Galaxy Evolution at High Resolution: The New View of the Milky Way's Disc. Jo Bovy (University of Toronto; Canada Research Chair)

Galaxy Evolution at High Resolution: The New View of the Milky Way's Disc Jo Bovy (University of Toronto; Canada Research Chair)

WHY THE MILKY WAY?

WHY THE MILKY WAY? Detailed measurements of position, velocity, age, abundances [X/ H] of individual stars

WHY THE MILKY WAY? Detailed measurements of position, velocity, age, abundances [X/ H] of individual stars Detailed chemical evolution and star-formation history: gas inflows/outflows, SNe yields, IMF, Detailed measurements of spatial and kinematical distributions of stellar populations of different abundances, ages Archaeological record: metal-poor stars & early galaxy formation, chemical tagging

MILKY WAY DISK MASS BUDGET Double-exponential-ish with h Z ~ 350 pc, h R ~ 2-3 kpc (e.g., Juric et al. 2008, Bovy & Rix 2013)

MILKY WAY DISK MASS BUDGET Double-exponential-ish with h Z ~ 350 pc, h R ~ 2-3 kpc (e.g., Juric et al. 2008, Bovy & Rix 2013) Mass ~ 5.5 x 10 10 M sun, maximal or close to it (Bovy & Rix 2013)

MILKY WAY DISK MASS BUDGET Double-exponential-ish with h Z ~ 350 pc, h R ~ 2-3 kpc (e.g., Juric et al. 2008, Bovy & Rix 2013) Mass ~ 5.5 x 10 10 M sun, maximal or close to it (Bovy & Rix 2013) See Bland-Hawthorn & Gerhard (2016, ARAA) for most up-todate Galactic parameters

Bland-Hawthorn & Gerhard (2016)

MILKY WAY DISK MASS BUDGET: SOLAR NEIGHBORHOOD Solar neighborhood inventories from counting (McKee et al. 2015, Flynn et al. 2006) and dynamics (e.g., Kuijken & Gilmore 1989, Zhang et al. 2013) McKee et al. (2015)

MILKY WAY DISK MASS BUDGET: SOLAR NEIGHBORHOOD McKee et al. (2015)

MILKY WAY DISK MASS BUDGET: SOLAR NEIGHBORHOOD McKee et al. (2015) > Mass dominated by massive stellar disk

OBSERVABLES AND SURVEYS

OBSERVABLES AND SURVEYS Individual-star measurements > trace populations

OBSERVABLES AND SURVEYS Individual-star measurements > trace populations (x,v) > combination of astrometry (celestial positions, parallaxes, proper motions), photometric distances, spectroscopic line-of-sight velocities > Gaia [Fe/H], [a/fe], [C/Fe], : medium-to-high resolution surveys: SEGUE, RAVE now, DESI, PFS future Individual abundances for many elements [X/Fe]: high-resolution spec. surveys: APOGEE, GALAH, Gaia-ESO now, 4MOST, WEAVE, MOONS, MSE, future

CHEMICAL EVOLUTION IN THE MILKY WAY

THE ABUNDANCE PLANE IN THE SOLAR NEIGHBORHOOD Kinematically- and (~)metallicity unbiased sample of ~1,000 stars within ~50 pc from the Sun Improves on abundant earlier work by Fuhrmann, Prochaska, Reddy, Bensby, et al. Adibeykan et al. (2012) Blue: high-velocity stars Red: low-velocity stars

METALLICITY DISTRIBUTION IN THE SOLAR NEIGHBORHOOD Peaked at solar, but broad and largely symmetric Casagrande et al. (2011) High-[Fe/H] tail hard to explain with a one-zone model Vertical gradient about -0.3 dex/kpc, radial gradient about -0.1 dex/kpc Largely flat behavior w/ Z when split by [α/fe] Calculated from Bovy et al. (2012); see also Schlesinger et al. (2014)

