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AKARI mid-infrared slitless spectroscopic survey of star-forming galaxies at <i>z</i> ≲ 0.5
Ohyama, Y.,Wada, T.,Matsuhara, H.,Takagi, T.,Malkan, M.,Goto, T.,Egami, E.,Lee, H.-M.,Im, M.,Kim, J.H.,Pearson, C.,Inami, H.,Oyabu, S.,Usui, F.,Burgarella, D.,Mazyed, F.,Imanishi, M.,Jeong, W.-S.,Miya EDP Sciences 2018 Astronomy and astrophysics Vol.618 No.-
<P><I>Context.</I> Deep mid-infrared (MIR) surveys have revealed numerous strongly star-forming galaxies at redshift <I>z</I> ≲ 2. Their MIR fluxes are produced by a combination of continuum and polycyclic aromatic hydrocarbon (PAH) emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy.</P><P><I>Aims.</I> We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR (SFR per stellar mass) up to <I>z</I> ≃ 0.5, by paying particular attention to their PAH properties.</P><P><I>Methods.</I> We conducted a low-resolution (<I>R</I> ≃ 50) slitless spectroscopic survey at 5-13 <I>μ</I>m of 9 <I>μ</I>m flux-selected sources (>0.3 mJy) around the north ecliptic pole with the infrared camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identify 48 PAH galaxies with PAH 6.2, 7.7, and 8.6 <I>μ</I>m features at <I>z</I> < 0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and IRC imaging covering 0.37-18 <I>μ</I>m were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7 <I>μ</I>m PAH feature over the 3.5 <I>μ</I>m stellar component of the SEDs.</P><P><I>Results.</I> The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7 <I>μ</I>m bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identify a PAH-enhanced population at <I>z</I> ≳ 0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we cannot confirm this optically think component from our spectral analysis.</P>
OVERVIEW OF NORTH ECLIPTIC POLE DEEP MULTI-WAVELENGTH SURVEY (NEP-DEEP)
H. Matsuhara,T. Wada,N. Oi,T. Takagi,T. Nakagawa,K. Murata,T. Goto,S. Oyabu,T.T. Takeuchi,K. Ma lek,A. Solarz,Y. Ohyama,T. Miyaji,M. Krumpe,H. M. Lee,임명신,S. Serjeant,C. P. Pearson,G. J. White,M. A. Ma 한국천문학회 2017 天文學論叢 Vol.32 No.1
The recent updates of the North Ecliptic Pole deep (0.5~deg$^2$, NEP-Deep)multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15~$\mu$m or 18~$\mu$mselected galaxies, which is the largest sample ever made at thesewavelengths. A continuous filter coverage in the mid-infrared wavelength(7, 9, 11, 15, 18, and 24~$\mu$m) is unique and vital to diagnose thecontributions from starbursts and AGNs in the galaxies out to $z$=2. The new goal of the project is to resolve the nature of the cosmic star formationhistory at the violent epoch (e.g. $z$=1--2), and to find a clue to understandits decline from $z$=1 to presentuniverse by utilizing the unique power of the multiwavelength survey. The progressin this context is briefly mentioned.
OVERVIEW OF THE NORTH ECLIPTIC POLE DEEP MULTI-WAVELENGTH SURVEY (NEP-DEEP)
Matsuhara, H.,Wada, T.,Takagi, T.,Nakagawa, T.,Murata, K.,Churei, S.,Goto, T.,Oyabu, S.,Takeuchi, T.T.,Ohyama, Y.,Miyaji, T.,Krumpe, M.,Lee, H.M.,Im, M.,Serjeant, S.,Peason, C.P.,White, G.,Malkan, M.A The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
An overview of the North Ecliptic Pole (NEP) deep multi-wavelength survey covering from X-ray to radio wavelengths is presented. The main science objective of this multi-wavelength project is to unveil the star-formation and AGN activities obscured by dust in the violent epoch of the Universe (z=0.5-2), when the star formation and black-hole evolution activities were much stronger than the present. The NEP deep survey with AKARI/IRC consists of two survey projects: shallow wide (8.2 sq. deg, NEP-Wide) and the deep one (0.6 sq. deg, NEP-Deep). The NEP-Deep provides us with a $15{\mu}m$ or $18{\mu}m$ selected sample of several thousands of galaxies, the largest sample ever made at these wavelengths. A continuous filter coverage at mid-IR wavelengths (7, 9, 11, 15, 18, and $24{\mu}m$) is unique and vital to diagnose the contribution from starbursts and AGNs in the galaxies at the violent epoch. The recent updates of the ancillary data are also provided: optical/near-IR magnitudes (Subaru, CFHT), X-ray (Chandra), FUV/NUV (GALEX), radio (WSRT, GMRT), optical spectra (Keck/DEIMOS etc.), Subaru/FMOS, Herschel/SPIRE, and JCMT/SCUBA-2.
The AKARI NEP-Deep survey: a mid-infrared source catalogue
Takagi, T.,Matsuhara, H.,Goto, T.,Hanami, H.,Im, M.,Imai, K.,Ishigaki, T.,Lee, H. M.,Lee, M. G.,Malkan, M.,Ohyama, Y.,Oyabu, S.,Pearson, C. P.,Serjeant, S.,Wada, T.,White, G. J. Springer-Verlag 2012 Astronomy and astrophysics Vol.537 No.-
<P>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<SUP>2</SUP> area. From our simulations, we estimate that the catalogue is~80 per cent complete to 200µJy at 15–18µm, 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 24µm are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15µm at the flux level of~300micro;Jy. This is likely due to the redshifted PAH emission at 8µm, 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.</P>