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TeV Gamma Ray Sky

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Title: TeV Gamma Ray Sky


1
TeV Gamma Ray Sky
  • F.A. Aharonian (MPI-K, Heidelberg)

VLVnT2, Catania, Nov 11, 2005
2
TeV Gamma-Ray Astronomy
  • a new observational discipline/a branch of High
    Energy Astrophysics
  • provides crucial window in the spectrum of
    cosmic E-M radiation
  • 0.1 TeV and 100
    TeV
  • for exploration of nonthermal phenomena in
    the Universe
  • in their most energetic, extreme and
    violent forms
  • TeV gamma-rays unique carriers of
    astrohysical information
  • are effectively produced in E-M and hadronic
    interactions
  • penetrate freely throughout intergalactic and
    galactic B-fields
  • are effectively detected by ground-based
    detectors (IACTs)

3
Intensity Shower Energy
Image Shape Background rejection
4
stereoscopic approach
image of source is somewhere on the image axis
need several views to get unambiguous shower
direction
5
H.E.S.S. - High Energy Stereoscopic System
13m diameter dish
920 pixel, 5 deg FoV camera
6
Potential of IACT Arrays
  • sensitivity 10-13 (10-14) erg/cm2s
    dynamical range 100 (3) GeV to 30 (300) TeV
  • angular resolution 3 (1-2) arcmin
    energy resolution 10 to 20
  • detection area 108 to 1010 (1011) cm2
    photon statistics typically gtgt100
  • FE erg/cm2 s an indicator how
  • deep the energetics in the relevant
  • energy band can be probed
  • Lg4pd2 FE
  • Lg,min 1033 (d/10kpc)2
  • Lg,min 1041 (d/100Mpc)2
  • two orders of magnitude
  • deeper probes than EGRET
  • gt 10 arcmin extended sources
  • more sensitive than Chandra
  • a basis for optimistic expec-
  • tations (many sources)?
  • YES and NO ...
  • IACTs - very effective
  • multi-functional tools
  • spectrometry
  • temporal studies
  • morphology
  • surveys
  • extended sources
  • from SNRs to
  • Clusters of Galaxies
  • transient phenomena
  • mQSOs, AGN, GRBs, ...
  • Galactic Astronomy,
  • Extragalactic Astronomy
  • Observational Cosmology

Energy Flux, E2J(E), erg/cm2 s

7
The VHE Sky today
11 Galactic, 11 Extragalactic, GC, plus 15
unidentified not many sources ... but at least 7
source populations !
H1426
1ES 1218
Mrk421
M87
Mrk501
PSR B1259
1ES 1101
1ES1959
SNR G0.9
RXJ 1713
RXJ 0852
Crab
Cas A
LS 5039
TeV 2032
Vela X
GC
1ES 2344
HESS J1303
Cygnus Diffuse
MSH 15-52
PKS 2155
H2356
PKS 2005
gal. compact
Galactic Center
8
H.E.S.S. survey of the central region of
the Galactic Plane 15 more (yet
unidentified) sources
S. Funk
9
TeV g-ray Source Populations

  • Extended Galactic Objects
  • Shell Type SNRs
  • Giant Molecular Clouds (star formation
    regions)
  • Pulsar Wind Nebulae plerions

  • Compact Galactic Sources
  • Binary pulsar PRB 1259-63
  • LS5039 a Microquasar

  • Galactic Center

  • Extragalactic objects
  • M87 - a radiogalaxy
  • TeV Blazars with redshift from 0.03 to
    0.18
  • and a large number of yet unidentified TeV
    sources

10
Major Objectives of TeV g-ray Astronomy
  • Origin of Galactic Cosmic Rays
  • SNRs, Molecular clouds, Diffuse radiation
    of the Galactic Disk, ...
  • Galactic and Extragalactic Sources with
    relativistic flows
  • Pulsar Winds, mQSOs, Small and Large Scale
    jets of AGN, GRBs...
  • Observational Gamma Ray Cosmology
  • Large Scale Structures (Clusters of
    Galaxies), Dark Matter Halos,
  • Diffuse Extragalactic Background radiation,
    Pair Halos
  • ........
  • ....

