ady annuar - dartmouth collegehiddenmonsters/talks/annuar.pdfmotivations… 2 ctagn contributes...

With Dave Alexander (Durham), Poshak Gandhi (Southampton), George Lansbury (Durham) & the NuSTAR Obscured AGN team.

Ady Annuar (Durham)

MOTIVATIONS…

2

CTAGN contributes 10-25% of the CXB emission at 30 keV (e.g. Gilli+07).

Obscured but Compton-thin (NH = 1022 – 1024 cm-2 )

CT (NH > 1024 cm-2)

Unobscured (NH < 1022 cm-2)

Gilli et al. (2007)

Cosmic X-ray Background (CXB)

Total

Total

MOTIVATIONS…

3

Howimportant

areCompton-

thick AGN?

The three nearestAGN are all heavily-obscuredor Compton-thick!

Matt et al. (2000) •  All 3 AGN within D = 4Mpc are heavily obscured

(NH ≥ 1023 cm-2).

•  2/3 (~67%) are Compton-thick (CT)!

The Astrophysical Journal, 792:117 (13pp), 2014 September 10 Gandhi et al.

Table 3List of Bona Fide Local Compton-thick AGNs

Source Distance L2–10,in Reference(Mpc) (erg s−1)

NGC 424 52.6 43.33 1NGC 1068 14.4 43.58 2NGC 1320 40.7 42.88 1CGCG420-15 133.0 43.88 3, 4ESO 005-G004 28.5 41.97Mrk 3 60.0 43.23 5NGC 2273 31.7 42.39ESO 565-G019 78.4 43.00 6NGC 3079 19.7 42.27IC 2560 43.1 42.89 1NGC 3281 52.4 43.22Mrk 34 236.0 43.95 4NGC 3393 50.0 42.92 7Arp 299B 44.0 43.18 8NGC 4102 19.0 42.24 9NGC 4939 51.1 42.74NGC 4945 3.8 42.52 10NGC 5194 8.1 40.70Circinus 4.2 42.58 11NGC 5728 30.0 42.77ESO 138-G001 41.5 42.58NGC 6240 112.0 44.08 12, 13NGC 7582 22.0 42.58

Notes. Distances are redshift-independent estimates from NED forthe closest sources, or luminosity distances from the respectivereferences, which were corrected for cosmology.References. (1) Balokovic et al. 2014; (2) F. E. Bauer et al. 2014(in preparation); (3) Severgnini et al. 2011; (4) this work; (5) Awakiet al. 2008; (6) Gandhi et al. 2013; (7) Fabbiano et al. 2011; (8) Ptaket al. 2014; (9) Gonzalez-Martın et al. 2011; (10) Puccetti et al. 2014;(11) Arevalo et al. 2014; (12) Vignati et al. 1999; (13) S. Puccettiet al. 2014 (in preparation). Where not stated, the reference is thecompilation by Goulding et al. (2012) and papers referred to therein.Mrk 231, NGC 7674, and IRAS 19254-72 are not included as a resultof recent updates to the intrinsic luminosities (see the text).

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At larger volume? Gandhi et al. (2014)

Compton-thick

Accretionin

thelocalUniverse

7

Table 1CT AGN in the Swift/BAT 70-months catalog.

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

SWIFT ID Counterpart Type z logNH Fe Kα EW Γ2−10 Γ logL 2−10 logL 14−150 Facility

[ cm−2] [eV] [ erg s−1] [ erg s−1]

SWIFT J0030.0−5904 ESO 112−6 · · · 0.0290 24.03 [23.79 – 24.43] 7300+4056−5641 −0.70+5.01

−NC 1.78+0.35−0.38 43.12 43.53 SX

SWIFT J0105.5−4213 MCG−07−03−007 2 0.0302 24.18 [23.95 – 24.30] ≤ 2246 −1.30+1.29−1.31 2.12+0.25

−0.41 43.46 43.55 SX

SWIFT J0111.4−3808 NGC 424 1.9 0.0118 24.33 [24.32 – 24.34] 928+109−72 0.11+0.06

−0.06 2.64+0.11−0.39 43.77 43.32 XE

SWIFT J0122.8+5003B MCG +08−03−018 2 0.0204 24.24 [24.09 – 24.58] ≤ 930 −0.29+0.36−0.97 2.71+0.05

−0.55 43.98 43.38 SX

SWIFT J0128.9−6039 2MASXJ01290761−6038423 · · · 0.2030 24.13 [23.90 – 24.32] ≤ 1204 −0.27+1.00−1.63 2.18+0.21

−0.36 45.23 45.23 SX

SWIFT J0130.0−4218† ESO 244−IG 030 2 0.0256 24.20 [24.02 – 24.55] NC 0.16+1.03−2.60 2.45+0.35

−0.40 43.68 43.42 SX

SWIFT J0242.6+0000 NGC 1068 2 0.0038 24.95 [24.63 – 25.16] 565+58−20 0.89+0.06

−0.06 2.37+0.10−0.08 42.93 42.76 XE

SWIFT J0250.7+4142 NGC 1106 21 0.0145 24.25 [24.08 – 24.54] ≤ 2558 0.83+1.21−2.28 1.87+0.26

−0.29 42.80 43.12 SX

SWIFT J0251.3+5441A 2MFGC 02280 2 0.0152 24.06 [23.96 – 24.18] 336+748−331 −2.17+0.67

−NC1.86+0.13

−0.21 43.02 43.36 SX

SWIFT J0251.6−1639 NGC 1125 2 0.0110 24.27 [24.03 – 24.59] ≤ 2023 0.03+1.47−1.93 2.01+0.29

−0.18 42.74 42.90 SX

SWIFT J0304.1-0108 NGC 1194 1.91 0.0136 24.33 [24.30 – 24.39] 768+235−241 0.21+0.12

−0.13 2.00+0.12−0.08 43.69 43.62 XE

SWIFT J0308.2−2258 NGC 1229 2 0.0360 24.94 [24.49 – NC] ≤ 1662 −1.51+1.20−1.36 2.14+0.43

−0.24 43.96 44.10 SX

SWIFT J0350.1−5019 ESO 201−4 2 0.0359 24.32 [24.25 – 24.35] 503+136−106 −0.40+0.25

−0.26 2.09+0.16−0.22 44.44 44.28 XE

SWIFT J0357.5−6255 2MASXJ03561995−6251391 1.9 0.1076 24.17 [23.99 – 24.38] ≤ 542 −2.77+2.08−NC 2.26+0.27

−0.32 44.84 44.77 SX

SWIFT J0427.6−1201† MCG−02−12−017 2 0.0325 24.25 [23.79 – 25.26] NC −0.59+1.24−NC 1.94+0.38

−0.43 43.41 43.67 SX

SWIFT J0453.4+0404 CGCG 420−015 2 0.0294 24.14 [23.93 – 24.18] 450+1725−24 −0.46+0.25

−0.26 2.27+0.12−0.40 44.00 43.93 XE

SWIFT J0601.9−8636 ESO 005− G 004 2 0.0062 24.34 [24.28 – 24.44] 1414+1175−1242 −0.86+0.22

−0.22 1.81+0.14−0.11 42.78 42.68 SuX

SWIFT J0615.8+7101 Mrk 3 1.9 0.0135 24.07 [24.03 – 24.13] 354+32−9 −0.52+0.04

−0.04 1.92+0.10−0.05 43.67 44.00 XE

SWIFT J0656.4−4921 2MASXJ06561197−4919499 2 0.0410 24.03 [23.93 – 24.33] ≤ 2224 −2.03+1.77−0.81 1.91+0.31

−0.25 43.48 43.77 SX

SWIFT J0714.2+3518A MCG +06−16−028 1.9 0.0157 24.80 [24.05 – NC] ≤ 6136 −1.65+1.77−1.12 1.92+0.42

−0.59 43.04 43.33 SX

SWIFT J0743.0+6513B Mrk 78 2 0.0371 24.11 [23.99 – 24.19] 366+2083−110 −0.49+0.51

