EVOLUTION OF LUMINOUS INFRARED GALAXIES REVEALED BY NEAR-INFRARED MULTI-BAND IMAGING OF THEIR HOSTS

Oi, Nagisa,Imanishi, Masatoshi The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

We present the result of our near infrared J- (${\lambda}=1.25{\mu}m$), H- (${\lambda}=1.63{\mu}m$), and $K_s$-band (${\lambda}=2.14{\mu}m$) imaging of ultraluminous ($L_{IR}$ > $10^{12}L_{\odot}$) and luminous ($L_{IR}=10^{11-12}L_{\odot}$) infrared galaxies (ULIRGs and LIRGs), to investigate their relationship through properties of their host galaxies. We find that (1) for single-nucleus ULIRGs and LIRGs, their spheroidal host galaxies have similar properties, but ULIRGs display a substantially higher level of nuclear activity than LIRGs, suggesting that their infrared luminosity difference comes primarily from the different level of current nuclear activity. We infer that LIRGs and ULIRGs have similar progenitor galaxies, follow similar evolutionary processes, and may evolve into optically-selected QSOs. (2) Largely-separated multiple-nuclei ULIRGs have significantly brighter host galaxies than single-nucleus ULIRGs and LIRGs in $K_s$-band, indicating that multiple-nuclei ULIRGs have a bias towards mergers of intrinsically large progenitor galaxies, in order to produce high infrared luminosity ($L_{IR}$ > $10^{12}L_{\odot}$) even at the early merging stage. (3) We derive dust extinction of host galaxies of ULIRGs and LIRGs to be $A_V$ ~ 14 mag in the optical or equivalently $A_K$ ~ 0.8 mag in the near-infrared $K_s$-band, based on the comparison of host galaxy's luminosities in the J-, H-, and $K_s$-bands.

INFRARED – X-RAY CONNECTION IN NEARBY ACTIVE GALACTIC NUCLEI; AKARI AND MAXI RESULTS

Naoki Isobe,TAKAONAKAGAWA,Kenichi Yano,Shunsuke Baba,SHINKI OYABU,Yoshiki Toba,Yoshihiro Ueda,Taiki Kawamuro 한국천문학회 2017 天文學論叢 Vol.32 No.1

Combining the AKARI Point Source Catalog andthe 37-month Monitor of All-sky X-ray Image (MAXI) catalog,the infrared and X-ray properties of nearby active galactic nucleiwere investigated. The 37-month MAXI catalog tabulates 100 nearby Seyfert galaxies,73 of which are categorized into Seyfert I galaxies. Among these Seyfert galaxies,69 ones were found to have an AKARI infrared counterpart. For the Seyfert I galaxies in this sample,a well-known correlation was found between the infrared and X-ray luminosities. However, the observed X-ray luminosity of the Seyfert II galaxiestends to be lower for the infrared luminosity than the Seyfert I galaxies. This suggests thatthe X-ray absorption is significant in the Seyfert II galaxies. The Seyfert II galaxies seem to havea bimodal distribution of the IR color between $18~\mu$m and $90~\mu$m. Especially, a large fraction of the Seyfert II galaxiesexhibits a redder IR color than the Seyfert I galaxies. A possible origin of the redder IR color is briefly discussed,in relation to the star formation activity in the host galaxy,and to the X-ray absorption.

Evolution of dust temperature of galaxies through cosmic time as seen by <i>Herschel</i>^★

Hwang, H. S.,Elbaz, D.,Magdis, G.,Daddi, E.,Symeonidis, M.,Altieri, B.,Amblard, A.,Andreani, P.,Arumugam, V.,Auld, R.,Aussel, H.,Babbedge, T.,Berta, S.,Blain, A.,Bock, J.,Bongiovanni, A.,Boselli, A.,B Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.1

