The Correlation Between the Hard-X-ray Photon Index and the Accretion Rate in AGN: Probing Black-Hole Growth Across Cosmic Time

Transcription

1 The Correlation Between the Hard-X-ray Photon Index and the Accretion Rate in AGN: Probing Black-Hole Growth Across Cosmic Time Ohad Shemmer Pennsylvania State University Collaborators: Niel Brandt (Penn State), Hagai Netzer (Tel Aviv U.), Roberto Maiolino (INAF-Roma), and Shai Kaspi (Tel Aviv U.)

2 Outline 1. The hard-x-ray spectrum of AGN 2. Determining the black-hole mass and accretion rate in AGN 3. A line width - accretion rate degeneracy in nearby AGN 4. The hard-x-ray photon index as an accretion-rate indicator 5. Using X-rays to probe the history of black-hole growth 6. Summary, ongoing work, implications

3 1. The Hard-X-ray Spectrum of AGN

4 1. The Hard-X-ray Spectrum of AGN > 2 kev N(E) E Γ

5 1. The Hard-X-ray Spectrum of AGN > 2 kev N(E) E Γ Typical Γ range for radio-quiet AGN: Γ 2.0±0.5

6 1. The Hard-X-ray Spectrum of AGN 2.5 2! Piconcelli et al. (2005) Chartas et al. (2002) Vignali et al. (2001) Shemmer et al. (2005) Shemmer et al. (2006) z M B e.g. Vignali+03, 05; Shemmer+05, 06 No clear dependence of Γ on either luminosity or redshift.

7 1. The Hard-X-ray Spectrum of AGN Brandt+97 (Γ) However... Γ - FWHM(Hβ) anticorrelation

8 1. The Hard-X-ray Spectrum of AGN Brandt+97 (Γ) However... Γ - FWHM(Hβ) anticorrelation Analogous to the anticorrelation between the soft-x-ray spectral slope and the Hβ width. (e.g. Boller+96; Laor+97)

9 2. Determining the BH Mass & Accretion Rate in AGN R BLR is measured by reverberation ( light-echo ) mapping R BLR = c 1 (λl λ ) α Assuming Keplerian motion: M BH R BLR v 2 R BLR [light-days] Sy 1 galaxy PG quasar Kaspi+00, 05 M BH = c 2 (λl λ ) α FWHM !L! (5100Å) [erg s -1 ]

10 2. Determining the BH Mass & Accretion Rate in AGN Two observables determine M BH and the Eddington ratio: 1. Luminosity 2. Line width [ ] 0.7 [ ] 2 M BH = νlν (5100 Å) FWHM(Hβ) ergs s km s 1 M [ ] 0.3 [ νlν (5100 Å) FWHM(Hβ) L/L Edd = 0.15f(L) ergs s km s 1 (L L bol ; f(l) 5 15) Kaspi+00; Marconi+04; Shemmer+06, ApJ, 646, L29 ] 2

11 3. A Line Width - Accretion Rate Degeneracy " (XMM) $L $ (5100Å) < ergs s -1 NLS1 1.5 (a) (b) FWHM(H!) [km s -1 ] L / L Edd [#L 0.3 FWHM(H!) -2 ] e.g. Lu & Yu 99; Porquet+04; Wang+04; Piconcelli+05; Kelly 07 Obscured 8 AGN Across Cosmic Time, Seeon, Bavaria, Germany, June 8, 2007

12 3. A Line Width - Accretion Rate Degeneracy " (XMM) $L $ (5100Å) < ergs s -1 NLS1 1.5 (a) (b) FWHM(H!) [km s -1 ] L / L Edd [#L 0.3 FWHM(H!) -2 ] e.g. Lu & Yu 99; Porquet+04; Wang+04; Piconcelli+05; Kelly 07 Obscured 8 AGN Across Cosmic Time, Seeon, Bavaria, Germany, June 8, 2007

13 3. A Line Width - Accretion Rate Degeneracy " (XMM) $L $ (5100Å) < ergs s -1 NLS1 1.5 (a) (b) FWHM(H!) [km s -1 ] L / L Edd [#L 0.3 FWHM(H!) -2 ] e.g. Lu & Yu 99; Porquet+04; Wang+04; Piconcelli+05; Kelly 07 Breaking the degeneracy requires Γ and FWHM(Hβ) measurements in luminous, radio-quiet AGN (at high redshift). Obscured 8 AGN Across Cosmic Time, Seeon, Bavaria, Germany, June 8, 2007

14 3. A Line Width - Accretion Rate Degeneracy XMM-Newton Spectroscopy of Luminous, High-Accretion Rate Quasars

