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 (27)

• Array Programming with NumPy
• Modules for Experiments in Stellar Astrophysics (MESA)
• The Dartmouth Stellar Evolution Database
• An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology
• Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
• 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 AIMSS Project I: Bridging the Star Cluster - Galaxy Divide
• 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
• 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
• Reaching the End of the White Dwarf Cooling Sequence in NGC 6791
• Exploring the consequences of pairing algorithms for binary stars
• Probing the Faintest Stars in a Globular Star Cluster
• The State-of-the-Art HST Astro-Photometric Analysis of the core of ωCentauri. III. The Main Sequence's Multiple Populations Galore
• MARCS model atmospheres
• 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
• 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
• The Mass Function of omega Centauri down to 0.15 M_s
• Hunting for Brown Dwarfs in the Globular Cluster M4: 2nd epoch HST NIR observations
• The HST Large Programme on NGC 6752. III. Detection of the Peak of the White Dwarf Luminosity Function
• A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of $\omega$ Centauri
• A closer look at the $pp$-chain reaction in the Sun: Constraining the coupling of light mediators to protons

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