Post on 29-Jul-2022
Gamma rays from Galactic pulsars: high- and low-
latitude emission
Francesca Calore
NOW 2014 Conca Specchiulla, 8th September 2014
F. Calore, M. Di Mauro & F. Donato, arXiv:1406.2706 F. Calore, I. Cholis & C. Weniger, arXiv:1409.0042
based on:
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50
Fermi all-sky gamma-ray map
Photon energy: 100 MeV - 10 GeV
The Isotropic Gamma-Ray Background (IGRB)
Francesca Calore - University of Amsterdam NOW 20141
M. Razzano presentation about Fermi results !
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50Energy range: 200 MeV - 100 GeV
Resolved Point Sources
Galactic Diffuse Emission
--
- CRs Background & solar photon
Fermi all-sky gamma-ray map
Solar photon & CRs background
-
=
-
-
11 months data @ high latitudes
|b| � 10�
Galactic Diffuse Emission
Resolved Point Sources
The Isotropic Gamma-Ray Background (IGRB)
Francesca Calore - University of Amsterdam NOW 20142
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50Energy range: 200 MeV - 100 GeV
Resolved Point Sources
Galactic Diffuse Emission
--
- CRs Background & solar photon
Fermi all-sky gamma-ray map
Abdo et al., PRL’10
/ E�2.41
+ Anisotropy at small scales.
Solar photon & CRs background
-
=
-
-
11 months data @ high latitudes
|b| � 10�
Galactic Diffuse Emission
Resolved Point Sources
The Isotropic Gamma-Ray Background (IGRB)
Francesca Calore - University of Amsterdam NOW 20142
Unresolved Point Sources Diffuse ProcessesBlazars
Most abundant population of LAT detected sources Contribution up to 10 - 20 % !
Non-blazars active galaxies Few resolved members, but large unresolved population. !
!Star-forming galaxies
Outnumber AGN in number density, although 4 detected objects; ca 4 - 20% !!
Galactic Pulsars Second most abundant population, but few % of the diffuse flux.
DM annihilation In the Milky Way and in other galaxies.Uncertainty in the DM distribution. !!UHECRs E.M. cascade from interaction with CMB. Contribution from 1% to 50% . !!Intergalactic shocks Shock waves as electrons accelerators, then IC on CMB; ca. 10% of IGRB. !
Abdo et al., ApJ’10, Ajello et al., ApJ’12, Di Mauro et al, ’13
Inoue, ApJ’11, Di Mauro et al, ApJ’13
I. Tamborra presentation !
Kalashev et al., PRD’09, Berezinsky et al., PLB, ‘10
Keshet et al., ApJ’03, Gabici & Blasi, AP’03
e.g. Fornasa et al., MNRAS’13
The origin of the IGRB
Francesca Calore - University of Amsterdam NOW 20143
Unresolved Point Sources Diffuse ProcessesBlazars
Most abundant population of LAT detected sources Contribution up to 10 - 20 % !
Non-blazars active galaxies Few resolved members, but large unresolved population. !
!Star-forming galaxies
Outnumber AGN in number density, although 4 detected objects; ca 4 - 20% !!
Galactic Pulsars Second most abundant population, but few % of the diffuse flux.
DM annihilation In the Milky Way and in other galaxies.Uncertainty in the DM distribution. !!UHECRs E.M. cascade from interaction with CMB. Contribution from 1% to 50% . !!Intergalactic shocks Shock waves as electrons accelerators, then IC on CMB; ca. 10% of IGRB. !
Abdo et al., ApJ’10, Ajello et al., ApJ’12, Di Mauro et al, ’13
Inoue, ApJ’11, Di Mauro et al, ApJ’13
I. Tamborra presentation !
Kalashev et al., PRD’09, Berezinsky et al., PLB, ‘10
Keshet et al., ApJ’03, Gabici & Blasi, AP’03
e.g. Fornasa et al., MNRAS’13
The origin of the IGRB
Francesca Calore - University of Amsterdam NOW 20143
• 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).
10-22
10-21
10-20
10-19
10-18
10-17
10-16
10-15
10-14
10-13
10-12
10-11
10-3 10-2 10-1 100 101
dP/d
t [s/
s]
P [s]
dP/dt vs P for the ATNF catalog Pulsars and MSPs
ATNF MSPsATNF young Pulsars
Fermi-LAT MSPsFermi-LAT Pulsars
P = 0.015 s
Young & Millisecond pulsars
MSPs
Young Pulsars
Francesca Calore - University of Amsterdam NOW 20144
• Gamma rays from the conversion of rotational kinetic energy.