11
SNRs and Origin of Cosmic Rays
  • a mystery since the discovery in 1912 by V.
    Hess
  • but now we are close (hopefully) to the
    solution of the
  • (galactic) component below the energy 1015
    eV thanks to
  • HESS capability for deep spectrometric and
    morphological
  • studies of g-rays from SNRs in the
    crucial energy band
  • 100 GeV to gt 30
    TeV
  • GLAST will provide additional (complementary)
  • information in the energy domain
    100 MeV-100 GeV
  • km3 scale TeV neutrino detectors will provide
    unambiguous
  • information about the hadronic
    component of radiation

12
SNRs the most probable factories of GCRs ?
  • (almost) common belief based on two arguments
  • necessary amount of available energy 1051 erg
  • Diffusive Shock Acceleration (DSA) 10
    efficiency and E-2 type

  • spectrum up to ?
    at least 1015 eV
  • Straightforward proof detection of g-rays (and
    neutrinos) from pp
  • interactions (as
    products of decays of secondary pions)
  • Objective to probe the content of
    nucleonic component of CRs
  • in SNRs within 10
    kpc at the level 1049 -1050 erg
  • Realization sensitivity of detectors -
    down to 10-13 erg/cm2 s
  • crucial energy
    domain - 100 GeV - 100 TeV

13
Cosmic Ray Accelerators ?
SNRs in our Galaxy 231(Green et al. 2001
with nonthermal X-ray emission - 10 or so
best candidates - young SNRs with nonthermal
synchrotron X-rays
SN1006
Diffusive source
Tycho
Kepler
CasA
30 arcmin
TeV emission
H.E.S.S. PSF
14
energy spectrum and
morphology
RXJ1713.7-3946 is a TeV source !
G2.1-2.1 with a curvature cutoff (?) at high
energies
no significant spectral variation
G2.1-2.2 -evidence of DSA of protons ?
HESS 2004 data preliminary !
15
RX 1713.7-3946
interpretation
the key issue - identification of g-ray
emission mechanisms p0 or IC ? new! -
energy spectra 150GeV-30 TeV
from different parts - NW, S W, E,C if
a coordinate-independent single power law
from 100 GeV to 10 TeV
difficult to explain by IC implications
? if p0 - hadronic component is detected !
estimate of Wp (with an uncertainty
related to the uncertainty in n/d2 )
if IC - model independent estimate of We
(multi-TeV electrons) LeLx and
model independent map of B-field
TeV-keV correlations what this could mean?
16
Origin of radiation ?
  • hadronic origin preferable given
  • the high density environment
  • Wp (above 10 TeV) 3x1049 (n/1 cm-3) -1
    erg
  • IC origin is not (yet) excluded, but this model
  • requires B field less than
    10 mG
  • more complex scenarios ? e.g. g-rays from NWSW
    are contributed by
  • protons while gamma-rays from remaining parts are
    due to IC g-rays
  • HESS observations with 4 telescope in
    2004 and 2005
  • provide higher quality data and
    certain answers ?

