The Chemical Impact of Stellar Mass Loss Rosemary Wyse Johns Hopkins University Gerry Gilmore, John Norris, Mark Wilkinson, Vasily Belokurov, Sergei Koposov, Wyn Evans, Dan Zucker, Anna Frebel, David Yong

Elemental abundances Field stars and dwarf spheroidal members Field stars and dwarf spheroidal members Massive-star mass function (core-collapse SNe) Massive-star mass function (core-collapse SNe) Invariant Invariant Mixing in interstellar medium Mixing in interstellar medium Surprisingly efficient Surprisingly efficient Carbon-rich (single) stars at very low [Fe/H] Carbon-rich (single) stars at very low [Fe/H] But also carbon-normal ultra-metal-poor stars But also carbon-normal ultra-metal-poor stars

Elemental Abundances: beyond metallicity  Core collapse supernovae have progenitors > 8 M  and explode on timescales ~ 10 7 yr, less than typical duration of star formation  Main site of  -elements, e.g. O, Mg, Ti, Ca, Si  Low mass stars enriched by only Type II SNe show enhanced ratio of  -elements to iron, with value dependent on mass distribution of SNe progenitors – if well-mixed system, see IMF-average  Type Ia SNe produce very significant iron, on longer timescales, few x 10 8 – several yr (WD in binaries) after birth of progenitor stars <

Schematic [O/Fe] vs [Fe/H] Wyse & Gilmore 1993 Slow enrichment Low SFR, winds.. Fast IMF biased to most massive stars Self-enriched star forming region. Assume good mixing so IMF-average yields Type II only Plus Type Ia

Gibson 1998 Progenitor mass Ejecta Salpeter IMF (all progenitor masses) gives [  /Fe] ~ 0.4; Change of IMF slope of ~1 gives change in [  /Fe] ~ +0.3 (Wyse & Gilmore 92) IMF dependence due to different nucleosynthetic yields of Type II progenitors of different masses Kobayashi et al 2006

Elemental abundances in old stars Ruchti et al 2011,12 Thick disk extends to -2 dex, same enhanced [ α /Fe] as halo stars  same massive-star IMF, short duration of star formation  little scatter – fixed IMF, good mixing, down to [Fe/H] < -3 dex Stars from RAVE survey, candidate metal-poor disk, follow-up echelle data

 same massive-star IMF Bulge Matches Thick Disk  same massive-star IMF Gonzales et al 2011

Extended, low-rate star formation and slow enrichment with gas retention, leads to expectation of ~solar (or below) ratios of [  /Fe] at low [Fe/H], such as in LMC stars Smith et al 2003 Gilmore & Wyse 1991 Local disk Hiatus then burst Pompeia et al 2008 LMC: solid

dSphs vs. MWG abundances: SFH (from A. Koch, updates) Shetrone et al. (2001, 2003): 5 dSphs Letarte (2006): Fornax Sadakane et al. (2004): Ursa Minor Koch et al. (2006, 2007): Carina Monaco et al. (2005): Sagittarius Koch et al. (2008): Hercules Shetrone et al. (2008): Leo II Aoki et al. (2009): Sextans Frebel et al. (2009): Coma Ber, Ursa Major Hill et al. (in prep): Sculptor Boo I  ◊ Leo IV Scl  Norris et al 10 BooI       Gilmore et al; Frebel et al 10 Scl Simon et al 10 Leo IV

Same ‘plateau’ in [ α /Fe] in all systems at lowest metallicities Same ‘plateau’ in [ α /Fe] in all systems at lowest metallicities Type II enrichment only: massive-star IMF invariant, and apparently well-sampled/mixed Type II enrichment only: massive-star IMF invariant, and apparently well-sampled/mixed Stellar halo could form from any system(s) in which star- formation is short-lived, and inefficient so that mean metallicity kept low Stellar halo could form from any system(s) in which star- formation is short-lived, and inefficient so that mean metallicity kept low Star clusters, galaxies, transient structures… Star clusters, galaxies, transient structures… Complementary, independent age information that bulk of halo stars are OLD further constrains progenitors (e.g. Unavane, Wyse & Gilmore 1996) Complementary, independent age information that bulk of halo stars are OLD further constrains progenitors (e.g. Unavane, Wyse & Gilmore 1996)

M92 M15 Main sequence luminosity functions of UMi dSph and of globular clusters are indistinguishable.   Wyse et al 2002 HST star counts 0.3M  Star Counts: Invariant Low-Mass IMF UMi dSph stars have narrow range of ages, all old

Low-Mass Stellar MF in Bulge: Zoccali et al 2000 (M15) Matches local disk (Kroupa 2000) And M15 – which matches the UMi dSph: Low-mass IMF invariant wrt metallicity, time..

