The obscured active nucleus of NGC 7172 as seen BY NuSTAR

Heading: 
Extragalactic Astronomy
1Vasylenko, AA
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2018, 34(6):41-56
https://doi.org/10.15407/kfnt2018.06.041
Start Page: Extragalactic Astronomy
Language: Russian
Abstract: 

We analyse the properties of the X-ray emission from Seyfert 2 NGC 7172 which are based on the 32 ks observational data from NuSTAR in 2014. This source showed a constant Compton-thin obscuration NH ≈ 8-1022 cм-2, which is similar to that observed by XMM-Newton, Suzaku, ASCA and BeppoSAX over past 30 years. We revealed the presence of a moderate reflection component with = 0.44 and a narrow Fe Kα line with EW = 67 +13-14 eV. The applied numerical models of torus confirmed the Compton-thin type of the Seyfert nucleus and allowed us to obtain an estimate of the torus opening angle Θi ≈ 59° and inclination Θi ≈ 61°. Using the observation data of previous observation, we demonstrate also the long-term variability of intrinsic luminosity Lintr(2—10 keV) almost by order and EWFeKα by factor ~4 on a timescale of ~12 years, that coincides to the distance of d ≈ 3.7 pc between central source and reprocessing medium. Such changes of intrinsic luminosity without changes in NH value indicate the variability ofa central source. In the same time the spectral analysis results with the presence of the lag between variability of intrinsic luminosity Lintr(2—10 keV) and EWFeKα,as well as a behavior of intensity IFeKα of the line are in agreement with the scenario, where observed FeKα line is generated in a distant gas-dust torus.
Keywords: active galactic nuclei, NGC 7172, X-rays

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References: 

1. Akylas A., Georgantopoulos I., Comastri A. BeppoSAX observations of the Seyfert 2 galaxies NGC 7172 and ESO103-G35. Mon. Notic. Roy. Astron. Soc. 2001. 324. P. 521—528.
https://doi.org/10.1046/j.1365-8711.2001.04375.x

2. Antonucci R. Unified models for active galactic nuclei and quasars. Annu. Rev. Astron. Astrophys. 1993. 31. P. 473—521.
https://doi.org/10.1146/annurev.aa.31.090193.002353

3. Awaki H., Murakami H., Ogawa Y. Variability study of Seyfert 2 galaxi es with XMM-Newton. Astrophys. J.2006. 645. P. 928—939.
https://doi.org/10.1086/504405

4. Blandford R. D., Begelman M. C. On the fate of gas accreting at a low rate on to a black hole. Mon. Notic. Roy. Astron. Soc. 1999. 303. P. 1—5.
https://doi.org/10.1046/j.1365-8711.1999.02358.x

5. Bennet C. L., Halpern M., Hinshaw G., et al. First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: Preliminary maps and basic results. Astrophys. J. Suppl. Ser. 2003. 148. P. 1—27.
https://doi.org/10.1086/377253

6. Brightman M., Nandra K. An XMM-Newton spectral survey of 12 μm selected galaxies - I. X-ray data. Mon. Notic. Roy. Astron. Soc. 2011. 413. P. 1206—1235.
https://doi.org/10.1111/j.1365-2966.2011.18207.x

7. Dadina M., Bassani L., Cappi M., et al. On the origin of the Fe K line in the Seyfert 2 galaxy NGC 7172. Astron. and Astrophys. 2001. 370. P. 70—77.
https://doi.org/10.1051/0004-6361:20010132

8. De Rosa A., Panessa F., Bassani L., et al. Broad-band study of hard X-ray-seiected absorbed active galactic nuclei. Mon. Notic. Roy. Astron. Soc. 2012. 420. P. 2087— 2101.
https://doi.org/10.1111/j.1365-2966.2011.20167.x

9. Fukazawa Y., Hiragi K., Mizuno M., et al. Fe-K line probing of material around the active galactic nucleus central engine with Suzaku. Astrophys. J. 2011. 727. P. 19— 31.
https://doi.org/10.1088/0004-637X/727/1/19

10. George I. M., Fabian A. C. X-ray reflection from cold matter in active galactic nuclei and X-ray binaries. Mon. Notic. Roy. Astron. Soc. 1991. 249. P. 352—367.
https://doi.org/10.1093/mnras/249.2.352

