The Treasury of the
AKARI NEP fieldTing-Chi Huang, Tomotsugu Goto, Hideo Matsuhara, Nagisa
Oi, Tetsuya Hashimoto, Seong-Jin Kim, Simon Ho, Toshinobu
Takagi, and the AKARI NEP teamPresented by (Kevin) Ting-Chi Huang
SOKENDAI, ISAS/JAXA
June 5th, 2019

Outline

Introduction
AKARI space telescope

Data
NEP survey

Studies
AGN/SF separation
Cluster candidates

SummaryIntroduction
AKARI space telescope

Introduction: AKARI
A space telescope made by JAXA. (2006~2011)

Far InfraredSurveyor (FIS)Infrared Camera(IRC)

AKARI spacetelescope
Credit: JAXA

Wright et al. (2010)

Introduction:
AKARI’s advantage
Other IR Observatories including
WISE and Spitzer have only 4bands in mid-IR, and they haveobservation gap in general.
AKARI IRC has 9 bands with
continuous wavelength coveragein mid-IR, so that we are able to
avoid the uncertainties frominterpolation in SED ﬁtting.
Matsuhara et al. (2006)

WISE

Data
The AKARI NEP survey

AKARI North Ecliptic
Pole (NEP) ﬁeld

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66:30.00

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5.4 square degree~72000 AKARI-HSC sourcesCFHT MegaCam/u*,g’,r’,i’,z’
Subaru HSC/g, r, i, z, Y
KPNO 2.1 FLAMINGOS/J, H
CFHT WIRCam/Y, J, Ks
AKARI IRC/ 9 bands
WISE W1, W2, W3, W4
Spitzer IRAC 3.6 and 4.5
Herschel PACS/100,160
Herschel SPIRE/250,350,500

Current status of the NEP research
NEP deep

NEP Wide❖
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AKARI catalog: K. Murata et al. 2013
Optical data (CFHT) and photo-z: N. Oi etal. 2014
Near-infrared data (KPNO): K. Imai et al.
2014 and Y. Jeon et al. 2014
X-ray data (Chandra): M. Krumpe et al.
2015
Luminosity function: T. Goto et al. 2015
AGN selection: T.-C. Huang et al. 2017❖➢➢➢➢➢➢AKARI catalog: S.-J. Kim et al. 2012
Optical data (HSC): N. Oi et al. 2018
Far-infrared data (Herschel): C. Pearson
et al. 2019
Luminosity function: T. Goto et al. 2019
Band-merged catalog: Seong-Jin Kim,Nagisa Oi
Photo-z: Simon HoAGN fraction and SED fitting: Tina Wang
Cluster candidates: Ting-Chi Huang
Data server: Ho-Seong Hwang
Morphology: Eunbin Kim, Matt Malkan

AGN/SFG separationin the AKARI NEP
deep ﬁeld
MNRAS 471, 4239

AGN/SFG separation
Active Galactic Nucleus (AGN) plays
an important role in galaxy evolution.
Because of the dusty torus, AGNtends to be obscured and be missed
in UV, optical and soft X-ray
observations.
However, we can use infrared toobserve obscured AGNs.

AGN/SFG separation

Jarrett et al. (2011)

Lacy et al. (2004)

AGN/SFG separation
Star-forming
galaxies (SFGs)

Polletta et al. (2007)

Active GalacticNuclei (AGN)

Polycyclic aromatichydrocarbon (PAH)emission features at
3.3, 6.2, 7.7, 8.6, and11.3μmWarm dust continuum
emission in IR due toblackbody radiation(A power lawspectrum)

Stellar component
from UV to NIR

Silicate absorption at
9.7μm

Results: Comparison with color-color diagram
AGN selection criteria in WISE
color-color diagram. (Jarrett et al.
2011)● X-ray AGN catalog from Chandra
NEP ﬁeld survey. (Krumpe et al.
2014)● Star-Galaxy separation by
CLASS_STAR parameter of 0.9 in
SExtractor.
The criteria are deﬁned to cover QSOs,
so moderately luminous AGNs andULIRGs are missed.
●

Results: Comparison with color-color diagram●●SED AGNs in WISE color-color
diagram. (Jarrett et al. 2011)
9 best-ﬁtting models are plottedin different colors.

The objects outside the box are
mainly Seyfert 1.8 and Seyfert 2.
SED ﬁtting could capture thehost-dominated or moderately
luminous AGNs, which color
methods usually miss.

Results: X-ray examination and recovering rate
254 X-ray AGNs.
Comparison of AGN selection
between SED ﬁtting and color box
in X-ray AGN samples.
The fraction of AGN selected in the254-X-ray-AGN sample is deﬁned to be
recovering rate.
●●SED ﬁtting has higher recovering rate
than color-color diagram selection.
Having as many bands as possible isbeneﬁcial in SED ﬁtting.

Galaxy cluster
selection

Method● Redshift bins from 0 to 1.2 (bin size 0.1)
● High density peaks are deﬁned by 3-sigma of the local
number density in the 10th-nearest neighborhood.
● Applied friend-of-friend algorithm to high density peaks
to obtain cluster candidates. (linking length = 1.5 Mpc,
group members > 7)
★ Because the data are still under construction, this result
is just preliminary and uncertainty might be high.

●●4000 angstrom break.
Stellar bump at 1.6 micron.

Color evolution can roughly beseen.
Some cluster candidates lookpromising.

Summary
AKARI NEP ﬁeld is fruitful with multi-wavelength data from X-ray tofar-infrared, especially the 9-band IRC photometry in mid-infrared.
AGN selection by SED ﬁtting with AKARI’s 9-band mid-infrared photometry
can identify the AGN missed by previous color-color methods.
We have established a method to select galaxy candidates by k-th nearest
neighbor density and friend-of-friend algorithm.