15 4. The hard-x-ray photon index as an accretion-rate indicator (XMM) " $L $ (5100Å) < ergs s -1 NLS1 1.5 (a) FWHM(H!) [km s -1 ] (b) L / L Edd [#L 0.3 FWHM(H!) -2 ] Shemmer+06, ApJ, 646, L29; Shemmer+07, in prep. Obscured 10 AGN Across Cosmic Time, Seeon, Bavaria, Germany, June 8, 2007

16 4. The hard-x-ray photon index as an accretion-rate indicator " (XMM) $L $ (5100Å) < ergs s -1 NLS1 $L $ (5100Å) > ergs s (a) FWHM(H!) [km s -1 ] (b) L / L Edd [#L 0.3 FWHM(H!) -2 ] Shemmer+06, ApJ, 646, L29; Shemmer+07, in prep. Γ values for luminous radio-quiet AGN, while consistent with those expected from their accretion rates, are higher than expected from the width of their Hβ lines. Obscured 11 AGN Across Cosmic Time, Seeon, Bavaria, Germany, June 8, 2007

17 5. Using X-rays to Probe the History of BH Growth L/LEdd - Γ correlation 0.0 Shemmer+07, in prep. log (L / L Edd ) !L! (5100Å) < ergs s -1 NLS1!L! (5100Å) > ergs s -1 BCES FITEXY # log (L / L Edd ) log(l/l Edd ) = (1.6 ± 0.3)Γ (3.8 ± 0.7) 12 " BCES

18 5. Using X-rays to Probe the History of BH Growth 28 X-ray flux - optical flux relation log L! (2 kev) log L! (2 kev) = (0.721±0.011) log L! (2500 Å) + (4.531±0.688) αox = log(f 2 kev/f ) 2500 Å log(ν2 kev/ν ) 2500 Å " ox Strateva+05; Steffen+06; Just+07 " ox = (0.137±0.008) log L! (2500 Å) + (2.638±0.240) log L! (2500 Å)

19 5. Using X-rays to Probe the History of BH Growth Γ The X-ray Method Lx L/LEdd νlν (2500Å) νlν(5100å) MBH M BH = [ νlν (5100 Å) ergs s 1 ] 0.7 [ ] 2 FWHM(Hβ) 10 3 km s 1 M L/L Edd = 0.15f(L) [ νlν (5100 Å) ergs s 1 ] 0.3 [ FWHM(Hβ) 10 3 km s 1 ] 2

20 5. Using X-rays to Probe the History of BH Growth Applying the X-ray method CDF-N CDF-S

21 5. Using X-rays to Probe the History of BH Growth CDFs (Saez et al. 2007, submitted) Netzer et al. (2007, submitted) Kollmeier et al. (2006) N log L / L Edd

22 5. Using X-rays to Probe the History of BH Growth CDFs (Saez et al. 2007, submitted) Netzer et al. (2007, submitted) Kollmeier et al. (2006) N log L / L Edd

23 5. Using X-rays to Probe the History of BH Growth 6 z>2 1<z<2 z<1 CDFs Type 1 sources - L/LEdd evolution? N Did high-z SMBHs have enough time to form at their current rate? log L / L Edd - Did some SMBHs experience faster growth in the past? - At what z have they grown much faster?

24 5. Using X-rays to Probe the History of BH Growth 2.5 2! Piconcelli et al. (2005) Chartas et al. (2002) Vignali et al. (2001) Shemmer et al. (2005) Shemmer et al. (2006) M B z Next: L/LEdd and MBH determinations at the highest redshift.

25 6. Summary, Ongoing Work, Implications Γ is strongly correlated with L/LEdd in radio-quiet AGN across three orders of magnitude in luminosity. Γ and Lx may be used as L/LEdd and MBH indicators. Implications for accretion-disk/corona models and the history of black-hole growth in the universe. Strengthening the Γ- L/LEdd correlation requires a large inventory of FWHM(Hβ) and Γ data for luminous, radio-quiet AGN.This involves: 1. Accurate Γ measurements with XMM-Newton/Chandra. 2. FWHM(Hβ) measurements from near-ir spectroscopy. Reducing the scatter on the Γ- L/LEdd correlation requires (near) simultaneous X-ray and optical observations.

26 6. Summary, Ongoing Work, Implications Advantages of the X-ray method : Measuring the slope of the X-ray power-law spectrum vs. detailed optical/near-ir spectroscopy. Imaging (many sources) vs. spectroscopy (individual sources). No redshift restriction vs. near-ir atmospheric bands. Relatively easy determinations of L/LEdd and MBH for faint and/or distant type 1 AGN. Perhaps the only way to determine L/LEdd and MBH for type 2/obscured AGN.