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Journal ArticleDOI

Infrared luminosity functions based on 18 mid-infrared bands: revealing cosmic star formation history with AKARI and Hyper Suprime-Cam

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, $\sim$10\% of the entire pointed observations. By combining archival Spitzer (5 bands) and WISE (4 bands) mid-IR photometry, we have, in total, 18 band mid-IR photometry, which is the most comprehensive photometric coverage in mid-IR for thousands of galaxies. However previously, we only had shallow optical imaging ($\sim$25.9ABmag) in a small area of 1.0 deg$^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\sim$27.5mag). These provided photometric redshift, and thereby IR luminosity for the previously undetected faint AKARI IR sources. Combined with the accurate mid-IR luminosity measurement, we constructed mid-IR LFs, and thereby performed a census of dust-obscured CSFH in the entire AKARI NEP field. We have measured restframe 8$\mu$m, 12$\mu$m luminosity functions (LFs), and estimated total infrared LFs at 0.35$<$z$<$2.2. Our results are consistent with our previous work, but with much reduced statistical errors thanks to the large area coverage of the new data. We have possibly witnessed the turnover of CSFH at $z\sim$2.
Topics: Photometric redshift (54%), Luminosity (53%), Photometry (optics) (52%)

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Infrared luminosity functions based on 18 mid-infrared
bands: revealing cosmic star formation history with
AKARI and Hyper Suprime-Cam*
Journal Item
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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arXiv:1902.02801v1 [astro-ph.GA] 7 Feb 2019
Publ. Astron. Soc. Japan (2014) 00(0), 1–10
doi: 10.1093/pasj/xxx000
Infrared luminosity functions based on 18
mid-infrared bands: revealing cosmic star
formation history with AKARI and Hyper
Tomotsugu GOTO
, Nagisa OI
, Yousuke UTSUMI
, Rieko MOMOSE
, Yoshiki TOBA
, Youichi
, Toshinobu TAKAGI
, Chia Ying CHIANG
, Seong Jin KIM
, Ece
, Matthew MALKAN
, Helen KIM
, Takamitsu MIYAJI
Myungshin IM
, Woong-Seob JEONG
, Chris
Veronique BUAT
and Hiroyuki IKEDA
National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013
Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), SLAC National Accelerator
Laboratory, Stanford University, SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
Department of Astronomy, School of Science, The University of Tokyo 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, JAPAN
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1
Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617,
Japan Space Forum, 3-2-1, Kandasurugadai, Chiyoda-k u, Tokyo 101-0062 Japan
Department of Physics and Astronomy, UCLA, Los Angeles, CA, 90095-1547, USA
Insitituto de Astronom´ıa, U niversidad Nacional Aut
onoma de M
Astronomy Program, Department of Physics & Astr onomy, FPRD, Seoul National University,
Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea
Korea Astronomy and Space Science Institute (KASI), 776 Daedeok-daero, Yuseong-gu,
Daejeon 34055, Korea
Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113,
RAL Space, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
The Open University, Milton Keynes, MK7 6AA, UK
European Space Astronomy Centre, 28691 Villanueva de la Canada, Spain
Aix-Marseille Universit, CNRS LAM (Laboratoire dAstrophysique de Marseille) UMR 7326,
13388 Mars eille, France
2014. Astronomical Society of Japan.

2 Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0
National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo, Japan
Received 2018 June 30; Accepted 2019 January 21
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
). 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
. 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 eld 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 eld. 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
. 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
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,
) =
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
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 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
Right ascension
Fig. 1. HSC three color (g, r, i) composite image of the NEP wide field (5.4 deg
). 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
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 tting 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
) has been known as a good indicator of the TIR
luminosity (Babbedge et al. 2006; Huang et al. 2007; Goto et al.
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
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
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 ( z1), then declines toward z2.

