Extragalactic Science with the CTA. A. Zech, LUTH

Transcription

1 Extragalactic Science with the CTA A. Zech, LUTH

2 "extragalactic" KSPs Active Galaxies Transients Galaxy Clusters blazars, radio-galaxies, other AGN EBL, IGMF fundamental physics GRBs galactic transients point sources, diffuse emission dark matter Star Forming Systems Galactic star forming regions starburst galaxies Extragalactic Survey 2

3 GRBs science questions: - origin of GRBs (intrinsic γγ absorption, variability...) - connection with cosmic rays (signatures from hadronic cascades?) - probing the EBL / IGMF at high redshifts - fundamental physics (LIV, axions,...) -> GRB observations will profit from the ~104 x higher effective area at 30 GeV compared to Fermi-LAT. expected number of alerts: - Swift (or SVOM) ~ 5 / yr - Fermi GBM ~ 10 / yr -> total ~ 12 / yr late-time follow-up of LAT bursts ~ 1 / yr 3

4 4

5 Galaxy Clusters science questions: - cosmic-ray acceleration and interactions - dark matter searches - "multi-purpose" fields of view (harbour AGN,...) candidate sources for the KSP: Perseus, Coma,... expected observation times for 5 σ detection (only CR-induced signal!) M. Doro et al (CTA) 5

6 Starburst galaxies science questions: - cosmic ray physics (highest energies? spectral shape / cutoffs?) - probing star formation rate / supernova rate - extended emission? 6

7 Extra-galactic survey science questions: - new TeV sources - unbiased blazar survey (but: statistics not competitive with pointed observations) - interest for fundamental physics / dark matter 1/4 of the sky at ~4-5 mcrab? divergent pointing? 7

8 "Active Galaxies" Key Science Project (I) science case 8

9 AGN & three key questions for CTA What is the nature of the different types of black hole particle accelerators? -> Understanding acceleration & emission processes in different AGN classes. NASA 9

10 AGN & three key questions for CTA What is the nature of the different types of black hole particle accelerators? -> Understanding acceleration & emission processes in different AGN classes. What is the origin and nature of cosmic rays and how do they interact with their environment? -> Nature of γ-ray emitters in AGN? Signatures of ultra-high energy cosmic rays? NASA 10

11 AGN & three key questions for CTA What is the nature of the different types of black hole particle accelerators? -> Understanding acceleration & emission processes in different AGN classes. What is the origin and nature of cosmic rays and how do they interact with their environment? -> Nature of γ-ray emitters in AGN? Signatures of ultra-high energy cosmic rays? How did the Universe evolve? Signatures of physics beyond the standard model? AGN as beacons: -> Cosmology with the imprint of the Extragalactic Background Light, Intergalactic Magnetic Field -> Searches for Lorentz invariance violation (quantum gravity), axions (dark matter)... NASA 11

12 absorption features in blazar spectra? Blazars BlazarsatatVHE VHE Senturk et al, ApJ 764 (2013)

13 absorption features in blazar spectra? Blazars BlazarsatatVHE VHE Senturk et al, ApJ 764 (2013) 119 emission mechanism of UHBLs? Murase et al

14 absorption features in blazar spectra? Blazars BlazarsatatVHE VHE Senturk et al, ApJ 764 (2013) 119 emission mechanism of UHBLs? leptonic emission mechanism? hadronic particle population? Murase et al AZ, M. Cerruti, ICRC

15 unified model of blazars, AGN absorption features in blazar spectra? (and jetted sources in general?) Blazars BlazarsatatVHE VHE Senturk et al, ApJ 764 (2013) 119 Ghisellini, Texas symposium 2010 emission mechanism of UHBLs? leptonic emission mechanism? hadronic particle population? Murase et al AZ, M. Cerruti, ICRC

16 correlated flares from M87 Acciari et al., Science 2009 radio-galaxies radio-galaxies && other otheragn AGN 16

17 correlated flares from M87 Acciari et al., Science 2009 radio-galaxies radio-galaxies && other otheragn AGN Centaurus A in multi-lambda NASA 17

