arXiv subjects

I. Matute

Publications and source records attributed to I. Matute.

42 records · Page 3Linked to original sources

arXiv2003

The Radio/Mid-Infrared Correlation and the Contribution of 15-micron Galaxies to the 1.4-GHz Source Counts

The radio counterparts to the 15-micron sources in the European Large Area ISO Survey southern fields are identified in 1.4-GHz maps down to about 80 microJy. The radio-MIR correlation is investigated and derived for the first time at these flux densities for a sample of this size. Our results show that radio and MIR luminosities correlate almost as well as radio and FIR, at least up to z ~ 0.6. Using the derived relation and its spread together with the observed 15-micron counts, we have estimated the expected contribution of the 15-micron extragalactic populations to the radio source counts and the role of MIR starburst galaxies in the well known 1.4-GHz source excess observed at sub-mJy levels. Our analysis demonstrates that IR emitting starburst galaxies do not contribute significantly to the 1.4-GHz counts for strong sources, but start to become a significant fraction of the radio source population at flux densities < 0.5 - 0.8 mJy. They are expected to be responsible for more than 60% of the observed radio counts at < 0.05 mJy. These results are in agreement with the existing results on optical identifications of faint radio sources.

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arXiv2002

The Evolution of type 1 AGN in the IR (15mu). The view from ELAIS-S1

We present the 15 micron luminosity function of type 1 AGN (QSO + Seyfert 1). Our sample of 21 high-redshift sources is selected from the Preliminary Analysis catalogue in the S1 field of the European Large Area ISO Survey (ELAIS). To study the cosmological evolution of the AGN1 luminosity function, our sample has been combined with a local sample of 41 sources observed by IRAS. We find that the luminosity function of AGN1 at 15 micron is fairly well represented by a double-power-law-function. There is evidence for significant cosmological evolution consistent with a pure luminosity evolution (PLE) model L(z) (1+z)^k, with k=3.0-3.3. The value of k depends on the existence or not of an evolution cut-off at redshift ~2, and on the adopted cosmology. From the luminosity function and its evolution we estimate a contribution of AGN1 to the Cosmic Infrared Background (CIRB) of nuI_nu ~ 6 x 10^{-11}W m^{-2} sr^{-1} at 15 micron. This corresponds to ~2-3% of the total observed CIRB at this wavelength. Under the usual assumptions of unified models for AGN, the expected contribution of the whole AGN population to the CIRB at 15 micron is 10-15%.

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arXiv2001

The evolution of AGNs in the Hard X-Rays and the Infrared

We present the estimate of the evolution of type 1 AGNs in the hard (2-10 keV) X-rays drawn from the HELLAS survey, and in the IR (15um) obtained from the ELAIS survey. We find that the local luminosity function (LF) of AGN1 in the 2-10 keV band is fairly well represented by a double-power-law-function. There is evidence for significant cosmological evolution according to a pure luminosity evolution model Lx(z)~(1+z)^k, with k=2.12 and k=2.19 in a (Omega_m,Omega_lambda)=(1.0,0.0) and in a (Omega_m,Omega_lambda)=(0.3,0.7) cosmology respectively. In a (Omega_m,Omega_lambda)=(1.0,0.0) Universe the data show an excess of faint high redshift type 1 AGN which is well modeled by a luminosity dependent density evolution, similarly to what observed in the soft X-rays. In the IR band, with a (Omega_m,Omega_lambda)=(1.0,0.0) cosmology, the evolution found is similar to what observed in other wavebands, the LF is a double-power-law-function with a bright slope 2.9 and a faint slope 1.1, following a luminosity evolution model L(z)~(1+z)^3.0.

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arXiv2001

The European Large Area ISO Survey VI - Discovery of a new hyperluminous infrared galaxy

We report the discovery of the first hyperluminous infrared galaxy (HyLIG) in the course of the European Large Area ISO Survey (ELAIS). This object has been detected by ISO at 6.7, 15, and 90 microns, and is found to be a broad-line, radio-quiet quasar at a redshift: z = 1.099. From a detailed multi-component model fit of the spectral energy distribution, we derive a total infrared luminosity: L_IR (1-1000 microns) ~ 1.0 x 10E13 h_65^-2 L_sun (q_0 = 0.5), and discuss the possible existence of a starburst contributing to the far-IR output. Observations to date present no evidence for lens magnification. This galaxy is one of the very few HyLIGs with an X-ray detection. On the basis of its soft X-ray properties, we suggest that this broad-line object may be the face-on analogue of narrow-line, Seyfert-like HyLIGs.

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arXiv2001

The European Large Area ISO Survey V: a BeppoSAX hard X-ray survey of the S1 region

We present BeppoSAX observations of the Southern S1 region in the European Large Area ISO Survey (ELAIS). These observations cover an area of ~1.7 sq. deg. and reach an on-axis (~0.7 sq. deg) 2-10 keV (HX) sensitivity of ~10E-13 cgs. This is the first HX analysis of an ISOCAM survey. We detect 9 sources with a signal to noise ratio SNR_HX>3, 4 additional sources with a 1.3 to 10 keV (T) SNR_T>3 and 2 additional sources which appear to be associated with QSOs with SNR_T>2.9. The number densities of the SNR_HX>3 sources are consistent with the ASCA and BeppoSAX logN-logS functions. Six BeppoSAX sources have reliable ISOCAM 15 micron counterparts within ~60 arcsec. All these ISOCAM sources have optical counterparts of R<20 mags. Five of these sources have been previously optically classified giving 4 QSOs and 1 BALQSO at z=2.2. The remaining unclassified source has X-ray and photometric properties consistent with that of a nearby Seyfert galaxy. One further HX source has a 2.6sigma ISOCAM counterpart associated with a galaxy at z=0.325. If this ISOCAM source is real, the HX/MIR properties suggest either an unusual QSO or a cD cluster galaxy. We have constructed MIR and HX spectral energy distributions to compute the expected HX/MIR ratios for these classes of objects up to z=3.2 and assess the HX/MIR survey depth. The BALQSO has an observed X-ray softness ratio and HX/MIR flux ratio similar to QSOs but different to those found for low redshift BALQSOs. This difference can be explained in terms of absorption, and suggests that high redshift BALQSOs should be comparatively easy to detect in the HX band, allowing their true fraction in the high redshift QSO population to be determined (ABRIDGED).

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arXiv2000

The evolution of type 1 AGN at 15um from the ELAIS

We present the first preliminary estimate of the evolution of type 1 AGNs at 15 um. A new sample of sources selected from the ELAIS-S1 survey has been used together with the RMS sample. The ELAIS-S1 survey covers an effective area of 2.2 deg^2 (total: 4 deg^2) down to 1.2 mJy at 15 um. Spectroscopic identifications have been carried out in the range 17.2<R<20.0 at the 3.6m/ESO, NTT/ESO and 2dF/AAT. The luminosity function is steeper at bright luminosities in comparison to the previous estimates of Rush, Malkan & Spinoglio (1993). The evolution is compatible with a Pure Luminosity Evolution model with L(z)=L(0)(1+z)^3.4.

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