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Carbon-Enhanced Metal-Poor Carbon-Enhanced Metal-Poor (CEMP) stars: probes of(CEMP) stars: probes ofnucleosynthesis from the first nucleosynthesis from the first generation of stars generation of stars in the Universein the Universe

SDSS

Timothy C. BeersTimothy C. BeersNational Optical Astronomy National Optical Astronomy Observatory Observatory

First-generation objects of high mass presumably formed from First-generation objects of high mass presumably formed from metal-free gasmetal-free gas

Lived short lives (Myrs)Lived short lives (Myrs) ExplodedExploded Distributed (pre or post explosion) their nucleosynthetic productsDistributed (pre or post explosion) their nucleosynthetic products

Next-generation objects formed from the gas polluted by first-Next-generation objects formed from the gas polluted by first-generation objectsgeneration objects

A wider range of masses allowed, perhaps including stars with A wider range of masses allowed, perhaps including stars with main-sequence lifetimes > a Hubble timemain-sequence lifetimes > a Hubble time

Further star formation (Pop II) contributed additional material, Further star formation (Pop II) contributed additional material, and diluted the signatures of first/next-generation starsand diluted the signatures of first/next-generation stars

We should look for a characteristic set of abundance signatures We should look for a characteristic set of abundance signatures ONLY foundONLY found among the lowest metallicity starsamong the lowest metallicity stars

Although alternatives have been suggested (e.g., “sawtooth Although alternatives have been suggested (e.g., “sawtooth pattern”), the odd-even effect associated with explosions of pair-pattern”), the odd-even effect associated with explosions of pair-instability SNe, I would like to advocate for instability SNe, I would like to advocate for CARBON and CARBON and other light elementsother light elements

Expected SignaturesExpected Signatures

The Discovery of Carbon-Enhanced The Discovery of Carbon-Enhanced Metal-Poor (CEMP) StarsMetal-Poor (CEMP) Stars

Just How Common are These CEMP Just How Common are These CEMP Stars ? Stars ?

The The HK SurveyHK Survey of Beers and of Beers and colleagues revealed that colleagues revealed that MANY MANY low-[Fe/H] stars exhibit a large low-[Fe/H] stars exhibit a large overabundance of carbon overabundance of carbon relative to iron relative to iron (10s of CEMP (10s of CEMP stars)stars)

This realization has inspired This realization has inspired further searches for CEMP stars, further searches for CEMP stars, both in the both in the HK survey HK survey and the and the (then) newer (then) newer Hamburg/ESO Hamburg/ESO prism prism survey survey (100s of CEMP (100s of CEMP stars) stars)

And by And by SDSS/SEGUE-1/SEGUE-SDSS/SEGUE-1/SEGUE-22 (1000s of CEMP stars)(1000s of CEMP stars)

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Carbon-Enhanced Metal-Poor (CEMP) stars have Carbon-Enhanced Metal-Poor (CEMP) stars have been recognized to be an important stellar been recognized to be an important stellar component of the halo systemcomponent of the halo system

CEMP stars frequencies are:CEMP stars frequencies are: 20% for [Fe/H] < —2.520% for [Fe/H] < —2.5 30% for [Fe/H] < —3.0 EMP30% for [Fe/H] < —3.0 EMP 40% for [Fe/H] < —3.540% for [Fe/H] < —3.5 75% for [Fe/H] < —4.0 UMP75% for [Fe/H] < —4.0 UMP

But Why ? – But Why ? – Atmospheric/Progenitor or Population Atmospheric/Progenitor or Population Driven ?Driven ?

