UNCOVERING HIDDEN BLACK HOLES: OBSCURED AGN AND THEIR RELATIONSHIP TO THE HOST GALAXY by Stephanie M. LaMassa A dissertation submitted to The Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy. Baltimore, Maryland July, 2011 Abstract Active Galactic Nuclei (AGN) are accreting supermassive black holes at the centers of galaxies. According to the unified model, this accretion disk is surrounded by an obscuring torus of dust and gas. In Type 2, or obscured, AGN this torus is viewed 24 edge on. When the column density of the torus exceeds 1/σt = 1.5×10 cm−2, this obscuring medium becomes Compton-thick. Studies indicate that a significant fraction of Compton-thick Type 2 AGN exist but are under-represented in many current samples. We have studied two samples of local type 2 AGN (Seyfert 2 galaxies) to explore issues relevant to finding and characterizing the Compton-thick population. We have also investigated the relationship between type 2 AGN and the galaxies in which they live. To find this Compton-thick population, selecting samples of AGN based on their inherent flux is necessary. We undertook an empirical approach in identifying the most reliable intrinsic AGN flux proxies. Using infrared spectroscopy from Spitzer, optical spectra from the Sloan Digital Sky Survey (SDSS) and the literature, and radio and hard X-ray (E > 10 keV) data from the literature, we demonstrated that ii the [OIV] 26µm, [OIII] 5007A˚ and MIR continuum fluxes agree the best among Type 1 and Type 2 Seyfert galaxies. Utilizing 2-10 keV X-ray data from Chandra and XMM-Newton, we probed the amount of obscuration that may be present in these systems. We find that a major- ity of sources exhibit signatures of heavy, and possibly Compton-thick, obscuration: depressed 2-10 keV X-ray emission when normalized by intrinsic AGN flux and large Fe Kα equivalent widths, Using a sample of ∼250 star forming galaxies, ∼50 composite systems and an additional ∼20 Seyfert 2 galaxies, we examined the connection between AGN activ- ity and star formation. We found that the SDSS derived star formation rates and [NeII] 12.8µm flux accurately probe starburst activity in both quiescent and active galaxies. Using these parameters and diagnostics that accurately trace AGN flux, we have shown that these processes are significantly correlated. This link suggests that supermassive black holes and their host galaxies grow simultaneously in the local universe. Advisors: Professor Timothy Heckman and Dr. Andrew Ptak iii Acknowledgements I would first like to thank my advisors, Tim Heckman and Andy Ptak, for being excellent instructors and a wonderful source of support over the years. They were always available to answer questions and offer advice, sometimes responding to emails at times when most people would be in their 3rd dream and far from being able to discuss and explain scientific matters effectively and intelligently. I also would like to think Profs. Dick Henry, Nina Markovic and Tom Haine for being part of my thesis defense committee. The grad students in this department deserve a huge thanks! There is a real com- munity here that makes going through the trials and tribulations of a PhD program not only bearable, but fun. I have had such a great time my past 5 years here and I realize I’m fortunate to have this experience. A huge thanks to all the friends I’ve made here along the way. I thank my parents for always encouraging my love for science over the years. They were always eager to cultivate this interest by bringing me to planetarium shows, museums and public astronomy lectures; buying me a telescope; enrolling me iv in an astronomy summer program for high school students; sharing popular astronomy articles from the NY Times and other periodicals with me; and understanding that I would only apply to colleges where I could major in astronomy. I thank them for traveling from NY to MD to be here for my thesis defense and to celebrate with me. My amazingly supportive boyfriend, Mark J. Cloherty, CRC, also deserves a very heart-felt thank you. He always believed in my abilities even during rough times when I doubted myself. I thank him for being a great listener and offering sage advice. His sense of humor and rational perspective has been inspirational. Finally, a big thank you to all the professors I’ve had at BU and at JHU, as well as all the scientists I’ve had the pleasure of working with and meeting at the CfA. The enthusiastic support I’ve received over the years has made me feel both welcome and that a place exists for me in the astronomy community. v Contents Abstract ii Acknowledgements iv List of Tables ix List of Figures xii 1 Introduction 1 1.1 AGNIdentification ............................ 2 1.2 X-rayBackground............................. 4 1.3 Co-evolutionofAGNandHostGalaxies . 6 1.4 AreasofExploration ........................... 6 2 Intrinsic AGN Flux Proxies 10 2.1 SampleSelection ............................. 12 2.2 DataAnalysis............................... 13 2.2.1 OpticalData ........................... 13 2.2.2 InfraredData ........................... 13 2.2.3 RadioandHardX-rayData . 16 2.3 Measurements............................... 16 2.3.1 IR Emission Line Fluxes . 16 2.3.2 IRContinuumFluxandPAHs. 17 2.4 Diagnostics of Intrinsic AGN Luminosity . 19 2.4.1 Inter-ComparisonofProxies . 21 2.4.2 ComparisonwithSy1s ...................... 24 2.4.3 LuminosityDependence . 28 2.4.4 Are [OIII] and [OIV] Biased by Star Formation? . 29 2.5 Summary ................................. 31 vi 3 X-ray Observations of Homogeneous Samples of Seyfert 2 Galaxies: Data Reduction 69 3.1 DataReductionOverview ........................ 70 3.1.1 [OIII]Sample ........................... 71 3.1.2 12µmSample ........................... 71 3.2 Fitting Multiple Spectra . 71 3.2.1 12µmSample ........................... 72 3.3 SpectralFitting.............................. 73 3.3.1 [OIII]Sample ........................... 75 3.3.2 12µmSample ........................... 76 3.4 Fe Kα Detection ............................. 79 3.4.1 [OIII]Sample ........................... 79 3.4.2 12µmSample ........................... 80 4 X-ray Observations of Homogeneous Samples of Seyfert 2 Galaxies - Results 114 4.0.3 ObscurationDiagnostics . 115 4.0.4 Implications for the Local AGN Population . 119 4.0.5 InvestigatingObscurationGeometry . 120 4.0.6 Are Compton-Thick Sources Unique? . 122 4.0.7 NuSTAR:DetectionatHigherEnergies . 124 4.1 Summary ................................. 125 5 Connection between AGN Activity and Host Galaxy Star Formation143 5.1 FromStar-formingGalaxiestoAGN . 144 5.1.1 Parametrizing Star Formation Rates: Effects of AGN Activity 145 5.1.2 AGNFluxProxies ........................ 148 5.1.3 ConnectionbetweenAGNandSFR . 150 5.1.4 Relative Importance of AGN to Star Formation Activity . 151 5.1.5 α20−30µm .............................. 153 5.1.6 PAHEWsandFluxRatios . .. .. 153 5.2 Soft X-ray Perspective on Disentangling AGN Activity from Host Galaxy StarFormation .............................. 155 5.2.1 Relationship Between APEC Flux and Multi-wavelength Star FormationRateIndicators . 157 5.2.2 GratingSpectroscopy. 158 5.3 Summary ................................. 159 6 Concluding Remarks 203 6.1 OurStorySoFar ............................. 203 6.2 LookingAheadtotheFuture . 204 vii A Aperture Bias 206 B Starburst Contribution to the MIR 209 C X-ray Analysis Notes on 12µmSources 211 D Simulated NuSTAR Detections: 10-40 keV 223 Bibliography 227 Vita 238 viii List of Tables 2.1 [OIII]Sample ............................... 34 2.2 12µmSample ............................... 35 2.2 12µmSample ............................... 36 2.3 Optical Emission Line Fluxes1 andRatiosfor[OIII]Sample . 37 2.4 Optical Emission Line Fluxes1and Ratios for 12µmSample ...... 38 2.4 Optical Emission Line Fluxes1and Ratios for 12µmSample ...... 39 2.4 Optical Emission Line Fluxes1and Ratios for 12µmSample ...... 40 2.5 Spitzer Observation Summary1 ...................... 41 2.5 Spitzer Observation Summary1 ...................... 42 2.5 Spitzer Observation Summary1 ...................... 43 2.6 MIRFluxandPAHEWvaluesfor[OIII]Sample . 44 2.6 MIRFluxandPAHEWvaluesfor[OIII]Sample . 45 2.7 MIR Flux and PAH EW values for 12µmSample ........... 46 2.7 MIR Flux and PAH EW values for 12µmSample ........... 47 2.7 MIR Flux and PAH EW values for 12µmSample ........... 48 2.8 Diagnostic Ratios: Optical & Infrared . 49 2.8 Diagnostic Ratios: Optical & Infrared . 50 2.9 Diagnostic Ratios: Optical & Infrared vs Radio & X-ray2 ....... 51 2.9 Diagnostic Ratios: Optical & Infrared vs Radio & X-ray2 ....... 52 2.10 Results of Two Sample Tests between Sy1s and Sy2s . 53 2.11 Correlation of Diagnostic Ratios with Eddington Parameters . .. 54 3.1 [OIII] Sample XMM-Newton ObservationLog . 81 3.1 [OIII] Sample XMM-Newton ObservationLog . 82 3.2 12µmSampleX-rayObservationLog . 83 3.2 12µmSampleX-rayObservationLog . 84 3.2 12µmSampleX-rayObservationLog . 85 3.2 12µmSampleX-rayObservationLog . 86 3.3 [OIII] Sample: Parameters for Powerlaw Fits . 87 3.3 [OIII] Sample: Parameters for Powerlaw Fits . 88 3.4 [OIII] Sample: Parameters for Thermal + Powerlaw Fits . 89 ix 3.4 [OIII] Sample: Parameters for Thermal + Powerlaw Fits . 90 3.5 12µm Sample: APEC model parameters (solar abundance) . 91 3.5 12µm Sample: APEC model parameters (solar abundance) . 92 3.5 12µm Sample: APEC model parameters (solar abundance) . 93 3.6 12µm Sample: Power law model parameters . 94 3.7 [OIII] Sample: 2 - 10 X-ray Flux and Luminosity