Introduction to observational astrophysics - S.D.Vergani - Rythme 1039 by Sonia Delaunay - Indico
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Rythme 1039 by Sonia Delaunay
S.D.Vergani
Introduction to observational astrophysics
GwM
The Electro-Magnetic (EM) counterpart quest
Detection
Identification
Characterization
S.D. Vergani - GwM
Detection : necessary …but no astrophysics
Identification : necessary + some astrophysics
Characterization : Top!
See Ghirlanda’s lectures
S.D. Vergani - GwM
LIGO-Virgo-Kagra events
Merger of binary system of neutron stars
NS-NS or BNS
Kilonova host galaxy
(KN) or globular cluster
Relativistic jet
(Gamma-ray burst)
EM counterparts
S.D. Vergani - GwM
LIGO-Virgo-Kagra events
Merger of binary system of neutron stars
NS-NS or BNS
Kilonova host galaxy
(KN) or globular cluster
Relativistic jet
Transients! (Gamma-ray burst)
S.D. Vergani - GwM
LIGO-Virgo-Kagra events
Merger of binary system of neutron stars
NS-NS or BNS
Kilonova host galaxy
(KN) or globular cluster
Relativistic jet
(Gamma-ray burst)
EM counterparts
S.D. Vergani - GwM
Credits: NASA S.D. Vergani - GwM
Credits: CHANDRA S.D. Vergani - GwM
Credits: NASA S.D. Vergani - GwM
Optical Filters
UV InfraRed
U B V R I J H K
u g r i z y J H K
S.D. Vergani - GwMGarcía-Vargas+13 S.D. Vergani - GwM
LIGO-Virgo-Kagra events
Merger of binary system of neutron stars
NS-NS or BNS
Kilonova host galaxy
(KN) or globular cluster
Relativistic jet
(Gamma-ray burst)
Knowledge based on models and 1 event
S.D. Vergani - GwMKilonova (KN)
blue component (faster, blue optical filters)
merger ejecta
red component
slower, neutron rich
Near-infrared filters
S.D. Vergani - GwMKilonova (KN)
blue component (faster, blue optical filters)
On-axis
θ Off-axis
merger ejecta
red component
slower, neutron rich
Near-infrared filters
what we see depends on our viewing angle
S.D. Vergani - GwMKilonova (KN)
Light-curve
Villar+17 and refs therein
GW170817/
S.D. Vergani - GwMKilonova (KN)
Light-curve
Villar+17 and refs therein
GW170817/
Apparent
Magnitude
S.D. Vergani - GwMKilonova (KN)
Light-curve
Villar+17 and refs therein
GW170817/
S.D. Vergani - GwMKilonova (KN)
Light-curve
Villar+17 and refs therein
GW170817/
Ejecta components
Velocity of the ejecta
Ejected Mass
S.D. Vergani - GwMKilonova (KN)
ESO-VLT/X-Shooter Pian et al. 2017, Nature
First spectral identification of a KN
Spectrum
• radioactive decay of
r-process nucleosynthesis
• BNS merger site for heavy
element production in the
Universe
GW170817/GRB170817
S.D. Vergani - GwMKilonova (KN)
blue component
radio KN
red component
afterglow
Inter-Stellar
Medium (ISM)
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
gamma rays
gamma rays
gamma rays
(fainter)
(fainter)
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
from X-rays to radio
relativistic jet
afterglow
ISM
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
ISM
what we see depends on our viewing angle
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
Credit: LIGO/Virgo Collaboration
GW170817/GRB170817
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
Makhathini et al. (2020)
GW170817/GRB170817
Relativistic, structured jet
S.D. Vergani - GwMhost galaxy
or globular cluster
Distance information used for H
Environment
Evolutionary channel studies
Credit: Space Telescope Science Institute
Credit: NASA
S.D. Vergani - GwMDetection S.D. Vergani - GwM
LIGO-Virgo-Kagra events
Mergers of binary systems of neutron stars
NS-NS or BNS
Sky map & Distance
S.D. Vergani - GwMLIGO-Virgo-Kagra events
Mergers of binary systems of neutron stars
NS-NS or BNS
Sky map & Distance
~10
S.D. Vergani - GwMLIGO-Virgo-Kagra events
Mergers of binary systems of neutron stars
NS-NS or BNS
Sky map & Distance
~10
S.D. Vergani - GwMLIGO-Virgo-Kagra events
Mergers of binary systems of neutron stars
NS-NS or BNS
Sky map & Distance
~10 deg
S.D. Vergani - GwMKilonova (KN)
adapted from Chornock+2019
~10
~10
~5*10
S.D. Vergani - GwMKilonova (KN)
Margutti+2018
S.D. Vergani - GwMDetection
I need observations that :
• cover the sky map
• reach the expected magnitudes
(in a “small” amount of time)
N.B.: The telescope time is limited!!!
