T. Ishigaki

Evolution of infrared luminosity functions of galaxies in the AKARI NEP-deep field - Revealing the cosmic star formation history hidden by dust

Aims. Dust-obscured star-formation increases with increasing intensity and increasing redshift. We aim to reveal the cosmic starformation history obscured by dust using deep infrared observation with AKARI. Methods. We constructed restframe 8 μm, 12 μm, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4128 infrared sources in the AKARI NEP-deep field. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24 μm) by the AKARI satellite allowed us to estimate restframe 8 μm and 12 μm luminosities without using a large extrapolation based on an SED fit, which was the largest uncertainty in previous work. Results. We find that all 8 μm (0.38 < z < 2.2), 12 μm (0.15 < z < 1.16), and TIR LFs (0.2 < z < 1.6) show continuous and strong evolution toward higher redshift. Our direct estimate of 8 μm LFs is useful since previous work often had to use a large extrapolation from the Spitzer 24 μm to 8 μm, where SED modeling is more difficult because of the PAH emissions. In terms of cosmic infrared luminosity density (Ω_(IR)), which was obtained by integrating analytic fits to the LFs, we find good agreement with previous work at z < 1.2. We find the ΩIR evolves as ∝(1 + z)^(4.4±1.0). When we separate contributions to Ω_(IR) by LIRGs and ULIRGs, we found more IR luminous sources are increasingly more important at higher redshift. We find that the ULIRG (LIRG) contribution increases by a factor of 10 (1.8) from z = 0.35 to z = 1.4.

Polycyclic aromatic hydrocarbon (PAH) luminous galaxies at z 1

Aims. The NEP-deep survey, an extragalactic AKARI survey towards the north ecliptic pole (NEP), provides a comprehensive wavelength coverage from 2 to 24 μm using all 9 photometric bands of the infrared camera (IRC). It allows us to photometrically identify galaxies whose mid-IR emission is clearly dominated by PAHs. Methods. We propose a single-colour selection method to identify such galaxies, using two mid-IR flux ratios at 11-to-7 μ ma nd 15-to-9 μm (PAH-to-continuum flux ratio in the rest frame), which are useful for identifying starburst galaxies at z ∼ 0.5 and 1, respectively. We perform a fitting of the spectral energy distributions (SEDs) from optical to mid-IR wavelengths, using an evolutionary starburst model with a proper treatment of radiative transfer (SBURT), in order to investigate their nature. Results. The SBURT model reproduces observed optical-to-mid-IR SEDs of more than a half of the PAH-selected galaxies. Based on the 8 μm luminosity, we find ultra luminous infrared galaxies (ULIRGs) among PAH-selected galaxies. Their PAH luminosity is higher than local ULIRGs with a similar luminosity, and the PAH-to-total IR luminosity ratio is consistent with that of less luminous starburst galaxies. They are a unique galaxy population at high redshifts, and we call these PAH-selected ULIRGs “PAH-luminous”Aims. Using an AKARI multi-wavelength mid-infrared (IR) survey, we identify luminous starburst galaxies at z >∼ 0.5 based on the PAH luminosity, and investigate the nature of these PAH-sel ect d starbursts. Methods. An extragalactic survey with AKARI towards the north eclipt ic pole (NEP), the NEP-Deep survey, is unique in terms of a comprehensive wavelength coverage from 2 to 24 μm using all 9 photometric bands of the InfraRed Camera (IRC). This survey allows us to photometrically identify galaxies whose mid-IR emiss ion is clearly dominated by PAHs. We propose a single colour s election method to identify such galaxies, using two mid-IR flux ratio s at 11-to-7μm and 15-to-9μm (PAH-to-continuum flux ratio in the rest-frame), which are useful to identify starburst galaxi es atz ∼ 0.5 and 1, respectively. We perform a fitting of the spectral ene rgy distributions (SEDs) from optical to mid-IR wavelengths, u ing an evolutionary starburst model with a proper treatmen of radiative transfer (SBURT), in order to investigate their nature. Results. The SBURT model reproduces observed optical-to-mid-IR SED s of more than a half of PAH-selected galaxies. Based on the 8μm luminosity, we find ultra luminous infrared galaxies (ULIR Gs) among PAH-selected galaxies. Their PAH luminosity is hi gher than local ULIRGs with a similar luminosity, and the PAH-tototal IR luminosity ratio is consistent with that of less lum inous starburst galaxies. They are a unique galaxy population at high redshi fts and we call these PAH-selected ULIRGs “PAH-luminous” ga laxies. Although they are not as massive as submillimetre galaxies a t z ∼ 2, they have the stellar mass of > 3 × 1010 M⊙ and therefore moderately massive.

