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Living alongside Monsters: Matter around Central Massive Black Holes Q. Daniel Wang University of Massachusetts Issues to be addressed • Why galactic nuclear regions? Why M31 and our GC? • Activities of the SMBHs – Quiescent accretion flow vs. flare – Relation to the ambient gas and stellar properties • How did nuclear stellar clusters (NCs) form? • What is the star formation (SF) mode? – in clusters and/or small groups – in burst or continuous fashion • How do massive stars interact with the ISM? • How do activities in nuclear regions affect galaxy ecosystem? Galactic nuclear regions play a key role in galaxy formation and evolution • Every galaxy probably contains a SMBH and/or a nuclear stellar cluster. • Their masses are correlated. • How these correlations are achieved is not clear. • SMBHs accrete gas in two modes : – Quasars: radiating ~10% of the rest-mass energy – Local SMBHs: radiatively inefficient • But SMBHs can also grow by mergers Graham & Spitler 2009 Little is known about the interplay among stars, the ISM, and SMBHs Lopsided stellar disks: relics of SMBH accretion in quasar mode? Dry mergers destroy such disks, as in massive spheroids Hopkins & Quataert 2010 M31: Double stellar nuclei and SMBH P1 P2 (M31*) HST view of the M31 center (Lauer et al. 1998) • A red star cluster forming a lopsided disk (Tremaine 1995) • Mbh ~ 1.4 x 108 Msun • Apparent young (A-type) stars (t ~ 200 Myr) around the SMBH • Alternatively, they may be post-HB stars formed from stripped redgiants and/or stellar mergers (e.g., Demargue & Virani 2007). M31*: Chandra view • 40 HRC observations and 58 ACIS observations taken from late 1999 to early 2010 • Sources associated with P1, SSS and S1 are probably Xray binaries • P2 – M31* • Lx ~ 10-5 Lbondi • Lbondi ~ 3 x1041 (η/0.1)erg s-1, η - radiation efficiency Li, Z. et al. (2010) A major outburst seen on Jan. 6, 2006 M31* brightened by ~102 After the outburst, M31* remained active with the mean flux ~ 7x quiescent one 10-yr Chandra light curve An outburst A quiescent state An active state What’s happening… • The outburst is similar in relative amplitude to the Xray flares detected in Sgr A*. • Both phenomena may be caused by episodic ejection of relativistic plasma blobs (“jets”) – analogous to coronal mass ejection in the Sun. • Activities after the outburst, Empirical and theoretical may also due to many small predictions for the outbursts/ejection events. mechanical feedback - up to a few % of Lbondi SMBH feedback: a major heating source of the nuclear region? HST/WFPC2 Hα Image Large [NII]/Hα ~ 1.3-2.7, similar to LINERS, cannot be explained purely by photo ionization. Heating by low-energy cosmic-ray from the SMBH feedback may be responsible. Li & Wang 2009 Dense stellar pop. dynamic formation of X-ray binary Radial X-ray source number density distribution in the M31 bulge With 1’ radius: • Lx > 1036 erg/s: an enhanced number density dynamic formation of LMXB Voss & Gilfanov 2007 • But in 1036 > Lx > 1035: a deficit destruction of loosely bound LMXB? • A normal Sx/Sk ratio toward the center indicates little effect on the CV pop. Nuclear stellar feedback: driving hot gas outflow • Stellar contribution (including CVs and coronally active binaries) subtracted • characteristics of hot gas in the bulge: • z0 ~ 600 pc; • T~ 0.3 keV; • L0.5-2 keV ~ 3×1038 erg/s Diffuse soft X-ray emission IRAC 8 micro, K-band, 0.5-2 keV Hydro-simulation of SNRs, bulge wind, nuclear disk, and SMBH accretion • Full box size =4 kpc • Adaptive mesh refinement down to 0.5 pc (FLASH code) • A cool gas inflow is assumed to continuously feed the nuclear disk around the SMBH. • Injection of Ia SN (4x10-4 / yr), and stellar mass loss follows the stellar light. • The injection drives a bulge wind and also reduces the accretion to the SMBH. • The disk is being evaporated mass loading to the hot gas. Density cut 800 pc Tang et al. 2009 ~ 1055 erg, or > 104 SNe is needed over the past 2 x 107 years! ROSAT Survey (1.5-keV Band) Chandra deep survey of the Galactic center Red: 1-2.5 keV Green: 2.5-4 keV Blue: 4-9 keV X-ray close-up: the Galactic nuclear region Bridge X-ray reverberation of a Sgr A* burst ~ 200 years ago Ponti et al. 2010 A Panoramic HST Infrared View of the Galactic Center 1.87 and 1.90 μm narrow bands: on and off Pα line; Wang et al. 2009 1.9 µm band detection limit • 0.6 million stars • Accounting for > 80% light • Including all stars with M > 10 M and evolved lower mass ones. • A high-res database for stellar pop., dist., and formation Pα + stellar continuum: Preliminary Results • Ionized gas features resolved into arrays of organized linear filaments strong local