17
New ! Vela Junior (a 2o diameter remnant)
B-fields RXJ 10 mG Vela Jr 4 mG
B-fields RXJ 10 mG Vela Jr 4 mG
CANGAROO , HESS Flux - 1 Crab at 1 TeV
no problem with hadronic gamma-ray models good
news for km3 scale neutrino detectors ! (?)
uncertainty in d as large as factor of 3, n
poorly known if no nearby clouds - Wp could be
as large as 1050 erg
IC origin ? very small B-field, B lt 10 mG,
and very large
Emax gt 100 TeV two assumptions hardly can
co-exists within standard DSA models
18
IC model B-field cannot exceed 10 mG and
does not provide
good spectral fit
19
steeper electron acceleration spectra ? now a
better fit, but conflict with radio and
2 orders of magnitude larger energetics
20
older source ?
21
two zone model ?
tesc50 tB (prop. 1/E) B13 mG, B215mG R3
pc
22
older source ?
23
RXJ 1713.7-3946 Spectrum of protons dN/dEK
E-a exp-(E/Ecut)b
Wp(gt1 TeV) w 0.5x1050 (n/1cm-3)(d/1kpc)2
24
spectra of gamma-rays and neutrinos
25
neutrino fluxes from RXJ1713.7-3946
Alvarez-Muniz and Halzen dN/dE4.14x10-11
(E/1TeV) -2 ph/cm2 s TeV 4.1 x 10-11 ph/cm2
s above 1 TeV 4.1 x 10-12 ph/cm2 s above 10
TeV
Costantini and Vissani dN/dEg1.7 x 10-11
(Eg/1TeV) -2.2 ph/cm2 s TeV
dN/dEn 1.5 x 10-11 (En/1TeV)
-2.2 ph/cm2 s TeV 1.2 x 10-11 ph/cm2 s above 1
TeV 0.8 x 10-12 ph/cm2 s above 10 TeV
our calculations 1. 0.87x10-11 ph/cm2 s
above 1 TeV 0.99 x 10-13 ph/cm2 s above 10
TeV 2. 0.90x10-11 ---
1.70x10-13 --- 3.
0.88x10-11 ---
1.78x10-13 ---
Before flavor oscillations
26
searching for galactic PeVatrons ...
TeV gammarays from Cas A and RX1713.7-3946,
Vela Jr a proof that SNRs are responsible for
the bulk of GCRs ? not yet
the hunt for galactic PeVatrons continues
unbiased approach deep survey of the Galactic
Plane not to miss any
recent (or currently active) acceleration site

SNRs, Pulsars/Plerions,
Microquasars...
not only from accelerators, but also from nearby
dense regions
27
Gamm-rays/X-rays from dense regions surrounding
accelerators
  • the existence of a powerful accelerator by itself
    is not sufficenrt for
  • gamma radiation an additional component a
    dense gas target - is required

gamma-rays from surrounding regions add much to
our knowledge about highest energy protons
which quickly escape the accelerator and
therefotr do not signifi- cantly contribute to
gamma-ray production inside the proton
accelerator-PeVatron
28
older source steeper g-ray spectrum
tesc4x105(E/1 TeV) -1 k-1 yr (R1pc) k1
Bohm Difussion
Qp / E-2.1 exp(-E/1PeV)
Lp1038(1t/1kyr) -1 erg/s
29
Giant Molecular Clouds (GMCs)
as tracers of Galactic Coismic Rays
  • GMCs - 103 to 105 solar masses clouds
    physically connected with
  • star formation regions - the likely sites of
    CR accelerators (with
  • or without SNRs) - perfect objects to play
    the role of targets !
  • While travelling from the accelerator to the
    cloud the spectrum of CRs
  • is a strong function of time t, distance to the
    source R, and the (energy-
  • dependent) Diffusion Coefficient D(E)
  • depending on t, R, D(E) one may expect
    any proton, and
  • therefore gamma-ray spectrum
    very hard, very soft,

  • without TeV tail, without GeV counterpart ...


30
R10pc to 1 - 100yr 2 1,000yr 3
- 10000yr
to1,000yr R 1 100pc 2 30pc 3
10pc
continuous accelerator of age to Lp1037 erg/s,
ap2, Emax100 TeV, diff.coef.
D(E)1027(E/10GeV)1/2 cm2/s Cloud at a distance
d and density 104 cm-3
31
First Unidentified TeV source TeV
J20324130
  • Found by HEGRA seredipiously (6 sigma signal
    accumulated 100h from
  • the Cygnus region and confirmed in 2002 by
    pointing observations (130 h)
  • Basic features hard power-law spectrum (photon
    index 1.9), constant flux
  • and slightly
    extended (about 5 arcmin) source
  • Origin ? leptonic (IC) origin is
    almost excluded, possibly dense gas cloud(s)
  • illuminated by
    protons arriving from a recent nearby Pevatron
    ?
  • if this object is a representative of a large
    source population, the planned survey
  • of the Galactic Disk by H.E.S.S. will
    reveal (many ?) more new hot spots
  • talk at the 2nd workshop on Unident. Gamma Ray
    Sources, Hong Kong, May 2004

