2017ApJ...835...91L


Query : 2017ApJ...835...91L

2017ApJ...835...91L - Astrophys. J., 835, 91-91 (2017/January-3)

Chandra reveals heavy obscuration and circumnuclear star formation in Seyfert 2 galaxy NGC 4968.

LAMASSA S.M., YAQOOB T., LEVENSON N.A., BOORMAN P., HECKMAN T.M., GANDHI P., RIGBY J.R., URRY C.M. and PTAK A.F.

Abstract (from CDS):

We present the Chandra imaging and spectral analysis of NGC 4968, a nearby (z = 0.00986) Seyfert 2 galaxy. We discover extended (∼1 kpc) X-ray emission in the soft band (0.5-2 keV) that is neither coincident with the narrow line region nor the extended radio emission. Based on spectral modeling, it is linked to on-going star formation (∼2.6-4 M☉ yr–1). The soft emission at circumnuclear scales (inner ∼400 pc) originates from hot gas, with kT ∼ 0.7 keV, while the most extended thermal emission is cooler (kT ∼ 0.3 keV). We refine previous measurements of the extreme Fe Kα equivalent width in this source (EW=2.5–1.0+2.6 keV), which suggests the central engine is completely embedded within Compton-thick levels of obscuration. Using physically motivated models fit to the Chandra spectrum, we derive a Compton-thick column density (NH > 1.25 x 1024 cm–2) and an intrinsic hard (2-10 keV) X-ray luminosity of ∼3-8 x 1042 erg s–1 (depending on the presumed geometry of the obscurer), which is over two orders of magnitude larger than that observed. The large Fe Kα EW suggests a spherical covering geometry, which could be confirmed with X-ray measurements above 10 keV. NGC 4968 is similar to other active galaxies that exhibit extreme Fe Kα EWs (i.e., >2 keV) in that they also contain on-going star formation. This work supports the idea that gas associated with nuclear star formation may increase the covering factor of the enshrouding gas and play a role in obscuring active galactic nuclei.

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): galaxies: active - galaxies: individual: NGC 4968 - galaxies: Seyfert - galaxies: star formation - X-rays: galaxies - X-rays: individual: NGC 4968 - X-rays: individual: NGC 4968

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026
#notes
1 IC 3639 Sy1 12 40 52.8344884344 -36 45 21.057011172   13.01 13.50 11.87 12.7 ~ 262 1
2 NGC 4968 Sy2 13 07 05.976 -23 40 37.34   13.78 14.79 12.46 12.78 ~ 198 2
3 IC 1127 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 3090 4

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