Stetson et al 2011 Carina dSph CMD Very extended, non-monotonic star formation history

Carina dSph – extended, bursty star formation history Carina data: bursts + inhomogeneous star formation Koch et al inc RW 2008Massive star IMF invariant

Lemasle et al 2012 Age estimates: younger indeed higher [ α/Fe]

A much simpler system: Bootes I ‘ultra-faint’ dwarf SDSS Discovery CMD (Belokurov et al, inc RW, 2006b) Subaru (Okamoto, PhD, 2010 ) M * ~ 4 x 10 4 M , dist ~ 65 kpc

Norris, RW et al 2010 Dwarf spheroidal galaxies have well-defined peaks, with low metallicity tails: self-enriched, from primordial gas? Then lost most baryons – M/L high. [Fe/H] distributions and radial dependence Very luminous globular cluster  lacks low-metallicity tail; most clusters do not self-enrich in Fe; Need enough compact baryons Segue 1, 7 stars 16 stars

Alpha Abundances: 8 stars in Boo I, VLT UVES 8 stars in Boo I, VLT UVES Double-blind analysis (Gilmore et al 2012) Double-blind analysis (Gilmore et al 2012)  minimal scatter Boo-119 is CEMP-no star; open dots are field CEMP CEMP-no star Segue 1-7 has [Mg/Fe] ~ 0.94 (Norris et al 2010)

Carbon-enhanced star in Segue 1 (triangles) and BooI (circles) No s-process plus high [Mg/Fe] Norris et al 2010a,b

Including data for Boo I stars from Lai et al 2011

[Fe/H] time ISM mixing scale             Two modes of enrichment? Unmixed, very early, enriched by individual supernovae from zero-metal stars? Unmixed, very early, enriched by individual supernovae from zero-metal stars? Extremely well mixed, fully sample massive-star IMF – minimal scatter in element ratios Extremely well mixed, fully sample massive-star IMF – minimal scatter in element ratios Boo I probably lost 90% of baryons – metals? Boo I probably lost 90% of baryons – metals?

Conclusions Lack of variations in elemental abundances probably produced by core-collapse supernovae argue for invariant massive-star IMF Lack of variations in elemental abundances probably produced by core-collapse supernovae argue for invariant massive-star IMF Star counts imply fixed low-mass IMF Star counts imply fixed low-mass IMF Overall patterns determined by star-formation history Overall patterns determined by star-formation history Small scatter implies well-mixed ISM Small scatter implies well-mixed ISM WHY? And HOW? WHY? And HOW?

Large Scale Flows Chemical evolution plus global star formation rates argue for gas replenishment Chemical evolution plus global star formation rates argue for gas replenishment High velocity clouds exist High velocity clouds exist Galactic Fountain Galactic Fountain Cold Flows from Cosmic Web Cold Flows from Cosmic Web Accretion from satellite galaxies (Magellanic Stream) Accretion from satellite galaxies (Magellanic Stream) Radial migration Radial migration

Boötes I M V ~ -6.3, M * ~ 4 x 10 4 M  (Kroupa IMF), distance of ~ 65kpc, half-light radius ~ 250pc (< dark matter scalelength?), central velocity dispersion ~ 3-6 km/s (?), derived (extrapolated) mass within half-light radius ~ M , M/L ~ 10 3, mean dark matter density ~ 0.1M  /pc 3 M V ~ -6.3, M * ~ 4 x 10 4 M  (Kroupa IMF), distance of ~ 65kpc, half-light radius ~ 250pc (< dark matter scalelength?), central velocity dispersion ~ 3-6 km/s (?), derived (extrapolated) mass within half-light radius ~ M , M/L ~ 10 3, mean dark matter density ~ 0.1M  /pc 3  collapse at redshift z > 10  collapse at redshift z > 10 Color-magnitude diagram consistent with old, metal- poor population, similar to classic halo globular cluster Color-magnitude diagram consistent with old, metal- poor population, similar to classic halo globular cluster More luminous dSph have very varied SFHs ~ ~ Belokurov et al 06; Gilmore et al 07; Martin et al 08; Walker et al 09; Okamoto et al 10

Getting the most from Flames on VLT: Bootes I field, ~1 half light radius FOV, 130 fibres, 12 x 45min integrations  Repeated observations allow detection of variability:  110 non-variable (giant) stars (< 1km/s) Analyse spectra in pixel space; Retain full covariance: map model spectra onto data, find ‘best’ match values of stellar parameters (gravity, metallicity, surface temperature) with a Bayesian classifier. Black: data r=19; red=model Koposov, et al (inc RW), 2011b

