Galactic sources of VHE gamma rays

1
Typical sensitivity of modern arrays (H.E.S.S.,
VERITAS) 1 Crab in some 10 h Threshold 100
GeV Angular resolution 0.1o MAGIC Threshold
25 GeV, few Crab sensitivity

2
H.E.S.S. Phase II

• 600 m2 dish, 2000 x 0.07o pixel camera
• Extends energy range down to 30 GeV
• Improves sensitivity in 100 GeV TeV range in
  stereo mode

Photo montage
3
H.E.S.S. Phase II
Reality
4
MAGIC II Stereo, 2 x 236 m2
First light ceremony April 25, 2009
85 m
5
MAGIC II Positioning in 20 s
6
MAGIC II
MAGIC I 397 x 0.1o pixels (FoV 2o), 180 x 0.2o
MAGIC II 1039 x 0.1o pixels FoV 3.2o
7
VERITAS
Fall 2009
T1 Jan 2005 T2 Spring 2006 T3 Fall 2006 T4
Spring 2007
1200 ft2 mirror area 499 x 0.15o pixels FoV 3.5o
8
VERITAS
Fall 2009

• 2009
• improved optical psf
• move T1 for better sensitivity and angular
  resolution
• Proposed upgrades
• High-QE PMTs (35)
• Trigger upgrade (topology)

9
CANGAROO III
A most remarkable piece of archeology arXiv0906
.4924 Early CANGAROO (3.8 m) claims for
discovery of PSR B1706-44, SN1006 cannot be
reproduced problems in old (1993
1999!) calibration and analysis identified

• Operational, but modest performance compared to
  other arrays
• Modest dish size (57 m2)
• Sea-level altitude
• Serious mirror deterioration (10 / year)
• Partly outdated camera hardware

10
TeV astronomy in India
MACE 356 m2 2011/12
PACT Array, Pachmari
TACTIC, Mt. Abu
x 25
First data HAGAR Array, Hanle
11
Air shower arrays
M. Amenomori et al., arXiv0810.3757
MILAGRO Water Cherenkov, ceased operation in
2008, after 7 years Tibet III Scintillator
array arXiv0810.3757, 0804.1862 CR spectra, moon
shadow, Crab Mrk 421, 3 hotspots ARGO-YBJ 6700
m2 RPC carpet arXiv0907.1164, 0905.1189,
0811.0997 Sun moon shadow in CR Crab
Mrk421, GRB search P-Air Xsection, pbar-p ratio
Tibet III Crab
12
ARGO-YBJ
S. Vernetto et al. ICRC 2009
5o smoothed
Scale 0.1
Mrk 421
Crab
High-pass filtered
13
Outline

• Instrument status
• Surveying the Galaxy in VHE gamma rays
• Source classes their astrophysics
• Supernova remnants
• Pulsar wind nebulae
• Unidentified / dark sources
• Binaries
• Stellar clusters
• No DM, electrons,

Apologies for many omissions!
14
Surveying the Galaxy in VHE gamma rays
15
The Galactic Plane in gamma rays
R. Chaves ICRC 2009
L 60o
L -85o
almost all sources extended
16
VERITAS survey of Cygnus region
A. Weinstein ICRC 2009
Effective exposure
1.0o
0.8o

• Source search with r0.11o, 0.24o regions
• No hotspots above 5s post-trials in base survey
• Limits 3 Crab flux for point sources at
  points below 3s
• 8.5 Crab flux for extended 0.2o sources

