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Post Info TOPIC: IC10
Blobrana


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Title: A kinematic study of planetary nebulae in the dwarf irregular galaxy IC10
Authors: Denise R. Gonçalves (OV/Universidade Federal do Rio de Janeiro), Ana M. Teodorescu (University of Hawaii), Alan Alves-Brito (Australian National University), Roberto H. Méndez (University of Hawaii), Laura Margini (INAF/Osservatorio Astrofisico di Arcetri)

We present positions, kinematics, and the planetary nebula luminosity function (PNLF) for 35 planetary nebulae (PNe) in the nearest starburst galaxy IC10 extending out to 3kpc from the galaxy's centre. We take advantage of the deep imaging and spectroscopic capabilities provided by the spectrograph FOCAS on the 8.2m Subaru telescope. The PN velocities were measured through the slitless-spectroscopy technique, which allows us to explore the kinematics of IC10 with high precision. Using these velocities, we conclude that there is a kinematic connection between the HI envelope located around IC10 and the galaxy's PN population. By assuming that the PNe in the central regions and in the outskirts have similar ages, our results put strong observational constraints on the past tidal interactions in the Local Group. This is so because by dating the PN central stars, we, therefore, infer the epoch of a major episode of star formation likely linked to the first encounter of the HI extended envelope with the galaxy. Our deep [OIII] images also allow us to use the PNLF to estimate a distance modulus of 24.1±0.25, which is in agreement with recent results in the literature based on other techniques.

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Blobrana


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Title: The chemical evolution of IC10
Authors: Jun Yin, Laura Magrini, Francesca Matteucci, Gustavo A. Lanfranchi, Denise R. Gonçalves, Roberto D. D. Costa
(Version v2)

Dwarf irregular galaxies are relatively simple unevolved objects where it is easy to test models of galactic chemical evolution. We attempt to determine the star formation and gas accretion history of IC10, a local dwarf irregular for which abundance, gas, and mass determinations are available. We apply detailed chemical evolution models to predict the evolution of several chemical elements (He, O, N, S) and compared our predictions with the observational data. We consider additional constraints such as the present-time gas fraction, the star formation rate (SFR), and the total estimated mass of IC10. We assume a dark matter halo for this galaxy and study the development of a galactic wind. We consider different star formation regimes: bursting and continuous. We explore different wind situations: i) normal wind, where all the gas is lost at the same rate and ii) metal-enhanced wind, where metals produced by supernovae are preferentially lost. We study a case without wind. We vary the star formation efficiency (SFE), the wind efficiency, and the time scale of the gas infall, which are the most important parameters in our models. We find that only models with metal-enhanced galactic winds can reproduce the properties of IC10. The star formation must have proceeded in bursts rather than continuously and the bursts must have been less numerous than ~10 over the whole galactic lifetime. Finally, IC10 must have formed by a slow process of gas accretion with a timescale of the order of 8 Gyr.

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Blobrana


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Posts: 131433
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Title: The Chemical Evolution of IC10
Authors: Jun Yin, Laura Magrini, Francesca Matteucci, Gustavo A. Lanfranchi, Denise R. Gonçalves, Roberto D. D. Costa

Dwarf irregular galaxies are relatively simple unevolved objects where it is easy to test models of galactic chemical evolution. We aim at deriving the star formation and gas accretion history of IC10, a local dwarf irregular for which abundance, gas and mass determinations are available. We run detailed chemical evolution models to predict the evolution of several chemical elements (He, O, N, S) and compared our predictions with the observational data. We considered also other constraints such as the present time gas fraction and the star formation rate as well as the total estimated mass for IC10. We assumed a dark matter halo for this galaxy and studied the development of a galactic wind. We explored different star formation regimes: bursting and continuous. We also explored different wind situations: i) normal wind, where all the gas is lost at the same rate and ii) metal-enhanced wind, where metals produced by supernovae are preferentially lost. We also explored a case without wind. We varied the star formation efficiency (SFE), the wind efficiency and the time scale for the gas infall, which are the most important parameters in our models. We found that only models with metal-enhanced galactic winds can reproduce the properties of IC10. The star formation must have proceeded in bursts rather than continuously and the bursts must have been no more than ten over the whole galactic lifetime. Finally, IC10 must have formed by a slow process of gas accretion with a timescale of the order of 8 Gyr.

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Blobrana


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Title: IC10: the history of the nearest starburst galaxy through its Planetary Nebula and HII region populations
Authors: Laura Magrini (INAF, Osservatorio Astrofisico di Arcetri, Italy), Denise R. Goncalves (UFRJ - Observatorio do Valongo, Brazil)

We report the results of spectroscopic observations, obtained with the Gemini North Multi-Object Spectrograph, of 9 planetary nebulae (PNe) and 15 H ii regions located in the 5.5' x 5.5' inner region of the nearby starburst galaxy IC10. Twelve new candidate PNe have been discovered during our pre-imaging phase. Nine of them have been spectroscopically confirmed. The direct availability of the electron temperature diagnostics in several nebulae allowed an accurate determination of the metallicity map of IC10 at two epochs: the present-time from H ii regions and the old/intermediate-age from PNe. We found a non-homogeneous distribution of metals at both epochs, but similar average abundances were found for the two populations. The derived age-metallicity relation shows a little global enrichment interpreted as the loss of metals by SN winds and to differential gas outflows. Finally, we analysed the production of oxygen --through the third dredge-up-- in the chemical abundance patterns of the PN populations belonging to several dwarf irregular galaxies. We found that the third dredge-up of oxygen is a metallicity dependent phenomenon occurring mainly for 12+ log (O/H) =< 7.7 and substantially absent in IC10 PNe.

