Quiescent and Starbursting star-forming galaxies at z=2

1. Quiescent and Starbursting star-forming galaxies at z=2 Giulia Rodighiero (University of Padova) On behalf of the PEP Team Trieste - The Physics of Star Formation – 18 October 2012 COSMOS24/100/160μm

3. The Main Sequence of Star-forming galaxies at 1.4 < z < 2.5

4. Two regimes of star formation: quasi-steady on the main sequence, starbursts off of it (Daddi et al 2010)

5. Two regimes of star formation: quasi-steady on the main sequence, starbursts off of it Two Critical Questions: Q1: what is the relative number of main sequence and starburst galaxies? Q2: what is their relative contribution to the global, cosmic star formation rate density?

6. Answering with HERSCHEL/PACS observations over the GOODS & COSMOS fields

7. The PEP- GOODS South (Lutz et al. 2011) ~21’x14’

8. The PEP-COSMOS ~2 square degrees

9. HERSCHEL/PACS observations over the GOODS & COSMOS FIELDS Rodighiero et al. (2011)) Data-set required to fully sample the stellar mass – SFR plane: PACS 100μm and 160μm shallow source catalogs with extraction based on 24μm prior positions + IRAC-selected source catalog from Ilbert et al. (2010) PACS 70, 100 and 160μm deep catalog in GOODS-S + multiwavelength photometry, spec & photo-z BzK COSMOS catalog (Daddi/McCracken) BzK GOODS-S catalog (Daddi et al. 2007)

10. SFR: derived from SED fitting to the complete UV-to-PACS observed photometry and converting the bolometric emission ([8-1000]μm) with the Kennicutt et al. (1998) relation (inclusion of unobscured SF does not affect the results). STELLAR MASSES: classical SED fitting to the UV-to-IRAC (5.8μm) with Bruzual & Charlot models

11. Populating the mass-SFR plane

12. X4-MS PACS-shallow PACS-deep BzK

13. Number densities as a function of mass and SSFR bins: defining the ON & OFF main sequence loci

14. SFR density: % OFF sequence ~10% Number density: % OFF sequence ~2% SFR density Number density ON and OFF sequence

15. Morphological WFC3/HST analysis in GOODS-S: The actual major-merger contribution to the star formation budget may be as low as~15% Kaviraj et al. 2012 (arXiv 1210.2160)

16. DUTY CYCLE ON/OFF the MAIN SEQUENCE at 1.5<z<2.5 With only ∼2% of the massive galaxies being OFF the main sequence, on average each galaxy spends 20 Myr in the starburst mode. This is actually much shorter than both the gas depletion timescale (~0.5 Gyr) and the dynamical time in starburst galaxies (~50-200 Myr, Daddi et al. 2010; Genzel et al. 2010). Not all galaxies may experience a (merger-driven) starburst during these ~2 Gyr of cosmic time interval.

17. ON- and OFF-main sequence IR Luminosity functions PEP/HERMES-COSMOS-GOODS-ECDFS sources Predictions from Sargent et al. 2012 ON-MS OFF-MS Gruppioni et al. (2012)

18. The integrated bolometric LFs confirm the dominant role of the main sequence population at 1<z<2 for the mass assembly, both in number and luminosity/SFR densities. Gruppioni et al. (2012)

19. MAIN CONCLUSION The merger-enhanced SFR phases are relatively unimportant for the stellar mass growth of z ∼ 2 galaxies, and probably so at all redshifts. Still, going through a merging-driven starburst phase may turn star-forming galaxies into passive ellipticals. TESTING THE STARBURST-MERGER PARADIGM

20. Padova Science Activities Follow-up campaign of extreme off-sequence Herschel sources at z=2 (1) P.I. G. Rodighiero

21. IRAM PdB CO(2-1) line:PACS-164 5-σ detection at z=1.646 Data analysis by Chiara Feruglio

22. L(IR)/L(CO) larger than BzK sources Daddi et al. (2010)

23. The S-K relation (preliminary!!) Assuming a “starburst” α(CO) value Daddi et al. (2010)

24. Padova Science Activities Follow-up campaign of extreme off-sequence Herschel sources at z=1.5 (2) P.I. J. Silverman

25. The AGN population in the mass-SFR plane:a key test to constrain the AGN feedback and the joint black-hole/star-formation accretion rate AGNs reside mostly in main-sequence hosts, reflecting the AGN - sSFR connection (Rovilos et al. 2012) The “Hidden AGN Main Sequence” at z~1 and z~2: the same secular processes that drive the bulk of star formation are also responsible for the majority of SMBH growth (Mullaney et al. 2012)

26. Singularly detected AGN seem to live preferentially on the Main Sequence Herschel COSMOS Obscured AGN: F(24μm)/F(R)>1000 & (R-K)>4.5 (Fiore et al. 2008) Herschel GOODS X-ray selected AGN (with thanks to P. Popesso & M. Brusa)

27. The most SB sources: x10>MS Dominated by SFR Obscured AGN present but does never dominate the bolometric far-IR emission

28. SED fitting of Herschel sources with local empirical templates Type 1 AGN Type 2 AGN Low Luminosity AGN Starburst Spirals/quiescent SFR (from C. Gruppioni SED fitting) Hard to derive trends….

29. SED fitting with energy balance (Da Cunha et al. 2008/2010) + dusty torus component (Berta et al. in prep.):  Hidden AGN fraction in the mid-IR and far-IR observed observed

30. Test case at 1.4<z<1.7 (preliminary…) Obscured AGN homogeneously distributed on the mass-SFR plane (at least in bright LIR limited samples) ON OFF Increasing AGN fraction (from 10% to 70%)

31. P.I. John Silverman

33. Broad emission lines consistent with nuclear activity Courtesy of J. Silverman

34. Overall test with X-ray stacking in different mass-SFR bins (in progress…): X4-MS

35. SUMMARY - Majority of star formation at high-z takes place on the MS - Outliers to the MS are starbursts also in the Schmidt-Kennicutt plane (tentative… well ok  … one source … but more to come!) - AGN activity and SFR are well correlated along the MS, what’s above? - Ideas, suggestions…?

36. FOR DiSCUSSION: underestimation of stellar mass in heavily extinguished galaxies Poster & paper (submitted) by Barbara Lo Faro Dead off-MS? sSFR of starbursts would drop down (by a factor ~6-10!)…

37. Thank you!