−0.53 2.49+0.21−0.36 43.82 43.53 XE

SWIFT J0807.9+3859 Mrk 622 1.9 0.0232 24.29 [23.99 – NC] 597+567−324 −1.09+0.67

−0.74 2.10+0.22−0.84 43.26 43.37 XE

SWIFT J0902.7−6816B NGC 2788A 2 0.0133 25.55 [24.14 – NC] 3408+1770−3232 −1.74+1.36

−NC 1.58+0.68−0.11 43.03 43.64 SX

SWIFT J0919.2+5528 Mrk 106 1.9 0.1234 24.01 [23.86 – 24.15] ≤ 1736 −1.31+0.98−1.01 2.12+0.41

−0.17 44.54 44.62 SX

SWIFT J0924.2−3141 2MASXJ09235371−3141305 2 0.0424 24.11 [24.03 – 24.20] ≤ 1683 −2.10+0.99−NC 2.19+0.24

−0.11 44.14 44.04 SX

SWIFT J0934.7−2156 ESO 565−G019 21 0.0163 24.65 [24.48 – NC] 1100+600−600 0.60+0.52

−0.38 1.86+0.21−0.37 43.50 43.67 SuX

SWIFT J0935.9+6120 MCG +10−14−025 1.9 0.0394 24.35 [24.31 – 24.45] ≥ 222 0.01+0.34−0.36 2.33+0.25

−0.25 44.23 44.07 XE

SWIFT J1001.7+5543A NGC 3079 1.9 0.0037 25.10 [24.51 – NC] 1609+389−1541 0.90+0.50

−0.47 1.46+0.09−0.08 41.30 42.47 XE

SWIFT J1031.5−4205† ESO 317− G 041 · · · 0.0193 24.30 [24.08 – 24.73] NC −2.98+0.56−NC 2.20+0.27

−0.22 43.27 43.24 SX

SWIFT J1033.8+5257 SDSS J103315.71+525217.8 · · · 0.0653 24.27 [24.06 – 24.53] ≤ 1776 −0.93+0.55−1.62 2.35+0.24

−0.30 44.33 44.18 SX

SWIFT J1048.4−2511A NGC 3393 2 0.0125 24.50 [24.31 – 24.82] 1585+467−466 0.70+0.56

−0.55 1.79+0.18−0.22 42.63 43.02 XE

SWIFT J1206.2+5243 NGC 4102 2 0.0028 24.18 [24.06 – 24.27] 275+234−204 0.90+0.47

−0.45 1.80+0.18−0.23 41.66 42.04 XE

SWIFT J1212.9+0702† NGC 4180 21 0.0070 24.15 [23.93 – 24.42] NC −2.78+2.62−NC 1.75+0.29

−0.19 41.92 42.38 SX

SWIFT J1253.5−4137 ESO 323−32 2 0.0160 24.79 [24.39 – NC] 1787+226−217 −0.01+0.24

−0.25 1.96+0.42−0.58 43.16 43.39 SuX

SWIFT J1305.4−4928 NGC 4945 21 0.0019 24.80 [24.76 – 24.93] 863+46−42 −0.04+0.06

−0.06 1.80+0.05−0.06 42.07 43.07 XE

SWIFT J1412.9−6522 Circinus Galaxy 21 0.0014 24.40 [24.39 – 24.41] 2019+224−21 0.21+0.02

−0.02 2.50+0.01−0.01 42.63 42.37 XE

SWIFT J1416.9−4640 IGR J14175−4641 2 0.0766 24.35 [24.20 – 24.54] ≤ 938 −0.30+0.94−1.38 2.11+0.17

−0.24 44.71 44.80 SX

SWIFT J1432.8−4412 NGC 5643 2 0.0040 25.40 [25.06 – NC] 1640+2484−13 −0.30+0.12

−0.12 1.65+0.13−0.11 42.43 42.98 XE

SWIFT J1442.5−1715 NGC 5728 2 0.0093 24.13 [24.09 – 24.16] 780+1561−105 −1.20+0.17

−0.16 1.95+0.03−0.04 42.86 43.30 SuX

SWIFTJ1445.6+2702A CGCG164−019 1.91 0.0299 24.75 [24.60 – 25.49] ≤ 1282 0.10+0.70−0.81 2.15+0.32

−0.21 44.57 44.65 SX

SWIFT J1635.0−5804 ESO 137− G 034 2 0.0090 24.30 [24.23 – 24.37] 1112+2178−98 0.02+0.23

−0.23 2.14+0.17−0.17 42.65 42.71 XE

8Riccietal.

Table 1 — Continued

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

SWIFT ID Counterpart Type z logNH Fe Kα EW Γ2−10 Γ logL 2−10 logL 14−150 Facility

[ cm−2] [eV] [ erg s−1] [ erg s−1]