11. Guainazzi M., Bianchi S., de la Calle Perez I., et al. On the driver of relativistic effect strength in Seyfert galaxies. Astron. and Astrophys. 2011. 531. P. 131—144.
https://doi.org/10.1051/0004-6361/201016245

12. Guainazzi M., Matt G., Antonelli L. A., et al. The X-ray spectrum and variability of the Seyfert 2 galaxy NGC 7172. Mon. Notic. Roy. Astron. Soc. 1998. 298. P. 824—830.
https://doi.org/10.1046/j.1365-8711.1998.01702.x

13. Hernández-Garcia L., Masegosa J., González-Martin O., et al. X-ray spectral variability of Seyfert galaxies. Astron. and Astrophys. 2015. 579. P. 90—167.
https://doi.org/10.1051/0004-6361/201526127

14. Iwasawa K., Taniguchi Y. The X-ray Baldwin effect. Astrophys. J. 1993. 413. P. 15—18.
https://doi.org/10.1086/186948

15. Kalberla P. Burton W. B., Hartmann D., et al. The LAB survey of Galactic HI final data reiease of the combined LDS and IAR surveys with improved stray-radiition corrections. Astron. and Astrophys. 2005. 440. P. 775—782.
https://doi.org/10.1051/0004-6361:20041864

16. Kawamuro T., Ueda Y., Tazaki F., et al. Suzaku observations of moderately obscured (Compton-thin) Active Galactic Nuclei selected by Swift/BAT Hard X-ray Survey. Astrophys. J. Suppl. Ser. 2016. 225. P. 14—37.
https://doi.org/10.3847/0067-0049/225/1/14

17. LaMassa S. M., Heckman T. M., Ptak A., et al. Uncovering Obscured Active Galactic Nuclei in Homogeneously Seiected Samples of Seyfert 2 Galaxies. Astrophys. J. 2011. 729. P. 52—80.
https://doi.org/10.1088/0004-637X/729/1/52

18. Lumsden S. L., Heisler C. A., Bailey J. A., et al. Spectropolarimetry of a complete infrared-selected sample of Seyfert 2 galaxies. Mon. Notic. Roy. Astron. Soc. 2001. 327. P. 459—474.
https://doi.org/10.1046/j.1365-8711.2001.04741.x

19. Lusso E., Comastri A., Simmons B. D., et al. Bolometric luminosities and Eddington ratios of X-ray selected active galactic nuclei in the XMM-COSMOS survey. Mon. Notic. Roy. Astron. Soc. 2012. 425. P. 623—640.
https://doi.org/10.1111/j.1365-2966.2012.21513.x

20. Madsen K. K., Harrison F. A., Markwardt C. B., et al. Calibration of the NuSTAR hight-energy focusing x-ray telescope. Astrophys. J. Suppl. Ser. 2015. 220. P. 8—24.
https://doi.org/10.1088/0067-0049/220/1/8

21. Magdziarz P., Zdziarski A. Angle-dependent Compton reflection of X-rays and gamma-rays. Mon. Notic. Roy. Astron. Soc. 1995. 273. P.837—848.
https://doi.org/10.1093/mnras/273.3.837

22. Molina M., Bassani L., Malizia A., et al. Hard x-ray spectra of active galactic nuclei in the INTEGRAL complete sample. Mon. Notic. Roy. Astron. Soc. 2013. 433. P. 1687—1700.
https://doi.org/10.1093/mnras/stt844

23. Murphy K. D., Yaqoob T. An X-ray spectral model for Compton-thick toroidal reprocessors. Mon. Notic. Roy. Astron. Soc. 2009. 397. P. 1549—1562.
https://doi.org/10.1111/j.1365-2966.2009.15025.x

24. Nandra K., Pounds K. A. GINGA observations of the x-ray spectra of Seyfert galaxies. Mon. Notic. Roy. Astron. Soc. 1994. 268. P. 405—429.
https://doi.org/10.1093/mnras/268.2.405

25. Nandra K., O’Neill P. M., George I. M., et al. An XMM-Newton survey of broad iron lines in Seyfert galaxies. Mon. Notic. Roy. Astron. Soc. 2007. 381. P. 194—228.
https://doi.org/10.1111/j.1365-2966.2007.12331.x