32
Electrons Inverse Compton
larger field
B-field smaller than 3 10-6 G (!) source
age less than 1000 yr (!) otherwise even
for very slow (Bohm) diffusion , the g-ray source
should be largder than 5 arcmin (for d1.6kpc)
faster escape
older source
33
electrons bremsstrahlung
protons pp -gt po -gt gg
g-ray spectrum strongly depends on diffusion
coefficient D(E) D(E)1024(E/1GeV)0.5 h cm2/s
more comfortable parameters
34
A new unidentified sources is found
by HESS !
Feb 2004
March 2004
PSR1259-63
35
HESS detected new galactic sources
unidentified HESS sources
36
HESS
Aharonian et al. 2005
TeV and CO data narrow distributions in
the Galactic Plane because of GMCs ? Star
Formation Regions ? or (most likely) both ?
NANTEN CO observations
Fukui et al.2005
37
  • Origin of Extended HESS TeV sources
  • mechanisms of gamma-ray production in extended
    sources
  • characteristic timescales
  • pp p0 gg
    tpp1x1015 (n/1cm-3) -1 sec
  • e2.7 K eg
    tIC4x1012 (E/10 TeV) -1 sec
  • e-bremsstrahlung
    tbr3x1014 (n/1cm-3) -1 sec
  • IC is very effective as long as magnetic field
    B lt 10 mG
  • Bremsstrhlung important in dense, n gt 102 cm-3 ,
    environments
  • pp interactions dominate over Bremsstrahlung if
    the ratio of energy
  • densities of protons to electrons wp/we gt
    10, and Inverse Compton
  • component if wp/we gt 500 (n/1cm-3) -1
    (at energies above 10 TeV)

38
  • Morphology vs. Energy Spectrum
  • morphology pp depends on spatial
    distributions of CR and gas nH(r)xNp(r)
  • IC depends only on
    spatial distribution of electrons Ne(r)
  • energy spectra depends on acceleration spectrum
    Q(E), energy losses dE/dt,
  • age of accelerator to, and character of
    propagation/diffusion coefficient D(E)
  • pp generally energy spectrum independent of
    morphology, but for young
  • objects energy spectrum could be harder at
    larger distances than near
  • the accelerator angular size
    increases with energy
  • IC very important are synchrotrin energy
    losses
  • weak B-field ( lt10 mG) and/or fast
    diffusion

  • angular size increases with energy
  • strong B-field (100 mG) and/or slow
    diffusion

  • angular size decreases with energy
  • irregular shapes of g-ray images because of
    inhomogeneous distrubition

39
Crab Nebula an acceleration of PeV
electrons !
Standard MHD theory cold ultrarelativistc pulsar
wind (G 105-106) terminates by a reverse
shock resulting in acceleration of electrons with
an unprecedented rate tacchrL/c, h lt 100 )
synchrotron radiation gt nonthermal
optical/X-ray nebula Inverse Compton gt
high energy gamma-ray nebula
1-10MeV
.
MAGIC new !
100TeV
HEGRA
  • Crab Nebula a very powerful WLrot5x1038
    erg/s
  • and extreme accelerator
    Ee gt 1000 TeV
  • Emax60 (B/1G) -1/2 h-1/2 TeV and
    hncut(0.7-2) af-1mc2 h-1 50-150 h-1 MeV


  • h1 minimum value allowed by classical
    electrodynamics
  • Crab hncut 10MeV acceleration at 1 to 10
    of the maximum rate ( h10-100)
  • maximum energy of electrons Eg100 TeV gt Ee
    gt 100 (1000) TeV B0.1-1 mG
  • very close the value independently derived from
    the MHD treatment of the wind

for comparison, in shell type SNRs DSA theory
gives h10(c/v)2104-105
40
Challenges
  • measurements of the energy-dependent size of IC
    component
  • detection of possible hadronic component
  • gt 1 TeV neutrinos (marginally)
    detectable by Ice Cube
  • to probe location of creation and the Lorentz
    factor of kinetic energy dominated wind through
    IC scatering of wind electrons
  • cold wind can be visible/detectable in
    gamma-rays with energy
  • E me c2 x wind Lorentz factor G
    (because of K-N effect)
  • unique feature of VHE gamma-ray
    astronomy - discovery of
  • ultrarelativistic MHD flows through
    bulk motion Comptonzation

41
  • TeV gamm-rays from other Plerions ?
  • Crab Nebula is a very effective accelerator

  • but not an effective IC g-ray emitter
  • We see TeV gamma-rays from the Crab Nebula
    because of
  • very large spin-down luminosity
  • but gamma-ray flux ltlt spin-down flux

  • because of large magnetic field
  • but the strength of
    B-field also depends on
  • less powerful pulsar weaker
    magnetic field
  • higher gamma-ray efficiency
  • detectable gamma-ray
    fluxes from other plerions
  • HESS confirms this
    prediction !

