Young stars and non-stellar emission in the aligned radio galaxy 3C 256

Abstract

We present ground-based images of the z=1.824 radio galaxy 3C 256 in the standard BVRIJHK filters and an interference filter centered at 8800A, a Hubble Space Telescope image in a filter dominated by Ly-alpha emission (F336W), and spectra covering rest-frame wavelengths from Ly-alpha to [O III] 5007. Together with published polarimetry observations, we use these to decompose the overall spectral energy distribution into nebular continuum emission, scattered quasar light, and stellar emission. The nebular continuum and scattered light together comprise half (one third) of the V-band (K-band) light within a 4-arcsec aperture, and are responsible for the strong alignment between the optical/near-infrared light and the radio emission. The stellar emission is dominated by a population estimated to be 100-200 Myr old (assuming a Salpeter IMF), and formed in a short burst with a peak star formation rate of 1-4x10^3 Msun/yr. The total stellar mass is estimated to be no more than 2x10^{11} Msun, which is far less than other luminous radio galaxies at similar redshifts, and suggests that 3C 256 will undergo further star formation or mergers.

35 pages including 10 figures; to appear in Nov 10 ApJ

References in corpus (7)

• Triggered Star Formation in a Massive Galaxy at z=3.8: 4C41.17
• HST, radio and infrared observations of 28 3CR radio galaxies at redshift z ~ 1: I. Old stellar populations in central cluster galaxies
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• Young stars and non-stellar emission in the aligned radio galaxy 3C 256
• A complete sample of quasars from the 7C redshift survey

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• Near-Infrared Observations of Powerful High-Redshift Radio Galaxies: 4C 40.36 and 4C 39.37
• Young stars and non-stellar emission in the aligned radio galaxy 3C 256
• Assessing model-based carbon and oxygen abundance derivation from ultraviolet emission lines in AGNs