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arXiv · 1001.2018

When galaxies collide: understanding the broad absorption-line radio galaxy 4C +72.26

D. J. B. Smith·C. Simpson·A. M. Swinbank·S. Rawlings·M. J. Jarvis
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Abstract

We present a range of new observations of the "broad absorption line radio galaxy" 4C +72.26 (z = 3.5), including sensitive rest-frame ultraviolet integral field spectroscopy using the Gemini/GMOS-N instrument and Subaru/CISCO K-band imaging and spectroscopy. We show that 4C +72.26 is a system of two vigorously star-forming galaxies superimposed along the line of sight separated by ~1300 +/- 200 km/s in velocity, with each demonstrating spectroscopically resolved absorption lines. The most active star-forming galaxy also hosts the accreting supermassive black hole which powers the extended radio source. We conclude that the star formation is unlikely to have been induced by a shock caused by the passage of the radio jet, and instead propose that a collision is a more probable trigger for the star formation. Despite the massive starburst, the UV-mid-infrared spectral energy distribution suggests that the pre-existing stellar population comprises ~10^12 Msolar of stellar mass, with the current burst only contributing a further ~2%, suggesting that 4C +72.26 has already assembled most of its final stellar mass.

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D. J. B. Smith, C. Simpson, A. M. Swinbank, S. Rawlings, M. J. Jarvis. 2010-01-12. When galaxies collide: understanding the broad absorption-line radio galaxy 4C +72.26. https://doi.org/10.1111/j.1365-2966.2010.16279.x

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