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AKARI-SDSS-GALEX SURVEYS: SPECTRAL ENERGY DISTRIBUTIONS OF NEARBY GALAXIES
Buat, V.,Yuan, F.T.,Takeuchi, T.T.,Giovannoli, E.,Heinis, S. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
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.
NEP-AKARI: EVOLUTION WITH REDSHIFT OF DUST ATTENUATION IN 8 μm SELECTED GALAXIES
V. Buat,N. Oi,D. Burgarella,K. Malek,H. Matsuhara,K. Murata,S. Serjeant,T.T. Takeuchi,M. Malkan,C. Pearson,T. Wada 한국천문학회 2017 天文學論叢 Vol.32 No.1
We built a 8 $\mu$m selected sample of galaxies in the NEP-AKARI field by defining 4redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0.15 < z < 0.49,0.75 < z < 1.34, 1.34 < z < 1.7 and 1.7 < z < 2.05) . Our sample contains 4079 sources, 599 are securely detected with$Herschel$/PACS. Also adding ultraviolet (UV) data from $GALEX$, we fit the spectral energy distributions using the physically motivated codeCIGALE to extract the star formation rate, stellar mass, dustattenuation and the AGN contribution to the total infrared luminosity ($L_{\rm IR}$). We discuss the impact of the adoptedattenuation curve and that of the wavelength coverage to estimate these physical parameters. We focus on galaxies with a luminosity close the characteristic $L_{\rm IR}^*$ in the different redshift bins to studythe evolution with redshift of the dust attenuation in these galaxies.
Burgarella Denis,Boquien Mederic,Buat Veronique,Ciesla Laure,Rhoelly Yannick 한국천문학회 2017 天文學論叢 Vol.32 No.1
Modelling and fitting the spectral energy distribution (SED) of galaxies or regions of galaxies is one of the most useful methods available to the astronomer nowadays. By modelling the SEDs and comparing the models to the observations, we can collect important information on the physical processes at play in the formation and evolution of galaxies. The models allow to follow the evolution of the galaxies from their formation on. The versatility of code is crucial because of the diversity of galaxies. The analysis is only relevant and useful if the models can correctly reproduce this diversity now and across (as best as possible) all redshifts. On the other hand, the code needs to run fast to compare several million or tens of millions of models and to select the best (on a probabilistic basis) one that best resembles the observations. With this important point in mind, it seems logical that we should efficiently make use of the computer power available to the average astronomer. For instance, it seems difficult, today, to model and fit SEDs without a parallelized code. We present the new Python version of CIGALE SED fitting code and its characteristics. CIGALE comes in two main flavours: {\it CIGALE Classic} to fit SEDs and {\it CIGALE Model} to create spectra and SEDs of galaxies at all redshifts. The latest can potentially be used in conjunction with galaxy evolution models of galaxy formation and evolution such as semi-analytic ones.
STAR FORMATION RATE CALIBRATIONS FOR WISE LUMINOSITIES
Yuan, F.T.,Takeuchi, T.T,Buat, V.,Burgarella, D. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Starting from an infrared selected GALEX-SDSS-2MASS-AKARI sample of local star forming galaxies, we built mock samples from redshift 0 to 2.5 to investigate star formation rate (SFR) calibrations using WISE luminosities. We find W3 and W4 band fluxes can indicate SFRs with small scatters when the rest-frame wavelengths are longer than ${\sim}6{\mu}m$. When the wavelength becomes shorter, the observed luminosities are more tightly connected to the emission of old stellar populations than dust, therefore lose the reliability to trace the SFR. The current SFR calibrations are consistent with previous studies.
PROPERTIES OF DUST OBSCURED GALAXIES IN THE NEP-DEEP FIELD
Nagisa Oi,Hideo Matsuhara,CHRIS PEARSON,Veronique Buat,Denis Burgarella,Matt Malkan,Takamitsu Miyaji 한국천문학회 2017 天文學論叢 Vol.32 No.1
We selected 47 DOGs at z ~ 1.5 using optical $R$ (or $r^{'}$), AKARI 18 $\mu$m, and 24 $\mu$m color in the AKARI North Ecliptic Pole (NEP) Deep survey field. Using the colors among 3, 4, 7, and $9\mu$m, we classified them into 3 groups; bump DOGs (23 sources), power-law DOGs (16 sources), and unknown DOGs (8 sources). We built spectral energy distributions (SEDs) with optical to far-infrared photometric data and investigated their properties using SED fitting method. We found that AGN activity such as a AGN contribution to the infrared luminosity and a Chandra detection rate for bump and power-law DOGs are significantly different, while stellar component properties like a stellar mass and a star-formation rate are similar to each other. A specific star-formation rate range of power-law DOGs is slightly higher than that of bump DOGs with wide overlap. Herschel/PACS detection rates are almost the same between bump and power-law DOGs. On the other hand SPIRE detection rates show large differences between bump and power-law DOGs. These results might be explained by differences in dust temperatures. Both groups of DOGs host hot and/or warm dust (~ 50 Kelvin), and many bump DOGs contain cooler dust ($\hspace{0.3em}\raisebox{0.4ex}{$<$}\hspace{-0.75em}\raisebox{-.7ex}{$\sim$}\hspace{0.3em}$ 30 Kelvin).
FAR INFRARED GALAXIES IN AKARI'S EYE
Malek, K.,Pollo, A.,Takeuchi, T.T.,Giovannoli, E.,Buat, V.,Burgarella, D.,Malkan, M. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
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.