<P>ABSTRACT</P><P>We study the dust properties of galaxies in the redshift range 0.1 ≲<I>z</I>≲ 2.8 observed by the <I>Herschel Space Observatory</I> in the field of the Great Observatories Origins Deep Survey-North as part of the PACS Extragalactic Probe (PEP) and <I>Herschel</I> Multi-tiered Extragalactic Survey (HerMES) key programmes. Infrared (IR) luminosity (<I>L</I><SUB>IR</SUB>) and dust temperature (<I>T</I><SUB>dust</SUB>) of galaxies are derived from the spectral energy distribution fit of the far-IR (FIR) flux densities obtained with the PACS and SPIRE instruments onboard <I>Herschel</I>. As a reference sample, we also obtain IR luminosities and dust temperatures of local galaxies at <I>z</I> < 0.1 using <I>AKARI</I> and <I>IRAS</I> data in the field of the Sloan Digital Sky Survey. We compare the <I>L</I><SUB>IR</SUB>–<I>T</I><SUB>dust</SUB> relation between the two samples and find that the median <I>T</I><SUB>dust</SUB> of <I>Herschel</I>-selected galaxies at <I>z</I>≳ 0.5 with <I>L</I><SUB>IR</SUB>≳ 5 × 10<SUP>10</SUP> L<SUB>⊙</SUB> appears to be 2–5 K colder than that of <I>AKARI</I>-selected local galaxies with similar luminosities, and the dispersion in <I>T</I><SUB>dust</SUB> for high-<I>z</I> galaxies increases with <I>L</I><SUB>IR</SUB> due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the <I>L</I><SUB>IR</SUB>−<I>T</I><SUB>dust</SUB> relation can bridge the gap between local star-forming galaxies and high-<I>z</I> submillimetre galaxies (SMGs). We also find that three SMGs with very low <I>T</I><SUB>dust</SUB> (≲20 K) covered in this study have close neighbouring sources with similar 24-μm brightness, which could lead to an overestimation of FIR/(sub)millimetre fluxes of the SMGs.</P>

OBSERVATIONS OF STAR FORMATION INDUCED BY GALAXY-GALAXY AND GALAXY-INTERGALACTIC MEDIUM INTERACTIONS WITH AKARI

Suzuki, T.,Kaneda, H.,Onaka, T. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

Nearby spiral galaxies M101 and M81 are considered to have undergone a galaxy-galaxy interaction. M101 has experienced HI gas infall due to the interaction. With AKARI far-infrared (IR) photometric observations, we found regions with enhanced star forming activity, which are spatially close to regions affected by the interaction. In addition, the relation between the star formation rate (SFR) and the gas content for such regions shows a significant difference from typical spiral arm regions. We discuss possible explanations for star formation processes on a kiloparsec scale and the association with interaction-triggered star formation. We also observed the compact group of galaxies Stephan's Quintet (SQ) with the AKARI Far-infrared Surveyor (FIS). The SQ shows diffuse intergalactic medium (IGM) due to multiple collisions between the member galaxies and the IGM. The intruder galaxy NGC 7318b is currently colliding with the IGM and causes a large-scale shock. The 160 micron image clearly shows the structure along the shock ridge as seen in warm molecular hydrogen line emission and X-ray emission. The far-IR emission from the shocked region comes from the luminous [CII]$158{\mu}m$ line and cold dust (~ 20 K) that coexist with molecular hydrogen gas. Survival of dust grains is indispensable to form molecular hydrogen gas within the collision age (~ 5 Myr). At the stage of the dusty IGM environment, [CII] and $H_2$ lines rather than X-ray emission are powerful cooling channels to release the collision energy.

ENVIRONMENTAL DEPENDENCE OF STAR FORMATION AND GALAXY TRANSFORMATION IN MERGING GALAXY CLUSTER ABELL 2255: AKARI'S POINT OF VIEW

Shim, Hyunjin The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

We investigate the role of galaxy environment in the evolution of individual galaxies through the AKARI observations of the merging galaxy cluster A2255. MIR diagnostics using N3-S11 colors are adopted to select star-forming galaxies and galaxies in transition between star-forming galaxies and quiescent galaxies. We do not find particular enhancement of star formation rates as a function of galaxy environment, reflected in cluster-centric distance and local surface density of galaxies. Instead, the locations of intermediate MIR-excess galaxies (-1.2 < N3 - S11 < 0.2) show that star-forming galaxies are transformed into passive galaxies in the substructures of A2255, where the local surface density of galaxies is relatively high.