The AKARI NEP-Deep survey: a mid-infrared source catalogue

We present a new catalogue of mid-IR sources using the AKARI NEP-Deep survey. The InfraRed Camera (IRC) onboard AKARI has a comprehensive mid-IR wavelength coverage with 9 photometric bands at 2–24 μm. We utilized all of these bands to cover a nearly circular area adjacent to the north ecliptic pole (NEP). We designed the catalogue to include most of sources detected in 7, 9, 11, 15 and 18 μm bands, and found 7284 sources in a 0.67 deg 2 area. From our simulations, we estimate that the catalogue is ~80 per cent complete to 200 μJy at 15–18 μm, and ~10 per cent of sources are missed, owing to source blending. Star-galaxy separation is conducted using only AKARI photometry, as a result of which 10 per cent of catalogued sources are found to be stars. The number counts at 11, 15, 18, and 24 μm are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15 μm at the flux level of ~ 300 μJy. This is likely due to the redshifted PAH emission at 8 μm, given our rough estimate of redshifts from an AKARI colour–colour plot. Along with the mid-IR source catalogue, we present optical-NIR photometry for sources falling inside a Subaru/Sprime-cam image covering part of the AKARI NEP-Deep field, which is deep enough to detect most of AKARI mid-IR sources, and useful to study optical characteristics of a complete mid-IR source sample.

Star Formation and AGN Activity in Galaxies Classified Using the 1.6 μm Bump and PAH Features at z = 0.4–2

We studied the star-formation and AGN activity of massive galaxies in the redshift range z = 0.4-2, which were detected in a deep survey field using the AKARI InfraRed (IR) astronomical satellite and Subaru telescope toward the North Ecliptic Pole (NEP). The AKARI/IRC Mid-InfraRed (MIR) multiband photometry was used to trace the star-forming activities with Polycyclic Aromatic Hydrocarbon (PAH) emission, which is effective not only to distinguish between star-forming and AGN galaxies, but also to estimate the Star Formation Rate (SFR) with converting its flux to the total emitting IR (TIR) luminosity. In combination with the analyses of the stellar components, we studied the MIR SED features of star-forming and AGN-harboring galaxies, which we summarize below: (1) The rest-frame 7.7-μm and 5-μm luminosities are good tracers of star-forming and AGN activities from their PAH and dusty tori emissions, respectively. (2) For dusty star-forming galaxies without AGN, their SFR shows a correlation that is nearly proportional to their stellar mass, and their specific SFR (sSFR) per unit stellar mass increases with redshift. Extinctions estimated from their TIR luminosities are larger than those from their optical SED fittings, which may be caused by geometric variations of dust in them. (3) Even for dusty star-forming galaxies with AGN, SFRs can be derived from their TIR luminosities with subtraction of the obscured AGN contribution, which indicates that their SFRs were possibly quenched around z ≃ 0.8 compared with those without AGN. (4) The AGN activity from their rest-frame 5-μm luminosity suggests that their Super Massive Black Holes (SMBHs) could already have grown to ≃ 3 × 10 8 M ⊙ in most massive galaxies with 10 11 M ⊙ at z > 1.2, and the mass relation between SMBHs and their host galaxies has already become established by z ≃ 1-2.