17
MILAGRO survey
B. Dingus
Cygnus region
J190806
Geminga Crab
Energy range 5 100 TeV
18
Source sizes shapes
For uniform distribution of targets, ? g-rays
probe particle distribution Typical lifetime of
electrons is 10s of kyr, of protons 100s of kr ?
range 10s of pc, unless confined by strong
magnetic fields or radiative losses ?
typically large diffuse sources ? electrons
are more effective radiators
Source of particles (e.g. pulsar)
Target material Gas for po production by
protons CMB, IR, optical for IC upscattering of
electrons
19
Supernova remnants as cosmic ray sources (?)
20
SRN with resolved shells
Latest addition SN 1006 expands in uniform
environment above the Galactic plane
VHE g-rays
2 4.5 keV X-rays
smoothed X-ray contours
Flux 1 Crab
H.E.S.S. prelim.
21
SN 1006
Azimuthal profile VHE vs X-rays
M. Naumann-Godo ICRC 2009 Moriond 2009
Spectral index 2.4 Flux 1 Crab
Energy spectra For both regions
22
SNR models
RX J1713.7-3946 Berezhko Völk astro-ph/0602177
Synchrotron radiation
po decay
Shock speed 1840 m/s e/p 10-4 B 126
mG asymptotically e ? 50
23
Acceleration in Supernova Remnants

• Some (Experimentalists) Questions
• Do SNR shocks accelerate particles to VHE
  energies? ?
• What is the p/e ratio among accelerated
  particles?
• What is the acceleration rate / acceleration
  time?
• Where does acceleration cut off? Do SNR
  accelerate CRs up to the knee are they
  Pevatrons?
• How efficiently is shock kinetic energy converted
  to CR energy?

24
e or p Supernovae interacting with clouds
IC 443 VERITAS MAGIC
Wardle et al. 2002
maser
IC 443 MAGIC 2007, arXiv0705.3119 VERITAS 2007,
2008 arXiv0810.0799
25
e or p Supernovae interacting with clouds
A. Fiasson, ICRC 2009
W 51 / G49.2-0.7
W 28
arXiv0801.3555
maser emission
Also 0FGL J1923.01411 MGRO hotspot
H.E.S.S.
26
SNR acceleration efficiency RCW 86
Helder et al., Science 2009
RCW 86 Age 2 kyr (?) Dist. 2.5 kpc (?)
Measured shock velocity 60002800 km/s (Chandra
2004,07) Expected post-shock gas
temperature 4270 keV Measured post-shock
temperature 2.30.3 keV (Ha line width) ? gt50 of
energy in non-thermal component (C.L. ?)
27
Who no Pevatrons?
(A) Lack of gamma-ray statistics
RCW 86 G 2.40.20.2
H.E.S.S. arXiv0810.2689
(B) Lack of source statistics With decreasing
shock speed, acceleration CR confinement
become less effective ? PeV particles only for
some 100 1000 years ? At any time maybe only
few pevatrons in Galaxy
28
The dominant speciesPulsar wind nebulae
29
Pulsars pulsar wind nebulae
van der Swaluw, Downes, Keegan 2003
G21.5-0.9 Chandra
SN shock accelerates particles for O(10 ky)
Pulsar sustains pulsar wind nebula for O(100 ky)
30
Interaction of shell and PWN
Vela X H.E.S.S.
31
Pulsars pulsar wind nebulae

• Dominant population among Galactic VHE sources
• Pulsar X-ray PWN discoveries in VHE sources
• Pulsars G0.90.1, HESS J1809-193, HESS
  J1833-105, HESS J1837-069, HESS J1857026
• X-ray PWN HESS J1616-508, HESS J1640-465, HESS
  H1718-385, HESS J1813-178, HESS J1833-105, HESS
  J1845-029
• Very extended sources 10s of pc
• Often significant displacement from pulsar
• Origin of emission sometimes
• ambiguous (PWN or unresolved
• SNR)

