Discovery of Latent Star Formation in the Extended H i Gas around the Local Group Dwarf Irregular Galaxy NGC 6822

2003 ◽  
Vol 590 (1) ◽  
pp. L17-L20 ◽  
Author(s):  
Yutaka Komiyama ◽  
Sadanori Okamura ◽  
Masafumi Yagi ◽  
Hisanori Furusawa ◽  
Mamoru Doi ◽  
...  
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Irregular Galaxy ◽  
Ngc 6822

scholarly journals Massive young stellar objects in the Local Group irregular galaxy NGC 6822 identified using machine learning

2021 ◽  
Vol 507 (4) ◽  
pp. 5106-5131
Author(s):  
David A Kinson ◽  
Joana M Oliveira ◽  
Jacco Th van Loon
Keyword(s):  
Machine Learning ◽  
Star Formation ◽  
Local Group ◽  
Point Sources ◽  
Asymptotic Giant Branch ◽  
Supervised Machine Learning ◽  
Young Stellar Objects ◽  
Irregular Galaxy ◽  
Stellar Objects ◽  
Ngc 6822

ABSTRACT We present a supervised machine learning methodology to classify stellar populations in the Local Group dwarf-irregular galaxy NGC 6822. Near-IR colours (J − H, H − K, and J − K), K-band magnitudes and far-IR surface brightness (at 70 and 160 $\mu$m) measured from Spitzer and Herschel images are the features used to train a Probabilistic Random Forest (PRF) classifier. Point-sources are classified into eight target classes: young stellar objects (YSOs), oxygen- and carbon-rich asymptotic giant branch stars, red giant branch and red supergiant stars, active galactic nuclei, massive main-sequence stars, and Galactic foreground stars. The PRF identifies sources with an accuracy of ∼ 90 per cent across all target classes rising to ∼96 per cent for YSOs. We confirm the nature of 125 out of 277 literature YSO candidates with sufficient feature information, and identify 199 new YSOs and candidates. Whilst these are mostly located in known star-forming regions, we have also identified new star formation sites. These YSOs have mass estimates between ∼15 and 50 M⊙, representing the most massive YSO population in NGC 6822. Another 82 out of 277 literature candidates are definitively classified as non-YSOs by the PRF analysis. We characterize the star formation environment by comparing the spatial distribution of YSOs to those of gas and dust using archival images. We also explore the potential of using (unsupervised) t-distributed stochastic neighbour embedding maps for the identification of the same stellar population classified by the PRF.

The Local Group Dwarf Irregular Galaxy NGC 6822.III. The Recent Star Formation History

1996 ◽  
Vol 112 ◽  
pp. 2596 ◽  
Author(s):  
C. Gallart ◽  
A. Aparicio ◽  
G. Bertelli ◽  
C. Chiosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History ◽  
Ngc 6822

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

2019 ◽  
Vol 491 (2) ◽  
pp. 1759-1770
Author(s):  
Nao Fukagawa
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Gas Flow ◽  
Building Blocks ◽  
Gas Flows ◽  
Chemical Abundance ◽  
Irregular Galaxy ◽  
Oxygen Abundance ◽  
History Of ◽  
Ngc 6822

ABSTRACT 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.

scholarly journals Stars at Low Metallicity in Dwarf Galaxies

2008 ◽  
Vol 4 (S255) ◽  
pp. 310-317
Author(s):  
Eline Tolstoy ◽  
Giuseppina Battaglia ◽  
Andrew Cole
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Wide Field ◽  
Irregular Galaxy ◽  
First Stars ◽  
Field Spectroscopy ◽  
Low Metallicity

AbstractDwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the recent target of deep HST/ACS imaging (Cole et al. 2007) and the Sculptor dwarf spheroidal, which has been the target of significant wide field spectroscopy with VLT/FLAMES (Battaglia 2007).

scholarly journals Planetary nebulae as tracers of the kinematic structure of the starburst galaxy IC 10

2011 ◽  
Vol 7 (S283) ◽  
pp. 368-369
Author(s):  
Denise R. Gonçalves ◽  
Ana M. Teodorescu ◽  
Alan Alves-Brito ◽  
Roberto H. Méndez ◽  
Laura Magrini
Keyword(s):  
Star Formation ◽  
Kinematic Analysis ◽  
Local Group ◽  
Stellar Populations ◽  
Starburst Galaxy ◽  
Kinematic Structure ◽  
Irregular Galaxy ◽  
Tidal Interactions ◽  
Ic 10 ◽  
The Galaxy