Star-galaxy separation in the AKARI NEP deep field

Context. It is crucial to develop a method for classifying objects detected in deep surveys at infrared wavelengths. We specifically need a method to separate galaxies from stars using only the infrared information to study the properties of galaxies, e.g., to estimate the angular correlation function, without introducing any additional bias. Aims. We aim to separate stars and galaxies in the data from the AKARI north ecliptic pole (NEP) deep survey collected in nine AKARI/IRC bands from 2 to 24 μm that cover the near- and mid-infrared wavelengths (hereafter NIR and MIR). We plan to estimate the correlation function for NIR and MIR galaxies from a sample selected according to our criteria in future research. Methods. We used support vector machines (SVM) to study the distribution of stars and galaxies in the AKARIs multicolor space. We defined the training samples of these objects by calculating their infrared stellarity parameter (sgc). We created the most efficient classifier and then tested it on the whole sample. We confirmed the developed separation with auxiliary optical data obtained by the Subaru telescope and by creating Euclidean normalized number count plots. Results. We obtain a 90% accuracy in pinpointing galaxies and 98% accuracy for stars in infrared multicolor space with the infrared SVM classifier. The source counts and comparison with the optical data (with a consistency of 65% for selecting stars and 96% for galaxies) confirm that our star/galaxy separation methods are reliable. Conclusions. The infrared classifier derived with the SVM method based on infrared sgc – selected training samples proves to be very efficient and accurate in selecting stars and galaxies in deep surveys at infrared wavelengths carried out without any previous target object selection.

Chandra survey in the AKARI North Ecliptic Pole Deep Field - I. X-ray data, point-like source catalogue, sensitivity maps, and number counts

Mon. Not. R. Astron. Soc. 000, 1–?? (2015) Printed 25 March 2015 (MN LaTEX style file v2.2) arXiv:1409.7697v2 [astro-ph.HE] 24 Mar 2015 Chandra survey in the AKARI North Ecliptic Pole Deep Field. I. X-ray data, point-like source catalog, sensitivity maps, and number counts M. Krumpe, 1,3⋆ T. Miyaji, 2,3 H. Brunner, 4 H. Hanami, 5 T. Ishigaki, 5 T. Takagi, 6 A. G. Markowitz, 3,7 T. Goto, 8 M. A. Malkan, 9 H. Matsuhara, 6,10 C. Pearson, 11,12,13 Y. Ueda, 14 and T. Wada 6 1 European Southern Observatory, ESO Headquarters, Karl-Schwarzschild-Strase 2, 85748 Garching bei M¨ unchen, Germany de Astronom´ia, Universidad Nacional Aut´ onoma de M´ exico, Carret. Tijuana-Ensenada, Ensenada 22860, BC, Mexico (mailing addr. P.O. Box 439027, San Diego, CA, 92143, USA) 3 University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Dr., La Jolla, CA, 92093-0424, USA 4 Max-Planck-Institut f¨ ur extraterrestrische Physik, Giesenbachstrase, 85748 Garching bei M¨ unchen, Germany 5 Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan 6 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 229-8510, Kanagawa, Japan 7 Karl Remeis Observatory and Erlangen Centre for Astroparticle Physics, Sternwartstrase 7, 96049 Bamberg, Germany; Alexander von Humboldt Fellow 8 Institute for Astronomy, University of Hawaii 2680 Woodlawn Drive, Honolulu, HI, 96822, USA 9 University of California, Los Angeles, Division of Astronomy & Astrophysics, 430 Portola Plaza, Los Angeles, CA, 90095-1547, USA 10 Department of Space and Astronautical Science, The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa, 240-0193, Japan 11 RAL Space, STFC Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX, UK 12 The Open University, Milton Keynes, MK7 6AA, UK 13 University of Oxford, Keble Rd, Oxford, OX1 3RH, UK 14 Department of Astronomy, Kyoto University, Kyoto, 606-8502, Japan 2 Instituto Released 2014 January 17 ABSTRACT We present data products from the 300 ks Chandra survey in the AKARI North Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band infrared pho- tometry covering 2–24 µm from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ∼15 µm, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z ∼ 1. We design a source detection procedure, which performs joint Maximum Likeli- hood PSF fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 deg 2 . The procedure has been highly optimized and tested by simulations. We provide a point source catalog with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5–7, 0.5–2, 2–7, 2–4, and 4–7 keV bands. The catalog contains 457 X-ray sources and the spurious fraction is estimated to be ∼1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical MIR counterparts in the central 0.25 deg 2 , where deep Sub- aru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ∼80 per cent have optical counterparts and ∼60 per cent also have AKARI mid-IR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. Around 30 per cent of all AGN that have MID-IR SEDs purely explain- able by AGN activity are strong Compton-thick AGN candidates. Key words: methods: data analysis – surveys – galaxies: active – X-ray: galaxies. E-mail: mkrumpe@ucsd.edu c 2015 RAS INTRODUCTION The search for Compton-thick absorbed (CT) AGN and the quantification of their contribution to the total accretion

Galaxy Clusters at 0.9< z <1.7 in the AKARI NEP deep field.

There is a huge gap between properties of red-sequence selected massive galaxy clusters at z 3. It is important to understand when and how the z > 3 proto-clusters evolve into passive clusters at z 1, taking advantage of the 4000u break and the 1.6µm bump. We carefully selected 16 promising cluster candidates at 0.9 < z < 1.7, which all show obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S15µm/S9µm flux ratio is an extinction-free indicator of galaxy star formation activity due to the redshifted PAH emission lines (6.2,7.7 and 8.6µm). We show statistically that the cluster galaxies have a lower S15µm/S9µm flux ratio than field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9 < z < 1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.

Clustering of the AKARI NEP deep field 24 μm selected galaxies

Aims. We present a method of selection of 24 μ m galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 μ Jy and measurements of their two-point correlation function. We aim to associate various 24 μ m selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution. Methods. We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r 0 ) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions. Results. We observe two different populations of star-forming galaxies, at z med ∼ 0.25, z med ∼ 0.9. Measurements of total infrared luminosities ( L TIR ) show that the sample at z med ∼ 0.25 is composed mostly of local star-forming galaxies, while the sample at z med ∼ 0.9 is composed of luminous infrared galaxies (LIRGs) with L TIR ∼ 10 11.62 L ⨀ . We find that dark halo mass is not necessarily correlated with the L TIR : for subsamples with L TIR = 10 11.15 L ⨀ at z med ∼ 0.7 we observe a higher clustering length ( r 0 = 6.21 ± 0.78 [ h −1 Mpc]) than for a subsample with mean L TIR = 10 11.84 L ⨀ at z med ∼ 1.1 ( r 0 = 5.86 ± 0.69 h −1 Mpc). We find that galaxies at z med ∼ 0.9 can be ancestors of present day L ∗ early type galaxies, which exhibit a very high r 0 ∼ 8 h −1 Mpc.

AKARI mid-infrared slitless spectroscopic survey of star-forming galaxies at z ≲ 0.5

Ministry of Science and Technology (MOST) of Taiwan [MOST 106-2112-M-001-008-, MOST 107-2119-M-001-026-]; National Research Foundation of Korea (NRFK) grant [2017R1A3A3001362]; Korean government (MSIP); Leverhulme Trust; UNAM-DGAPA PAPIIT [IN104216]; CONACyT [252531]; JSPS KAKENHI [26247030]; JSPS [21340042]

High excitation emission line nebula associated with an ultra-luminous X-ray source at z = 0.027 in the AKARI North Ecliptic Pole Deep Field

Aims. We report our finding of a high excitation emission line nebula associated with an Ultra Luminous X-ray source (ULX) at