APOGEE HI-RES BEYOND THE Infrared H-band spectrograph SOLAR NEIGHBORHOOD high resolution (R ~ 22,500) S/N > 100 / pixel (J-Ks)0 > 0.5, H <~ 13.8 vlos, logg, Teff, + 15 abundances (C,N,O,Na,Mg,Al,Si,S,K,Ca,Ti,V,Mn,Fe,Ni) APOGEE-1survey complete: 500k high-res spectra for ~150,000 stars PI: Steve Majewski, + many people

Majewski et al. (2016) Credit: Michael Hayden, Background: R. Hurt, JPL-Caltech, NASA

ABUNDANCE DISTRIBUTION Nidever, Bovy et al. (2014) Solar neighborhood [α/fe] vs. [Fe/H] similar to previous high-resolution studies, e.g., HARPS sample (Adibekyan et al. 2012) <~ 50 pc Data from Adibekyan et al. (2012) Haywood et al. (2013)

ABUNDANCE DISTRIBUTION Nidever, Bovy et al. (2014) Solar neighborhood [α/fe] vs. [Fe/H] similar to previous high-resolution studies, e.g., HARPS sample (Adibekyan et al. 2012)

ABUNDANCE DISTRIBUTION Nidever, Bovy et al. (2014) 6 kpc 8 kpc 10 kpc

ABUNDANCE DISTRIBUTION Nidever, Bovy et al. (2014) 6 kpc 8 kpc 10 kpc High-[α/Fe] sequence remarkably uniform throughout the Galaxy

ABUNDANCE DISTRIBUTION Nidever, Bovy et al. (2014) 6 kpc 8 kpc 10 kpc High-[α/Fe] sequence remarkably uniform throughout the Galaxy Increasing radii = high-[α/ Fe] sequence disappears

LARGER-SCALE ABUNDANCE DISTRIBUTION Hayden, Bovy, et al. (2015) ~whole disk!

CHEMICAL EVOLUTION [α/fe] (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION Early: SNe II: rich in α elements and ironpeak [α/fe] (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION Early: SNe II: rich in α elements and ironpeak [α/fe] (O,Mg,Si,S, Ca,Ti) SNe Ia only produce iron-peak elements and drive down the relative abundance of α to Fe [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION [α/fe] (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION [α/fe] Efficiency of star formation (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION [α/fe] (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION [α/fe] Efficiency of outflows (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION [α/fe] (O,Mg,Si,S, Ca,Ti) [Fe/H] (Fe,Ni)

HIGH-ALPHA SEQUENCE Nidever, Bovy et al. (2014) Star formation Early evolution of the Disk Gas outflows

HIGH-ALPHA SEQUENCE Nidever, Bovy et al. (2014) Star formation Early evolution of the Disk Star formation and gas in/outflow must have been very similar everywhere at R < 10 kpc within the first ~4 Gyr of the Disk s existence Gas outflows

METALLICITY DISTRIBUTION Hayden, Bovy, et al. (2015) Beyond the [α/fe] vs. [Fe/H] track, APOGEE can measure the MDF = p([fe/h]) over the entire radial range of the disk

METALLICITY DISTRIBUTION Hayden, Bovy, et al. (2015) Beyond the [α/fe] vs. [Fe/H] track, APOGEE can measure the MDF = p([fe/h]) over the entire radial range of the disk Inner disk MDF (R 7 kpc) is negatively skewed in the way a one-zone model would be skewed

CHEMICAL EVOLUTION ~constant SFH N [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION ~constant SFH ~declining SFH (gas starved) N [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION Metallicity gradient N [Fe/H] (Fe,Ni) Hayden, Bovy, et al. (2015)

CHEMICAL EVOLUTION: NON-CIRCULAR ORBITS N [Fe/H] (Fe,Ni)

CHEMICAL EVOLUTION: NON-CIRCULAR ORBITS+MIGRATION N [Fe/H] (Fe,Ni)

METALLICITY DISTRIBUTION Hayden, Bovy, et al. (2015) Same Rg, w/ velocity dispersion Rg diffusion, w/ velocity dispersion Radial trend of skewness is difficult to explain with simple chemical evolution and epicyclic blurring Migration of stars (or gas) over ~5 kpc is required to supply the metal-rich tail of the middle and outer disk MDFs (see Loebman et al. 2015 for a simulation)

