in the reflection nebula GN 18.14.0, which does not show emission lines from ionized gas. We obtain a similar result that excess emission in the 4xa0μm region, if present, is about 2% of the PAH band emission in the 3xa0μm region. The present study does not find evidence for the presence of the large amount of deuterated PAHs that the depletion model predicts. The results are discussed in the context of deuterium depletion in the interstellar medium.

Near- to mid-infrared imaging and spectroscopy of two buried AGNs of the nearby merging galaxy NGC 6240 with Subaru/IRCS+AO and GTC/CanariCam

We report near-infrared K, L, and M band imaging observations of the nearby merging galaxy NGC 6240 with the Infrared Camera and Spectrograph on the Subaru telescope. The observations were performed with the assistance of the Subaru Adaptive Optics System, and the achieved spatial resolutions were around 0.10--0.20

Summary of observations of the infrared camera (IRC) onboard AKARI

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Deuterated polycyclic aromatic hydrocarbons: Revisited

. We also obtained new mid-infrared imaging in the Si-2 filter band (8.7

UNUSUAL CARBONACEOUS DUST DISTRIBUTION IN PN G095.2+00.7*

mu

Investigation of PAHs in galactic planetary nebulae with the AKARI/IRC and the Spitzer/IRS

m) and N-band (7.5--13

AKARI NEAR-INFRARED SPECTROSCOPY OF THE EXTENDED GREEN OBJECT G318.05+0.09: DETECTION OF CO FUNDAMENTAL RO-VIBRATIONAL EMISSION

mu

Near-infrared views of dust in planetary nebulae: AKARI/IRC NIR spectral atlas of Galactic PNe

m) spectroscopy of this galaxy with the CanariCam on the Gran Telescopio Canarias with a spatial resolution of 0.4--0.5