SWIFT J1643.2+7036A NGC 6232 2 0.0148 24.94 [24.53 – NC] ≤ 3314 −0.39+1.76−2.16 1.80+0.83

−0.35 42.82 43.19 SX

SWIFT J1652.0−5915A ESO 138− G 001 21 0.0091 25.25 [24.94 – NC] 885+79−84 −0.06+0.09

−0.09 2.19+0.07−0.07 44.09 44.26 XE

SWIFT J1652.9+0223 NGC 6240 1.9 0.0245 24.40 [24.32 – 24.45] 357+588−52 0.88+0.16

−0.16 2.33+0.06−0.10 44.75 44.62 XE

SWIFT J1800.3+6637 NGC 6552 21 0.0265 24.05 [23.83 – 24.40] 756+411−522 −2.66+1.75

−NC1.87+0.28

−0.30 43.27 43.59 XE

SWIFT J2015.2+2526† 2MASXJ20145928+2523010 2 0.0453 24.42 [24.25 – 24.62] NC 1.29+1.19−1.13 2.30+0.25

−0.29 44.59 44.50 SX

SWIFTJ2028.5+2543B,C NGC 6921 · · · 0.0145 24.27 [24.09 – 24.39] 944+373−292 0.47+0.33

−0.34 1.96+0.14−0.12 42.88 43.12 XE

SWIFT J2102.6−2810 ESO 464− G016 2 0.0364 24.19 [23.94 – 24.59] ≤ 909 −1.86+1.82−NC 2.00+0.24

−0.32 43.74 43.91 SX

SWIFT J2148.3−3454 NGC 7130 1.9 0.0162 24.00 [23.90 – 24.21] ≤ 1716 1.07+0.73−0.62 2.05+0.09

−0.08 42.13 42.93 CA

SWIFT J2207.3+1013A NGC 7212 NED02 2 0.0267 24.41 [24.34 – 24.48] ≥ 454 −0.12+0.22−0.22 2.20+0.32

−0.39 44.41 43.94 XE

SWIFT J2242.4−3711† ESO 406− G 004 · · · 0.0290 24.74 [24.19 – NC] NC NC 2.04+0.78−0.96 43.44 43.59 SX

SWIFT J2304.9+1220 NGC 7479 1.9 0.0079 24.16 [24.03 – 24.28] 684+259−672 −1.59+1.20

−1.27 1.81+0.26−0.26 42.07 42.44 XE

SWIFT J2307.9+2245† 2MASXJ23074887+2242367 21 0.0350 24.20 [24.00 – 24.50] NC NC 1.89+0.28−0.30 43.48 43.79 SX

SWIFT J2318.4−4223 NGC 7582 2 0.0052 24.33 [24.32 – 24.34] 515+150−6 −0.15+0.04

−0.04 2.33+0.05−0.06 43.48 43.23 XE

SWIFT J2328.9+0328 NGC 7682 1.9 0.0171 24.30 [24.18 – 24.38] ≥ 63 −0.61+0.44−0.47 2.18+0.18

−0.21 43.50 43.51 XE

Note. — The table reports the (1) Swift ID, (2) counterpart name, (3) optical classification, (4) redshift, (5) value and 90% confidence interval of the column density, (6) Fe Kα EW,(7) photon index obtained by fitting the spectrum in the 2–10 keV range with a power-law, (8) photon index obtained by fitting the 0.3–150 keV spectrum (see Sect. 2), (9) 2–10 keVand (10) 14–150 keV intrinsic (i.e. absorption and k-corrected) luminosities, and (11) X-ray observatory used for the soft X-ray spectra (CA=Chandra/ACIS; SuX=Suzaku/XIS;SX=Swift/XRT; XE=XMM-Newton/EPIC). The optical classifications are taken from the Swift/BAT Spectral Survey (BASS paper I, Koss et al. in prep.) unless stated otherwise.BASS will report the optical characteristics of more than 500 BAT selected AGN. Dots are reported when no optical classification is available. Newly identified CT AGN are reportedin boldface.A Sources reported to be CT by Koss et al. (in prep.) thanks to NuSTAR observations.B Sources reported to be Compton-thin by previous works due to the narrower energy band used for the X-ray spectral analysis.C Swift/BAT flux due to the combined emission of NGC6921 and MCG+04−48−002. The 14–150 keV luminosity reported refers only to NGC69211 Optical classification from the literature.†

Fe Kα line not detected because of the low signal-to-noise ratio of the Swift/XRT observation.NC value not constrained.

Ricci et al. (2016)

23 bona-fide CTAGN within D ~ 200 Mpc.

Corresponds to <<1% of the expected AGN population

within this volume!

~8% in Swift-BAT (<z> ~ 0.055)

AGN NH DISTRIBUTION

5

NH Distribution of AGN is highly uncertain at high obscuration end.

Obscuring column density distribution and intrinsic AGN powers very uncertain at high obscuration end

Burlon et al. 2011Burlon et al. (2011)

AGN NH DISTRIBUTION

6

Obscuring column density distribution and intrinsic AGN powers very uncertain at high obscuration end

Burlon et al. 2011

Need a representative AGN sample to more completely constrain the population of

CTAGN and NH distribution of AGN population

in the local universe. Burlon et al. (2011)

NH Distribution of AGN is highly uncertain at high obscuration end.

7

THE SAMPLE: Mid-IR SELECTED, VOLUME-LIMITED (D<15Mpc)

Goulding & Alexander (2009) 1166 A. D. Goulding and D. M. Alexander

and X-ray observations (Iwasawa et al. 1993). Various studies havesuggested that NGC 4945 is unlikely to be a particularly unusualAGN (e.g. Lutz et al. 2003; Maiolino et al. 2003), indicating thatthere may be many more optically unidentified AGN in the localUniverse.

X-ray observations have revealed potential AGN in many galax-ies in the Ho97 sample lacking optical AGN signatures (e.g. Hoet al. 2001; Desroches & Ho 2009). However, there is often am-biguity over whether an AGN is producing the X-ray emission inthese galaxies (e.g. there can be significant contamination fromX-ray binaries). Furthermore, the X-ray emission from Compton-thick AGN (NH > 1.5 × 1024 cm−2) can be extremely weak, mak-ing it challenging to identify the most heavily obscured AGNusing X-ray data alone (i.e. the <10 keV emission can be afactor ≈30–1000 times weaker than the intrinsic emission; e.g.Risaliti, Maiolino & Salvati 1999; Matt et al. 2000). By compar-ison, due to the extreme conditions required to produce the high-ionization emission line [Ne V] λ14.32, 24.32 µm (97.1 eV), mid-IRspectroscopy provides an unambiguous indicator of AGN activityin nearby galaxies (e.g. Weedman et al. 2005; Armus et al. 2006).1

The relative optical depth at mid-IR wavelengths is also consider-ably lower than at optical wavelengths (Aλ14.3 µm/AV ≈ 50; Li &Draine 2001). Even heavily Compton-thick AGN that are weak atX-ray energies can be identified using mid-IR spectroscopy (e.g. thewell-studied NGC 1068 with NH > 1025 cm−2 has bright [Ne V]λ14.32 µm emission; Sturm et al. 2002). Thus, the identification ofhigh-ionization [Ne V] λ14.32, 24.32 µm provides a relatively op-tically thin means by which to probe the central engine of nearbyAGN. On the basis of the identification of [Ne V] emission in aheterogeneous sample of late-type spiral galaxies within the localUniverse, Satyapal et al. (2008, hereafter S08) have suggested thata large number of Sc–Sm galaxies host optically unidentified AGNactivity.

Local mid-IR surveys [e.g. Sturm et al. 2002; the Spitzer InfraredNearby Galaxy Survey (SINGS) Legacy Project (Dale et al. 2006;hereafter D06) and S08] have shown the advantages of using mid-IR spectroscopy as an AGN diagnostic. However, none of thesestudies has used this diagnostic to provide a complete unambigu-ous census of AGN activity within the local Universe. Here, weuse sensitive high-resolution Spitzer–IRS spectroscopy to identifyAGN within a complete (≈94 per cent) volume-limited survey ofthe most bolometrically luminous galaxies (LIR > 3 × 109 L⊙)to a distance of D < 15 Mpc.2 By selecting galaxies at IR wave-lengths, our sample will comprise the most active galaxies in thelocal Universe and will also include the most dust-obscured sys-tems. We use these data to unambiguously identify AGN using thehigh-ionization [Ne V] λ14.32 µm emission line to produce the mostsensitive census of AGN activity in the local Universe to date. InSection 2, we outline the construction and data reduction analysisof the sample assembled from the IRAS Revised Bright Galaxy Sur-vey (RBGS) of Sanders et al. (2003). In Section 3, we determinethe fraction of local galaxies hosting AGN activity, explore theirproperties and compare the results to the previous optical survey ofHo97 to address the key question: why are a large number of AGNunidentified at optical wavelengths? In Section 4, we present ourconclusions.

1 We note that [O IV] λ25.9 µm (54.9 eV) is also often used for AGNidentification, although energetic starbursts can also produce luminous [O IV]emission; see Section 3.4.2 LIR corresponds to the 8–1000 µm luminosity, as defined by Sanders &Mirabel (1996).

Figure 1. Logarithm of IR luminosity versus luminosity distance for allobjects in the RBGS (Sanders et al. 2003; squares). The 64 IR-bright galaxies(LIR ≈ 3 × 109 L⊙) to D < 15 Mpc with high-resolution Spitzer–IRSspectroscopy are explored here (stars).

2 TH E S A M P L E A N D DATA R E D U C T I O N

2.1 Sample selection

Using IRAS, the RBGS (Sanders et al. 2003) has provided an accu-rate census of all IR-bright galaxies (|b| > 5◦, f 60 µm > 5.24 Jy) inthe local Universe. The aim of our study is to identify AGN activityin the most bolometrically luminous galaxies (LIR > 3 × 109 L⊙)out to D < 15 Mpc.3 The distance constraint of 15 Mpc was placedso as to not include the Virgo cluster at 16 Mpc (i.e. to be repre-sentative of field-galaxy populations). The IR luminosity thresholdwas chosen to be well matched to the flux limit of the RBGS (seeFig. 1) and ensures that we do not include low-luminosity dwarfgalaxies and relatively inactive galaxies. In the RBGS, there are 68IRAS detected galaxies to a distance of D < 15 Mpc with LIR >

3 × 109 L⊙, 64 of which have Spitzer–IRS high-resolution spec-troscopy publicly available (i.e. ≈94 per cent complete): P3124 (28objects; PI: D.M. Alexander); P159 [18 objects; PI: R. Kennicutt(SINGS)]; P14 (11 objects; PI: J.R. Houck); P59 (four objects; PI:G. Rieke) and P86 (three objects; PI: M. Werner).

