2011A&A...534A..23G


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.18CET16:16:36

2011A&A...534A..23G - Astronomy and Astrophysics, volume 534A, 23-23 (2011/10-1)

On the Lx - L6µm ratio as a diagnostic for compton-thick AGN.

GEORGANTOPOULOS I., ROVILOS E., AKYLAS A., COMASTRI A., RANALLI P., VIGNALI C., BALESTRA I., GILLI R. and CAPPELLUTI N.

Abstract (from CDS):

As the mid-IR luminosity represents a good isotropic proxy of the AGN power, a low X-ray to mid-IR luminosity ratio is often claimed to be a reliable indicator of Compton-thick AGN. We assess the efficiency of the X-ray to mid-IR luminosity ratio diagnostic by examining the 12 µm IRAS AGN sample (intrinsic L2–10keV>1042erg/s) for which high signal-to-noise ratio XMM-Newton observations are now available. We find that the vast majority (ten out of eleven) of the AGN that were classified as Compton-thick on the basis of X-ray spectroscopy by Brightman & Nandra have a low LX/L6µm luminosity ratio, i.e. lower than a few percent of the average AGN ratio, as is typical of reflection-dominated Compton-thick sources. At low LX/L6µm ratios, we also find a comparable number of AGN, most of which are heavily absorbed but not Compton-thick. This implies that although most Compton-thick AGN have low LX/L6µm ratios, at least in the local, Universe, the converse is not necessarily true. We then extend our analysis to higher redshifts. We perform the same analysis in the Chandra Deep Field South, for which excellent quality Chandra (4Ms) and XMM-Newton (3Ms) X-ray spectra are available. We derive accurate X-ray luminosities for Chandra sources using X-ray spectral fits, as well as 6µm luminosities from spectral energy distribution fits. We find in total eight AGN (intrinsic L2–10keV>1042erg/s) with low LX/L6µm ratios, after excluding one source where the 6µm emission primarily comes from star-formation. One of these sources has been already found to host a Compton-thick nucleus, while for another one at a redshift of z=1.22 we argue it is most likely Compton-thick on the basis of its combined Chandra and XMM-Newton spectrum. In agreement with the low redshift sample, we find a large number of non Compton-thick ``contaminants'' with low X-ray to mid-IR luminosity ratios. Our results suggest that a low LX/L6µm ratio alone cannot help us to ascertain whether a Compton-thick AGN is present, albeit the majority of low LX/L6µm AGN are heavily obscured. More interestingly, the two most reliable Compton-thick AGN in the high redshift Universe have high LX/L6µm ratios, showing that this method cannot provide complete Compton-thick AGN samples.

Abstract Copyright:

Journal keyword(s): X-rays: general - X-rays: diffuse background - X-rays: galaxies - infrared: galaxies

CDS comments: Paragraph 3.3 IRAS 20547 not identified (incomplete format).

