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Infrared luminosity functions based on 18 mid-infrared
bands: revealing cosmic star formation history with
AKARI and Hyper Suprime-Cam*
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How to cite:
Goto, Tomotsugu; Oi, Nagisa; Utsumi, Yousuke; Momose, Rieko; Matsuhara, Hideo; Hashimoto, Tetsuya;
Toba, Yoshiki; Ohyama, Youichi; Takagi, Toshinobu; Chiang, Chia-Ying; Kim, Seong Jin; Kilerci Eser, Ece; Malkan,
Matthew; Kim, Helen; Miyaji, Takamitsu; Im, Myungshin; Nakagawa, Takao; Jeong, Woong-Seob; Pearson, Chris;
Barrufet, Laia; Sedgwick, Chris; Burgarella, Denis; Buat, Veronique and Ikeda, Hiroyuki (2019). Infrared luminosity
functions based on 18 mid-infrared bands: revealing cosmic star formation history with AKARI and Hyper Suprime-
Cam*. Publications of the Astronomical Society of Japan, 71(2), article no. 30.
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2019 The Authors
https://creativecommons.org/licenses/by-nc-nd/4.0/
Version: Accepted Manuscript
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arXiv:1902.02801v1 [astro-ph.GA] 7 Feb 2019
Publ. Astron. Soc. Japan (2014) 00(0), 1–10
doi: 10.1093/pasj/xxx000
1
Infrared luminosity functions based on 18
mid-infrared bands: revealing cosmic star
formation history with AKARI and Hyper
Suprime-Cam
∗
Tomotsugu GOTO
1
, Nagisa OI
2
, Yousuke UTSUMI
3
, Rieko MOMOSE
1,4
,
Hideo MATSUHARA
5
, Tetsuya HASHIMOTO
1
, Yoshiki TOBA
6
, Youichi
OHYAMA
6
, Toshinobu TAKAGI
7
, Chia Ying CHIANG
1
, Seong Jin KIM
1
, Ece
KILERCI ESER
1
, Matthew MALKAN
8
, Helen KIM
8
, Takamitsu MIYAJI
9
,
Myungshin IM
10
, Takao NAKAGAWA
5
, Woong-Seob JEONG
11,12
, Chris
PEARSON
13,14
, Laia BARRUFET
15
, Chris SEDGWICK
14
, Denis BURGARELLA
16
,
Veronique BUAT
16
and Hiroyuki IKEDA
17
1
National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013
2
Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
3
Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), SLAC National Accelerator
Laboratory, Stanford University, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
4
Department of Astronomy, School of Science, The University of Tokyo 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, JAPAN
5
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1
Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
6
Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617,
Taiwan
7
Japan Space Forum, 3-2-1, Kandasurugadai, Chiyoda-k u, Tokyo 101-0062 Japan
8
Department of Physics and Astronomy, UCLA, Los Angeles, CA, 90095-1547, USA
9
Insitituto de Astronom´ıa, U niversidad Nacional Aut
´
onoma de M
´
exico
10
Astronomy Program, Department of Physics & Astr onomy, FPRD, Seoul National University,
Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea
11
Korea Astronomy and Space Science Institute (KASI), 776 Daedeok-daero, Yuseong-gu,
Daejeon 34055, Korea
12
Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113,
Korea
13
RAL Space, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
14
The Open University, Milton Keynes, MK7 6AA, UK
15
European Space Astronomy Centre, 28691 Villanueva de la Canada, Spain
16
Aix-Marseille Universit, CNRS LAM (Laboratoire dAstrophysique de Marseille) UMR 7326,
13388 Mars eille, France
c
2014. Astronomical Society of Japan.
2 Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0
17
National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo, Japan
∗
E-mail: tomo@gapp.nthu.edu.tw
Received 2018 June 30; Accepted 2019 January 21
Abstract
Much of the star formation is obscured by dust. For the complete understanding of the cosmic
star formation history (CSFH), infrared (IR) census is indispensable. AKARI carried out deep
mid-infrared observations using its continuous 9-band filters in the North Ecliptic Pole (NEP)
field (5.4 deg
2
). This took significant amount of satellite’s lifetime, ∼10% of the entire pointed
observations. By combining archival Spitzer (5 bands) and WISE (4 bands) mid-IR photometry,
we have, in total, 18 band mid-IR photometry, which is the most comprehensive photometric
coverage in mid-IR for thousands of galaxies. However previously, we only had shallow optical
imaging (∼25.9ABmag) in a small area of 1.0 deg
2
. As a result, there remained thousands of
AKARI’s infrared sources undetected in optical. Using the new Hyper Suprime-Cam on Subaru
telescope, we obtained deep enough optical images of the entire AKARI NEP field in 5 broad
bands (g ∼27.5mag). These provided photometric redshift, and thereby IR luminosity for the
previously undetected faint AKARI IR sour ces. Combined with the accurate mid-IR luminosity
measurement, we constr ucted mid-IR LFs, and thereby performed a census of dust-obs cured
CSFH in the entire AKARI NEP field. We have measured restframe 8µm, 12µm luminosity
functions (LFs), and estimated total infrared LFs at 0.35<z<2.2. Our results are consistent with
our previous work, but with much reduced statistical err ors thanks to the large area coverage
of the new data. We have possibly witnessed the turnover of CSFH at z ∼2.