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Journal ArticleDOI
David Elbaz1, Mark Dickinson, Ho Seong Hwang1, Tanio Díaz-Santos2  +54 moreInstitutions (21)
Abstract: We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3–500 μm spectral energy distributions (SEDs) of galaxies at 0 < z < 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes. We find that the ratio of total IR luminosity to rest-frame 8 μm luminosity, IR8 (≡ L_(IR)^(tot)/L_8), follows a Gaussian distribution centered on IR8 = 4 (σ = 1.6) and defines an IR main sequence for star-forming galaxies independent of redshift and luminosity. Outliers from this main sequence produce a tail skewed toward higher values of IR8. This minority population ( 3 × 10^(10) L_⊙ kpc^(-2)) and a high specific star formation rate (i.e., starbursts). The rest-frame, UV-2700 A size of these distant starbursts is typically half that of main sequence galaxies, supporting the correlation between star formation density and starburst activity that is measured for the local sample. Locally, luminous and ultraluminous IR galaxies, (U)LIRGs (L_(IR)^(tot)≥ 10^(11) L_☉), are systematically in the starburst mode, whereas most distant (U)LIRGs form stars in the “normal” main sequence mode. This confusion between two modes of star formation is the cause of the so-called “mid-IR excess” population of galaxies found at z > 1.5 by previous studies. Main sequence galaxies have strong polycyclic aromatic hydrocarbon (PAH) emission line features, a broad far-IR bump resulting from a combination of dust temperatures (T_(dust) ~ 15–50 K), and an effective T_(dust) ~ 31 K, as derived from the peak wavelength of their infrared SED. Galaxies in the starburst regime instead exhibit weak PAH equivalent widths and a sharper far-IR bump with an effective T_(dust)~ 40 K. Finally, we present evidence that the mid-to-far IR emission of X-ray active galactic nuclei (AGN) is predominantly produced by star formation and that candidate dusty AGNs with a power-law emission in the mid-IR systematically occur in compact, dusty starbursts. After correcting for the effect of starbursts on IR8, we identify new candidates for extremely obscured AGNs.

1,162 citations

"Infrared luminosity functions based..." refers background in this paper

  • ...Also Elbaz et al. (2011) showed that L8µm/LTIR is different for starbursts....


Journal ArticleDOI
Jonathan P. Gardner1, John C. Mather1, Mark Clampin1, René Doyon2  +19 moreInstitutions (13)
Abstract: The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m. The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations. To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.

1,092 citations

Journal ArticleDOI
Emeric Le Floc'h1, Emeric Le Floc'h2, Casey Papovich2, Herve Dole3  +15 moreInstitutions (6)
Abstract: We analyze a sample of ~2600 Spitzer MIPS 24 μm sources brighter than ~80 μJy and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of the universe up to z ~ 1. Using published ancillary optical data, we first obtain a nearly complete redshift determination for the 24 μm objects associated with R 24 mag counterparts at z 1. These sources represent ~55%-60% of the total MIPS 24 μm population with f24 μm 80 μJy, the rest of the sample likely lying at higher redshifts. We then determine an estimate of their total IR luminosities using various libraries of IR spectral energy distributions. We find that the 24 μm population at 0.5 z 1 is dominated by "luminous infrared galaxies" (i.e., 1011 L☉ ≤ LIR ≤ 1012 L☉), the counterparts of which appear to be also luminous at optical wavelengths and tend to be more massive than the majority of optically selected galaxies. A significant number of fainter sources (5 × 1010 L☉ LIR ≤ 1011 L☉) are also detected at similar distances. We finally derive 15 μm and total IR luminosity functions (LFs) up to z ~ 1. In agreement with the previous results from the Infrared Space Observatory (ISO) and SCUBA and as expected from the MIPS source number counts, we find very strong evolution of the contribution of the IR-selected population with look-back time. Pure evolution in density is firmly excluded by the data, but we find considerable degeneracy between strict evolution in luminosity and a combination of increases in both density and luminosity [L ∝ (1 + z), ∝ (1 + z)]. A significant steepening of the faint-end slope of the IR luminosity function is also unlikely, as it would overproduce the faint 24 μm source number counts. Our results imply that the comoving IR energy density of the universe evolves as (1 + z)3.9±0.4 up to z ~ 1 and that galaxies luminous in the infrared (i.e., LIR ≥ 1011 L☉) are responsible for 70% ± 15% of this energy density at z ~ 1. Taking into account the contribution of the UV luminosity evolving as (1 + z)~2.5, we infer that these IR-luminous sources dominate the star-forming activity beyond z ~ 0.7. The uncertainties affecting these conclusions are largely dominated by the errors in the k-corrections used to convert 24 μm fluxes into luminosities.

936 citations