1. HERMES: Deciphering the Milky Way’s History Daniel Zucker with Gayandhi de Silva and the HERMES team

2. HERMES: Introduction HERMES: High Efficiency and Resolution Multi- Element Spectrograph Under construction at the AAO (as of 1 July, the Australian Astronomical Observatory) 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 1

3. HERMES Basics 4 arms with VPH gratings and 4k 2 CCDs R~28,000, 200-300 Å/per arm (~1000Å total); higher res w/slitmask (R~50,000) For V~14, S/N ~ 100 in 1 hour Designed to work with 2dF top end on 3.9m AAT at Siding Springs, Australia 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 2

4. HERMES and 2dF 2dF: prime focus robotic positioner with 392 data fibres and a 2º field of view 2dF currently used with AAOmega spectrograph (low- to moderate resolution, 2 arms) Minimum spacing between fibres: 30-40” 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 3

5. HERMES Instrument Status Preliminary Design Review completed, design meets science requirements Final Design Review: late 2010 Optics procurement, grating prototyping, detector testing underway Data simulator and reduction pipeline in testing On track for science operations in 2013 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 4

6. Galactic Archaeology with HERMES Look for evidence from the epoch of the Galaxy’s formation to gain insight into the processes involved One approach: reconstruct the star- forming aggregates that built up the disk, bulge and halo of the Galaxy Some still recognisable kinematically (moving groups); dynamical information for others may be lost, but recognisable by compositions (“chemical tagging”) 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 5

7. Galactic Archaeology with HERMES How important were mergers/ accretion for building the Galactic disk and bulge? (CDM: very) Goal: try to find dispersed groups of stars which were associated at birth because they –were born in a common Galactic star-forming event, or –came from the same accreted galaxy 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 6

8. Chemical Tagging Use detailed chemical abundance patterns of individual stars to associate them with common ancient star-forming aggregates with similar patterns The detailed abundance pattern reflects the chemical evolution of the gas from which the aggregate formed: different supernovae provide different yields  scatter in detailed abundances, especially at lower metallicities 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 7 Freeman & Bland-Hawthorn 2002, Bland-Hawthorn & Freeman 2004, De Silva+ 2009

9. Chemical Tagging For chemical tagging to work within the Galactic disk, some things need to be true (or at least mostly true): –Stars form in large aggregates –Aggregates are chemically homogeneous –Aggregates have unique chemical signatures (defined by several elements) which do not vary in lockstep from one aggregate to another With chemical tagging, we can identify disk stars that are the debris of star-formation aggregates, as well as those accreted from disrupting satellites 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 8

10. Chemical Tagging in Action 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 9 Clusters vs. Field Stars Hyades Coll 261 HR1614 De Silva 2007

11. HERMES: Galactic Archaeology Survey Stellar survey, complete down to V = 14 (~fiber density), covering ~half the southern sky (|b| > 30)  ~10,000 square degrees = 3000 pointings, spectra of 1.2 x 10 6 (!) stars For V ~ 14, R ~ 28,000, with SNR ~ 100 per resolution element in 1 hour, with ~ 8 fields per night  can be done in ~ 400 clear nights (bright time) 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 10

12. HERMES: GA Survey In order to maximise chemical “resolution”, select four wavelength regions to allow abundance measurements from a range of 7 independent element groups: 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 11 Light elements (Na,Al) Mg Other alpha-elements (Ca, Si, Ti) Fe and Fe-peak elements Light s-process elements (Sr,Zr) Heavy s-process elements (Ba) r-process (Eu) ChannelWavelengths Blue4708 – 4893Å Green5649 – 5873Å Red6481 – 6739Å IR7590 – 7890Å

13. HERMES: GA Survey 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 12 Expected Fractional Contribution from Galactic Components DwarfGiant Thin disk0.580.20 Thick disk0.100.07 Halo0.020.03 Old disk dwarfs will be seen out to distances of about 1 kpc Disk giants ___________________________________ 5 kpc Halo giants ___________________________________ 15 kpc

