DISENTANGLING AGN AND STAR FORMATION IN SOFT X-RAYS

Journal Article · Sat Oct 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/758/2/82· OSTI ID:22086547

LaMassa, Stephanie M; Heckman, T M ^[1]; Ptak, A ^[2]

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1. Johns Hopkins University, Department of Physics and Astronomy, Baltimore, MD 21218 (United States)
2. NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

We have explored the interplay of star formation and active galactic nucleus (AGN) activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low-resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft emission of 34 Sy2s using power-law and thermal models. For the 11 sources with high signal-to-noise Chandra imaging of the diffuse host galaxy emission, we estimate the luminosity due to star formation by removing the AGN, fitting the residual emission. The AGN and star formation contributions to the soft X-ray luminosity (i.e., L{sub x,AGN} and L{sub x,SF}) for the remaining 24 Sy2s were estimated from the power-law and thermal luminosities derived from spectral fitting. These luminosities were scaled based on a template derived from XSINGS analysis of normal star-forming galaxies. To account for errors in the luminosities derived from spectral fitting and the spread in the scaling factor, we estimated L{sub x,AGN} and L{sub x,SF} from Monte Carlo simulations. These simulated luminosities agree with L{sub x,AGN} and L{sub x,SF} derived from Chandra imaging analysis within a 3{sigma} confidence level. Using the infrared [Ne II]12.8 {mu}m and [O IV]26 {mu}m lines as a proxy of star formation and AGN activity, respectively, we independently disentangle the contributions of these two processes to the total soft X-ray emission. This decomposition generally agrees with L{sub x,SF} and L{sub x,AGN} at the 3{sigma} level. In the absence of resolvable nuclear emission, our decomposition method provides a reasonable estimate of emission due to star formation in galaxies hosting type 2 AGNs.

• OSTI ID: 22086547
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 758; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
CHARGE-COUPLED DEVICES
COMPUTERIZED SIMULATION
DECOMPOSITION
EMISSION SPECTRA
GALAXY NUCLEI
GAMMA ASTRONOMY
KEV RANGE
LUMINOSITY
MONTE CARLO METHOD
PHOTON EMISSION
SEYFERT GALAXIES
SOFT X RADIATION
STAR EVOLUTION
STARS
X-RAY GALAXIES