Young bulges and old ellipticals Daniel Thomas University of Oxford Formation epochs of elliptical galaxies SF-AGN connection Stellar populations in spiral bulges Age of the MW Bulge

Old ellipticals - old plots Worthey et al 1992 Absorption-line indices Bender et al 1992 Fundamental Plane Bower et al 1992 Colour-magnitude relation Kodama et al 1998 Colour-magnitude at z>0 Bender et al 1996 Mgb- at z>0 Renzini 2006

Epochs of early-type galaxy formation Kauffmann & Charlot 1998 Thomas, Maraston, Bender, Mendes de Oliveira 2005

Galaxy formation caught in the act sub-mm sources Smail et al 2002; Swinbank et al 2004 z~2–6 Massive objects ~ 1011 M High star formation rates ~ 1000 M/yr Bertoldi et al 2003

Ellipticals in the SDSS Sample of 30,000 morphologically selected ellipticals Kevin Schawinsky (Oxford) Sugata Kaviraj (Oxford) Claudia Maraston (Oxford) Marc Sarzi (Hertfordshire) Seok-Joo Joo (Oxford, Yonsei) Sukyoung Yi (Yonsei)

AGN feedback at work

What about bulges?

Bulges - Imaging Recent star formation in later-type bulges? Bulges in later type spirals have steeper color gradients and are younger (optical/NIR color maps; Balcells & Peletier 1994; Peletier et al 1999; Carollo et al 2001) Recent star formation in later-type bulges? Fingerprints of secular evolution?

Ellis, Abraham, Dickinson 2001 Blue bulges at high z Ellis, Abraham, Dickinson 2001

The Bulge of the Milky Way Zoccali et al 2003

Sample of spiral bulges Proctor & Sansom (2002)  32 objects (11 Es, 6 S0s, 16 bulges)  Exposure ~ 1h per object on 4m  Edge-on, minor axis  Galaxy type from S0 – Sbc  Wavelength range 4000 ≤  ≤ 5500 Å  Ages and Mg/Fe ratios of bulges lower than ellipticals Maraston et al (2003)  Milky Way bulge (integrated light in Baade’s window)  Lick absorption line indices

Deriving stellar population parameters SSP models: TMB03, TMK04

Comparison bulges and ellipticals Thomas & Davies 2006

Rejuvenation of bulges Thomas & Davies 2006

A spectrum of the Bulge Maraston et al 2003

The Milky Way Bulge Thomas & Davies 2006

The Milky Way Bulge SSP models: TMB03, TMK04

The Milky Way Bulge Thomas & Davies 2006

The Milky Way Bulge: really old? Maraston 2004 Zoccali et al 2003

Summary Ellipticals follow anti-hierarchical pattern Spiral bulges follow anti-hierarchical pattern The Milky Way Bulge is young (rejuvenated) ‘Downsizing’, ‘The hierarchy is broken’ Interplay SF-AGN observed in SDSS Rejuvenation at redshifts z < 0.5 Same stellar populations like ellipticals Disc influence negligible down to Sbc

Optical vs near UV Passive Star forming

Anti-hierarchical AGN’s De Lucia et al 2005 Thomas et al 2005 Hasinger, Takamitsu, Schmidt 2005