• The initial rotation period slows down for magnetic-dipole 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:
Pulsar gamma-ray emission
Francesca Calore - University of Amsterdam NOW 20145
• Gamma rays from the conversion of rotational kinetic energy.
• The initial rotation period slows down for magnetic-dipole 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:
Pulsar gamma-ray emission
Francesca Calore - University of Amsterdam NOW 20145
(1) magnetic field (2)rotation period
(1) luminosity efficiency
0
5
10
15
8 9
N(B
)
Log10(B) [G]
B distribution N(B) of ATNF catalog MSPs
ATNF DistrLog10 Gauss.
0
5
10
15
0.002 0.004 0.006 0.008 0.01
N(P
)
P [s]
P distribution N(P) of ATNF catalog MSPs
ATNF distr.Gauss.
Log10 Gauss.
Parameter distributions (1)
Francesca Calore - University of Amsterdam NOW 20146
(1)magnetic field (2)rotation period
Radio measurements from ATNF catalog (132 sources)
Novelty!!
hlog10
(B/G)i = 8.27
�log10 B = 0.30
hlog10
(P/s)i = �2.54
�log10 P = 0.19
P [s]N(P
)
N(B
)
log10(B/G)
Parameter distributions (1)
Francesca Calore - University of Amsterdam NOW 20147
(3)z distribution (4)r distribution
Radio measurements from ATNF catalog (132 sources)
0
10
20
30
40
3 4 5 6 7 8 9 10 11 12 13
N(r)
r [kpc]
r distribution N(r) of ATNF catalog MSPs
ATNF distr.Gauss.
Exp.
0
5
10
15
20
25
-1.5 -1 -0.5 0 0.5 1 1.5
N(z
)
z [kpc]
z distribution N(z) of ATNF catalog MSPs
ATNF distr.Gauss.
Exp.
distance from the Galactic plane
projected distance from the Galactic center
hri = 7.42 kpc
r0 = 1.03 kpc
hzi = 0kpc
z0 = 0.67 kpc
N(z)
N(r)
r[kpc]z[kpc]
Parameter distributions (2)
Francesca Calore - University of Amsterdam NOW 20148
Gamma-ray measurements from Fermi-LAT 2PC (40 sources)
1030
1031
1032
1033
1034
1035
1036
1037
1038
1031 1032 1033 1034 1035 1036 1037
L a [e
rg/s
]
dE/dt [erg/s]
La(dE/dt)
Band¡ = 0.095, _ = 1
Fermi-LAT MSPsFermi-LAT UL
(1) luminosity efficiency
• 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 non-
detected by the Fermi-LAT. • 20 selected sources in the ATNF catalog are the ones (with ) expected to be the
most powerful gamma-ray emitters if standard values of ử = 1 and ỷ =0.1 are assumed.
ỷ is the conversion efficiency.
E[erg/s]
L�[erg/s]
|b| > 10�
↵ = 1 , ⌘ = 0.095Benchmark:
Empirical uncertainty band:⌘ = 0.015, 0.65{ }
Parameter distributions (2)
Francesca Calore - University of Amsterdam NOW 20149
(2)spectral index
Gamma-ray measurements from Fermi-LAT 2PC (40 sources)
0
5
10
15
0.5 1 1.5 2
N(K
)
K
K distribution N(K) of MSPs in the 2FPC
Fermi-LATGauss.
0
5
10
3 3.5
N(E
cut)
Log10(Ecut [MeV])
Log10(Ecut) distribution N(Log10(Ecut)) of MSPs in the 2FPC
Fermi-LATGauss.
h�i = 1.29
�� = 0.37hEcuti = 3.38
�Ecut= 0.18
(3)cutoff energy
Spectral energy distribution of observed sources
�
N(�
)
log10(Ecut/MeV)
N(E
cut)
MSP gamma-ray sky
Francesca Calore - University of Amsterdam NOW 2014
Simulated MSPs distribution
10
For each simulated source we derive: - the position: r, z - the gamma-ray luminosity:
• P, B • a • a • Fermi-LAT source sensitivity
! E
� , Ecut ! F�
⌘ ! L� ! S� ⌘ L�/(4⇡d2)
Fermi-LAT Coll. arXiv:1305.8345
MSP gamma-ray sky
Francesca Calore - University of Amsterdam NOW 2014
Simulated MSPs distribution
10
For each simulated source we derive: - the position: r, z - the gamma-ray luminosity:
• P, B • a • a • Fermi-LAT source sensitivity
! E
� , Ecut ! F�
⌘ ! L� ! S� ⌘ L�/(4⇡d2)
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.
