Francesca Calore

Francesca Calore
Gamma rays from Galactic
pulsars: high- and lowlatitude emission
NOW 2014
Conca Specchiulla, 8th September 2014
based on:
F. Calore, M. Di Mauro & F. Donato, arXiv:1406.2706
F. Calore, I. Cholis & C. Weniger, arXiv:1409.0042
The Isotropic Gamma-Ray Background (IGRB)
M. Razzano presentation about Fermi results !
Fermi all-sky gamma-ray map
0
0.05
Photon energy: 100 MeV - 10 GeV
0.15
0.35
Francesca Calore - University of Amsterdam
0.74
1.5
1
3.1
6.2
13
25
50
NOW 2014
The Isotropic Gamma-Ray Background (IGRB)
Fermi all-sky gamma-ray map
-
11 months data
@ high latitudes
|b|
10
Resolved
- Point
Sources
Galactic Diffuse
Emission
-
Resolved Point
Sources
Galactic Diffuse
Emission
Solar
photon &
0
-
0.05
CRs
background
CRs
Background &
solar
= photon
Energy range: 200 MeV - 100 GeV
0.15
0.35
Francesca Calore - University of Amsterdam
0.74
1.5
2
3.1
6.2
13
25
50
NOW 2014
The Isotropic Gamma-Ray Background (IGRB)
Fermi all-sky gamma-ray map
-
11 months data
@ high latitudes
|b|
10
Resolved
- Point
Sources
Galactic Diffuse
Emission
/E
2.41
-
Resolved Point
Sources
Galactic Diffuse
Emission
Solar
photon &
0
-
0.05
Abdo et al., PRL’10
CRs
background
CRs
Background &
solar
= photon
+ Anisotropy at small scales.
Energy range: 200 MeV - 100 GeV
0.15
0.35
Francesca Calore - University of Amsterdam
0.74
1.5
2
3.1
6.2
13
25
50
NOW 2014
The origin of the IGRB
Unresolved Point Sources
Diffuse Processes
Blazars
Most abundant population
of LAT detected sources
Contribution up to 10 - 20 %
Abdo et al., ApJ’10,
! Ajello et al., ApJ’12, Di Mauro et al, ’13
Non-blazars active galaxies
Few resolved members, but
large unresolved
population.
! Inoue, ApJ’11, Di Mauro et al, ApJ’13
!
Star-forming galaxies
Outnumber AGN in number
density, although 4
detected objects; ca 4 - 20%
! I. Tamborra presentation !
!
Galactic Pulsars
Second most abundant
population, but few % of the
diffuse flux.
Francesca Calore - University of Amsterdam
DM annihilation
In the Milky Way and in
other galaxies.Uncertainty
in the DM distribution.
!
e.g. Fornasa et al., MNRAS’13
!
UHECRs
E.M. cascade from interaction with CMB. Contribution from 1% to
50% .
! et al., PRD’09, Berezinsky et al., PLB, ‘10
Kalashev
!
Intergalactic shocks
Shock waves as electrons
accelerators, then IC on
CMB; ca. 10% of IGRB.
!
Keshet et al., ApJ’03, Gabici & Blasi, AP’03
3
NOW 2014
The origin of the IGRB
Unresolved Point Sources
Diffuse Processes
Blazars
Most abundant population
of LAT detected sources
Contribution up to 10 - 20 %
Abdo et al., ApJ’10,
! Ajello et al., ApJ’12, Di Mauro et al, ’13
Non-blazars active galaxies
Few resolved members, but
large unresolved
population.
! Inoue, ApJ’11, Di Mauro et al, ApJ’13
!
Star-forming galaxies
Outnumber AGN in number
density, although 4
detected objects; ca 4 - 20%
! I. Tamborra presentation !
!
Galactic Pulsars
Second most abundant
population, but few % of the
diffuse flux.
Francesca Calore - University of Amsterdam
DM annihilation
In the Milky Way and in
other galaxies.Uncertainty
in the DM distribution.
!
e.g. Fornasa et al., MNRAS’13
!
UHECRs
E.M. cascade from interaction with CMB. Contribution from 1% to
50% .
! et al., PRD’09, Berezinsky et al., PLB, ‘10
Kalashev
!
Intergalactic shocks
Shock waves as electrons
accelerators, then IC on
CMB; ca. 10% of IGRB.
