The nuclear star cluster and nuclear stellar disc of the Milky Way: Different stellar population and star formation history

Abstract

The Milky Way's nuclear stellar disc (NSD) and nuclear star cluster (NSC) are the main features of the Galactic centre. Nevertheless, their observation is hampered by the extreme source crowding and high extinction. Hence, their relation and formation scenario are not fully clear yet. We aim at detecting the stellar populations from the NSC and the NSD along the line-of-sight towards the NSC, and assess whether they have different stellar populations and star formation histories. We analysed the colour-magnitude diagram, $K_s$ vs. $H-K_s$, of a region of $8.2^{\prime }\times 2.8^{\prime }$ centred on the NSC, and detected two different stellar groups with different extinctions. We studied their red clumps to find the features associated to each of the stellar populations. We obtained that the two groups of stars correspond to the NSD and the NSC, and found that they have significantly different stellar populations and star formation histories. We detected a double red clump for the NSD population, in agreement with previous work, whereas the NSC presents a more complex structure well fitted by three Gaussian features. We created extinction maps to analyse the extinction variation between the detected stellar groups. We found that the high-extinction layer varies on smaller scales (arc-seconds), and that there is a difference of $A_{K_s}\sim 0.6$\,mag between both extinction layers. Finally, we obtained that the distance towards each of the stellar populations is compatible with the Galactic centre distance, and found some evidence of a slightly closer distance for the NSD stars ($\sim 360\pm 200$\,pc).

arXiv commentAccepted for publication in ApJ. 13 pages, 10 figures

References in corpus (42)

• Scikit-learn: Machine Learning in Python
• Array Programming with NumPy
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Improving PARSEC models for very low mass stars
• PARSEC evolutionary tracks of massive stars up to $350M_{\odot }$ at metallicities 0.0001$\le Z\le$0.04
• Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• The Nuclear Bulge of the Galaxy. III. Large-Scale Physical Characteristics of Stars and Interstellar Matter
• Mapping the Three-Dimensional Density of the Galactic Bulge with VVV Red Clump Stars
• The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge
• Interstellar Extinction Law in the J, H, and Ks Bands toward the Galactic Center
• Quantifying the Coexistence of Massive Black Holes and Dense Nuclear Star Clusters
• Constraining the thermally-pulsing asymptotic giant branch phase with resolved stellar populations in the Small Magellanic Cloud
• Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud
• Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
• StarFinder: an IDL GUI based code to analyze crowded fields with isoplanatic correcting PSF fitting
• Early formation and recent starburst activity in the nuclear disc of the Milky Way
• The Milky Way's nuclear star cluster: Old, metal-rich, and cuspy
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars
• The red clump absolute magnitude based on revised Hipparcos parallaxes
• GALACTICNUCLEUS: A high angular resolution $JH{K}_s$ imaging survey of the Galactic Centre. I. Methodology, performance, and near-infrared extinction towards the Galactic Centre
• Red clump stars and Gaia: Calibration of the standard candle using a hierarchical probabilistic model
• GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre II. First data release of the catalogue and the most detailed CMDs of the GC
• New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging
• Magnetically Confined Interstellar Hot Plasma in the Nuclear Bulge of our Galaxy
• OGLE-III Detection of the Anomalous Galactic Bulge Red Giant Branch Bump: Evidence of Enhanced Helium Enrichment
• The Gaia DR2 parallax zero point: Hierarchical modeling of red clump stars
• The Milky Way's nuclear stellar disc: A dynamically cool and metal-rich component formed from the Central Molecular Zone?
• Holographic Imaging of Crowded Fields: High Angular Resolution Imaging with Excellent Quality at Very Low Cost
• The inner two degrees of the Milky Way. Evidence of a chemical difference between the Galactic Center and the surrounding inner bulge stellar populations
• Jeans modelling of the Milky Way's nuclear stellar disc
• Star formation history and metallicity in the Galactic inner bulge revealed by the red giant branch bump
• GALACTICNUCLEUS: A high-angular-resolution $JH{K}_s$ imaging survey of the Galactic centre. IV. Extinction maps and de-reddened photometry
• GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre III. Evidence for wavelength dependence of the extinction curve in the near-infrared
• Variability of the near-infrared extinction curve towards the Galactic centre
• The Quintuplet Cluster: Extended Structure and Tidal Radius
• The globular clusters-stellar haloes connection in early type galaxies
• Distance to three molecular clouds in the central molecular zone

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• The Origin of Stars in the Inner 500 Parsecs in TNG50 Galaxies
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• Evidence of Deep Mixing in IRS 7, a Cool Massive Supergiant Member of the Galactic Nuclear Star Cluster
• Smooth kinematic and metallicity gradients reveal that the Milky Way's nuclear star cluster and disc might be part of the same structure
• The LEGARE Project. I. Chemical evolution model of the Nuclear Stellar Disc in a Bayesian framework
• Chemical analysis of the Milky Way's Nuclear Star Cluster: Evidence for a metallicity gradient
• The Galactic Center with Roman
• Self-consistent modelling of the Milky Way's Nuclear Stellar Disc
• Demonstration of Plate Analysis, an algorithm for precise relative astrometry
• The contribution to Galactic Centre γ-ray excess from cluster-born millisecond pulsars. Constraints from direct N-body simulations
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