SFR and COSMOS Bahram Mobasher + the COSMOS Team

COSMOS offers: Extensive multi-waveband surveys from radio to X-ray Large area coverage ( 2 sq. deg.) HST/ACS morphologies (B/D, Sersic, concentration, asymmetry, clumpiness) Accurate photometric/spectroscopic redshifts and spectral types (from early-type to starburst) Galaxy masses

How COSMOS can help to understand: Physics of star fromation activity Nature of star forming galaxies Main parameters affecting the SFR

Star Formation Rate How different star formation diagnostics are compared ? What is the role of galaxy mergers on SF activity ? How the SFR changes with redshift for different morphologies of galaxies ? Are dusty galaxies more actively star forming ? How SFR depends on galaxy environment ?

Low-z Q1: How are Different SF Diagnostics Compared ?

UV (GALEX); U (CFHT); H  (VLT); IRAC (Spitzer); MIPS(Spitzer); radio (VLA)

UV Luminosity (GALEX) Produced by young massive stars Is directly proportional to SFR Highly affected by dust extinction Old population also contribute to the UV flux

H  Line (VLT/VIMOS) Emission line produced by star-forming regions Less affected by dust extinction Can be used at high redshifts Is directly correlated to SF activity

Mid/Far-IR Luminosity (IRAC/MIPS) FIR radiation is produced by absorption and re-emission of the UV light by dust Mid-IR emission is produced by PAH features Far-IR surveys provide an easy way to select unbiased samples of SF galaxies Need to calibrate PAH features as a measure of SFR

Radio Luminosity (VLA) Produced by synchrotron radiation generated by electrons from Type II SNe Indirectly is proportional to SFR Not affected by dust extinction

Q2: How the SFR is Affected by Galaxy Interaction/mergers ? Q3: How does this change in different environments and with redshift?

Concentration Most z<=1 optically selected starbursts have concentration indices which are significantly smaller than most early types C>0.3 : 12 % SB, 18% Late, 73% E/Sa Komogorov-Smirnov ( K-S) test - SB vs Early type : 7e-7 (> 99.9%) - SB vs Late-type : 0.53 Large C & galfit Sersic n=3-4 correlate AGN fraction : CDF-S X-ray catalog : 2% of SB host AGN vs >25% of Early types

Asymmetry in rest frame B 55 % of z 0.3) compared to lower fractions in late (20% ) and early (12%). K-S test on A B - SB vs Early type : 1e-10 - SB vs Late-type : 3e-4 ABAB Large A B : highly asymmetric distribution of massive SF (no m=2 symmetry) - Externally triggered : tidal interactions, mergers

Q4: How Disk-Size Relation changes with environment and redshift ?

Ravindranath et al –Sersic indices n<2 –Rest-frame M B <-19.5 –Photometric redshifts

Disk galaxy evolution from GOODS Ravindranath et al Tendency for smaller sizes at z~1 (30% smaller) after correcting for measurement bias Number-densities are relatively constant to z~1

Intermediate Redshift: Q5: How the Total SFRs Change with Redshift ? Q6: How the SFR for Different Types of Galaxies change with Redshift ?

Rest-frame 2800 A: U: 0.30 < z < 0.42 B: 0.52 < z < 0.68 V: 0.88 < z < 1.04 R: 1.13 < z < 1.37 I: 1.62 < z < 1.87 z: 2.11 < z < 2.33

COSMOS-GOODS-GALEX

Q7: What is the Effect of Environment on the SFR ? Q8: How the Environmental Effect Change with Redshift ?

Median SFRs: 0.71 (F) 0.76 (C) 0.30 < z < 0.42

Median SFRs: 0.84 (F) 0.95 (C) 0.52 < z < 0.68

Median SFRs: 2.45 (F) 2.75 (C) 0.88 < z < 1.04

SFR in Different Environments Field LSS M sun /yr 0.3 < z < < z < < z <

Q9: What is the LF of Star- forming Galaxies ? Q10: How the LF for Star- forming Galaxies Change with Redshift ? Q11: What is the Type- dependence of the LF ?

LF Parameters for  =-1.2 M* < z < < z < < z < 1.04 – < z < 1.37 – < z < 1.87 – < z < 2.33 –20.38

Type-dependent 2800 A LF parameters M *  (2800A) Total Early-type Late-Type Starburst

High-z Q12: What is the SFR and Stellar Mass Associated with LBGs and LAEs at 4.5 < z < 6.5 ?

rest-optical & -IR at z=5.8 SST IRAC detections of z~6 galaxies => stellar population & dust fitting possible Dickinson et al in prep ch1, 3.6  m rest =5300A ch2, 4.5  m rest =6600A

LBG at z=5.83 Bviz (ACS) JHK (ISAAC) IRAC

LAE at z=5.7 Bviz (ACS) JHK (ISAAC) IRAC

LAE LBG z 5.7 (6.2) 5.8 E(B-V) Age (Gyr)  (Gyr) Metallicity Mass (M sun /yr) 1 x x Log (L bol )

SF Working Group What can we do with the available data now? What data we need ? What we plan to do with the up-coming data (ie Ha, Spitzer) ?

The available data: UV, U-band, BVRiz, radio, phot-z’s, spectral types, mass, LSS identification, rest-frame 2800A Future useful data: Near-IR spectroscopy, sub-mm data Up-coming data: H , Spitzer

SFR- Outstanding Questions: How different star formation diagnostics are compared ? What is the role of galaxy mergers on SF activity ? How the SFR changes with redshift for different morphologies of galaxies ? Are dusty galaxies more actively star forming ? How SFR depends on galaxy environment ? What is the relation between the mass of galaxies and their SFRs ? How does this depend on the environment/redshift/morphology ?

Continued… How the LF and correlation function of SF galaxies change with redshift/morphology ? What regulates the SFR for LBGs and LAEs ? ( mass ? Size? Morphology?). How different are these in terms of their SF activity ? Extension of SFR vs. redshift relation to z~7, using narrow-band and LBG surveys. Type-dependence of the SFR vs. z relation How different is the SFR in filamentary structures compared to clusters or isolated fields ? How does this change with morphology ?

Continued… Could the MIPS data be used to measure SFR (from PAH) at z~2 ? 82% of the SF galaxies in GOODS-N have MIPS detection. How effectively we could use Paschen lines to measure dust-free SFR ? Would IRS be useful ? Evolution of SFR-mass relation Cross correlation between SFR and mass maps