Max-Planck-Institut für extraterrestrische Physik

X-ray Sources in Normal Galaxies

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X-Ray Astronomy
Research Activities
Compact Objects
Normal Galaxies

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XMM-Newton observations of Local Group galaxies are well suited to study the X-ray source population and diffuse emission in nearby spiral galaxies. The results are important to interpret X-ray data from similar more distant galaxies and allow us to study the differences between younger (e.g. high mass XRBs) and older (low mass XRBs, globular cluster sources) populations.

We have homogeneously analyzed all archival XMM-Newton EPIC observations of the Local Group galaxies M 31 and M 33 and detected 856 and 408 sources, respectively. The sources are identified or classified using X-ray hardness ratio and information from other wavelengths. Within the galaxies we find supersoft sources (SSSs), supernova remnants (SNRs), and X-ray binaries (XRBs). In addition there are foreground stars from the Milky Way and objects in the background (galaxies, cluster of galaxies and active galactic nuclei (AGN)). In total we more than doubled the number of sources in the fields and detected many new SSS, XRBs and SNRs in the galaxies.

Fig 1: XMM-Newton EPIC low background three colour images combining PN and MOS cameras for M 31. Red, green and blue show respectively (0.2-1, 1-2, 2-12) keV bands. The optical extent of the galaxies is indicated by D25 ellipses. The images are smoothed with a Gaussian of 20" FWHM. The insert in the M 31 image shows a factor 3 zoom-in on the centre area (5" smoothing). SSS, thermal SNRs and foreground stars show up in red and yellow, plerionic type SNRs, XRBs and AGN in green , white or blue.

Fig 2: Hardness ratio (HR) diagram of M 33 sources detected by XMM-Newton. Shown as dots are only sources with HR errors smaller than 0.2. Fourground stars and candidates are marked as big and small stars, AGN as crosses, SSSs as triangles, SNRs as hexagons, X-ray binaries as squares. In addition HRs from measured objects in the Galaxy or Magellanic Clouds or determined from model spectra for the source classes are shown by filled symbols. SSSs clearly separate by their HR1. Thermal SNRs and foreground stars cover the same area in the HR2-HR1 diagram and can be separated using optical information. XRBs, plerionic type SNRs and AGN do not separate in the HR diagrams and all show hard HRs.

Ongoing projects:
  • An X-ray monitoring program of the central area of M 31 with Chandra and XMM-Newton
  • - The X-ray Supersoft Source State of Optical Novae in M 31
    - Transient X-ray sources in the central area of M 31
  • The X-ray Source Population of the Andromeda Galaxy M 31
    - An X-ray survey of M 31 using XMM-Newton
  • The Chandra ACIS Survey of M 33 (ChASeM33)
    - A Deep Survey of the Nearest Face-on Spiral Galaxy
Papers from this work:
  • Deep XMM-Newton survey of M 33
    Pietsch, W., Ehle, M., Haberl, F., Misanovic, Z., Trinchieri, G.
    2003, AN, 324, 85
  • The eclipsing massive X-ray binary M 33 X-7: New X-ray observations and optical identification
    Pietsch, W., Mochejska, B.J., Misanovic, Z., Haberl, F., Ehle, M., Trinchieri, G.
    2004, A&A, 413, 879
  • XMM-Newton survey of the Local Group galaxy M 33
    Pietsch, W., Misanovic, Z., Haberl, F., Hatzidimitriou, D., Ehle, M., Trinchieri, G.
    2004, A&A, 426, 11
  • XMM-Newton detection of type I X-ray bursts in M 31
    Pietsch, W., Haberl, F.
    2005, A&A, 430, L45
  • XMM-Newton survey of M 31
    Pietsch, W., Freyberg M., Haberl, F.
    2005, A&A, 434, 483
  • Optical novae: the major class of supersoft X-ray sources in M 31
    Pietsch, W., Fliri, J., Freyberg, M. J., Greiner, J., Haberl, F., Riffeser, A., Sala, G.
    2005, A&A, 442, 879
  • An XMM-Newton survey of the Local Group galaxy M 33 - variability of the detected sources
    Misanovic, Z., Pietsch, W., Haberl, F., Ehle, M., Hatzidimitriou, D., Trinchieri, G.
    2006, A&A, 448, 1247
  • Spectroscopy of the brightest optical counterparts of X-ray sources in the direction of M 31 and M 33
    Hatzidimitriou, D., Pietsch, W., Misanovic, Z., Reig, P., Haberl, F.
    2006, A&A, 451, 835
  • M33 X-7: ChASeM33 Reveals the First Eclipsing Black Hole X-Ray Binary
    Pietsch, W., Haberl, F., Sasaki, M., Gaetz, T. J., Plucinsky, P. P., Ghavamian, P., Long, K. S., Pannuti, T. G.
    2006, ApJ, 646, 420

© X-Ray Group at MPE (group)
last update:09-07-2006, editor of this page:Wolfgang Pietsch, Frank Haberl

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