Bibcode
Rodríguez-Eugenio, N.; Pérez-García, A. M.; Alonso-Herrero, A.; Acosta-Pulido, J. A.; Rodríguez-Espinosa, J. M.; Ramos-Almeida, C.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 429, Issue 4, p.3449-3471
Advertised on:
3
2013
Citations
13
Refereed citations
11
Description
We present near-infrared (NIR) spectroscopic observations of 28 X-ray
and mid-infrared selected 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 galaxies
are representative of a larger sample studied in a previous work,
consisting of over a hundred X-ray selected sources with mid-infrared
counterparts, which were classified either as AGN dominated or host
galaxy dominated, 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
≥1.5σ above the continuum for the majority of the galaxies.
Using attenuation-corrected Hα luminosities and observed
Spitzer/MIPS 24 μm fluxes, and after subtracting an AGN component
estimated using an AGN empirical correlation and multifrequency SED
fits, we obtain average star formation rates (SFRs) of 7 ± 7 and
20 ± 50 M&sun; yr-1, respectively (median
SFRs = 7 and 5 M&sun; yr-1). These values are
lower than the SFRs reported in the literature for different samples of
non-active star-forming galaxies of similar stellar masses and redshifts
(M* ˜ 1011 M&sun; and z ˜
1). In spite of the small size of the sample studied here, as well as
the uncertainty affecting the AGN-corrected SFRs, we speculate with 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 AGN activity, as observed in the local Universe.
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