arXiv subjects

E. Gonzalez-Solares

Publications and source records attributed to E. Gonzalez-Solares.

40 records · Page 3Linked to original sources

arXiv2003

The ELAIS Deep X-ray Survey I: Chandra Source Catalogue and First Results

We present an analysis of two deep (75 ks) Chandra observations of the European Large Area ISO Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well studied regions with extensive multi-wavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to 2 soft extended sources, which are found to be associated with galaxy clusters. An over-density of sources is found in N1 with 30% more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources.

astro-ph↗

arXiv2002

Obscured AGN from the ELAIS Deep X-ray Survey

The sources discovered in deep hard X-ray surveys with 2-8 keV fluxes of 10^-14 erg cm^-2 s^-1 make up the bulk of the X-ray background at these energies. We present here detailed multi-wavelength observations of three such sources from the ELAIS Deep X-ray Survey. The observations include sensitive near-infrared spectroscopy with the Subaru Telescope and X-ray spectral information from the Chandra X-ray Observatory. The sources observed all have optical-to-near-IR colours redder than an unobscured quasar and comprise a reddened quasar, a radio galaxy and an optically-obscured AGN. The reddened quasar is at a redshift z=2.61 and shows a very large X-ray absorbing column of N_H approx 3.10^23 cm^-2. This contrasts with the relatively small amount of dust reddening, implying a gas-to-dust ratio along the line-of-sight a hundred times greater than that of the Milky Way. The radio galaxy at z=1.57 shows only narrow emission lines, but has a surprisingly soft X-ray spectrum. The softness of this spectrum either indicates an unusually low gas-to-dust ratio for the absorbing medium or X-ray emission related to the young radio source. The host galaxy is extremely red (R-K=6.4) and its optical/near-IR spectrum is best fit by a strongly reddened (A_V~2) starburst. The third X-ray source discussed is also extremely red (R-K=6.1) and lies in a close grouping of three other R-K>6 galaxies. No emission or absorption lines were detected from this object, but its redshift (and that of one of the nearby galaxies) are constrained by SED-fitting to be just greater than z=1. The extremely red colours of these two galaxies can be accounted for by old stellar populations. These observations illustrate the diverse properties of hard X-ray selected AGN.

astro-ph↗

arXiv2002

The coincidence and angular clustering of Chandra and SCUBA sources

We explore the relationship between the hard X-ray and sub-mm populations using deep Chandra observations of a large, contiguous SCUBA survey. In agreement with other recent findings, we confirm that the direct overlap is small. Of the 17 sub-mm sources detected in this field at 850 microns, only one is coincident with a Chandra source. The resulting limits imply that the majority of SCUBA sources are not powered by AGN, unless the central engine is obscured by Compton-thick material with a low (<1 per cent) scattered component. Furthermore, since Chandra detects only ~5 per cent of SCUBA sources, the typical obscuration would need to be almost isotropic. The X-ray upper limits are so strong that in most cases we can also rule out a starburst SED at low redshift, suggesting that the majority of SCUBA sources lie at z>1 even if they are purely starburst galaxies. Despite the low detection rate, we find evidence for strong angular clustering between the X-ray and sub-mm populations. The implication is that AGN and SCUBA sources trace the same large-scale structure but do not generally coincide. If bright sub-mm sources represent massive elliptical galaxies in formation, we suggest that (for a given galaxy) the major episode of star-formation must be distinct from the period of observable quasar activity.

astro-ph↗

arXiv2001

The ELAIS Deep X-ray Survey

We present initial follow-up results of the ELAIS Deep X-ray Survey which is being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray sources are detected in our two 75 ks ACIS-I observations in the well-studied ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to R=26 with a median magnitude of R=24. We show that objects which are unresolved optically (i.e. quasars) follow a correlation between their optical and X-ray fluxes, whereas galaxies do not. We also find that the quasars with fainter optical counterparts have harder X-ray spectra, consistent with absorption at both wavebands. Initial spectroscopic follow-up has revealed a large fraction of high-luminosity Type 2 quasars. The prospects for studying the evolution of the host galaxies of X-ray selected Type 2 AGN are considered.

astro-ph↗