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Blobrana


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IC10 galaxy
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Title: A study of the kinematics near WR-stars in the IC10 galaxy
Authors: Podorvanyuk N.Yu

A study of the ionised and neutral gas kinematics near 23 WR stars in the Irr galaxy IC10 are provided. For most of the stars signs of the WR winds impact on the interstellar medium were detected. A rough estimate of the power of wind WR stars is about ~(0.01-0.84) 10^38 erg / sec.

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Blobrana


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IC10 StSy-1
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Most Distant Symbiotic Star Pair Discovered
An international team led by Brazilian astronomer Denise Gonçalves used the Gemini Multi-Object Spectrograph (GMOS) on Gemini North to discover the most distant known symbiotic star. The star is part of a dwarf starburst galaxy in the Local Group called IC10 and is located about 750 kiloparsecs (about 2.5 million light-years) away.
A symbiotic star is a variable binary star in which one star has expanded its outer envelope, in the late stages of its evolution, and is shedding mass quickly on another hot star (often a white dwarf). Some time in the future, the pair will end catastrophically with the white dwarf detonating as a Type Ia supernova as more material is dumped on it by the red giant.
Symbiotic stars are critical in understanding Type Ia supernovae and the evolution of binary star systems. However, relatively few systems of this sort are known so finding them outside of our galaxy is an important step in developing a cohesive theory of how symbiotic stars interact over their lifetimes in different environments.
This particular star pair (IC10 StSy-1) shines at apparent magnitude V=24.62±0.02 and the cooler component matches that of M8III giants in our solar neighbourhood. Its observed emission lines belong to the Balmer series, [SII], [NII] and [OIII] which suggests a low electronic density, negligible optical depth effects and a temperature (Teff) for the ionising source of between 35,000 and 90,000 K. The spectrum of the new symbiotic star in the pair is an almost perfect copy of the well-known nearby symbiotic star Hen 2-147 and is also similar to the famous naked-eye star Mira in the constellation Cetus.

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Blobrana


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Title: Discovery in IC10 of the farthest known symbiotic star
Authors: Denise R. Goncalves (1), Laura Magrini (2), Ulisse Munari (3), Romano L. M. Corradi (4 and 5), Roberto D. D. Costa (6) ((1) UFRJ - Observatorio do Valongo, Brazil; (2) INAF - Osservatorio Astrofisico di Arcetri, Italy; (3) INAF - Osservatorio Astronomico di Padova, Italy; (4) Isaac Newton Group of Telescopes, Spain; (5) Instituto de Astrofisica de Canarias, Spain; (6) IAG - Universidade de Sao Paulo, Brazil)

We report the discovery of the first known symbiotic star in IC10, a starburst galaxy belonging to the Local Group, at a distance of ~750kpc. The symbiotic star was identified during a survey of emission-line objects. It shines at V = 24.62±0.04, V - R_C = 2.77±0.05 and R_C - I_C = 2.39±0.02 and suffers from E(B-V) = 0.85±0.05 reddening. The spectrum of the cool component well matches that of solar neighbourhood M8III giants. The observed emission lines belong to Balmer series, [SII], [NII] and [OIII]. They suggest a low electronic density, negligible optical depth effects and 35,000K < T_eff < 90,000K for the ionising source. The spectrum of the new symbiotic star in IC10 is an almost perfect copy of that of Hen 2-147, a well known Galactic symbiotic star and Mira.

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Blobrana


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Title: Imaging of the Stellar Population of IC10 with Laser Guide Star Adaptive Optics and the Hubble Space Telescope
Authors: William D. Vacca, Christopher D. Sheehy, James R. Graham (Berkeley)

We present adaptive optics (AO) images of the central starburst region of the dwarf irregular galaxy IC10. The Keck 2 telescope laser guide star was used to achieve near diffraction-limited performance at H and K' (Strehls of 18% and 32%, respectively). The images are centred on the putative Wolf-Rayet (W-R) object (MAC92)24. We combine our AO images with F814W data from HST. By comparing the K' vs. (F814W)-K' colour-magnitude diagram (CMD) with theoretical isochrones, we find that the stellar population is best represented by at least two bursts of star formation, one ~ 10 Myr ago and one much older (150-500 Myr). Young, blue stars are concentrated in the vicinity of (MAC92)24. This population represents an OB association with a half-light radius of about 3 pc. We resolve the W-R object (MAC92)24 into at least six blue stars. Four of these components have near-IR colours and luminosities that make them robust WN star candidates. By matching the location of C-stars in the CMD with those in the SMC we derive a distance modulus for IC10 of about 24.5 mag. and a foreground reddening of E(B-V) = 0.95. We find a more precise distance by locating the tip of the giant branch in the F814W, H, and K' luminosity functions. We find a weighted mean distance modulus of 24.48 ± 0.08. The systematic error in this measurement, due to a possible difference in the properties of the RGB populations in IC10 and the SMC, is ± 0.16 mag.

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