32
New PWN / PWN candidates
S. Wakely ICRC 2009
G54.1 0.3 / PSR J19301852 Chandra
VERITAS
LAT PSR
Crab-like pulsar 1.2 x 1037 ergs/s
VERITAS point source
Boomerang / PSR J22296114 Black contours radio,
purple CO Also MGRO source
33
PSR B1706-44 - a pulsar with VHE history
CANGAROO III ICRC 2009
H.E.S.S. ICRC 2009
source size s 0.6o Crab-level flux
source size s 0.3o 17 Crab
34
The most distantN 157B / PSR J0537-6910 in LMC
Nu. Komin ICRC 2009
About 1 of spin-down lumi of 5 x 1038
ergs/s visible in 1-10 TeV g-rays
Consistent with 0FGL J0538.4-6856 (30 Doradus?)
XMM-Newton
H.E.S.S. preliminary
6, 8.5, 11 s H.E.S.S. contours
SN 1987a in FoV upper limits close to
predicted flux
35
VHE source
Sorted by Spin-down flux
36
Pulsars in HE vs VHE
Abdo et al., ApJ Lett in press, 2009.
14 of 34 Fermi Bright Sources in Milagro FoV
have gt3s 9 of 16 LAT PSR have gt3s Most strong
PSR extend into Multi-TeV regime
Geminga 0FGL J06341745
LAT PSR J203241 , HEGRA,MAGIC,
37
Clearest pattern X-ray vs VHE luminosity
Old pulsars VHE emitting electrons accumulate
over 10s of kyr Low B field synchroton falls
below X-ray range Young pulsars VHE emitting
TeV electrons still building up X-ray emitting
electrons already in equilibirum Higher B field
Old PWN are X-ray dark
old (105 y)
young (103 y)
Mattana et al. arXiv0811.0327
38
HESS J1303-631 a pwn?
M. Dalton ICRC 2009
Aharonian et al., astro-ph/0505219
M. Dalton ICRC 2009
39
Complex source morphologies
E. de Ona Wilhelmi ICRC 2009
one of several instances where complex
sources decompose into multiple objects
HESS J1023-575 Combination of a hard source,
compatible with PSR J1028-5819, 0FGL
J1028.6-5817) and a softer source (Wd 2, OFGL
J1024.0-5754)
above 2.5 TeV
0.75 to 2.5 TeV
40
First ground-baseddetection of pulsedemission
from a pulsarMAGIC, Science 322, 2008using
special low-energy trigger
41
Origin of pulsed emission outer gap
Emission from polar cap and slot gap cut off
around 10 GeV due to pair production
EGRET
MAGIC
42
Binaries
43
Gamma-ray binaries
H.E.S.S.
MAGIC VERITAS
ICRC 2009 New results on 2nd orbit
Binaries Laboratory to study how particle
acceleration reacts to periodically varying
conditions (radiation fields, B-fields, )
MAGIC
H.E.S.S.
Periodic emission
44
LS I 61 303
MAGIC arXiv0809.4254, ICRC 2009, also VERITAS
arXiv0904.4422
Periodic variation Of VHE flux along 4 orbits
MAGIC
Orbital frequency
3rd harmonic
Periastron
45
Variability of HESS J0632057- a new gamma-ray
binary?
HESS J0632057One of the few point sources in
the Galaxy survey Consistent with MWC 148, Rosat
source
XMM
Hinton et al. arXiv0809.0584
Acciari et al. arXiv0905.3139
46
Stellar clusters
47
Young stellar clusters / star forming regions
W43 SFR
Wd 1
Wd 2
Collective stellar winds (OB, WR) ? Colliding
wind binaries ? First SNR ? First PWN ?
J1023575
HESS J1848-18
48
Old stellar clusters globular clusters

• Object PSR Flux (C.U.) Exp.
• M5 5 lt 0.6 VERITAS
• M13 8 lt 2 MAGIC
• lt 2 VERITAS
• M15 8 lt 1.6 VERITAS
• 47 Tuc 23 lt 2 H.E.S.S.
• Limits within a factor of few from
• fluxes predicted for shock acceleration
• in colliding pulsar winds constraints
• on number of undetected PSR

47 Tucanae (Chandra)
106 M?, 23 pulsars Fermi-LAT source
Aharonian et al., arXiv0904.0361 Anderhub et
al., arXiv0905.2427 McCutcheon, ICRC 2009
49

• objects
• in default catalog

TeVCaT
50
19 objects newly announced
TeVCaT
Will reach 100 objects with current
instruments Improved instruments (soon) online (x
3) Next generation in planning (x 10)