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X-UDS: The Chandra Legacy Survey of the UKIDSS Ultra Deep Survey Field

Kocevski, Dale D.; Hasinger, Guenther; Brightman, Murray; Nandra, Kirpal; Georgakakis, Antonis; Cappelluti, Nico; Civano, Francesca; Li, Yuxuan; Li, Yanxia; Aird, James; Alexander, David M.; Almaini, Omar; Brusa, Marcella; Buchner, Johannes; Comastri, Andrea; Conselice, Christopher J.; Dickinson, Mark A.; Finoguenov, Alexis; Gilli, Roberto; Koekemoer, Anton M.; Miyaji, Takamitsu; Mullaney, James R.; Papovich, Casey; Rosario, David; Salvato, Mara; Silverman, John D.; Somerville, Rachel S.; Ueda, Yoshihiro

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Dale D. Kocevski

Guenther Hasinger

Murray Brightman

Kirpal Nandra

Antonis Georgakakis

Nico Cappelluti

Francesca Civano

Yuxuan Li

Yanxia Li

James Aird

Omar Almaini

Marcella Brusa

Johannes Buchner

Andrea Comastri

Christopher J. Conselice

Mark A. Dickinson

Alexis Finoguenov

Roberto Gilli

Anton M. Koekemoer

Takamitsu Miyaji

James R. Mullaney

Casey Papovich

David Rosario

Mara Salvato

John D. Silverman

Rachel S. Somerville

Yoshihiro Ueda


We present the X-UDS survey, a set of wide and deep Chandra observations of the Subaru-XMM Deep/UKIDSS Ultra Deep Survey (SXDS/UDS) field. The survey consists of 25 observations that cover a total area of 0.33 deg2. The observations are combined to provide a nominal depth of ~600 ks in the central 100 arcmin2 region of the field that has been imaged with Hubble/WFC3 by the CANDELS survey and ~200 ks in the remainder of the field. In this paper, we outline the survey's scientific goals, describe our observing strategy, and detail our data reduction and point source detection algorithms. Our analysis has resulted in a total of 868 band-merged point sources detected with a false-positive Poisson probability of <1 × 10−4. In addition, we present the results of an X-ray spectral analysis and provide best-fitting neutral hydrogen column densities, N H, as well as a sample of 51 Compton-thick active galactic nucleus candidates. Using this sample, we find the intrinsic Compton-thick fraction to be 30%–35% over a wide range in redshift (z = 0.1–3), suggesting the obscured fraction does not evolve very strongly with epoch. However, if we assume that the Compton-thick fraction is dependent on luminosity, as is seen for Compton-thin sources, then our results are consistent with a rise in the obscured fraction out to z ~ 3. Finally, an examination of the host morphologies of our Compton-thick candidates shows a high fraction of morphological disturbances, in agreement with our previous results. All data products described in this paper are made available via a public website.


Kocevski, D. D., Hasinger, G., Brightman, M., Nandra, K., Georgakakis, A., Cappelluti, N., …Ueda, Y. (2018). X-UDS: The Chandra Legacy Survey of the UKIDSS Ultra Deep Survey Field. Astrophysical Journal Supplement, 236(2), Article 48.

Journal Article Type Article
Acceptance Date Jan 29, 2018
Online Publication Date Jun 14, 2018
Publication Date Jun 14, 2018
Deposit Date Jul 5, 2018
Publicly Available Date Jul 5, 2018
Journal Astrophysical Journal Supplement
Print ISSN 0067-0049
Electronic ISSN 1538-4365
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 236
Issue 2
Article Number 48
Public URL


Published Journal Article (2.1 Mb)

Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.

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