Arrival directions of the highest-energy cosmic rays detected by the - - PowerPoint PPT Presentation

Arrival directions of the highest-energy cosmic rays detected by the Pierre Auger Observatory

Ugo Giaccari Ugo Giaccari1 for for the the Pierr Pierre e Auger Auger Collaboration Collaboration2

2

1Instituto de Física

Instituto de Física – Universidade Federal Rio de Janeir Universidade Federal Rio de Janeiro

• – Brazil

Brazil now

• w at

at Centr Centro Brasileir

• Brasileiro Pesquisa Física Rio de Janeir
• Pesquisa Física Rio de Janeiro
• – Brazil

Brazil

• 2Av. San Martín Norte 304, 5613

. San Martín Norte 304, 5613 Malar Malargüe güe, Ar , Argentina gentina

Outline

2 Pr Previous r evious results on small/intermediate scales anisotr esults on small/intermediate scales anisotropies of the most ener

• pies of the most energetic CRs

getic CRs in ten years of operation, 1/2004 – 3/2014 [ in ten years of operation, 1/2004 – 3/2014 [ApJ ApJ 804, 15, (2015)] 804, 15, (2015)] Around Centaurus A

ener energy thr gy threshold E eshold Eth

th = 58

= 58 EeV EeV for an angular window for an angular window ψ = 15° = 15°

Bright AGNs of the Swift-BAT catalog

Eth

th = 58

= 58 EeV EeV, , ψ = 18°, for objects within 130 = 18°, for objects within 130 Mpc Mpc and brighter than 10 and brighter than 1044

44 er

erg/s g/s

two lar two largest departur gest departures fr es from isotr

• m isotropy
• py

both with post-trial pr both with post-trial probability ~1.4

• bability ~1.4 × 10

10-2

• 2

ü Report an update of these two excesses with enlarged dataset ü Search for deviations from isotropy using two extra-galactic populations of gamma-ray sources

• Star-forming galaxies and AGNs motivated by gamma-ray observations of Fermi-LAT
• Weight individual sources in proportion to their fluxes
• Same flux-weight analysis for the objects of the Swift-BAT catalog

] ° [

• 80
• 60
• 40
• 20

20 40 60 80

yr]

2

) [km

• (
• 5000

10000 15000 20000 full data set vertical inclined

3

The Dataset

Events detected by the Surface Detector of the Pierr Events detected by the Surface Detector of the Pierre Auger Observatory (*) e Auger Observatory (*) fr from 1

• m 1st

st Jan. 2004 to 30

• Jan. 2004 to 30th

th April 2017 above 40

April 2017 above 40 EeV EeV, with ~90,000 km , with ~90,000 km2

2 sr

sr yr yr ü zenith angle zenith angle θ ≤ 60°, 60°, 650 (“vertical”) events 650 (“vertical”) events ü zenith angle 60° zenith angle 60° ≤ θ ≤ 80°, 80°, 170 (“inclined”) events 170 (“inclined”) events Same qual Same quality cuts used in ity cuts used in ApJ ApJ 804 (2015),1 804 (2015),1 820 events E > 40 820 events E > 40 EeV EeV ~30% incr ~30% increase in the ease in the statistic r statistic respect to espect to pr previous r evious results esults

Vertical/Inclined exposur ertical/Inclined exposure: 71,070/18,650 km e: 71,070/18,650 km2

2 yr

yr sr sr

(*) (*) see see F F . . Fenu’ nu’s talk talk For each energy threshold in this analysis energy migration effects taken into account

Geometrical exposure Correct vertical and inclined exposures for unfolding factors as in spectrum studies (*)

E > 40 E > 40 EeV EeV: ~ 5/6% for vert./incl. : ~ 5/6% for vert./incl. E > 80 E > 80 EeV EeV: ~ 8% for : ~ 8% for vert vert, ~20% for incl. , ~20% for incl.

