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IC 10
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Title: The Star Cluster System in the Local Group Starburst Galaxy IC 10
Author: Sungsoon Lim, Myung Gyoon Lee

We present a survey of star clusters in the halo of IC 10, a starburst galaxy in the Local Group based on Subaru R band images and NOAO Local Group Survey UBVRI images. We find five new star clusters. All these star clusters are located far from the center of IC 10, while previously known star clusters are mostly in the main body. Interestingly the distribution of these star clusters shows an asymmetrical structure elongated along the east and south-west direction. We derive UBVRI photometry of 66 star clusters including these new star clusters as well as previously known star clusters. Ages of the star clusters are estimated from the comparison of their UBVRI spectral energy distribution with the simple stellar population models. We find that the star clusters in the halo are all older than 1 Gyr, while those in the main body have various ages from very young (several Myr) to old (>1 Gyr). The young clusters (<10 Myr) are mostly located in the H{\alpha} emission regions and are concentrated on a small region at 2' in the south-east direction from the galaxy center, while the old clusters are distributed in a wider area than the disk. Intermediate-age clusters (~100 Myr) are found in two groups. One is close to the location of the young clusters and the other is at ~4' from the location of the young clusters. The latter may be related with past merger or tidal interaction.

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Title: Oxygen-rich dust production in IC 10
Authors: V. Lebouteiller, G. C. Sloan, M. A. T. Groenewegen, M. Matsuura, D. Riebel, D. G. Whelan, J. Bernard-Salas, P. Massey, E. Bayet

We report the detection of oxygen-rich circumstellar envelopes in stars of the nearby (700 kpc) starburst galaxy IC 10. The star formation history and the chemical environment of this galaxy makes it an ideal target to observe dust production by high-mass stars in a low-metallicity environment. The goal of this study is to identify oxygen-rich stars in IC 10 and to constrain their nature between asymptotic giant branch stars (AGBs), red supergiants (RSGs), and other infrared bright sources. We examine the mass-loss rate of the stars and compare to results obtained for the Magellanic Clouds. Our objectives are to (1) assess whether RSGs can be significant dust producers in IC 10, and (2), solve the discrepancy between the star formation history of IC 10 and the relatively low number of RSGs detected in the optical. We search for silicate dust in emission by using the spectral map observed with the Infrared Spectrograph on board the Spitzer Space Telescope. The optical (UBVRI) and infrared (JHK, Spitzer/IRAC and Spitzer/MIPS) photometry is used to assert the membership of the stars to IC 10 and disentangle between AGBs and RSGs. Radiative models are used to infer mass-loss rates and stellar luminosities. The luminosity and colours of at least 9 silicate emission sources are consistent with stars within IC 10. Furthermore, the photometry of 2 of these sources is consistent with RSGs. We derive dust mass-loss rates similar to the values found in the Magellanic Clouds. Accounting for the sample completeness, RSGs are not important contributors to the dust mass budget in IC 10.

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RE: Local Group Galaxy IC 10
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Title: Stellar Population of the Irregular Galaxy IC 10
Authors: N. A. Tikhonov, O. A. Galazutdinova

Based on our observations with the 6-m BTA telescope at the Special Astrophysical Observatory, the Russian Academy of Sciences, and archival Hubble Space Telescope images, we have performed stellar photometry for several regions of the irregular galaxy IC 10, a member of the Local Group. Distance moduli with a median value of (m-M)=24.47, D=78040 kpc, have been obtained by the TRGB method for several regions of IC 10. We have revealed 57 star clusters with various masses and ages within the fields used. Comparison of the Hertzsprung - Russell diagrams for star clusters in IC 10 with theoretical isochrones has shown that this galaxy has an enhanced metallicity, which probably explains the high ratio of the numbers of carbon and nitrogen Wolf-Rayet stars (WC/WN). The size of the galaxy's thick disk along its minor axis is 10'.5 and a more extended halo is observed outside this disk.

