Is the I N TEG R AL IBIS Source IGR J17204-3554 a Gamma-Ray-emitting Galaxy Hidden behind the Molecular Cloud NGC 6334? | Zendy

L. Bassani | Zendy; Alessandra De Rosa | Zendy; A. Bazzano | Zendy; A. J. Bird | Zendy; Anthony J. Dean | Zendy; N. Gehrels | Zendy; J. A. Kennea | Zendy; A. Malizia | Zendy; M. Molina | Zendy; J. B. Stephen | Zendy; P. Ubertini | Zendy; R. Walter | Zendy

Open Access

Is the I N TEG R AL IBIS Source IGR J17204-3554 a Gamma-Ray-emitting Galaxy Hidden behind the Molecular Cloud NGC 6334?

Author(s) -

L. Bassani,

Alessandra De Rosa,

A. Bazzano,

A. J. Bird,

Anthony J. Dean,

N. Gehrels,

J. A. Kennea,

A. Malizia,

M. Molina,

J. B. Stephen,

P. Ubertini,

R. Walter

Publication year - 2005

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/498718

Subject(s) - physics , astrophysics , milky way , galaxy , flux (metallurgy) , molecular cloud , astronomy , galactic center , ibis , supernova remnant , stars , supernova , materials science , metallurgy , paleontology , biology

We report on the identification of a soft gamma-ray source, IGR J17204-3554,detected with the IBIS imager on board the INTEGRAL satellite. The source has a20-100 keV flux of ~3x10^-11 erg cm^-2 s^-1 and is spatially coincident withNGC 6334, a molecular cloud located in the Sagittarius arm of the Milky Way.Diffuse X-ray emission has been reported from this region by ASCA andinterpreted as coming from five far-infrared cores located in the cloud.However, the combined ASCA spectrum with a 9 keV temperature was difficult toexplain in terms of emission from young pre-main sequence stars known to beembedded in the star forming regions. Detection of gamma-rays makes thisinterpretation even more unrealistic and suggests the presence of a high energysource in or behind the cloud. Follow up observations with Swift and archivalChandra data allow us to disentangle the NGC6334 enigma by locating anextragalactic object with the proper spectral characteristics to explain thegamma-ray emission. The combined Chandra/IBIS spectrum is well fitted by anabsorbed power law with index 1.2+/-0.1, NH=1.4+/-0.1x10^23 cm^-2 and anunabsorbed 2-10 keV flux of 0.5x10^-11 erg cm^-2 s^-1. This column density isin excess of the galactic value implying that we are detecting a backgroundgalaxy concealed by the molecular cloud and further hidden by material locatedeither in the galaxy itself or between IGR J17204-3554 and the cloud.Comment: 4 pages, 4 figures, to be published in Astrophysical Journal Letter

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