Quenching in the Green Valley(Preliminary Work)

Joanna WooAdvisor: Avishai Dekel

Hebrew University of Jerusalem

Motivation

Galaxy Bimodality Presumably BC galaxies are quenched and form

RS galaxies Then GV galaxies are still being quenched

What can the GV tell us about quenching mechanisms?

Quenching in GalICS

Hybrid N-body (DM) + SAM Each galaxy has 3 components: disc, bulge, burst Stars form as a function of M

cold / t

dyn

Quenching happens in two ways: During mergers and periods of disc instability, stars

+ gas from the disc move to the burst and then to the bulge (causes bulge to grow, and depletes disc of gas) → BULGE QUENCHING

If a halo grows above 2x1012 M⊙ all SF is shutdown by hand → HALO QUENCHING

Questions

Which quenching mechanisms dominate in which eras?

How does the GalICS SAM compare with the real universe? (SDSS, AEGIS)

Green Valley

The galaxy bimodality is characterised by two sequences: the Red Sequence and the Star Forming sequence

Define GV to be those that are NOT in the RS, and not in the SF sequence

Data

SDSS: Colours: KCORRECT on ugriz (Cooper et al. 2007) SFR: GALEX (Salim et al. 2007) M

*: (Kauffmann et al 2002)

C=R90/R50: sdss website M

halo: (Yang et al. 2008)

AEGIS: Colours: KCORRECT on BRI from Coil et al. 2004 (Cooper et al.

2007) SFR: GALEX (Salim et al. 2009) M

*: SED fits to optical/NIR photometry (Bundy et al. 2006)

B/T: (Simard et al 2002 – kindly provided by David Koo)

Bulge Quenched

Halo Quenched

Bulge Quenched

Halo Quenched

Bulge Quenched

Halo Quenched

Bulge Quenched

Summary of Preliminary Results

At z~0, bulge-quenching is the dominant quenching mechanism in the GV Affects smaller galaxies The GalICS SAM and the SDSS agree

At z~1, halo-quenching was the dominant quenching mechanism in the GV Affects larger galaxies True in GalICS, not enough data in AEGIS

Still to Think About

Better GV sample? In GalICS, bulge-quenching resulted from both

mergers and disc-instability Easy to separate in GalICS. How about in data?

Halo masses for AEGIS? Apply Yang et al method?