department of physics, university of udine, italydeangeli/fismod/vhegamma.pdf · 2012. 12. 4. · 3...

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Cluster of very bright stars, Omega Centauri,

as observed from the space:

60,000 K

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μ

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5

~ parsecs

Accretion Disk 3- 10 rs Black Hole Diameter = 2rs ~ 4 AU

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E2 d

N/d

E

energy E

e- (TeV) Synchrotron (eV-keV)

(TeV) Inverse Compton (eV)

B

e.m. processes

0decay

-

0

+

(TeV)

p+ (>>TeV)

matter

hadronic cascades

VHE

In the VHE region, dN/dE ~ E- ( : spectral index)

To distinguish between had/leptonic origin study Spectral Energy Distribution (SED): (differential flux) . E2

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Radio 408 Mhz

Infrared 1-3 μm

Visible Light

Gamma Rays

Centre of Galaxy in Different Photon Wavelengths

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New instruments often give unexpected results:

With future new detector can again hope for completely new discoveries

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De Angelis, Galanti, Roncadelli 2011

with Franceschini EBL modeling

30 G

eV

100 G

eV

red

shif

t z

ray energy (TeV)

= 1 (GRH)

> 1

region of opacity

VHE bck e+e-

( ) ~

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• The earth atmosphere (28 X0 at

sea level) is opaque to X/ Thus

only a satellite-based detector

can detect primary X/

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Atmospheric

Sat

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17 Unfolding is a nice mathematical problem !

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e+ e-

10

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Incoming

-ray

~ 10 km

~ 1o

Che

renk

ov li

ght

~ 120 m

Image intensity

Shower energy

Image orientation

Shower direction

Image shape

Primary particle

The Cherenkov technique

c ~ 1º

e Threshold @

sl: 21 MeV

Maximum of a 1 TeV

shower

~ 8 Km asl

~ 200 photons/m2 in

the visible

Angular spread ~ 0.5º

20 20

Crab

10% Crab

1% Crab

Fermi

Magic-II

E*F

(>E

) [

TeV

/cm

2s]

Agile

, F

erm

i, A

rgo,

Haw

k:

1 y

ear

Magic

, H

ess,

Verita

s,

CTA

: 50h

Agile

Argo

Hess/Veritas

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24 Marvel 1961

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= ln

=

/( )+( )

(> )

=/( )

+( )

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R 10 km, B 10 T E 10 TeV

Large Hadron Collider

Tycho SuperNova Remnant

E BR

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μ

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30 And also: the maximum possible energy for a terrestrial accelerator is ~ 5

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μ

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extremely difficult

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dN

dE

dNp

dE p

D x =E

E p

Alessandro De Angelis

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Fermi,

Egret

Magic,

Veritas

34 Alessandro De Angelis

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[Albert et al. ApJ 664L 87A 2007

W51: gamma rays come from a

molecular cloud separated from the

pulsar

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Alessandro De Angelis 36

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VHE

nucleus

Peak flux

nucleus

X-ray

Radio

HST-1

Core

Knot D Knot A

Colours: 0.2 - 6 keV (Chandra) Contours: 8 GHz radio (VLA)

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Chandra

jet37


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dN

dE

1

2

dN

dE

Very accurate input for

neutrino detectors


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x

x x

Measurement of spectral features permits to constrain EBL models

VHE bck e+e-

Heitler 1960

( ) ~

Mean free path

e+

e-


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Selection bias? New physics ?

~ E-2


De Angelis, Galanti, Roncadelli 2011

with Franceschini EBL modeling

red

shif

t z

ray energy (TeV)

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• 10 1

*

a

*

*

…

*

a a

La = ga

E

B ( )a

P a NP1

P1

ga2 BT

2s2

42 10 3 BT s ga

2

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DARMA

3C279

Note: if conversion “a la

Simet-Hooper-Serpico”,

=> the effect could be directional

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EP = hcG 1.2 1019

H 2= m2

+ p2 H 2= m2

+ p2 1+E

EP

+…

Hp>> p 1+

m2

2p2 +p

2EP

+…

v =H

p1

m2

2p2 +p

EP

v 1+E

EP

t T EEP

28

55

c 2 p2= E 2 1

E

Es

+ OE

Es

2

= -1

= 1

v =H

p1

m2

2p2 +p

EP

1. If <0 => ce < c => decay -> e+e- kinematically allowed for gamma with

energies above

2. If >0 => ce > c => electrons become superluminal for energies larger than

Emax/sqrt(2) => Vacuum Cherenkov Radiation.

