Japanese electromagnetic
follow-up network forgravitational wave
sources: J-GEM
Michitoshi Yoshida, Hiroshima University
on behalf of the J-GEM collaboration

Importance of EM follow-upof GW events
EM identification may provide Where it is hosted, Accurate localization
 Accurate distance Their environments (where it is in a galaxy, which type ofgalaxy, metallicity, density, etc.)

 Information of the accompanying physics andprogenitors
 Equation of state of neutron star
 Physics of explosion associated with GW
 r-process nucleosynthesis

Searching for EM counterparts is crucial
for understanding the nature of GW sources

S-GRB
The most promising GW
sources  NS-NS merger

Kilonova

Metzger & Berger 20123

Kilonova candidate associated with GRB130603B.
NR Tanvir et al. (2013)

Kilonova models
ejecta mass
10-1 M
10-2 MNumerical simulations of kilonova

Tanaka, et al. 2014

Matter ejection by NS-NS、BH-NS coalescence

NS-NS merger

BH-NS merger
5Light curve models of kilonova (Tanaka+ 2014)

BH-NS merger @ 400Mpc
NS-NS merger @ 200Mpc

can be distinguished from SNeby color variation
6

The EM follow-up consortium in Japan•J-GEM: Japanese collaboration for
Gravitational-wave Electro-Magnetic
follow-up observation• Purpose:• Electro-magnetic follow-up of gravitational wave
transients detected by advanced GW detectors(LIGO, Virgo and KAGRA)• Utilize existing optical, infrared, and radio
astronomical facilities of Japanese institutes
2016/07/11

HinOTORI WS @ NAOC

7

Members• M. Yoshida (PI), K. S. Kawabata, M. Uemura, H. Nagashima (Hiroshima
Univ.)• N. Yasuda (IPMU, Univ. of Tokyo)• K. Motohara, M. Doi, T. Morokuma, Y. Tamura, R. Osawa, S. Sako (Univ.
of Tokyo)• N. Kawai, Y. Saito, Y. Yatsu, R. Itoh (Tokyo Inst. of Tech.)• M. Tanaka, H. Nagai (NAOJ)• F. Abe, Y. Asakura (Nagoya Univ.)• K. Ohta, T. Tanaka, N. Seto, T. Nakamura (Kyoto Univ.)• N. Kanda, H. Tagoshi (Osaka City Univ.)• N. Tominaga (Konan Univ.)• Y. Itoh (Hyogo Pref. Univ.)• K. Yanagisawa, D. Kuroda, K. Matsubayashi (OAO, NAOJ)• K. Fujisawa (Yamaguchi Univ.)• T. Nagayama (Kagoshima Univ.)
2014/06/20

Japan-Korea WS on KAGRA

8J-GEM (Japanese collaboration for Gravitational-wave Electro-Magnetic follow-up)
A part of the project “Multi-messenger Observations of GW sources”* collaborating with the KAGRA data analysis team• 1m Kiso Schmidt telescope
6 deg2 camera  36 deg2

Main features:
5 deg2 opt. imaging w/ 1m
1 deg2 NIR imaging w/ 1m
opt-NIR spectroscopy w/ 1–8m
opt-NIR polarimetry

•
••
•
•

★
50cm telescope(Hiroshima Univ. 2016)★
3.8m telescope(Kyoto Univ. 2017)

HSC, Subaru @Hawaii
TAO 6.5m (TokyoUniv. 2018)★
★
IRSF (Nagoya Univ.)@ South Africa

1.5m Kanata telescope
2m Nayuta telescope
50cm MITSuME OAO & Akeno
91cm OAO-WFC of NAOJ
Yamaguchi 32m radio telescope

MOA-II, B&C (NagoyaUniv.) @ New Zeeland

miniTAO (Tokyo Univ.)
ASTE (NAOJ) @ Chile★

Telescopes currently joining J-GEM

10

Optical infrared wide field facilities in the world
optical：red infrared：blue [ ]：future plans

ASAS-SN[ZTF][Kiso/Tomo-e]
GW localization
w/ LVK (2019-)

more effective[LSST]PTF PS1DECamKiso/KWFC
Subaru/HSC
MOAIICFHT[OAO-WFC2]
VISTA
OAO-WFC[WFIRST] WFCam Subaru/SCamJ-GEM

HST/ACS11We are not always able to use HSC,
but its performance is the key for
GW follow-up.

