PBH search with microlensing
Masahiro Takada(Kavli IPMU)
Based on collaborations with, Sunao Sugiyama (IPMU), Naoki Yasuda (IPMU),
T. Sumi (Osaka), S. More (IUCAA/IPMU), Robert Lupton (Princeton), Toshiki Kurita (IPMU),
Misao Sasaki (IPMU), Volodymyr Takhistov (IPMU), Alex Kusenko (UCL/IPMU)@AstroDark-2021, Dec 2021

Primordial black hole (PBH) = A viable DM candidate
Zel’dovich & Novikov 67; Hawking 74⌫<latexit sha1_base64="mZBacTe/Yga11OlslC7/ftyfsz0=">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</latexit>

figure: Hitoshi Murayama

e pbacteria<latexit sha1_base64="0z2xPXPSiCdmX5Z5yqtgJzx9LTA=">AAACiHichVE9TxtBEH1cQiAHBJM0SDQWFiiisOYuxoZUCBpKPmKwZFvW3XlxVj7vHXdnS47FD0j+QAqqIEVRlIKW1GnyByj4CRElkdJQMHc2ghSGWe3O7Nt5M293bd+VYUR0MaI9eTr6bGz8uT4xOfViOjXzci/02oEjio7nekHJtkLhSiWKkYxcUfIDYbVsV+zbzY34fL8jglB66l3U9UW1ZTWUPJCOFTFUS2UqtmhI1ROHygoCq7t0pPt6Raj6PYSzKLu6kjdz+TRliQqGacSBWci9yaUNRmLLYGBbXuobKqjDg4M2WhBQiDh2YSHkUYYBgs9YFT3GAo5kci5wBJ25bc4SnGEx2uS1wbvyAFW8j2uGCdvhLi7PgJlpLNA5facr+k0/6A9dD63VS2rEWrrs7T5X+LXpT7O7/x5ltdhHeH/HelBzhAOsJFola/cTJL6F0+d3Pny+2n27s9BbpBO6ZP1f6IJ+8Q1U56/zdVvsHEPnD7h95fTwYM/MGstZ2jYza+uDrxjHHObxmt+7gDVsYgtF7vsRpzjDT03XSCtoq/1UbWTAeYX/TFu/AdEpl8w=</latexit><latexit sha1_base64="CAxN0VW1zDWFBGwlJ1K8jYSvcLc=">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</latexit>

Human

Earth Sundark matter mass [GeV/c2]
10–40 10–30 10–20 10–10 100 1010 1020 1030 1040 1050 1060 1070
wave-like DM

light DM

WIMP

too light

heavy DM

composite DM・macroscopic DM

excluded by
CMB obs

elementary particle

this talkmacroscopic DM candidate= PBH, axion stars, …
Astronomical data is a way to explore
this macroscopic DM candidate

Current status: excluded regions of PBHs
1015

10

1010

105

1010

0.1

K

0.01

SN
I
O

E

HSC

103

M

GW S1

Eri

lensing

DH
LSS

XB

accretionDFlarge-scale structure
dynamical

V

n/p

CMB
108

PA

EGB

CMB mu-distortion (Planck)

GGB

1015

IL

evaporation

107

1010

CMB

GC

Ly

105

109

1020

G

RS

WB

GW

104

106

1015

Carr, Kohri, Sendouda & Yokoyama 20

1

f (M)

M/M
1
105

GW2

1020

1025

1030

• Assume that all experiments
are null results (shaded
regions are excluded
regions of PBH assuming a
monochromatic massfunction in x-axis)



1035
M [g]

1040

1045

1050

1055

More exciting! A possible hint of PBHs
1015

10

1010

105

1
Open
window

0.1
0.01

Katz+18

f (M)

103

O

E

RS

WB
GW S1

Eri

HSC

1015

1020

G
CMB

GC

Ly

DH
LSS

A possible
observational hint ofEarth-mass PBH

105

DF
IL

Niikura, MT+19a,b

V

107

PBH can be LIGO-Virgo GW sources

108

CMB

109

EGB

1010

K

M

SN
I

1010

XB

104

106

M/M
1
105

Bird+ 16
Sasaki+ 16

GGB

1015

n/p

PA

GW2

1020

1025

1030

If we can observationallyfind any black hole with
M<Msun, it is a smokinggun evidence of PBH



