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Observing the Feedback Process? Peter Capak (SSC-Caltech) Nick Scoville (Caltech) Mara Salvato (MPIA- Garching) Dan Masters (UC Riverside) Tommy Wiklind (ESO-ALMA) Bahram Mobasher (UC Riverside) Questions • What are the parameters affecting the feedback process? • What are the relative contributions of starburst and AGN to the feedback process? • What is the observational evidence for the starburst-AGN connection/coevolution? AIM • Find galaxies while undergoing the feedback process- by star formation or AGN • This needs selection of evolved galaxies with high stellar mass at relatively high redshifts, hosting AGN • Select bright enough galaxies to allow follow-up spectroscopy Use near– and mid–IR to select high redshift and evolved galaxies? The Balmer break is a prominent feature for stellar populations age t > 100 Myrs z=7 no extinction t = 50 Myr t = 100 Myr t = 300 Myr t = 500 Myr t = 600 Myr t = 800 Myr Source Selection • Construct a Spitzer/IRAC 4.5 micron selected sample, using COSMOS data • This corresponds to a “mass-selected” sample at z~2-5 • Select galaxies with zphot > 4 from this sample • Select objects with bright IRAC ch1 and ch2 fluxes (high mass & evolved systems) • Objects with marginal or no detection at optical bands Model tracks from BC03 •z=5 •z=8 •z=5 •z=8 •z=5 •z=8 •z=5 •z=8 •z=2 •z=4 Post-starburst galaxies (age 0.2–1.0 Gyr) Elliptical (age > 3 Gyr) Dusty starburst galaxies •z=2 •z=4 K-selected sample from GOODS-S HST/ACS (BViz); VLT/ISAAC (JHKs); SST/IRAC (3.6, 4.5, 5.8, 8mm) 5754 sources 155 / 85 selected; 14/12 z > 5 (total 17) ~82% complete at KAB = 23.5 Stellar Population Models Population synthesis models (Bruzual & Charlot 2003): • Redshift range z = 0.2 - 8.6 • Age range = 5 Myr - 2.4 Gyr • Calzetti attenuation law EB-V = 0.0 - 1.0 • IGM absorption • Metallicities Z = 0.2, 0.4 1.0, 2.5 Zo • Salpeter IMF: 0.1 – 100 Mo • Star formation history: exponentially declining SFR t = 0 - 1.0 Gyr Fit to the Stellar Component Redshift 4.37 EB-V = 0.20 Age (Gyr) = 1.4 SF time-scale (Gyr) =0.6 Log(M*) = 11.10 Msun Corrected for dust Not corrected for dust Observations at longer Wavelengths • The source is detected at 24 micron • At 4.5-24 microns the SED has a power-law shape. • the galaxy is not detected at mm wavelengths with IRAM; at sub-mm (1.2 mm) with MAMBO; at radio continuum (1.4 GHz) and X-ray. • The absence of sub-mm and mm flux implies there is little or no cold dust => no on-going star formation activity Pure AGN SEDs AGN + dust (NGC6240) QSO (type 2) Stellar Component Pure Starburst SEDs Pure starburst SEDs: Arp220 M82 The template SEDs contain significant extinction Obscured AGN+Starburst SED Mkr231 SED: Stellar+ AGN-heated dust with an intense starburst at the center. Large Infrared luminosity Stellar Component Higher Redshift Counterparts JD2 (J-dropout) in HUDF (Mobasher et al. 2005) z = 6.5 no current star formation age ~ 0.65 – 1.0 Gyr EB-V = 0.0 M* = 5 1011 Mo Z ~ 0.2 – 1.0 Zo z EB-V age t M* = 5.6 = 0.025 = 0.8 Gyr = 0.2 Gyr = 1 1011 Mo z EB-V age t M* = 4.9 = 0.150 = 1.0 Gyr = 0.3 Gyr = 2 1011 Mo zspec = 5.554 Vanzella et al. 2006 Stellar mass density The stellar mass density derived from M*~1011 Mo at z~5.4 and z~4.5 appear consistent with the observed decrease with redshift from Yan et al. 2006 (Yan et al. 2006) Conclusions • The discovered galaxy appears to be a lower redshift counterpart of the more distant (old and evolved) systems • It has gone through intense star formation activity (77 Msun/year) • Given that there is an AGN at the core of the galaxy, the SF is not the only process responsible for removal of gas • Number density of these galaxies strongly constrains the CDM models for formation of galaxies