Schematic overview of EM follow-up• Detect GW EM counterpart with wide-fieldobservations• Study the physics of EM counterpart withmulti-mode observations

GW alert

alert

LIGO/Virgo/KAGRA

The natureof GW transient

Wide field obs.

EM counterpart
X-ray γ-ray

Neutrino

Rapid identification
alert to other facilities

Coop.

Yamaguchi32m
NRAO 45m

Multi-wavelen.
detailed study

identification
emission mechanism
IRSFCoop.

theory2016/02/20

Kiso 6x6 deg2
CameraOAO IR WFC

miniTAO

J-GEMMulti-mode obs.
detailed study

World-wide obs.

long term monitor

event evolution
HinOTORI 50cm

G.W. 4th Symposium @ IPMU

MOA-II 1.5x1.5deg2
Cameraredshift -> distanceemission mechanism
KanataSubaruKyoto 3.8m
TAO 6.5m

19Localization of the GW telescopes

Expected light curve of kilonova @100Mpc (Tanaka+ 2014)
Detectable with 1-m class telescopes within 1 – 2days after merger
HSC can follow the light curve for 1 – 2 weeks

Quick follow-up with small telescopes＋ Deep observations with Subaru HSC21

Follow-up observation strategy of J-GEM• Blind survey– 10 deg2 – 100 deg2 blind survey within GW error area
– KWFC, MOA-II and Subaru HSC– 1 color or 2 colors with short exp-time (1 – 3 min)survey• Targeted observation– Select target galaxies using nearby galaxy catalogs– Kanata, Nayuta, MOA-II, IRSF, OAO-WFC and MITSuME– 1 color with ~10 min exp-time per one galaxy

LIGO, Virgo, KAGRA

J-GEM
Kiso

Preliminary Alert

30 minInitial Alert

OAO

preparationin mind…?

Hiroshima
TiTech

KWFC: survey

Kiso

OAO-WFC: survey

OAO
TiTechMITSuME: targeted

Hiroshima

Kanata: targeted

Kyoto IFU
MOA
IRSF
othersSubaru ToO
HSC survey
other targeted

GraceDBSkymapFollow-up status
other information

HSC follow-up strategy
1. Prompt wide field observations– within 5 days after the GW event, if possible– 1 min exposure in 2 bands (𝑖𝑖 and 𝑧𝑧)
 5σ limiting magnitudes: ~24mag for 𝑖𝑖, ~23.5mag for 𝑧𝑧– 2 times visits for one field (effective FOV is ~1.1 deg2)– ~60 deg2 can be surveyed with 2 colors within a half night

2. Second observations for checking the color-magnitude
evolution of the transients– within a few days after the prompt observations

3. Third observations for getting the reference images– 1 – 2 months after the second observations• Data reduction procedure– prompt obs. data – 2nd obs. data  candidate selection– prompt – 3rd, 2nd – 3rd, then study color-mag evolution of thecandidates  characterization

GW150914

36M BH + 29M BH  64M BH at 4１0Mpc

Follow-up observations of GW150914• KWFC on 105 cm Schmidt telescope at Kiso observatory  24 deg2
• tripole5 on the B&C 61cm telescope in New Zealand  18 nearby galaxies
Observation dates: September 18 - 26, 2015
Kiso 105cm Schmidt

observed area Left: KWFC, Right: tripole5

B&C 61cm telescope

Limiting magnitudes:
KWFC 18.9 – 19.2 mag. for I-band
tripole5 g-band: 18.9 mag. r-band: 18.7mag. i-band: 18.3 mag

No EM counterpart
was detected Morokuma, T., et al., 2016, PASJ, 68, L9

Morokuma, T., et al., 2016, PASJ, 68, L9

GW151226

14.2M BH + 7.5M BH  20.8M BH at 440Mpc

2015-12-28 01:28:13 (JST)GCN/LVC_INITIAL_SKYMAP
TITLE:

GCN/LVC NOTICENOTICE_DATE:Sun 27 Dec 15 16:28:13 UTNOTICE_TYPE:

LVC Initial Skymap

TRIGGER_NUM:

G211117

TRIGGER_DATE:

17382 TJD; 360 DOY; 2015/12/26 (yy/mm/dd)

TRIGGER_TIME:

13133.647758 SOD {03:38:53.647758} UTGROUP_TYPE:

1 = CBC (= compact binary coalescence)

SEARCH_TYPE:

3 = HighMass (including BH)