18 correlated flares from M87 Acciari et al., Science 2009 radio-galaxies radio-galaxies && other otheragn AGN Centaurus A in multi-lambda NASA LLAGN candidates in the Virgo cluster (G. Pedaletti, IEEC Barcelona) 18

19 NLSy1 PMN J correlated flares from M87 Acciari et al., Science 2009 Foschini et al., 2011 radio-galaxies radio-galaxies && other otheragn AGN Centaurus A in multi-lambda NASA LLAGN candidates in the Virgo cluster (G. Pedaletti, IEEC Barcelona) 19

20 Precision Precision measurement measurement ofofthe theebl EBL - EBL encodes information of starformation since the early universe -> "gamma-ray cosmology" - CTA allows for first time to measure attenuated and intrinsic parts of spectra -> resolve EBL at z=0 down to 20-30% from UV to far IR -> determine evolution up to z~1 D. Mazin et al

21 Constraining Constraining (or (ordetecting detecting?)?) the theigmf IGMF - profound impact on our understanding of galactic fields and evolution of the Universe pair halos: ~ G - CTA allows for the first time a measurement of the intrinsic and reprocessed components pair echos: ~ G E. Prandini 21

22 "Active Galaxies" Key Science Project (II) observational programme prel imin ar y 22

23 VHE AGN at present 23

24 VHE AGN at present 24

25 a possible observation programme I. fixed target observations - promising non-hbl Fermi sources -> high-resolution spectra for systematic modelling - sample of sources at different redshifts -> precision measurement of the EBL & IGMF studies -> evolution of VHE blazars 25

26 fixed-target observations of VHE & Fermi sources example observation time needed for highresolution spectra: 48 new sources combined FoVs cover 8% of the sky! ~ 750 h per site 26

27 T. Hassan, preliminary expected spectra K. Murase, H. Takami, M. Hayashida, preliminary signatures for UHECRs? 27

28 a possible observation programme I. fixed target observations - promising non-hbl Fermi sources -> high-resolution spectra for systematic modelling - sample of sources at different redshifts -> precision measurement of the EBL & IGMF studies -> evolution of VHE blazars - deep observations of radio-galaxies -> spectra & maybe extended emission? 28

29 radio-galaxies (an example) Centaurus A deep observations of core and lobes M87 - deep exposure - include in monitoring and ToO programs other radio-galaxies, LLAGN... included in galaxy cluster surveys (e.g. NGC 1275 & IC 310 in Perseus) figure from Y. Tanaka 29

30 a possible observation programme I. fixed target observations - promising non-hbl Fermi sources -> high-resolution spectra for systematic modelling - sample of sources at different redshifts -> precision measurement of the EBL & IGMF studies -> evolution of VHE blazars - deep observations of radio-galaxies -> spectra & maybe extended emission? II. VHE bright reference sources (monitoring) -> long-term variability & time-resolved spectra 30

31 a possible observation programme I. fixed target observations - promising non-hbl Fermi sources -> high-resolution spectra for systematic modelling - sample of sources at different redshifts -> precision measurement of the EBL & IGMF studies -> evolution of VHE blazars - deep observations of radio-galaxies -> spectra & maybe extended emission? II. VHE bright reference sources (monitoring) -> long-term variability & time-resolved spectra III. AGN flares (ToOs & "snapshots") -> short-term variability -> needed for EBL / IGMF studies at z > ~0.5 -> only way to access NLSy1s and most FSRQs -> LIV, axions... 31

32 from Sol et al (CTA) (figure by J. Biteau) 32

33 a possible observation programme I. fixed target observations - promising non-hbl Fermi sources -> high-resolution spectra for systematic modelling - sample of sources at different redshifts -> precision measurement of the EBL & IGMF studies -> evolution of VHE blazars - deep observations of radio-galaxies -> spectra & maybe extended emission? II. VHE bright reference sources (monitoring) -> long-term variability & time-resolved spectra III. AGN flares (ToOs & "snapshots") -> short-term variability -> needed for EBL / IGMF studies at z > ~0.5 -> only way to access NLSy1s and most FSRQs -> LIV, axions... + MWL coverage / campaigns! 33

