Diffuse Gamma-Ray Emission - PDF Free Download

Diffuse Gamma-Ray Emission Debbijoy Bhattacharya Manipal Centre for Natural Sciences (MCNS) Manipal University 5 Sept 2014

Observational Gamma-Ray Astronomy

Atmospheric Window 00 11 00 11 Figure: Atmospheric window Space based observation is required.

Explorer 11 Launched on April 27, 1961 Explorer 11 detected first γ-ray photons from space A brief history... DEBBIJOY BHATTACHARYA Figure: Explorer Recent Trends 11on Astrophysics and Cosmology (Sep. 04-06)

A brief history... 3rd Orbital Solar Observatory (OSO 3) Figure: OSO 3 (Credit: NASA) Launched in March 8, 1967

A brief history... 3rd Orbital Solar Observatory (OSO 3) Figure: OSO 3 (Credit: NASA) Launched in March 8, 1967 detected 621 events during its 16 month operation

A brief history... 3rd Orbital Solar Observatory (OSO 3) Figure: OSO 3 (Credit: NASA) Launched in March 8, 1967 detected 621 events during its 16 month operation first evidence of an isotropic diffuse emission, probably extragalactic origin

A brief history... Second Small Astronomy Satellite (SAS 2) Launched in November 15, 1972 Figure: SAS 2 (Credit: NASA)

A brief history... Second Small Astronomy Satellite (SAS 2) Launched in November 15, 1972 Sensitive above 35 MeV Figure: SAS 2 (Credit: NASA)

A brief history... Second Small Astronomy Satellite (SAS 2) Launched in November 15, 1972 Sensitive above 35 MeV Figure: SAS 2 (Credit: NASA) Two distinct component of diffuse emission:

A brief history... Second Small Astronomy Satellite (SAS 2) Launched in November 15, 1972 Sensitive above 35 MeV Figure: SAS 2 (Credit: NASA) Two distinct component of diffuse emission: component I: Intensity is correlated with lattitude and HI distribution

A brief history... Second Small Astronomy Satellite (SAS 2) component I: Intensity is correlated with lattitude and HI distribution Figure: SAS 2 (Fichtel, Simpson, Thompson, 1978, ApJ, 222, 833)

Second Small Astronomy Satellite (SAS 2) A brief history... component I: Intensity is correlated with lattitude and HI distribution Figure: SAS 2 (Fichtel, Simpson, Thompson, 1978, ApJ, 222, 833)

A brief history... Second Small Astronomy Satellite (SAS 2) I γ = AN HI +B Figure: SAS 2 (Fichtel, Simpson, Thompson, 1978, ApJ, 222, 833)

A brief history... Second Small Astronomy Satellite (SAS 2) I γ = AN HI +B component I: Intensity is correlated with lattitude and HI distribution component II: Isotropic in nature

A brief history... COSB Satellite ESA s first γ-ray satellite.

A brief history... COSB Satellite ESA s first γ-ray satellite. Life time: August 9, 1975; April 25, 1982 Energy range: 2 KeV to 5 GeV Figure: COS B (Credit: ESA)

A brief history... COSB Satellite ESA s first γ-ray satellite. Figure: Extragalactic Source 3C 273

A brief history... COSB Satellite ESA s first γ-ray satellite. Figure: Extragalactic Source 3C 273 detected first extragalactic point source 3C 273

Compton Gamma-Ray Observatory (CGRO) launched on April 5, 1991; deorbited June 4, 2000 A brief history... Figure: CGRO (Credit: NASA)

Compton Gamma-Ray Observatory (CGRO) launched on April 5, 1991; deorbited June 4, 2000 A brief history... Figure: CGRO (Credit: NASA) conducted the first all sky survey in γ-ray utilizing two payloads: COMPTEL and EGRET

Energetic Gamma-ray Experiment Telescope (EGRET) Energy range: 20 MeV to 30 GeV A brief history... Figure: EGRET (Credit: NASA)

Energetic Gamma-ray Experiment Telescope (EGRET) Energy range: 20 MeV to 30 GeV A brief history... Figure: EGRET (Credit: NASA) 20 times larger and more sensetive than previous γ-ray instruments

Energetic Gamma-ray Experiment Telescope (EGRET) detected 273 sources, A brief history...

Energetic Gamma-ray Experiment Telescope (EGRET) detected 273 sources, almost two third sources are unidentified A brief history... Figure: Third EGRET catalog (Hartman et al. 1999)

Energetic Gamma-ray Experiment Telescope (EGRET) detected 273 sources, almost two third sources are unidentified A brief history... Figure: Third EGRET catalog (Hartman et al. 1999) most of the identified sources are a class of active galaxies: Blazars

A brief history... Energetic Gamma-ray Experiment Telescope (EGRET) Gamma-ray Universe 3C 279 Galactic plane Geminga Vela Crab Figure: Gamma-ray All sky Map

Fermi Gamma-ray Space Telescope (Fermi) Launched June 11, 2008 Figure: Fermi telescope (Credit: NASA)

Fermi Gamma-ray Space Telescope (Fermi) Second Fermi catalog: more than 1800 sources (Nolan et al. 2012) Figure: Gamma-ray sky (Credit: NASA)

Diffuse γ-rays Production processes: Neutral pion decay from cosmic-ray nucleons interacting with nucleons in the interstellar gas bremsstrahlung by cosmic-ray electrons, Inverse Compton interaction of cosmic-ray electrons with ambient low energy interstellar photons.