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Starburst Galaxy IC 10
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Title: Reddening and Distance of the Local Group Starburst Galaxy IC 10
Authors: Minsun Kim (1,2), Eunhyeuk Kim (2,4), Narae Hwang (2,3), Myung Gyoon Lee (2), Myungshin Im (2), Hiroshi Karoji (3), Junichi Noumaru (4), and Ichi Tanaka (3) ((1) Korea Astronomy and Space Science Institute, (2) Seoul National University, (3) National Astronomical Observatory of Japan, and (4) Yonsei University)

We estimate the reddening and distance of the nearest starburst galaxy IC 10 using deep near infrared JHK_{S} photometry obtained with the Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru telescope. We estimate the foreground reddening toward IC 10 using UBV photometry of IC 10 from the Local Group Survey, obtaining E(B-V)=0.520.04 mag. We derive the total reddening including the internal reddening, E(B-V)=0.98 0.06 mag, using UBV photometry of early-type stars in IC 10 and comparing JHK_{S} photometry of red giant branch stars in IC 10 and the SMC. Using the 2MASS point source catalogue of 20 Galactic globular clusters, we derive a relation between the metallicity [Fe/H]_{CG97} and the slope of the red giant branch in the K_{S}- (J-K_{S}) colour-magnitude diagram. The mean metallicity of the red giant branch stars in IC 10 is estimated to be [Fe/H]_{CG97}=-1.080.28. The magnitude of the tip of the red giant branch (TRGB) of IC 10 in the K_{S} band is measured to be K_{S,TRGB}=18.280.01. Based on the TRGB method, we estimate the distance modulus of IC 10 to be (m-M)_{0}=24.270.03{(random)}0.18{(systematic)}, corresponding to the distance of d=7151060 kpc. This confirms that IC 10 is a member of the Local Group.

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RE: Local Group Galaxy IC 10
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Edwin Hubble once called IC 10 one of the most curious objects in the sky, and new observations of the extremely faint, lightweight dwarf galaxy are giving scientists new clues about how populations of stars are born.
Though the properties of stars is one of the most well-studied topics in astronomy, scientists still dont fully understand all the mechanisms involved in star formation and evolution, particularly in galaxies with low levels of oxygen, nitrogen and other heavy elements. But scientists studying the IC 10 galaxy may soon understand how stars might have looked like in the distant past, when the universe was in a younger, more pristine form.

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IC10_e2
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Credit: UCB/NASA/Keck Observatory
The central starburst region of the IC 10 irregular dwarf galaxy.


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Astronomers using the W.M. Keck Observatory on Mauna Kea have been studying a "dwarf galaxy" about 2.6 million light years from Earth to try to get a picture of what our own Milky Way galaxy might have looked like billions of years ago.
The study of the very faint IC 10 galaxy also used images from NASA's Hubble Space Telescope, and has revealed evidence of a vigorous star formation event that took place within the last 10 million years.
That research is giving astronomers a picture of what the Milky Way might have looked like billions of years ago before the galaxy's interstellar medium was enriched with elements such as oxygen and nitrogen.

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Galaxy IC 10.kmz
Google Sky File

-- Edited by Blobrana at 14:57, 2008-01-12

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Title: The Proper Motion of the Local Group Galaxy IC 10
Authors: A. Brunthaler (1), M.J. Reid (2), H. Falcke (3,4), C. Henkel (1), K.M. Menten (1) ((1) Max-Planck-Institut fuer Radioastronomie, (2) Harvard-Smithsonian Centre for Astrophysics, (3) ASTRON, (4) Universiteit Nijmegen)

We have measured the proper motion of the Local Group galaxy IC 10 with the Very Long Baseline Array by measuring the position of an H2O maser relative to two background quasars over 4.3 years. After correction for the rotation of the Milky Way and IC 10, we obtain a motion of -39 9 microas/yr toward the East and 31 8 microas/yr toward the North. This corresponds to a total space velocity of 215 42 km/s relative to the Milky Way for an assumed distance of 660 66 kpc. Assuming that IC 10 and M33, for which also a proper motion measurement exists, are bound to M31, we calculate a lower limit for the mass of M31 of 7.5 x 10^11 Msol.

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