NO CLEAR SUBMILLIMETER SIGNATURE OF SUPPRESSED STAR FORMATION AMONG X-RAY LUMINOUS AGNS

1. Author: C. M. Harrison et al. Reporter: Saiyu Hou NO CLEAR SUBMILLIMETER SIGNATURE OF SUPPRESSED STAR FORMATION AMONG X-RAYLUMINOUS AGNS

2. Abstract • Introduction • Work of Page et al. • Catalogs and data • X-ray data (AGNs) • IR data (star-forming galaxies) • Measuring average SFRs • Results and discussion

3. Introduction • Simulations and theoretical models • AGNs suppress star formation • By heating or removing cold gas • Indirect observational support *

4. Results of other groups • Approach: explore the relation of AGN activity and star formation • Moderate-luminous AGNs: mean SFRs comparable to co-eval galaxies* • Luminous AGNs: still not clear • Many studies argue: SFR rises or remains flat towards the highest luminosities*

5. Work of Page et al. • Page et al. • Data: Herschel-SPIRE & CDF-N • Z=1~3* • Mean SFRs of luminous AGNs are significantly lower than moderate luminous ones. • Important: direct, empirical connection • Disagreement with other groups • Limitation: small number of sources (7~14 in Lx>10^44 erg/s bins)

7. Influence of redshift incomplete

8. Correction for absorption

11. Work of Harrison et al. • Harrison et al. • Herschel-SPIRE 250μm in wider-area COSMOS * • ΛCDM, Salpeter IMF • Improve source statistics by an order of magnitude for luminous AGNs • Explore mean SFRs: using stacking analysis, does not explore individual detection rates* • repeat the analysis using Her-SPIRE 250 μm data in the CDF-N and CDF-S fields to explore the effect of smaller fields (different detection fraction lead to different SFR)

12. Catalogs and data AGN samples • AGNs samples: X-ray selected • CDF-N,CDF-S,COSMOS samples • Lx=10^42~10^45 erg/s, z=1~3 • Include both photometric (53%) and spectroscopic (47%) redshifts results do not change, spectroscopic only • Derive the rest-frame observed 2-8 Kev luminosity, as Page* • Lx= 4πD2Fx(1+z)(Γ-2)*

14. IR data • IR data: where the mean SFRs are derived • Generally, AGNs contribute < 10% to IR lum • 250um Her-SPIRE which are unaffected by AGN or obscuration of dust • Results: consistent between GOODS-H CDF-N and HerMES

17. Results & discussion • ① CDF-N: stacking results agree with Page et al. * • ② COSMOS*: SFRs of Lx>1044 erg/s AGNs ≈ Lx=1043~44 erg/s AGNs • Z=1~3 AGN: mean SFR independent of Lx, Lx>1044 consistent with Lx=1043-44* • Flat SFR distribution out to Lx=1044.8 erg/s • poor source statistics and potentially field–to–field variations (cosmic variance)

19. ③ Further investigate: SPIRE data in CDF-S * • ④ Restack CDF-N AGNs using GOODS-H program * • Results of the three fields:* • Broad agreement -- moderate luminous AGNs • Variation -- luminous AGNs

21. Possible explanation • Our results: AGN activity does not suppress SF, really? • AGN lifetime < time between the onset of luminous AGNs and the shut down of star formation • Probably: different timescales of these processes

22. conclusion • Find no evidence for significantly reduced mean SFRs among high luminous AGNs • Mean SFRs consistent with typical star-formation galaxies • Maybe depending on the timescale involved • Challenging to see the signature of suppression with current data

23. Other References • The suppression of star formation by powerful active galactic nuclei M. J. Page et al. doi:10.1038 /nature11096 • Elbaz, D., Daddi, E., Le Borgne, D., et al. 2007, A&A, 468, 33 • Alexander, D. M., & Hickox, R. C. 2012, NewAR, 56, 93

24. Thanks !