CHANDRA OBSERVATIONS OF THE COLLISIONAL RING GALAXY NGC 922

Journal Article · Sat Mar 10 00:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/747/2/150· OSTI ID:22016215

Prestwich, A H; Galache, J L; Zezas, A ^[1]; Linden, T ^[2]; Kalogera, V ^[3]; Roberts, T P ^[4]; Kilgard, R ^[5]; Wolter, A; Trinchieri, G ^[6]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. University of Santa Cruz, Department of Physics 211 Interdisciplinary Sciences Building, 1156 High Street, Santa Cruz, CA 95064 (United States)
3. Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)
4. Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)
5. Van Vleck Observatory, Wesleyan University, 96 Foss Hill Dr., Middletown, CT 06459 (United States)
6. INAF, Osservatorio Astronomico di Brera, Via Brera 28, IT 20121 Milano (Italy)

In this paper, we report on Chandra observations of the starburst galaxy NGC 922. NGC 922 is a drop-through ring galaxy with an expanding ring of star formation, similar in many respects to the Cartwheel galaxy. The Cartwheel galaxy is famous for hosting 12 ultraluminous X-ray sources (ULXs), most of which are in the star-forming ring. This is the largest number of ULXs seen in a single system and has led to speculation that the low metallicity of the Cartwheel (0.3 Z{sub Sun }) may optimize the conditions for ULX formation. In contrast, NGC 922 has metallicity near solar. The Chandra observations reveal a population of bright X-ray sources, including seven ULXs. The number of ULXs in NGC 922 and the Cartwheel scales with the star formation rate: we do not find any evidence for an excess of sources in the Cartwheel. Simulations of the binary population in these galaxies suggest that the ULX population in both systems is dominated by systems with strong wind accretion from supergiant donors onto direct-collapse black holes. The simulations correctly predict the ratio of the number of sources in NGC 922 and the Cartwheel. Thus, it would appear that the metallicity of the Cartwheel is not low enough to see a difference in the ULX population compared to NGC 922.

• OSTI ID: 22016215
• Journal Information: Astrophysical Journal, Vol. 747, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BLACK HOLES
COMPUTERIZED SIMULATION
STAR EVOLUTION
STARS
STELLAR WINDS
X-RAY GALAXIES