AbstractThe Local Group dwarf irregular galaxy IC 10 is the nearest starburst galaxy (at 725 kpc) and presents extended and complex HI kinematics. It is believed that IC 10 is still experiencing an intense and very recent burst of star formation, likely triggered by infalling gas from an extended envelope which is counter-rotating with respect to the galaxy proper rotation. In this contribution we summarize our preliminary results (Gonçalves et al. 2011, in prep.) obtained by performing a kinematic analysis of the PN population of IC 10. Our aim is to explore the kinematic connection of its intermediate to old stellar populations with that obtained from HI observations. Some PNe were found at large galactocentric distances and could therefore represent a trace of past tidal interactions.

scholarly journals Not even wrong: A philosophical, historical and ultimately a scientific inquiry into the Schmidt Law

2016 ◽  
Vol 11 (S321) ◽  
pp. 37-39
Author(s):  
Barry F. Madore ◽  
Erika K. Carlson
Keyword(s):  
Star Formation ◽  
Scientific Inquiry ◽  
Closed Loop ◽  
Local Group ◽  
Active Regions ◽  
High Mass ◽  
Ob Stars ◽  
Novel Approach ◽  
Two Phases ◽  
Ngc 6822

AbstractWe introduce a novel approach to interpreting the well-known spatial correlation of gas densities with on-going star formation. Treated as a closed-loop process involving two physically distinct phases the data can be subdivided into regions that are active and those that are quiescent. The active regions can be distinguished by the presence of high-mass, short-lived, but recently-formed OB stars; the quiescent regions are marked by an absence of these stars and they are considered to be recovering from the last star-formation event and are re-collapsing. The relative (areal) frequencies of those two phases are directly proportional to the relative timescales. For four Local Group galaxies, NGC 6822, the Large & Small Magellanic Clouds, and M33, the cloud assembly/collapse timescales are all found to be monotonically decreasing power-law functions of density, with as yet to be explained differences.

scholarly journals Outskirts of Local Group Dwarf Galaxies Revealed by Subaru Hyper Suprime-Cam

2016 ◽  
Vol 11 (S321) ◽  
pp. 25-27
Author(s):  
Yutaka Komiyama
Keyword(s):  
Stellar Population ◽  
Local Group ◽  
Dwarf Galaxies ◽  
High Spatial Resolution ◽  
Ccd Camera ◽  
High Sensitivity ◽  
Irregular Galaxy ◽  
Ursa Minor ◽  
Ngc 6822 ◽  
Shed Light

AbstractLocal Group galaxies are important targets since their stellar populations can be resolved, and their properties can be investigated in detail with the help of stellar evolutionary models. The newly-built instrument for the 8.2m Subaru Telescope, Hyper Suprime-Cam (HSC), which has a 1 Giga pixel CCD camera with 1.5 degrees field of view, is the best instrument for observing Local Group galaxies. We have carried out a survey for Local Group dwarf galaxies using HSC aiming to shed light on the outskirts of these galaxies. The survey covers target galaxies out beyond the tidal radii down to a depth unexplored by previous surveys. Thanks to the high spatial resolution and high sensitivity provided by the Subaru Telescope, we are able to investigate properties such as spatial distribution and stellar population from the very center of galaxies to the outskirts. In this article, I will show results for the dwarf irregular galaxy NGC 6822 and the dwarf spheroidal galaxy Ursa Minor.

scholarly journals Hierarchical clustering in the Local Group dwarf galaxy NGC 6822

2009 ◽  
Vol 5 (S266) ◽  
pp. 538-538
Author(s):  
S. Schmeja ◽  
D. A. Gouliermis ◽  
R. S. Klessen ◽  
W. J. G. de Blok ◽  
F. Walter
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Minimum Spanning Tree ◽  
Dwarf Galaxy ◽  
Nearest Neighbour ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ngc 6822 ◽  
Hierarchy Of Structures

AbstractStar formation appears to be clumped into a hierarchy of structures, from giant molecular clouds down to individual cores and clusters, which are often hierarchical themselves, showing significant substructure. This has been demonstrated for our Galaxy through the application of sophisticated statistical methods, in particular the nearest-neighbour density and the minimum spanning tree (MST), to different star-forming regions. Here we present our analysis of clustered star formation as demonstrated through the detection of structures of young stellar populations in the dwarf star-forming galaxy NGC 6822.

Sign in / Sign up

Export Citation Format

Share Document