The Centaurus A region

4

ü Compar Compare e the the cumulative cumulative number number of

• f observed
• bserved (

(nobs

• bs)

) events events with with the the expected expected on

• n average

average fr from

• m isotr

isotropic

• pic simulations

simulations ( (nexp

exp)

) ü Compute Compute the the cumulative cumulative binomial binomial pr probability

• bability (

(P) ) to measur to measure e nobs

• bs

given

given < <nexp

exp>

> ü Scan can in in parameters parameters: :

(degree)

• 5

10 15 20 25 30 (EeV) th E 40 45 50 55 60 65 70 75 80

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1

Largest excess

Eth = 58 EeV, Ψ = 15° nobs = 19, nexp = 6.0 P ~ 1.1 × 10-5 (fraction fraction of

• f isotr

isotropic

• pic simulations

simulations that that have a ave a smaller smaller pr probability

• bability under

under the the same same scan scan) )

Post-trial probability ~ 1.1 × 10-3

Eth

th in [40; 80]

in [40; 80] EeV EeV in in steps steps of

• f 1

1 EeV EeV Ψ in [1°; 30°] in in [1°; 30°] in steps steps of

• f 0.25°

0.25° up up to to 5°, 1° for 5°, 1° for lar larger ger angles angles

preliminary Region of secondary minima above ~40 EeV

(degree)

• 5

10 15 20 25 30 (EeV) th E 40 45 50 55 60 65 70 75 80

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10 1

Cross-Correlation with bright AGNs (Swift-BAT)

5

ü Count Count the the cumulative cumulative number number of

• f pairs

pairs btw btw CRs CRs and and objects

• bjects dir

directions ections ( (nobs

• bs)

) ü Excess xcess pr probability

• bability pr

provides

• vides by

by the the fraction fraction of

• f isotr

isotropic

• pic simulations

simulations ( (fmin

min)

) with with equal equal or

• r

gr greater eater number number of

• f pairs

pairs ü Scan can in in parameters parameters: :

Largest excess

Eth = 62 EeV, Ψ = 16° nobs = 57, nexp = 26.4 fmin = 1 × 10-7 after fter accounting accounting for for the the scan scan in (E, in (E, ϑ, , Dmax Dmax, , Lmin Lmin)

Post-trial probability ~ 6.5 × 10-4

Eth

th in [40; 80]

in [40; 80] EeV EeV in in steps steps of

• f 1

1 EeV EeV Ψ in [1°; 30°] in in [1°; 30°] in steps steps of

• f 0.25°

0.25° up up to to 5°, 1° for 5°, 1° for lar larger ger angles angles

preliminary

(E/ψ) scan for Dmax = 130 Mpc, Lmin

= 1044 erg/s

6

Gamma-ray Sources

Active Galactic Nuclei

• Selected fr

Selected from 2FHL Catalog (

• m 2FHL Catalog (Fermi

Fermi-LA

• LAT, 360 sour

, 360 sources): ces): Φ(> 50 (> 50 GeV GeV) ---> pr ) ---> proxy for UHECR flux

• xy for UHECR flux
• Selection of the 17 objects within 250
• Selection of the 17 objects within 250 Mpc

Mpc

• Majority
• Majority blazars

blazars of BL-Lac type and radio-galaxies of FR-I type

• f BL-Lac type and radio-galaxies of FR-I type

Star-forming or Starburst Galaxies

Use of Use of Fermi- Fermi-LA LAT sear search list for star ch list for star-formation objects (Ackermann+ 2012) formation objects (Ackermann+ 2012)

• 63 objects within 250

63 objects within 250 Mpc Mpc, only 4 detected in gamma rays: , only 4 detected in gamma rays: corr correlated elated Φ(> 1.4 GHz) ---> pr (> 1.4 GHz) ---> proxy for UHECR flux

• xy for UHECR flux
• Selection of brightest objects (flux completeness) with
• Selection of brightest objects (flux completeness) with Φ(> 1.4 GHz) > 0.3