MSP gamma-ray sky
Francesca Calore - University of Amsterdam NOW 2014
Simulated MSPs distribution
11
Resolved MSPs counterpart
MSP gamma-ray sky
Francesca Calore - University of Amsterdam NOW 2014
Simulated MSPs distribution
11
Unresolved MSPs counterpart
1000 MC realisations of MSPs population. Uncertainty band due to parameter distributions errors and LAT sensitivity.
10-8
10-7
10-6
10-5
10-4
10-3
10-1 100 101 102 103
E2 dN
/dE
[GeV
/cm
2 /s/s
r]
E [GeV]
Unresolved MSPs flux in the high-latitude region
1m BandAverage
Ackermann 2012
High-latitude emission
Francesca Calore - University of Amsterdam NOW 201412
|b| > 10�
Calore, Di Mauro, Donato (2014)
10-8
10-7
10-6
10-5
10-4
10-3
10-1 100 101 102 103
E2 dN
/dE
[GeV
/cm
2 /s/s
r]
E [GeV]
Unresolved MSPs flux in the high-latitude region
1m BandAverage
Ackermann 2012
Calore, Di Mauro, Donato (2014)
High-latitude emission
Francesca Calore - University of Amsterdam NOW 201412
|b| > 10�MSPs contribution to the IGRB is about 0.1% - 0.9% at the peak (2 GeV) and
about 0.02% - 0.13% of the integrated IGRB intensity. Uncertainty band of O(10) at all energies.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50
Claim of a gamma-ray excess emission over standard astrophysical background in the inner region of the Galaxy:
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50
Claim of a gamma-ray excess emission over standard astrophysical background in the inner region of the Galaxy:
Macias & Gordon (2013)
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.
Claim of a gamma-ray excess emission over standard astrophysical background in the inner region of the Galaxy:
• Galactic Center region:
• Inner Galaxy: inner tens of degrees about the GC, Daylan et al. (2014), Huang et al. (2013), Hooper & Slatyer (2013), etc.
|b| > 1�
|b| 3.5� & |l| 3.5�
Abazajian et al. (2014), Macias & Gordon (2013), etc.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
0 0.05 0.15 0.35 0.74 1.5 3.1 6.2 13 25 50
Calore, Cholis, Weniger (2014)
100 101 102
E [GeV]
10−8
10−7
10−6
10−5
E2dN/d
E[G
eVcm
−2s−
1sr
−1]
broken PL
PL with exp. cutoff
DM bb
DM τ+τ−
GC excess spectrum withstat. and corr. syst. errors
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201414
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
100 101 102
E [GeV]
10−8
10−7
10−6
10−5
E2dN/d
E[G
eVcm
−2s−
1sr
−1]
broken PL
PL with exp. cutoff
DM bb
DM τ+τ−
GC excess spectrum withstat. and corr. syst. errors
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201414
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
100 101 102
E [GeV]
10−8
10−7
10−6
10−5
E2dN/d
E[G
eVcm
−2s−
1sr
−1]
broken PL
PL with exp. cutoff
DM bb
DM τ+τ−
GC excess spectrum withstat. and corr. syst. errors
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201414
Parametric fits to the spectrum of the GCE emission.
Calore, Cholis, Weniger (2014)
100 101 102
E [GeV]
10−8
10−7
10−6
10−5
E2dN/d
E[G
eVcm
−2s−
1sr
−1]
broken PL
PL with exp. cutoff
DM bb
DM τ+τ−
GC excess spectrum withstat. and corr. syst. errors
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201414
Can young pulsars and MSPs explain the GC excess emission?