In Fig. 1, we plot IR luminosity versus luminosity distance forthe RBGS and highlight the 64 galaxies with Spitzer–IRS obser-vations in our D < 15 Mpc sample. The basic properties fromthe RBGS for the sources are combined with published opticaldata and listed in Table 1. The objects are all late-type galaxies(Hubble classification of S0 or later), which is unsurprising sinceearly-type galaxies are typically IR faint and undetected by IRAS(e.g. Knapp et al. 1989). The four galaxies that match our selec-tion criteria but lack sufficient high-resolution Spitzer–IRS obser-vations of the central regions are shown in Table 2. Specifically,NGC 3486 has short-high (SH) and long-high (LH) observationsbut the data are noisy and no statistically useful information can be

3 Distances have been calculated using the cosmic attractor model of Mouldet al. (2000), which adjusts heliocentric redshifts to the centroid of the localgroup, taking into account the gravitational attraction towards the Virgocluster, the Great Attractor and the Shapley supercluster.

C⃝ 2009 The Authors. Journal compilation C⃝ 2009 RAS, MNRAS 398, 1165–1193

at University of D

urham on M

arch 19, 2014http://m

nras.oxfordjournals.org/D

ownloaded from

Goulding & Alexander (2009)

8

GA09 GA09

The Incidence of Growing SMBHs

A. D. Goulding

12

e.g.; High-‐resolu4on (R~600) Spitzer-‐IRS Spectra of NGC 1448

•  Mid-IR emission line (λ = 14.32μm). •  Very high-ionization

potential (97.1 eV). •  Optical depth at mid-

IR is relatively low. à Can identify AGN that

are not identified in optical due to host obscuration.

à Can identify the most heavily CTAGN that are weak/missed in X-ray

[NeV] AS AN UNAMBIGUOUS AGN INDICATOR

9

SELECTING CTAGN CANDIDATES IN THE SAMPLE

Method Description Advantage Disadvantage X-ray

Spectroscopy •  NH measurements through

broadband X-ray spectroscopy (E > 10 keV). •  Strong Iron Kα line

(EW > 1 keV). •  Flat photon index (Γ ≤ 1) at

E < 10 keV.

•  Direct NH measurements.

•  Misses heavily CTAGN

(NH > 1025 cm-2).

[OIII]:X-ray diagnostic

•  F2-10 keV,obs/F[OIII],corr < 1 (Bassani et al. 1999)

•  Traces ionized gas in the NLR (extends beyond the torus).

•  NLR can be affected by large scale obscuration.

•  Relationship has large scatter

Mid-IR:X-ray relation

•  F2-10keV,obs/F12µm< 0.04 (Asmus et al. 2015)

•  Most of the absorbed radiation is re-emitted in Mid-IR by the torus.

•  Contamination by host galaxy.

10






E < 10 keV.



(NH > 1025 cm-2).










11






E < 10 keV.



(NH > 1025 cm-2).










AGN log NH [cm-2] Classification

NGC 1068 > 25.0 CT NGC 4945 24.7 CT NGC 5194 24.7 CT Circinus 24.6 CT

NGC 0613 23.6 No NGC 4051 23.3 No NGC 6300 23.3 No NGC 5128 23.0 No NGC 4565 21.4 No NGC 5033 < 20.9 No NGC 5643 ? ? NGC 1448 ? ? NGC 0660 ? ? NGC 3486 ? ?

NGC 3627 ? ? NGC 5195 ? ? NGC 3621 ? ? NGC 3628 ? ? NGC 1792 ? ?

ESO 121-G6 ? ?

D < 15 Mpc AGN SAMPLE

Note: NH values are only given here for those with high S/N X-‐ray spectroscopic data available.

NH Distribu4on at D < 15 Mpc

The rest of the sample?

AGN log NH [cm-2] Classification

NGC 1068 > 25.0 CT NGC 4945 24.7 CT NGC 5194 24.7 CT Circinus 24.6 CT

NGC 0613 23.6 No NGC 4051 23.3 No NGC 6300 23.3 No NGC 5128 23.0 No NGC 4565 21.4 No NGC 5033 < 20.9 No NGC 5643 ? ? NGC 1448 ? ? NGC 0660 ? ? NGC 3486 ? ?

NGC 3627 ? ? NGC 5195 ? ? NGC 3621 ? ? NGC 3628 ? ? NGC 1792 ? ?

ESO 121-G6 ? ?

D < 15 Mpc AGN SAMPLE

Pre-NuSTAR constraints:

Note: NH values are only given here for those with high S/N X-‐ray spectroscopic data available.



20% (up to 70%) are CT

*: 12μm flux was predicted from [NeV]:12μm rela4on. †: Detec4on of strong Fe Kα line in Chandra observa4on. ‡: This source has been suggested to be CT in several literatures e.g.; Cappi et al. (2006).



CTAGN Candidates

AGN with NH measurements from high S/N X-‐ray data. CT Candidates based on our analyses.

AGN Optical MIR log NH [cm-2] (X-ray)

Final Classification

NGC 1068 CT CT > 25.0 CT NGC 4945 No No 24.7 CT NGC 5194 CT CT 24.7 CT Circinus CT CT 24.6 CT

NGC 0613 No No 23.6 No NGC 4051 No No 23.3 No NGC 6300 No No 23.3 No NGC 5128 No No 23.0 No NGC 4565 No ?* 21.4 No NGC 5033 No No < 20.9 No NGC 5643 CT CT ? CT NGC 1448 ? CT ? CT? † NGC 0660 CT CT* ? CT? NGC 3486 No ? ? CT? ‡

NGC 3627 CT CT ? CT? NGC 5195 No CT* ? ? NGC 3621 No CT* ? ? NGC 3628 No ? ? ? NGC 1792 ? No ? ?

ESO 121-G6 ? ? ? ? CT % 30% 45% 20% 25-45%

16

Case Study: NuSTAR Observations of NGC 5643

AGN

ULX

Annuar et al. 2015

17

Swib-‐BAT NuSTAR

XMM-‐Newton + Chandra

TORUS Model (Brightman & Nandra 11)

MYTorus Model (Murphy & Yaqoob 09)

PEXRAV Model (Magdziarz & Zdziarski 95)

NH ≥ 5 × 1024 cm-2 (CT!) Γ = 1.8-2.1 L2-10,observed = (1.6-1.7) × 1040 erg s-1 L2-10,intrinsic = (0.8-1.7) × 1042 erg s-1

Annuar et al. 2015

Case Study: NGC 5643 - X-ray Broadband Spectral Fitting Results

18

Case Study: NGC 1448 - Background

The Incidence of Growing SMBHs

A. D. Goulding

12

•  D = 11.5 Mpc •  Was optically classified as HII galaxy. •  AGN was discovered by Goulding & Alexander

(2009) through the detection of [NeV] line.

Case Study: NGC 1448 – High Spatial Resolution Mid-IR Observation (Gemini/TReCS)

Annuar et al. submitted

4 A. Annuar et al.

Figure 2. Optical R-band image of NGC 1448 taken with the ESO NTT. The aperture used to extract the optical spectra of the AGN,optical peak and the total galaxy are plotted using cyan rectangle regions, and labeled as 1, 2 and 3, respectively. The zoom-in image ofthe central 2000 ⇥ 2000 of the galaxy is shown in the bottom-right panel. “⇥” marks the sources detected within a 2000 circular radius ofthe AGN in the Chandra 2–8 keV band image.