magnetic fields. • ~200 stars show enhanced Pα emission (green dots). • ~2/3 of them are located outside the three known clusters. • 13 have been followed up spectroscopically, confirming that they are indeed massive stars a new population of massive stars. Sickle HII Region Detailed structure of ionized gas pillars sculpted by the intense radiation and wind from the Quintuplet cluster. But magnetic field may also play a critical role. Red: radio continuum Green: Pα Blue: 1.9µm Detailed views of individual compact HII regions Nuclear Spiral/Torus Sgr A* • Ionized gas around the supermassive black hole is confined to a spiral embedded in a circumnuclear dusty torus. • Evidence for ionized gas outflows from this torus. Red: 8µm (IRAC) Green: Pα Blue: 1.9µm X-ray Flare from Sgr A* • Mbh ~ 3 x 106 M • Peak L(2-10 keV) ∼1035 erg s-1 • Lasted for about 3 hrs • Variability ~ a few minutes Baganoff et al. (2003) Spectra of extended X-rayemitting features Sgr A* PWN IRS 13 Diffuse The spectra of Sgr A*, IRS 13, and diffuse X-ray emission all show the Fe K line at ~6.6 keV NEI emission from gas heated recently (net~103 cm-3 yr). Nuclear cluster and extinction mapping NICMOS image: Red: H, Green: 1.9 Blue: K Extinction map from SED fits for individual stars Spitzer/IRAC 4.5 µm Intensity Map IRAC 4.5/3.6 µm Intensity Map Extinction contour overlaid on the HST 1.9 µm image Great Observatory Survey of the GC Summery • An unprecedented high-resolution infrared panorama of the Galactic center. Initial results: – a new population of very massive stars in relative isolation and with strong winds. – Fine filamentary structures of ionized diffuse gas indicating profound influence of local strong magnetic field. – Compact nebulae, tracing various stages of massive star evolution – Construction of a high-res extinction map toward the GC. – Evidence for a SF burst ~ a few 108 yrs ago, in addition to continuum SF over the life time of the Galaxy. Summary Cont. • X-ray flare and flux variation are detected from M31*, a scaled-up version of Sgr A* activities. • Cool gas in the nuclear regions of M31 and our GC both has a small filling factor and are embedded in hot gas. • Evaporation of cool gas by hot gas may lead to the starvation of SMBHs • The mass-loaded hot gas undergoes outflows, affecting the global ecosystem of the galaxies. • We aim to understand the formation modes of massive stars and their interplay with the extreme environment in galactic nuclei. CMZ T ≤107 K Filling factor? Composition? Physical properties? Heating and cooling? Mass loading? Corona Galactic disk Magnetic loops Galactic Center: Environment • Strong absorption from NIR to soft X-ray • Strong scattering and dispersion of low frequency radio wave • Large amounts of molecular gas (~ 107 Msun) – But small filling factor (< 10%) • Very active in star formation – Close to 10% of the SF in the Galaxy – SN rate ~ 1 per 103 yrs 1041 ergs/s • Short orbital period (~ a few x 106 yr) – Large tidal and shear forces • Very high B field (up to ~ 1 mG) – Toroidal B field in dense clouds – Poloidal B field in intercloud gas • Very hard diffuse X-ray emission – Much harder than spectra of SNRs HST/NICMOS 1.90µm Map of the Galactic Center l Foreground dusty clouds Quintuplet cluster b 15’ (115 light-year) Arches cluster Sgr A* 39’ (300 light-year) • Distance to the Galactic center: 26,000 light-year • Resolution: 0.025 light-year (0.2”) • 144 HST orbits, taken between Feb and June, 2008 144X4X4=2304 images for each of the two wavelength filters HST/NICMOS 1.87µm Map of the Galactic Center Arched HII filaments Arches cluster Sickle HII region Quintuplet cluster Sgr A* • The 1.9µm filter is sensitive to the stellar continuum emission. • The 1.87µm filter covers the Pα line. • Subtracting the 1.9µm map from the 1.87µm map adaptively. A net Pα line emission map (see the poster by Dong et al.; 415.01) . Net Pα Map of the Galactic Center Why do we need the HST? • Excellent imaging stability • Only observable from the space • Little background due to the Earth’s warm atmosphere Living alongside Monsters: Matter around Central Massive Black Holes Q. Daniel Wang University of Massachusetts But most of SMBHs are not active in nearby galaxies. They are starved. Why? • Little gas falls into the galaxy center? • Or the infalling gas is being removed, due to episodic AGN feedback or some continuous processes? Answering these questions will help to understand the formation of SMBHs and galaxies in general. Outline • Review of nuclear regions in M31 and our Galactic center • key components • interesting unique phenomena • their interplay • What need to be done? M31 (d=780 kpc) IRAC 8 micro 0.5-2 keV 2-8 keV Li & Wang 2007