!
Keshet et al., ApJ’03, Gabici & Blasi, AP’03
3
NOW 2014
Young & Millisecond pulsars
dP/dt vs P for the ATNF catalog Pulsars and MSPs
10-11
ATNF MSPs
10-12
10
-13
10
-14
ATNF young Pulsars
dP/dt [s/s]
10-15
10-16
Fermi-LAT MSPs
Fermi-LAT Pulsars
P = 0.015 s
MSPs
10-17
10-18
Young
Pulsars
10-19
10
-20
10-21
10-22 -3
10
10-2
10-1
100
P [s]
Francesca Calore - University of Amsterdam
4
101
• Pulsars are rapidly
spinning neutron stars.
!
• Pulsars divided into young
Pulsars (P>15 ms) and
Millisecond Pulsars
(MSPs) .
!
• ATNF catalog: about 2000
sources (132 MSPs)
!
• Fermi-LAT second Pulsars
catalog (2FPC) with 117
sources (40 MSPs and 77
young objects).
NOW 2014
Pulsar gamma-ray emission
•
•
•
Gamma rays from the conversion of rotational kinetic
energy.
The initial rotation period slows down for magneticdipole braking.
The slow down is measured by the period derivative:
!
!
!
•
The spin-down luminosity, namely the loss energy rate
is:
!
!
•
A fraction of the spin-down luminosity is converted
into gamma rays with a given efficiency:
Francesca Calore - University of Amsterdam
5
NOW 2014
Pulsar gamma-ray emission
•
•
•
Gamma rays from the conversion of rotational kinetic
energy.
The initial rotation period slows down for magneticdipole braking.
The slow down is measured by the period derivative:
!
!
!
•
(1) magnetic field
(2)rotation period
The spin-down luminosity, namely the loss energy rate
is:
!
!
•
A fraction of the spin-down luminosity is converted
into gamma rays with a given efficiency:
(1) luminosity efficiency
Francesca Calore - University of Amsterdam
5
NOW 2014
Parameter distributions (1)
Radio measurements from ATNF catalog (132 sources)
B distribution N(B) of ATNF catalog MSPs
ATNF Distr
Log10 Gauss.
hlog10 (B/G)i = 8.27
log10 B
= 0.30
ATNF distr.
Gauss.
Log10 Gauss.
15
NN(P)
(P )
NN(B)
(B)
15
P distribution N(P) of ATNF catalog MSPs
10
hlog10 (P/s)i =
5
5
0
0
8
log10 P
10
0.002
9
0.004
0.006
2.54
= 0.19
0.008
0.01
P [s]
[G]
logLog10(B)(B/G)
P [s]
10
(1)magnetic field
(2)rotation period
Novelty!!
Francesca Calore - University of Amsterdam
6
NOW 2014
Parameter distributions (1)
Radio measurements from ATNF catalog (132 sources)
r distribution N(r) of ATNF catalog MSPs
z distribution N(z) of ATNF catalog MSPs
40
25
20
ATNF distr.
Gauss.
Exp.
hzi = 0 kpc
NN(r)(r)
NN(z)
(z)
hri = 7.42 kpc
30
z0 = 0.67 kpc
15
10
ATNF distr.
Gauss.
Exp.
r0 = 1.03 kpc
20
10
5
0
0
-1.5
-1
-0.5
0
0.5
1
1.5
3
z [kpc]
5
6
7
8
9
10
11
12
13
r [kpc]
r[kpc]
z[kpc]
(3)z distribution
(4)r distribution
distance from the
Galactic plane
Francesca Calore - University of Amsterdam
4
projected distance from
the Galactic center
7
NOW 2014
Parameter distributions (2)
Gamma-ray measurements
from Fermi-LAT 2PC (40 sources)
L (dE/dt)
10
38
1037
LL [erg/s]
[erg/s]
10
36
Band
= 0.095, = 1
Fermi-LAT MSPs
Fermi-LAT UL
(1) luminosity
efficiency
1035
1034
ỷ is the conversion efficiency.
1033
Benchmark:
1032
↵ = 1 , ⌘ = 0.095
1031
Empirical uncertainty band:
1030
1031
⌘ ={0.015, 0.65}
1032
1033
1034
1035
1036
1037
˙dE/dt [erg/s]
E[erg/s]
• The scatter of the data points does not allow a statistically robust correlation.
