2010A&A...524A..72L


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.24CET00:27:14

2010A&A...524A..72L - Astronomy and Astrophysics, volume 524, A72-72 (2010/12-1)

Seyfert 2 galaxies in the GeV band: jets and starburst.

LENAIN J.-P., RICCI C., TUERLER M., DORNER D. and WALTER R.

Abstract (from CDS):

The Fermi/LAT collaboration recently reported the detection of starburt galaxies in the high energy γ-ray domain, as well as radio-loud narrow-line Seyfert1 objects. Motivated by the presence of sources close to the location of composite starburst/Seyfert 2 galaxies in the first year Fermi/LAT catalogue, we aim at studying high energy γ-ray emission from such objects, and at disentangling the emission of starburst and Seyfert activity. We analysed 1.6 years of Fermi/LAT data from NGC1068 and NGC4945, which count among the brightest Seyfert 2 galaxies. We search for potential variability of the high energy signal, and derive a spectrum of these sources. We also analyse public INTEGRAL IBIS/ISGRI data over the last seven years to derive their hard X-ray spectrum. We find an excess of high energy γ-rays of 8.3σ and 9.2σ for 1FGLJ0242.7+0007 and 1FGLJ1305.4-4928, which are found to be consistent with the position of the Seyfert 2 galaxies NGC1068 and NGC4945, respectively. The energy spectrum of the sources can be described by a power law with a photon index of Γ=2.31±0.13 and a flux of F100MeV–100GeV=(8.60 ±2.27)x10–12erg/cm2/s for NGC1068, while for NGC4945, we obtain a photon index of Γ=2.31±0.10 and a flux of F100MeV–100GeV=(1.58±0.32)x10–11erg/cm2/s. For both sources, we detect no significant variability nor any indication of a curvature of the spectrum. While the high energy emission of NGC4945 is consistent with starburst activity, that of NGC1068 is an order of magnitude above expectations, suggesting dominant emission from the active nucleus. We show that a leptonic scenario can account for the multi-wavelength spectral energy distribution of NGC1068. High energy γ-ray emission is revealed for the first time in a Seyfert 2 galaxy. If this result is confirmed in other objects, new perspectives would be opened up into the GeV band, with the discovery of a new class of high energy γ-ray emitters.

Abstract Copyright:

Journal keyword(s): gamma rays: galaxies - galaxies: Seyfert - galaxies: individual: NGC1068 - galaxies: individual: NGC4945 - radiation mechanisms: non-thermal

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 2987 2
2 2SLAQ J024157.36+000944.0 BLL 02 41 57.3678081585 +00 09 44.040656085   21.11 20.67     ~ 20 0
3 2XMM J024230.6-000030 QSO 02 42 30.6519133167 -00 00 29.623535634   21.06 20.10     ~ 24 0
4 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 4162 2
5 [GBO96] S1 Rad 02 42 40.772 -00 00 47.73           ~ 53 0
6 2XMM J024250.8-000030 QSO 02 42 50.984 -00 00 31.62   22.07 21.65     ~ 13 0
7 QSO B0240-0012 QSO 02 43 04.6892134092 +00 00 05.462412920   18.73 18.45     ~ 60 0
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15122 1
9 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5410 6
10 NGC 4945 Sy2 13 05 27.279 -49 28 04.44   9.31 14.40 7.55   ~ 1296 2

    Equat.    Gal    SGal    Ecl

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2021.01.24-00:27:14

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