SED DECOMPOSITION OF INFRARED-LUMINOUS GALAXIES

Lee, Jong Chul The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

We select infrared-luminous galaxies by cross-matching the SDSS spectroscopic sample of galaxies with the WISE all-sky survey catalog. Based on photometric data points covering from SDSS u-band to WISE $22{\mu}m$, their spectral energy distributions (SEDs) are separated into AGN, elliptical, spiral, and irregular galaxy components. The derived luminosities of spiral galaxy and AGN are well correlated with $H{\alpha}$ and [OIII] line luminosities, respectively. Most galaxies are dominated by young stellar populations even for optical AGNs, but at least 10% of optical non-AGNs appear to harbor buried AGNs. The AGN contribution increases dramatically with the total luminosity. These results show that the SED decomposition is successful and is useful to understand the true nature of dusty galaxies.

DETECTION OF Hα EMISSION FROM z>3.5 GALAXIES WITH AKARI-FUHYU NIR SPECTROSCOPY

Sedgwick, Chris,Serjeant, Stephen,Pearson, Chris,Takagi, Toshinobu,Matsuhara, Hideo,Wada, Takehiko,Lee, Hyung Mok,Im, Myungshin,Jeong, Woong-Seob,Oyabu, Shinki,White, Glenn J. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

This paper presents $H{\alpha}$ emission line detections for four galaxies at z > 3.5 made with AKARI as part of the FUHYU mission program. These are the highest-redshift $H{\alpha}$ detections to date in star-forming galaxies. AKARI's unique near-infrared spectroscopic capability has made these detections possible. For two of these galaxies, this represents the first evidence of their redshifts and confirms their physical association with a companion radio galaxy. The star formation rates (SFRs) estimated from the $H{\alpha}$ lines under-predict the SFRs estimated from their far-infrared luminosities by a factor of ~ 2 - 3. We have also detected broad $H{\alpha}$ components in the two radio galaxies which indicate the presence of quasars.

The ultraluminous and hyperluminous infrared galaxies in the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey and 6dF Galaxy Survey

Hwang, Ho Seong,Serjeant, Stephen,Lee, Myung Gyoon,Lee, Kang Hwan,White, Glenn J. Blackwell Publishing Ltd 2007 Monthly notices of the Royal Astronomical Society Vol.375 No.1

<P>ABSTRACT</P><P>We present a result of cross-correlating the <I>Infrared Astronomical Satellite</I> Faint Source Catalogue with the spectroscopic catalogues of galaxies in the Fourth Data Release of the Sloan Digital Sky Survey, the Final Data Release of the 2dF Galaxy Redshift Survey (2dFGRS) and the Second Data Release of the 6dF Galaxy Survey. We have identified 324 ultraluminous infrared galaxies (ULIRGs) including 190 newly discovered ULIRGs, and two hyperluminous infrared galaxies. Adding these new ULIRGs, we increase the number of known ULIRGs by about 30 per cent. The reliability of the cross-correlation is estimated using the likelihood ratio method. The incompleteness of our sample introduced by the identification procedure in this study is estimated to be about 5 per cent. Our sample covers the redshift range of <I>z</I>= 0.037–0.517 with a median redshift of <IMG SRC='http://mnras.oxfordjournals.org/content/375/1/115/embed/inline-graphic-1.gif'/>, which is larger than that <IMG SRC='http://mnras.oxfordjournals.org/content/375/1/115/embed/inline-graphic-2.gif'/> of the sample of previously known ULIRGs.</P>

