The Pristine Inner Galaxy Survey (PIGS) III: carbon-enhanced metal-poor stars in the bulge

Abstract

The most metal-deficient stars hold important clues about the early build-up and chemical evolution of the Milky Way, and carbon-enhanced metal-poor (CEMP) stars are of special interest. However, little is known about CEMP stars in the Galactic bulge. In this paper, we use the large spectroscopic sample of metal-poor stars from the Pristine Inner Galaxy Survey (PIGS) to identify CEMP stars ([C/Fe] > +0.7) in the bulge region and to derive a CEMP fraction. We identify 96 new CEMP stars in the inner Galaxy, of which 62 are very metal-poor ([Fe/H] < -2.0); this is more than a ten-fold increase compared to the seven previously known bulge CEMP stars. The cumulative fraction of CEMP stars in PIGS is $42_{-13}^{+14}\%$ for stars with [Fe/H] < -3.0, and decreases to $16_{-3}^{+3}\%$ for [Fe/H] < -2.5 and $5.7_{-0.5}^{+0.6}\%$ for [Fe/H] < -2.0. The PIGS inner Galaxy CEMP fraction for [Fe/H] < -3.0 is consistent with the halo fraction found in the literature, but at higher metallicities the PIGS fraction is substantially lower. While this can partly be attributed to a photometric selection bias, such bias is unlikely to fully explain the low CEMP fraction at higher metallicities. Considering the typical carbon excesses and metallicity ranges for halo CEMP-s and CEMP-no stars, our results point to a possible deficiency of both CEMP-s and CEMP-no stars (especially the more metal-rich) in the inner Galaxy. The former is potentially related to a difference in the binary fraction, whereas the latter may be the result of a fast chemical enrichment in the early building blocks of the inner Galaxy.

arXiv comment15 pages, 9 figures, accepted for publication in MNRAS

References in corpus (102)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• On the variation of the Initial Mass Function
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• The Pan-STARRS1 Surveys
• Near-Field Cosmology with Metal-Poor Stars
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• The ACS Survey of Galactic Globular Clusters. XII. Photometric Binaries along the Main-Sequence
• ULySS: A Full Spectrum Fitting Package
• A Spectroscopic Study of the Ancient Milky Way: F- and G-Type Stars in the Third Data Release of the Sloan Digital Sky Survey
• First-generation black-hole-forming supernovae and the metal abundance pattern of a very iron-poor star
• The early star generations: the dominant effect of rotation on the CNO yields
• SkyMapper Southern Survey: First Data Release (DR1)
• The Anglo-Australian Observatory's 2dF Facility
• The Most Metal-Poor Stars. II. Chemical Abundances of 190 Metal-Poor Stars Including 10 New Stars With [Fe/H] < -3.5
• The Binary Frequency Among Carbon-Enhanced, s-Process Rich, Metal-Poor Stars
• ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way
• Carbon-Enhanced Metal-Poor Star Frequencies in the Galaxy: Corrections for the Effect of Evolutionary Status on Carbon Abundances
• 4MOST: Project overview and information for the First Call for Proposals
• Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
• The Pristine survey I: Mining the Galaxy for the most metal-poor stars
• New ATLAS9 And MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• J-PLUS: The Javalambre Photometric Local Universe Survey
• The Optical-Infrared Extinction Curve and its Variation in the Milky Way
• Segue 1: An Unevolved Fossil Galaxy from the Early Universe
• The Most Metal-Poor Stars. IV. The Two Populations With [Fe/H] < -3.0
• A strong case for fast stellar rotation at very low metallicities
• Chemodynamical history of the Galactic Bulge
• Performance of AAOmega: the AAT multi-purpose fibre-fed spectrograph
• The Southern Photometric Local Universe Survey (S-PLUS): improved SEDs, morphologies and redshifts with 12 optical filters
• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Bright Metal-Poor Stars from the Hamburg/ESO Survey. I. Selection and Follow-up Observations from 329 Fields
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
• Binarity in Carbon-Enhanced Metal-Poor stars
• The role of binaries in the enrichment of the early Galactic halo. III. Carbon-enhanced metal-poor stars -- CEMP-s stars
• Carbon-enhanced metal-poor stars: the most pristine objects?
• Abundance Profiling of Extremely Metal-Poor Stars and Supernova Properties in the Early Universe
• s-Process in Low Metallicity Stars. I. Theoretical Predictions
• Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way
• Center-to-Limb Variation of Solar 3-D Hydrodynamical Simulations
• Numerical Simulations of Thermohaline Convection: Implications for Extra-Mixing in Low-Mass RGB Stars
• The role of binaries in the enrichment of the early Galactic halo. II. Carbon-Enhanced Metal-Poor Stars - CEMP-no stars
• The EMBLA Survey -- Metal-poor stars in the Galactic bulge
• Carbon-enhanced metal-poor stars in dwarf galaxies
• The [Fe/H], [C/Fe], and [alpha/Fe] distributions of the Bootes I Dwarf Spheroidal Galaxy
• An Extremely Carbon-rich, Extremely Metal-poor Star in the Segue 1 System
• SkyMapper Filter Set: Design and Fabrication of Large Scale Optical Filters
• The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal
• The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge
• Pristine Dwarf-Galaxy Survey I: A detailed photometric and spectroscopic study of the very metal-poor Draco II satellite
• Ba stars and other binaries in first and second generation stars in globular clusters
• Binarity among CEMP-no stars: an indication of multiple formation pathways?
• Carbon-Enhanced Metal-Poor Stars: CEMP-s and CEMP-no Sub-Classes in the Halo System of the Milky Way
• The Pristine Survey IV: Approaching the Galactic metallicity floor with the discovery of an ultra metal-poor star
• Metal-poor stars towards the Galactic bulge - a population potpourri
• Constraining Metallicity-dependent Mixing and Extra Mixing using [C/N] in Alpha-Rich Field Giants
• The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge
• Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods
• The Pristine Survey -- VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates
• The depletion of carbon by extra mixing in metal-poor giants
• Galactic Archeology with the AEGIS Survey: The Evolution of Carbon and Iron in the Galactic Halo
• The SkyMapper DR1.1 Search for Extremely Metal-Poor Stars
• The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime
• Very Metal-poor Stars in the Outer Galactic Bulge Found by the Apogee Survey
• The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars
• Pristine IX: CFHT ESPaDOnS Spectroscopic Analysis of 115 Bright Metal-Poor Candidate Stars
• J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINX
• MARCS model atmospheres
• Modelling the observed properties of carbon-enhanced metal-poor stars using binary population synthesis
• The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a Bimodal Bulge?
• The incidence of binaries in Globular Cluster stellar populations
• The Pristine Inner Galaxy Survey (PIGS) II: Uncovering the most metal-poor populations in the inner Milky Way
• Chemistry of the Most Metal-poor Stars in the Bulge and the z > 10 Universe
• Carbon and oxygen in metal-poor halo stars
• The Photometric Metallicity and Carbon Distributions of the Milky Way's Halo and Solar Neighborhood from S-PLUS Observations of SDSS Stripe 82
• The contribution of N-rich stars to the Galactic stellar halo using APOGEE red giants
• The Most Metal-Poor Stars. V. The CEMP-no Stars in 3D and Non-LTE
• The Pristine Dwarf-Galaxy survey - II. In-depth observational study of the faint Milky Way satellite Sagittarius II
• The COMBS Survey -- II. Distinguishing the Metal-Poor Bulge from the Halo Interlopers
• Spectroscopic Validation of Low-Metallicity Stars from RAVE
• Chemical Cartography. I. A Carbonicity Map of the Galactic Halo
• WHT follow-up observations of extremely metal-poor stars identified from SDSS and LAMOST
• The Pristine survey -- XII: Gemini-GRACES chemo-dynamical study of newly discovered extremely metal-poor stars in the Galaxy
• Stellar metallicities from SkyMapper photometry I: A study of the Tucana II ultra-faint dwarf galaxy
• The R-Process Alliance: Spectroscopic Follow-up of Low-Metallicity Star Candidates from the Best & Brightest Survey
• The COMBS survey I: Chemical Origins of Metal-Poor Stars in the Galactic Bulge
• The [α/Fe]-[Fe/H] relation in the E-MOSAICS simulations: its connection to the birth place of globular clusters and the fraction of globular cluster field stars in the bulge
• The Pristine Dwarf-Galaxy survey -- III. Revealing the nature of the Milky Way globular cluster Sagittarius II
• Chemical Cartography. II. The Assembly History of the Galactic Stellar Halo Traced by Carbon-Enhanced Metal-Poor Stars
• A new sample of southern radio galaxies: Host galaxy masses and star-formation rates
• Using the Multi-Object Adaptive Optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre
• The Most Metal-poor Stars in the Inner Bulge
• The Pristine survey II: a sample of bright stars observed with FEROS
• 4MOST Consortium Survey 3: Milky Way Disc and Bulge Low-Resolution Survey (4MIDABLE-LR)