S.D. Vergani - GwMField of view (FOV) S.D. Vergani - GwM
Field of view (FOV)
largest telescopes
VLT
Credit: ESO
S.D. Vergani - GwMField of view (FOV)
largest telescopes
VLT
Credit: ESO
very small telescopes
GWAC
Credit: SVOM
S.D. Vergani - GwMField of view (FOV)
Vera Rubin Telescope
~10 deg
Source : National Accelerator Laboratory
largest telescopes Survey telescopes
VLT
Credit: ESO
very small telescopes
GWAC
Credit: SVOM
S.D. Vergani - GwMfainter objects (fluxes):
intrinsically fainter or more distant
FOV
For the same amount of observing time
…and time matters!
S.D. Vergani - GwMfainter objects (fluxes):
intrinsically fainter or more distant
FOV
If we want to cover a large part of the sky
—> smaller telescopes
If we want to cover faint objects
—> larger telescopes
+ fast!
S.D. Vergani - GwMVera Rubin
2023 ->
S.D. Vergani - GwMKilonova (KN)
Margutti+2018
S.D. Vergani - GwMKilonova (KN)
blue component (faster, blue optical filters)
merger ejecta
red component
slower, neutron rich
Near-infrared filters
what we see depends on our viewing angle
S.D. Vergani - GwMKilonova (KN)
Margutti+2018
S.D. Vergani - GwMKilonova (KN)
Mochkovitch+2021
Lack of sensitive transient survey telescopes in the NIR
S.D. Vergani - GwMKilonova (KN)
Do we have instruments with
• wide enough FOV
• enough sensitive
• (and rapid)?
~10 ~10
~ maybe OK ~ OK
for very close ones for very close ones
~ NO ~ NO
for the rest for the far ones
~10 deg
OK
except for the far ones
S.D. Vergani - GwMKilonova (KN)
Do we have instruments with
• wide enough FOV
• enough sensitive
• (and rapid)?
~10 ~10
OK
except for the very far / red
~10 deg
LSST key role
for detection !
S.D. Vergani - GwMKilonova (KN)
P of success
Distance
Sky map extent
Viewing angle
(with on-axis caveat)
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
from X-rays to radio
relativistic jet
afterglow
ISM
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
z=0.1
z=0.2
• Viewing angle of the observer
• Jet structure
• Burst energetic
• Density of the inter-stellar medium
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
z=0.1
z=0.2
• On-axis: good but we must be fast
• Off-axis/high z: (extremely) faint
S.D. Vergani - GwMCredits: NASA S.D. Vergani - GwM
Credits: NASA S.D. Vergani - GwM
Relativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
z=0.1
z=0.2
• On-axis: good but we must be fast
• Off-axis: faint
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
z=0.1
z=0.2
If the localization is not precise
we need satellites capable of rapidly scanning the sky
S.D. Vergani - GwMXRT FoV: 23.6 x 23.6 arcmin
but ~ same exposure time
to reach the same flux values!
MXT FoV:
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
• weak bursts peak earlier
• lower frequencies —>
• lower frequencies peak later
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
radio scans
~102deg2 ~1h
• More time
• Faint but ~doable for small/intermediate off-axis angles
• large off-axis angles: good localization needed
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
gamma rays
gamma rays
gamma rays
(fainter)
(fainter)
S.D. Vergani - GwMCredits: NASA S.D. Vergani - GwM
FoV
Localization: ~10-10
FoV
Localization:
~
Gamma-ray emission helps!
S.D. Vergani - GwMFoV
Localization: ~10-10
FoV
Localization:
~
If on-axis & detected by Swift:
immediate X-rays & optical observations
Localization: arcsec precision!
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
On-axis with detection of gamma rays
best case for relativistic jet (& host galaxy) detection
BUT
We may miss the KN!