14. HERMES: GA Survey Ultimate goal of the archaeology program is unravelling the star formation history of the thin and thick disk and the halo via chemical tagging Interim data products include: –distribution of stars in [position, velocity, chemical] space for a million stars –distribution of Fe/H, α/Fe and X/Fe for enormous samples of stars from thin and thick disks, halo –detailed abundance gradients in each component –chemical and kinematical correlations in inner and outer thick and thin disks 7-year timeline for survey (including construction) 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 13

15. (Some) Other Science with HERMES: The Spectrograph Substructure in the halo and studies of closest Milky Way satellites Magellanic Clouds Skymapper Follow-up ISM in the Milky Way + Local Group Globular and open clusters Stellar astrophysics Time Domain: Stellar binarity and variability, planet searches, etc., etc. 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 14

16. For V ~ 14, HERMES will achieve S/N ~ 100 in 1 hour; for V ~ 17, S/N ~ 10 in 1 hour (S/N ~ 20 in 4 hours) For R ~ 28,000 spectra with S/N ~ 10, [M/H] and velocities can be determined with errors of ~0.12 dex and <1 km/s, respectively 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 15 Carney et al. 1987

17. HERMES and the Halo V~17 reaches the TRGB out to ~100 kpc, HB out to ~ 25 kpc HERMES will be able to directly measure [Fe/H], [α/H], etc. for these stars, as well as precision RVs 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 16 Mochejska et al. 2001 TRGB: ~ 100 kpc HB: ~ 25 kpc

18. Satellites, Streams, Substructure Surviving (~bound) satellites, stellar streams and substructure in general should be most apparent in galaxy halos (lowρ stellar, long τ dyn ) Substructure should be detectable in multi-dimensional (spatial, kinematic, chemical) parameter space 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 17 Bullock, Johnston, Font et al.

19. HERMES and the Halo Streams and faint satellites in the halo are typically extremely diffuse and extend over large areas of the sky Thanks to the FOV and ~400 fibres of 2dF, HERMES will be ideally suited for studies of halo substructure 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 18 UMa II Zucker+ 2006 Belokurov+ 2006

20. HERMES and the Magellanic Clouds A magnitude limit of V ~ 17 reaches the RGB in the LMC (upper RGB in the SMC) HERMES will make it possible to study the chemical and dynamical evolution of the MCs in unprecedented detail 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 19 Alcock et al. 2000 LMC

21. HERMES and Skymapper Skymapper initial 5-second survey  input photometry and astrometry for main HERMES survey Symbiosis: Skymapper  targets for spectroscopy, HERMES  precision abundances and radial velocities for Skymapper discoveries 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 20

22. HERMES in the Gaia Era Gaia: astrometry and spectroscopy  parallaxes, proper motions, RVs HERMES + Gaia: combine 6-D phase space info with detailed abundances to disentangle the formation history of the Milky Way (e.g., “real” phase-space substructures vs. artefacts) 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 21 Helmi and de Zeeuw 2000 Brown+ 2005

23. HERMES Recap New spectrograph for AAT + 2DF: ~400 fibres, 2° FOV 4 arms, R (Δλ/λ)~28000, ~ 200 - 300Å per arm (total ~ 1000Å); higher res capability (R~50,000) S/N ~ 100 @ V ~ 14 in 1 hour (S/N ~ 10 @ V ~ 17 in 1 hour) First light: late 2012, full operations: mid-2013 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 22

24. Summary High efficiency, high spectral resolution, wide field of view and massive multiplexing will make HERMES a uniquely powerful tool for disentangling the complex formation and evolution of the Milky Way and its components 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 23

25. In conjunction with data from other projects (e.g., Skymapper and Gaia) HERMES has the potential to revolutionise our understanding of the Milky Way’s history – and of galaxy formation in general 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 24 Summary

26. JOBS! JOBS! JOBS! Do you have what it takes to join Team Hermes? Are you: Smart? Motivated? Within 3 years of receiving your PhD? 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 25

27. HERMES Super Science Fellowships 3 x 3-year Super Science Fellowship postdocs starting 2011, at Macquarie University, in beautiful Sydney, Australia Very competitive salary and generous research budget Linked PhD scholarships with supervisory opportunities 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 26

28. Science with HERMES 28 – 29 September 2010 ATNF Lecture theatre Epping, Sydney, Australia www.aao.gov.au/HERMES 22 July 2010 27 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

29. 22 July 2010Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing 28