2013A&A...556A..29M

Query : 2013A&A...556A..29M

2013A&A...556A..29M - Astronomy and Astrophysics, volume 556A, 29-29 (2013/8-1)

Obscured AGN at z∼1 from the zCOSMOS-bright survey. I. Selection and optical properties of a [NeV]-selected sample.

MIGNOLI M., VIGNALI C., GILLI R., COMASTRI A., ZAMORANI G., BOLZONELLA M., BONGIORNO A., LAMAREILLE F., NAIR P., POZZETTI L., LILLY S.J., CAROLLO C.M., CONTINI T., KNEIB J.-P., LE FEVRE O., MAINIERI V., RENZINI A., SCODEGGIO M., BARDELLI S., CAPUTI K., CUCCIATI O., DE LA TORRE S., DE RAVEL L., FRANZETTI P., GARILLI B., IOVINO A., KAMPCZYK P., KNOBEL C., KOVAC K., LE BORGNE J.-F., LE BRUN V., MAIER C., PELLO R., PENG Y., PEREZ MONTERO E., PRESOTTO V., SILVERMAN J.D., TANAKA M., TASCA L., TRESSE L., VERGANI D., ZUCCA E., BORDOLOI R., CAPPI A., CIMATTI A., KOEKEMOER A.M., McCRACKEN H.J., MORESCO M. and WELIKALA N.

Abstract (from CDS):

The application of multi-wavelength selection techniques is essential for obtaining a complete and unbiased census of active galactic nuclei (AGN). We present here a method for selecting z∼1 obscured AGN from optical spectroscopic surveys. A sample of 94 narrow-line AGN with 0.65<z<1.20 was selected from the 20k-Bright zCOSMOS galaxy sample by detection of the high-ionization [NeV] λ3426 line. The presence of this emission line in a galaxy spectrum is indicative of nuclear activity, although the selection is biased toward low absorbing column densities on narrow-line region or galactic scales. A similar sample of unobscured (type 1 AGN) was collected applying the same analysis to zCOSMOS broad-line objects. This paper presents and compares the optical spectral properties of the two AGN samples. Taking advantage of the large amount of data available in the COSMOS field, the properties of the [NeV]-selected type 2 AGN were investigated, focusing on their host galaxies, X-ray emission, and optical line-flux ratios. Finally, a previously developed diagnostic, based on the X-ray-to-[NeV] luminosity ratio, was exploited to search for the more heavily obscured AGN. We found that [NeV]-selected narrow-line AGN have Seyfert 2-like optical spectra, although their emission line ratios are diluted by a star-forming component. The ACS morphologies and stellar component in the optical spectra indicate a preference for our type 2 AGN to be hosted in early-type spirals with stellar masses greater than 109.5–10M☉, on average higher than those of the galaxy parent sample. The fraction of galaxies hosting [NeV]-selected obscured AGN increases with the stellar mass, reaching a maximum of about 3% at ≃2x1011M☉. A comparison with other selection techniques at z∼1, namely the line-ratio diagnostics and X-ray detections, shows that the detection of the [NeV] λ3426 line is an effective method for selecting AGN in the optical band, in particular the most heavily obscured ones, but cannot provide a complete census of type 2 AGN by itself. Finally, the high fraction of [NeV]-selected type 2 AGN not detected in medium-deep (≃100-200ks) Chandra observations (67%) is suggestive of the inclusion of Compton-thick (i.e., with NH>1024cm–2) sources in our sample. The presence of a population of heavily obscured AGN is corroborated by the X-ray-to-[NeV] ratio; we estimated, by means of an X-ray stacking technique and simulations, that the Compton-thick fraction in our sample of type 2 AGN is 43±4% (statistical errors only), which agrees well with standard assumptions by XRB synthesis models.

Abstract Copyright: ∼

Journal keyword(s): galaxies: active - X-rays: galaxies

Simbad objects: 1

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Number of rows : 1
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NAME COSMOS Field reg 10 00 28.60 +02 12 21.0           ~ 2973 0

Query : 2013A&A...556A..29M

Basic data :
NAME COSMOS Field -- Region defined in the Sky
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases

Other object types: 		reg ()
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) : 		10 00 28.60 +02 12 21.0 [ ] D 2007ApJS..172..523M
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
FK4 coord. (ep=B1950 eq=1950) : 		09 57 53.49 +02 26 47.1 [ ]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
Gal coord. (ep=J2000) : 		236.82224 +42.12163 [ ]
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', {sourceSize:12, color:'#30a090'})); aladin.on('objectClicked', function(object) { var objName=object.data.MAIN_ID; aladin.showPopup(object.ra,object.dec,'',''+ objName+''); });" title="Show Simbad objects"> Overlay Simbad points in this preview
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NAME COSMOS Field

References (2973 between 1850 and 2024) (Total 2973)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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