Two Main Techniques. I: Star-forming Galaxies

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1 p.1/24

2 The high redshift universe has been opened up to direct observation in the last few years, but most emphasis has been placed on finding the progenitors of today s massive ellipticals. p.2/24

3 Two Main Techniques. I: Star-forming Galaxies Galaxies photometrically selected in rest-frame UV within well-determined z intervals. Follow-up spectroscopy: > 1000 galaxies with z = 3.0 ± 0.3 (LBGs), z = 2.2 ± 0.3 (BX). > 100 with z = 1.7 ± 0.35 (BM). p.3/24

4 Two Main Techniques. II: Absorption-selected Galaxies p.4/24

5 The Links to Today s Galaxies. I: Star-forming Galaxies The working hypothesis that these are the progenitors of today s spheroids elliptical galaxies and bulges of massive spirals, as proposed by Steidel et al. in 1996, is supported by: High star formation rates: L LBG at z = 3 has SFR = 45h 2 M yr 1 z = 3 LBGs Shapley et al p.5/24

6 The Links to Today s Galaxies. I: Star-forming Galaxies The working hypothesis that these are the progenitors of today s spheroids elliptical galaxies and bulges of massive spirals, as proposed by Steidel et al. in 1996, is supported by: High star formation rates: L LBG at z = 3 has SFR = 45h 2 M yr 1 Near-solar metallicities z = 3 LBGs Shapley et al p.6/24

7 NIRSPEC K-band Spectra of 100 BX Galaxies K s 20 [N II]/Hα = 0.25 [O/H]= /5 [O/H] K s > 20 [N II]/Hα = 0.13 [O/H]= /2 [O/H] p.7/24

8 This result is not unique to UV-selected galaxies. Similar conclusions (Z 1/2Z Z ) have been reached for: 32 FORS Deep Field galaxies at z = 2.3 (UV Stellar Wind Lines Mehlert et al. 2002) 13 GDDS (IR selection but UV bright) galaxies at 1.3 < z < 2 (UV Interstellar Absorption Lines Savaglio et al. 2004) 5 K20 (IR-bright) galaxies at 1.7 < z < 2.3 (UV Stellar Photospheric Lines de Mello et al. 2004) 11 SCUBA (submm-bright) galaxies at 2 < z < 2.7 ([N II]/Hα ratio Swinbank et al. 2004) p.8/24

9 All the above studies give an approximate measure of the overall metallicity. Only in one case do we have more detailed knowledge of the relative proportions of different elements: Suggestive of a rapid ( 300 Myr) timescale for the enrichment, consistent with high ( M yr 1 ) SFRs of these galaxies. p.9/24

10 The Links to Today s Galaxies. I: Star-forming Galaxies The working hypothesis that these are the progenitors of today s spheroids elliptical galaxies and bulges of massive spirals, as proposed by Steidel et al. in 1996, is supported by: High star formation rates Near-solar metallicities Rapid assembly of stellar masses of up to a few M Strong clustering Shapley et al p.10/24

11 Blaizot et al 2004 (GALICS Project) Cosmic Time (Gyr) Galaxies which have already reached Z < Z at z = 2 2.5, while still supporting high rates of star formation, will attain supersolar metallicities by z = 0. p.11/24

12 The main ingredients of models of the formation of the Milky Way Bulge: Very short infall timescales, 0.5Gyr Rapid enrichment to near solar metallicity Significant outflow of gas and metals High redshift of formation, z 5 M M 9 >= e.g. Ferreras, Wyse, & Silk 2003 >; are very much in line with the properties of typical LBG & BX galaxies. p.12/24

13 Masses and Clustering SEDs indicate assembled stellar masses M, M = M p.13/24

14 Masses and Clustering SEDs indicate assembled stellar masses M, M = M Clustering properties (r 0 = h 1 Mpc) are those of dark matter halos with M DM = M (Adelberger et al. 2005) p.13/24

15 Masses and Clustering SEDs indicate assembled stellar masses M, M = M Clustering properties (r 0 = h 1 Mpc) are those of dark matter halos with M DM = M (Adelberger et al. 2005) In N-body simulations, these halos evolve with time to have values of r 0 similar to those measured for elliptical galaxies in the DEEP ( z = 1) and SDSS ( z = 0.2) p.13/24

16 The Links to Today s Galaxies. II: QSO Absorbers If the star-forming galaxies at z = 2 3 are the progenitors of ellipticals and bulges, where are the disks? In current CDM models, disks build up slowly over time. But the metallicity of the stars changes little over the lifetime of the disk (disk stars have a flat age-metallicity relation) see, e.g. Naab & Ostriker p.14/24

17 Most DLAs don t fit this picture very well, unless the stellar disk is surrounded by a more extended envelope (halo/thick disk?) of gas which is metal-poor/has a steep metallicity gradient. Akerman et al p.15/24

18 Are theoretical ideas whereby galactic disks build up slowly through mergers... Theory: Moore et al p.16/24

19 ... consistent with recent findings of very extended stellar disk structures in nearby galaxies? Observations: Ibata et al p.17/24

20 Evidence for Rotation in Star-Forming Galaxies? Spatially tilted Hα emission line profiles are not unusual... BX691 BX600 MD41 1" 1" 1" BX447 MD103 BX511 1" 1" 1" Erb et al p.18/24

21 Evidence for Rotation in Star-Forming Galaxies? But do they trace rotation curves... Erb et al p.18/24

22 Evidence for Rotation in Star-Forming Galaxies? Whose apparent velocity extent depends on the seeing... Q1700 BX691 Erb et al p.18/24

23 Evidence for Rotation in Star-Forming Galaxies?... or merging protogalactic clumps? GOODS-N ACS images Erb et al p.18/24

24 The Future is... Orange! p.19/24

25 OSIRIS will resolve 2-D velocity fields of z 2 galaxies on scales of 100 mas 1 kpc sufficient to differentiate between ordered disk rotation (c) and merging sub-units (d) GOODS-N BX1332 (z = ) Law et al p.20/24

26 Conclusions (1) We are building an increasingly detailed picture of the high redshift universe... p.21/24

27 Conclusions (1) We are building an increasingly detailed picture of the high redshift universe... (2)... but the signatures of (the progenitors of) galactic disks have so far proved difficult to recognise. p.21/24

28 Conclusions (1) We are building an increasingly detailed picture of the high redshift universe... (2)... but the signatures of (the progenitors of) galactic disks have so far proved difficult to recognise. (3) We are on the verge of a breakthrough in this area as Integral-field near-ir spectrographs + Adaptive Optics come on line on the Keck and VLT telescopes. p.21/24

29 Abundances at High z. II: Absorption-selected Galaxies (DLAs) We find quite a different picture when we sample high-z galaxies by absorption cross-section: Generally metal-poor: [ Zn/H ] = 1.2 (1/15Z ) at 1.8 < z < 3.5 p.22/24

30 Abundances at High z. II: Absorption-selected Galaxies (DLAs) We find quite a different picture when we sample high-z galaxies by absorption cross-section: Generally metal-poor: [ Zn/H ] = 1.2 (1/15Z ) at 1.8 < z < 3.5 Wide dispersion (two orders of magnitude) in metallicity p.22/24

31 Abundances at High z. II: Absorption-selected Galaxies (DLAs) Dust-induced bias evidently not an issue in the light of recent results from the CORALS survey: [ Zn/H ] CORALS [ Zn/H ] Optical +0.2 p.23/24

32 A Stellar Mass-Metallicity Relation at High Redshift Erb et al p.24/24