Showing papers by "Brigitte Rocca-Volmerange published in 2008"

Radio-loud AGN in the XMM-LSS field I. Optical identification and sample selection

Abstract: The XMM-Large Scale Structure survey field (XMM-LSS) is an extragalactic window surveyed in the X-ray with the XMM-Newton satellite. It has also been observed in the optical with the Canada-France Hawai Telescope (CFHTLS survey), and in the infrared with the Spitzer Space Telescope (SWIRE survey). These surveys have been carried out to study the structure and evolution of both baryonic and dark matter on cosmological scales. In two previous papers, we presented deep low frequency radio surveys of the XMM-LSS field, with limiting flux density levels of ~4 and ~1.5 mJy/beam at 325 and 610 MHz respectively (5 σ ). These radio surveys were motivated by the need to understand the various connections between the host galaxies of radio sources and their environments. In this paper, we identify optical counterparts to the low frequency radio sources, using the CFHTLS optical catalogue and images, that have an i -band limiting magnitude of $i_{\rm AB}\sim 25$. We use a likelihood ratio method and estimate that ~75% of the radio sources have a detected optical counterpart. Using the CFHTLS and SWIRE data, we derive photometric redshifts for the galaxies that are identified with a radio source, as well as for those that are not; we demonstrate the reliability of these photometric redshifts by deriving the stellar mass function for galaxies at different redshifts, and showing that it is consistent with previous determinations. We classify the radio sources as type-1 AGN, radio galaxies, or star-forming galaxies, and show that the radio luminosity function of the radio galaxies agrees with previous measurements.

Galaxy evolution and faint counts in the near‐infrared

Abstract: The contribution of distant galaxies to the diffuse near‐infrared and submillimetric extragalactic backgrounds can be predicted with the help of a multispectral modelling of the faint galaxy counts. In particular, star‐forming galaxies have to be taken into account as well as old evolved galaxies implying a coherent simulation of the stellar emission from the blue to the near‐infrared with gas and dust contributions. For this reason, an extension of our previous UV and visible models is worked out with a detailed synthesis population model for strong, short timescale starbursts in a dusty medium in the near IR (Lancon and Rocca‐Volmerange, 1995, hereafter LRV95) by using a spectral library of stars from 1.4 to 2.5 μm observed with the FTS instrument at the 3.60m/CFHT and fitted on starburst spectra observed with the instrument. Then an extension of our atlas of synthetic galaxies was carried out, the near‐IR emission (K band) being carefully normalised to the blue (B, V or J+ bands) emission. Galaxy count...