• We derive 95% C.L. upper limits on the gamma-ray flux of a sample of 20 sources nondetected by the Fermi-LAT.
• 20 selected sources in the ATNF catalog are the ones (with |b| > 10 ) expected to be the
most powerful gamma-ray emitters if standard values of ử = 1 and ỷ =0.1 are assumed.
Francesca Calore - University of Amsterdam
8
NOW 2014
Parameter distributions (2)
Gamma-ray measurements from Fermi-LAT 2PC (40 sources)
Spectral energy distribution
of observed sources
distribution N( ) of MSPs in the 2FPC
15
h i = 1.29
Log10(Ecut) distribution N(Log10(Ecut)) of MSPs in the 2FPC
N (Ecut )
= 0.37
10
˜cut
E
Fermi-LAT
Gauss.
= 0.18
N(Ecut)
10
N( )
N( )
˜cut i = 3.38
hE
Fermi-LAT
Gauss.
5
5
0
0
0.5
1
1.5
3
2
3.5
log10 (Ecut /MeV)
Log10(Ecut [MeV])
(3)cutoff energy
(2)spectral index
Francesca Calore - University of Amsterdam
9
NOW 2014
MSP gamma-ray sky
Simulated MSPs distribution
For each simulated source we derive:
- the position: r, z
- the gamma-ray luminosity:
˙
• P, B ! E
2
⌘
!
L
!
S
⌘
L
/(4⇡d
)
• a
• a , Ecut ! F
• Fermi-LAT source sensitivity
Francesca Calore - University of Amsterdam
10
Fermi-LAT Coll. arXiv:1305.8345
NOW 2014
MSP gamma-ray sky
Simulated MSPs distribution
For each simulated source we derive:
- the position: r, z
- the gamma-ray luminosity:
˙
• P, B ! E
2
⌘
!
L
!
S
⌘
L
/(4⇡d
)
• a
• a , Ecut ! F
• Fermi-LAT source sensitivity
Fermi-LAT Coll. arXiv:1305.8345
Detected or
non-detected source?
A. Resolved MSPs (max 39)
B. Unresolved MSPs
Total of about 1000 - 1500 simulated sources for 1000 MC simulations.
Francesca Calore - University of Amsterdam
10
NOW 2014
MSP gamma-ray sky
Simulated MSPs distribution
Resolved MSPs counterpart
Francesca Calore - University of Amsterdam
11
NOW 2014
MSP gamma-ray sky
Simulated MSPs distribution
Unresolved MSPs counterpart
Francesca Calore - University of Amsterdam
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NOW 2014
High-latitude emission
Unresolved
flux in the high-latitude region
Calore, Di Mauro,
DonatoMSPs
(2014)
E2 dN/dE [GeV/cm2/s/sr]
10
1 Band
Average
Ackermann 2012
-3
10-4
10-5
10-6
10-7
10
|b| > 10
-8
10-1
100
101
102
103
E [GeV]
1000 MC realisations of MSPs population. Uncertainty band due
to parameter distributions errors and LAT sensitivity.
Francesca Calore - University of Amsterdam
12
NOW 2014
High-latitude emission
Unresolved
flux in the high-latitude region
Calore, Di Mauro,
DonatoMSPs
(2014)
E2 dN/dE [GeV/cm2/s/sr]
10
1 Band
Average
Ackermann 2012
-3
10-4
10-5
10-6
10-7
|b| >
MSPs contribution to the IGRB
is 10
1
2
about 0.1%
the
peak (210GeV)
and 103
10-1
100 - 0.9% at 10
E [GeV]
about 0.02% - 0.13% of the
integrated IGRB intensity.
Uncertainty band of O(10) at all energies.
10-8
Francesca Calore - University of Amsterdam
12
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Claim of a gamma-ray excess emission over standard astrophysical
background in the inner region of the Galaxy:
0
0.05
0.15
0.35
0.74
1.5
3.1
6.2
13
25
Francesca Calore - University of Amsterdam
50
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Claim of a gamma-ray excess emission over standard astrophysical
background in the inner region of the Galaxy:
•
Galactic Center region: |b|  3.5 & |l|  3.5
Abazajian et al. (2014), Macias & Gordon (2013), etc.
