2009A&A...498...67L


C.D.S. - SIMBAD4 rel 1.7 - 2021.01.24CET01:59:14

2009A&A...498...67L - Astronomy and Astrophysics, volume 498, 67-81 (2009/4-4)

Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios.

LANZUISI G., PICONCELLI E., FIORE F., FERUGLIO C., VIGNALI C., SALVATO M. and GRUPPIONI C.

Abstract (from CDS):

Recent works have suggested that selection criteria based on mid-IR properties, i.e. extreme colors and bright flux levels, can be used to reveal a population of dust-enshrouded, extremely-luminous quasars at z∼1-2. However, the X-ray spectral properties of these intriguing objects still remain largely unexplored. We have performed an X-ray study of a large sample of bright mid-IR (F24µm>1.3mJy) galaxies showing an extreme MIR/Optical flux ratio (F24µm/FR>2000) in order to confirm the presence of a luminous active nucleus in these very red objects. Sampling of a large area is required to pick up objects at the highest luminosities given their low surface density. Accordingly, we have applied our selection criteria to an area of ∼6deg2 covered by XMM-Newton/Chandra observations within the ∼50deg2 SWIRE survey, resulting in a final sample of 44 objects. The vast majority of the source redshifts, both spectroscopic and photometric, are in the range 0.7 ≲ z ≲ 2.5. The X-ray coverage of the sample is highly inhomogeneous (from snap-shot 5ks Chandra observations to medium-deep XMM-Newton exposures of 70ks) and, consequently, a sizable fraction of them (≃43%) remains undetected in the 0.5-10keV band. Using spectral or hardness information we were able to estimate the value of the absorbing column density in 23 sources. 95% of them are consistent with being obscured by neutral gas with an intrinsic column density of NH≥1022cm–2. Remarkably, we also find that ∼55% of these sources can be classified as type 2 quasars on the basis of their absorption properties and X-ray luminosity. Moreover, most of the X-ray undetected sources show extreme mid-IR colors, consistent with being luminous AGN-powered objects, suggesting they might host heavily obscured (possibly Compton-thick) quasars in X-rays. This demonstrates that our selection criteria applied to a wide area survey is very efficient in finding a large number of type 2 quasars at z>1. The existence of this class of very powerful, obscured quasars at high z could have important implications in the context of the formation and cosmological evolution of accreting supermassive black holes and their host galaxies.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: high-redshift - galaxies: nuclei - infrared: galaxies - X-rays: galaxies

Nomenclature: Table 1, col(2): SWIRE JHHMMSS.ss+DDMMSS.s N=44.

CDS comments: Table 1, col(1): numbering NN is not used in SIMBAD, objects are SWIRE JHHMMSS.ss+DDMMSS.s.