Previous literature value  (already reduced) Identify 37 members, based on line-of-sight velocity, metallicity and stellar gravity (should be giants, dwarfs will be foreground field halo stars) Koposov, et al (inc RW), 2011b

Field of Streams (and dots) SDSS data, 19< r< 22, g-r < 0.4 colour-coded by mag (distance), blue (~10kpc), green, red (~30kpc) Belokurov et al (inc RW, 2006) Outer stellar halo is lumpy: but only ~15% by mass (total mass ~ 10 9 M  ) and dominated by Sgr dSph stream  Segue 1  Boo I

Members well beyond the nominal half-light radius in both Stars more iron-poor than -3 dex (10 -3 solar) exist in both Extremely rare in field halo, membership very likely Very far out, parameters and velocity confirmed by follow-up:  Segue 1 is very extended! (as is Boo I) Both systems show a large spread in iron Implies dark halo for self-enrichment (cf Simon et al 2011, 6 stars in Segue 1, 7 in total) Norris, RW et al 2010 Wide-area spectroscopy Red: Segue 1Black: Boo I Geha et al І

Wyse & Gilmore 1992 Salpeter IMF slope: Scalo: -1.5 Matteucci for Bulge: -1.1

Chemical Abundances: Boo I & Segue 1 Spectroscopic surveys with the 2dF/AAΩ fibre-fed MOS; stars selected from SDSS to follow discovery CMD: wide-area mapping unique capability of 2dF Spectroscopic surveys with the 2dF/AAΩ fibre-fed MOS; stars selected from SDSS to follow discovery CMD: wide-area mapping unique capability of 2dF 400 fibres, 2-degree FOV, dual beam, chemical abundances from blue spectra, R ~ 5000, range Å. Membership based on radial velocity (to better than 10 km/s) and the derived values of stellar parameters Iron from calibration of Ca II K line (3933 Å, as field halo surveys, Beers et al 99 ), +/- 0.2 dex (Norris et al 08) Iron from calibration of Ca II K line (3933 Å, as field halo surveys, Beers et al 99 ), +/- 0.2 dex (Norris et al 08) Carbon from synthesis of CH G-band, +/- 0.2 in Boo I and +/- 0.4 in Segue 1 (Norris et al 10) Carbon from synthesis of CH G-band, +/- 0.2 in Boo I and +/- 0.4 in Segue 1 (Norris et al 10) Follow-up UVES echelle data, [Fe/H] +/- 0.1dex; [C/Fe] for 1 star

Caveat: Segue 1 in very complex part of the Galaxy Caveat: Segue 1 in very complex part of the Galaxy Very flat (bimodal?) metallicity distribution, unlike other dwarf galaxies: contamination? Very flat (bimodal?) metallicity distribution, unlike other dwarf galaxies: contamination? Extended structure around it Extended structure around it Same distance and line-of-sight as Sgr stream, but different velocity (Niederste-Ostholt et al wrong orbit for Sgr stream) Same distance and line-of-sight as Sgr stream, but different velocity (Niederste-Ostholt et al wrong orbit for Sgr stream) Distance and velocity, line-of-sight match Orphan stream (Newberg et al 2010, Koposov et al inc RW 2011a) Distance and velocity, line-of-sight match Orphan stream (Newberg et al 2010, Koposov et al inc RW 2011a) What is the `300km/s stream’? What is the `300km/s stream’? Extremely wide-field mapping needed to be assured of status Extremely wide-field mapping needed to be assured of status

Segue 1 M V ~ -1.5, M * ~ 600 M , distance of ~25kpc, half-light radius ~ 30pc (?), velocity dispersion ~ 4 km/s (?), derived mass within half-light radius ~ 3 x 10 5 M  (?), M/L ~ 2000 (?), again DM ~ 0.1 M  /pc 3 and high collapse redshift M V ~ -1.5, M * ~ 600 M , distance of ~25kpc, half-light radius ~ 30pc (?), velocity dispersion ~ 4 km/s (?), derived mass within half-light radius ~ 3 x 10 5 M  (?), M/L ~ 2000 (?), again DM ~ 0.1 M  /pc 3 and high collapse redshift Superposed on Sgr tidal debris, close in distance and velocity (?), contamination likely (Niederste-Ostholt et al 09); unlikely ( Simon et al 2010) Again old, metal-poor population Again old, metal-poor population Belokurov et al. 07; Martin et al 08; Geha et al 09; Walker et al 09; Simon et al 2010