1035
M [g]

1040

1045

1050

1055

Open-minded! PBH+CDM scenario
CDM-like<latexit sha1_base64="w8M6b5YOnB/2HfKNQ665wvbPSec=">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</latexit>(fPBH = 10 5 )fPBH = 10 3<latexit sha1_base64="5fFPaC2WMw4/pYDW/f4/Rjq6uRI=">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</latexit>• Inman & Ali-Haimoud (19) studied structure formation for
PBH+CDM model using N-body simulations• PBH accelerates growth of structure formation• DM halos containing PBH at the center display a cuspy profile

MPBH = 20 h 1 M
zout = 99
1
30 h kpc<latexit sha1_base64="XydDUJf5pl8Phzb6fw2ZMgsYjpE=">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</latexit><latexit sha1_base64="MGAW0N9Iax768H/dzvobrJnmtEI=">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</latexit>(also see Gosenca, Adamek, Byrnes+17)<latexit sha1_base64="OeXqamBuGnzEsF0SjXDgfGEOaeo=">AAACmXichVFNTxNBGH5Yv2D9oMjFhMuGBmNMbN6FCtQTyIV4AmqBhGKzuwxl0t3ZZXbbpGzKD+APmOgJE2OMf8KEC3j3wE8wHjHx4sG32zXqAX0nM/PMM+/zzjMzbuTLOCE6HzKuXL12/cbwiHnz1u07o4Wxu+tx2NaeqHmhH+pN14mFL5WoJTLxxWakhRO4vthwW0v9/Y2O0LEM1fOkG4ntwGkquSs9J2GqUSjXXdGUKhX7ytHa6T7smTN0uPcifWT30roOrFbk9cy6UDt/pDQKRSpVyK48nrMGYL6cg9mKZZcoiyLyWAkL71DHDkJ4aCOAgELC2IeDmNsWbBAi5raRMqcZyWxfoAeTtW3OEpzhMNviscmrrZxVvO7XjDO1x6f43DUrLUzRZ3pPF3RKH+gL/bi0VprV6Hvp8uwOtCJqjB7dq37/ryrgOcHeb9U/PSfYxXzmVbL3KGP6t/AG+s7By4vqk7Wp9D69oa/s/5jO6YRvoDrfvLerYu01TP6AX69sXQ7Wp0v2bKm8Ol1ceJp/xTAmMIkH/N5zWMAyVlDjc1/hI87wyZgwFo1l49kg1RjKNeP4K4zqT9gpnrc=</latexit><latexit sha1_base64="l4C+BT74aj0Ceu3Z2XKGd/ZeZzA=">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</latexit>

fPBH = 10

1• PBH+CDM scenario gives tighter limit on WIMP annihilation
signal for dwarfs (or G.C.) (also might be relevant for cuspy
profile of Draco in Mariangela’s talk for SIDM).
# of halos with PBH

mass profileMicrolensing: robust, powerful method to search for invisible PBH
Paczynski 86; Griest 91• Microlensing occurs when observer-lens-source are almost aligned• Einstein radiusRE =• Light curve timescale<latexit sha1_base64="i/WOh5HgAu4bIC7eeCcTcD789OU=">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</latexit>r

4⇡GMPBH d(1c2d/ds )

2RE
tE ⇠
vrel
on the sky

light curve

credit: Sunao Sugiyama

Microlensing experiment• What we need are …
• Need a wide field-of-view camera (plus large-aperture telescope if possible)• Need a monitoring observation of the same stars in a target region (LMC, Galactic bulge andAndromeda galaxy (M31))• Previous and ongoing microlensing experiments• MACHO (1992-99: 1.27m, Alcock+00, 01: LMC), OGLE (1992-: 1.3m, LMC/G.C.), EROS-I/II (90-03:
1.5m, LMC, G.C.), EROS2 ...
• For M31, several attempts were made, but face difficulty (pixel lensing) (e.g., Novati 10 for a review)• Griest+ (2014) used the public Kepler data to search for PBH microlensing• Subaru HSC microlensing observations for M31 (PI: Takada: 2014 - )• Upcoming experiments (more focused on exoplanet search, but the same data can beused for PBH search)• VRO LSST (G.C.), PRIME (PI: T. Sumi, Osaka U.: G.C.), Roman Space Telescope (G.C.), ….

