Identifying distant* hidden monsters with NuSTAR

Identifying distant* hidden monsters with NuSTAR * z ~ 0.05 1 log (L X / erg s -1 ) ~ 43 45 George Lansbury Durham University with David Alexander, James Aird, Daniel Stern, Poshak Gandhi, the NuSTAR science team

The cosmic X-ray background (XB) peaks at hard X-ray (>10keV) energies XB intensity [kev 2 cm -2 s -1 kev -1 Str -1 ] 100 10 1 log N H < 22 22 < log N H < 23 23 < log N H < 24 ompton-thick (log N H > 24) All ompton-thin All AGN Galaxies Total Swift/XRT Swift/BAT Luminosity Density of X-ray selected AGNs (split by N H ) Aird+15 1 10 100 Energy [kev] Buchner+15 A large fraction (most?) of the cosmic growth of supermassive black holes occurs during a phase of luminous, heavily obscured accretion: a hidden monster phase (e.g., Fabian 1999; Gilli+2007; Treister+2009, Buchner+2015)

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 1 10 E [kev] unobscured log (N H / cm -2 ) = 20 log (N H / cm -2 ) = 21

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 1 10 E [kev] obscured log (N H / cm -2 ) = 22 log (N H / cm -2 ) = 23

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 1 10 E [kev] ompton-thick log (N H / cm -2 ) = 24 log (N H / cm -2 ) 25

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 handra and XMM 1 10 E [kev]

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 Hard X-ray (> 10 kev) coverage important, especially at z < 1 handra and XMM NuSTAR 1 10 E [kev]

EFE Flux [photons cm 2 s 1 kev 1 ] 10 3 10 2 10 1 10 0 Hard X-ray (> 10 kev) coverage important, especially at z < 1 handra and XMM NuSTAR 1 10 E [kev] NuSTAR (3-78 kev): + first focusing mission at > 10keV + 100 higher sensitivity.. + 10 higher angular resolution.. than previous > 10 kev missions

Identifying distant hidden monsters with NuSTAR- In this talk:

Identifying distant hidden monsters with NuSTAR- In this talk: i. SAMPLE 1: SDSS-selected Type 2 quasars - pre-select candidate hidden monsters from large area survey (SDSS) - target with NuSTAR observations - how extreme are they? - does NuSTAR change our interpretation? Technique: Optical ( [OIII] ) line selection + hard X-ray observation Lansbury+2014, Gandhi+2014, Lansbury+2015

Identifying distant hidden monsters with NuSTAR- In this talk: i. SAMPLE 1: SDSS-selected Type 2 quasars ii. - pre-select candidate hidden monsters from large area survey (SDSS) - target with NuSTAR observations - how extreme are they? - does NuSTAR change our interpretation? SAMPLE 2: NuSTAR serendipitous survey - unbiased hard X-ray (>10keV) sample - do we identify any extreme systems like the above? Technique: Optical ( [OIII] ) line selection + hard X-ray observation Lansbury+2014, Gandhi+2014, Lansbury+2015 Technique: Hard X-ray selection + observation Lansbury+ in prep.

Identifying distant hidden monsters with NuSTAR- In this talk: i. SAMPLE 1: SDSS-selected Type 2 quasars ii. - pre-select candidate hidden monsters from large area survey (SDSS) - target with NuSTAR observations - how extreme are they? - does NuSTAR change our interpretation? SAMPLE 2: NuSTAR serendipitous survey - unbiased hard X-ray (>10keV) sample - do we identify any extreme systems like the above? iii. omparing the different techniques: - Optical selection versus hard X-ray selection Technique: Optical ( [OIII] ) line selection + hard X-ray observation Lansbury+2014, Gandhi+2014, Lansbury+2015 Technique: Hard X-ray selection + observation Lansbury+ in prep.

