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Register a new userAKARI near-infrared spectroscopy of the extended green object G318.05+0.09: Detection of CO fundamental ro-vibrational emission
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We present the results of near-infrared (2.5--5.4um) long-slit spectroscopy of the extended green object (EGO) G318.05+0.09 with AKARI. Two distinct sources are found in the slit. The brighter source has strong red continuum emission with H2O ice, CO2 ice, and CO gas and ice absorption features at 3.0, 4.25um, 4.67um, respectively, while the other greenish object shows peculiar emission that has double peaks at around 4.5 and 4.7um. The former source is located close to the ultra compact HII region IRAS 14498-5856 and is identified as an embedded massive young stellar object. The spectrum of the latter source can be interpreted by blue-shifted (-3000 ~ -6000km/s) optically-thin emission of the fundamental ro-vibrational transitions (v=1-0) of CO molecules with temperatures of 12000--3700K without noticeable H2 and HI emission. We discuss the nature of this source in terms of outflow associated with the young stellar object and supernova ejecta associated with a supernova remnant.
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We present high-resolution spectroscopy of gaseous CO absorption in the fundamental ro-vibrational band toward the heavily obscured active galactic nucleus (AGN) IRAS 08572+3915. We have detected absorption lines up to highly excited rotational levels (J<=17). The velocity profiles reveal three distinct components, the strongest and broadest (delta_v > 200 km s-1) of which is due to blueshifted (-160 km s-1) gas at a temperature of ~ 270 K absorbing at velocities as high as -400 km s-1. A much weaker but even warmer (~ 700 K) component, which is highly redshifted (+100 km s-1), is also detected, in addition to a cold (~ 20 K) component centered at the systemic velocity of the galaxy. On the assumption of local thermodynamic equilibrium, the column density of CO in the 270 K component is NCO ~ 4.5 x 10^18 cm-2, which in fully molecular gas corresponds to a H2 column density of NH2 ~ 2.5 x 10^22 cm-2. The thermal excitation of CO up to the observed high rotational levels requires a density greater than nc(H2) > 2 x 10^7 cm-3, implying that the thickness of the warm absorbing layer is extremely small (delta_d < 4 x 10-2 pc) even if it is highly clumped. The large column densities and high radial velocities associated with these warm components, as well as their temperatures, indicate that they originate in molecular clouds near the central engine of the AGN.
We present observations of ro-vibrational OH and CO emission from the Herbig Be star HD 100546. The emission from both molecules arises from the inner region of the disk extending from approximately 13 AU from the central star. The velocity profiles of the OH lines are narrower than the velocity profile of the [O I] 6300 Angstrom line indicating that the OH in the disk is not cospatial with the O I. This suggests that the inner optically thin region of the disk is largely devoid of molecular gas. Unlike the ro-vibrational CO emission lines, the OH lines are highly asymmetric. We show that the average CO and average OH line profiles can be fit with a model of a disk comprised of an eccentric inner wall and a circular outer disk. In this model, the vast majority of the OH flux (75%) originates from the inner wall, while the vast majority of the CO flux (65%) originates on the surface of the disk at radii greater than 13 AU. Eccentric inner disks are predicted by hydrodynamic simulations of circumstellar disks containing an embedded giant planet. We discuss the implications of such a disk geometry in light of models of planet disk tidal interactions and propose alternate explanations for the origin of the asymmetry.
HD 141569 is a Herbig Ae/Be star that straddles the boundary between the transition disks and debris disks. It is a low dust mass disk that reveals numerous structural elements (e.g. gaps and rings) that may point to young planets. It also exhibits a reservoir of CO gas observed at both millimeter and IR wavelengths. Previous observations (Goto et al. 2006) reported a possible asymmetry in the CO gas emission. Herein the IR ro-vibrational emission lines are analyzed and modeled both spectroscopically and spectroastrometrically. We find emission features from both 12CO and 13CO isotopologues heated to a temperature of approximately 200 K in the radial extent of 13 to 60 au. We do not see evidenceof the previously reported asymmetry in CO emission, our results being consistent with a Keplerian, axisymmetric emitting region. This raises the question of whether the emission profile may be evolving in time, possibly as a result of an orbiting feature in the inner disk such as a planet.
We present new far-infrared (FIR) images of the edge-on starburst galaxy NGC253 obtained with the Far-Infrared Surveyor (FIS) onboard AKARI at wavelengths of 90 um and 140 um. We have clearly detected FIR dust emission extended in the halo of the galaxy; there are two filamentary emission structures extending from the galactic disk up to 9 kpc in the northern and 6 kpc in the northwestern direction. From its spatial coincidence with the X-ray plasma outflow, the extended FIR emission is very likely to represent outflowing dust entrained by superwinds. The ratios of surface brightness at 90 um to that at 140 um suggest that the temperatures of the dust in the halo are getting higher in the regions far from the disk, implying that there exist extra dust heating sources in the halo of the galaxy.
Aims. We investigate the properties of hydrocarbon grains in the galactic superwind of M 82. Methods. With AKARI, we performed near-infrared (2.5 - 4.5 um) spectroscopic observations of 34 regions in M 82 including its northern and southern halos. Results. Many of the spectra show strong emission at 3.3 um due to polycyclic aromatic hydrocarbons (PAHs) and relatively weak features at 3.4 - 3.6 um due to aliphatic hydrocarbons. In particular, we clearly detect the PAH 3.3 um emission and the 3.4 - 3.6 um features in halo regions, which are located at a distance of 2 kpc away from the galactic center. We find that the ratios of the 3.4 - 3.6 um features to the 3.3 um feature intensity significantly increase with distance from the galactic center, while the ratios of the 3.3 um feature to the AKARI 7 um band intensity do not. Conclusions. Our results clearly confirm the presence of small PAHs even in a harsh environment of the halo of M 82. The results also reveal that the aliphatic hydrocarbons emitting the 3.4 - 3.6 um features are unusually abundant in the halo, suggesting that small carbonaceous grains are produced by shattering of larger grains in the galactic superwind.
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