34 Conclusions CTA will offer largely improved time-resolution, as well as high-resolution spectra for AGN. Important step for understanding the physics of sources at the smallest scales and highest energies. Very important impact on studies of the EBL, IGMF and fundamental physics. 34

35 35

36 Extra-galactic survey science questions: - new TeV sources - unbiased blazar survey (but: statistics not competitive with pointed observations) - interest for fundamental physics / dark matter? 1/4 of the sky at ~4-5 mcrab? divergent pointing? preliminary L. Gérard 36

37 sensitivity to EBL "wriggles" D. Mazin et al (CTA) sensitivity to pair halos H. Sol et al (CTA) 37

38 Why go to very high energies? (Hasn't Fermi seen it all...?) Cherenkov telescopes probe the fastest time-scales -> probe particle acceleration & cooling -> constraints on emission regions Study of the high-energy end of the spectrum -> cutoffs, breaks -> signatures of EBL, IGMF, LIV... -> measuring the EBL at far-ir VHE γ-rays can probe photon fields inside blazars -> hints to the nature of different blazar classes -> constraints on accretion luminosity S. Funk, J.A. Hinton for CTA, ApP, 43 (2013)

39 Science Objectives 1. Understanding the nature of the different blazar classes - evolution of blazars with redshift - role of external photon fields - blazar unification - particle acceleration mechanism and emission region in blazars 2. High-precision measurement of the Extragalactic Background Light - unprecedented precision measurement of EBL density - EBL at low frequencies (far IR) - disentangle EBL absorption from intrinsic processes - identify characteristic EBL signatures 3. Constraining the Intergalactic Magnetic Field - two regimes accessible with GeV-TeV observations: > ~ 10^-12 G pair halos < ~ 10^-14 G magnetically driven cascades - possibility of first detection of IGMF + Synergies with fundamental physics (ALP, LIV), UHECR physics 39

40 Narrow Line Seyfert 1s "... it is now possible to study an unexplored range of black hole masses and accretion disc rates..." Foschini et al., 2011 Five NLSy1s have been detected in the first 4 years of Fermi-LAT data. astro-ph/

41 e.g. TeV / radio connection M87 in 2008 multiwavelength campaign H.E.S.S., MAGIC, VERITAS, Chandra, VLBA - VHE variability on day-scale -> emission region of small size, close to central core (HST-1, inner VLBI jet, core, BH environment - simultaneous X-ray flare from nucleus - coincides with rise in radio flux -> TeV emission from inner jet or central core M87 in 2005 HST-1 favoured for TeV emission M87 in VHE flare with increased X-ray flux - no increase in radio emission from core => long-term MWL observations needed to pin down the emission region. Radio observations play a vital role! Acciari et al., Science

42 Emission from extended jets/lobes? Hardcastle & Croston, MNRAS 415 (2011) 133 Centaurus A X-ray jet extension ~ 4 arc minutes -> large enough to be resolved with CTA However, most emission is produced in central regions In an optimistic scenario, extended emission beyond 1 arc minute might be detectable A non-detection would place a very valuable lower limit on the magnetic field strength 42

43 Blank Sky Surveys Apart from targeted observations of Fermi AGN or radio/x-ray selected sources, blank sky surveys might be considered. For blank sky surveys, "wide & shallow" coverage is the fastest option to initially maximise number of sources: full-sky survey: >50 sources for 1000 h (< 1 year) # of detections for a total of 100h of observation: Y.Inoue, T.Totani, AGN Physics in the CTA Era (FoV of 5 deg is assumed for CTA here) With 50h/FoV, all-sky survey would take longer than expected life time of CTA of 30 years. Serendipitous discoveries are to be expected. 43

44 for a more complete picture... SOC: M. Begelman, C. Boisson, G. Ghisellini, H. Krawczynski, M. Punch, H. Sol, M. Totani, M. Urry, R.Wagner, M. Ward, A. Zech Proceedings published in PoS 44

45 TeV γ-ray astronomy: 2013 The goal for CTA: detection of ~1000 VHE sources VHE skymap 2013 (source: TeVCat) (145 VHE sources in Nov. 2013) 45

46 Fermi extrapolations max. 50h observation time per source could be obtained in about 3 years with 1500 hr observation time / year 46