Figure 3. Top: High spatial resolution MIR image of NGC 1448taken by Gemini/T-ReCS. Bottom: Image fits performed using themirphot task in idl following Asmus et al. (2014). Shown are thecentral 4.005 ⇥ 4.005 of the image. The left column is the originalimage, the middle column is the fit performed on the data, andthe right column is the residual after subtracting the fit from thedata. The top row shows the results from a Gaussian fit to thetotal emission, and the bottom row shows the results from fittingthe standard star (as a PSF reference) to the total emission. Northis up and east is to the left in all images.

2.2. Chandra

NGC 1448 was observed by Chandra in 2014 with theACIS-S detector with an exposure time of 49.4 ks (50.1

ks on-source time) as part of the Chandra HRC-GTOprogram (2014-03-09; PI S. Murray; ObsID 15332). Wereprocessed the data to create event files with updatedcalibration modifications using the ciao v4.6 pipeline,following standard procedures.We determined the centroid position of the AGN in the

Chandra hard energy band of 2–8 keV using the wavde-tect tool within ciao with the threshold parameter setto 1⇥ 10�7. We detected three sources within the central2000-radius of the galaxy in this energy band (see Figure1). The brightest source was detected at position of RA= 3:44:31.83, and Dec. = �44:38:41.22, with errors of0.0017 and 0.0011, respectively. This is consistent with the2MASS and Gemini/T-ReCS (see Section 2.4) positionsof the nucleus within ⇠100. Therefore, we adopted thisChandra position as the AGN position.Source counts were extracted using the specextract

task in ciao from a circular region of 2000-radius cen-tered on the detected position of the AGN to matchthe NuSTAR extraction region. The background wasextracted from an o↵set, source-free 5000-radius circularregion. The total net count rate within the 2000-radiusextraction region in the 0.5–8 keV band is 5.69 ⇥ 10�3

counts s�1. The net count rate measured bywavdetectfor the AGN is 1.39 ⇥ 10�3 counts s�1 in the 0.5–8 keVband. The two other sources detected within the extrac-tion region are located to the north-east (NE) and north-west (NW) of the AGN. They do not have counterpartsat other wavelengths, and are likely to be X-ray binarieswithin NGC 1448 (see Section 3.2.1). These sources have0.5–8 keV count rates of 6.67 ⇥ 10�4 counts s�1 and 8.61⇥ 10�4 counts s�1, for the NE and NW sources, respec-

Chandra 2-8 keV

TReCS 12um

Gandhi et al. (2014) local bona fide CTAGN

AGN

20

Case Study: NGC 1448 – Chandra & NuSTAR Observations


Unveiling the buried nucleus in NGC 1448 with NuSTAR 3

Figure 1. Chandra images of NGC 1448 in the 0.5–3 keV and 3–8 keV bands (top panel) and NuSTAR FPMA+B images in the 3–8keV, 8–24 keV and 24–40 keV bands (bottom panel). The color scale for Chandra and NuSTAR images are shown with magenta andred representing the lowest and highest counts in each image, respectively. The black circle marks a 2000-radius region centered on theChandra position of the AGN that was used to extract the X-ray spectra. Images are smoothed with a Gaussian function of radius 5pixels, corresponding to 2.4700 and 12.300 for Chandra and NuSTAR, respectively. North is up and east is to the left in all images. The twoo↵-nuclear X-ray sources detected within the extraction region in the Chandra image are at the north-east and north-west of the AGN,labeled as NE and NW, respectively.

operating at E & 10 keV. These characteristics makeNuSTAR the ideal instrument to characterize the spec-tral shape of heavily obscured AGNs in the local universe(e.g., Balokovic et al. 2014; Puccetti et al. 2014; Baueret al. 2015; Annuar et al. 2015; Gandhi et al. 2016).NGC 1448 was observed by NuSTAR in 2015 (2015-07-

12; ObsID 60101101002) with an e↵ective exposure timeof 58.9 ks (60.3 ks on-source time) for each FPM. Thesource was observed as part of our program to study acomplete, volume-limited (D < 15 Mpc), MIR selectedAGN sample from Goulding & Alexander (2009), to formthe most complete census of the CTAGN population andthe NH distribution of AGN in the local universe.3

We processed the NuSTAR data of NGC 1448 with theNuSTAR Data Analysis Software (nustardas) v1.4.1within heasoft v6.15.1 with CALDB v20150316. Cal-ibrated and cleaned event files were produced using thenupipeline v0.4.3 script with standard filter flags. Spec-tra and response files were extracted using the nuprod-ucts v0.2.5 task.The AGN is detected in both of the NuSTAR FPMs.

We show the combined FPMA+B images of the AGN inthe 3–8, 8–24, and 24–40 keV bands in Figure 1. We ex-tracted the NuSTAR spectrum of NGC 1448 from each

3 The results of the first source in the sample observed by NuS-TAR as part of this program, NGC 5643, was reported in Annuaret al. (2015).

FPM using a circular aperture region of 2000-radius (cor-responding to ⇠30% NuSTAR encircled energy fraction,ECF) centered on the Chandra position of the AGN (seeSection 2.2). The aperture size was chosen to minimizecontamination from o↵-nuclear sources observed in theChandra data. The background photons were collectedfrom an annulus region centered on the AGN with in-ner and outer radii of 4000 and 7000, respectively. Weco-added the spectrum from each FPM using the addas-caspec script to increase the overall SNR of the data.Significant counts are detected up to ⇠40 keV, and thenet count rate measured from this combined spectrum is2.79 ⇥ 10�3 counts s�1 in the 3–40 keV band.We note that in the 24–40 keV band image, where we

expect the AGN to completely dominate, the peak emis-sion appears to be o↵set from the center of the extractionregion. The o↵set is not observed in the 3–8 and 8–24keV band images where NuSTAR is more sensitive. Per-forming our spectral fits up to only 24 keV gave consis-tent results with that obtained by the 0.5–40 keV spectralfits. We therefore attribute this o↵set due to NuSTARstatistical uncertainty due to lower SNR at this higherenergy band. We note that centering the NuSTAR ex-traction region according to this o↵set, or enlarging theextraction region to account for this apparent o↵set alsodo not significantly a↵ect our final results on the analysisof the AGN in NGC 1448.

21


Case Study: NGC 1448 - X-ray Broadband Spectral Fitting Results



Figure 4. Best-fitting models to the combined NuSTAR and Chandra data of NGC 1448 - Model T (top) and Model M (bottom). Colorscheme: black (NuSTAR FPMA+B), red (Chandra). Plots on the left show the model components fitted to the data (dotted lines), withthe total model shown in solid lines. We included an apec component to model the emission at the softest energies, and two cutoffplcomponents to model the two o↵-nuclear sources located within the extraction region in all models. The iron line modeled in Model T islabeled as “Fe K↵”, and the direct, scattered and line components of Model M are labeled as mytz, myts and mytl, respectively. The toppanels of the left plots show the data and unfolded model in E2FE units, while the bottom panels show the fit residuals in terms of sigmawith error bars of size one. Plots on the right show the observed (dashed lines) and intrinsic spectra (solid line) of the AGN component foreach model. The slight o↵set between the red and black lines are due to the cross-calibration uncertainties between Chandra and NuSTAR(Madsen et al. 2015). These plots show that even at E � 10 keV, the spectra that we observed for CTAGNs are still significantly suppressed(up to ⇠2 orders of magnitude for the case of NGC 1448), demonstrating the extreme of CT absorption.

Table 1

X-ray spectral fitting results for NGC 1448.

