A&A 514, A9 (2010) Astronomy DOI: 10.1051/0004-6361/200913383 & c ESO 2010 Astrophysics Science with AKARI Special feature The AKARI FU-HYU galaxy evolution program: first results from the GOODS-N field C. P. Pearson1,2,3, S. Serjeant3, M. Negrello3,T.Takagi4, W.-S. Jeong5, H. Matsuhara4,T.Wada4,S.Oyabu4, H. M. Lee6,andM.S.Im6 1 Space Science and Technology Department, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK e-mail: [email protected] 2 Department of Physics, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1J 1B1, Canada 3 Astrophysics Group, Department of Physics, The Open University, Milton Keynes MK7 6AA, UK 4 Institute of Space and Astronautical Science, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229 8510, Japan 5 KASI, 61-1, Whaam-dong, Yuseong-gu, Deajeon 305-348, South Korea 6 Department of Physics and Astronomy, Seoul National University, Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea Received 30 September 2009 / Accepted 9 February 2010 ABSTRACT The AKARI FU-HYU mission program carried out mid-infrared imaging of several well studied Spitzer fields preferentially selecting fields already rich in multi-wavelength data from radio to X-ray wavelengths filling in the wavelength desert between the Spitzer IRAC and MIPS bands. We present the initial results for the FU-HYU survey in the GOODS-N field. We utilize the supreme multiwavelength coverage in the GOODS-N field to produce a multiwavelength catalogue from infrared to ultraviolet wavelengths, containing more than 4393 sources, including photometric redshifts. Using the FU-HYU catalogue we present colour-colour diagrams that map the passage of PAH features through our observation bands. We find that the longer mid-infrared bands from AKARI (IRC-L18W 18 mi- cron band) and Spitzer (MIPS24 24 micron band) provide an accurate measure of the total MIR emission of the sources and therefore their probable total mid-infrared luminosity. We also find that colours incorporating the AKARI IRC-S11 11 micron band produce a bimodal distribution where an excess at 11 microns preferentially selects moderate redshift star-forming galaxies. These powerful colour-colour diagnostics are further used as tools to extract anomalous colour populations, in particular a population of Silicate Break galaxies from the GOODS-N field showing that dusty starbursts can be selected of specific redshift ranges (z = 1.2−1.6) by mid-infrared drop-out techniques. The FU-HYU catalogue will be made publically available to the astronomical community. Key words. methods: observational – catalogs – surveys – galaxies: evolution – infrared: galaxies 1. Introduction GOODS survey (300 square arcmins over 2 fields, Giavalisco et al. 2004), the other GTO fields and the Spitzer first look survey Studies with the Infrared Space Observatory (ISO) of the Hubble (FLS, e.g. Frayer et al. 2006)aswellashavingcoverageoverthe deep fields, north and south (HDF-N, HDF-S) have revealed star 3.5−160 μm wavelength range also include a wealth of ancillary formation rates at least comparable to or higher than those of the data at other wavelengths from radio to X-rays. However, Spitzer / optical UV studies (Mann et al. 2002). At submillimetre wave- has limited imaging capability between 8 μm <λ<24 μmand lengths, surveys in the same HDF-N field with SCUBA on the μ −2 no spectroscopic capability shortward of 5 m leaving a conspic- JCMT has revealed a large (>3000 deg at S 850 > 2 mJy) popu- uous gap in these ranges in both wavelength and redshift. lation of strongly evolving sources with bolometric luminosities 12 −1 >10 L and star formation rates of ∼300−1000 M yr with a The AKARI satellite, (formerly known as ASTRO-F, median redshift of 2.4 (Chapman et al. 2005). The overwhelming Murakami et al. 2007) is the first Japanese space mission ded- conclusion is that the star formation rate at z ∼ 1−2 requires sig- icated to infrared astrophysics and was launched on board nificant evolution in the IR galaxy population from the current JAXA’s M-V Launch Vehicle No. 8 (M-V-8) at 6:28 a.m. on epoch. Deep observations with the Spitzer space telescope have February 22, 2006 Japan Standard Time, JST (February 21st, confirmed this strong evolution in the galaxy population out to 9.28 p.m. UT) from the Uchinoura space center (USC) on the the intermediate redshift range probed by ISO (z ∼ 0.3−1) and southern tip of Japan. The satellite is in a Sun-synchronous polar furthermore provided insight into the higher redshift Universe orbit at an altitude of 700 km and a period of 100 min. AKARI in the so called redshift desert z ∼ 1−3. To connect the lo- has a 68.5 cm