2007
DOI: 10.1051/0004-6361:20077394
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AGN counts at 15$\mu{\rm m}$

Abstract: Context. The counts of galaxies and AGN in the mid infra-red (MIR) bands are important instruments for studying their cosmological evolution. However, the classic spectral line ratios techniques can become misleading when trying to properly separate AGN from starbursts or even from apparently normal galaxies. Aims. We use X-ray band observations to discriminate AGN activity in previously classified MIR-selected starburst galaxies and to derive updated AGN1 and (Compton thin) AGN2 counts at 15 µm. Methods. XMM … Show more

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Cited by 5 publications
(3 citation statements)
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“…If we extrapolate the 16 µm source counts to fluxes 10 times fainter (down to 3 µJy), assuming faint-end slope α = −1.9, we obtain IGL 16 ∼ 2.9 nW m −2 sr −1 , in good agreement with the MIPS value. Fadda et al (2002) find that AGN contribute ∼ 17% of the 15 µm background (see also La Franca et al 2007). Similarly, Matute et al (2006) place a lower limit of the AGN contribution to the 15 µm IGL of 4-10%, using only optically-selected AGN.…”
Section: Integrated Galaxy Light At 16 Micronsmentioning
confidence: 80%
“…If we extrapolate the 16 µm source counts to fluxes 10 times fainter (down to 3 µJy), assuming faint-end slope α = −1.9, we obtain IGL 16 ∼ 2.9 nW m −2 sr −1 , in good agreement with the MIPS value. Fadda et al (2002) find that AGN contribute ∼ 17% of the 15 µm background (see also La Franca et al 2007). Similarly, Matute et al (2006) place a lower limit of the AGN contribution to the 15 µm IGL of 4-10%, using only optically-selected AGN.…”
Section: Integrated Galaxy Light At 16 Micronsmentioning
confidence: 80%
“…The first very shallow (∼10 −13 cgs; 2-10 keV) X-ray band observations on the ELAIS-S1 area were carried out with BeppoSAX and presented by Alexander et al a We define as "good quality" those spectra with quality flag ≥1.5 (see section 3.5) b La Franca et al (2004Franca et al ( , 2007 (2001). More recently, the central ∼0.6 deg 2 region of ELAIS-S1 has been surveyed in the X-ray band with XMM-Newton (four pointings of about 70 "useful" ks each) with 478 sources detected, 395 in the soft (0.5 − 2 keV) band down to a flux of 5.5 × 10 −16 cgs and 205 in the hard (2 − 10 keV) band down to a flux of 2 × 10 −15 cgs (Puccetti et al 2006).…”
Section: X-ray Band Datamentioning
confidence: 99%
“…It should be noted that our measure of the AGN fraction is based on a direct spectroscopic optical classification, while the estimates from Brand et al (2006) are based on a classification which uses Spitzer colors (selecting sources in which the MIR emission is AGN dominated), and Treister et al (2006) use a selection in the hard-X band and then corrects by the absorbed AGN fraction expected to be missed assuming an N H population distribution. The real fraction of AGN would be even larger if we took into account that a fraction (∼10%) of X-ray (or even MIR) classified AGN do not show in the optical signatures of AGN activity (e.g., the XBONG; see Fiore et al 2000Fiore et al , 2003La Franca et al 2007;Cocchia et al 2007;Caccianiga et al 2008;Gruppioni et al 2008;Feruglio et al 2008 and references therein). These objects usually show large values of both X-ray to optical and MIR to optical flux ratios.…”
Section: Fraction Of Agn As a Function Of The 24 µM Fluxmentioning
confidence: 99%