PIPELINE_TYPE: 4 = GSTLAL
FAR:

6.340e-09 [Hz] (one per 1825.5 days)

CHIRP_MASS:
ETA:-1.0000 [M_solar]-1.000

MAX_DIST:-1.00 [Mpc]

TRIGGER_ID:

0x0

MISC:

0x2100003

error region: ~1300deg2 (90%)

Targeted survey

Nayuta/MINT, Kanata/HONIR, TIT-OAO50cm/MITSuME (opt),
OAO91cm/OAO-WFC, IRSFF/SIRIUS (NIR)

Observed galaxies

No. of galaxies-times

238 independent galaxies at <100Mpc
Limiting magnitudes are~18-21 mag

Let’s use Subaru！
•How about the observation
schecule?
33

When will HSC be attached to Subaru?
GW151226

この間すばるにHSCは付いていなかった
すばるの当初スケジュール

34

ハワイ観測所長にお願い

Director Arimoto

J-GEM• 重力波出ましたから、追跡観測を割り込ませてくださいませ。
35

割り込ませてもらいました
GW151226

Updated schedule of Subaru

36

Survey fields
Kiso/KWFC

MOA-II/MOA-Cam

Subaru/HSC

HSC 63.5deg2 (prob. 9%)
KWFC 778deg2 (prob. 10%)
MOA 145deg2 (prob. 11%)
total 986.5 deg2

30% of the probability skymap
were covered by J-GEM.

Candidates from Kiso/KWFC• Observed only fields within SDSS footprints for image
subtraction• 13 supernova candidates• KISS15ai (30 Dec 2015)• r~16.6mag
SDSS

KWFC

difference

SDSS

KWFC

difference• KISS16c (3 Jan 2016)• r~19.3mag• SN2015bl (Type Ia SN)• 3 of them were already reported as supernovae.
• All of them are too bright for GW151226.

Transient candidates found• 1256 candidates were found…
16.8”x16.8”
i-band3.4”x3.4”
Reference

Jan 7 1stJan 7 2ndJan 13z-band

Light curve
39Candidates from Subaru/HSC• 60 candidates are likely to be astronomicalobjects.
• 20 possible AGNs
• 40 SNe• No candidate for an optical counterpart ofGW151230
This is consistent with the fact thatGW151226 was a BH-BH merger at ~440Mpc.

Limiting mag. of the J-GEM follow-ups withkilonova models
MOA-cam3

Pan-STARRS
iPTF

KWFC

KWFC
KanataNayutaMITSuME

DECamHSC

Yoshida, M. et al., 2017, PASJ, 69, 9

Instrumentation
activities of J-GEM

1. Tomo-e : Next Generation
WFC at Kiso Observatory
FoV of Kiso 1mSchmidt Telescope
φ9°

ZTF (1.2m) , 47 □° (2016-)

KWFC/Kiso
4.8 □°, CCD

iPTF (1.2m), 7.8□ °Pan-STARRS (1.8m), 9□°
LSST (8.4m), 9.6 □° (2023-)

Fill-up 20□° of φ 9°with CMOS sensors

F.O.V
φ 9°

Tomo-e: Layout of the Focal Plane
φ 9 °(0.44mag vignetting)

Canon 35mm Full HD CMOS sensor
40’
12’12’

480 mm12’
2000 x 1128 pix

530 mmx 84 chips

23’12’

QE~50%@550nm
Low noise : RON < 2e- rms
Large pixel : 18um/pix

 Total 190 Mpixels
 760 MB/exposureφ 4 °(Vignetting-free area) Driven at Room Temperature

Tomo-e: Data Acquisition System• Data Production Rate : 420MB / one shot
• Requirements :– Typical survey observations (3sec exp / 3sec tel.
slew)
⇒ 70MB/sec– 2Hz monitoring observations (2Hz / frame)⇒ 830MB/sec• Realtime Data Reduction Pipeline– Data reduction (calibration, subtraction, source
detection) should be completed within ~5secCapability of Tomo-e↓ Region where Tomo-e hasan advantage

Kiso/Tomo-e Gozen

Observable Field (deg2)

10,000
ZTF
1,000iPTF

600 deg2

DECamSubaru HSC

100101

1719212325

Limiting Magnitude（Vmag）

27

Tomoe FoV

Tomo-e has a bigadvantage if theposition accuracy ofGW source is not sogood (~100 deg2)

381mmTomo-e prototype: CMOS Sensors
mounted on the Baseplate

588mm

Tomo-e prototype

Tomo-e: Development Schedule
Current

2013

2014

2015

2016

↑ First Light- New Innovative (GW)
- Kaken A (Solar system Obj.)- Sakigake (Big Data)- Kaken A (SNe Survey)- Kaken S (GW)

2018

2017

↑ First Light

Long-term survey

CMOS Procure.
PrototypeSolar system Survey

Data Reduction System
Camera Develop.
Camera Develop.