(> 1.4 GHz) > 0.3 Jy Jy

• 23 objects, size similar to the gamma-ray AGN sample

23 objects, size similar to the gamma-ray AGN sample Assumption UHECRs flux proportional to non thermal photon flux

Maximum likelihood technique

7

Build probability maps of CRs arrival directions

• Weight objects by their r

eight objects by their relative flux in the corr elative flux in the corresponding esponding electr electromagnetic wavelength

• magnetic wavelength
• Fisher

Fisher-V

• Von
• n Mises

Mises (~2D Gaussian) smearing (~2D Gaussian) smearing center centered on astr ed on astrophysical objects

• physical objects
• Isotr

Isotropic fraction (dif

• pic fraction (diffuse flux)

fuse flux)

• Account for dir

Account for directional exposur ectional exposure e and normalize to the total number of events and normalize to the total number of events

Smearing Angle Ψ first free parameter Anisotropic Fraction fani = 1 - fiso second free parameter

Test statistic (TS) likelihood ratio TS = 2 log [ L( TS = 2 log [ L(Ψ,f ,fani

ani) / L(

) / L(fani

ani = 0) ]

= 0) ]

Wilk’ Wilk’s Theor Theorem em: : TS TS distributed distributed accor ccording ding a a Χ2

2 with

with two two degr degrees ees of

• f fr

freedon eedon

(good good agr agreement eement with with isotr isotropic

• pic simulations

simulations) )

Scan in energy threshold [20; 80] EeV in steps of 1 EeV Maximum deviation from Isotropy found at ~40 EeV for one model lowering minimum energy to 20EeV 5514 events, same quality cuts of 5514 events, same quality cuts of ApJ ApJ 2015 2015 4396 (“vertical”) events 4396 (“vertical”) events 1118 (“inclined”) events 1118 (“inclined”) events

Test Statistic vs. Energy

8 Mass Mass composition composition model model following following JCAP 04 (2017) 38 for JCAP 04 (2017) 38 for accounting accounting CRs CRs pr propagation

• pagation

Homogeneous distribution of sour Homogeneous distribution of sources ces EPOS-LHC, EPOS-LHC, γ = 1 = 1 log

• g10

10(Rcut cut/V) = 18.68

/V) = 18.68 fH(%) = 0, (%) = 0, fHe

He(%) = 67.3 ,

(%) = 67.3 , fN(%) = 28.1 (%) = 28.1 fSi

Si(%) = 4.6,

(%) = 4.6, fFe

Fe(%) = 0

(%) = 0 attenuation: negligible impact on nearby objects (starburst) more impact on distant objects (AGNs)

Starburst Galaxies TS = 24.9, E TS = 24.9, Eth

th = 39

= 39 EeV EeV γ-ray detected AGNs TS = 15.2, E TS = 15.2, Eth

th = 60

= 60 EeV EeV Swift-BAT AGNs TS = 19.9, E TS = 19.9, Eth

th = 60

= 60 EeV EeV

Other scenarios also tested

9

Best-fit parameters

Starburst Galaxies fani

ani = 10%,

= 10%, Ψ

= 13°

= 13° TS = 24.9 TS = 24.9 p-value 3.8 p-value 3.8 × 10 10-6

• 6

Post-trial probability 4 4 × 10 10-5

• 5 ( ~ 3.9

( ~ 3.9 σ)

1-2σ contours

(fraction of isotropic simulations that have a greater TS under the same energy scan)

γ-ray detected AGNs fani

ani = 7%,

= 7%, Ψ

= 7°

= 7° TS = 15.2 TS = 15.2 p-value 5.1 p-value 5.1 × 10 10-4

• 4

Post-trial probability 3 3 × 10 10-3

• 3 ( ~ 2.7

( ~ 2.7 σ)

preliminary

10

Maps for the best-fit parameters

CenA ~ 4 Mpc NGC 4945 M 83 3.7Mpc NGC 253 NGC 253 2.5 2.5 Mpc Mpc NGC 1068 NGC 1068 16.7 16.7 Mpc Mpc