Technique: Optical ( [OIII] ) line selection + hard X-ray observation i. SAMPLE 1: SDSS-selected Type 2 quasars - pre-select candidate hidden monsters from large area survey (SDSS) - target with NuSTAR observations - how extreme are they? - does NuSTAR change our interpretation? References: Lansbury et al. 2014 (ApJ...785...17L) Gandhi, Lansbury et al. 2014 (ApJ...792..117G) Lansbury et al. 2015 (ApJ...809..115L)

SDSS selected Type 2 quasars Initial sample = Reyes+2008 = 887 Type 2 quasars selected from the SDSS based on: + z < 0.83 + L [OIII] > 10 8.3 L + AGN emission line ratios + Narrow permitted lines (Hα, Hβ) ß i.e. Type 2 example SDSS spectrum for Type 2 quasar (SDSS J1218)

SDSS selected Type 2 quasars Initial sample = Reyes+2008 = 887 Type 2 quasars selected from the SDSS based on: + z < 0.83 [OIII] traces intrinsic AGN luminosity + L [OIII] > 10 8.3 L relatively unbiased against obscuration effects + AGN emission line ratios + Narrow permitted lines (Hα, Hβ) ß i.e. Type 2 example SDSS spectrum for Type 2 quasar (SDSS J1218)

SDSS selected Type 2 quasars: selection of NuSTAR targets Reyes+2008 sample 887 SDSS Type 2 quasars (Reyes+08) 10 10 L[OIII] [Lsolar] 10 9 10 8 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 z

SDSS selected Type 2 quasars: selection of NuSTAR targets Reyes+2008 sample Direct X-ray sample 887 SDSS Type 2 quasars (Reyes+08) L[OIII] [Lsolar] 10 10 10 9 70 have X-ray coverage with handra/xmm (e.g., Jia+13) 10 8 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 z

SDSS selected Type 2 quasars: selection of NuSTAR targets Reyes+2008 sample Direct X-ray sample 887 SDSS Type 2 quasars (Reyes+08) L[OIII] [Lsolar] 10 10 10 9 70 have X-ray coverage with handra/xmm absorption (N H ) distribution: Data from: Vignali+2006,2010 Jia+2013, LaMassa+2014 10 8 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 z Where s the ompton-thick AGNs?

SDSS selected Type 2 quasars: selection of NuSTAR targets L[OIII] [Lsolar] 10 10 10 9 10 8 Reyes+2008 sample Direct X-ray sample This sample 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 z 887 SDSS Type 2 quasars (Reyes+08) 70 have X-ray coverage with handra/xmm This work: 9 candidate ompton-thick objects targeted with NuSTAR: (Oct 2012 Sep 2014) + z < 0.5 + L [OIII] > 2.5 10 8 L + low L X /L [OIII] (i.e., likely ompton-thick)

SDSS selected Type 2 quasars: NuSTAR image cutouts NuSTAR 8-24 kev images for the 9 targets: + NuSTAR exposure times: 20 ksec 50 ksec per source 3.5 arcmin

SDSS selected Type 2 quasars: NuSTAR image cutouts NuSTAR 8-24 kev images for the 9 targets: + NuSTAR exposure times: 20 ksec 50 ksec per source 3.5 arcmin + Five statistically significant detections (all non-detections in 104 month Swift BAT maps) + Three with enough photons for (relatively) detailed modelling + Two with X-ray band ratio constraints

z = 0.051! XMM Broad-band X-ray spectra + Reflection-dominated continua + High absorption (N H 10 24 cm -2 ) + High intrinsic X-ray luminosities (L X 10 44 erg s -1 ) kev 2 [photons cm 2 s 1 kev 1 ] 10 3 10 4 10 5 10 3 10 4 10 5 10 6 10 7 SDSS J1218+4706 Model M APE XMM z = 0.094! MYTS MYTL MYTZ POW kev 2 [photons cm 2 s 1 kev 1 ] 10 3 10 4 10 5 10 6 10 4 10 5 10 6 10 7 SDSS J1243-0232 ZWABS POW handra z = 0.281! NuSTAR 10 8 1 10 Energy [kev] 10 8 Energy [kev] 10

