hwr bhagn

Information about hwr bhagn

Published on November 28, 2007

Author: Danior

Source: authorstream.com

Content

Black Holes:  Black Holes Black Holes and Galaxy Centers :  Black Holes and Galaxy Centers Two most important energy production mechanisms in astrophysics: nuclear fusion (e.g. stars) Efusion ~ 0.007 mc² gravitational accretion onto “deep potential wells” such as white dwarfs, neutron stars & black holes requires conversion of: potential energy  thermal energy  radiation Eaccretion ~ e mc2/2 with e: efficiency for black holes Accretion onto black holes could be the most efficient energy production mechanism, IF black holes are abundant! Do Black Holes Exist? A brief History:  Do Black Holes Exist? A brief History Late 60‘s: Zeldovich, Lynden-Bell, Salpeter and others considered that QSOs (“Quasi-stellar Objects”) have “sustained” luminosities of ~1046 ergs/sec flux variability (at short wavelengths) at tvar ~ hours  rflux ~ tvar · c  luminosity equal to a whole galaxy from a region the size of the solar system  accretion onto BH only sustainable and viable energy production mechanism To sustain accretion, Fradiation < -Fgrav on electrons (“Eddington limit”):  LQSO  MBH x 107 - 109 Msun  “Super-massive black holes” (SMBH) How to detect a black hole?:  How to detect a black hole? A. Criteria demonstrate the existence of an event horizon “relativistically deep” potential well gravitational redshift of light Doppler boosting, transverse Doppler effect, etc. show relativistic (v  0.1 c) material motion exclude alternative explanations e.g. lower limit on dynamical mass + upper limit on emitted radiation  astrophysical “mass-to-light-ratio” limit from considering alternatives: clusters of neutron stars clusters of planets, etc. must be stable for t ~ tuniverse ~ 1010 years Slide5:  1. Fe - K lines (X-ray spectroscopy) for few objects (~ 6.5 keV) emission from very hot plasma line widths and line shapes match expectations for material orbiting v  0.3 c in a few cases last stable orbit implies SMBH of high spin B. Methods Two separate issues: qualitative proof existence and estimate/measurement of masses (and spin) Observed Ka Lines:  Observed Ka Lines X-ray observations of galaxy centers: we see gas move at relativistic speeds  close to last stable orbit Relativistic Jets in AGNs Require Black Holes:  Relativistic Jets in AGNs Require Black Holes Broad Optical/UV Emission Lines in Active Galactic Nuclei:  Broad Optical/UV Emission Lines in Active Galactic Nuclei Measuring Black Hole Masses:  Measuring Black Hole Masses Example 1: NGC4258 the nucleus of the nearby spiral galaxy shows several spots of H2O maser emission (Myashi etal 1995) Velocities and positions fit a Keplerian disk perfectly  r > 5x1012Msun/pc3 NGC4258 (cntd.):  NGC4258 (cntd.) Example 2: the Galactic Center:  Example 2: the Galactic Center Genzel, Eckardt,Schoedel et al. 1990- Ghez et al 1995 – At the geometric center of the Milky Ways inner stellar mass distribution lies the radio source SgrA* Is it a black hole? Method: at only 10kpc distance, we can watch stars move Stellar Motions in the G.C.:  Stellar Motions in the G.C. Stellar distribution in the G.C. Black Holes in Nearby Nuclei:  Black Holes in Nearby Nuclei Example 3: M32 (van der Marel, de Zeeuw & Rix, 1997) Compare predicted stellar kinematics with HST data MBH~3x106MSun Census of Nearby Black Holes:  Census of Nearby Black Holes Employing “broad brush” methods: Whenever a “non-luminous”, compact mass excess (“MDO”) in galaxy centers could be studied, an SMBH is the only viable explanation.  attempt census of MDO‘s and identify with MBH HST with its superior resolution has been pivotal in such studies e.g. Gebhardt et al 2002 Questions: Do all galaxies have black holes at their centers? Do big (i.e. massive) black holes live in big galaxies? MBH and Host Galaxy Properties:  MBH and Host Galaxy Properties Magorrian et al. 1998: claimed that more luminous galaxies have more massive black hole measurements. [all their BH measurements were spurious, though] Ferrarese & Merrit, 2000; Gebhardt et al 2000: MBH ~ s*n MBH can be predicted from the velocity dispersion at 1kpc No good physical explanation, yet. MBH vs Mstars and Concentration:  MBH vs Mstars and Concentration The black hole mass seems to correlate well with many global properties of the galaxy’s bulge (not disk!!) E.g. Haering & Rix 2003: MBH vs Mstars M-s relation is an easy way to measure MBH from s Mean density of BH today r(BH)  5105 M / Mpc3 Measuring Black Holes in High-Redshift Galaxies:  Measuring Black Holes in High-Redshift Galaxies Reverberation mapping: Measure light-travel time between accretion disk at the very center (continuum) Broad line region Measure velocity width of broad lines MBH~s2BLRxR/G Netzer, Peterson, Maoz, Kaspi and others Reverberation Mapping of QSOs:  Reverberation Mapping of QSOs QSO Spectra Reverberation Mapping of QSOs:  Reverberation Mapping of QSOs How Early Did Massive Black Holes Exist?:  How Early Did Massive Black Holes Exist? Pentericci et al 2001 Very Luminous QSOs exist at z>6! “Eddington Limit”: Gravitational force inward > Radiation Force Outward  MBH > 109 MSun 0.6 Gyrs after the Big Bang Questions: How did massive Black Holes get to the to galaxy centers in the first place? How did they grow in mass? Black Hole Growth:  Black Hole Growth Increase in total mass (integrated over all black holes): Accretion onto the black hole Individual mass increase: Accretion or Merging QSO Luminosity Function and BH Growth:  QSO Luminosity Function and BH Growth QSO luminosity function varies widely as a function of z Are present day black holes the result of luminous accretion in QSO phases? Black Hole Merging:  Black Hole Merging BH’s sit at the centers of every (most) (proto-)galaxy Early galaxies (and their halos) merge What happens to the black holes at their centers? Step 1: Black holes in central cusps sink to the center via dynamical friction, until i.e. the BH’s dominate the mass in the center Step 3: Black holes spiral in, emitting gravitational radiation Step 2: ahang-up > 100 agrav.rad !! How to get from 1 to 3 ?? Black Hole Merging in a Cosmological Context :  Black Hole Merging in a Cosmological Context Volonteri et al. 2003: Start with MBH~200 MSun in every sub-halo Follow merging tree can get 108MSun by now But: it is hard to get 109 by z~6 Question: what was the initial black hole mass? Initial Black Holes:  Initial Black Holes Possible Key: Very first generation of stars (Pop III) No metals  no cooling  gas clouds stay hotter  Jeans mass is higher (where fragmentation sets in)  first stars very massive Possible masses 200 MSun 106 MSun(?) Bromm etal 1999,2003, Abell et al 2000 Formation of 105 MSun star at z~30 (Bromm and Loeb 2003) Overall Census:  Overall Census All galaxies with bulges seem to have black holes The black hole mass correlates tightly with the overall mass and dynamics of the host bulge Averaging over the galaxy population in the present day universe, the mean black hole density is <rBH>~5x105MSun/Mpc3 (Yu & Tremaine 2003)  BH growth and bulge formation are connected E.g. both happen during mergers with gas inflow Black holes grow through (luminous) accretion were all galaxies QSOs sometime in the past? How important is the merging of BH’s during the merging of their galaxies? Not clear yet!