Key words: AKARI, infrared galaxies, cosmic star formation history
1 Introduction
Mid-infrared ( mid-IR) is one of the less explored wavelengths
due to the earth’s atmosphere, and difficulties in developing sen-
sitive detectors. NASA’s S pitzer and WISE space telescopes
only had four filters in the mid-IR wavelength range, hamper-
ing studies of distant galaxies.
AKARI space telescope has a potential to revolutionize the
field. Using its 9 continuous mid-IR filters (2-24µm), AKARI
performed a deep imaging survey in the North Ecliptic Pole
(NEP) field over 5.4 deg
2
. Using AKARI’s 9 mid-IR band pho-
tometry, mid-IR SED diagnosis can be performed for thousands
of galaxies, for the first time, over the large enough area to over-
come cosmic variance. Environmental effects on galaxy evolu-
tion can be also investigated with the large volume coverage
(Koyama et al. 2008; Goto et al. 2010a).
However, previously, we were limited by a poor optical cov-
erage both in area and depths. Over this wide area, only shal-
low optical/NIR imaging data have been available (Hwang et al.
2007; Jeon et al. 2010, 2014). Deep optical images are limited
to the central 0.25 deg
2
.
To overcome these problems, we have newly obtained
deeper optical data over the entire AKARI NEP wide field, us-
ing the Hyper-Suprime Cam on the Subaru telescope. Using
the deeper optical data, in this paper, we measure mid-infrared
galaxy LFs, and estimate total IR LFs (based on the mid-IR
SED fitting) from the entire AKARI NEP field. Unless oth-
erwise stated, we assume a cosmology with (h, Ω
m
, Ω
Λ
) =
(0.7,0.3,0.7).
2 Data
To rectify the situation and to fully exploit the AKARI’s space-
based data, we carr ied out an optical survey of the AKARI NEP
wide field (PI:Goto) using Subaru’s new Hyper Suprime-Cam
(HSC; Miyazaki et al. 2018) in five optical bands (g, r,i, z, and
y, Oi et al. 2018 submitted). The HSC has a field-of-view (FoV)
of 1.5 deg in diameter, covered with 104 red-sensitive CCDs. It
has the largest FoV among optical cameras on 8m-class tele-
scopes, and can cover the AKARI NEP wide field (5.4 deg
2
)
with only 4 FoV (Fig.1). The 5 sigma limiting magnitudes are
27.18, 26.71, 26.10, 25.26, and 24.78 mag [AB] in g,r,i,z, and
y-bands, respectively. See Oi et al. (2018, submitted) for more
details of the observation and data reduction.
Subaru telescope does not have u
∗
-band capability, while it
is critically important to accurately estimate photometric red-
shifts (photo-z) of low-z galaxies. Therefore, we obtained u
∗
-
band image of the AKARI NEP wide fi eld using the Megaprime
camera of Canada France Hawaii Telescope (PI :Goto, Goto
Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0 3
45:00.0
17:50:00.0
55:00.0
18:00:00.0
05:00.0
10:00.0
15:00.0
65:00:00.0
30:00.0
66:00:00.0
30:00.0
67:00:00.0
30:00.0
Right ascension
Declination
Fig. 1. HSC three color (g, r, i) composite image of the NEP wide field (5.4 deg
2
). The AKARI NEP wide data exist within the white circle.
et al. 2017). Combining the optical six bands, we have obtained
accurate photo-z in the AKARI NEP field (Oi et al. 2018, sub-
mitted). To the detection limit in L18W filter (18.3 ABmag,
Kim et al. 2012), we have 5078 infrared sources.
In addition to the AKARI’s 9 mid-IR bands, in the AKARI
NEP field, there exit archival deep Spitzer (IRAC1,2,3,4 and
MIPS24, Nayyeri et al. 2018) and WISE (W 1, W 2, W 3, and
W 4) images as well. By combining all available mid-IR bands,
in total we used 18 mid-IR bands, which are one of the most
comprehensive mid-IR data sets for thousands of galaxies.
