THE EXTENDED CHANDRA DEEP FIELD-SOUTH SURVEY: OPTICAL SPECTROSCOPY OF FAINT X-RAY SOURCES WITH THE VLT AND KECK

Abstract

We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the ExtendedChandra Deep Field-South (E-CDF-S) and its central 2 Ms area. New spectroscopic redshifts, up to z = 4, are measured for 283 counterparts to Chandra sources with deep exposures (t ∼ 2-9 hr per pointing) using multi-slit facilities on both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of spectroscopically identified X-ray sources to over 500 in this survey field. Since our new spectroscopic identifications are mainly associated with X-ray sources in the shallower 250 ks coverage, we provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, determined by a likelihood routine, and redshifts (both spectroscopic and photometric), that incorporate published spectroscopic catalogs, thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. We demonstrate the remarkable coverage of the luminosity-redshift plane now accessible from our data while emphasizing the detection of active galactic nuclei (AGNs) that contribute to the faint end of the luminosity function (L 0.5-8 keV ∼ 10 43 -10 44 erg s −1 ) at 1.5 z 3 including those with and without broad emission lines. Our redshift catalog includes 17 type-2 QSOs at 1 z 3.5 that significantly increases such samples (2×). Based on our deepest (9 hr) VLT/VIMOS observation, we identify "elusive" optically faint galaxies (R mag ∼ 25) at z ∼ 2-3 based upon the detection of interstellar absorption lines (e.g., O ii+Si iv, C ii], C iv); we highlight one such case, an absorption-line galaxy at z = 3.208 having no obvious signs of an AGN in its optical spectrum. In addition, we determine accurate distances to eight galaxy groups with extended X-ray emission detected both by Chandra and XMM-Newton. Finally, we measure the physical extent of known large-scale structures (z ∼ 0.7) evident in the CDF-S. While a thick sheet (a radial size of 67.7 Mpc) at z ∼ 0.67 extends over the full field, the z ∼ 0.73 structure is thin (18.8 Mpc) and filamentary as traced by both AGNs and galaxy groups. In the Appendix, we provide spectroscopic redshifts for 49 counterparts to fainter X-ray sources detected only in the 1 and 2 Ms catalogs, and 48 Very Large Array radio sources not detected in X-rays.

THE STELLAR, MOLECULAR GAS, AND DUST CONTENT OF THE HOST GALAXIES OF TWOz∼ 2.8 DUST-OBSCURED QUASARS

“…The best spectroscopic analogues with similar redshifts as these objects are high-redshift radio galaxies (McCarthy 1993) and type-2 quasars detected in X-ray surveys (e.g., Norman et al 2002;Silverman et al 2010). The Lyα lines from the radio galaxies are, however typically much stronger relative to the UV emission lines, consistent with the large halos of ionized gas around these objects being affected by the presence of the radio jets (Reuland et al 2007).…”

The Impact of JWST Broadband Filter Choice on Photometric Redshift Estimation

“…Our first galaxy sample contains 2422 galaxies with secure spectroscopic redshifts (z spec ) from the ESO public compilation in the Chandra Deep Field South (CDFS; Cristiani et al 2000;Croom et al 2001;Bunker et al 2003;Dickinson et al 2004;Stanway et al 2004aStanway et al , 2004bStrolger et al 2004;Szokoly et al 2004;van der Wel et al 2004;Doherty et al 2005;Le Fèvre et al 2005;Mignoli et al 2005;Ravikumar et al 2007;Popesso et al 2009;Balestra et al 2010;Silverman et al 2010;Kurk et al 2013;Vanzella et al 2014) and from Morris et al (2015). In order to obtain multiwavelength photometry for these galaxies, we cross-matched this sample with the public Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS; Grogin et al 2011;Koekemoer et al 2011) catalog for the Great Observatory Origins Deep Survey South field (GOODS-S) obtained by Guo et al (2013).…”

The XMM deep survey in the CDF-S

“…Optical identifications and redshifts are primarily taken from X11 (i.e., spectroscopic redshifts from Treister et al 2009b;Popesso et al 2009;Balestra et al 2010;Silverman et al 2010;Le Fèvre et al 2004;Szokoly et al 2004;Mignoli et al 2005;Ravikumar et al 2007;Vanzella et al 2008; and photometric redshifts from Zheng et al 2004;Luo et al 2010;Cardamone et al 2010;Rafferty et al 2011). To search for more redshifts and updates, we checked spectroscopic redshifts in recent works (Cooper et al 2011;Coppin et al 2012;Kurk et al 2013).…”