The HST large programme on $\omega$ Centauri -- V. Exploring the Ultracool Dwarf Population with Stellar Atmosphere and Evolutionary Modelling

Abstract

Brown dwarfs can serve as both clocks and chemical tracers of the evolutionary history of the Milky Way due to their continuous cooling and high sensitivity of spectra to composition. We focus on brown dwarfs in globular clusters that host some of the oldest coeval populations in the galaxy. Currently, no brown dwarfs in globular clusters have been confirmed, but they are expected to be uncovered with advanced observational facilities such as JWST. In this paper we present a new set of stellar models specifically designed to investigate low-mass stars and brown dwarfs in $\omega$ Centauri -- the largest known globular cluster. The parameters of our models were derived from iterative fits to HST photometry of the Main Sequence members of the cluster. Despite the complex distribution of abundances and the presence of multiple Main Sequences in $\omega$ Centauri, we find that the modal colour-magnitude distribution can be represented by a single stellar population with parameters determined in this study. The observed luminosity function is well-represented by two distinct stellar populations having solar and enhanced helium mass fractions and a common initial mass function, in agreement with previous studies. Our analysis confirms that the abundances of individual chemical elements play a key role in determining the physical properties of low-mass cluster members. We use our models to draw predictions of brown dwarf colours and magnitudes in anticipated JWST NIRCam data, confirming that the beginning of the substellar sequence should be detected in $\omega$ Centauri in forthcoming observations.