Search of PBH with microlensing

PBH
HSC M31 PBH
microlensing search(Niikura, MT+Nature Astron. 19)

OGLE (Optical Gravitational Lensing
Experiment) for PBH search(Niikura, MT+, PRD 19)

M31 halo

PBH microlensing of M31 star
• For a case to monitor many stars in Andromeda galaxy(M31) (stars in M31 are sources for ML)

MW halo• Lensed image can’t be resolved with optical resolution(~10-8 arcsec) ⇒ only light curve is a signal

PBH• MW/M31 halos known to be ~ 1012Msun within a factor of 2(e.g. NFW models)• PBH has a peculiar velocity of ~200km/s• Need to monitor brightness of the same star as a functionof “time” (time domain astronomy)

RE =

r

4⇡GMPBH d(1c2d/ds )log (magnification)• ~1000 expected events for one night if PBH is DM in the
MW and M31 halo regions and if we can monitor 108 stars

Paczynski 86

time

PBH microlensing optical depth for a M31 star
10°5

Cumulative optical depth of PBH microlensing for a single star in M31

10°6

ø

⌦PBH
⌧=
⌦DM
10°7
Assumed

10°8

Z dL
0

⇢DM (d) 2
dd
⇡RE
MPBH

⌦PBH
= 1 and MW and M31 halo models
⌦DM

101

102

103

dL [kpc]
If we observe ~106 stars at any given moment, one star at least should be micro-lensed if PBHs are DM(a microlensing optical depth for a star in LMC or Galactic bulge is also similar, ~10-6)

Event rate of microlensing with light curve of a given timescale
Griest 91
source star

• Differential event rate [events/sec/sec]• Need to model velocity distribution of PBHs, e.g. the model that
reproduces the random virial motions

Z ds<latexit sha1_base64="t50srLfrMU0TjSTBckBCLHBH1tk=">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</latexit>

d
dtE

=

⌦PBH
⇢DM (dl )ddl
2⇡RE (ds , dl )
⌦DM 0
MPBH
✓
Z 1
Z ⇡/2
2
⇥
dv?
d✓ v?
cos ✓fDM (v? , ✓) D tE
0

=

⌦PBH
⇡
⌦DM

⇡/2

Z ds
0

⇢DM (dl )
ddl
MPBH

Z ⇡/2

⇡/2

4
d✓ v?
fDM (v? , ✓)2RE cos ✓v?

◆

v? =2RE cos ✓/tE

MW haloPBH microlensing event
rate
✓
◆
dL ✓E
tE ⇠
⇠ 34 minvPBH

MPBH
10 8 M

10°4

1/2 ✓

d2Nevent/dtobsd ln tFWHM [events/hrs]dL
100 kpc◆✓

vPBH
200 km/s◆ 1

MPBH = 10°12 MØ

Event rate for a single star in M31

10°5

source star

⌦PBH
=1
⌦DM

10°11 MØ10°10 MØ10°9 MØ
10°8 MØ
10°7 MØ

Mmoon ⇠ 10 8 M<latexit sha1_base64="lJH/jcB91yFHzcPhGqJnONCUnzY=">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</latexit>

1/2
RE / MPBH

lens (PBH)

10°6

10°7

10°8 °210Note t_E~200 days
for lens with M_sun
10°1
6min

100
60min
[hrs]

101

tFWHM
(time scale of ML light curve)
Event rate per unit obs. time and per a single star in M31 for a given timescale oflight curve: 10-6 = one event per one source million stars (we monitored ~108 stars)

observerSubaru Hyper Suprime-Cam (HSC)• Large aperture (8.2m)• Wide FoV = 9 full moon
• ~1G pixels (104 CCDs)• Most powerful instrument for
microlensing (before VRO LSST)

Kavli IPMU+NAOJ+Princeton+ASIAA

14

Microlensing search of stars in Andromeda Galaxy (M31)• In the northern hemisphere (notaccessible from VST, DES, LSST)• Large spiral galaxy• HSC FoV ~ entire M31(neither too closer nor too far!)• ~770kpc (𝜇~24.4), reachable
distance (not too far)!