26. Narayan R., Yi I. Advection-dominated accretion: A self-similar solution. Astrophys. J. 1994. 428. P. 13—16.
https://doi.org/10.1086/187381

27. Ricci C., Ueda Y., Paltani S., et al. Iron Kα emission in type-I and type-II active galactic nuclei. Mon. Notic. Roy. Astron. Soc. 2014. 441. P. 3622—3633.
https://doi.org/10.1093/mnras/stu735

28. Risaliti G. The BeppoSAX view ofbright Compton-thin Seyfert 2 galaxies. Astron. and Astrophys. 2002. 386. P. 379—398.
https://doi.org/10.1051/0004-6361:20020170

29. Ryde F., Poutanen J., Svensson R., et al. The variable X/gamma-ray spectrum of the Seyfert 2 galaxy NGC 7172. Astron. and Astrophys. 1997. 328. P. 69—77.

30. Sharples R. M., Longmore A. J., Hawarden T. G., et al. NGC 7172 - an obscured active nucleus. Mon. Notic. Roy. Astron. Soc. 1984. 208. P. 15—24.
https://doi.org/10.1093/mnras/208.1.15

31. Smajić S., Fischer S., Zuther J., et al. Unveiling the nucleus of NGC 7172. Astron. and Astrophys. 2012. 544. P. 105—119.
https://doi.org/10.1051/0004-6361/201118256

32. Thean A., Pedlar A., Kukula M. J., et al. High-resolution radio observations of Seyfert galaxi es in the extended 12-μm sample - I. The observations. Mon. Notic. Roy. Astron. Soc. 2000. 314. P. 573—588.
https://doi.org/10.1046/j.1365-8711.2000.03401.x

33. Turner T. J., Pounds K. A. The EXOSAT spectral survey of AGN. Mon. Notic. Roy. Astron. Soc. 1989. 240. P. 833—880.
https://doi.org/10.1093/mnras/240.4.833

34. Turner T. J., George I. M., Nandra K., et al. ASCA observations of type 2 Seyfert galaxies. I. Data analysis results. Astrophys. J. Suppl. Ser. 1997. 113. P.23—67.
https://doi.org/10.1086/313053

35. Urry C. M., Padovani P. Unified schemes for radio-loud active galactic nuclei. Publs Astron. Soc. Pacif. 1995. 107. P. 803—845.
https://doi.org/10.1086/133630

36. Vasylenko A. A., Zhdanov V. I., Fedorova E. V. X-ray spectral parameters for a sample of 95 active galactic nuclei. Astrophys. and Space Sci. 2015. 360. P. 71—87.
https://doi.org/10.1007/s10509-015-2585-z

37. Wilms J., Allen A., McCray R. On the absorption of X-rays in the interstellar medium. Astrophys. J. 2000. 542. P. 914—924.
https://doi.org/10.1086/317016

38. Winter L. M., Mushotzky R. F., Reynolds C.S., et al. X-ray spectral properties of the BAT AGN sample. Astrophys. J. 2009. 690. P. 1322—1349.
https://doi.org/10.1088/0004-637X/690/2/1322

39. Yaqoob T. X-ray transmission in cold matter: nonrelativistic corrections for compton scattering. Astrophys. J. 1997. 479. P. 184—189.
https://doi.org/10.1086/303843

40. Yaqoob T. The nature of the Compton-thick X-ray reprocessor in NGC 4945. Mon. Notic. Roy. Astron. Soc. 2012. 423. P. 3360—3396.
https://doi.org/10.1111/j.1365-2966.2012.21129.x

41. Yaqoob T., Murphy K. D., Miller L., et al. On the efficiency of production of the Fe Kα emission line in neutral matter. Mon. Notic. Roy. Astron. Soc. 2010. 401. P. 411—417.
https://doi.org/10.1111/j.1365-2966.2009.15657.x

42. Yaqoob T., Tatum M.M., Scholtes A., et al. A Compton-thin solution for the Suzaku X-ray spectrum of the Seyfert 2 galaxy Mkn 3. Mon. Notic. Roy. Astron. Soc. 2015. 454. P. 973—990.
https://doi.org/10.1093/mnras/stv2021