Intrinsic 2-10keV LX [erg X-ray s 1 ] luminosity NuSTAR essential to reliably measure intrinsic properties like N H and L X 10 46 10 45 10 44 10 43 10 42 10 41 NuSTAR constraints SDSS J0011+0056 SDSS J1034+6001 SDSS J1218+4706 SDSS J1243-0232 SDSS J1713+5729 10 20 10 21 10 22 10 23 10 24 10 25 N H [cm 2 ] = pre-nustar constraints N H [cm -2 ] N 20 15 10 5 0 N H distribution for z < 0.5 Type 2 quasars: 0011+0056 1034+6001 1218+4706 1243-0232 1713+5729 20 21 22 23 24 20 21 22 23 24 log ( N H / cm 2 ) + Higher NH and LX measured with the addition of NuSTAR data than with handra / XMM alone + Implied ompton-thick fraction for z < 0.5 Type 2 quasars of f TK 36 % (cf., Ueda+2014 require f TK 33 62 % for AGNs in order to reproduce the XB peak intensity) T T T T T T T T T T T T T T T T handra / XMM Have identified hidden monsters in the optically selected Type 2 quasar population T T T T T T T T NuSTAR-informed

ii. SAMPLE 2: NuSTAR serendipitous survey - unbiased hard X-ray (>10keV) sample Technique: Hard X-ray selection + observation - do we identify any extreme systems like the above NuSTAR-observed SDSS Type 2 quasars? Reference: Lansbury et al. in prep.

The NuSTAR serendipitous survey 15 0 30 45 60 75 0 30 60 90 120 150 = dedicated surveys (e.g., EDFS, OSMOS) = serendipitous survey fields 40-month survey status: 0 sources 1 2 sources 3 7 sources 8 sources (RA, Dec) [] t exp [ks] 10 100 1000 # NuSTAR fields incorporated = 331 umulative exposure time = 20 Ms Areal coverage 13 deg 2 Lansbury et al. serendipitous survey catalog paper to be submitted soon # detected sources = 497 (276 with spec-z s) Similar sensitivity to the dedicated NuSTAR surveys in well-studied fields ( EDFS, OSMOS, EGS, UDS, & GOODS-N; see next talk by A. Del Moro )

NuSTAR serendipitous survey: L X z plane comparison with Swift BAT 10 46 Swift BAT NuSTAR Serendipitous L10 40keV [erg s 1 ] 10 45 10 44 10 43 L (z) 10 42 10 41 0.01 0.1 1.0 Redshift (z)

Very hard objects in the NuSTAR serendipitous survey 3.5 NuSTAR Band Ratio (8-24keV / 3-8keV) 3.0 2.5 2.0 1.5 1.0 0.5 ompton Thick (Balokovic+16) Moderate absorption (N H = 10 23 cm -2 ) 0.0 0.5 1.0 1.5 2.0 Redshift (z)

Very hard objects in the NuSTAR serendipitous survey 3.5 SDSS QSO2s (L15) NuSTAR Band Ratio (8-24keV / 3-8keV) 3.0 2.5 2.0 1.5 1.0 0.5 ompton thick Moderate absorption (N H = 10 23 cm -2 ) 0.0 0.5 1.0 1.5 2.0 Redshift (z)

Very hard objects in the NuSTAR serendipitous survey NuSTAR Band Ratio (8-24keV / 3-8keV) 3.5 3.0 2.5 2.0 1.5 1.0 ompton thick NuSTAR serendip SDSS QSO2s (L15) 0.5 0.0 0.5 1.0 1.5 2.0 Redshift (z)

Very hard objects in the NuSTAR serendipitous survey NuSTAR Band Ratio (8-24keV / 3-8keV) 3.5 3.0 2.5 2.0 1.5 1.0 J1506 J0505 J1410 J1512 J1534 ompton thick J0823 J1653 J0315 J0433 NuSTAR serendip SDSS QSO2s (L15) J1444 10 very hard objects all detected in the hard NuSTAR band (8-24 kev), but typically undetected in the soft NuSTAR band (3-8 kev). 0.5 0.0 0.5 1.0 1.5 2.0 Redshift (z)

Very hard objects in the NuSTAR serendipitous survey: X-ray image cutouts NuSTAR 8-24 kev cutouts J1506 J0505 J1410 J1512 J1534 J0823 J1653 J0315 J0433 J1444 handra / XMM / Swift-XRT 0.5-10 kev cutouts

