1 / 29

HERMES: Deciphering the Milky Way’s History

HERMES: Deciphering the Milky Way’s History. Daniel Zucker with Gayandhi de Silva and the HERMES team. HERMES: Introduction. HERMES: H igh E fficiency and R esolution M ulti- E lement S pectrograph

asher
Download Presentation

HERMES: Deciphering the Milky Way’s History

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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) Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  3. HERMES Basics • 4 arms with VPH gratings and 4k2CCDs • 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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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” Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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”) Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Freeman & Bland-Hawthorn 2002, Bland-Hawthorn & Freeman 2004, De Silva+ 2009 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

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

  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 106 (!) 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) Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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: • 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) Channel Wavelengths Blue 4708 – 4893Å Green 5649 – 5873Å Red 6481 – 6739Å IR 7590 – 7890Å Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  13. HERMES: GA Survey Expected Fractional Contribution from Galactic Components Dwarf Giant Thin disk 0.58 0.20 Thick disk 0.10 0.07 Halo 0.02 0.03 Old disk dwarfs will be seen out to distances of about 1 kpc Disk giants ___________________________________ 5 kpc Halo giants ___________________________________ 15 kpc Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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) Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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. Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  16. HERMES with Fainter Stars • 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 Carney et al. 1987 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 TRGB: ~ 100 kpc HB: ~ 25 kpc Mochejska et al. 2001 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

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

  19. HERMES and the Halo UMa II • 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 Belokurov+ 2006 Zucker+ 2006 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  20. HERMES and the Magellanic Clouds LMC • 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 Alcock et al. 2000 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  22. Helmi and de Zeeuw 2000 Brown+ 2005 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) Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

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

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

  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 Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

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

  29. Daniel Zucker LAMOST Milky Way Workshop // KIAA, Beijing

More Related