Component Parameter Units Model T Model M(1) (2) (3) (4) (5)

apec kT keV 0.64+0.15�0.18 0.64+0.15

�0.18

Absorber/Reflector NH(eq) 1024 cm�2 4.7+u�2.0 7.0+u

�3.8

NH(los) 1024 cm�2 4.7+u�2.0 6.6+u

�4.0

✓inc deg 87f 80.5+5.5�17.9

✓tor deg 47.4+32.1�u 60f

AGN Continuum �hard 1.9f 1.9f

L0.5�2,obs 1039 erg s�1 0.2 0.2L2�10,obs 1039 erg s�1 0.9 0.9L10�40,obs 1039 erg s�1 11.0 11.6L0.5�2,int 1041 erg s�1 0.3 0.9L2�10,int 1041 erg s�1 0.4 1.2L10�40,int 1041 erg s�1 0.4 1.2

�2r /d.o.f. 0.99/18 0.98/18

Note. — (1) Model component; (2) parameter associated with each component; (3) units of each parameter; (4) best-fitting parametersfor Model T (torus model by Brightman & Nandra 2011); (5) best-fitting parameters for Model M (MYTorus model by Murphy & Yaqoob2009). “f” is fixed parameter and “u” is unconstrained parameter. Details of each model are described in Section 3.


Figure 4. Best-fitting models to the combined NuSTAR and Chandra data of NGC 1448 - Model T (top) and Model M (bottom). Colorscheme: black (NuSTAR FPMA+B), red (Chandra). Plots on the left show the model components fitted to the data (dotted lines), withthe total model shown in solid lines. We included an apec component to model the emission at the softest energies, and two cutoffplcomponents to model the two o↵-nuclear sources located within the extraction region in all models. The iron line modeled in Model T islabeled as “Fe K↵”, and the direct, scattered and line components of Model M are labeled as mytz, myts and mytl, respectively. The toppanels of the left plots show the data and unfolded model in E2FE units, while the bottom panels show the fit residuals in terms of sigmawith error bars of size one. Plots on the right show the observed (dashed lines) and intrinsic spectra (solid line) of the AGN component foreach model. The slight o↵set between the red and black lines are due to the cross-calibration uncertainties between Chandra and NuSTAR(Madsen et al. 2015). These plots show that even at E � 10 keV, the spectra that we observed for CTAGNs are still significantly suppressed(up to ⇠2 orders of magnitude for the case of NGC 1448), demonstrating the extreme of CT absorption.

Table 1

X-ray spectral fitting results for NGC 1448.

Component Parameter Units Model T Model M(1) (2) (3) (4) (5)

apec kT keV 0.64+0.15�0.18 0.64+0.15

�0.18

Absorber/Reflector NH(eq) 1024 cm�2 4.7+u�2.0 7.0+u

�3.8

NH(los) 1024 cm�2 4.7+u�2.0 6.6+u

�4.0

✓inc deg 87f 80.5+5.5�17.9

✓tor deg 47.4+32.1�u 60f

AGN Continuum �hard 1.9f 1.9f

L0.5�2,obs 1039 erg s�1 0.2 0.2L2�10,obs 1039 erg s�1 0.9 0.9L10�40,obs 1039 erg s�1 11.0 11.6L0.5�2,int 1041 erg s�1 0.3 0.9L2�10,int 1041 erg s�1 0.4 1.2L10�40,int 1041 erg s�1 0.4 1.2

�2r /d.o.f. 0.99/18 0.98/18

Note. — (1) Model component; (2) parameter associated with each component; (3) units of each parameter; (4) best-fitting parametersfor Model T (torus model by Brightman & Nandra 2011); (5) best-fitting parameters for Model M (MYTorus model by Murphy & Yaqoob2009). “f” is fixed parameter and “u” is unconstrained parameter. Details of each model are described in Section 3.


MYTorus Model (Murphy & Yaqoob 09)

NH ≥ 3 × 1024 cm-2 (CT!) Γ = 1.9 (fixed) L2-10,observed = 0.9 × 1039 erg s-1 L2-10,intrinsic = (0.4 - 1.2) × 1041 erg s-1

NuSTAR 3-8 keV

NuSTAR 8-24 keV

Chandra 2-8 keV Chandra 6-8 keV

November 2012; texp ~ 30ks December 2012; texp ~ 20ks August 2015; texp ~ 10ks

NuSTAR Observation of NGC 660

– 32 –

DECL

INAT

ION

(J20

00)

RIGHT ASCENSION (J2000)01 24 51 50 49 48 47 46 45

09 33 00

32 45

30

15

00

31 45

0.0 0.5 1.0 1.5 2.0

DECL

INAT

ION

(J20

00)

RIGHT ASCENSION (J2000)02 41 50 48 46 44 42 40

00 27 15

00

26 45

30

15

00

0.0 0.5 1.0 1.5 2.0

DECL

INAT

ION

(J20

00)

RIGHT ASCENSION (J2000)01 43 02.50 02.45 02.40 02.35 02.30 02.25 02.20 02.15 02.10

13 38 48

47

46

45

44

43

42

DECL

INAT

ION

(J20

00)

RIGHT ASCENSION (J2000)01 43 03.2 03.0 02.8 02.6 02.4 02.2 02.0 01.8 01.6 01.4

13 38 54

52

50

48

46

44

42

40

38

36

Fig. 2.— As in Figure 1. (2a) NGC524 (2 ′ ′. 66 × 2 ′ ′. 47), (2b) NGC1055 (3 ′ ′. 45 × 2 ′ ′. 57) (2c)

NGC660 (0 ′ ′. 21 × 0 ′ ′. 21), and (2d) NGC660 (2 ′ ′. 54 × 2 ′ ′. 19).

New activity in NGC 660 1083

Baseline Array (VLBA) observations taken in 2001 (BF068;5.0 GHz) and 2010 (BC191; 8.4 GHz) have also been examined.The 5-GHz 2001 VLBA data cover a total of 1h23m split into twoobservations, separated by four hours, using four 8-MHz sub-bandseach split into 16 channels. The 8.4-GHz 2010 data consist of twoobservations of eight minutes each, separated by 96 d, each obser-vation was made using eight sub-bands of 16 MHz split into 128channels each. In addition, the VLA A-array 1986 15 GHz datafrom Carral et al. (1990) have also been extracted and analysed.

Four separate X-ray observations from the Chandra archive wereused, taken in 2001 January, 2003 February, and 2012 Decemberand November (Obs IDs 1633, 4010, 15333 and 15587). The dataconsist of a total of ∼52 ks of exposure time, ∼7 ks before the radiooutburst and ∼45 ks after. All of these data were obtained using theAdvanced CCD Imaging Spectrometer (ACIS-S). The data wereprocessed using CIAO v4.5, with the most recent calibration files(Fruscione et al. 2006). Spectra covering 0.1-10 keV were extractedusing a circle of radius 6 arcsec centred on the location of the radionucleus, but avoiding the point source to the west of the nucleus (seeSection 3.2). Background spectra were extracted using an annulussurrounding the source extraction region, with an outer radius of25 arcsec and an inner radius of 13 arcsec, avoiding nearby X-raypoint sources.

3 C O N T I N U U M C O M P O N E N T S

3.1 Radio results: a time-line

No central compact radio source was detected within NGC 660in either archival MERLIN observations from 1998 (to a 3σ limitof 0.3 mJy beam−1, Fig. 1, left), or VLBA observations taken in2001. The archival VLBA observations in 2010 September showthat a single compact source (beam size 2 × 1 mas) was presentat the centre of the galaxy at 8.4 GHz by late 2010. The peak fluxdensity rises from 18.3 ± 0.9 mJy beam−1 on September 16 to36.0 ± 1.8 mJy beam−1 on 2010 December 21.

The two e-MERLIN continuum data sets from mid-2013 bothshow a strong compact source at the same position as the 2010VLBA detection, unresolved in both frequency bands (150 mas at1.4 GHz, 50 mas at 5 GHz). In the 2013 e-MERLIN data, the inte-grated flux density in the centre of the 5-GHz band is 364 ± 18 mJy.Comparing this with the MERLIN pre-outburst limit results ina factor of >1200 change in brightness. At the centre of the e-MERLIN band observed at 1.4-GHz, the integrated flux density is198 ± 9.9 mJy, giving a fairly flat overall spectral index of α = 0.5,where S ∝ να .