cooled telescope with two focal plane instru- cal and intermediate redshift Universe to the higher and high z ments, namely the far-infrared surveyor (FIS) and the infrared Universe observed by Spitzer and SCUBA, comprehensive mul- camera (IRC). The FIS has two 2-dimensional detector arrays tiwavelength imaging and spectroscopy is required throughout and observes in four far-infrared bands between 50 and 180 μm the extragalactic population. The fields surveyed by the Spitzer (Kawada et al. 2007). The IRC consists of three cameras cover- space telescope are some of the most richest fields in multi- ing 1.7−26 μm in 9 bands (see Table 1) with fields of view of wavelength data in the entire sky. The SWIRE wide area sur- approximately 10 × 10 (Onaka et al. 2007). Both instruments vey (50 square degrees over 6 fields, Lonsdale et al. 2004), the have low- to moderate-resolution spectroscopic capability. Article published by EDP Sciences Page 1 of 18 A&A 514, A9 (2010) Table 1. Photometric filter band definitions for the three cameras of the IRC. ∗ Camera Array Area Pixel scale Band λref Δλ (pixels) (arcsec) (μm) (μm) NIR 319 × 412 1.46 × 1.46 N2 2.4 1.9–2.8 #" N3 3.2 2.7–3.8 N4 4.1 3.6–5.3 MIR-S 233 × 256 2.34 × 2.34 S7 7.0 5.9–8.4 #!!% S9W 9.0 6.7–11.6 S11 11.0 8.5–13.1 MIR-L 246 × 239 2.51 × 2.39 L15 15.0 12.6–19.4 L18W 18.0 13.9–25.6 L24 24.0 20.3–26.5 Notes. (∗) This is the effective imaging area of the array. The AKARI mission is primarily a survey mission with an all-sky survey in the far-infrared and large mid-infrared legacy $#! " survey programs being carried out in the region of the North Ecliptic Pole (Matsuhara et al. 2006) and the Large Magellanic Fig. 1. The comprehensive coverage of the AKARI and Spitzer bands Cloud. However in addition to these large surveys (LS), a cam- in the FU-HYU fields. The combination of the AKARI and Spitzer paign of guaranteed time observations, referred to as mission bands completely cover the features in the mid-infrared spectra of star- programs (MP) was also undertaken. forming galaxies (STFG, shown in the figure at three different redshifts) ∼ We report the initial results from the AKARI-FU-HYU mis- locally, out to redshifts of 2. sion program (Follow-Up Hayai-Yasui-Umai). The FU-HYU MP strategically targeted well-studied fields to maximise the opportunities whilst fields near the ecliptic may only be visi- legacy value of the AKARI data and in particular to target Spitzer ble on a few orbits every six months. Taking as an example the fields in the above mentioned conspicuous wavelength “gap”, at two well known fields of ISO-ELAIS N1 (Oliver et al. 2000) wavelengths of 11, 15 and 18 μm. The FU-HYU observations fill at an ecliptic latitude of β ∼ 73◦ and the UKIDSS-UDS field in vital gaps in the wavelength coverage (see Fig. 1) and provide (Lawrence et al. 2007)atβ ∼−17◦, we find that the former invaluable insight into the connection between ISO and Spitzer is observable of 17 orbits during half a year whilst the latter is populations and linking the far-infrared Universe to the high red- observable only 5 times. Given that not every AKARI orbit is shift sub-mm Universe as observed by the SCUBA instrument on available for observation (calibration, directors time, etc.) and the James Clerk Maxell Telescope. further constraints placed on the observations by the necessity The FU-HYU program imaged three major fields of choice of the deep imaging AOT (see below), there exist very (GOODS-N, Lockman Hole, ELAIS-N1, see Sect. 2)and clear criteria for our choice of target fields. in this work we report on the initial data reduction and results For the FU-HYU program we selected three contemporary from the GOODS-N observations. Observation in the Lockman data rich fields; Hole will be reported by Serjeantetal.(2010). Unfortunately, the FU-HYU observations in the GOODS-N – the GOODS North field (GOODS-N); field were not dithered during the observation operation result- – the ELAIS-N1 field; ing in many hot and bad pixels leaving holes in the final co- – the Lockman Hole. added images. Moreover the distortion correction in the standard The ELAIS-N1 field (RA = 16h09m20s; Dec =+54◦5700, IRC pipeline toolkit blurs the hot pixels compounding the prob- J2000, β = 73◦) is one of the the most richest fields in mul- lem. In Sect. 3 we describe in detail our extensive additional pro- tiwavelength data on the entire sky. The ELAIS-N1 field was cessing utilizing intrinsic jitter in the spacecraft observations as ff selected as part of the extragalactic large area ISO survey an e ective dithering and interrupting the standard IRC pipeline (ELAIS, Oliver et al.