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 level
s (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 the results of our systematic infrared 2.5-5 micron spectroscopy of 60 luminous infrared galaxies (LIRGs) with infrared luminosities L(IR) = 10^11-12 Lsun, and 54 ultraluminous infrared galaxies (ULIRGs) with L(IR) > 10^12 Lsun, using AKAR
I IRC. AKARI IRC slit-less spectroscopy allows us to probe the full range of emission from these galaxies, including spatially extended components. The 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission features, hydrogen recombination emission lines, and various absorption features are detected and used to investigate the properties of these galaxies. Because of the relatively small effect of dust extinction in the infrared range, quantitative discussion of these dusty galaxy populations is possible. For sources with clearly detectable Br beta (2.63 micron) and Br alpha (4.05 micron) emission lines, the flux ratios are found to be similar to that predicted by case B theory. Starburst luminosities are estimated from both 3.3 micron PAH and Br alpha emission, which roughly agree with each other. In addition to the detected starburst activity, a significant fraction of the observed sources display signatures of obscured AGNs, such as low PAH equivalent widths, large optical depths of dust absorption features, and red continuum emission. The energetic importance of optically elusive buried AGNs in optically non-Seyfert galaxies tends to increase with increasing galaxy infrared luminosity, from LIRGs to ULIRGs.
We present the characterization and calibration of the Slow-Scan observation mode of the Far-Infrared Surveyor (FIS) onboard the AKARI satellite. The FIS, one of the two focal-plane instruments on AKARI, has four photometric bands between 50--180 um
with two types of Ge:Ga array detectors. In addition to the All-Sky Survey, FIS has also taken detailed far-infrared images of selected targets by using the Slow-Scan mode. The sensitivity of the Slow-Scan mode is one to two orders of magnitude better than that of the All-Sky Survey, because the exposure time on a targeted source is much longer. The point spread functions (PSFs) were obtained by observing several bright point-like objects such as asteroids, stars, and galaxies. The derived full widths at the half maximum (FWHMs) are ~30 for the two shorter wavelength bands and ~40 for the two longer wavelength bands, being consistent with those expected by the optical simulation, although a certain amount of excess is seen in the tails of the PSFs. The flux calibration has been performed by the observations of well-established photometric calibration standards (asteroids and stars) in a wide range of fluxes. After establishing the method of aperture photometry, the photometric accuracy for point-sources is better than +-15% in all of the bands expect for the longest wavelength.
We report initial results of far-infrared observations of the Lockman hole with Far-Infrared Surveyor (FIS) onboard the AKARI infrared satellite. On the basis of slow scan observations of a 0.6 deg x 1.2 deg contiguous area, we obtained source number
counts at 65, 90 and 140 um down to 77, 26 and 194 mJy (3 sigma), respectively. The counts at 65 and 140 um show good agreement with the Spitzer results. However, our 90 um counts are clearly lower than the predicted counts by recent evolutionary models that fit the Spitzer counts in all the MIPS bands. Our 90 um counts above 26 mJy account for about 7% of the cosmic background. These results provide strong constraints on the evolutionary scenario and suggest that the current models may require modifications.
