Populations Studies in the Fermi Era

D. Gasparrini on behalf of M. Ajello and Fermi Lat collaboration

2LAC Clean Sample

• 310 FSRQ• 395 BLLAC• 157 Blazar of unknown type (no clear optical

classification

|bII| >10º , single association, no analysis flags

Completeness at 5x 10-12 erg cm-2s-1

FSRQBL LACUnknown Blazar

Not corrected non-uniform sensitivity and detection/association efficiency

Roughly compatible with 1LAC results and the FSRQ flattening at faint end shows that increasing the exposure will yield only a modest addition to the number of such sources.

Counts Distribution in 2LAC

FSRQUnass. 2FGLTotal

Not corrected non-uniform sensitivity and detection/association efficiency

Adding High Latitude unassociated sources with gamma >2.2 (FSRQ like), we observe a steepening of the distribution showing that the unassociated are not only FSRQ

Counts Distribution in 2LAC

LF FRSQ Sample• The sample of 186 FSRQs is based on the 11month

catalog :– Extremely clean, ~5% incompleteness– F100 ≥ 10−8 ph cm−2 s−1– TS >50 (>7 sigma) , |b|>15deg– 0.1< z < 3.0

LF estimate methodology

€

d3N

dLγdzdΓ=d2N

dLγdV×dN

dΓ×dV

dz= Φ(Lγ ,z) ×

dN

dΓ×dV

dz

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dN

dΓ= e

−(Γ − μ )2

2σ 2

The luminosity Function is modeled as:

Where Is the intrinsic distribution of the photon index modeled as Gaussian

The LF is determined fitting an analytical parameterization to the z, L,Γ space using Maximum Likelihood algorithm

Pure Luminosity evolution (PLE)

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Φ(Lγ /e(z = 0)) =A

ln(10)Lγ

LγL*

⎛

⎝ ⎜

⎞

⎠ ⎟

γ1

+LγL*

⎛

⎝ ⎜

⎞

⎠ ⎟

γ2 ⎡

⎣ ⎢ ⎢

⎤

⎦ ⎥ ⎥

−1

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e(z) = (1+ z)kez ξ

€

zc = −1− kξ

Double Power law Evolution in luminosity as a power-law with index k with a cutoff after the Maximum of the Evolution

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Φ(Lγ ,z) = Φ(Lγ /e(z))

L-γ2

L-γ1

L. Evol.

PLE resultsPLE provides a reasonably good fit to the data It implies:• Strong evolution in luminosity of FSRQ (k=5.7)• A cut-off in the evolution after z = ~1.6

2 findings:• PLE does not reproduce the source counts very well• There are hints that the redshift cut-off changes with luminosity

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Φ(Lγ ,z) = Φ(Lγ ) × e(z,Lγ )

€

Φ(Lγ ) =A

ln(10)Lγ

LγL*

⎛

⎝ ⎜

⎞

⎠ ⎟

γ1

+LγL*

⎛

⎝ ⎜

⎞

⎠ ⎟

γ 2 ⎡

⎣ ⎢ ⎢

⎤

⎦ ⎥ ⎥

−1

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e(z,Lγ ) =1+ z

1+ zc (Lγ )

⎛

⎝ ⎜

⎞

⎠ ⎟

p1

+1+ z

1+ zc (Lγ )

⎛

⎝ ⎜

⎞

⎠ ⎟

p2 ⎡

⎣ ⎢ ⎢

⎤

⎦ ⎥ ⎥

−1

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zc (Lγ ) = zc ⋅ (Lγ /1048)α

Luminosity-dependent density evolution (LDDE)

Evolution of the redshift peak with luminosity

L-γ2

L-γ1

L. Evol.D.

Evo

l.

p1

p2

LDDE resultLDDE represents the Fermi data well

• It implies:• Strong evolution of FSRQ: factor 100 more FSRQs at

z=1.5• A cut-off in the evolution that changes with luminosity

The representation of the GLF

Redshift peak evolution

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zc (Lγ ) = zc ⋅ (Lγ /1048)α

Comparison with previous results Local GLF (Z=0) Z=1

(low luminosity end) = 1.68 +/- 0.17

2 (high luminosity end) = 3.15 +/- 0.63

Increase of a factor 150 for a source with L = 1048 erg s-1

Contribution of FSRQs to EGBTotal (e.g. resolved + unresolved) emission from FSRQs

No EBL/cascade considered yet, but unimportant for soft spectra

The Status of the γ-ray backgroundFSRQStar-forming Gal.BL LacRadio Galaxies

BL Lac contribution comes from LogN-LogS: a better estimate can be obtained with a study on LF

BLLAC Luminosity functionMain Problem: 55% of the BL Lacs in the 2LAC lack a redshift

measurement

However, several constraints can be put on BL Lacs redshifts:– Spectroscopic lower limits: metal absorption lines due to

intervening systems along the line of sight – Spectroscopic upper limits: due to lack of Lyman forest in the

spectra – Imaging of the host galaxy – ULs due to the detection at TeV

Limits available thanks to the work M. Shaw and R. Romani

Rue et al. A& A, 538, 26

– Photometric redshift which yields a z<1.3 UL for 90% of the objects and estimate for the rest 10% (from Rue et al. A& A, 538, 26)

Redshift constrainsFor the |b|>15deg, TS>50, 1st yr sample:

– ~75% of the (204) BLLs have a redshift constraint

Constraints can be combined to obtain a pseudo redshift measurement

We aim at having >90% redshift completeness

How to derive BL Lac LFMonte-Carlo simulation to produce N samples of BL Lacs drawning the random

redshift from the PDF of each source

The PDF is convoluted by:

– the constrains available for the source

– the intrinsic PDF of the Fermi detected BL Lacs

This distribution is unknown but there are some starting points:

– Use the 2LAC detected BL Lac distribution

– Use the sample distribution

– Use a flat distribution

– Etc..

Motivations• First LF of BLLs at gamma-rays

– most complete redshift coverage• Important for the IGRB

– if LF is compatible with an ‘unbroken’ power law -> BLLs might be very numerous and might contribute most of the >10GeV IGRB

• Cascade emission– quantify reprocessed component and contribution to the IGRB

• Important for CTA/cosmology– easy to quantify/predict number of sources detectable by CTA– TeV blazar in the Universe might provide heating to the IGM

• Important for the blazar sequence or FSRQ-BLL link– easy to check sequence prediction and a good framework to

understand if a genetic link between the FSRQ-BLL class exists