An X‐Ray–selected Active Galactic Nucleus at<i>z</i> = 4.6 Discovered by the CYDER Survey

Treister, Ezequiel; Castander, F. J.; Maccarone, Thomas J.; Herrera, David; Gawiser, Eric; Maza, J.; Coppi, P.

doi:10.1086/381432

Cited by 5 publications

(5 citation statements)

References 29 publications

(20 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The objects presented in this paper are shown as large filled triangles (X-ray detections) and large downward-pointing arrows (upper limits); RQQs from previous X-ray observations (Kaspi, Brandt, & Schneider 2000;V01;Brandt et al 2002;Bechtold et al 2003;V03a;V03b) are shown as filled circles (X-ray detections) and small downward-pointing arrows (upper limits). AGN detected by X-ray surveys (Schneider et al 1998;Silverman et al 2002;V02;Castander et al 2003;Treister et al 2004) are shown as open squares. The slanted dashed lines show the α ox =−1.5 and α ox =−1.8 loci at z=4.3 (the average redshift of the present sample); the dotted line shows the best-fit correlation reported in §5 for the sample of high-redshift, optically selected RQQs observed by Chandra.…”

Section: Discussionmentioning

confidence: 99%

“…3 and plotted as filled symbols and downward-pointing arrows), only a few AGN at fainter optical magnitudes are detected in the X-rays (open squares). These have all been discovered by moderately deep and deep X-ray surveys with ROSAT (Schneider et al 1998) and Chandra (Silverman et al 2002;V02;Castander et al 2003;Treister et al 2004).…”

Section: X-ray Properties Of the Samplementioning

confidence: 95%

See 1 more Smart Citation

X-Ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminousz≳4 Quasars withChandra

et al. 2005

View full text Add to dashboard Cite

We report on Chandra observations of a sample of 11 optically luminous (M B < −28.5) quasars at z=3. 96-4.55 selected from the Palomar Digital Sky Survey and the Automatic Plate Measuring Facility Survey. These are among the most luminous z ∼ > 4 quasars known and hence represent ideal witnesses of the end of the "dark age ". Nine quasars are detected by Chandra, with ≈ 2-57 counts in the observed 0.5-8 keV band. These detections increase the number of X-ray detected AGN at z ∼ > 4 to ≈ 90; overall, Chandra has detected ≈ 85% of the high-redshift quasars observed with snapshot (few kilosecond) observations. PSS 1506+5220, one of the two X-ray undetected quasars, displays a number of notable features in its rest-frame ultraviolet spectrum, the most prominent being broad, deep Si IV and C IV absorption lines. The average optical-to-X-ray spectral index for the present sample ( α ox =−1.88±0.05) is steeper than that typically found for z ∼ > 4 quasars but consistent with the expected value from the known dependence of this spectral index on quasar luminosity.We present joint X-ray spectral fitting for a sample of 48 radio-quiet quasars in the redshift range 3.99-6.28 for which Chandra observations are available. The X-ray spectrum (≈ 870 counts) is well parameterized by a power law with Γ=1.93 +0.10 −0.09 in the rest-frame ≈ 2-40 keV band, and a tight upper limit of N H ≈ 5×10 21 cm −2 is obtained on any average intrinsic X-ray absorption. There is no indication of any significant evolution in the X-ray properties of quasars between redshifts zero and six, suggesting that the physical processes of accretion onto massive black holes have not changed over the bulk of cosmic time.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: X-ray Properties Of the Samplementioning

confidence: 95%

X-Ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminousz≳4 Quasars withChandra

et al. 2005

View full text Add to dashboard Cite

show abstract

“…Initial results from the first two fields studied were presented by Castander et al (2003b). In addition, two highredshift (z > 4) X-ray-selected quasars discovered in this survey, a significant fraction of the total sample known today ($10), were reported by Castander et al (2003a) and Treister et al (2004a). Near-infrared images in the J and K bands were obtained for these fields up to J $ 21 mag and K $ 20 mag (Vega).…”

mentioning

confidence: 87%

The Calan‐Yale Deep Extragalactic Research (CYDER) Survey: Optical Properties and Deep Spectroscopy of Serendipitous X‐Ray Sources

