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First high-energy observations of narrow-line Seyfert 1s with INTEGRAL/IBIS

First high-energy observations of narrow-line Seyfert 1s with INTEGRAL/IBIS
First high-energy observations of narrow-line Seyfert 1s with INTEGRAL/IBIS
Narrow-line Seyfert 1 (NLS1) galaxies are very interesting objects which display peculiar properties when compared to their broad-line analogues (BLS1). Although well studied in many wavebands, their behaviour at >10 keV is poorly studied and yet important to discriminate between models invoked to explain the complexity observed in the X-ray band. Here, we present for the first time high-energy observations (17–100 keV) of five NLS1 galaxies (three bona fide and two candidates) detected by INTEGRAL/Imager on Board INTEGRAL Satellite (IBIS) and provide for all of them a broad-band spectral analysis using data obtained by Swift/XRT below 10 keV. The combined INTEGRAL spectrum is found to be steeper (?= 2.6 ± 0.3) than those of classical Seyfert 1 objects. This is due to a high-energy cut-off, which is required in some individual fits as in the average broad-band spectrum. The location of this high-energy cut-off is at lower energies (E? 60 keV) than typically seen in classical type 1 active galactic nuclei (AGNs); a reflection component may also be present but its value (R < 0.8) is compatible with those seen in standard Seyfert 1s. We do not detect a soft excess in individual objects but only in their cumulative spectrum. Our results suggest a lower plasma temperature for the accreting plasma which combined to the high accretion rates (close to the Eddington rate) points to different nuclear conditions in broad and NLS1 galaxies, likely related to different evolutionary stages.
galaxies: active, galaxies: seyfert, x-rays: galaxies
0035-8711
1360-1366
Malizia, A.
efa63850-cf26-482c-ae3b-54b0c8fb8a87
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32
Landi, R.
b8243478-d7a1-4774-8a66-4158a65a33d3
Masetti, N.
78166fad-2a82-4de5-9359-25706c0a6e2f
De Rosa, A.
b2a68e71-5c23-4649-94f0-1d8ffd40bb77
Panessa, F.
ea57d0af-2ad5-4f65-a8f7-b001e70ebe13
Molina, M.
28a3f3b6-aedf-4fa5-9a4f-dbcba001435d
Dean, A.J.
2f9093f2-855c-4769-b1aa-6dd621b5dcf1
Perri, M.
dc5d82c2-7321-4982-825e-4110b4799766
Tueller, J.
4b3250ab-3761-4f74-acd1-3d5c13a9fb1a
Malizia, A.
efa63850-cf26-482c-ae3b-54b0c8fb8a87
Bassani, L.
07e5602c-f97e-4334-a0fa-c2212431a61a
Bird, A.J.
045ee141-4720-46fd-a412-5aa848a91b32
Landi, R.
b8243478-d7a1-4774-8a66-4158a65a33d3
Masetti, N.
78166fad-2a82-4de5-9359-25706c0a6e2f
De Rosa, A.
b2a68e71-5c23-4649-94f0-1d8ffd40bb77
Panessa, F.
ea57d0af-2ad5-4f65-a8f7-b001e70ebe13
Molina, M.
28a3f3b6-aedf-4fa5-9a4f-dbcba001435d
Dean, A.J.
2f9093f2-855c-4769-b1aa-6dd621b5dcf1
Perri, M.
dc5d82c2-7321-4982-825e-4110b4799766
Tueller, J.
4b3250ab-3761-4f74-acd1-3d5c13a9fb1a

Malizia, A., Bassani, L., Bird, A.J., Landi, R., Masetti, N., De Rosa, A., Panessa, F., Molina, M., Dean, A.J., Perri, M. and Tueller, J. (2008) First high-energy observations of narrow-line Seyfert 1s with INTEGRAL/IBIS. Monthly Notices of the Royal Astronomical Society, 389 (3), 1360-1366. (doi:10.1111/j.1365-2966.2008.13657.x).

Record type: Article

Abstract

Narrow-line Seyfert 1 (NLS1) galaxies are very interesting objects which display peculiar properties when compared to their broad-line analogues (BLS1). Although well studied in many wavebands, their behaviour at >10 keV is poorly studied and yet important to discriminate between models invoked to explain the complexity observed in the X-ray band. Here, we present for the first time high-energy observations (17–100 keV) of five NLS1 galaxies (three bona fide and two candidates) detected by INTEGRAL/Imager on Board INTEGRAL Satellite (IBIS) and provide for all of them a broad-band spectral analysis using data obtained by Swift/XRT below 10 keV. The combined INTEGRAL spectrum is found to be steeper (?= 2.6 ± 0.3) than those of classical Seyfert 1 objects. This is due to a high-energy cut-off, which is required in some individual fits as in the average broad-band spectrum. The location of this high-energy cut-off is at lower energies (E? 60 keV) than typically seen in classical type 1 active galactic nuclei (AGNs); a reflection component may also be present but its value (R < 0.8) is compatible with those seen in standard Seyfert 1s. We do not detect a soft excess in individual objects but only in their cumulative spectrum. Our results suggest a lower plasma temperature for the accreting plasma which combined to the high accretion rates (close to the Eddington rate) points to different nuclear conditions in broad and NLS1 galaxies, likely related to different evolutionary stages.

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More information

Published date: September 2008
Keywords: galaxies: active, galaxies: seyfert, x-rays: galaxies

Identifiers

Local EPrints ID: 144803
URI: http://eprints.soton.ac.uk/id/eprint/144803
ISSN: 0035-8711
PURE UUID: 41533dc1-da55-4cc8-a685-b4969bdbf68b
ORCID for A.J. Bird: ORCID iD orcid.org/0000-0002-6888-8937

Catalogue record

Date deposited: 24 May 2010 13:57
Last modified: 26 Nov 2021 02:36

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Contributors

Author: A. Malizia
Author: L. Bassani
Author: A.J. Bird ORCID iD
Author: R. Landi
Author: N. Masetti
Author: A. De Rosa
Author: F. Panessa
Author: M. Molina
Author: A.J. Dean
Author: M. Perri
Author: J. Tueller

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