A MAGIC picture of our Galactic Center Christian Fruck - - PowerPoint PPT Presentation

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A MAGIC picture of our Galactic Center

A MAGIC picture of our Galactic Center

Christian Fruck

fruck@mpp.mpg.de Max-Planck-Institut für Physik PPMSC - München - 2015

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results

Observability of the GC from the MAGIC site Results Speculations

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

Some of the most important reasons ...

◮ The GC hosts the by far closest Super Massive Black Hole

(SMBH) to Earth

◮ Studying the GC might finally allow for testing new theories

describing Gravity in a quantum-mechanical framework

◮ Spatial/angular resolution of sub Event Horizon scales of the

GC BH in radio and optical are only few years away

◮ The DM concentrated at the GC , if annihilating/decaying should

be the most luminous when observed from Earth

◮ Therefore the GC is one of the best candidates for indirect DM

searches

◮ The GC is a very dense and active environment, from an

astrophysical point of view

◮ It hosts star forming regions with plenty of molecular gas, heavy

young stars, and many supernova remnants

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

Putting the Galactic Center into context

Milky Way galaxy:

◮ disk (30 kpc x 0.3 kpc): young stars, gas, molecular clouds, dust ◮ bar (4.5 kpc) and bulge (1.5 kpc): old stars low star formation ◮ Galactic Center (250 pc): dense molecular clouds high star formation

rate

image source: en.wikipedia.org 4 / 33

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

GC region in 20cm, 1.1mm, IR

◮ VLA (20cm): H II regions that are illuminated by hot, massive stars,

supernova remnants, and synchrotron emission

◮ Caltech Submillimeter Observatory (1.1mm): cold (20-30 K) dust

associated with molecular gas

◮ Spitzer (IR): primarily emission from stars and from polycyclic aromatic

hydrocarbons

image source: http://images.nrao.edu 5 / 33

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

Radio sources SgrA and SgrA*

◮ bright point-like radio source ◮ at the center of SgrA-West (Mini-Spiral) ◮ at the edge of SNR SgrA-East ◮ thought to be SMBH ◮ from stelar motions: ≈ 4 · 106 M⊙

image source (left): N. E. Kassim, D. S. Briggs, T. J. W. Lazio, T. N. LaRosa, J. Imamura (NRL/RSD) image source (right): astro.ucla.edu 6 / 33

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A MAGIC picture of our Galactic Center Why are astronomers so fascinated by the Galactic Center?

The Galactic Center S-star cluster — stellar motion reveals the SMBH

◮ few 10 OB stars confined inside the central arc-sec around SgrA* ◮ star S2 periastron: 120 AU, period: 15.6 y

refer to for example: Ghez, A. M., et al. The Astrophysical Journal 509.2 (1998): 678. 7 / 33

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A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign

Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results

Observability of the GC from the MAGIC site Results Speculations

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A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign

G2 gas cloud falling onto the Galactic Center

◮ Reports by ESO about a gas cloud of three times the Earth mass on its

way to SgrA* (S. Gillessen et al. 2012)

◮ Pericenter passage 2013-2014, ≈ 2000 Schwarzschild radii (20 light

hours) (S. Gillessen et al. 2013)

◮ Tidal disruption of the cloud has already begun 2011 ◮ Likely that part of the cloud will be subjected to accretion in the

upcoming years ⇒ Monitoring campaigns triggered in nearly all wavelengths

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A MAGIC picture of our Galactic Center Triggering event for the MAGIC observation campaign

Possible scenarios

Rough summary of possible observable accretion scenarios:

◮ Formation of a hot accretion disk

⇒ Production of thermal X-rays (X-ray satellites)

◮ Production of energetic electrons

⇒ Synchrotron radiation from Radio to X-ray from energetic electrons (Radio telescopes, X-ray satellites) ⇒ Bremsstrahlung and/or Inverse Compton scattering of high energy e− ( ray satellite observatories, ground based ray observatories)

◮ Acceleration of protons and heavy nuclei

⇒ 0 production in interaction of hadronic cosmic rays ( ray satellite

• bservatories, ground based ray observatories)