Plerions Pulsar Driven Nebulae
42

MSH 15-52
dN/dE ? E-G G 2.27?0.03?0.15 ?2/n
13.3/12 Flux gt 280 GeV 15 Crab Nebula
  • the energy spectrum - a perfect hard power-law
    with photon index G2.2-2.3
  • over 2
    decades !
  • cannot be easily explained by IC
  • hadronic (po-decay) origin of g-rays ?

since 2.7 K MBR is the main target field, TeV
images reflect spatial distributions of
electrons Ne(E,x,y) coupled with synchrotron
X-rays, TeV images allow measurements of B(x,y)

43
G0.90.1 (2)
  • Spectrum
  • F(gt0.2TeV) (5.7?0.7stat?1.2syst) 10-12 cm-2 s-1
  • ?2 Crab flux, ?50 Crab luminosity
  • Power-law ? 2.40?0.11stat?0.20syst
  • Morphology
  • Compatible with a point source
  • Position compatible with the PWN position
  • Emission not consistent with the SNR shell

Radio (90 cm)
B.Khelifi
44
HESS J0835-456 (Vela X)
  • Energy Spectrum
  • F(gt1TeV) (1.23?0.12stat?0.25syst) 10-11 ph/cm2s
  • ?75 Crab flux, ?7 Crab luminosity
  • power-lawexponential cut-off
  • G 1.48 ? 0.02stat ? 0.20 syst
  • Ec 17.41 ? 1.41stat ? 3.5syst TeV
  • Morphology
  • ?L 23.4'?1.2' , ?l 15.6'?1.2'

HESS J0835-456
pulsar
IC spectrum ?
contours ROSAT
should be IC image of electrons ...
B.Kelifi, preliminary
45
PSR1259-63 - a unique high energy laboratory
  • binary pulsars - a special case with strong
    effects associated with the
  • optical star on both
    the dynamics of the pulsar wind
  • and the radiation
    before and after its termination
  • the same 3 components - Pulsar/Pulsar/Wind/Synch.
    Nebula - as in plerions
  • both the electrons of the cold wind and
    shocke-accelerated electrons are illuminated
    by
  • optical radiation from the companion star
    detectable IC g-ray emission
  • the photon field is a strong function of time,
    thus the only unknown parameter is B-field
  • TeV electrons are cooled and and radiate in deep
    Klein-Nishina regime with
  • very interesting effects on both synchrotron
    X-ray and IC gamma-rays

HESS detection of TeV gamma-rays from
PSR1259-63 at lt 0.1Crab level several days
before the periastron and 3weeks after the
periastron
but with characteristic timescales much shorter
- less than 1 h !
46
energy flux of starlight close to the
periastron around 1 erg/cm3 B-field is
estimated between 0.1 to 1 G
predictable X and gamma-ray fluxes ?
time evolution of fluxes and energy spectra of X-
and g-rays contain unique information about the
shock dynamics, electron acceleration, B(r), ...
47
while the gamma-ray energy spectrum
can be (more or less) explained by IC the
lightcurve is still a puzzle deep
theoretical (in particular MHD) studies
needed to understand the source
48
new ! HESS discovered TeV g-rays from a
microquasar !
  • LS 5039 X-ray binary - BH O7 star
  • presence of two basic components for TeV
    gamma-ray production !
  • 0.2c jet as accelerator of electrons (protons ?)
  • 1039 erg/s luminosity star as source of seed
    photons for IC or pg
  • scenario ? both gamma-ray production region
    within (despite tgg gtgt 1) and
  • outside binary system (jet
    termination site) cannot be excluded