Diffuse γ-rays Neutral pion decay Interaction between nuclei produces pions of all charge Neutral pions decay to gamma-ray: p+p π 0 π 0 2γ

Diffuse γ-rays Neutral pion decay Figure: Primary nucleon spectrum and γ-ray distribution from π 0 decay

Diffuse γ-rays Production processes: / γ ray Bremsstrahlung

Diffuse γ-rays Production processes: / γ ray Bremsstrahlung γ ray Inverse Compton

Diffuse γ-rays Production processes: / γ ray Bremsstrahlung γ ray Inverse Compton Synchrotron

Galactic diffuse emission CR + Matter CR + Radiation Address distribution of matter in the Galaxy Address distribution of star-light Model CR distribution Consistency check with gamma-ray distribution

Space Based γ-ray Telescope OSO-3 (1967): First evidence for an isotropic diffuse emission

Space Based γ-ray Telescope OSO-3 (1967): First evidence for an isotropic diffuse emission SAS-2 (1972): >35 MeV, the diffuse emission is composed of two components (Fichtel et al. 1978): a) one component of galactic origin b) An isotropic component presumed to be extragalactic origin

Space Based γ-ray Telescope OSO-3 (1967): First evidence for an isotropic diffuse emission

Extragalactic γ-ray Background

Extragalactic γ-ray Background = Observed high-latitude emission

Extragalactic γ-ray Background = Observed high-latitude emission {Instrumental

Extragalactic γ-ray Background = Observed high-latitude emission {Instrumental + resolved point sources

Extragalactic γ-ray Background = Observed high-latitude emission {Instrumental + resolved point sources +Galactic diffuse emission}

How to estimate EGRB? Approach I I obs = I EGRB B N H

How to estimate EGRB? I EGRB Approach I I obs = I EGRB + B N H

How to estimate EGRB? I EGRB Approach I I obs = I EGRB + B N H Approach II Directly from pixel by pixel ML fit of FERMI all sky data

Measured EGRB Extragalactic Gamma-Ray Background (EGRB) Figure: EGRB Spectrum (Sreekumar et al. (1998)

Measured EGRB From EGRET Emission > 30 MeV is well represented by a single power law of index 2.1 shows no significant departure from isotropy The integrated flux > 100 MeV is (1.45±0.14) 10 5 photons /cm 2 /sec/sr

Measured EGRB Figure: EGRB Spectrum (Abdo et al. (2010))

Measured EGRB From Fermi: in the energy range of 0.1 100 GeV single power law of index 2.40±0.02 (Abdo et al. 2010, 104, 101101) shows no significant departure from isotropy The integrated flux > 100 MeV is (1.03±0.17) 10 5 photons /cm 2 /sec/sr

Origin of the EGRB Truly Diffuse Processes Large Scale structure formation Black hole evaporation Exotic particle annihilation...

Origin of the EGRB Unresolved point source origin Active galaxies Normal galaxies Starburst galaxies Cluster of galaxies

Diffuse emission due to poor angular resolution

Diffuse emission due to poor angular resolution Figure: Images with increasing poor angular resolutions

Active Galaxy Normal galaxy Figure: M 31 Main source of energy (in optical band) is star light

Active Galaxy Normal galaxy Figure: M 31 Main source of energy (in optical band) is star light Total number of star in our Galaxy: 10 11 ;

Active Galaxy Normal galaxy Figure: M 31 Main source of energy (in optical band) is star light Total number of star in our Galaxy: 10 11 ; Luminosity 10 11 L SUN

Active Galaxy Active Galactic Nuclei (AGN) Figure: M 87 Most of the energy comes from the nucleus (10-1000 times more luminous than the rest of the galaxy)

Active Galaxy Active Galactic Nuclei (AGN) Figure: M 87 Most of the energy comes from the nucleus (10-1000 times more luminous than the rest of the galaxy) So starlight cannot be the source of energy Some other energy production mechanism is needed!

