| 1. |
- Chen, C. T.J., et al.
(författare)
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The XMM-SERVS survey : New XMM-Newton point-source catalogue for the XMM-LSS field
- 2018
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 478:2, s. 2132-2163
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Tidskriftsartikel (refereegranskat)abstract
- We present an X-ray point-source catalogue from the XMM-Large Scale Structure (XMMLSS) survey region, one of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields. We target the XMM-LSS region with 1.3 Ms of new XMM-Newton AO-15 observations, transforming the archival X-ray coverage in this region into a 5.3 deg2 contiguous field with uniform X-ray coverage totaling 2.7 Ms of flare-filtered exposure, with a 46 ks median PN exposure time. We provide an X-ray catalogue of 5242 sources detected in the soft (0.5-2 keV), hard (2-10 keV), and/or full (0.5-10 keV) bands with a 1 per cent expected spurious fraction determined from simulations. A total of 2381 new X-ray sources are detected compared to previous source catalogues in the same area. Our survey has flux limits of 1.7 × 10-15, 1.3 × 10-14, and 6.5 × 10-15 erg cm-2 s-1 over 90 per cent of its area in the soft, hard, and full bands, respectively, which is comparable to those of the XMM-COSMOS survey. We identify multiwavelength counterpart candidates for 99.9 per cent of the X-ray sources, of which 93 per cent are considered as reliable based on their matching likelihood ratios. The reliabilities of these high-likelihood-ratio counterparts are further confirmed to be ≈97 per cent reliable based on deep Chandra coverage over ≈5 per cent of the XMM-LSS region. Results of multiwavelength identifications are also included in the source catalogue, along with basic optical-to-infrared photometry and spectroscopic redshifts from publicly available surveys. We compute photometric redshifts for X-ray sources in 4.5 deg2 of our field where forced-aperture multiband photometry is available; > 70 per cent of the X-ray sources in this subfield have either spectroscopic or high-quality photometric redshifts.
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| 2. |
- Luo, B., et al.
(författare)
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The Chandra Deep Field-South Survey : 7 Ms Source Catalogs
- 2017
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Ingår i: Astrophysical Journal, Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 228:1
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Tidskriftsartikel (refereegranskat)abstract
- We present X-ray source catalogs for the ≈7 Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 arcmin2. Utilizing wavdetect for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0 keV, 0.5-2.0 keV, and 2-7 keV. A supplementary source catalog is also provided, including 47 lower-significance sources that have bright (Ks ≤ 23) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous ≈4 Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central ≈1 arcmin2 region of ≈1.9 ×10-17, 6.4 ×10-18, and 2.7 ×10-17 erg cm-2 s-1 in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0 keV flux levels. The highest X-ray source density reaches ≈50,500 deg-2, and 47% ± 4% of these sources are AGNs (≈23,900 deg-2).
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| 3. |
- Vito, F., et al.
(författare)
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High-redshift AGN in the Chandra Deep Fields : The obscured fraction and space density of the sub-L* population
- 2018
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 473:2, s. 2378-2406
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the population of high-redshift (3≤z < 6) active galactic nuclei (AGN) selected in the two deepest X-ray surveys, the 7 Ms Chandra Deep Field-South and 2 Ms Chandra Deep Field-North. Their outstanding sensitivity and spectral characterization of faint sources allow us to focus on the sub-L* regime (logLX ≲ 44), poorly sampled by previous works using shallower data, and the obscured population. Taking fully into account the individual photometric-redshift probability distribution functions, the final sample consists of ≈102 X-ray-selected AGN at 3 ≤ z < 6. The fraction of AGN obscured by column densities logNH > 23 is ~0.6-0.8, once incompleteness effects are taken into account, with no strong dependence on redshift or luminosity. We derived the high-redshift AGN number counts down to F0.5-2 keV = 7 × 10-18 erg cm-2 s-1, extending previous results to fainter fluxes, especially at z > 4. We put the tightest constraints to date on the low-luminosity end of AGN luminosity function at high redshift. The space density, in particular, declines at z > 3 at all luminosities, with only a marginally steeper slope for low-luminosity AGN. By comparing the evolution of the AGN and galaxy densities, we suggest that such a decline at high luminosities is mainly driven by the underlying galaxy population, while at low luminosities there are hints of an intrinsic evolution of the parameters driving nuclear activity. Also, the black hole accretion rate density and star formation rate density, which are usually found to evolve similarly at z ≲ 3, appear to diverge at higher redshifts.
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| 4. |
- Vito, F., et al.
(författare)
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The deepest X-ray view of high-redshift galaxies : Constraints on low-rate black hole accretion
- 2016
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 463:1, s. 348-374
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Tidskriftsartikel (refereegranskat)abstract
- We exploit the 7 Ms Chandra observations in the Chandra Deep Field-South (CDF-S), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at 3.5 ≤ z < 6.5. This aim is achieved by stacking the Chandra data at the positions of optically selected galaxies, reaching effective exposure times of ≥109s.We detect significant (>3.7s) X-ray emission from massive galaxies at z ≈ 4. We also report the detection of massive galaxies at z ≈ 5 at a 99.7 per cent confidence level (2.7σ), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The stacking results place constraints on theBHADassociated with the known high-redshift galaxy samples, as well as on the SFRD at high redshift, assuming a range of prescriptions for X-ray emission due to X- ray binaries.We find that the X-ray emission from our sample is likely dominated by processes related to star formation. Our results show that low-rate mass accretion on to SMBHs in individually X-ray-undetected galaxies is negligible, compared with the BHAD measured for samples of X-ray detected AGN, for cosmic SMBH mass assembly at high redshift. We also place, for the first time, constraints on the faint-end of the AGN X-ray luminosity function (logLX ~ 42) at z > 4, with evidence for fairly flat slopes. The implications of all of these findings are discussed in the context of the evolution of the AGN population at high redshift.
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