mQSOs one of the highest priority targets of
the HESS project
49
LS5039 as a (detectable) neutrino source ? )
  • if TeV gamma-rays are produced within the
    binary system (R lt 1012cm)
  • severe absorption of gt100 GeV gamma-rays
    (g starlight -gt ee-)
  • up to a factor of 10 to 100
    higher initial luminosity
  • severe radiative (synchrotron and
    Compton) losses
  • difficult to accelerate
    electrons to multi-TeV energies
  • Conclusions ? TeV gamma-rays of hadronic origin
    with high luminosity,
  • and consequently high
    detectable TeV neutrino fluxes (!?)
  • TeV neutrino fluxes strongly depend o the
    production site of g-rays
  • the base of the jet/accretion disk and/or
    wind/atmosphere of the star
  • X-ray binaries as sources of TeV
    neutrions (V.Berezinsky, 1976, ...)


  • again a hot topic ...

) astro-ph 0508658
50
TeV Blazars and Diffuse Extragalactic

Background Radiation
  • two topics relevant to different
    research areas

TeV Blazars ideal laboratories to study particle
acceleration and MH structures in relativistic
jets, and powerful factories of GeV/TeV g-ray
beams DEBRA (also EBL, CIB,)
thermal emission components - between O/UV and
FIR produced by stars and
absorbed/re-emitted by dust,
and accumulated over the entire history of the
Universe
  • but tightly coupled through intergalactic gg
    absorption

51
impact of the intergalactic absorption on the
understanding of physics of TeV blazars
52
Models
  • SSC or external Compton currently
    most favoured models
  • easy to accelerate electrons to TeV energies
  • easy to produce synchrotron and IC gamma-rays
  • recent blazar observations require more
    sophisticated leptonic models
  • Hadronic Models
  • protons interacting with ambient plasma
    neutrinos
  • very slow process
  • protons interacting with photon fields
    neutrinos
  • low efficiency severe absorption of TeV
    g-rays
  • Proton Synchrotron
    no neutrinos
  • very large magnetic field B100 G
    accelaration rate c/rg
  • extreme accelerator (of EHE CRs) /
    Poynting flux dominated flow

expect neutrinos from EGRET AGN but not from
TeV blazars
53
X-TeV flares of 1ES 1959650 in 2002
  • Basic conclusions
  • correlations
  • X-TeV do correlate
  • No optical TeV (X) correlations
  • Radio essentialy stable
  • puzzles
  • strong TeV flare on June 4 not
  • accompanied by an X-ray activity
  • MAGIC also does not see strong
  • TeV-keV correlations
  • hadronic origin of TeV emision ?
  • actually pg implies stronger TeV-X
  • correlations than IC models

54
1ES 1426428 a different blazar ?
IC ?

Proton synchrotron?
  • 1ES 1426428 does not agree with
  • the red-blue phenomenology

55
Cooling and acceleration times in Markarian 501
in TeV blazars synchrotron cooling time always ltlt
photomeson colling time
no neutrinos from TeV
blazars
no VHE gamma-rays from most powerful and distant
AGN and QSOs but (possibly)
detectable fluxes of VHE and UHE neutrinos
56
  • TeV g-rays - carriers of unique cosmological
    information
  • about epochs and
    history of evolution of galaxies
  • such information can be extracted through
    studies of intergalactic
  • absorption features in the energy spectra of
    blazars of given z, if
  • one can unambiguously identify the
    intergalactic absorption features
  • two (both not perfect) approaches
  • measure the intrinsic spectrum based on
    comprehensive time-
  • dependent modeling of multiwavelength
    data (broad band SED)
  • a very hard problem
  • accept a principle the intrinsic spectrum
    Jo(E)Jobs(E) expt(E) should be reasonable
  • but what means
    reasonable ?
  • or if gamma-rays are of hadronic (pp -gt
    po-gtgg) origin
  • measure the spectrum
    of TeV neutrinos
  • a dream and still not sufficient
    (intrinsic absorption of gs)

absorption does not mean spectral cutoff
57
New blazars detected at large z ! HESS
H2356-309 (z0.165), 1ES1101-232 (z0.186)

MAGIC 1ES1218304
(z0.182)

