Chemodynamics of galaxies with resolved stellar populations now

Chemo-dynamics of galaxies with resolved stellar populations: now and then Giuseppina Battaglia Instituto de Astrofisica de Canarias, Tenerife Karachentsev et al. 2014 Credit: ESO/H. H. Heyer Credit: ESO/L. Calçada

Individual Red Giant Branch stars & Ca. II triplet - Tracers of galaxy intermediate resolution evolution from recent epochs back spectroscopy Gallart et al 2005 to the oldest times - Bright! Brightest feature in old stellar pop. - KINEMATICS: Velocities accurate to a few km/s - CHEMISTRY: Calibration Ca. T EW – [Fe/H] OVER A WIDE [Fe/H] RANGE (e. g. Rutledge et al. 1997, Cole et al. 2004, Battaglia et al. 2008, Starkenburg et al. 2010, Carrera et al. 2013 etc. ) Starkenburg et al. 2010 At low/ intermediate resolution (R ~ 3000 -6000) -> short(ish) exposure times:

Dwarf galaxies: even the simplest galaxies are complex Credits: M. Mateo Mc. Connachie 2012

Dwarf galaxies: even the simplest galaxies are complex Early-types Late-types Milky Way Dwarf spheroidals & VLT/FLAMES Phoenix transition NGC 6822 dwarf type & irregular & VLT/FORS VLT/MUSE Credits: M. Mateo Mc. Connachie 2012 Figure credits: Mc. Connachie 2012; Mario Mateo; Stephen Leshin; Local Group Survey Team; Lowell Observatory

Spatial variations of metallicity properties [Fe/H] from Ca. T lines calculated using the calibration from Starkenburg et al. 2010 Sculptor d. Sph (Tolstoy et al. 2004, Battaglia et al. 2008) Sextans d. Sph (Battaglia et al. 2011) 180 mem 600 mem rcore rtid Fornax d. Sph (Battaglia et al. 2006, 2008) Phoenix d. T (Kacharov, Rejkuba, Battaglia et al. in prep) 850 mem rcore rtid (see also e. g. Koch et al. 2006; Faria et al. 2007; Gullieuszik et al. 2009; Kirby et al. 2011) 180 mem rcore rtid

A “centrifugal barrier” mechanism? Leaman et al. 2013 Non-rotating Pegasus Phoenix Rotating Less massive (Mdm ~ 5 x 10^8 Msun) Mored. Irrs massive (Mdm ~ 3 x 10^9 Msun) Interesting to analyze and d. Ts as a function of mass and angular momentum; we are starting to populate the parameter space Schroyen et al. 2011

Multiple stellar components & dark matter: Sculptor (found also in Fornax and Sextans) MR -Kinematics of multiple stellar components prefer a cored profile to a cuspy one (Battaglia et al. 2008) MP -Not possible to make a distinction when treating the stars as 1 component -Results confirmed by other groups (Walker & Peñarrubia 2011; Amorisco & Evans 2012) Line-of-sight velocity dispersion profiles: “Metal-rich” [Fe/H] > -1. 5 Battaglia et al. (2008) Cored _____ Cusped - - “Metal-poor” [Fe/H] < -1. 7 No selection in [Fe/H]

Large number statistics is important ! VLT/FLAMES: Tolstoy et al. 2004, Battaglia et al. 2006, 2008, 2011, Starkenburg et al. 2010 Sculptor Fornax VLT/FORS: Tolstoy et al. 2001 Much wider range of [Fe/H] values within each galaxy than previously thought > this should give indications on the galaxy’s capability to retain its ISM -> potential well Presence of (rare) extremely metal-poor stars (see also Kirby et al. 2009, Frebel 2010, Tafelmeyer et al. 2010)

Spatially extended vs centrally concentrated samples

Spatially extended vs centrally concentrated samples Kirby et al. 2010, 2011

In the E-ELT era: Simulations within the Design Reference Mission Can we carry out similar observations out to the distance of the Virgo cluster using the E-ELT + HARMONI ? Credit: ESO/L. Calçada GENERAL AIM: [Fe/H] (± 0. 3 dex) and line-of-sight velocities (± 20 km/s for large galaxies, 5 km/s for dwarfs) from the Ca. T lines for about 1000 individual RGB stars in a “reasonable” observing time out to a few Mpc (Virgo? )