Macias & Gordon (2013)
0
0.05
0.15
0.35
0.74
1.5
3.1
6.2
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Francesca Calore - University of Amsterdam
50
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Claim of a gamma-ray excess emission over standard astrophysical
background in the inner region of the Galaxy:
•
Galactic Center region: |b|  3.5 & |l|  3.5
Abazajian et al. (2014), Macias & Gordon (2013), etc.
•
Inner Galaxy: inner tens of degrees about the GC, |b| > 1
Daylan et al. (2014), Huang et al. (2013), Hooper & Slatyer (2013), etc.
Calore, Cholis, Weniger (2014)
0
0.05
0.15
0.35
0.74
1.5
3.1
6.2
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25
Francesca Calore - University of Amsterdam
50
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
E 2 dN/dE [GeV cm−2 s−1 sr−1 ]
10−5
DM τ + τ −
GC excess spectrum with
stat. and corr. syst. errors
broken PL
PL with exp. cutoﬀ
DM ¯bb
10−6
10−7
10−8
100
101
E [GeV]
102
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
14
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
E 2 dN/dE [GeV cm−2 s−1 sr−1 ]
10−5
DM τ + τ −
GC excess spectrum with
stat. and corr. syst. errors
broken PL
PL with exp. cutoﬀ
DM ¯bb
10−6
10−7
10−8
100
101
E [GeV]
102
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
14
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
E 2 dN/dE [GeV cm−2 s−1 sr−1 ]
10−5
DM τ + τ −
GC excess spectrum with
stat. and corr. syst. errors
broken PL
PL with exp. cutoﬀ
DM ¯bb
10−6
10−7
10−8
100
101
E [GeV]
102
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
14
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
E 2 dN/dE [GeV cm−2 s−1 sr−1 ]
10−5
DM τ + τ −
GC excess spectrum with
stat. and corr. syst. errors
broken PL
PL with exp. cutoﬀ
DM ¯bb
10−6
10−7
10−8
100
101
E [GeV]
102
Can young pulsars and MSPs explain the GC excess emission?
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
14
NOW 2014
Pulsars low-latitude emission
Inner Galaxy
10  |b|  20
|b|  3.5 & |l|  3.5
Galactic Center
Calore, Di Mauro, Donato (2014)
Francesca Calore - University of Amsterdam
15
NOW 2014
Pulsars low-latitude emission
Inner Galaxy
10  |b|  20
|b|  3.5 & |l|  3.5
Galactic Center
Pulsars and MSPs
might
explain
up
to
5% of the GeV excess in the Inner Galaxy and
8% in the Galactic Center region.
Calore, Di Mauro, Donato (2014)
Francesca Calore - University of Amsterdam
15
NOW 2014
Pulsars interpretation of the GeV excess
✓t
1. Spectral argument
Power-law with exponential cutoff is consistent with
observed pulsar gamma ray properties.
✓t
2. Luminosity (flux) argument
The emission from unresolved pulsars can account for
at most 10% of the excess emission in both the Galactic
Center and Inner Galaxy regions.
3. Morphology argument
?
The source distribution is well compatible with a disklike population. Nevertheless, it is possible to have a
“bulge” component. It is anyhow unlikely that it
extends up to 10 degrees in latitude.
e.g Cholis, Hooper, Linden [arXiv:1407.5625]
Francesca Calore - University of Amsterdam
16
NOW 2014
Conclusions
✓
Up-to-date and systematic analysis of MSPs population
properties from radio (ATNF catalog) to gamma rays (Fermi-LAT).
✓
MSPs are a marginal component of the IGRB: 0.02% - 0.13% within
an uncertainty of O(10).
✓
MSPs are also a negligible contributor to the gamma-ray
anisotropy signal measured by the Fermi-LAT, thus indicating that
this should be dominated by other sources.
✓
At low latitudes, the contribution from both young pulsars and
MSPs can explain up to about 10% of the excess emission
measured in the inner part of the Galaxy.
✓
The MSPs interpretation of the Fermi-LAT GeV excess is nowadays
in tension with spectral and morphological properties of the MSPs
population as we model it from radio and gamma-ray observations.
Francesca Calore - University of Amsterdam
17
NOW 2014
Conclusions
✓
Up-to-date and systematic analysis of MSPs population
properties from radio (ATNF catalog) to gamma rays (Fermi-LAT).
✓
MSPs are a marginal component of the IGRB: 0.02% - 0.13% within
an uncertainty of O(10).