HESS
1 ES 1101 G 2.90.2
H 2356 (x 0.1) G 3.10.2
Preliminary
58
reconstructing gamma-ray spectra with different
EBL models
HESS collaboration, submitted to Nature
59
HESS robust upper limits on EBL at O/NIR
  • EBL (almost) resolved at NIR
  • Universe more transparent
  • intrinsic gamma-ray spectra

direct measurements
upper limits
lower limits from galaxy counts
60
1ES1426428 - a special case
  • many puzzles
  • difficult to believe... TeV gamma-rays from
    this source at z0.129 despite
  • the intergalactic absorption gtgt 10
  • TeV peak significantly higher than the X-ray peak
  • violation of the red-blue blazar
    paradigm cannot be easily explained
  • by standard SSC or external Compton models
  • only a specific class of EBL models allows
    reasonable instrinsic TeV spectrum

61
TeV g-rays from GC
GC a unique site that harbors many
interesting sources packed with un-
usually high density around the most
remarkable object 3x106 Mo SBH Sgr A
many of them are potential g-ray emitters -
Shell Type SNRs Plerions, Giant Molecular
Clouds Sgr A itself, Dark Matter
HESS FoV5o
all of them are in the FoV HESS ! and can be
probed down to a flux level 10-13 erg/cm2 s
and localized within ltlt 1 arcmin
62
Position?
systematic and statistical errors on source
location by HESS are comparable
20-30 arcseconds
63
two comments
  • typically (often) theorists face problems of
    interpreting g-ray
  • observations in the frameworks of
    "standard" models, but in the
  • case of TeV observations of GC we face an
    opposite problem
  • TeV data can be explained within several
    (essentially different)
  • scenarios and by several
    different radiation mechanisms
  • the FoV, PSF, and sensitivity of HESS (and
    GLAST) perfectly match
  • the performance of other relevant instruments
    at other wavelengths
  • (Chandra, XMM, INTEGRAL, VLT, radio and mm
    telescopes, etc.)
  • both for compact objects like Sgr A and
    diffuse structures
  • HESS and GLAST can provide perfect temporal,
    spectroscopic and
  • morphological studies over six (100 MeV
    to 100 GeV) g-ray decades

64
TeV g-rays from central lt10 pc region of GC
  • Annihilation of DM ? mass of DM particles gt 10
    TeV ?
  • Sgr A 3 106 Mo BH ? yes, but lack of
    variability
  • even the inner R lt 10 Rg region is
    transparent for TeV g-rays !
  • SNR Sgr A East ? why not ?
  • Plerionic (IC) source(s) why not ?
  • Interaction of CRs with GMCs ? easily

65
Sagittarius A - point-like but not variable
syst. error
power-law index 2.3
Contours - radio
66
Point-like but not variable TeV source an
argument in favor of DM origin of detected TeV
gamma-rays ?
  • angular size of TeV signal can be explained by
    DM annihilation for
  • n(r) profile like r-a with a gt 1.1 i.e.
    Qg(r)C1n2 Qor-2a
  • but the absolute intensity of the TeV signal
    requires much sharper
  • density
    profile n(r) within lt 0.1 pc
  • Note that the same can be the case of CR
    interactions with gas
  • Qg(r)C2ncr(r)
    nH(r)Qor-(a1a2) ,
  • e.g. CR density decreases like r-2 and the gas
    density like r-0.2
  • absolute g-ray fluxes can be explained naturally
    by interactions
  • of run-away
    protons with surrounding dense gas

C1 and C2 interaction constants
(cross-sections)
67
A concluding remark
  • We are just at the gates of the Paradise of
  • TeV astrophysics and
    Cosmology
  • condition for entrance? FE gt 10-14 erg/cm2 s
    (0.03-100 TeV)
  • realization ? 1 to 10 km2
    scale IACT arrays (super-HESS)
  • timescales short (years)
    - no technological challenges
  • price for the ticket very reasonable
    including

  • (almost) 100 guarante for

  • the success (great discoveries)
  • several tens (100 ?) of 15m diameter class 5
    deg FoV telescopes

  • located on 3.5-4 km
    a.s.l.
  • another major objective reduction of the
    energy threshold down to

  • lt 10 GeV energies (different approaches,

  • different astrophysical objectives /motivations)
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