E > 39 EeV Ψ = 10°

preliminary

E > 60 EeV Ψ = 7°

Galactic coordinate

ü We have measur e have measured a ~3.9 ed a ~3.9σ (*) (*) deviation fr deviation from isotr

• m isotropy at an intermediate
• py at an intermediate

angular scale. angular scale. ü It can be attributed to char It can be attributed to charged cosmic rays coming pr ged cosmic rays coming prefer eferentially fr entially from the

• m the

dir directions of starburst galaxies in our vicinity of the Universe. ections of starburst galaxies in our vicinity of the Universe. ü We We cannot cannot exclude exclude contributions contributions fr from

• m sour

sources ces having having same same flux flux and and angular angular distributions distributions as as the the starburst starburst galaxies galaxies

Conclusion

Update of the pr Update of the previously unlikely findings eviously unlikely findings Centaurus Centaurus A, brightest S A, brightest Swift ift AGNs AGNs

ü Significance of the association incr Significance of the association increased in both cases at ~3. eased in both cases at ~3.σ(*) level (*) level with with thr three additional years of data ee additional years of data

examine CRs arrival dir examine CRs arrival direction in r ection in relation to elation to gamma-ray sour gamma-ray sources ces

(*) not a priori explorations, the significance do not account for the previous searches made within the Auger Collaboration and those made by others

12

Extra-slides

13

The Data Sets

Events detected by the Surface Detector of the Pierre Auger Observatory from 1st Jan. 2004 to 30th April 2017 above 40 EeV ü zenith angle θ ≤ 60° (“vertical”) events

• largest signal detector surrounded

at least by 4 detectors

• core inside triangle of contiguous

detectors (isosceles and/or equilateral)

full efficiency > 3 EeV ü zenith angle 60° ≤ θ ≤ 80° (“inclined”) events

• at least 5 detectors surround the
• ne closest the shower core

full efficiency > 4 EeV Above 10 EeV

ü Angular resolution better than 0.9° ü Statistical uncertainty on energy estimation better than 12% ü Systematic in absolute energy scale ~ 14%

Centaurus A – ApJ 2015

E ≥ 58 EeV, r = 15° fmin = 2 × 10-4 nobs = 14 nexp = 4.5 post-trial probability ~1.4% 14

E ≥ 58 EeV, r = 18° nobs = 62 nexp = 32.8 pre-trial probability = 2 × 10-6 post--trial probability = 1.3 × 10-2

15

Bright Swift-BAT AGNs – ApJ 2015

• Complete for Φ > 1.34 10-11 erg/s/cm2 in the band (14-195 keV)
• ~ 300 AGNs above the cut in flux within 200 Mpc
• Majority of Seyfert I&II spiral galaxies

Eth

th in [40; 80]

in [40; 80] EeV EeV in in steps steps of

• f 1

1 EeV EeV Ψ in [1°; 30°] in in [1°; 30°] in steps steps of

• f 0.25°/1°

0.25°/1° Lmin

min in [10

in [1042

42; 10

; 1044

44] er

] erg/ g/s, in , in steps steps of

• f log(L) = 0.33

log(L) = 0.33 Dmax

max in [10; 190]

in [10; 190] Mpc Mpc, in , in steps steps of

• f 20

20 Mpc Mpc

Bright Swift-BAT AGNs – ApJ 2015

16

Zenith distribution

zenith [degree]

20 40 60 80

number of events

100 200 300 400

Dotted

• tted line

line: : expected expected sin sin θ cos cos θ distribution distribution fr from

• m isotr

isotropy

• py

zenith [degree]

20 40 60 80

number of events

20 40 60

E > 20 EeV E > 40 EeV 17

18

JC JCAP 04 04 (2017) 2017) 38 38