Active Galaxy Active Galactic Nuclei (AGN) Figure: Unification model (Urry & Padovani (1995))

Active Galaxy Radio-loud AGN classification Figure: Unification model (Urry & Padovani (1995)) Blazars

Active Galaxy Radio-loud AGN classification Figure: Unification model (Urry & Padovani (1995)) Blazars :: (FSRQ, BL Lacs) off-axis AGN

How to find contribution from unresolved sources from a source class observables: flux (F), distance (d)

How to find contribution from unresolved sources from a source class observables: flux (F), distance (d) Luminosity (L)

How to find contribution from unresolved sources from a source class observables: flux (F), distance (d) Luminosity (L) L = F 4πd 2

How to find contribution from unresolved sources from a source class observables: flux (F), distance (d) Luminosity (L) L = F 4πd 2 construct source distribution with luminosity and distance Luminosity function (φ(l, z))

How to find contribution from unresolved sources from a source class Source distribution may not be uniform.

How to find contribution from unresolved sources from a source class Source distribution may not be uniform. The density may evolve with distance (density evolution)

How to find contribution from unresolved sources from a source class Source distribution may not be uniform. The density may evolve with distance (density evolution) The luminosity may evolve with distance (luminosity evolution)

How to find contribution from unresolved sources from a source class Catalog Selection Criteria: New source list Average Spectral index NO Shows evolution < V/Vmax> =0.5 Yes No evolution Luminosity Func Pure density evolution Luminosity + density evolution Pure luminosity evolution Evolution Function De evolved Luminosities Expo nential Power law Figure: Luminosity Function Construction (Bhattacharya et al. (2009))

Finally!! Using the final luminosity function. One can estimate the individual source contributions to the diffuse emission (beyond the source catalog limit)

Finally!! Using the final luminosity function. One can estimate the individual source contributions to the diffuse emission (beyond the source catalog limit) Residuals beyond the estimated source contributions point to contributions from truly diffuse processes a result of great interest.

Evolution of estimation of Blazar Contribution Figure: Stecker and his group (1993, 1996)

Evolution of estimation of Blazar Contribution Figure: Stecker and his group (1993, 1996) Figure: Narumoto and Totani (2006, 2007)

Evolution of estimation of Blazar Contribution Blazar Contribution ~ 20 % Figure: Bhattacharya et al. (2009a, 2009c)

Evolution of estimation of Blazar Contribution Blazar Contribution ~ 20 % Figure: Bhattacharya et al. (2009a, 2009c) Limitations

Evolution of estimation of Blazar Contribution Blazar Contribution ~ 20 % Figure: Bhattacharya et al. (2009a, 2009c) Limitations Simple evolution models (pure luminosity and pure density) were used.

Evolution of estimation of Blazar Contribution Blazar Contribution ~ 20 % Figure: Bhattacharya et al. (2009a, 2009c) Limitations Simple evolution models (pure luminosity and pure density) were used. Luminosity function was not well constrained.

Present Status (Using Fermi observation) Utilizing First Fermi catalog Figure: First Fermi Catalog (Abdo et al. 2010, ApJS, 188, 405)

Present Status (Using Fermi observation) Utilizing First Fermi catalog

Present Status (Using Fermi observation) Utilizing First Fermi catalog Bhattacharya et al (2011) was able construct a better constrained luminosity function with simple evolution function.

Present Status (Using Fermi observation) Utilizing First Fermi catalog Bhattacharya et al (2011) was able construct a better constrained luminosity function with simple evolution function. Ajello et al. (2012) considered luminosity dependent density evolution model.

Present Status (Using Fermi observation) Utilizing Second Fermi catalog Figure: First Fermi Catalog (Abdo et al. 2010, ApJS, 188, 405)

Present Status (Using Fermi observation) Utilizing Second Fermi catalog

Present Status (Using Fermi observation) Utilizing Second Fermi catalog Zeng et al. (2013, MNRAS, 431, 997) reconstruct gamma-ray luminosity function of FSRQs considering LDDE evolution model. FSRQ contribution to EGRB is 10%.

BL Lac contribution Due to limited redshift information BL Lac LF was ill constrained until recently. Ajello et al. (2013; arxiv: 1310.0006) constructed the LF of BL Lacs using a complete sample of 211 BL Lacs utilizing 1st year of Fermi data. Few important findings: High luminosity sources evolve faster than low luminosity ones. a subclass of BL Lacs (HSPs) shows negative evolution.

BL Lac contribution Contribution from unresolved BL Lacs 10 15% to the EGRB.

BL Lac contribution Contribution from unresolved BL Lacs 10 15% to the EGRB. Only 50% sources have spectroscopic redshift.

Future work

Future work Derive a more constrained luminosity function of FSRQs with a larger number of sources in the next couple of years.

Future work Derive a more constrained luminosity function of FSRQs with a larger number of sources in the next couple of years. Detailed optical monitoring of BL Lacs for redshift determination.

Future work Derive a more constrained luminosity function of FSRQs with a larger number of sources in the next couple of years. Detailed optical monitoring of BL Lacs for redshift determination. With significant increase of the number of detected off-axis blazars / radio galaxies, constructing their SED and associated modeling a more constrained estimation of their contribution can be achieved than earlier works (e.g., Bhattacharya et al. 2009c, Ajello et al. 2012).

Thanks for your attention