Rule of the game: light curve timescale vs. cadencetLC
tvisit ⇠O(10)Design the ML observation satisfying the condition

flux of lensed star<latexit sha1_base64="oriof8OsXC4QGBJ5pmr1BUkuWM0=">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</latexit>

simulated light curveü As many stars to monitor as
possible (M31, GC bulge, LMC)

Δtvisit: frequency of visits (cadence)

ü “right” cadence for a target
light-curve timescale (short
time-scale cadence for lightmass PBH, and vice versa)

tLC: timescale of light curve
p
RE
MPBH
tLC ⇠
/
v
vhalo
<latexit sha1_base64="L6VnM2e+KD7+dK4q4X9xMTYR0Fw=">AAAC2HichVHNaxNBFH9Zv9L1o1EvgpfFUBEPYZKiST2VFqEHhTQ1bbFbwux2kg7dndnOTAJxGfAmevTiwZOCiPhnePEf8JA/QTxW8CLo2w9RD9W37Mx7v/d+7/1mJkgirg0hs4pz4uSp02eqc+7Zc+cvzNcuXtrUcqxC1g9lJNV2QDWLuGB9w03EthPFaBxEbCs4WM3yWxOmNJfigZkmbDemI8GHPKQGoUFN+wEbcZGyQ0GVotOb1jWD1Fexd2/V+prHnj9UNEx7BXjX2nRi/UTJxMgy5etDZdL7RUF3Zc1mNUW0TyNpreszsffHhEGtThqk3SFt4qGTGzpLS51bzdtes0TqUFpX1t6CD3sgIYQxxMBAgEE/Agoavx1oAoEEsV1IEVPo8TzPwIKL3DFWMaygiB7gOsJop0QFxllPnbNDnBLhr5DpwQL5RN6RI/KRvCefyfdje6V5j0zLFPeg4LJkMP/sysa3/7Ji3A3s/2b9U7OBIXRyrRy1JzmSnSIs+JNHL4427vQW0uvkNfmC+l+RGfmAJxCTr+GbddZ7CS4+wK9b9o53NluN5mKjtd6qL6+UT1GFq3ANbuB9t2EZ1qALfZw7gx+VamXOeeg8dp44T4tSp1JyLsNf5jz/CWEjuGQ=</latexit>

time from the start of observation

ü Shortest timescale is limited by
CCD readout (Subaru HSC
CCD has 30sec readout time,
while VRO LSST CCD has 2sec)ü Longest timescale = a durationof observation

~2 min
Hiroko Niikura (PhD 2016)
HSC dense-cadence observation of M31 (PI Takada, S14B)

•
•
•
•
•
•
•

Nov 2014
90sec exposure each (r-band)~35sec readout~190 exposures
No dithering
one clear night (seeing~0.5-0.6’’)
Also used g-band data (fromcommissioning run)Procedures: search for ML events
difference image (coadds of 3 exposures)

identify candidates in each diff. image⇒15,571

measure light curve (188 data points)
21.0
21.2

mag

21.4
21.6
21.8
22.0
22.2

0

5000

10000
15000
time [sec]

20000

25000

candidates with bump-like light curve⇒ 11,703

fitting of LC to the microlensing model
counts

2500
2000
1500
1000
500
0
−500
−1000
−1500
0

selection criteria
5000

10000

15000
time [sec]

20000

25000

⇒ 66

visual inspection ofindividual candidates…

23.69One possible microlensing candidate among ~15,000 variable stars …
compared to expected ~1000 events if PBH is DM
20

diff.

10

diff.-PSF

24.13

24.88
5

30.93

0

0

5000

10000

15000

20000

25000

time [second]

confirmed with the latest HSC
pipeline (based on the LSST stack)~1 hrObserved light curve of this candidate
Best-fit ML modelSunao Sugiyama(Kavli IPMU)

Niikura, MT+ 19, Nature AstronomymAB [mag]targetFlux [count]

ref.

