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Searching for massive galaxy progenitors with GMASS

Searching for massive galaxy progenitors with GMASS ( G alaxy M ass A ssembly ultradeep S pectroscopic S urvey) (a progress report). Andrea Cimatti (INAF-Arcetri)

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Searching for massive galaxy progenitors with GMASS

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  1. Searching for massive galaxy progenitors with GMASS (Galaxy Mass Assembly ultradeepSpectroscopic Survey) (a progress report) Andrea Cimatti (INAF-Arcetri) M. Bolzonella (INAF-Bologna), P. Cassata (INAF-Milano), E. Daddi (NOAO), M. Dickinson (NOAO), A. Franceschini (Uni-Padova), C. Halliday (INAF-Arcetri), J. Kurk (MPIA), C. Mancini (Uni-Firenze), M. Mignoli (INAF-Bologna), L. Pozzetti (INAF-Bologna), A. Renzini (INAF-Padova), G. Rodighiero (Uni-Padova), P. Rosati (ESO), G. Zamorani (INAF-Bologna)

  2. The emerging picture z ~ 0 0 < z < 1 1 < z < 2 Cimatti et al. 2004 McCarthy et al. 2004 Saracco et al. 2005 Daddi et al. 2005 Thomas et al. 2005 Bundy et al. 2006 “Downsizing” evolutionary pattern (Cowie et al. 1996) (supported by several other results, e.g. FP, SSFR, …)

  3. z > 1.5-2 z < 1-2 ? Powerful, short-lived, massive starbursts LBGs ?, BzKs ?, DRGs ? SMGs ? IEROs ? Hyper-EROs ? … ? Old, passively evolving, massive early-type galaxies GMASS •  Search for the highest redshift ETGs •  Identify and study the progenitors of massive ETGs • Stellar mass assembly evolution at 1.5<z<3

  4. GMASS main features ESO VLT + FORS2 Large Program (145h; PI Cimatti) Target field : 50 arcmin2 in the GOODS-South/HUDF region Sample selection :Spitzer+IRAC, m(4.5μm) < 23 (AB) + z(phot) > 1.4 Sample size : N(m<23)= 1190, N(zphot>1.4)= 390 , 210 in 6 spectroscopic masks Ultradeep spectroscopy to B=27, I=26, 11h-30hintegration Complementary to other surveys (depth, no color selections) 100% of data taken in service mode up to 31 December 2005 (80% reduced) Reduced and calibrated data will be publicly available worldwide Spitzer VLT Arcetri

  5. GMASS target field 51 arcmin2 within the GOODS-South field covering a large fraction of the K20 and Hubble Ultra Deep Field (UDF) areas

  6. Why 4.5µm selection ?  Best compromise among IRAC bands (sensitivity, PSF, IQ, blending)  “Negative” k-correction (the stellar SED peak enters the 4.5μm-band for z>1.5)  Better sensitivity to stellar mass up to z~3  Less affected by dust extinction than K-band 1.6μm bump

  7. Preliminary redshift statistics Spectroscopic redshift efficiency: red (12h-30h): ~70% (not final) blue (11h-15h): ~95% z(phot) or z(spec) z(spec) (literature + GMASS) z(spec) (GMASS only) Small contamination from objects with zphot > 1.4 and zspec < 1.4

  8. Comparison with DRG selection

  9. Spectra

  10. J. Kurk

  11. Average spectrum of first blue mask objects M. Mignoli N=35

  12. Multi-band SEDs

  13. Photometric SED fitting with known z(spec) Bolzonella, Pozzetti UBVRIz + BViz + JH + JHKs + IRAC

  14. Stellar mass estimates zspec zphot

  15. Main properties •  Passive or weakly star-forming • Old stars (1-3 Gyr) • Massive (log M_stars = 10.9 – 11.2 Msun, Chabrier IMF) • Low levels of specific SFR • Early-type morphology • Star-forming Low mass blue systems (log M_stars ~ 10 Msun) Red systems with large mass (log M_stars ~ 11+) and strong star formation (50-100 Msun/yr) Red more because of age than dust extinction High specific star formation Solar metallicity from UV photospheric features (Halliday et al.) Strong morphological K-correction Star formation located mostly in outer regions “Transition” phase leading to an old/massive ETG ?

  16. Beyond GMASS …

  17. Optical blank-fields + extremely K-band faint (K[AB]<25) z J H K 3.6 4.5 5.8 8.0 24 micron STACKING (3”x3”) ACS: b+v+i+z Rodighiero et al.

  18. Dusty Starbursts @ z~2.5 ? Masses: 10^10-10^11 => SFR~1000 M_sun/yr Superantennae +Av=3 Post-starbursts @ z~6.5 ? Masses: 10^11-10^12 + AGN (Mobasher et al. 2006) Dusty Torus

  19. Mid-Infrared colours: the bulk of the sources are consistent with a population of starbursts at z~2-3 Are we looking at a mixed population ?

  20. Short summary GMASS is designed to investigate the physical mechanisms leading to the formation and mass assembly of massive early-type galaxies In the redshift range of 1.5 < z < 3, GMASS is unveiling co-existing populations of old, passive, massive early-type galaxies up to z~2 and massive starbursts probably experiencing their dominant phase of star formation and mass assembly Population of IRAC galaxies with no optical and sometimes near-IR counterparts: old systems + AGN at z>6 or extreme dusty starbursts ? Have a look at Claire Halliday’s and Jaron Kurk’s posters and STAY TUNED !

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