Simbad objects: 46

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Number of rows : 46

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 34 Sy2 00 11 06.612 -12 06 28.33   14.14 13.52     ~ 303 0
2 NGC 424 Sy2 01 11 27.6374462713 -38 05 00.404099901   13.76 14.12 12.38 12.8 ~ 268 0
3 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 3992 2
4 NGC 1194 Sy2 03 03 49.100 -01 06 12.99   15.29 14.18     ~ 191 0
5 NGC 1320 Sy2 03 24 48.6903707574 -03 02 32.121207374   14.0 14.00     ~ 226 0
6 [LBX2017] 16 AGN 03 31 46.620 -27 45 52.09   25.51 25.45 24.96 23.99 ~ 13 0
7 [LBX2017] 172 AGN 03 32 08.383 -27 40 46.75   28.32 27.71   25.87 ~ 30 0
8 2MASS J03320855-2746483 AGN 03 32 08.560 -27 46 48.37   21.478   19.224 18.955 ~ 52 0
9 [LBX2017] 290 AGN 03 32 16.14982 -27 49 41.6993   21.553   21.322 20.476 ~ 41 1
10 [LBX2017] 304 AGN 03 32 17.04953 -27 49 21.8096   20.000 20.295 19.755 19.524 ~ 34 0
11 [SWM2014] GOODS-S 13628 Sy2 03 32 18.3389 -27 50 55.176   24.89 24.190 23.82 23.039 ~ 69 0
12 [SWM2014] GOODS-S 31295 AGN 03 32 18.44318 -27 45 55.8709   22.344 23.35 25.010 21.267 ~ 35 1
13 [LBX2017] 387 AGN 03 32 21.979 -27 51 11.80   27.075 28.72   26.930 ~ 14 0
14 [SWM2014] GOODS-S 36189 AGN 03 32 22.585 -27 44 25.84   22.46 21.570 21.101 20.606 ~ 48 1
15 NAME Chandra Deep Field-South reg 03 32 28.0 -27 48 30           ~ 1753 1
16 [VV2006] J033229.9-275106 Sy2 03 32 29.8487 -27 51 05.879   27.6 25.05 23.970 24.54 ~ 82 0
17 CXOCDFS J033231.5-274624 AGN 03 32 31.46027 -27 46 23.1871 25.05 23.96 23.64 23.28 23.001 ~ 74 0
18 [LBX2017] 623 AGN 03 32 33.436 -27 52 27.88   31.457 27.72   27.963 ~ 29 0
19 NAME BzK 4892 AGN 03 32 35.7111 -27 49 16.022   25.681 27.798 25.00 24.645 ~ 63 0
20 [SWM2014] GOODS-S 2546 Sy2 03 32 46.4092 -27 54 13.959   23.06 21.86 20.683 19.999 ~ 40 0
21 [LBX2017] 867 AGN 03 32 49.21541 -27 40 50.3803   22.613 22.99 22.61 21.51 ~ 43 0
22 [DSS2017] 1988 AGN 03 32 52.32 -27 45 42.0   23.59 23.50 23.22 22.763 ~ 18 0
23 NGC 1667 Sy2 04 48 37.205 -06 19 11.47   13.66 12.86 11.72   ~ 326 1
24 IRAS 07598+6508 Sy1 08 04 30.4643075056 +64 59 52.790728532   14.3 15.5     ~ 211 0
25 UGC 5101 Sy1 09 35 51.694 +61 21 10.52   15.20 15.50     ~ 500 4
26 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5223 6
27 NAME COSMOS Field reg 10 00 28.60 +02 12 21.0           ~ 1894 0
28 NGC 3256 IG 10 27 51.284 -43 54 13.55   11.83 11.33 10.62 11.9 ~ 734 2
29 Mrk 231 Sy1 12 56 14.2340989340 +56 52 25.238555193   14.68 13.84     ~ 1739 3
30 NGC 4968 Sy2 13 07 05.976 -23 40 37.34   13.78 14.79 12.46   ~ 160 1
31 NGC 5256 PaG 13 38 17.8 +48 16 41   14.1 13.42     ~ 394 2
32 Mrk 273 Sy2 13 44 42.070 +55 53 13.17   15.68 14.91     ~ 814 3
33 Mrk 463 Sy2 13 56 02.9 +18 22 18   14.8 14.22     ~ 349 2
34 NAME IRAS F15163+4255 NW LIN 15 18 06.123 +42 44 44.59   15.0 15     ~ 175 1
35 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2625 4
36 IRAS 15480-0344 Sy2 15 50 41.521 -03 53 17.58   16.20 15.1 14.83   ~ 80 0
37 NGC 6090 PaG 16 11 40.3 +52 27 21   14.0       ~ 392 2
38 NGC 6552 Sy2 18 00 07.2507502885 +66 36 54.347573772   14.6       ~ 130 2
39 NAME Superantennae Sy2 19 31 21.4252803168 -72 39 21.448768732   17.39 16.37 14.65   ~ 275 2
40 NGC 6890 Sy2 20 18 18.1048952350 -44 48 24.732671687   13.06 14.02 11.57   ~ 151 0
41 ESO 286-19 LIN 20 58 26.8182983654 -42 38 59.418569678   14.79 14.79 14.20   ~ 244 0
42 NAME South America H2G 22 51 49.307 -17 52 23.96   16.97       ~ 282 3
43 NGC 7479 Sy2 23 04 56.668 +12 19 22.36 11.74 11.60 10.85 10.47 9.66 ~ 652 2
44 ESO 148-2 Sy2 23 15 46.772 -59 03 15.94   14.94 14.73 13.95   ~ 232 1
45 NGC 7582 GiP 23 18 23.621 -42 22 14.06 11.62 10.92 10.62     ~ 778 2
46 NGC 7674 Sy2 23 27 56.6974755223 +08 46 44.238278540 13.84 13.92 13.23 12.64   ~ 621 4

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2019.11.18-16:16:36

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