We present the first measurement of the angular two-point correlation function for AKARI 90μm point sources, detected outside of the Milky Way plane and selected as candidates for extragalactic sources. This is the first measurement of the large-scale angular clustering of galaxies selected in the far-infrared after IRAS. We find a positive clustering signal in both hemispheres extending up to ~ 40 degrees, without any significant fluctuations at larger scales. The observed correlation function is well fitted by a power law function. However, southern galaxies seem to be more strongly clustered than northern ones and the difference is statistically significant. The reason for this difference - technical or physical - is still to be found.

It is a long known fact that there exists a tight correlation between far-infrared and radio emission both for galaxies hosting active galactic nuclei and for star forming galaxies. We probe the radio - infrared correlation for a sample of extragalactic sources constructed by the cross-correlation of the AKARI/IRC All-Sky Survey Point Source Catalogue, the AKARI/FIS All-Sky Survey Bright Source Catalogue, and the NRAO VLA Sky Survey. Additionally, all objects of our sample were identified as galaxies in NED and SIMBAD databases, and a part of them is known to host active galactic nuclei (AGNs). After remeasuring all the fluxes, in order to avoid small aperture effects, we compare the ratio of radio to infrared emission from different types of extragalactic sources, and discuss the FIR/radio correlation as seen by AKARI and make a comparison to the previous results obtained thanks to IRAS.

We will report our recent study on the properties of more than 1,600 galaxies detected by the AKARI All-Sky Survey with physical quantities based on optical and 21-cm observations, to understand the physics determining the infrared spectral energy distribution (Totani et al., 2011). We discover a tight linear correlation for normal star-forming galaxies between the radiation field strength of dust heating (corresponding to dust temperature) and the galactic-scale infrared radiation field, LTIR/R2 . This is the tightest correlation of dust temperature ever known, and the dispersion along the mean relation is 13% in dust temperature. This relation can be explained physically by a thin layer of heating sources embedded in a thicker, optically-thick dust screen. We also find that the number of galaxies sharply drops when galaxies become optically thin against dust-heating radiation, indicating that a feedback process to galaxy formation (e.g., by the photoelectric heating) is working when dust-heating radiation is not self-shielded on a galactic scale. We discuss implications from these findings for the MHI -size relation, the Kennicutt-Schmidt relation, and galaxy formation in the cosmological context.

A sample of nearby galaxies was built from the AKARI/FIS all sky survey cross-correlated with the SDSS and GALEX surveys. The spectral energy distributions from 0.15 to 160 microns of these galaxies are analysed to study dust attenuation and star formation properties. The calibrations of the amount of dust attenuation as a function of the IR-to-UV flux ratio and the FUV-NUV colour are re-investigated: the former one is confirmed to be robust and accurate whereas the use of the FUV-NUV colour to measure dust attenuation is found highly uncertain. The current star formation rate given by the SED fitting process is compared to that directly obtained from the UV and total IR luminosities. It leads to an accurate estimate of dust heating by old stars. We emphasize the importance of such a sample as a reference for IR selected star forming galaxies in the nearby universe.

We established a separation scheme to distinguish galaxies from stars with the aid of AKARI/FIS color-color (CC) diagrams. In all the combinations of CC diagrams we can distinguish two separate clouds. It was shown that in all cases one of them contains more than 95% of galaxies and the other one, in most cases, consists in more than 80% of stars (Pollo et al., 2010). Currently we are looking into more detailed classifications. We are especially interested in separating different morphological types of galaxies, mainly within spiral galaxies. Moreover, we study the properties of infrared galaxies.

Understanding the birth and evolution of galaxies, and the history of star formation in them, is one of the most important problems in astronomy. Using the data from the AKARI IRC survey of the Large Magellanic Cloud at 3.2, 7, 11, 15, and 24 μm , we have constructed a multi-wavelength catalog containing data from the cross-correlation with a number of other databases at different wavelengths. We present the first approach with a Support Vector Machine (SVM)-based method to separate different classes of stars in LMC in the color-color and color-magnitude diagrams.

We present the method of star/galaxy separation based on the support vector machines (SVM) in the data from the AKARI North Ecliptic Pole (NEP) Deep survey collected through nine AKARI / IRC bands from 2 to 24 μm , with a classification accuracy of 93 %.

We present the results of Spectral Energy Distribution (SED) fitting of far-infrared galaxies detected in the AKARI Deep Field-South (ADF-S) Survey and discuss their physical properties. Additionally, we perform a comparison between photometric redshifts estimated using only optical and both optical and infrared data. We conclude that our sample consists mostly of nearby galaxies rich in dust and young stars. We observe an improvement in the estimation of photometric redshifts when the IR data are included, comparing to a standard approach based mainly on the optical to UV photometry.