Interstellar medium towards the unidentified gamma-ray ...
Transcript of Interstellar medium towards the unidentified gamma-ray ...
Interstellar medium towards the unidentified gamma-ray source HESS J1804-216
Kirsty Feijen
TALK OUTLINE
2
• High Energy Stereoscopic System Galactic
Plane Survey (HGPS)
• Production of gamma-rays
• Interstellar medium
• Intro to HESS J1804-216
• Multiwavelength studies
• Local region
• Moment scripts
• Mopra Data
• 12CO and 13CO
• SGPS Data
• HI
• Most recent work: Maser emission
ɣ
HESS
3
4 x 12m diameter telescopes since 2003
1 x 28m diameter telescope since 2012
Latitude: ±3.5°
Longitude: ±30°, 250° to 65°
(1/2)
• 3 Binary
• 8 Composite
• 8 SNR
• 12 PWN
• 36 Unidentified
4
Donath et al, ICRC 2015 HESS (2/2)
PRODUCTION OF -RAYSɣ
e
• Pi-zero decay
• Bremsstrahlung
• Inverse Compton
• Synchrotron
Radiation
ɣ
ISM gas
p
e
e
π0 ɣ
ɣ
ɣe
p
Low energy ɣie CMB
Magnetic field
e
ɣ (different types)
5
HADRONIC
LEPTONIC
MOLECULAR CLOUDS
6
GAMMA RAYS
CR DEFLECTED BYMAGNETIC FIELDS
MOLECULAR CLOUD
• Dense regions of gas give information about gamma-ray sources
• Clouds serve as a target for CR collisions
• Important to understand the interstellar gas surrounding a source
INTERSTELLAR MEDIUM
7
Mopra
TELESCOPE
3mm: 12
CO, 13
CO, C18
O, C17O
7mm: CS(1-0), SiO
12mm: NH3
HESS Fermi
Parkes ATCA
+ 21cm line: HI
DETECTS GAS DENSITY
GAMMA-RAYS
20MeV to 300GeV
102 -10
3cm
-3
103 -10
5cm
-3
101to 10
3cm
-3
100
to 102
cm-3
100GeV to 10’s of TeV
AROUND THE WORLD
8
NantenHESS
Mopra
Parkes
HESS J1804-216
9
Galactic LongitudeG
alac
tic
Lati
tud
e
• Origin of high energy CRs is a
mystery
• -rays provide information
on the high energy
astrophysical environments
• Studying various -ray
sources helps us understand
the extreme universe
ɣ
ɣ
• HESS J1804-216 is focus
• 3FGL= Fermi Bright -ray source List
• 3FHL= Fermi Hard source List
ɣ
Above: HESS J1804-216 excess counts map
MULTI-WAVELENGTH
• HESS J1804-216 shines
brightly in gamma rays
• flux of 25% of the Crab
Nebula
• The other wavelengths are
not as excited
Left: Energy spectrum for HESS J1804-216, from
the HESS array and Fermi telescope
10
HESS collab 2018Lin et al 2013Frail et al 1994
Radio Microwave Infrared Visible X-ray Gamma Rays
VLA Planck Spitzer UK Schmidt XMM-Newton HESS
HESS J1804-216
ASIDE: GRC
11
• Distances to sources
not easily resolved
• Doppler shifting of
spectral lines allows
us to estimate them
• Objects in the galaxy
rotate around the GC
• GRC gives average
velocity wrt GC
• 2 solutions are
found:
• Near & far
kinematic distances
Left: Galactic Rotation
Curve for HESS J1804-216
LOCAL REGION
12
SNR 8.3-0.1
• Size: 5’x4’
• Distance: 16.3kpc
SNR G8.7-0.1
• Age: 15 kyr
• Radius: 26’
• Distance: 4.5 kpc
PSR J1803-2137
• Spin down power: wedf
• Age: 16 kyr
• Distance: 3.8 kpc1720MHz OH Maser
• Distance: 4.6 kpc
Galactic Longitude
Gal
acti
c La
titu
de
• PSR J1803-2137 born outside SNR G8.7-0.1, requires huge transverse velocity
• Likely moving towards it rather than away from it -> no connection
MOMENT MAPS
13
• Region is taken around the
contours of HESS J1804-216 of
the data cube
• Doppler shifted velocity along the
z-axis
• Two moment maps used are
moment0 and moment2
Galactic Longitude
Gal
acti
c La
titu
de
• Moment 0 - integrates over the selected velocity regions employing the
equation:
𝑀0 = ∫ 𝐼 𝑣 𝑑𝑣• Moment 2 - velocity dispersion map
SPECTRA
14
Left: Mopra uncleaned vs Mopra cleaned data set for 12
CO
Velocity range (km/s) Label
-27 to -10 A
-10 to 8 B
8 to 26 C
26 to 56 D
56 to 105 E
Right: Mopra
12CO and
13CO
spectra
towards HESS
J1804-216
• Ignore the Nanten data for now:
• Mopra has better resolution
• Mopra Galactic Plane CO survey data
• 12CO and 13CO
MOPRA DATA
15
12CO(1-0)
MOPRA DATA13CO(1-0)
16
SGPS DATA
17
HI
18
Right: Mopra12
CO spectra taken
from the data cube placed at
36km/s
• See two peaks in this
spectra centred on:
• 18 km/s
• 36 km/s (maser velocity)
• Bright OH maser discovered by Hewitt & Yusef-Zadeh in 2008
• Emission is a good tool for probing astrophysical phenomena eg SNRs
• Two different surveys for hydroxyl (OH), THOR and SPLASH
• THOR – survey of HI and OH emission in the Milky Way
• not available for this source
• SPL – OH survey with Parkes
• not yet publicly available
MASER EMISSION(1/2)
MASER EMISSION
• Made over a smaller range -
> showing turbulence of
individual clouds
• Clip value for moment 2 map
chosen from the rms
sensitivity per channel:
• 12CO clip=1.5K
• 13CO clip=0.7K
19
Galactic Longitude
Gal
acti
c La
titu
de
Right: Crop region ~ 0.5° x 0.5°
around the 1720MHz OH maser
Below: Moment 2 maps
for 12
CO (top) and 13
CO
(bottom) with Moment
0 contours (cyan)
(2/2)
OH MASER EXAMPLE
• Analyse the 7mm data
covering disrupted gas
towards W28 SNR
• Broad line emission is in
all detected lines
• “Velocity dispersion of
broad gas further
supports the idea that
SNR W28 is the source
of molecular disruption”20
Left: Velocity dispersion map for CS(1-
0) emission with clipping of 0.5 K.
Black contours are for HESS J1801-233
• Need to analyse the gas more closely
towards the maser for my source
• Using CS data could be helpful
A 7mm line survey of the shock and disrupted molecular gas towards the W28 field TeV gamma-ray sources, B Nicholas et al, 2011
SUMMARY
21
• Showed the various gas tracers that
will be used through-out the project
• Where the telescopes are located
• HESS J1804-216 analysed, including a
multi-wavelength look
• Looked into the Mopra12CO and 13CO
data
• Also looked at the SGPS HI data
• Started looking at the area towards the
1720MHz OH maser to see for disrupted
gas
FUTURE STUDIES
22
• Next step is to start processing some
new data in the 7mm, in particular CS
data
• Telescope gives us rpf files
• Need to use Livedata and Gridzilla
to process these into fits cubes
• Will then use the moment 0 scripts
on the previously selected velocity
ranges
• Can then do a more in depth
analysis with the OH maser
• Start writing my paper on this work