✓
MSPs are also a negligible contributor to the gamma-ray
anisotropy signal measured by the Fermi-LAT, thus indicating that
this should be dominated by other sources.
✓
At low latitudes, the contribution from both young pulsars and
MSPs can explain up to about 10% of the excess emission
measured in the inner part of the Galaxy.
✓
The MSPs interpretation of the Fermi-LAT GeV excess is nowadays
in tension with spectral and morphological properties of the MSPs
population as we model it from radio and gamma-ray observations.
Thanks for your attention!! :)
Francesca Calore - University of Amsterdam
17
NOW 2014
Backup slides
Francesca Calore - University of Amsterdam
18
NOW 2014
The origin of the IGRB
Unresolved Point Sources
Diffuse Processes
Blazars
Most abundant population
of LAT detected sources
Contribution up to 10 - 20 %
Abdo et al., ApJ’10,
! Ajello et al., ApJ’12, Di Mauro et al, ’13
Non-blazars active galaxies
Few resolved members, but
large unresolved
population.
! Inoue, ApJ’11, Di Mauro et al, ApJ’13
!
Star-forming galaxies
Outnumber AGN in number
density, although 4
detected objects; ca 4 - 20%
! I. Tamborra presentation !
!
Galactic Pulsars
Second most abundant
population, but few % of the
diffuse flux.
Francesca Calore - University of Amsterdam
DM annihilation
In the Milky Way and in
other galaxies.Uncertainty
in the DM distribution.
!
!"
##
! $%&
'(
)"*
!
!
Potential to be one
of the most efficient future means of
probing thermally
produced DM.
Bringmann, Calore, Di Mauro, Donato, PRD’13
3
NOW 2014
Gamma-ray anistropy
Anisotropy of the IGRB recently measured by the Fermi-LAT
Collab. in the multipole range ` = 155 504 :
Ackermann et al.,PRD’12
• 22 month of data
• Energy range: 1
50 GeV
• Region: |b| > 30 (high latitudes)
!
➡ Anisotropy detected at small scales, `
155 (✓ 
➡ Consistent with Poisson-like anisotropy from an
2)
unresolved population of point-like sources.
➡ No-energy dependence
Cp
=
9.05
±
0.84
⇥
10
hIi2
Francesca Calore - University of Amsterdam
6
sr
s
18
= 2.40 ± 0.07
NOW 2014
Gamma-ray anistropy from MSPs
Calore, Di Mauro, Donato (2014)
The 1σ upper limit angular power from the unresolved MSPs
together with Fermi-LAT data.
Francesca Calore - University of Amsterdam
18
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
1. to generate counts map of Fermi-LAT data for the region of interest
and subtract/mask point sources (PSC Fermi catalogs);
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
A. CRs (p) vs ISM:
⇡ 0emission.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
0
A. CRs (p) vs ISM: ⇡ emission.
B. CRs (e) vs ISM: Bremsstrahlung.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
A.
B.
C.
0
CRs (p) vs ISM: ⇡ emission.
CRs (e) vs ISM: Bremsstrahlung.
CRs (e) vs ISRF: ICS emission.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
A.
B.
C.
0
CRs (p) vs ISM: ⇡ emission.
CRs (e) vs ISM: Bremsstrahlung.
CRs (e) vs ISRF: ICS emission.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Possible strategy applied to single out the excess:
2. to perform a pixel based maximum likelihood analysis on the
counts map, by fitting the data (bin-by-bin) with a sum of
spatial templates.
1. Galactic diffuse emission
A.
B.
C.
0
CRs (p) vs ISM: ⇡ emission.
CRs (e) vs ISM: Bremsstrahlung.
CRs (e) vs ISRF: ICS emission.
2. Isotropic diffuse emission;
3. Fermi Bubbles brightness-uniform
emission;
4. Spherically symmetric template
for the GC emission.
Francesca Calore - University of Amsterdam
13
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
2  |b|  20 & |l|  20
Longitude dependence of the
different components in a
latitude strip.
Energy spectra of different
components from the template
fit to the data.
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
14
NOW 2014
Low-latitude emission:
the Fermi-LAT GeV excess
Spectrum of the GCE emission
with statistical and background model systematics.
Calore, Cholis, Weniger (2014)
Francesca Calore - University of Amsterdam
15
NOW 2014

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