3 Analysis
To compute LFs, we use the 1/V
max
method, following Goto
et al. (2010b, 2015). Uncertainties of the LF values include
fluctuations in the number of sources in each luminosity bin,
the photometric redshift uncertainties, the k-correction uncer-
tainties, and the flux errors. To estimate errors, we used Monte
Carlo simulations from 1000 simulated catalogs. Each sim-
ulated catalog contains the same number of sources. These
sources are assigned with a new redshift, to follow a Gaussian
distribution centered at the photo-z with the width of ∆z/(1 +
z) (∼ 0.060, Oi et al. in preparation). A new flux is also as-
signed following a Gaussian distribution with the width of flux
error. For total infrared (TIR) LF errors, we re-performed the
SED fit for the 1000 simulated catalogs. Note that total in-
frared luminosity is estimated based on mid-IR SED fitting al-
though we have intensive 18-band filter coverage in mid-IR, as
explained in Section 4.3. We ignored the cosmic variance due
to our much improved volume coverage. All the other err ors
4 Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0
Fig. 2. Restframe 8µm LFs based on the AKARI NEP wide field. The blue
diamonds, the purple triangles, the red squares, and the orange crosses
show the 8µm LFs at 0.28 < z < 0.47, 0.65 < z < 0.90, 1.09 < z < 1.41,
and 1.78 < z < 2.22, respectively. AKARI’s MIR filters can observe rest-
frame 8µm at these redshifts in a corresponding filter. Error bars are esti-
mated from the Monte Carlo simulations (§3). The dotted l ines show analytic
fits with a double-power law. The smaller data points at the faint ends are
adopted from the NEP deep field, where AKARI data are deeper (Goto et al.
2015), and are included in the fit. Vertical arrows show the 8µm luminos-
ity corresponding to the flux limit at the central redshift in each redshift bin.
Overplotted LFs are B abbedge et al. (2006) in the pink dash-dotted lines,
Caputi et al. (2007) in the cyan dash-dotted lines, Huang et al. (2007) in
the dark-yellow dash-dotted lines, F u et al. (2010), in the dark green dash-
dotted line, and Kim et al. (2015) in the bright green dash-dotted line. Best-fit
parameters are presented in Table 1.
described above are added to the Poisson errors for each LF bin
in quadrature.
4 Results
4.1 The 8µm LF
We firs t present monochromatic 8µm LFs, because the 8µm lu-
minosity (L
8µm
) has been known as a good indicator of the TIR
luminosity (Babbedge et al. 2006; Huang et al. 2007; Goto et al.
2011a).
An advantage of AKARI is that we do not need k-correction
because one of the continuous filters always convert the rest-
frame 8µm at our redshift range of 0.28 < z < 2.22. Often in
previous work, SED based extrapolation was needed to estimate
the 8µm luminosity. This was often the largest uncertainty. This
is not the case for the analysis present in this paper.
To estimate the restframe 8µm LFs, we followed our previ-
ous method in Goto et al. (2015) as we briefly summarize below.
We used sources down to 80% completeness limits ( Kim et al.
2012). Galaxies are excluded when SEDs were better fit to QSO
Fig. 3. Restframe 12µm LFs based on the AKARI NEP wide field.
Luminosity unit is logarithmic solar luminosity (L
⊙
). The blue diamonds,
the purple triangles, and the red squares show the 12µm LFs at 0.15 < z <
0.35, 0.38 < z < 0.62, and 0.84 < z < 1.16, respectively. The smaller data
points at the faint ends are adopted from the NEP deep field, where AKARI
data are deeper (Goto et al. 2015), and are included in the fit. Vertical arrows
show the 12µm luminosity corresponding to the flux limit at the central red-
shift in each redshift bin. Overplotted LFs are P
´
erez-Gonz
´
alez et al. (2005)
at z=0.3, 0.5 and 0.9 in the dark-cyan dash-dotted l ines, Toba et al. (2014)
at 0< z <0.05 based on WISE in the dark green dash-dotted lines, Rush
et al. (1993) at 0< z <0.3 in the light green dash-dotted lines, and Kim et al.
(2015) at 0< z <0.3 in the pink dash-dotted line. Note Rush et al. (1993) is
at higher redshifts than Toba et al. (2014). Best-fit parameters are presented
in Table 1.
templates (2% from the sample).
We corrected for the completeness using Kim et al. (2012)
(25% correction at maximum, with our selection to the 80%
completeness limits). Four redshift bins of 0.28< z <0.47,
0.65< z <0.90, 1.09< z <1.41, and 1.78< z <2.22, were used,
following our previous work. Then, the 1/V
max
method was
used to compensate for the flux limit.
The resulting restframe 8µm LFs are shown in Fig. 2. The
arrows show the flux limit at the m edian redshift in bin. We
performed the Monte Carlo simulation to obtain errors. They
are smaller than in our previous work (Goto et al. 2010b, 2015)
thanks to the improved area coverage. The faint end marked
with smaller data points are adopted from the NEP deep field,
where AKARI data are deeper (Goto et al. 2015).
Various previous studies are shown with dashed lines for
comparison. Compared to the local LF, our 8µm LFs show
strong evolution in luminosity up to z ∼ 0.9. Interestingly, the
8µm LFs peaks in the 3rd bin ( z∼1), then declines toward z∼2.