Very hard objects in the NuSTAR serendipitous survey: Broad-band X-ray spectra NuSTAR plus handra / XMM / Swift-XRT spectra: 10 3 J1506 z =0.034 J0505 z =0.036 J1410 z =0.067 J1512 z =0.069 J1534 z =0.160 10 4 kev 2 [cm 2 s 1 kev 1 ] 10 5 10 6 10 3 J0823 z =0.313 10 4 10 5 10 6 1 10 J1653 z =0.354 1 10 J0315 z =0.679 1 10 Energy [kev] J0433 z =0.866 1 10 J1444 z =1.539 1 10 + Mixture of robust ompton-thick AGN ( ), likely ompton-thick AGN ( ), highly absorbed ompton-thin AGN, and indeterminates + Many would not have been identified as high absorption systems based on the < 10 kev data alone

Very hard objects in the NuSTAR serendipitous survey: Broad-band X-ray spectra NuSTAR plus handra / XMM / Swift-XRT spectra: 10 3 J1506 z =0.034 J0505 z =0.036 J1410 z =0.067 J1512 z =0.069 J1534 z =0.160 10 4 kev 2 [cm 2 s 1 kev 1 ] 10 5 10 6 10 3 J0823 z =0.313 10 4 10 5 10 6 1 10 J1653 z =0.354 1 10 J0315 z =0.679 1 10 Energy [kev] J0433 z =0.866 1 10 J1444 z =1.539 1 10 Have identified hidden monsters in the (relatively) distant hard X-ray selected population See also ivano+15 for a robust ompton-thick AGN in NuSTAR-OSMOS

iii. omparing the different techniques: Optical selection versus hard X-ray selection

log 10-40keV log X-ray L 10 40 kev Luminosity [erg s 1 ] [erg s -1 ] 46 45 44 43 42 41 L X versus L MIR for the extreme Type 2 quasars (SAMPLE 1): 1243 1218 0011 1034 0840 1713 0758 0056 1157 SDSS QSO2s (L15) Alexander + 2013 Del Moro + 2014 Stern + 2014 ivano + 2015 43 44 45 46 47 log L 6 µm [erg s 1 ] log 6µm MIR Luminosity [erg s -1 ] andidate deeply buried AGNs, unlikely to be selected in NuSTAR surveys (but X-ray upper limits still important!!) An impressive example: SDSS1157 one of the brightest/most powerful of the 887 Reyes+08 QSO2s (both in terms of [OIII] and MIR luminosities), yet undetected at hard X-ray energies with NuSTAR

log 10-40keV log X-ray L 10 40 kev Luminosity [erg s 1 ] [erg s -1 ] 46 45 44 43 42 41 L X versus L MIR for the extreme Type 2 quasars (SAMPLE 1): 1243 1218 0011 1034 0840 1713 0758 0056 1157 SDSS QSO2s (L15) Alexander + 2013 Del Moro + 2014 Stern + 2014 ivano + 2015 43 44 45 46 47 log L 6 µm [erg s 1 ] log 6µm MIR Luminosity [erg s -1 ] WISE HotDOGs Stern+15 andidate deeply buried AGNs, unlikely to be selected in NuSTAR surveys (but X-ray upper limits still important!!) An impressive example: SDSS1157 one of the brightest/most powerful of the 887 Reyes+08 QSO2s (both in terms of [OIII] and MIR luminosities), yet undetected at hard X-ray energies with NuSTAR

Many of the extreme NuSTAR survey AGNs would be missed by optical selections. SAMPLE 1 (SDSS QSO2s) optical spectra: SAMPLE 2 (NuSTAR ser) optical spectra: + Many high S/N lines in all cases + Generally fewer & weaker lines + 2 sources with undetected [OIII]

Optically selected Hard X-ray identified Most of the hidden monster AGNs would be identified by an individual one of the techniques, but not by both.

Summary For targetted SDSS Type 2 quasars, adding NuSTAR data reveals obscuration and luminosities which are an order of magnitude higher than suggested by <10keV X-ray data alone. The NuSTAR serendipitous survey (~500 objects at present) has uncovered some extreme sources, akin to the ompton-thick SDSS Type 2 quasars above. There are deeply buried optically (SDSS-) selected AGNs which wouldn t be selected by NuSTAR. The converse is also true: some extreme NuSTAR AGNs wouldn t necessarily be selected in the optical.

The End

omparing the two techniques: optical versus hard X-ray selection ompton-thick fractions for Type 2 objects at z < 0.5 and matched in luminosity (43.7 < log L X < 45.1): SDSS-selected Type 2 quasars: f T 36 % NuSTAR serendipitous survey: f T = 14 (+29-13) %