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The suppression of star formation by

The suppression of star formation by powerful active galactic nuclei 作者： M.J.Page , M.Symeonidis 报告人：倪嘉阳. Introduction.

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The suppression of star formation by

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  1. The suppression of star formation by powerful active galactic nuclei 作者：M.J.Page, M.Symeonidis 报告人：倪嘉阳

  2. Introduction • It is widely suspected that the tight correlation between the mass of the black hole and the mass of stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity • X-rays trace emission from AGN, powerful star-forming galaxies are brightest at infrared and submillimetre wavelengths

  3. Introduction • Conclusion: Submillimetre and X-ray observations show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 1044 ergs per second

  4. Sample Selection • Of all parts of the electromagnetic spectrum, the far-infrared to millimetre waveband offers the best opportunity to measure star formation in galaxies hosting AGN • The combination of deep X-ray and submillimertre observations therefore offers the best prospects for studying the association of star formation and accretion during the 1<z<3 when star formation and black hole growth in massive galaxies were at their most vigorous

  5. Sample Selection • X-ray catalogue of the CDF-N • Sample restriction: those sources detected in the most penetrating (2-8kev) band, further limit the sample to those sources for which spectroscopic redshiftsare available in the literature. In order to restrict the X-ray sample to AGN, discard any sources with 2-8kev luminosity LX <1042 erg s-1

  6. Sample Selection • Part of the HerMESprogramme: submillimetre observations of the CDF-N • Chose the 250 um catalogue and use only sources with 250 um flux densities greater than 18 mJy • X-rays sources were matched to 250 um sources within 6arcsec, corresponding to approximately 95% confidence in the 250 um positions

  7. Data Analysis

  8. Data Analysis

  9. Data Analysis • Incompleteness in the spectroscopic redshifts, or absorption of the X-ray flux by gas and dust, might have effects on the results • Also verified the low 250 um detection rate of AGN with Lx>1044 erg s-1 using the Extended Chandra Deep Field South field

  10. Data analysis • Infrared spectral energy distributions for the 250-um-detected AGN were constructed by combining the SPIRE photometry with 3.6-160 um photometry from the Spitzer • X-ray and infrared properties of the 11 250-um-detected AGN with 1<z<3 and Lx in the range 1043-1044 erg s-1 are given in Table 2

  11. Data Analysis

  12. Data Analysis • Stacking analysis for the 1<z<3 AGN

  13. Two models • The form of AGN feedback is responsible for terminating star formation in the host galaxy. quasar mode • Two families of feed back models radio mode

  14. Spectroscopic redshifts of CDF-N X-ray sources • Take a recent compilation as main source of spectroscopic redshifts • give a number of spectroscopic redshifts and references which are not listed in the main source

  15. Spectroscopic redshifts of CDF-N X-ray sources 返回

  16. Effect of redshift incompleteness • Examine whether the limited spectroscopic completeness(64%) has any effect on the results • A large fraction(87%) of the X-ray sources within the CDF-N have photometric redshifts, and so offer a good test as to whether the spectroscopic comleteness has a significant influence on the results

  17. Effect of redshift incompleteness

  18. Effect of redshift incompleteness • Look specifically at the identification statistics of those 2-8 kev X-ray sources which are associated with 250 um sources. • A total of 33 2-8 kev X-ray sources are associated with 250 um sources, of which 27 are spectroscopically identified • For the 6 sources without spectroscopic redshifts, Fig.S1 shows the tracks of X-ray luminosity as a function of redshift

  19. Effect of redshift incompleteness 返回

  20. Effect of X-ray absorption • X-rays in the 2-8 kev band can penetrate considerable column densities of material, but column densities>1023 cm-2 can lead to significant attenuation of the X-ray flux • The hardness ratio of 2-8 kev/0.5 kev X-rays is a crude but effective estimator of the degree of X-ray absorption • Applying the Fisher’s exact test, we can demonstrate that the 250 um detection rate depends on X-ray luminosity, and can not state with such confidence that the 250 um detection rate depends on X-ray absorption

  21. Effect of X-ray absorption 返回

  22. Verification in the ECDF-S • Extended Chandra Deep Field South is a larger field than the CDF-N, containing a larger sample of AGN with Lx>1044 erg s-1 • The 250 um detections in the ECDF-S plane are shown in Figure S3, analogous to Fig. 1 of the main article

  23. Verification in the ECDF-S 返回

  24. Infrared spectral energy distributions of 250 um-detected AGN • The spectral energy distributions and best fit models for the AGN associated with 250 um sources with 1<z<3 and 1043 <Lx< 1044

  25. Infrared spectral energy distributions of 250 um-detected AGN 返回

  26. Obtaining the average star formation rates through stacking 返回

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