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Populations Studies in the Fermi Era D. Gasparrini on behalf of M. Ajello and Fermi Lat collaboration
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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 -2 s -1
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FSRQ BL LAC Unknown 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
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FSRQ Unass. 2FGL Total 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
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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
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LF estimate methodology The luminosity Function is modeled as: WhereIs 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
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Pure Luminosity evolution (PLE) Double Power law Evolution in luminosity as a power-law with index k with a cutoff after the Maximum of the Evolution L -γ 2 L -γ 1 L. Evol.
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PLE results PLE 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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Luminosity-dependent density evolution (LDDE) Evolution of the redshift peak with luminosity L -γ 2 L -γ 1 L. Evol. D. Evol. p1p1 p2p2
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LDDE result LDDE 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
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The representation of the GLF
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Redshift peak evolution
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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 = 10 48 erg s -1
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Contribution of FSRQs to EGB Total (e.g. resolved + unresolved) emission from FSRQs No EBL/cascade considered yet, but unimportant for soft spectra
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The Status of the γ -ray background FSRQ Star-forming Gal. BL Lac Radio Galaxies BL Lac contribution comes from LogN-LogS: a better estimate can be obtained with a study on LF
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BLLAC Luminosity function Main 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
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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)
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Redshift constrains For 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
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How to derive BL Lac LF Monte-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..
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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
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