Calore, Cholis, Weniger (2014)
Pulsars low-latitude emission
Francesca Calore - University of Amsterdam NOW 201415
Galactic Center
Inner Galaxy
|b| 3.5� & |l| 3.5�
10� |b| 20�
Calore, Di Mauro, Donato (2014)
Francesca Calore - University of Amsterdam NOW 201415
Galactic Center
Inner Galaxy
|b| 3.5� & |l| 3.5�
10� |b| 20�
Calore, Di Mauro, Donato (2014)
Pulsars and MSPs might explain up to 5% of the GeV excess in the Inner Galaxy and
8% in the Galactic Center region.
Pulsars low-latitude emission
1. Spectral argument
Power-law with exponential cutoff is consistent with observed pulsar gamma ray properties.
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 disk-like population. Nevertheless, it is possible to have a “bulge” component. It is anyhow unlikely that it extends up to 10 degrees in latitude.
Pulsars interpretation of the GeV excess
Francesca Calore - University of Amsterdam NOW 201416
✓t
✓t
?
e.g Cholis, Hooper, Linden [arXiv:1407.5625]
Francesca Calore - University of Amsterdam NOW 201417
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 NOW 201417
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 NOW 201418
Backup slides
Unresolved Point Sources Diffuse ProcessesBlazars
Most abundant population of LAT detected sources Contribution up to 10 - 20 % !
Non-blazars active galaxies Few resolved members, but large unresolved population. !
!Star-forming galaxies
Outnumber AGN in number density, although 4 detected objects; ca 4 - 20% !!
Galactic Pulsars Second most abundant population, but few % of the diffuse flux.
DM annihilation In the Milky Way and in other galaxies.Uncertainty in the DM distribution. !Abdo et al., ApJ’10, Ajello et al., ApJ’12, Di Mauro et al, ’13
Inoue, ApJ’11, Di Mauro et al, ApJ’13
I. Tamborra presentation !
The origin of the IGRB
Francesca Calore - University of Amsterdam NOW 20143
!Potential to be one
of the most efficient future means of probing thermally
produced DM. Bringmann, Calore, Di Mauro, Donato, PRD’13
Francesca Calore - University of Amsterdam NOW 201418
Gamma-ray anistropyAnisotropy of the IGRB recently measured by the Fermi-LAT Collab. in the multipole range :
• 22 month of data • Energy range: • Region: (high latitudes) !➡ Anisotropy detected at small scales, ( ) ➡ Consistent with Poisson-like anisotropy from an
unresolved population of point-like sources. ➡ No-energy dependence
1� 50GeV|b| > 30�
` � 155 ✓ 2�
Ackermann et al.,PRD’12
` = 155� 504
Cp
hIi2 = 9.05± 0.84⇥ 10�6sr �s = 2.40± 0.07
Francesca Calore - University of Amsterdam NOW 201418
Gamma-ray anistropy from MSPs
The 1σ upper limit angular power from the unresolved MSPs together with Fermi-LAT data.
Calore, Di Mauro, Donato (2014)
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
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);
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
1. Galactic diffuse emission
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
1. Galactic diffuse emissionA. CRs (p) vs ISM: emission.⇡0
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
1. Galactic diffuse emissionA. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung.A. CRs (p) vs ISM: emission.⇡0
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
A. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung. C. CRs (e) vs ISRF: ICS emission.
1. Galactic diffuse emissionA. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung.A. CRs (p) vs ISM: emission.⇡0
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
A. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung. C. CRs (e) vs ISRF: ICS emission.
1. Galactic diffuse emissionA. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung.A. CRs (p) vs ISM: emission.⇡0
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.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201413
A. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung. C. CRs (e) vs ISRF: ICS emission.
1. Galactic diffuse emissionA. CRs (p) vs ISM: emission. B. CRs (e) vs ISM: Bremsstrahlung.A. CRs (p) vs ISM: emission.⇡0
2. Isotropic diffuse emission; 3. Fermi Bubbles brightness-uniform
emission; 4. Spherically symmetric template
for the GC emission.
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201414
Energy spectra of different components from the template
fit to the data.
2� |b| 20� & |l| 20�
Longitude dependence of the different components in a
latitude strip.
Calore, Cholis, Weniger (2014)
Low-latitude emission: the Fermi-LAT GeV excess
Francesca Calore - University of Amsterdam NOW 201415
Spectrum of the GCE emission with statistical and background model systematics.
Calore, Cholis, Weniger (2014)