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results

Observability of the GC from the MAGIC site Results Speculations

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

IACTs in context of other Instruments

4 k m 2 k m 1 k m

γ

HE

N2, O2, O3, O H2O CO2 EAS

10 6 m 1 Mm 10 3 m 1 km 10-3m 1 mm 10-9m 1 nm 10 -12m 1 pm 1 am 10 m

• 18

1 m µ 10-6m 10 -15m 1 fm 1 m

radio

eV 1 eV

IR UV

1 keV 1 MeV 300 GHz 300 kHz 300 MHz eV

1 mm

1 EeV

18

1 PeV eV 10

15

1 TeV eV 10

12

1 GeV eV 10

9

eV 10

6

eV 10

3

eV 10

• 3

eV 10

• 6

eV 10

• 9

eV 10

• 12

10

• 15

10

VHE X UHE

visible Cosmic microwave background, ~3 mm

γ-rays

satellites radio telescopes

• ptical

telescopes balloons rockets Cherenkov telescopes fluorescence detectors 50% of incident radiation absorbed particle detectors Earth surface

image credit: Robert Wagner 12 / 33

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Extended air-showers

EM (left) and hadronic (right) shower and Atmospheric MC simulations (center)

e+ e+ e- Primary e- e+ e+ e- e+ e- e-

e- e- e+ e+

+ K , etc. Nucleons, K , etc. Nucleons,

Cosmic Ray (p, , Fe ...)

Atmospheric Nucleus EM Shower EM Shower EM Shower Atmospheric Nucleus

image credit: Robert Wagner / CORSIKA 13 / 33

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Imaging Air Cherenkov Telescopes γ

Extensive Air Shower Cherenkov Light Reconstructed Source Position Cameras with PMT pixels Air Shower Images Impact point 14 / 33

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

The MAGIC telescopes

◮ located on the Roque de los Muchachos (at 2200 m a.s.l.) on the Canary island La Palma ◮ Two 17m diameter parabolic single-mirror telescopes consisting of 239 1 m2 mirror panels each ◮ Support structure from carbon fiber can rotate 180◦ in about 20 s

image credit: Robert Wagner 15 / 33

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Images recorded by the cameras of the MAGIC telescopes

◮ The two cameras consist of 1039 photomultiplier pixels each (3.5◦ FoV) ◮ Events last only a few ns ◮ Different coincidence criteria (charge concentration in small region of

camera in one and simultaneous such events in both telescopes) required for the events to be recorded

◮ Typical CR event rate 300 Hz ◮ Event classification offline via Random Forests

CleanData Mean 2.341 RMS 4.346 187mm ° 0.60

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1 5 9 13 17 21 25 29 32 36 40 44 48 52 56 60

L

CleanData Mean 2.546 RMS 2.107 187mm ° 0.60

1 2 3 4 5 7 8 9 10 11 12 13 14 16 17 18

L

CleanData Mean 3.781 RMS 3.707 187mm ° 0.60

2 4 6 8 11 13 15 17 19 21 23 26 28 30 32 34

L

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Short excursion: How are VHE -rays produced?

◮ -rays in the TeV regime are exclusively of non-thermal origin. ◮ They are always produced as a by-product of the acceleration of

charged particles to VHE

◮ The favored acceleration scenarios are: Diffusive shock acceleration

and acceleration in rotating magnetic fields (Pulsars, BH plerions)

u = β c u2 u4 u5

magnetic mirror v θ θ charged particle

x u1

u = β c

strong shock-wave

v ≈ c

charged particle

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A MAGIC picture of our Galactic Center Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC

Short excursion: How are VHE -rays produced?

◮ -rays are then produced via: ◮ Leptonic: Bremsstrahlung, Curvature radiation, Inverse Compton

scattering (IC) – mostly on synchrotron radiation produced by the same population (SSC)

◮ Hadronic: decay of 0 form pp interaction

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results

Why are astronomers so fascinated by the Galactic Center? Triggering event for the MAGIC observation campaign Introduction to Imaging Air Cherenkov Telescopes (IACTs) and MAGIC The MAGIC GC observation campaign and results

Observability of the GC from the MAGIC site Results Speculations

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site

Observability of the GC

◮ Source declination of -29◦ ⇒ culminates at 58◦ zenith distance

⇒ Observation at large zenith (58◦ – 70◦) distance with all advantages and disadvantages (light pool size vs. light dilution, enhanced absorption ...)