Simbad objects: 57

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Number of rows : 57

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 SWIRE J003314.61-432300.3 AGN 00 33 14.61 -43 23 00.3   24.290 24.710 24.13   ~ 3 0
2 2XMM J003317.0-431705 AGN 00 33 16.92 -43 17 06.3       24.332   ~ 4 0
3 2XMM J003333.7-432328 G 00 33 33.75 -43 23 26.9       24.41   ~ 2 0
4 2XMM J003336.1-431732 G 00 33 36.26 -43 17 31.7       24.65   ~ 2 0
5 SWIRE J003348.18-432822.3 G 00 33 48.18 -43 28 22.3       26.63   ~ 2 0
6 ELAIS S1 reg 00 34 44 -43 28.2           ~ 160 0
7 SWIRE J003518.20-433414.6 G 00 35 18.20 -43 34 14.6       25.19   ~ 1 0
8 SWIRE J003641.47-432038.1 G 00 36 41.47 -43 20 38.1       23.91   ~ 3 0
9 SWIRE J021559.46-045517.5 G 02 15 59.46 -04 55 17.5       25.65   ~ 1 0
10 SWIRE J021625.91-050425.1 G 02 16 25.91 -05 04 25.1       24.39   ~ 1 0
11 SWIRE J021656.59-051005.3 G 02 16 56.59 -05 10 05.3       24.31   ~ 3 0
12 SWIRE J021734.65-051718.2 G 02 17 34.65 -05 17 18.2       26.36   ~ 1 0
13 SWIRE J021743.09-044921.6 G 02 17 43.09 -04 49 21.6       24.20   ~ 1 0
14 2XMM J021749.0-052306 AGN 02 17 49.015 -05 23 06.76   23.4797 22.8329 22.36   ~ 11 0
15 2XLSSd J021754.8-043014 AGN 02 17 54.45 -04 30 16.0   23.3858 22.9318 23.34   ~ 4 0
16 SWIRE J021912.66-043308.5 G 02 19 12.66 -04 33 08.5       23.80   ~ 1 0
17 SWIRE J021924.57-045300.0 G 02 19 24.57 -04 53 00.0   26.0278 22.9304 25.26   ~ 6 0
18 SWIRE J021935.19-050528.4 AGN 02 19 35.19 -05 05 28.4   22.3043 21.7868 22.70   ~ 4 0
19 2XMM J022003.6-045145 AGN 02 20 03.58 -04 51 45.6       23.07   ~ 2 0
20 SWIRE J022003.95-045220.4 G 02 20 03.95 -04 52 20.4       24.22   ~ 2 0
21 NAME Chandra Deep Field-South reg 03 32 28.0 -27 48 30           ~ 1854 1
22 2MASS J09134545+4056282 Sy2 09 13 45.4949162350 +40 56 28.214305677   19.69 19.21     ~ 236 2
23 NAME COSMOS Field reg 10 00 28.60 +02 12 21.0           ~ 2180 0
24 [OM2008] 100 QSO 10 44 09.95 +58 52 24.7 24.29     23.56   ~ 25 0
25 NAME Lockman Hole reg 10 45 00.0 +58 00 00           ~ 757 0
26 SWIRE J104528.29+591326.7 QSO 10 45 28.33 +59 13 26.9       23.68   ~ 11 0
27 SWIRE J104837.82+572816.2 G 10 48 37.82 +57 28 16.2       23.84   ~ 1 0
28 SWIRE J104847.14+572337.6 AGN 10 48 47.14 +57 23 37.6       23.74   ~ 6 0
29 SWIRE J104954.96+584429.4 G 10 49 54.96 +58 44 29.4       24.15   ~ 1 0
30 5MUSES 138 AGN 10 56 04.860 +57 42 30.20       22.21   ~ 5 0
31 NGC 6051 BiC 16 04 56.704 +23 55 58.34   14.9       ~ 104 2
32 SWIRE J160623.44+542301.9 G 16 06 23.44 +54 23 01.9       24.59   ~ 1 0
33 SWIRE J160650.71+542510.1 G 16 06 50.724 +54 25 10.19       24.30   ~ 3 0
34 SWIRE J160700.62+542416.8 G 16 07 00.62 +54 24 16.8       26.02   ~ 1 0
35 SWIRE J160734.22+544217.3 AGN 16 07 34.22 +54 42 17.3           ~ 2 0
36 SWIRE J160813.86+541942.4 G 16 08 13.86 +54 19 42.4       25.09   ~ 3 0
37 SWIRE J160816.15+545351.1 G 16 08 16.15 +54 53 51.1       24.12   ~ 2 0
38 SWIRE J160913.02+540509.7 G 16 09 13.02 +54 05 09.7       25.31   ~ 1 0
39 SWIRE J160913.28+542322.0 AGN 16 09 13.28 +54 23 22.0       23.86   ~ 2 0
40 SWIRE J160933.78+535720.2 G 16 09 33.78 +53 57 20.2           ~ 1 0
41 SWIRE J160945.43+534944.6 IR 16 09 45.43 +53 49 44.6           ~ 1 0
42 SWIRE J160950.98+535836.3 G 16 09 50.98 +53 58 36.3       23.95   ~ 1 0
43 ELAIS N1 reg 16 10 01 +54 30.6           ~ 317 0
44 SWIRE J161007.17+540628.5 G 16 10 07.17 +54 06 28.5       23.34   ~ 1 0
45 SWIRE J161017.70+535124.1 G 16 10 17.70 +53 51 24.1       24.80   ~ 1 0
46 SWIRE J161017.93+542332.1 AGN 16 10 17.93 +54 23 32.1           ~ 2 0
47 SWIRE J161037.63+540603.5 G 16 10 37.63 +54 06 03.5       24.88   ~ 1 0
48 SWIRE J161051.03+535330.5 G 16 10 51.03 +53 53 30.5       25.39   ~ 1 0
49 SWIRE J161052.74+543740.4 AGN 16 10 52.74 +54 37 40.4       23.53   ~ 2 0
50 SWIRE J161102.22+550551.6 G 16 11 02.22 +55 05 51.6       24.10   ~ 1 0
51 SWIRE J161204.84+544149.2 G 16 12 04.84 +54 41 49.2       25.07   ~ 3 0
52 SWIRE J161306.28+543959.7 G 16 13 06.28 +54 39 59.7       24.91   ~ 2 0
53 ELAIS N2 reg 16 36 48.0 +41 01 45           ~ 162 0
54 SWIRE J163723.94+410525.7 G 16 37 23.94 +41 05 25.7       23.80   ~ 1 0
55 [WLH2006] 8 G 17 12 05.123 +59 15 08.36           ~ 7 0
56 [WLH2006] SST24 J172249.03+585027.6 Rad 17 22 49.059 +58 50 28.38           ~ 4 0
57 4C 23.56 EmG 21 07 14.82 +23 31 45.0           ~ 96 0

    Equat.    Gal    SGal    Ecl

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2021.01.24-01:59:14

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