Carollo et al. (2012) suggest the latterCarollo et al. (2012) suggest the latter

Frequencies of CEMP Stars Frequencies of CEMP Stars Based on Stellar PopulationsBased on Stellar Populations

Exploration of Nature’s Exploration of Nature’s Laboratory for Neutron-Capture Laboratory for Neutron-Capture ProcessesProcesses

Beers & Christlieb ARAA (2005)

The UMP/HMP Stars are (Almost) ALL CEMP-no The UMP/HMP Stars are (Almost) ALL CEMP-no StarsStars

Aoki et al. (2007) demonstrated that the CEMP-no stars occur preferentially at lower [Fe/H] than the CEMP-s stars

About 80% of CEMP stars are CEMP-s or CEMP-r/s, 20% are CEMP-no

Global abundance patterns of CEMP-no stars incompatible with AGB models at low [Fe/H]

Carbon Enhancement Associated Carbon Enhancement Associated with s-process Patterns (Aoki et al. with s-process Patterns (Aoki et al. 2002)2002)

LP 625-44: [Fe/H] = -2.7; [C/Fe] = +2.0

LP 625-44 was the first s-process-rich MP star with Pb measured

Carbon Enhancement Associated with Carbon Enhancement Associated with r-process Patterns (CS 22892-052; r-process Patterns (CS 22892-052; McWilliam et al. 1995; Sneden et al. McWilliam et al. 1995; Sneden et al. 2000)2000)CS 22892-052: [Fe/H] = -3.1; [C/Fe] = +1.0

CS 22892-052 was the first highly r-process-rich MP star discovered

CEMP-no Stars are Associated with UNIQUE CEMP-no Stars are Associated with UNIQUE Light-Element Abundance Patterns (Aoki et al. Light-Element Abundance Patterns (Aoki et al. 2002)2002)

CS 29498-043: [Fe/H] = -3.8; [C/Fe] = +1.9

Harbingers of Things to Come!

Last but Definitely Least… Last but Definitely Least… (Christlieb et al. 2002; Frebel et al. (Christlieb et al. 2002; Frebel et al. 2005)2005)

HE 0107-5240 [Fe/H] = -5.3 [C/Fe] = +3.9HE 0107-5240 [Fe/H] = -5.3 [C/Fe] = +3.9

It is the SAME pattern among the light elements !

BD+44:493 – A 9BD+44:493 – A 9thth Magnitude Magnitude Messenger from the Early Messenger from the Early UniverseUniverse

Ito et al. (2009) report on discovery that BD+44 is Ito et al. (2009) report on discovery that BD+44 is an an [Fe/H] = —3.8, CEMP-no star, CEMP-no star

Light-element abundance patterns similar to those Light-element abundance patterns similar to those for other CEMP-no starsfor other CEMP-no stars

Previous RV monitoring by Carney et al. indicate no Previous RV monitoring by Carney et al. indicate no variation at levels > 0.5 km/s over variation at levels > 0.5 km/s over past 25 years

More detailed observations by Ito et al. (2013)More detailed observations by Ito et al. (2013)

Something You DonSomething You Don’’t Often t Often SeeSee

An Object of COSMOLOGICAL Significance with Diffraction Spikes

Abundance Pattern Abundance Pattern Compared to 25 MCompared to 25 Moo Mixing/Fallback ModelMixing/Fallback Model

Ito et al. (2013) : Note the low N, compared with some other CEMP-no stars with enhanced N

Radial Velocity Radial Velocity MonitoringMonitoring

Carney et al. (1986) + Ito et al. (2012)Carney et al. (1986) + Ito et al. (2012)

The rms variation over 25 years is 0.73 km/s !

Inference of Inner/Outer Halo Inference of Inner/Outer Halo Structure (Carollo et al. 2010)Structure (Carollo et al. 2010)

Follow-on of work from D. Carollo et al. (2007), demonstrating existence of inner/outer halo populations, based on 32,360 unique calibration stars from SDSS

Determination of velocity ellipsoids for thick disk, MWTD, inner, outer halos

Modeling of fractions of various components in local sample (d < 4 kpc)

Fractions of Fractions of ComponentsComponents

Velocity EllipsoidsVelocity Ellipsoids

Global CEMP Fraction and <[C/Fe]> vs Global CEMP Fraction and <[C/Fe]> vs [Fe/H][Fe/H](Carollo et al. 2012) analysis of SDSS/SEGUE Cal (Carollo et al. 2012) analysis of SDSS/SEGUE Cal StarsStars

