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/co-

evolution?

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

z = 7

no extinction

t = 50 Myrt = 100 Myrt = 300 Myrt = 500 Myrt = 600 Myrt = 800 Myr

The Balmer break is a prominent feature for stellar populations age t > 100 Myrs

Use near– and mid–IR to select high redshift and evolved galaxies?

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

• z = 5• z = 8

• z = 5• z = 8

• z = 2• z = 4

• z = 5• z = 8

• z = 5• z = 8

• z = 2• z = 4

K-selected sample from GOODS-S

HST/ACS (BViz);VLT/ISAAC (JHKs);

SST/IRAC (3.6, 4.5, 5.8, 8m) 5754 sources

155 / 85 selected; 14/12 z > 5 (total 17)

~82% complete at KAB = 23.5

Model tracks from BC03

Post-starburst galaxies (age 0.2–1.0 Gyr)Elliptical (age > 3 Gyr)

Dusty starburst galaxies

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 = 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 = 6.5no current star formationage ~ 0.65 – 1.0 GyrEB-V = 0.0M* = 5 1011 Mo

Z ~ 0.2 – 1.0 Zo

z = 5.6EB-V = 0.025age = 0.8 Gyr = 0.2 GyrM* = 1 1011 Mo

z = 4.9EB-V = 0.150age = 1.0 Gyr = 0.3 GyrM* = 2 1011 Mo

Vanzella et al. 2006

zspec = 5.554

(Yan et al. 2006)

Stellar mass densityfrom Yan et al. 2006

The stellar mass densityderived from M*~1011 Mo

at z~5.4 and z~4.5 appearconsistent with the observeddecrease with redshift

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