A state-of-the-art analysis of the dwarf irregular galaxy NGC 6822

Fusco, F.; Buonanno, R.; Hidalgo, Sebastián L.; Aparicio, A.; Pietrinferni, A.; Bono, G.; Monelli, M.; Cassisi, S.

doi:10.1051/0004-6361/201323075

Cited by 17 publications

(12 citation statements)

References 32 publications

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“…); however, the same explanation seems not to be valid for the intermittent bursts of SFH seen in the past 1-2 Gyr in these galaxies, though those events are less strong than the older star forming events. Fusco et al (2014) determined the SFH of NGC 6822 in 6 fields at different distances from the centre, out to 4 kpc. Their shapes differ significantly from each other and there is no unambiguous signature of a drop at a common time.…”

Section: Relation To the Milky Waymentioning

confidence: 99%

Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Battaglia,

Taibi,

Thomas

et al. 2021

Preprint

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Aims. We perform a comprehensive determination of the systemic proper motions of 74 dwarf galaxies and dwarf galaxy candidates in the Local Group based on Gaia early data release 3. The outputs of the analysis for each galaxy, including probabilities of membership, will be made publicly available. The analysis is augmented by a determination of the orbital properties of galaxies within 500 kpc. Methods. We adopt the flexible Bayesian methodology presented by McConnachie & Venn (2020), which takes into account the location of the stars on the sky, on the colour-magnitude diagram and on the proper motion plane. We apply some modifications, in particular to the way the colour-magnitude diagram and spectroscopic information are factored in, e.g. by including stars in several evolution phases. The bulk motions are integrated in three gravitational potentials: two where the Milky Way is treated in isolation and has a mass 0.9 & 1.6 ×10 12 M and the time-varying potential by Vasiliev et al. ( 2021), which includes the infall of a massive Large Magellanic Cloud (LMC). Results. We are able to determine bulk proper motions for 73 systems, and we consider reliable 66 of these measurements. For the first time, systemic motions are presented for galaxies out to a distance of 1.4 Mpc, in the NGC 3109 association. The inclusion of the infall of a massive LMC significantly modifies the orbital trajectories of the objects, with respect to orbit integration in static Milky Way-only potentials, and leads to 6 galaxies being likely associated to the LMC, 3 possibly associated and 1 recently captured object. We discuss the results of the orbit integration in the context of the relation of the galaxies to the system of Milky Way satellites, implications for the too-big-to-fail problem, impact on star formation histories, and tidal disruption.

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Section: Relation To the Milky Waymentioning

confidence: 99%

Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Battaglia,

Taibi,

Thomas

et al. 2021

Preprint

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“…The SFH of NGC 6822 will be presented by using LPV stars as a tracer of the SFH of the galaxy. Figure 1, left panel, shows the CMD which is over-plotted isochrones by Marigo et al (2017) with a distance modulus of 23.51 ± 0.051 mag and interstellar extinction of A V = 0.77 (Whitelock et al, 2013), and also Z = 0.0007 based on the result of Fusco et al (2014), who is reported in a range of 0.0001 < Z < 0.01.…”

Section: Discussion and On-going Workmentioning

confidence: 99%

From Evolved Stars to the Formation and Evolution of NGC 6822

Taefi

Saremi

Javadi

2020

ComBAO

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NGC6822, an isolated dwarf irregular galaxy (dIrr), due to close distance, apparent isolation, and easy observation, has been always selected as a desired candidate for studying star formation and galactic evolution, without the strong gravitational influences of other systems. To derive the SFH of NGC6822, the method mentioned by Javadi et al. (2011) is used which is based on theoretical models coupled with color-magnitude diagrams (CMDs) by using directly the long period variable (LPV) stars which are mostly asymptotic giant branch (AGB) stars at their very late stage of evolution, as well as more massive red super-giant (RSG) stars according to their significant role to study the star formation rate (SFR). To calculate the SFH in the bar of the galaxy, we use more than 600 LPV stars from different catalogs of variable stars that two of the most important are Whitelock et al. (2013) and Letarte et al. (2002) that they reported the main part of the LPVs and the Carbon stars, respectively, Patrick et al. (2015) announced the RSG stars. Understanding the star formation history of NGC 6822 plays an important role in comparing the galaxy history evolution with other nearby dwarf galaxies as well as studying the nature of the evolving population of galaxies which were detected in deep redshift surveys.

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“…Previous studies (e.g. Fusco et al 2014) yielded evidence that there are stars older than 10 Gyr in NGC 6822. Based on the presence of the old stellar populations, the observed values of gas-phase oxygen abundance and gas mass fraction are compared to predicted values in the universe at present (t = 13.80 Gyr).…”

Section: Chemical Evolution Modelsmentioning

confidence: 95%

Star formation and gas flow history of a dwarf irregular galaxy traced by gas-phase and stellar metallicities

Fukagawa

2019

Monthly Notices of the Royal Astronomical Society

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Studying the evolution of dwarf galaxies can provide insights into the characteristics of systems that can act as building blocks of massive galaxies. This paper discusses the history of star formation and gas flows (inflow and outflow) of a dwarf irregular galaxy in the Local Group, NGC 6822, from the viewpoint of gas-phase and stellar chemical abundance. Gas-phase oxygen abundance, stellar metallicity distribution and gas fraction data are compared to chemical evolution models in which continuous star formation and gas flows are assumed. If the galaxy is assumed to be a closed or an accretion-dominated system where steeper stellar initial mass functions are allowed, the observed gas-phase oxygen abundance and gas fraction can be explained simultaneously; however metallicity distributions predicted by the models seem to be inconsistent with the observed distribution, which suggests that the star formation, gas flows and/or chemical enrichment are more complex than assumed by the models. When NGC 6822 is assumed to be a system dominated by outflow, the observed values of gas-phase oxygen abundance and gas fraction can be explained, and the metallicity distributions predicted by some of the models are also roughly consistent with the observed distribution in the metallicity range of −2.0 [Fe/H] −0.5. It should be noted that this result does not necessarily mean that the accretion of gas is completely ruled out. More observables, such as chemical abundance ratios, and detailed modelling may provide deeper insight into the evolution of the system.

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A state-of-the-art analysis of the dwarf irregular galaxy NGC 6822

Cited by 17 publications

References 32 publications

Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud

From Evolved Stars to the Formation and Evolution of NGC 6822

Star formation and gas flow history of a dwarf irregular galaxy traced by gas-phase and stellar metallicities

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