Cited by in corpus (23)

• On the inconsistency of [C/Fe] abundances and the fractions of carbon-enhanced metal-poor stars among various stellar surveys
• The Three-Phase Evolution of the Milky Way
• The Pristine Inner Galaxy Survey (PIGS) V: a chemo-dynamical investigation of the early assembly of the Milky Way with the most metal-poor stars in the bulge
• Chemo-Dynamically Tagged Groups of CEMP Stars in the Halo of the Milky Way. I. Untangling the Origins of CEMP-$s$ and CEMP-no Stars
• Carbon-Enhanced Metal-Poor star candidates from BP/RP Spectra in $Gaia$ DR3
• Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($[Fe/H]\lesssim -3$) Regime
• Hunting for C-rich long-period variable stars in the Milky Way's bar-bulge using unsupervised classification of Gaia BP/RP spectra
• The energy distribution of the first supernovae
• Enrichment by Extragalactic First Stars in the Large Magellanic Cloud
• Information content of BP/RP spectra in Gaia DR3
• Constructing the Milky Way Stellar Halo in the Galactic Center by Direct Orbit Integration
• Predicting metallicities and carbon abundances from Gaia XP spectra for (carbon-enhanced) metal-poor stars
• The Pristine Inner Galaxy Survey (PIGS) VII: a discovery of the first inner Galaxy CEMP-r/s star
• On the dearth of C-enhanced metal-poor stars in the Galactic bulge
• The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy
• The Pristine Inner Galaxy Survey (PIGS) X. Probing the early chemical evolution of the Sagittarius dwarf galaxy with carbon abundances
• The Pristine survey -- XX: GTC follow-up observations of extremely metal-poor stars identified from Pristine and LAMOST
• Where are the extremely metal-poor stars in the Milky Way and Andromeda? Expectations from TNG50
• A method for identifying metal-poor stars with Gaia BP/RP spectra
• A second-generation star in a relic dwarf galaxy
• The Pristine Inner Galaxy Survey (PIGS) VI: Different vertical distributions between two DIBs at 442.8 nm and 862.1 nm
• Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. IV. Heavy Element Enhanced Stars
• The COMBS Survey -- III. The Chemodynamical Origins of Metal-Poor Bulge Stars