< At formation Stars Today > Gas Loebman et al. (2016)

DISSECTING THE MILKY WAY S STELLAR POPULATIONS

IDENTIFYING DISK POPULATIONS (currently) impossible to identify single-stellar populations, but would like to get as close to that as possible Previously, populations were typically defined based on position or velocity (bad!) Even integrals of the motion likely change significantly over the lifetime of a star Surface abundance of stars don t change * over the stellar lifetime and uniform for SSPs Natural to define populations based on abundances (~chemical tagging)

MONO-ABUNDANCE POPULATIONS vertical profile: scale height radial profile: scale length thick short thin long Bovy et al. (2012abc) using SDSS/SEGUE data

MONO-ABUNDANCE POPULATIONS velocity dispersion: vertical vertical profile: detailed distribution of mass warm cool Bovy et al. (2012abc) using SDSS/SEGUE data

APOGEE MAPS Bovy et al. (2016a)

Combination of Green et al. (2015), Marshall et al. (2006), Drimmel et al. (2003) see Bovy et al. (2016b)

APOGEE MAPS: RADIAL PROFILE Bovy et al. (2016a) old younger

APOGEE MAPS: RADIAL PROFILE Bovy et al. (2016a)? old younger

APOGEE MAPS: VERTICAL PROFILE Bovy et al. (2016a) old younger

MAPS AND THE OVERALL DISK Bovy & Rix (2013) Rd ~ 2.15 kpc

MAPS AND THE OVERALL DISK

MAPS AND THE OVERALL DISK Bird et al. (2013)

MAPS AND THE OVERALL DISK Bird et al. (2013) Minchev et al. (2015) Martig et al. (2014)

SEGUE/APOGEE MAPS: IMPLICATIONS

SEGUE/APOGEE MAPS: IMPLICATIONS High-alpha / old disk: centrally-concentrated, pure exponential > MW formed inside-out

SEGUE/APOGEE MAPS: IMPLICATIONS High-alpha / old disk: centrally-concentrated, pure exponential > MW formed inside-out Low-alpha donuts: strong correspondence between [Fe/ H] and (birth) radius > equilibrium chemical evolution over last ~6-8 Gyr Flaring of low-alpha, cool populations > consistent with radial migration

MILKY WAY EVOLUTION

MILKY WAY EVOLUTION Great progress in the last few years

MILKY WAY EVOLUTION Great progress in the last few years Radial migration: good theoretical underpinnings, shown to be important in various ways

MILKY WAY EVOLUTION Great progress in the last few years Radial migration: good theoretical underpinnings, shown to be important in various ways Disk evolution appears to have been very quiescent over the last ~10 Gyr, with no large fraction of stars accreted by mergers Disk formed inside-out, and was likely turbulent at redshift ~ 2

AGES

AGES FROM PARALLAXES AND ISOCHRONES Many methods, but difficult to measure Traditional method: turn-off stars have widely different magnitudes at different ages > abs. mag. from parallaxes give tance uncertainties 1. ages Uncertainties ~ 1 Gyr Figure 3: Overview of Gaia data: shown are isochrones of solar metallicity in absolute magnitude in the Gaia G bandpass and effective temperature. The isochrones are colorcoded by the maximum distance for which Gaia will deliver 10% dis- In the context of this proposal their most important characteristics are: Turnoff/subgiant stars: Isochrones of different ages for these stars separate widely (shown are isochrones of 1, 2, 3, 5, 7, 10, and 12.6Gyr), allowing ages to be estimated up to 3kpc without age bias. Redclump and giant stars: The intrinsic brightness of these stars means that they can be traced throughout the whole extent of the disk in regions of low extinction and Gaia can measure their proper mo- Possible with Gaia over ~3-4 kpc in the disk > limited tions everywhere. Similar method for giants + surface gravity > APOGEE+Gaia tal abundances. (Feuillet, Bovy et al. 2016) MG 2 0 2 4 6 8 3.9 Red clump stars 10% distance uncertainty 3.8 3.7 log T eff Turn off/ subgiant stars 3.6 Giants Main sequence APOGEE can 0 1 2 3 4 5 6 7 8 9 10 additionally measure their line-ofsight velocities and detailed elemen- Maximum distance for 10% distance uncertainty (kpc) Main-sequence stars: Millions of main-sequence stars will have accurate positions and velocities from Gaia out to 2kpc and many millions more beyond can be studied using photometric distances. 3.2 The Gaia revolution: ages and precise phase-space coordinates for millions of stars 3.5 25/63 10/25 4/10 2/4 1/2 0/1 3.4 distance for G = 15/17 (kpc)

