Abstract
Improving the capabilities of detecting faint X-ray sources is
fundamental for increasing the statistics on faint high-z active
galactic nuclei (AGNs) and star-forming galaxies (SFGs). We performed a
simultaneous maximum likelihood point-spread function fit in the
[0.5–2] keV and [2–7] keV energy bands of the 4 Ms Chandra
Deep Field South (CDFS) data at the position of the 34,930 CANDELS
H-band selected galaxies. For each detected source we provide X-ray
photometry and optical counterpart validation. We validated this
technique by means of a ray-tracing simulation. We detected a total of
698 X-ray point sources with a likelihood { L }\gt 4.98 (i.e.,
>2.7σ). We show that prior knowledge of a deep sample of
optical–NIR galaxies leads to a significant increase in the
detection of faint (i.e., ∼10‑17 cgs in the
[0.5–2] keV band) sources with respect to “blind”
X-ray detections. By including previous X-ray catalogs, this work
increases the total number of X-ray sources detected in the 4 Ms CDFS,
CANDELS area to 793, which represents the largest sample of extremely
faint X-ray sources assembled to date. Our results suggest that a large
fraction of the optical counterparts of our X-ray sources determined by
likelihood ratio actually coincides with the priors used for the source
detection. Most of the new detected sources are likely SFGs or faint,
absorbed AGNs. We identified a few sources with putative photometric
redshift z > 4. Despite the low number statistics and the
uncertainties on the photo z, this sample significantly increases the
number of X-ray-selected candidate high-z AGNs.
Original language | English |
---|---|
Pages (from-to) | 95 |
Journal | Astrophysical Journal |
Volume | 823 |
Issue number | 2 |
DOIs | |
Publication status | Published - 25 May 2016 |
Keywords / Materials (for Non-textual outputs)
- galaxies: active
- galaxies: high-redshift
- quasars: supermassive black holes