Global variation shows smooth increase of f (CEMP) vs. [Fe/H]

Clear increase of <[C/Fe]> vs. [Fe/H]

Global CEMP Fraction vs. |Z|Global CEMP Fraction vs. |Z|

Clear increase of f (CEMP) with |Z| (not expected for single halo)

Inner/Outer Halo CEMP Inner/Outer Halo CEMP FractionsFractions

f (CEMP)OH ~ 2 x f (CEMP) IH <[C/Fe]> roughly constant IH/OH

(Carollo et al. 2012)

InterpretationInterpretation

Bottom LineBottom Line CEMP stars in the Galaxy likely have had multiple sources of carbon production

CEMP-s in AGB starsCEMP-no in massive (50-100 Mo) rapidly rotating MMP starsCEMP-no in intermediate (25-30 Mo) “faint” SNe

CEMP-no stars occur preferentially at the lowest metallicities, including the 3 of the 4 stars known with [Fe/H] < -4.5

CEMP stars are found in great number in the ultra-faint SDSS dwarf galaxies, some of which have low n-capture abundances

High-z DLA systems exhibit similar abundance patterns as CEMP-no stars

We have observed (!) the nucleosynthesis products of first generation stars (Pop III)

Fractions of CEMP-no and CEMP-s in the

Inner/Outer halo Carollo et al., in preparationCarollo et al., in preparation

Sample of 183 stars with high-resolution Sample of 183 stars with high-resolution spectroscopy obtained with Subaru and spectroscopy obtained with Subaru and other sources (Aoki et al. 2013; Norris et other sources (Aoki et al. 2013; Norris et al. 2013), including on the order of 50 al. 2013), including on the order of 50 CEMP starsCEMP stars

High resolution spectroscopy necessary to High resolution spectroscopy necessary to obtain the Barium signature of s-processobtain the Barium signature of s-process

Rapo > 15 kpc

IHP-OHP Memberships using Integrals of Motion

IHP-OHP Memberships using Integrals of Motion

OHP

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s-CEMP2 no-CEMP

no-CEMP2 s-CEMP

New CEMP + VMP Star Survey Summary

Placco, Beers, et al. have been using “bad weather” time on the Gemini N and S telescopes to search for NEW (formerly missed)

examples of CEMP and VMP stars chosen from the HK and HES candidates

Numerous examples of new CEMP stars found by targeting on the G-band strength of scanned HES stars

By taking advantage of the apparently strong correlation between large C over-abundances and declining [Fe/H], rather than on the weakness

of the CaII K line for metal weakness, and obtaining C information later from medium-res spectroscopic follow-up

Numerous examples of new VMP stars found by targeting on previously unobserved HK and HES candidates

CEMP survey recently completed (~ 800 spectra / ~200 new CEMP stars)

VMP survey just getting underway

High-resolution work (AAT, Magellan, VLT/X-Shooter) – Just Starting

[C/Fe] vs. [Fe/H] (Medium-Res Results)

Expansion of numbers of identified CEMP stars, in particular Expansion of numbers of identified CEMP stars, in particular with [F/eH] < —2.5, which include both CEMP-s and CEMP-with [F/eH] < —2.5, which include both CEMP-s and CEMP-no starsno stars

High-resolution follow-up spectroscopy of a core sample of High-resolution follow-up spectroscopy of a core sample of 100-200 CEMP stars, in order to assign classifications based 100-200 CEMP stars, in order to assign classifications based on heavy elements, and to determine CNO and other light on heavy elements, and to determine CNO and other light element abundanceselement abundances

Radial velocity monitoring of CEMP stars, in order to Radial velocity monitoring of CEMP stars, in order to determine binary nature, as well as characterize determine binary nature, as well as characterize correlations between chemical patterns and nature of the correlations between chemical patterns and nature of the detected binarydetected binary

An exciting time indeed !An exciting time indeed !

The Path ForwardThe Path Forward