0° Zd 60° Zd 10 km

E [GeV] 10

2

10

3

10

4

10 1 10

2

10

3

10

4

10

5

10

6

10 Aeff [m2]

100 200 300 400 500 600 700 800

3

10 × CrabGlowGZd EntriesG 3772219 MeanG 17.27 RMSG 7.65 GalacticGCenterGobs. EntriesG 1.968662e+07 MeanG 64.01 RMSG 2.553

50 10 20 30 40 60 70

ZdG[°] Entries

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Observability of the GC from the MAGIC site

Observed about 60 hin total!

◮ Total observability throughout the year (only about 1/3 of the year available for monitoring)

• 4
• 2

2 4 6 56650 56700 56750 56800 56850 56900 56950

Visibility:1GalacticCenter1(zd1< 70.0)

starting Date (MJD) Time (past UTC midnight)

29.11 24.12 18.1 12.2 9.3 3.4 28.4 23.5 17.6 12.7 6.8 31.8 25.9 20.10 14.11

◮ Due to limited trigger delay between both telescopes, part of the observable window is lost

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

Lightcurve (Is the flux variable?) – constant flux (correlated fit)

F(t) = F0

56000 56100 56200 56300 56400 56500 56600 56700 56800 MJD 2 4 6 flux [m−2 s−1 ] 1e 12

χ2 / ndf 8.0 / 10 Prob 0.63 F0 2.3e-12 ± 6.2e-13 χ2 / ndf 13.5 / 10 Prob 0.20 F0 8.7e-13 ± 2.4e-13 χ2 / ndf 6.9 / 10 Prob 0.73 F0 2.3e-13 ± 6.5e-14 E > 1 TeV E > 2 TeV E > 5 TeV 22 / 33

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

Lightcurve (Is the flux variable?) – linearly increasing flux (correlated fit)

F(t) = F0 + (t[MJD] − 56000)

56000 56100 56200 56300 56400 56500 56600 56700 56800 MJD 2 4 6 flux [m−2 s−1 ] 1e 12

χ2 / ndf 6.4 / 9 Prob 0.70 F0 1.8e-12 ± 6.2e-13 α 8.8e-16 ± 7.4e-16 χ2 / ndf 10.4 / 9 Prob 0.32 F0 6.0e-13 ± 2.3e-13 α 5.4e-16 ± 3.4e-16 χ2 / ndf 4.7 / 9 Prob 0.86 F0 1.5e-13 ± 7.2e-14 α 1.6e-16 ± 1.2e-16 E > 1 TeV E > 2 TeV E > 5 TeV 23 / 33

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

Spectral Energy Density (SED)

◮ MAGIC SED (flux per relative bandwidth) compared to other measurements ◮ Power-law with exponential cutoff fit: dF

dE = f0

• E

1TeV

−2.0 exp−

E 10TeV E [GeV]

3

10

4

10

]

• 1

s

• 2

[TeV cm dE dA dt dN

2

E

• 14

10

• 13

10

• 12

10

• 11

10

MAGIC, this work 0.2 deg (Schmelling) MAGIC, this work 0.2 deg (Forward) MAGIC, this work 0.1 deg (Forward) H.E.S.S., Aharonian et al. 2009 VERITAS, Archer et al. 2014

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

Spectral Energy Density (SED) – MAGIC and Fermi (same source?)

◮ Correlated fit: dF

dE = f0,1

• E

5GeV

1+1 log

• E

5GeV

• + f0,2
• E

3TeV

2+2 log

• E

3TeV

• 10-2

10-1 100 101 102 103 104 105

Energy [GeV]

10-14 10-13 10-12 10-11 10-10 10-9

SED [TeV cm−2 s−1 ]

χ2 / ndf 28.2 / 14 Prob 0.01 f0,1 1.6e-06 ± 1.7e-07 α1 -2.53 ± 0.03 β1 -0.13 ± 0.02 f0,2 3.4e-13 ± 1.0e-13 α2 -2.26 ± 0.12 β2 -0.52 ± 0.28 χ2 / ndf 19.0 / 14 Prob 0.17 f0,1 1.6e-06 ± 1.7e-07 α1 -2.52 ± 0.02 β1 -0.13 ± 0.02 f0,2 1.8e-13 ± 5.7e-14 α2 -2.24 ± 0.14 β2 -0.71 ± 0.47 χ2 / ndf 16.1 / 14 Prob 0.31 f0,1 1.6e-06 ± 1.7e-07 α1 -2.54 ± 0.03 β1 -0.14 ± 0.02 f0,2 2.2e-13 ± 6.9e-14 α2 -2.30 ± 0.12 β2 -0.50 ± 0.28 Fermi, Chernyakova et al. 2011 MAGIC, this work, 0.4 deg MAGIC, this work, 0.1 deg MAGIC, this work, 0.2 deg

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

Skymaps: MAGIC and 90cm radio

◮ Morphology can definitely not be explained by point source ◮ Resembles quite much the 90 cm radio image – but what causes the TeV radiation?