Related presentations


Other presentations created by Danior

The 1950s
25. 12. 2007
0 views

The 1950s

18 electro magnetism
12. 11. 2007
0 views

18 electro magnetism

NAAR ROME EN FLORENCE
31. 10. 2007
0 views

NAAR ROME EN FLORENCE

OPERA intro FAM nov05
01. 11. 2007
0 views

OPERA intro FAM nov05

cruise powerpoint
06. 11. 2007
0 views

cruise powerpoint

Tanks
08. 11. 2007
0 views

Tanks

SIGIR04
20. 11. 2007
0 views

SIGIR04

Chapter 7 Leading Effectively
14. 12. 2007
0 views

Chapter 7 Leading Effectively

Harriet Tubman
17. 12. 2007
0 views

Harriet Tubman

5BAD
02. 01. 2008
0 views

5BAD

NC CERT Disaster Preparation
03. 01. 2008
0 views

NC CERT Disaster Preparation

VDSL
03. 01. 2008
0 views

VDSL

ImpactTerror
04. 01. 2008
0 views

ImpactTerror

Sirker
07. 01. 2008
0 views

Sirker

VHS for Dec 5 2006 Meeting
07. 01. 2008
0 views

VHS for Dec 5 2006 Meeting

Korea mar05
30. 10. 2007
0 views

Korea mar05

Ellerbroek AFOSR PRET
15. 11. 2007
0 views

Ellerbroek AFOSR PRET

dokuchaev
01. 12. 2007
0 views

dokuchaev

dogclark
16. 11. 2007
0 views

dogclark

Lect15SocialRela
30. 12. 2007
0 views

Lect15SocialRela

Tue1720 157bis
30. 10. 2007
0 views

Tue1720 157bis

AFMCPTeachingModel 10 8
06. 12. 2007
0 views

AFMCPTeachingModel 10 8

DC Air Natl Guard RR brief
20. 02. 2008
0 views

DC Air Natl Guard RR brief

ballroom
24. 02. 2008
0 views

ballroom

Tas Talk
27. 02. 2008
0 views

Tas Talk

week2
30. 10. 2007
0 views

week2

R Miller WTTC Stockholm
27. 03. 2008
0 views

R Miller WTTC Stockholm

HPB Expo 2008Webinar
11. 12. 2007
0 views

HPB Expo 2008Webinar

Merwe pres
06. 11. 2007
0 views

Merwe pres

ciullapp
14. 11. 2007
0 views

ciullapp

bondiv 05 30 07
19. 11. 2007
0 views

bondiv 05 30 07

olga russia
26. 10. 2007
0 views

olga russia

Fiszelson cover ru
26. 10. 2007
0 views

Fiszelson cover ru

Steve Beslity and Jo
07. 11. 2007
0 views

Steve Beslity and Jo

Henk van Leeuwen 2007
05. 11. 2007
0 views

Henk van Leeuwen 2007

globalization tang text
24. 12. 2007
0 views

globalization tang text

Murshed
30. 12. 2007
0 views

Murshed