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Stellar Population Synthesis of Bright X-ray Point Sources in NGC 1399

Author Affiliations

  • 1Department of Physics, University of Calicut, Kerala, INDIA

Res. J. Recent Sci., Volume 3, Issue (ISC-2013), Pages 86-88, (2014)


We present the stellar population synthesis (SPS) of X-ray point sources in NGC 1399 with an aim to investigate the dependence of X-ray characteristics on the dynamical properties of the sources. Our sample includes 22 bright X-ray sources (Lx ≥1038 erg/sec) in NGC 1399, of which two are ultra-luminous X-ray sources (ULXs). Using the SPS code of Bruzual and Charlot 2003 (BC03) and magnitudes in four Hubble space telescope (HST) filters, we estimate the possible ages and masses of these sources. We find that their X-ray luminosities are anti-correlated with the derived stellar masses excepting the two ULXs, the Spearman’s rank correlation coefficient being -0.62 with a significance greater than 99%. As the optical counterparts are definitely multiple sources (most likely globular clusters), the strong trend exhibited by X-ray sources suggests the possibility of existence of multiple sources for the production of X-rays as well. Further, SPS also shows that the brighter X-ray sources are in general older. This analysis also suggests that the energy production mechanism in ULXs may be different from other non- ULX sources in our sample, as they are not following the correlation.


  1. Drinkwater M.J., Gregg M.D., Colless M., Substructure and Dynamics of the Fornax Cluster, ApJ., 548), L139-L142 ( 2001)
  2. Richtler T., Dirsch B., Gebhardt K., Geisler D., Hilker M., Alonso M.V., Forte J.C., Grebel E.K., Infante L., Larsen S., Minniti D. and Rejkuba M., The Globular Cluster System of NGC 1399.II. Kinematics of a Large Sample of Globular Clusters, ApJ., 127, 2094-2113(2004)
  3. Blakeslee J.P., Cho H., Peng E.W., Ferrarese L., Jordan A. and Martel A.R., Optical and Infrared Photometry of Globular Clusters in NGC 1399: Evidence for Color -Metallicity Nonlinearity, ApJ., 746(1), 88-103 (2012)
  4. Angelini L., Loewenstein M. and Mushotzky R.F., The X-ray Globular Cluster Population in NGC 1399, ApJ., 557, L35–L38 (2001)
  5. Kundu A., Zepf S.E., Hempel M., Morton D., Ashman K.M., Maccarone T.J., Patig M.K., Puzia T.H. and Vesperini E., The Ages of Globular Clusters in NGC 4365 Revisited with Deep HST Observations, ApJ., 634 (1), L41-L44 (2005)
  6. Bassino L.P., Faifer F.R., Forte J.C., Dirsch B., Richtler T., Geisler D. and Y. Schuberth, Large Scale Study of the NGC 1399 Globular Cluster System in Fornax, A&A, 451(3), 789-796 (2006)
  7. Paolillo M., Puzia T.H., Goudfrooij P., Zepf S.E., Maccarone T.J., Kundu A., Fabbiano G. And Angelini L., Probing the GC-LMXB Connection in NGC 1399 : A Wide Field Study with the Hubble Space Telescope and Chandra, ApJ., 736(2), 90-106 (2011)
  8. Shalima P., Jithesh V., Jeena K., Misra R., Raveendranath S., Dewangan G.C., Ravikumar C.D. and Babu B.R.S., Mid-infrared and X-ray Luminosity Correlations of X-ray Point Sources in NGC 1399, MNRAS, 434(2), 639-651 (2013)
  9. Kim H.S., Yoon S.J., Sohn S.T., Kim S.C., Kim E., Chung C., Lee S.Y. and Lee Y.W., Wide Field Multiband Photometry of Globular Cluster Systems in the Fornax Galaxy Cluster, ApJ., 763(1), 40-61(2013)
  10. Kaaret P., Prestwich A.H., Zezas A., Murray S.S., Kim D.W., Kilgard R.E., Schlegel E.M. and Ward M.J., Chandra High Resolution Camera Observations of the Luminous X-ray source in the starbust galaxy M82, MNRAS, 321, L29-L32 (2000)
  11. Swartz D.A., Ghosh K.K., Tennant A.F., Wu K., The Ultraluminous X-ray Source Population from the Chandra Archive of Galaxies, ApJS., 154, 519-539 (2004)
  12. Devi A.S., Misra R., Agrawal V.K. and Singh K.Y., The dependence of the estimated luminosities of ultra- luminous X-ray sources on spectral modes, ApJ., 664, 458-466 (2007)
  13. Jithesh V., Jeena K., Misra R., Ravindranath S., Dewangan G.C., Ravikumar C.D. and Babu B.R.S., Black hole mass limits for optically dark X-ray bright sources in elliptical galalaxies, ApJ., 729, 67-70 (2011)
  14. Bertin E. and Arnouts S., Sextractor : Software for Source Extraction, A&AS., 117, 393-404 (1996)
  15. Bruzual G. and Charlot S., Stellar population synthesis at the resolution of 2003, MNRAS, 344, 1000-1028 (2003)
  16. Conroy C., Modeling the panchromatic spectral energy distributions of galaxies, Annu. Rev. Astron. Astrophys., 51, 1-66 (2013)
  17. Ostrov P., Geisler D. and Forte J.C., The metallicity gradient and distribution function of globular clusters around NGC 1399, AJ., 105(5), 1762-1778 (1993)
  18. Humphrey P.J. and Buote D.A., Low mass X-ray binaries and globular clusters in early-type galaxies.I. Chandra observations, ApJ., 689, 983-1004 (2008)
  19. Heinke C.O., X-ray Sources in Galactic Globular Cluster, AIP Conf. Proc., 1314, 135-139 (2010)
  20. Zhang Z., Gilfanov M. and Bogdan A., Dependence of the LMXB Population on Stellar Age, A&A, 546, A36-A48 (2012)
  21. Strader J., Chomiuk L., Maccarone T.J. and James C.A., Two stellar mass black holes in the globular cluster M22, Nature, 490, 71-73 (2012)