SNe Survey
GW Folow-up
ToO Obs.

2. OAOWFC: 1 deg2 NIR camera• Optical alignment was completed • LIGO O1 follow-ups were carried out– FWHM=2pix entire frame– Reached J=17~18 with 15minexposure– Almost identical to the 2MASS limit

Ks-band image of the Galactic Plane
2016/02/20

2MASS

G.W. 4th Symposium @ IPMUOAOWFC

Difference51Comparison FOVs: NIR imagers
D=4.1mESO VISTA: 0.77 ×0.77 deg2

D=0.91m
D=3.8mOAOWFC: 0.47 ×0.47 deg2
UKIRT
WFCAM: 0.46 ×0.46 deg2

D=0.8m

IRIS:

0.22 ×0.22 deg2

D=1.4mSIRIUS:

0.13 ×0.13 deg2

OAOWFC’s FOV is one of the largest in the world.
2016/12/26

GW 5th Symposium @ Kyoto

52

3. IFU for the spectrograph ofKyoto 3.8m telescope
Aim:• prompt optical spectroscopy w/ IFU on theOkayama 188 cm and the future 3.8 m
telescope• targets• short GRBs of which positional accuracy is less than
~10-20 arcsec• optical counterpart candidates of GW sources• spectroscopy of SNe, galaxies, etc can also be possible
2016/12/26

GW 5th Symposium @ Kyoto

53

KOOLS-IFU on 188cm telescope
The IFU moves into the optical pathby promptly changing units
when HIDES-F unit is working,which is used frequently.

Fibrebundle
Integral Field Uniton HIDES-F unit
Optical spectrograph: KOOLS
2016/12/26

GW 5th Symposium @ Kyoto

188cm telescope
54

KOOLS-IFU on 188cm telescope:
Performance• FoV of IFU: ~ 30”• FoV of a fibre: ~ 2” (# of fibres =127)• Filling factor: ~ 60%• Wavelength coverage (*): 5020-8830A• Spectral resolution (*): 600-850• Limiting mag (30min, 10σ)(*): 18.7 AB(*) w/ Grism No.2
2016/12/26

GW 5th Symposium @ Kyoto

55

KOOLS-IFU: Future plan
Equip to the 3.8m telescope (on-going)
Filling factor~ 100%CCD grade-up (on-going),
improve throughput

56

3. HinOTORI: a robotic telescope inTibet• Development of a 50cm robotic telescope + 3color camera system West China (Tibet area)• FOV: 24 arcmin x 24 arcmin 0.7 arcsec/pix• Expected limiting mag. (S/N=5 for 10 min exp.)– 18.5 mag. u’-band– 21.1 mag. Rc-band– 20.8 mag. Ic-band

2016/07/11

HinOTORI WS @ NAOC

57

Current status of HinOTORI
The telescope reached at the Ali site
and installed in a dome of NAOC
on Sep. 7 2016.
We plan to visit Ali in this month Full commissioning

Ali site
2016/07/11

HinOTORI WS @ NAOC

58

Road to the Summit
2016/12/26

GW 5th Symposium @ Kyoto

592016/12/26

GW 5th Symposium @ Kyoto

60

大学間連携事業

2011 – 2016 6 universities + NAOJ  GRB
2017 – 2021 8 universities + NAOJ  GW, neutrino, GRB

2016/12/26

GW 5th Symposium @ Kyoto

61Summary• We developed a coordinated network of optical-infraredradio telescopes for follow-up of GW transients, J-GEM.
• The network contains several existing optical-infraredradio telescopes in Japan, Hawaii, South-Africa, New
Zeeland and Chile.
• Subaru HSC is a very powerful optical camera for GW-EM
follow-up (mlim~24 mag for 60 deg2 in a half night)• Three new telescopes are under construction (50cm inTibet, 3.8m in Japan and 6.5m in Chile).
• We plan to make EM follow-up for LIGO O2 from thiswinter.
2014/06/20

Japan-Korea WS on KAGRA

62