Generalities Objects and Distance range: ~1 Mpc (LG: NGC 205) Tip of the RGB in I-mag at ~: 20. 6 4 Mpc (Cen. A) 23. 9 17 Mpc (Virgo: M 87) 27. 2 Constant SFH (14 -12 Gyr) [Fe/H] = -1. 7 (MP) [Fe/H] = -1. 0 (MR) Spectrum star 1 + spectrum star 2 + …… + …. Star N + sky contribution & technical effects = Integrated spectrum Target RGB + stellar background from mock stellar population yielding a given surf. brightness (code by J. Liske) Spectra from the Munari et al. 2005 synthetic spectral library

Instrumental and technical adopted characteristics Diameter = 42 m (to be updated to 39 m) INSTRUMENT (adapted to HARMONI) • • • R = 4000 & 9000 Instantaneous field-of-view = 5” x 10” Spatial pixel (spaxel) size = 40 mas x 40 mas 35% instrument throughput 18% Encircled Energy in one spaxel in Iband TECHNICAL PARAMETERS • • Exposure time (20 min to 50 h) Site (Paranal-like; High&Dry) Mirror coating (bare Al; Ag/Al) Zenith & seeing = 0. 8”

Centaurus A • [Fe/H]=-1 ; target RGB 0. 5 mag below tip (I= 24. 4) • No crowding at these distances at the explored mag. • High&Dry; Ag/Al • R=4000&9000 2 Re ≈ 12 kpc 5 Re ≈ 30 kpc (23. 7 mag/arcsec^2) (26. 3 mag/arcsec^2) 5”

Centaurus A [Fe/H] and vel requirements fulfilled in 1 h considering the flux in only 1 spaxel! EE= 18%: -> seeing 0. 6” If EE=9% -> exp. time x 4 In reality we will recover the flux over multiple spaxels Numb RGB stars per pointing (I <= tip – 0. 5 mag): 1 Re = 75 2 Re = 16 3. 5 Re= 4 -> well feasible to observe 1000 target RGBs

M 87/Virgo • [Fe/H]=-1 ; target RGB at the tip (I= 27. 2) • Some crowding already at 4 Re (22. 2 mag/arcsec^2) • Critical to explore options to use more spaxels (ala Kammann et al. ) • Most likely observations limited to a few pointings

Summary • Even small systems like dwarf galaxies are complex (e. g. metallicity gradients, large range of [Fe/H], multiple-stellar components, rotation etc. ). • Large number statistics and spatial coverage are important (even more so for larger/more complex galaxies) • Intermediate res. Spectroscopy of large numbers of individual RGB stars in the n. IR Ca. T region with EELT+HARMONI: Well feasible out to a few Mpc (e. g. Cen. A) Much more time consuming at the distance of Virgo

Caveats • • Simulations assumed “perfect” data reduction. Only 1 -D spectra simulated. No effect of airmass; just one seeing Only one spaxel considered and for completely resolved stars Restricted range of SFHs/target types (RGBs)/only Ca. T Next Steps • • • HARMONI simulator (DATA CUBES) Explore options to deal with crowding and extract flux from more spaxels (e. g. as Kammann et al. ) Actual IFU observations of Local Group systems

Resolved stellar population studies with IFUs: NGC 6822 d. Irr @ VLT/MUSE (PI: Mendel) D= 490 kpc Star-forming and gas-rich MV= -15. 2 Pointing: Surf. Bright V ~ 20. 8 mag/arcsec^2 ~ half-light radius “BVI” MUSE image 1’ x 1’, 0. 2”/pixel (0. 3”-0. 4” FWHM) R = 1700 (480 nm) – 3600 (930 nm) 1. 5 h on source

Resolved stellar population studies with IFUs: NGC 6822 d. Irr @ VLT/MUSE (PI: Mendel) Data reduction mostly with ESO pipeline Source extraction/sky-subtraction with Pampel. MUSE (Kammann et al. 2013) 192 sources 288 sources