The most recent observation, the 2013 October EVN data (withan angular resolution of 26 × 20 mas), shows an obvious jet-likefeature to the north-east of the central brightest source (Fig. 2, grey-scale). When the EVN data are imaged with uniform weighting,giving greater resolution (19 × 6 mas) at the expense of increasednoise, there also appears to be a weaker feature to the west (Fig. 2,contours). The high-resolution image shows a compact central ob-ject with an integrated flux density of 69.1 ± 3.5 mJy. Despitehaving greater angular resolution, the 2010 VLBA data show nosign of the structures seen in the EVN data taken three years later,only the central brightest source. This could be because the objectis evolving spatially in time, or simply due to the lack of sensitivityand poor u − v coverage of the earlier VLBA snapshot observations.

Between e-MERLIN and EVN scales there is a significant de-crease in the flux detected. Summing the fitted components in theEVN model gives a total flux density of ∼105 ± 5 mJy, while the

Figure 2. Continuum image of the new source in NGC 660 showing thejet-like components. The ‘low’ resolution (natural weighting; 26 × 20 mas)image is shown in grey-scale, with contours from the ‘high’ resolution(uniform weighting; 19 × 6 mas) image overlaid. The numerals correspondto those of the spatial fit parameters listed in Table 1. The data are contouredat (−1, 1, 2, 4, 8, 16, 32, 64) × 1.736 mJy beam−1, the grey-scale range is−1.26 to 66.49 mJy beam−1.

Table 1. Results of two-component (top) and three-component (bot-tom) fits to the naturally weighted and uniform continuum images,respectively. Labels correspond to those in Fig. 2. Positions are rel-ative to 01h43m 13◦38′, and phase referenced to J0143+1215 (RA= 01h43m31.s092221 Dec. =12◦15′42.′′93343; J2000) which has a cata-logued positional uncertainty of ±1.02 mas in RA and 0.78 mas in Dec.Brightness temperatures are calculated using the beam major axis andare lower limits only.

RA Dec. Peak Int. TB(J2000) (J2000) (mJy beam−1) (mJy) (× 107 K)

1 02.319 44.9033 75.4 ± 3.8 80.0 ± 4.0 >7.22 02.320 44.9130 26.3 ± 1.3 25.6 ± 1.3 >2.3

1 02.319 44.9028 62.8 ± 3.1 69.1 ± 3.5 >11.62 02.320 44.9127 24.9 ± 1.2 27.7 ± 1.4 >4.63 02.319 44.9068 10.1 ± 0.5 10.6 ± 0.5 >1.8

e-MERLIN flux density measured in the sub-band closest to theEVN measurement is 196 ± 10 mJy, almost twice that detected bythe EVN. This large difference in flux is likely due to a combinationof the two arrays not being sensitive to the same spatial scales, andthe source possibly fading as it evolves in the five months betweenthe observations.

Table 1 shows the results of two-dimensional Gaussian fits to theEVN continuum images. The two-component fit was carried out onthe naturally weighted image, while the three-component fit is forthe higher resolution uniform-weighted image. If component 2 is, asit appears to be, moving, then we can estimate limits on its velocity.Assuming that the event occurred between 2008.0 (Minchin et al.2013) and 2010.7 (epoch of the first of the VLBA detections), then

MNRAS 452, 1081–1088 (2015)

at University of D

urham on A

ugust 4, 2016http://m

nras.oxfordjournals.org/D

ownloaded from

VLA 8.4 GHz (0.21 x 0.21 arcsec2)

Filho et al. (2002)

Radio Outburst: Argo et al. (2015)

EVN 1.4 GHz (26 x 20 mas2)

August 2015

Annuar et al. in prep.

NuSTAR 3-8 keV

NH = 0.6 [+0.5,-0.3] × 1024 cm-2

(heavily obscured/near CT)

NuSTAR Observation of NGC 3486 & NGC 5195

NH < 2 x 1022 cm-‐2

(Unobscured?)

XMM-‐Newton NuSTAR

Annuar et al. in prep.

NH ~ 1 x 1021 cm-‐2

(Unobscured)

XMM-‐Newton + Chandra

NuSTAR




CTAGN Candidates





NGC 0613 No No 23.6 No NGC 4051 No No 23.3 No NGC 6300 No No 23.3 No NGC 5128 No No 23.0 No NGC 4565 No ?* 21.4 No NGC 5033 No No < 20.9 No NGC 5643 CT CT ? CT NGC 1448 ? CT ? CT? † NGC 0660 CT CT* ? CT? NGC 3486 No ? ? CT? ‡

NGC 3627 CT CT ? CT? NGC 5195 No CT* ? ? NGC 3621 No CT* ? ? NGC 3628 No ? ? ? NGC 1792 ? No ? ?

ESO 121-G6 ? ? ? ? CT % 30% 45% 20% 25-45%




NGC 0613 No No 23.6 No NGC 4051 No No 23.3 No NGC 6300 No No 23.3 No NGC 5128 No No 23.0 No NGC 4565 No ?* 21.4 No NGC 5033 No No < 20.9 No NGC 5643 CT CT 24.7 CT NGC 1448 ? CT 24.7 CT NGC 0660 CT CT* 23.8 No NGC 3486 No ? < 22.3 No

NGC 3627 CT CT ? CT? NGC 5195 No CT* 21.0 No NGC 3621 No CT* ? ? NGC 3628 No ? ? ? NGC 1792 ? No ? ?

ESO 121-G6 ? ? ? ?

CT % 30% 45% 30% 30-35%


80% complete…

Post-NuSTAR








ESO 121-G6 ? ? ? ?

CT % 30% 45% 30% 30-35%


80% complete…

Post-NuSTAR



4 Ricci et al.

Ueda et al. (2014) argue that assuming a strength of theCompton hump produced by the disk of Rdisk = 0.25or Rdisk = 1 would change the best estimate of fCTby as much as 50%. The significantly higher fractionof CT AGN predicted at low fluxes by the model ofUeda et al. (2014) (Fig. 2; i.e., a factor of∼ 3 at F10−40 =10−15 erg cm−2 s−1 with respect to Treister et al. 2009) isrelated to the increase in the fraction of obscuration athigher redshifts considered by the authors.In Figure 2 we illustrate the fraction of CT sources

predicted by different synthesis models of the CXB as afunction of the 10–40keV flux limit. The figure shows thevalues of fCT obtained by our work, by Alexander et al.(2013) and Civano et al. (2015) using NuSTAR, and byTueller et al. (2008) for the 9-months Swift/BAT cata-log. The Swift/BAT 70 months survey has a flux limitof ∼ 10−11 erg s−1 cm−2 in the 14–195keV energy band,which corresponds to 4.3× 10−12 erg s−1 cm−2 in the 10–40 keV band (for a power-law emission with a photonindex of Γ = 1.8). The observed value of fCT we find isin good agreement with that predicted, for the flux limitof the 70-months Swift/BAT survey, by Treister et al.(2009) and Ueda et al. (2014), and with the two modelsof Akylas et al. (2012) that consider an intrinsic fractionof CT AGN of 15% and 25%. In agreement with theresults of Tueller et al. (2008), we find that the modelof Draper & Ballantyne (2010) and of Gilli et al. (2007)clearly overestimate (by a factor of ∼ 2) the fractionof CT AGN for the flux-limit we probe in the 10–40keVband. The value of fCT obtained by Civano et al. (2015)combining NuSTAR detections in the 3–8, 8–24 and 3–24keV band is larger than the value predicted by the mod-els consistent with Swift/BAT measurements. This couldbe related to the large uncertainties associated with theestimation of NH from hardness ratios.

