Mon. Not. R. Astron. Soc., 441, 172-186 (2014/June-2)
SDSS J143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources ?
CACCIANIGA A., ANTON S., BALLO L., DALLACASA D., CECA R.D., FANALI R., FOSCHINI L., HAMILTON T., KRAUS A., MACCACARO T., MACK K.-H., MARCHA M.J., PAULINO-AFONSO A., SANI E. and SEVERGNINI P.
Abstract (from CDS):
We present SDSS J143244.91+301435.3, a new case of a radio-loud narrow-line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4GHz = 2.1x1025 W/Hz) and large radio-loudness parameter (R1.4 = 600±100). The radio source is compact with a linear size below ∼ 1.4 kpc but, in contrast to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (α = 0.93, Sν ∝ ν-α) and does not support a `blazar-like' nature. Both the small mass of the central supermassive black hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2x107 M☉ and 0.27, respectively, with a formal error of ∼ 0.4dex for both quantities) are typical of the NLS1 class. Through modelling the spectral energy distribution of the source, we have found that the galaxy hosting SDSS J143244.91+301435.3 is undergoing quite intense star formation (SFR = 50 M☉/yr), which, however, is expected to contribute only marginally ( ∼ 1 per cent) to the observed radio emission. The radio properties of SDSS J143244.91+301435.3 are remarkably similar to those of compact steep-spectrum (CSS) radio sources, a class of active galactic nuclei (AGN) mostly composed of young radio galaxies. This may suggest a direct link between these two classes of AGN, with CSS sources possibly representing the misaligned version (the so-called `parent population') of RL NLS1 showing blazar characteristics.
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
galaxies: active - galaxies: nuclei - quasars: individual: SDSS J143244.91+301435.3
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