15

Expectation number of ML events of a given timescale t_E

d⌧
NML,exp ' Ns ⇥ tobs ⇥⇥ ✏(tE )dtE<latexit sha1_base64="0zfC8QrgG0MRzkEuKRgZHChhSQE=">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</latexit># of source stars– depends ontarget gals (M31,
LMC, Galactic
bulge), tel. aperture,seeing, …

RE =<latexit sha1_base64="Y50rLPbOHO5RWB3feQvn1u6QU/s=">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</latexit>

r

RE
tE '
v

4⇡GMPBH dPBH (1
c2

total
observationtime(duration ofmonitoring
observation)

dPBH /ds )ML opticaldepth –
depends on thenumber ofcompact
objects (MS,WD, NS, BH) …
PBHs (assume,for M31, that alllenses for are
PBHs)<latexit sha1_base64="+8r1wN2lCbFkW8qcMxjDvB9mj4E=">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</latexit>

efficiency –depends on
cadenceand qualityof data

d⌧
⌦PBH
/
dtE
⌦DM

Subaru/HSC constraint on PBH abundance
MPBH [MØ]

10°15

10°10

10°5

100

Kepler
EROS/MACHO

CMB

10°2
10°3

ion

10°1
BH Evaporatf=≠PBH/≠DM

Mass fraction of PBHs to DM

Femto

10°4
10°5 15
10

Sunao Sugiyama(Kavli IPMU)

HSC 95%
upper
limit on PBH
abundnace
HSCCLM31
constraint(95%
limit)

obs > rSch (MPBH )tightest bound on PBH with MPBH=[1022,1028]g

1 HSC night ⇔ 2 years Kepler data

Finite source size + Wave effect1020

Niikura, MT+ (19, Nature Astronomy)

1025

MPBH [g]

1030

1035

Sunao is now
working on 2014,16, 20 datasets withthe latest HSC
pipelineSearch of PBH with microlensing

PBH
HSC M31 PBH
microlensing search

OGLE (Optical Gravitational Lensing
Experiment) for PBH searchOptical Gravitational Lensing Experiment (OGLE)• A long-term monitoring observation of Galactic bulge (1992- ). PI Prof. Udalski (Warsaw)• 1.3m Warsaw U. Telescope at Las Campanas, Chile5-year OGLE ML data: Mroz et al. Nature 2017
• 2622 ML events: the ML timescale distribution is provided
Mroz+ 17, Nature

OGLE 5yrs

Ns ' 5 ⇥ 107<latexit sha1_base64="DfUEmtVXu0p/rS+VVUyiSzzXLXw=">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</latexit>

Number of events

102

101

However, the individual
microlensing light curves are
not publicly available

100
10°1

100

101
tE [day]102

103Spatial and velocity structures of stars, WDs and NSs
Earth: rotation ~220km/s

disk stars (vertical)~30km/sbulge stars~100km/se.g., Bahcall 86;
Kent 92; Han &Gould 95, 96

MW dark matter halo
Dark matter (PBH)~220km/s

(old-days) Astronomers very smart!
Number of events per bin

OGLE data(2622 events)

Galactic bulge/disk models

MS

102
BD

10

<latexit sha1_base64="QoJdHU0JTORSpn9Qyw5tGVf51iA=">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</latexit>

tE =

10°1

Mlens
vrel

+ spatial and velocity
structures in the Galactic
bulge and disk regions

1
WD

100

RE
/
vrel

p

NS

100

101

102

ML LC timescale: tE [days]

Niikura, MT+PRD 19

Earth-mass scale PBH?
Number of events per bin

OGLE data(2622 events)

PBH

10

10

2

Galactic bulge/disk models

MS

MPBH = 9.5 £ 10°6 MØ
fPBH = 0.026

BD<latexit sha1_base64="QoJdHU0JTORSpn9Qyw5tGVf51iA=">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</latexit>

tE =

10°1

WD

NS

100

101

Mlens
vrel

+ spatial and velocity
structures in the Galactic
bulge and disk regions

1

100

RE
/
vrel

p

102

ML LC timescale: tE [days] Niikura, MT+ 19

P (MAS)

Assume both HSC and OGLE events are due to PBH … the two datasets are consistent (Sugiyama+21)

Sunao Sugiyama(Kavli IPMU)

100

10°1

fAS
fPBH

10°2
10°3

<latexit sha1_base64="ny92dZA9C+MDpcIufEu/TEm4cTc=">AAACknicSyrIySwuMTC4ycjEzMLKxs7BycXNw8vHLyAoFFacX1qUnBqanJ+TXxSRlFicmpOZlxpaklmSkxpRUJSamJuUkxqelO0Mkg8vSy0qzszPCympLEiNzU1Mz8tMy0xOLAEKxQvoxiSlpmfmVacW5iUWFSVWatVypcVXxxTlKgQ4edRyxaTmpSDJxQsoG+gZgIECJsMQylBmgIKAfIHlDDEMKQz5DMkMpQy5DKkMeQwlQHYOQyJDMRBGMxgyGDAUAMViGaqBYkVAViZYPpWhloELqLcUqCoVqCIRKJoNJNOBvGioaB6QDzKzGKw7GWhLDhAXAXUqMKgaXDVYafDZ4ITBaoOXBn9wmlUNNgPklkognQTRm1oQz98lEfydoK5cIF3CkIHQhdfNJQxpDBZgt2YC3V4AFgH5Ihmiv6xq+udgqyDVajWDRQavge5faHDT4DDQB3llX5KXBqYGzWbgAkaAIXpwYzLCjPQMzfQMA42UHZygUcHBIM2gxKABDG9zBgcGD4YAhlCgvZMZdjIcYjjMJMJkxeTI5AxRysQI1SPMgAKYfABif5ty</latexit>

AllowedAllowedregion
regionHSC
OGLE
HSC£OGLE

10°4
10°5
10°6 °11
10

10

°9

10
<latexit sha1_base64="xQcfza3BiyQAIuePKoqI2frxIQg=">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</latexit>

°7

10

]
AS [MØ[M
MMPBH
]

°5

10

Sugiyama, MT & Kusenko 21°3

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V( )P (MAS)Or this is a signature of axion DM?

='⇤4 [1 cos( /fa )]
m2a 2
m2a 4
+ ···
2
24fa2

self-interaction → leads to formation of axion “stars”

Schiappacasse & Hertzberg 18

100

10°1
10°2

MAS ⇠ MEarth , RAS ⌧ REarth

10°3

Allowed region
HSC
OGLE
HSC£OGLE

10°4
10°5
10°6 °11
10

10°9

10°7

10°5

MAS[MØ]

10°3

10°10

CAST

SN1987A

10HESS

Haloscopes°12|ga∞∞ |[GeV°1]

fAS<latexit sha1_base64="04ge0Z9BWb7F29CGq7MdtkGPZCQ=">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</latexit>

RAS > RE

(MAS)

10°14
Microlensing
95% allowed band
HSC
OGLE
HSC£OGLE

10°16
10°18

Sugiyama, MT, Kusenko 21

10°20
10°9

10°8

10°7

10°6

10°5
ma[eV]

10°4

10°3

10°2

10°1

Microlensing canprobe only
“compact” axion
stars (not diffuse
axion)

Vera C. Rubin Observatory: Legacy Survey of Space and Time (LSST: 2024 - 2037)•

6.4m aperture, FoV: 3.5 deg. ⇔ HSC: 1.5 deg.

•

Submitted an in-kind contribution proposal in order for us (scientists
in Japan) to join LSST (NAOJ: S. Miyazaki, Kavli IPMU: MT)•

Hopefully got ~40 PI’s if the proposal is approved (including ~40
Subaru nights)•

LSST (Legacy Survey of Space and Time) will start in 2024, till ~2036•

Including a monitoring observation of Galactic bulge over ~10yrs

LSST bulge observation (TBD)
•
•
•
•
•
•

read out: ~2sec (⇔HSC: 30sec), ugrizy (HSC: no u), ~10 yrs
A nominal plan of “Wide-Fast-Deep (WFD)” field (~18000 sq. deg.): each visit: 15sec×2, and then~800 visits in total in ugrizy for each field over 10yrs
ReX a+B2M+2
Q7 sq.
p`vBM;q6. bm`p2v 7QQiT`BMiX h?2 MmK#2` Q7 bi`b
Some6B;m`2“Deep Drilling
Field”BKT+i
for ~50
deg. i?2
in totalM/ ;HtB2b Bb Q#pBQmbHv p2`v b2MbBiBp2 iQ i?2 7QQiT`BMi- b `2 i?2 MmK#2` Q7 /Bb+Qp2`2/
Galacticplane, Galactic bulge, ….
hLPb Ub i?2b2 Q#D2+ib KQp2 p2`v bHQrHvVX h?2 6bi JB+`QH2MbBM; HbQ p`B2b bi`QM;Hv- b
Detailed
plan ofQM
bulge
observation
hasn’t yet
been
fully
finalized
i?Bbcadence
K2i`B+ /2T2M/b;H+iB+THM2 +Qp2`;2X
h?2
`B;?i
TM2H
Bb  xQQK@BM Q7 i?2 H27i
NASATM2HX
Roman Space Telescope (2026 launch expected)

6B;m`2 RdX a2`B2b Q7 bBKmHiBQMb i`vBM; /Bz2`2Mi #mH;2 Q#b2`pBM; bi`i2;B2bc i?2b2 p`v 7`QK
bBKTH2 HB;?i +Qp2`;2 Q7 i?2 ;H+iB+ #mH;2 M/ THM2 iQ ?2pB2` +Qp2`;2 Q7 i?2 #mH;2 Ur?BH2
KBMiBMBM; HB;?i +Qp2`;2 Q7 i?2 `2bi Q7 i?2 ;H+iB+ THM2VX

White paper of fundamental nature of DM with LSST
Community efforts: A. Drlica-Wagner+
arXiv:1902.01055• MW satellites and streams• Strong lens systems• Galaxy clusters• WIMP• Ultra-light DM• PBH

mass function: dn/d ln M

Byproduct of microlensing PBH search
ZAMS

WD

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dNevent
dtE

NS

BH

10°1

/

100

101

# of ML events: Nexp

106

10

4

10

3

0

M

2

4
RE
ddl nl (dl ) 4 f (v? )|v? =2RE /tE
tE<latexit sha1_base64="UbEJHIUuz/kLlx4V5WYv6TiNwDw=">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</latexit>

for events with v? =2RE
⌧ vtypical or tE
tE

2RE
vtypical102

initial or end mass: M [MØ]

105

/

Z ds

MS

tobs = 10 yrs
Ns = 2 £ 1010
¢ log10 tE = 0.1• Bulge, ~100km/s; disk, ~30km/s; halos, ~200km/s• If LIGO-Virgo BBHs are stellar-origined, longtimescale events are dominated by BH events of>10Msun

BH

WD• The event rate of microlensing depends on thespatial and velocity structures of lenses

NS• VRO LSST’s bulge search will find >10^4 BH events• Can also study wide-orbit binary BHs: binary fraction,
properties of binaries (separation, mass ratio, …)

102

total (power-law)• Microlensing events also enable to study
properties of stars, WDs, BDs and planets

total (Gaussian)
101 0
10

Abrams & MT 20
Toki & MT 21

101

102

tE [days]103

summary• Gravitational microlensing is very powerful to probe “compact, invisible objects” including PBH(and axion stars). Three windows that are worth further exploring• M_PBH~[10-15,10-10]Msun: all DM can be explained by PBH• M_PBH~10-5Msun (Earth mass): a possible candidate for Subaru M31 and OGLE microlensing events• M_PBH~10Msun: a counterpart of LIGO BBH GWs, might partly contribute DM (with mass fraction <0.1%)• We used the 8.2m Subaru HSC data of M31 to search for shotr timescale (~1hr) microlensing
events due to PBHs, and obtained the tightest upper bound on the abundance of PBHs
• 6 ultra short timescale events in the 5-year OGLE data (1.3m) indicate PBHs of Earth-massscales• The HSC event and the 6 OGLE events, although completely independent, are consistent• Bright future: Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) promises tomake significant progresses in microlensing studies with 10-year monitoring observation of the
Galactic bulge• Verify/falsify the Earth-mass PBH events