4. THE INTRINSIC COLUMN DENSITY DISTRIBUTION

Due to the significant effect of Compton scattering forNH > 1024 cm−2 even hard X-ray selected samples canbe biased against CT AGN (see Fig. 1). In particularonly a few objects with logNH ! 24.5 are detected bySwift/BAT. In these reflection-dominated AGN the pri-mary X-ray emission is almost completely depleted andthey are observed only through their reflection compo-nent. The effect of this observational bias is clearly il-lustrated in Fig. 3, which shows how the observed valueof fCT inferred from our sample changes with the intrin-sic flux and the distance. Within 20Mpc the fraction ofCT AGN is fCT = 32 ± 11%, while this value clearlydecreases with increasing distance, and is below 10% atD ! 80Mpc.To derive the intrinsic NH distribution of AGN one

must carefully correct the observed distribution (bottompanel of Fig. 4) for selection biases. Besides absorption,the reflection components from the torus and accretiondisk also affect the selection efficiency of AGN at hard X-rays. We follow the same analysis as in Ueda et al. (2003,2014) to constrain the “NH function” [f(LXi, zi;NHi)],which represents the probability distribution function ofline-of-sight column density of an AGN. Since it is ex-tremely difficult to constrain the number of AGN withlogNH > 25, the NH function is normalized to unityin the range between logNH = 20–24 (completely un-absorbed AGN are arbitrarily assigned logNH = 20.0).

Figure 4. Top panel: NH function of our hard X-ray selectedAGN sample (normalised to unity in the logNH = 20–24 range)for a torus with an half-opening angle of θOA = 60◦. Centralpanel: same as top panel for a torus with an half-opening angle ofθOA = 35◦. Bottom panel: observed column density distribution(normalised to unity in the logNH = 20–24 range). The plotsshow the values for 14–195 keV luminosities in the logL 14−195 =40 − 43.7 and logL 14−195 = 43.7 − 46 range. Objects with littleor no absorption were assigned logNH = 20.

Thanks to the large sample size, we do not assume anyfunctional shape for the NH function, but treat the valuesin discrete bins of logNH as independent, free parame-ters. We perform a maximum-likelihood fit of the ab-sorption function using the likelihood estimator definedby Ueda et al. (2014):

L′ = −2!

lnf(LXi, zi;NHi)A(NHi,Γi, LXi, zi)"

f(LXi, zi;NHi)A(NHi,Γi, LXi, zi)d logNH

(1)where i represents each object of the sample, and A is thesurvey area (from Baumgartner et al. 2013) per countrate expected from a source with column density NH, in-

Ricci et al. (2016)

4 Ricci et al.

Ueda et al. (2014) argue that assuming a strength of theCompton hump produced by the disk of Rdisk = 0.25or Rdisk = 1 would change the best estimate of fCTby as much as 50%. The significantly higher fractionof CT AGN predicted at low fluxes by the model ofUeda et al. (2014) (Fig. 2; i.e., a factor of∼ 3 at F10−40 =10−15 erg cm−2 s−1 with respect to Treister et al. 2009) isrelated to the increase in the fraction of obscuration athigher redshifts considered by the authors.In Figure 2 we illustrate the fraction of CT sources

predicted by different synthesis models of the CXB as afunction of the 10–40keV flux limit. The figure shows thevalues of fCT obtained by our work, by Alexander et al.(2013) and Civano et al. (2015) using NuSTAR, and byTueller et al. (2008) for the 9-months Swift/BAT cata-log. The Swift/BAT 70 months survey has a flux limitof ∼ 10−11 erg s−1 cm−2 in the 14–195keV energy band,which corresponds to 4.3× 10−12 erg s−1 cm−2 in the 10–40 keV band (for a power-law emission with a photonindex of Γ = 1.8). The observed value of fCT we find isin good agreement with that predicted, for the flux limitof the 70-months Swift/BAT survey, by Treister et al.(2009) and Ueda et al. (2014), and with the two modelsof Akylas et al. (2012) that consider an intrinsic fractionof CT AGN of 15% and 25%. In agreement with theresults of Tueller et al. (2008), we find that the modelof Draper & Ballantyne (2010) and of Gilli et al. (2007)clearly overestimate (by a factor of ∼ 2) the fractionof CT AGN for the flux-limit we probe in the 10–40keVband. The value of fCT obtained by Civano et al. (2015)combining NuSTAR detections in the 3–8, 8–24 and 3–24keV band is larger than the value predicted by the mod-els consistent with Swift/BAT measurements. This couldbe related to the large uncertainties associated with theestimation of NH from hardness ratios.

4. THE INTRINSIC COLUMN DENSITY DISTRIBUTION

Due to the significant effect of Compton scattering forNH > 1024 cm−2 even hard X-ray selected samples canbe biased against CT AGN (see Fig. 1). In particularonly a few objects with logNH ! 24.5 are detected bySwift/BAT. In these reflection-dominated AGN the pri-mary X-ray emission is almost completely depleted andthey are observed only through their reflection compo-nent. The effect of this observational bias is clearly il-lustrated in Fig. 3, which shows how the observed valueof fCT inferred from our sample changes with the intrin-sic flux and the distance. Within 20Mpc the fraction ofCT AGN is fCT = 32 ± 11%, while this value clearlydecreases with increasing distance, and is below 10% atD ! 80Mpc.To derive the intrinsic NH distribution of AGN one

must carefully correct the observed distribution (bottompanel of Fig. 4) for selection biases. Besides absorption,the reflection components from the torus and accretiondisk also affect the selection efficiency of AGN at hard X-rays. We follow the same analysis as in Ueda et al. (2003,2014) to constrain the “NH function” [f(LXi, zi;NHi)],which represents the probability distribution function ofline-of-sight column density of an AGN. Since it is ex-tremely difficult to constrain the number of AGN withlogNH > 25, the NH function is normalized to unityin the range between logNH = 20–24 (completely un-absorbed AGN are arbitrarily assigned logNH = 20.0).

Figure 4. Top panel: NH function of our hard X-ray selectedAGN sample (normalised to unity in the logNH = 20–24 range)for a torus with an half-opening angle of θOA = 60◦. Centralpanel: same as top panel for a torus with an half-opening angle ofθOA = 35◦. Bottom panel: observed column density distribution(normalised to unity in the logNH = 20–24 range). The plotsshow the values for 14–195 keV luminosities in the logL 14−195 =40 − 43.7 and logL 14−195 = 43.7 − 46 range. Objects with littleor no absorption were assigned logNH = 20.

Thanks to the large sample size, we do not assume anyfunctional shape for the NH function, but treat the valuesin discrete bins of logNH as independent, free parame-ters. We perform a maximum-likelihood fit of the ab-sorption function using the likelihood estimator definedby Ueda et al. (2014):

L′ = −2!

lnf(LXi, zi;NHi)A(NHi,Γi, LXi, zi)"

f(LXi, zi;NHi)A(NHi,Γi, LXi, zi)d logNH

(1)where i represents each object of the sample, and A is thesurvey area (from Baumgartner et al. 2013) per countrate expected from a source with column density NH, in-






ESO 121-G6 ? ? ? ?

CT % 30% 45% 30% 30-35%


80% complete…

Post-NuSTAR



•  Sample: Mid-IR selected AGN within 15 Mpc. •  Used multiwavelength techniques to identify CTAGN

candidates. •  Observed these candidates with NuSTAR. •  30-35% are CT (could be as high as 55% accounting for

those that we still lack data). •  CT fraction found is similar (potentially higher) to CT population found by X-ray-selected and optically-selected AGN sample. (~30%; Ricci+16; Maiolino+98).

SUMMARY

80% complete…


ady annuar - dartmouth collegehiddenmonsters/talks/annuar.pdfmotivations… 2 ctagn contributes...

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