Bibcode
Ramos-Almeida, C.; Rodríguez-Espinosa, J. M.; Acosta-Pulido, J. A.; Alonso-Herrero, A.; Pérez-García, A. M.; Rodríguez-Eugenio, N.
Referencia bibliográfica
Highlights of Spanish Astrophysics VII, Proceedings of the X Scientific Meeting of the Spanish Astronomical Society (SEA), held in Valencia, July 9 - 13, 2012, Eds.: J.C. Guirado, L.M. Lara, V. Quilis, and J. Gorgas., pp.343-348
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5
2013
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0
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Descripción
We present near-infrared (NIR) spectroscopic observations of 28 X-ray
and mid-infrared sources at a median redshift of z˜0.8 in the
Extended Groth Strip (EGS). To date this is the largest compilation of
NIR spectra of active galactic nuclei (AGN) at this redshift. The data
were obtained using the multi-object spectroscopic mode of the Long-slit
Intermediate Resolution Infrared Spectrograph (LIRIS) at the 4.2 m
William Herschel Telescope (WHT). These AGN are representative of a
larger sample studied in a previous work, consisting of over a hundred
X-ray selected AGN with mid-infrared counterparts, which were classified
either as AGN-dominated or host galaxy-dominated (i.e. buried AGN)
depending on the shape of their spectral energy distributions (SEDs).
Here we present new NIR spectra of 13 and 15 sources of each class
respectively. We detect the Hα line at ≥ 1.5 σ above the
continuum for the majority of the galaxies. Using attenuation-corrected
Hα luminosities, and after subtracting an AGN component that we
estimate using an AGN empirical correlation, we obtain a median star
formation rate (SFR) of 7±7 {M}_{&sun;} year^{-1}. This SFR is
lower than those reported in the literature for different samples of
non-active star-forming galaxies of similar stellar masses and redshifts
(M_*˜ 10^{11} {M}_&sun; and z˜1). Despite the small size of
the sample, we speculate on the possibility of AGN quenching the star
formation in galaxies at z˜0.8. Alternatively, we might be seeing
a delay between the offset of the star formation and the AGN activity,
as observed in the local Universe.