- E > 100 TeV => abs( ) < 5 x 10-17

Emax = me sqrt(2/abs( ))

- Ee > 2 TeV from cosmic electron radiation => abs( ) < 2 x 10-14

- Modification of -> e+e- threshold. Using Mkn 501 and Mkn 421

spectra observations up to Eg > 20 TeV

=> abs( ) < 1.3 x 10-15

From MAGIC Mkn501 (taken as a LIV signal): | | ~ 2 10-15

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v 1+E

EP

t T EEP


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HESS PKS 2155 z = 0.116

July 2006 Peak flux ~15 x Crab ~50 x average Doubling times 1-3 min

RBH/c ~ 1...2.104 s

H.E.S.S. arXiV:0706.0797

MAGIC, Mkn 501 Doubling time ~ 2 min

astro-ph/0702008 arXiv:0708.2889


Alessandro De Angelis 60 HESS, PKS 2155

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0.15-0.25 TeV

0.25-0.6 TeV

0.6-1.2 TeV

1.2-10 TeV 4 min lag

1st order

> 1 GeV

< 5 MeV

( t)obs

E

Es1

H0

1 dz'(1+ z')

M (1+ z')3+

0

z

MAGIC Mkn 501, PLB08 (with J. Ellis et al.) Es1 ~ 0.04 MP ( ~ -25) Es1 > 0.02 MP

HESS PKS 2155, PRL08

Es1 > 0.06 MP

GRB X-ray limits: Es1 > 0.11 MP (Fermi, but…)

v c 1+E

MP

+ 22 E

MP2 + ...

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K(z)~z

~ -12

( t)obs

E

Es1

H0

1 dz'(1+ z')

M (1+ z')3+

0

z

t

E MP

H0

1K(z)

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• z = 1.8 ± 0.4

• one of the brightest GRBs

observed by LAT

• after prompt phase, power-low

emission persists in the LAT data as

late as 1 ks post trigger:

highest E photon so far detected:

33.4 GeV, 82 s after GBM trigger

[expected from Ellis & al. (26 ± 13) s]

• much weaker constraints on LIV Es

• z = 0.903 ± 0.003

• prompt spectrum detected,

significant deviation from Band

function at high E

• High energy photon detected:

31 GeV at To + 0.83 s

[expected from Ellis & al. (12 ± 5) s]

• tight constraint on Lorentz

Invariance Violation:

– Es1 = MQG > several MPlanck

=> Fermi rules, and 1st order violations appear unlikely

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Es2 > 6 1010 GeV (~10-9 MP) (HESS, MAGIC)

( t)obs

3

2

E

Es2

2

H01 dz'

(1+ z')2

M (1+ z')3+

0

z

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GRH depends on the –ray path and there the Hubble constant and

the cosmological densities enter => if EBL density and intrinsic

spectra are known, the GRH might be used as a distance estimator

GRH behaves differently than other observables already used for cosmology measurements.

Blanch & Martinez 2004

Simulated measurements

Mkn 421 Mkn 501

1ES1959+650 Mkn 180

1ES 2344+514

PKS2005-489

1ES1218+304

1ES1101-232

H2356-309 PKS 2155-304 H1426+428

EBL constraints are paving

the way for the use of AGN

to fit M and …

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Using the foreseen precision on the

GRH (distance at which (E,z)=1)

measurements of 20 extrapolated

AGN at z>0.2, cosmological

parameters can be fitted.

=> The 2=2.3 2-parameter

contour might improve by a

factor 2 the 2004’ Supernovae

combined result !

E,z( ) = d z dl

d z 0

z

dxx

20

2

d n , z ( ) 2xE 1+ z( )2[ ]

2m 2c 2

Ex 1+z( )2

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Begelman/

Navarro

=( )

( ) ~

r

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los

2dl

from particle physics

from

ast

rophysi

cs

Look to the closest point with M <<L

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All-sky map of simulated gamma ray

signal from DM annihilation

(Pieri et al 2006)

Satellites

Low background and good source id,

but low statistics, astrophysical background

Galactic Center

Good statistics but source

confusion/diffuse background

Milky Way Halo

Large statistics but diffuse background

Spectral Features

Lines, endpoint Bremsstrahlung,…

No astrophysical uncertainties, good source Id, but low sensitivity because of expected small BR

Extra-galactic

Large statistics, but astrophysics, galactic

diffuse backgrounds

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Chandra GC survey

NASA/UMass/D.Wang et al.

CANGAROO (80%)

Whipple (95%)

H.E.S.S.

from W.Hofmann, Heidelberg 2004

detection of -rays from GC by Cangaroo,

Whipple, HESS, MAGIC

hard E-2.2 spectrum

fit to -annihilation continuum

spectrum leads to: M > 14 TeV

other interpretations possible (probable)

Galactic Center: very crowded sky region, strong exp.

evidence against cuspy profile

no real indication of DM…

The spectrum is featurless!!!

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FORNAX

BOOTES

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MAGIC ICRC 2011

Preliminary

all e+e-


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probe e+/e- ratio at 300-700 GeV

?

MAGIC

e+/e

++

e-


• LHC may find candidates but cannot prove that

they are the observed Dark Matter, nor localize it

• Direct searches (nuclear recoil) may recognize

local halo WIMPs but cannot prove the nature and

composition of Dark Matter in the sky

• LHC reach limited to some 200-600 GeV; IACT

sensitivity starts at some ~200 GeV (should

improve)


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• extend E range beyond 50 TeV

• better angular resolution

• larger FOV

• monitor many objects simult.

• extend E range under 50 GeV

•10x sources

• better flux sensitivity

• lower threshold


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low energy section

Ethresh ~ 10 GeV

4 23 m telescopes

core array

100 GeV-10 TeV

~ 23 12 m telescopes

high energy section

~35 tel.

on 10 km2 area

2 arrays: north+south

all-sky coverage


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Very deep field

Deep field

~1/3 of telescopes

Monitoring

4 telescopes

Survey mode:

Full sky at current

sensitivity in ~1 year


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Crab

10% Crab

1% Crab

Fermi

Magic-II

E*F

(>E

) [

TeV

/cm

2s]

Agile

, F

erm

i, A

rgo,

Haw

k:

1 y

ear

Magic

, H

ess,

Verita

s,

CTA

: 50h

Agile

C T A

Argo

Hawc

Hess/Veritas

Far universe

Pulsars Fundamental physics

Cosmic rays

at the knee

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Results from HESS, MAGIC and VERITAS

Over 350 publications in high-impact journals:

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Chandra Hubble


The future in

VHE gamma ray

astronomy:

World-wide Collaboration

25 countries

132 institutes

>800 scientists

10 fold sensitivity of current instruments

10 fold energy range

improved angular resolution

two sites (North / South)

operated as observatory

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Design study phase concluded in Fall 2010

Design Concepts for the Cherenkov Telescope Array

(arXiv:1008.3703)

FP7-supported Preparatory Phase: Fall 2010 – Fall 2013

Technical design, sites, construction and operation cost

Legal, governance and finance schemes

Small + medium-sized telescope prototypes

Aim for

start of deployment in early 2014

first data in 2016/17

base arrays complete in late 2018

expanded mid-energy array driven by US

total cost below 200 M

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Carbon-fibre

structure

400 m2 dish area

1.5 m sandwich

mirror facets

On (GRB) target

in < 20 sec.

27.8 m focal length

4.5o field of view

0.1o pixels

16 m focal length

7-8o field of view

0.18o pixels

100 m2 dish area

1.2 m mirror

facets

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Under study:

dual-mirror optics with compact photo sensor arrays

single-mirror optics

PMT-based and silicon-based sensors

Not yet conclusive which solution is most cost-effective

One of four

options for

telescope

structure

Multi-Anode PMT camera option

Wavelenght range

300 – 600 nm

Mirror PSF

O(1’) on axis, worse off axis

Pixel size

0.1o – 0.2o

Source localization

5” – 10” for source centroid

Image rate

kHz

Exposure time

single image: O(10 ns)

typical source: 10 – 50 h

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+30

-30

Warning: map not quite accurate

proposals for sites due 6/2011 (S) and 12/2011 (N)

evaluation and downselection to few sites

final selection

Hardware key elements:

- O(100) Telescope structures/drives: very resistant, reliable,

accurate, light-weight (LST)

- O(10.000) m2 Mirrors: good quality, stable in extreme

conditions, cheap, light-weight

- O(2-3 x10.000) camera channels:

* Photosensors: PMT (and eventually SiPMs)

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* Readout Electronics: fast, low dissipation, compact,

reliable, cheap

- Timing/Synchronization: comparable to LHC machine

requirements

- Trigger/Data: comparable to LHC experiments

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Fermi

HESS

CTA

MILAGRO HAWC

factor 3

improvement


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HESS map of the Gal.plane, total exp ~500 hours


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2008 2009 2010 2011 2012 2013 2014 2015


department of physics, university of udine, italydeangeli/fismod/vhegamma.pdf · 2012. 12. 4. · 3...

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