AGES IN THE ABUNDANCE PLANE IN THE SOLAR NEIGHBORHOOD Haywood et al. (2013) Data from Adibekyan et al. (2012) Haywood et al. (2013) measured ages for ~400 turnoff/sub-giant stars in the Adibekyan sample See also earlier work by Edvardsson et al. (1993) and Nordstrom et al. (2004)

AGES IN THE ABUNDANCE PLANE IN THE SOLAR NEIGHBORHOOD [α/fe] vs. age (mostly) confirms to expectations Large [Fe/H] scatter at a given age for stars younger than ~8 Gyr Haywood et al. (2013) Well-defined age-[fe/h] relation for high-alpha stars (filled blue dots)

NEW METHODS: AGES FOR GIANTS

NEW METHODS: AGES FOR GIANTS Giants: mass+z > main-sequence lifetime > age

NEW METHODS: AGES FOR GIANTS Giants: mass+z > main-sequence lifetime > age Asteroseismology: oscillations in the convective surface layer related to density and surface-gravity > mass and radius

NEW METHODS: AGES FOR GIANTS Giants: mass+z > main-sequence lifetime > age Asteroseismology: oscillations in the convective surface layer related to density and surface-gravity > mass and radius Sub-giants/giants: deepening of convective layer leads to C & N mixing and partial C burning > C/N decreases Mass-dependence of this effect: C/N > mass > age (Masseron & Gilmore 2015, Martig et al. 2016) Martig et al. (2015)

Can start to look at age distributions of large samples: RC in APOGEE (Martig et al. 2016): High-[a/Fe] sequence is > 8 Gyr Low-[a/Fe] sequence younger than 8 Gyr; no metallicity trend

AGE ISSUES All methods have large, non-symmetric uncertainties on the ages: sub-giants ~1 Gyr, giants ~3 Gyr > Need to deal with this: Hierarchical modeling (Feuillet et al. 2016) < Feuillet et al. (2016) > Systematics not well-understood, esp. in newer C/N methods, need more empirical and theoretical work to understand these Giants are age-biased, so recovering underlying age distribution requires stellar models, IMF

CONCLUSIONS Exciting time for Milky Way studies with much new data on the way

CONCLUSIONS Exciting time for Milky Way studies with much new data on the way Now have abundance patterns over the entire radial range of the disk

CONCLUSIONS Exciting time for Milky Way studies with much new data on the way Now have abundance patterns over the entire radial range of the disk Chemical tracks (Nidever et al. 2014, Hayden et al. 2015): Early evolution of the Milky Way disk uniform Metallicity distribution functions (Hayden et al. 2015): Change in skew from negative (inner) to positive (outer) > radial migration Spatial decomposition in metallicity/age reveals stellar donuts: [Fe/H] > birth radius

MILKY WAY EVOLUTION

REPORT CARD: MW DISK EVOLUTION Satellite interaction (Quinn et al. 1993, Abadi et al. 2003, ) Radial migration (Sellwood & Binney 2002, Schoenrich & Binney 2009, ) State of SF gas (Bournaud et al. 2009, Stinson et al., Bird et al. 2013, ) Gas outflows low [α/fe] high [α/fe]

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No high [α/fe] > few

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No Yes high [α/fe] > few

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No Yes high [α/fe] > few No*

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No Yes high [α/fe] No No*

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No Yes cold high [α/fe] No No* warm

REPORT CARD: MW DISK EVOLUTION Satellite interaction Radial migration State of SF gas Gas outflows low [α/fe] No Yes cold High high [α/fe] No No* warm Low