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

GC skymaps MAGIC, E > 1Tev (∼60h)

◮ Image before (left) after (right) the subtraction of a point source

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Results

GC skymaps MAGIC, E > 3Tev (∼60h)

◮ Image before (left) after (right) the subtraction of a point source

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Source candidates for extended emission

◮ Expanding giant molecular cloud G0.11-0.11 exactly matching the

coordinates of MAGIC excess (M. Tsuboi et al. 1997) — possible origin: 10 - 100 SNE

◮ Possible origin of Arc -radiation from GMC G0.11-0.11 - maybe

interaction of linear filaments and expanding GMC?

◮ Fe K emission either X-ray echo of SgrA* (M. Clavel et al. 2013) flare

• r excited by CRs (F

. Yusef-Zadeh et al. 2013)

◮ Are same CRs also producing the TeV emission?

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Attempting to calculate spectrum of the Arc

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Preliminary Results:

E [GeV]

3

10

4

10

]

• 1

s

• 2

[TeV cm dE dA dt dN

2

E

• 15

10

• 14

10

• 13

10

• 12

10

• 11

10

• 10

10

/ ndf

2

χ 0.3851 / 2 f 1.864e-13 ± 5.669e-13

1

α 0.5824 ±

• 0.9812

cut

E 1.524 ± 3.309 / ndf

2

χ 0.3851 / 2 f 1.864e-13 ± 5.669e-13

1

α 0.5824 ±

• 0.9812

cut

E 1.524 ± 3.309 / ndf

2

χ 2.674 / 2 f 1.961e-13 ± 2.137e-12

1

α 0.1522 ±

• 1.756

cut

E 1.772 ± 7.332 / ndf

2

χ 2.674 / 2 f 1.961e-13 ± 2.137e-12

1

α 0.1522 ±

• 1.756

cut

E 1.772 ± 7.332 / ndf

2

χ 0.3207 / 3 f 2.523e-13 ± 8.799e-13

1

α 0.3099 ±

• 2.748

/ ndf

2

χ 0.3207 / 3 f 2.523e-13 ± 8.799e-13

1

α 0.3099 ±

• 2.748

/ ndf

2

χ 0.3851 / 2 f 1.864e-13 ± 5.669e-13

1

α 0.5824 ±

• 0.9812

cut

E 1.524 ± 3.309 / ndf

2

χ 0.3851 / 2 f 1.864e-13 ± 5.669e-13

1

α 0.5824 ±

• 0.9812

cut

E 1.524 ± 3.309

Source regions: SgrA* 0.1 deg radius 0.25 deg ellipse × Arc 0.075 G0.9 0.14 deg radius SgrA* 0.1 deg using Flute

SEDs from skymap regions

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Preliminary Results:

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Preliminary Results:

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Remarks

◮ Flux for the central object (GC/SgrA*):

FE>1TeV ≈ 2 · 10−12 cm−2s−1, FE>2TeV ≈ 1 · 10−12 cm−2s−1, FE>5TeV ≈ 2 · 10−13 cm−2s−1

◮ This corresponds to ≈20 evts/h, ≈15 evts/h, ≈7 evts/h in

case of MAGIC taking into account the average effective collection areas

◮ The observations are of course not background free

⇒ We are quite statistics limited, especially at high energies

◮ Also, because of the detection technique the angular

resolution is always worse than 0.05◦

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A MAGIC picture of our Galactic Center The MAGIC GC observation campaign and results Speculations

Conclusions

◮ GC is a very interesting target for astronomical observations –

also in VHE-

◮ We are coming closer and closer to revealing the origin of the

high energy radiation from the GC

◮ Each observation at each wavelength serves as a piece in the

puzzle

Thanks for your attention!

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