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)

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HADRONIC

LEPTONIC

MOLECULAR CLOUDS

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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

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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

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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

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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

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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

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• 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

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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

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• 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

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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

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12CO(1-0)

MOPRA DATA13CO(1-0)

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SGPS DATA

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HI

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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

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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

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• 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

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• 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