(and many aspects of jet physics)
S.D. Vergani - GwMRelativistic jet
(Gamma-ray burst)
Courtesy of Om Sharam Salafia
z=0.1
z=0.2
• On-axis: good but we must be fast
• Off-axis/high z: (extremely) faint
S.D. Vergani - GwMKilonova (KN)
adapted from Chornock+2019
~10
~10
~5*10
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
On-axis with detection of gamma rays
best case for relativistic jet (& host galaxy) detection
BUT
We may miss the KN!
(and many aspects of jet physics)
S.D. Vergani - GwMRelativistic jet (Gamma-ray burst)
P of success
Viewing angle
Sky map extent
Distance
Burst Energetic
ISM density
(excluding very high densities)
S.D. Vergani - GwMHost Galaxy
Credits: NASA
S.D. Vergani - GwMHost Galaxy
Belczynski
High chance to host a BNS merger
• massive (bright in NIR)
• some SFR (bright in UV-VIS)
Artale+2020
S.D. Vergani - GwMLIGO-Virgo-Kagra events
Mergers of binary systems of neutron stars
NS-NS or BNS
Sky map & Distance
~10
S.D. Vergani - GwMDetection
Galaxy surveys (all-sky)
with information on distance and magnitudes
We observe galaxies in the sky map by prioritizing:
• high probability sky map regions
• galaxies with expected distance and properties
S.D. Vergani - GwMHost Galaxy
Coulter+2017
GW170817 - NGC 4993
S.D. Vergani - GwMCoulter+2017
GW170817 - NGC 4993
S.D. Vergani - GwMHost Galaxy
Galaxy density
Luminosity Shirakata+2017
NIR Galaxy luminosity function
S.D. Vergani - GwMfainter objects (fluxes):
intrinsically fainter or more distant
missing galaxies
Coverage
completeness
Survey
apparent magnitudes
S.D. Vergani - GwMDetection
Galaxy surveys (all-sky)
with information on distance and magnitudes
We observe galaxies in the sky map by prioritizing:
• high probability sky map regions
• galaxies with expected distance and properties
Issue: Catalogue incompleteness
Large sky map/distant event —> large number of galaxies
Limited telescope time + limited time window to detect the KN
Issue: Observation incompleteness
S.D. Vergani - GwMexample from
~10 deg
With transient surveys
+
Dedicated galaxy observations
Ackley+2020
S.D. Vergani - GwMexample from
Ackley+2020
S.D. Vergani - GwMexample from
~10 deg
With transient surveys
+
Dedicated galaxy observations
Ackley+2020
S.D. Vergani - GwMIdentification S.D. Vergani - GwM
We need light-curve or spectrum
(supposing that models are correct)
faint object and/or many candidates
how can we identify that it is the counterpart?
large localization: many transients!
faint: just one point
radio: slow variability
S.D. Vergani - GwMKilonova (KN)
Do we have instruments with
• wide enough FOV
• enough sensitive
• (and rapid)?
~10 ~10
large localization: many transients!
~10 deg
LSST key role
for detection !
S.D. Vergani - GwMKilonova (KN) faint: just one point S.D. Vergani - GwM
Courtesy of Om Sharam Salafia
radio scans
~102deg2 ~1h
• Time association!
• Many transients
• Late time (faint at other wavelengths)
Multi-wavelength strategy with the best telescopes needed
Ok for few objets, not for many
S.D. Vergani - GwMKilonova (KN)
adapted from Chornock+2019
Spectrum only with largest telescopes
Ok for few objets, not for many
S.D. Vergani - GwMDetection : necessary …but no astrophysics
Identification : necessary + some astrophysics
H0, some spectral features, some rough properties of the KN ejecta
(blue component, velocity,…)
Characterization : Top!
See Ghirlanda’s lectures
S.D. Vergani - GwMDetection : necessary …but no astrophysics
si b l e !
m p o s
n o t i
g b u t u r n !
Identification n gi n : necessary + some c re t
astrophysics
h a ll e ie n t i fi
C spectral features, some
H , some
i g h sc
rough properties of the KN ejecta
0
ia l l y h g !
t e t
(blue component, velocity,…)
n t r y i n
Po l ke e p
e w i l
W
Characterization : Top!
See Ghirlanda’s lectures
S.D. Vergani - GwMThank you!
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