Treister

Castander

Maccarone

et al. 2005

ApJ

Self Cite

View full text Add to dashboard Cite

We present the first results from the Calán-Yale Deep Extragalactic Research (CYDER) survey. The main goal of this survey is to study serendipitous X-ray sources detected by Chandra in an intermediate flux range (10 À15 to 10 À12 ergs s À1 ) that comprises most of the X-ray background. A total of 267 X-ray sources spread over five archived fields were detected. The log N log S distribution obtained for this sample is consistent with the results of other surveys. Deep V and I images were taken of these fields in order to calculate X-ray-to-optical flux ratios. Identifications and redshifts were obtained for 106 sources using optical spectroscopy from 8 m class telescopes to reach the optically faintest sources, to the same level as deeper X-ray fields like the Chandra Deep Fields, showing that the nature of sources detected depends mostly on the optical limit for spectroscopy. In general, sources optically classified as obscured active galactic nuclei (AGNs) have redder optical colors than unobscured AGNs. A rough correlation between f X =f opt and hard X-ray luminosity was found for obscured AGNs, confirming the prediction by existing models that in obscured AGNs the optical light is completely dominated by the host galaxy. The previously claimed decrease of the obscured-to-unobscured AGN ratio with increasing X-ray luminosity is observed. However, this correlation can be explained as a selection effect caused by the lower optical flux of obscured AGNs. Comparison between the observed N H distribution and predictions by existing models shows that the sample appears complete up to N H < 3 ; 10 22 cm À2 , while for more obscured sources incompleteness plays an important role in the observed obscured-to-unobscured AGN ratio.

show abstract

“…The ChaMP (Kim et al 2004a;Green et al 2004) is carrying out an extragalactic X-ray survey encompassing 10 deg 2 using serendipitous detections in archival Chandra fields. Chandra ′ s small point spread function (∼ 1 ′′ resolution on-axis) and low background allow sources to be detected to fainter flux levels (∼ 10 −15 erg cm −2 s −1 ) than any X-ray observatory past or present, thus enabling the detection of high redshift (z ∼ 5) AGN (Treister et al 2004;Barger et al 2003;Castander et al 2003;Silverman et al 2002). For the present study, we use the full Chandra energy range (0.3-8.0 keV) to detect the absorbed sources missed by previous optical, UV or soft X-ray surveys and take advantage of the high collecting area at soft energies to detect the faint, high redshift AGN.…”

Section: Chandra Multiwavelength Projectmentioning

confidence: 99%

Comoving Space Density of X‐Ray–selected Active Galactic Nuclei

Silverman

Green

Barkhouse

et al. 2005

ApJ

View full text Add to dashboard Cite

For measurement of the active galactic nucleus (AGN ) luminosity function and its evolution, X-ray selection samples all types of AGNs and provides reduced obscuration bias in comparison with UV excess or optical surveys. The apparent decline in optically selected quasars above z $ 3 may be strongly affected by such a bias. The Chandra Multiwavelength Project (CHAMP) is characterizing serendipitously detected X-ray sources in a large number of fields with archival Chandra imaging. We present a preliminary measure of the comoving space density using a sample of 311 AGNs found in 23 CHAMP fields ($1.8 deg 2 ) supplemented with 57 X-ray-bright AGNs from the Chandra Deep Field-North and Chandra Deep Field-South. Within our X-ray flux ( f 0:3-8:0 keV > 4 ; 10 À15 ergs cm À2 s À1 ) and optical magnitude (r 0 < 22:5) limits, our sample includes 14 broad emission-line AGNs at z > 3. Using this X-rayselected sample, we detect a turnover in the comoving space density of luminous type 1 AGNs (log L X > 44:5 ergs s À1 , measured in the 0.3-8.0 keV band and corrected for Galactic absorption) at z > 2:5. Our X-ray sample is the first to show a behavior similar to the well-established evolution of the optical quasar luminosity function. A larger sample of high-redshift AGNs and with a greater fraction of identified sources, either spectroscopic or photometric, at faint optical magnitudes (r 0 > 22:5) are required to remove the remaining uncertainty in our measure of the X-ray luminosity function, particularly given the possibility that AGNs might be more easily obscured optically at high redshift. We confirm that for z < 1, lower luminosity AGNs (log L X < 44:5) are more prevalent by more than an order of magnitude than those with high luminosity. We have combined the Chandra sample with AGNs from the ROSAT surveys to present a measure of the space density of luminous type 1 AGNs in the soft X-ray band (0.5-2.0 keV) that confirms the broadband turnover described above.

show abstract

An X‐Ray–selected Active Galactic Nucleus atz = 4.6 Discovered by the CYDER Survey

Cited by 5 publications

References 29 publications

X-Ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminousz≳4 Quasars withChandra

X-Ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminousz≳4 Quasars withChandra

The Calan‐Yale Deep Extragalactic Research (CYDER) Survey: Optical Properties and Deep Spectroscopy of Serendipitous X‐Ray Sources

Comoving Space Density of X‐Ray–selected Active Galactic Nuclei

Contact Info

Product

Resources

About