Prospects for gamma-ray observations of narrow-line Seyfert 1 galaxies with the Cherenkov Telescope Array II. Gamma-gamma absorption in the broad-line region radiation fields. (arXiv:2002.11737v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Romano_P/0/1/0/all/0/1">P. Romano</a> (1,2), <a href="http://arxiv.org/find/astro-ph/1/au:+Bottcher_M/0/1/0/all/0/1">M. Böttcher</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Foschini_L/0/1/0/all/0/1">L. Foschini</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Boisson_C/0/1/0/all/0/1">C. Boisson</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Vercellone_S/0/1/0/all/0/1">S. Vercellone</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Landoni_M/0/1/0/all/0/1">M. Landoni</a> (1), ((1) INAF/OAB, (2) LUTH/OdP/CNRS/U Paris, (3) CFR North-Western U.)
Gamma-ray emitting narrow-line Seyfert 1 ($gamma$-NLS1) galaxies possibly
harbour relatively low-mass black holes (10$^6$-10$^8$ M$_{odot}$) accreting
close to the Eddington limit, and share many characteristics with their sibling
sources, flat-spectrum radio quasars. Although they have been detected in the
MeV–GeV band with Fermi-LAT, they have never been seen in the very high energy
band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they
are key targets for the next-generation IACT, the Cherenkov Telescope Array
(CTA). In a previous work we selected, by means of extensive simulations, the
best candidates for a prospective CTA detection (SBS 0846$+$513, PMN
J0948$+$0022, and PKS 1502$+$036) taking into account the effects of both the
intrinsic absorption (approximated with a cut-off at 30 GeV), and the
extra-galactic background light on the propagation of $gamma$-rays. In this
work we simulate the spectra of these three sources by adopting more realistic
broad-line region (BLR) absorption models. In particular, we consider the
detailed treatment of $gamma$-$gamma$ absorption in the radiation fields of
the BLR as a function of the location of the $gamma$-ray emission region with
parameters inferred from observational constraints. We find that, due to the
energy range extent and its sensitivity, CTA is particularly well suited to
locate the $gamma$-ray emitting region in $gamma$-NLS1. In particular CTA
will be able not only to distinguish whether the $gamma$-ray emitting region
is located inside or outside the BLR, but also where inside the BLR it may be.
Gamma-ray emitting narrow-line Seyfert 1 ($gamma$-NLS1) galaxies possibly
harbour relatively low-mass black holes (10$^6$-10$^8$ M$_{odot}$) accreting
close to the Eddington limit, and share many characteristics with their sibling
sources, flat-spectrum radio quasars. Although they have been detected in the
MeV–GeV band with Fermi-LAT, they have never been seen in the very high energy
band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they
are key targets for the next-generation IACT, the Cherenkov Telescope Array
(CTA). In a previous work we selected, by means of extensive simulations, the
best candidates for a prospective CTA detection (SBS 0846$+$513, PMN
J0948$+$0022, and PKS 1502$+$036) taking into account the effects of both the
intrinsic absorption (approximated with a cut-off at 30 GeV), and the
extra-galactic background light on the propagation of $gamma$-rays. In this
work we simulate the spectra of these three sources by adopting more realistic
broad-line region (BLR) absorption models. In particular, we consider the
detailed treatment of $gamma$-$gamma$ absorption in the radiation fields of
the BLR as a function of the location of the $gamma$-ray emission region with
parameters inferred from observational constraints. We find that, due to the
energy range extent and its sensitivity, CTA is particularly well suited to
locate the $gamma$-ray emitting region in $gamma$-NLS1. In particular CTA
will be able not only to distinguish whether the $gamma$-ray emitting region
is located inside or outside the BLR, but also where inside the BLR it may be.
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