A Chandra deep X-ray exposure on the Galactic plane and near infrared identification

K. Ebisawa, A. Paizis, T. J L Couvoisier, P. Dubath, M. Tsujimoto, K. Hamaguchi, V. Beckmann, A. Bamba, A. Senda, M. Ueno, H. Kaneda, Y. Maeda, G. Sato, S. Yamauchi, R. Cutri, E. Nishihara

Research output: Contribution to journalArticle


Using the Chandra ACIS-I instruments, we have carried out a deep X-ray observation on the Galactic plane region at (l, b) ≈ (28.°5, 0.°0), where no discrete X-ray sources have been known previously. We have detected, as well as strong diffuse emission, 274 new point X-ray sources (4 σ confidence) within two partially overlapping fields (∼250 arcmin2 in total) down to the flux limit ∼ 3 × 10-15 erg s -1 cm-2 (2 - 10 keV) and ∼ 7 × 7 × 10 -16 erg s-1 cm-2 (0.5 - 2 keV). We clearly resolved point sources and the Galactic diffuse emission, and found that ∼ 90 % of the flux observed in our field of view originates from diffuse emission. Many point sources are detected either in the soft X-ray band (below 2 keV) or in the hard band (above 2 keV), and only a small number of sources are detected in both energy bands. On the other hand, most soft X-ray sources are considered to be nearby X-ray active stars. We have carried out a follow-up near-infrared (NIR) observation using SOFI at ESO/NTT. Most of the soft X-ray sources were identified, whereas only a small number of hard X-ray sources had counterparts in NIR. Using both X-ray and NIR information, we can efficiently classify the point X-ray sources detected in the Galactic plane. We conclude that most of the hard X-ray sources are background Active Galactic Nuclei seen through the Milky Way, whereas majority of the soft X-ray sources are nearby X-ray active stars.

Original languageEnglish
Pages (from-to)687-690
Number of pages4
JournalUnknown Journal
Issue number552
Publication statusPublished - 2004


  • Chandra
  • Diffuse emission
  • Milky way
  • Near-infrared
  • Survey

ASJC Scopus subject areas

  • Aerospace Engineering

Fingerprint Dive into the research topics of 'A Chandra deep X-ray exposure on the Galactic plane and near infrared identification'. Together they form a unique fingerprint.

  • Cite this

    Ebisawa, K., Paizis, A., Couvoisier, T. J. L., Dubath, P., Tsujimoto, M., Hamaguchi, K., Beckmann, V., Bamba, A., Senda, A., Ueno, M., Kaneda, H., Maeda, Y., Sato, G., Yamauchi, S., Cutri, R., & Nishihara, E. (2004). A Chandra deep X-ray exposure on the Galactic plane and near infrared identification. Unknown Journal, (552), 687-690.