References in corpus (98)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• The chemical composition of the Sun
• On the variation of the Initial Mass Function
• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• A Survey of Stellar Families: Multiplicity of Solar-Type Stars
• The Dartmouth Stellar Evolution Database
• Low Temperature Opacities
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• Models of Stars, Brown Dwarfs and Exoplanets
• Galactic Chemical Evolution: Hydrogen Through Zinc
• An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
• A high accuracy computed water line list
• Destruction of the Galactic Globular Cluster System
• Omega Centauri: The Population Puzzle Goes Deeper
• The ACS Survey of Galactic Globular Clusters. VII. Relative Ages
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results
• Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement
• An ACS Survey of Globular Clusters V: Star Catalog for Each Cluster
• Internal Dynamics of Globular Clusters
• Dynamical Evolution of the Mass Function of Globular Star Clusters
• Further Defining Spectral Type "Y" and Exploring the Low-mass End of the Field Brown Dwarf Mass Function
• Clouds and Chemistry: Ultracool Dwarf Atmospheric Properties from Optical and Infrared Colors
• Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
• The Deuterium-Burning Mass Limit for Brown Dwarfs and Giant Planets
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program
• Population Properties of Brown Dwarf Analogs to Exoplanets
• New Limits on an Intermediate Mass Black Hole in Omega Centauri: I. Hubble Space Telescope Photometry and Proper Motions
• A comparison of chemistry and dust cloud formation in ultracool dwarf model atmospheres
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared
• The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo Kinematics
• The AIMSS Project I: Bridging the Star Cluster - Galaxy Divide
• Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
• Dynamical Evolution and Spatial Mixing of Multiple Population Globular Clusters
• The Dependence of Brown Dwarf Radii on Atmospheric Metallicity and Clouds: Theory and Comparison with Observations
• The State-of-the-Art HST Astro-Photometric Analysis of the core of $\omega$ Centauri. I. The Catalog
• T Dwarfs and the Substellar Mass Function. I. Monte Carlo Simulations
• Cluster AgeS Experiment: The Age and Distance of the Globular Cluster omega Centauri Determined from Observations of the Eclipsing Binary OGLEGC17
• Pandeia: A Multi-mission Exposure Time Calculator for JWST and WFIRST
• No Energy Equipartition in Globular Clusters
• Radial distribution of the multiple stellar populations in omega Centauri
• The Parallax of Omega Centauri Measured from Gaia EDR3 and a Direct, Geometric Calibration of the Tip of the Red Giant Branch and the Hubble Constant
• A Definition for Giant Planets Based on the Mass-Density Relationship
• Reaching the End of the White Dwarf Cooling Sequence in NGC 6791
• The HST large programme on $\omega$ Centauri - II. internal kinematics
• The End of the White Dwarf Cooling Sequence in M4: an efficient approach
• The C+N+O abundance of Omega Centauri giant stars: implications on the chemical enrichment scenario and the relative ages of different stellar populations
• Inferring the Age of the Universe with Globular Clusters
• Spherically symmetric model atmospheres for low mass pre-Main Sequence stars with effective temperatures between 2000 and 6800 K
• The lithium depletion boundary and the age of the Hyades cluster
• Exploring the consequences of pairing algorithms for binary stars
• Hubble Space Telescope Observations of an Outer Field in Omega Centauri: A Definitive Helium Abundance
• Probing the Faintest Stars in a Globular Star Cluster
• Constraining the multiplicity statistics of the coolest brown dwarfs: binary fraction continues to decrease with spectral type
• Binary Formation Mechanisms: Constraints from the Companion Mass Ratio Distribution
• The State-of-the-Art HST Astro-Photometric Analysis of the core of ωCentauri. III. The Main Sequence's Multiple Populations Galore
• Temperatures and Metallicities of M dwarfs in the APOGEE Survey
• The Molecular Line Opacity of MgH in Cool Stellar Atmospheres
• Color--Magnitude Diagram and Luminosity Function of M4 Near the Hydrogen-Burning Limit
• A Large Sample Study of Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• The HST Large Program on Omega Centauri. I. Multiple stellar populations at the bottom of the main sequence probed in NIR-Optical
• MARCS model atmospheres
• Our Sun. IV. The Standard Model and Helioseismology: Consequences of Uncertainties in Input Physics and in Observed Solar Parameters
• Liquid metallic hydrogen and the structure of brown dwarfs and giant planets
• Reddening distribution across the center of the globular cluster Omega Centauri
• New insights on the Galactic Bulge Initial Mass Function
• Mass estimates from stellar proper motions: The mass of $\omega$ Centauri
• WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5: The First Extreme T-type Subdwarfs?
• The HST Large Programme on NGC6752. II. Multiple populations at the bottom of the main sequence probed in NIR
• The HST large programme on $\omega$ Centauri -- III. Absolute proper motion
• On the black hole content and initial mass function of 47 Tuc
• Globular cluster systems and galaxy formation
• Hot Horizontal Branch stars in omega Centauri: clues about their origin from the cluster Color Magnitude Diagram
• On the distance of the globular cluster M4 (NGC 6121) using RR Lyrae stars: II. Mid-infrared period-luminosity relations
• The State-of-the-Art HST Astro-Photometric Analysis of the core of $\omega$ Centauri. II. Differential-Reddening Map
• Exploring the outskirts of globular clusters: the peculiar kinematics of NGC 3201
• The Most Metal-poor Stars in Omega Centauri (NGC 5139)
• The HST large programme on omega Centauri -- IV. catalogue of two external fields
• Oxygen and Neon Abundances of B-Type Stars in Comparison with the Sun
• The Mass Function of omega Centauri down to 0.15 M_s
• HST observations of the metal rich globular clusters NGC6496 and NGC6352
• A Simple Dynamical Model for Omega Cen
• The HST Large Programme on NGC 6752. III. Detection of the Peak of the White Dwarf Luminosity Function
• Hunting for Brown Dwarfs in the Globular Cluster M4: 2nd epoch HST NIR observations
• A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of $\omega$ Centauri
• On the use of the main sequence knee (saddle) to measure globular cluster ages
• A closer look at the $pp$-chain reaction in the Sun: Constraining the coupling of light mediators to protons
• Brown Dwarfs as Galactic Chronometers

Cited by in corpus (7)

• Characterization of Population III Stars with Stellar Atmosphere and Evolutionary Modeling and Predictions of their Observability with the James Webb Space Telescope
• Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5$-$101002.3
• oMEGACat II -- Photometry and proper motions for 1.4 million stars in Omega Centauri and its rotation in the plane of the sky
• Beyond the Local Volume. II. Population Scaleheights and Ages of Ultracool Dwarfs in Deep HST/WFC3 Parallel Fields
• The stellar to sub-stellar masses transition in 47 Tuc
• New Way to Date Globular Clusters: Brown Dwarf Cooling Sequences
• JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit