J/MNRAS/477/4749 gamma-rays in Fermi blazars (Costamante+, 2018)
On the origin of gamma-rays in Fermi blazars: beyond the broad-line region.
Costamante L., Cutini S., Tosti G., Antolini E., Tramacere A.
<Mon. Not. R. Astron. Soc., 477, 4749-4767 (2018)>
=2018MNRAS.477.4749C 2018MNRAS.477.4749C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Gamma rays
Keywords: galaxies: active - galaxies: jets - quasars: general -
gamma-rays: general
Abstract:
The gamma-ray emission in broad-line blazars is generally explained as
inverse Compton (IC) radiation of relativistic electrons in the jet
scattering optical-UV photons from the broad-line region (BLR), the
so-called BLR external Compton (EC) scenario. We test this scenario on
the Fermi gamma-ray spectra of 106 broad-line blazars detected with
the highest significance or largest BLR, by looking for cut-off
signatures at high energies compatible with γ-γ
interactions with BLR photons. We do not find evidence for the
expected BLR absorption. For 2/3 of the sources, we can exclude any
significant absorption (τmax<1), while for the remaining 1/3
the possible absorption is constrained to be 1.5-2 orders of magnitude
lower than expected. This result holds also dividing the spectra in
high- and low-flux states, and for powerful blazars with large BLR.
Only 1 object out of 10 seems compatible with substantial attenuation
(τmax>5). We conclude that for 9 out of 10 objects, the jet
does not interact with BLR photons. Gamma-rays seem either produced
outside the BLR most of the time, or the BLR is ∼100 x larger
than given by reverberation mapping. This means that (i) EC on BLR
photons is disfavoured as the main gamma-ray mechanism, versus IC on
IR photons from the torus or synchrotron self-Compton; (ii) the Fermi
gamma-ray spectrum is mostly intrinsic, determined by the interaction
of the particle distribution with the seed-photon spectrum; and (iii)
without suppression by the BLR, broad-line blazars can become copious
emitters above 100GeV, as demonstrated by 3C 454.3. We expect the CTA
sky to be much richer of broad-line blazars than previously thought.
Description:
We selected the 100 objects detected with the highest significance in
the Third Fermi-LAT AGN catalogue (3LAC; Ackermann et al.,
2015ApJ...810...14A 2015ApJ...810...14A, Cat. J/ApJ/810/14), and classified as FSRQ to
guarantee the presence of a BLR. The list of sources is presented in
Table 1, in order of decreasing 3LAC significance.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 80 106 Sample of FSRQ blazars studied in this paper
tablea1.dat 104 106 Spectral parameters of the fits of the
gamma-ray SED data
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See also:
J/ApJ/810/14 : Third catalog of LAT-detected AGNs (3LAC) (Ackermann+, 2015)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- Name Name
19 A1 --- n_Name [b] Note on Name (1)
21- 37 A17 --- 3FGL 3LAC name (3FGL JHHMM.m+DDMM)
39- 45 F7.5 --- z Redshift
47- 52 F6.2 --- sigma Significance of the detection in the 3LAC
(from Ackermann et al., 2015,
Cat. J/ApJ/810/14)
53 A1 --- n_sigma [b] Note on sigma (1)
55- 59 F5.1 10+37W LBLR ?=- Luminosity of the BLR (in 10+44erg/s)
60 A1 --- n_LBLR [a] Note on LBLR (1)
63- 69 E7.2 cm RBLR ?=- Associated radius of the BLR
71- 75 F5.1 --- taumaxBLR ? Maximum optical depth, at the peak of the
γ-γ cross-section,
for a path-length l=RBLR/2
77- 80 A4 --- Refs References for the BLR or emission lines
luminosities (2)
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Note (1): Notes as follows:
a = Our calculation from the line luminosities reported in the respective
reference, following Celotti, Padovani & Ghisellini
(1997MNRAS.286..415C 1997MNRAS.286..415C).
b = This object was left out of the main FSRQ selection despite its LAT
significance, because it was classified as BCU-I in the 3LAC.
Note (2): Referneces as follows:
X14 = Xiong & Zhang (2014MNRAS.441.3375X 2014MNRAS.441.3375X) from data in
Cao & Jiang (1999MNRAS.307..802C 1999MNRAS.307..802C),
Liu, Jiang & Gu (2006ApJ...637..669L 2006ApJ...637..669L),
Chai, Cao & Gu (2012ApJ...759..114C 2012ApJ...759..114C)
GG10 = Ghisellini et al. (2010MNRAS.402..497G 2010MNRAS.402..497G)
GG11 = Ghisellini et al. (2011MNRAS.411..901G 2011MNRAS.411..901G)
GG15 = Ghisellini & Tavecchio (2015MNRAS.448.1060G 2015MNRAS.448.1060G, Cat. J/MNRAS/448/1060)
I15 = Isler et al. (2015ApJ...804....7I 2015ApJ...804....7I, Cat. J/ApJ/804/7)
P14 = Pacciani et al. (2014ApJ...790...45P 2014ApJ...790...45P)
S12 = Shaw et al. (2012ApJ...748...49S 2012ApJ...748...49S, Cat. J/ApJ/748/49)
Sb14 = Sbarrato, Padovani & Ghisellini (2014MNRAS.445...81S 2014MNRAS.445...81S)
T13 = Tavecchio et al. (2013MNRAS.435L..24T 2013MNRAS.435L..24T)
To12 = Torrealba et al. (2012RMxAA..48....9T 2012RMxAA..48....9T, Cat. J/other/RMxAA/48.9)
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- Name Object name
19- 25 F7.5 --- z Redshift
28- 35 E8.3 1/cm2/s F0.2-10GeV Integral flux over the 0.2-10GeV band
38- 41 F4.2 --- GammaU Photon index of the best-fit model below
13GeV rest-frame (Unabsorbed band)
43- 46 F4.2 --- e_GammaU rms uncertainty on GammaU
48- 51 F4.2 --- betaU Curvature of the best-fit model below
13GeV rest-frame (Unabsorbed band)
53- 56 F4.2 --- e_betaU ? rms uncertainty on betaU
58- 61 F4.2 --- chi2U chi2 of the best-fit model below
13GeV rest-frame (Unabsorbed band)
62 A1 --- --- [/]
63 I1 --- DOFU DOF of the best-fit model below
13GeV rest-frame (Unabsorbed band)
65- 68 F4.2 --- GammaF Photon index of the log-parabolic fit with
BLR absorption (logptau), over the full
LAT band and with all parameters free
70- 73 F4.2 --- e_GammaF rms uncertainty on GammaF
75- 78 F4.2 --- betaF Curvature of the log-parabolic fit with
BLR absorption (logptau), over the full
LAT band and with all parameters free
80- 83 F4.2 --- e_betaF rms uncertainty on betaF
85- 88 F4.2 --- chi2F chi2 of the log-parabolic fit with
BLR absorption (logptau), over the full
LAT band and with all parameters free
89 A1 --- --- [/]
90 I1 --- DOFF DOF of the log-parabolic fit with
BLR absorption (logptau), over the full
LAT band and with all parameters free
92- 95 F4.2 --- chi2(logp) chi2 of the following fits over the
full band: pure log-parabola with no
BLR absorption (logp)
96 A1 --- --- [/]
97 I1 --- DOF(logp) DOF of the following fits over the full
band: pure log-parabola with no BLR
absorption (logp)
99-102 F4.2 --- chi2(exp03) chi2 of the following fits over the full
band: power-law with high-energy cutoff
with beta=1/3 (exp03)
103 A1 --- --- [/]
104 I1 --- DOF(exp03) DOF of the following fits over the full
band: power-law with high-energy cutoff
with beta=1/3 (exp03)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Jun-2021