Photometric redshift accuracy in <i>AKARI</i> deep surveys

Negrello, M.,Serjeant, S.,Pearson, C.,Takagi, T.,Efstathiou, A.,Goto, T.,Burgarella, D.,Jeong, W.-S.,Im, M.,Lee, H. M.,Matsuhara, H.,Oyabu, S.,Wada, T.,White, G. Blackwell Publishing Ltd 2009 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.394 No.1

<P>ABSTRACT</P><P>We investigate the photometric redshift accuracy achievable with the <I>AKARI</I> infrared data in deep multiband surveys, such as in the North Ecliptic Pole field. We demonstrate that the passage of redshifted polycyclic aromatic hydrocarbons (PAH) and silicate features into the mid-infrared wavelength window covered by <I>AKARI</I> is a valuable means to recover the redshifts of starburst galaxies. To this end, we have collected a sample of ∼60 galaxies drawn from the Great Observatories Origins Deep Survey-North Field with spectroscopic redshift 0.5 ≲<I>z</I><SUB>spec</SUB>≲ 1.5 and photometry from 3.6 to 24 μm, provided by the <I>Spitzer</I>, <I>Infrared Space Observatory</I> and <I>AKARI</I> satellites. The infrared spectra are fitted using synthetic galaxy spectral energy distributions which account for starburst and active nuclei emission. For ∼90 per cent of the sources in our sample, the redshift is recovered with an accuracy |<I>z</I><SUB>phot</SUB>−<I>z</I><SUB>spec</SUB>|/(1 +<I>z</I><SUB>spec</SUB>) ≲ 10 per cent. A similar analysis performed on a set of simulated spectra shows that the <I>AKARI</I> infrared data alone can provide photometric redshifts accurate to |<I>z</I><SUB>phot</SUB>−<I>z</I><SUB>spec</SUB>|/(1 +<I>z</I><SUB>spec</SUB>) ∼ 10 per cent (1σ) at <I>z</I>≲ 2. At higher redshifts, the PAH features are shifted outside the wavelength range covered by <I>AKARI</I> and the photo-<I>z</I> estimates rely on the less prominent 1.6 μm stellar bump; the accuracy achievable in this case on (1 +<I>z</I>) is ∼10–15 per cent, provided that the active galactic nuclei contribution to the infrared emission is subdominant. Our technique is no more prone to redshift aliasing than optical-ultraviolet photo-<I>z</I>, and it may be possible to reduce this aliasing further with the addition of submillimetre and/or radio data.</P>

PROPERTIES OF DUST IN VARIOUS ENVIRONMENTS OF NEARBY GALAXIES

HIDEHIRO KANEDA,Takuma Kokusho,Rika Yamada,DAISUKE ISHIHARA,SHINKI OYABU,TORU KONDO,MITSUYOSHI YAMAGISHI,Akiko Yasuda,TAKASHI ONAKA,Toyoaki Suzuki 한국천문학회 2017 天文學論叢 Vol.32 No.1

We have performed systematic studies of the properties of dust in various environments of nearby galaxies with AKARI. The unique capabilities of AKARI, such as near-infrared (near-IR) spectroscopy combined with all-sky coverage in the mid- and far-IR, enable us to study processing of dust, particularly carbonaceous grains includings polycyclic aromatic hydrocarbons (PAHs), for unbiased samples of nearby galaxies. In this paper, we first review our recent results on individual galaxies, highlighting the uniqueness of AKARI data for studies of nearby galaxies. Then we present results of our systematic studies on nearby starburst and early-type galaxies. From the former study based on the near-IR spectroscopy and mid-IR all-sky survey data, we find that the properties of PAHs change systematically from IR galaxies to ultra-luminous IR galaxies, depending on the IR luminosity of a galaxy or galaxy population. From the latter study based on the mid- and far-IR all-sky survey data, we find that there is a global correlation between the amounts of dust and old stars in early-type galaxies, giving an observational constraint on the origin of the dust.