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RE: Blue Compact Dwarf Galaxies
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Title: A Study on the Chemical Properties of Blue Compact Dwarf Galaxies
Authors: Yinghe Zhao (PMO), Yu Gao (PMO), Qiusheng Gu (NJU)

In this paper, we report our studies on the gaseous and chemical properties of a relatively large sample (53 members) of blue compact dwarf galaxies (BCDs). The results of correlations among the oxygen abundance, stellar mass, gas mass, baryonic mass, and gas fraction are present both for E- and I-type BCDs, which are classified according to Loose & Thuan (1985) and show elliptical and irregular outer haloes, respectively. These correlations of I-type BCDs show similar slopes to those of E-type ones. However, in general, E-type BCDs are more gas-poor and metal-rich than I-type ones at a given baryonic mass. Based on these results, we suggest that E-type BCDs, at least a part of them, and I-type ones might be likely at different evolutionary phases and/or having different progenitors. Our investigation of the correlation between oxygen abundance and gas fraction shows that BCDs appear to have not evolved as isolated systems, but to have experienced some gas flows and/or mergers.

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Low Metallicity Blue Compact Dwarf Galaxies
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Title: WISE Discovery of Low Metallicity Blue Compact Dwarf Galaxies
Authors: Roger L. Griffith (IPAC), Chao-Wei Tsai (IPAC), Daniel Stern (JPL), Andrew Blain (Leicester), Peter R. M. Eisenhardt (JPL), Fiona Harrison (Caltech), Thomas H. Jarrett (IPAC), Kristin Madsen (Caltech), Spencer A. Stanford (UC Davis), Edward L. Wright (UCLA), Jingwen Wu (JPL), Yanling Wu (IPAC), Lin Yan (IPAC)

We report two new low metallicity blue compact dwarf galaxies (BCDs), WISEP J080103.93+264053.9 (hereafter W0801+26) and WISEP J170233.53+180306.4 (hereafter W1702+18), discovered using the Wide-field Infrared Survey Explorer (WISE). We identified these two BCDs from their extremely red colors at mid-infrared wavelengths, and obtained follow-up optical spectroscopy using the Low Resolution Imaging Spectrometer on Keck I. The mid-infrared properties of these two sources are similar to the well studied, extremely low metallicity galaxy SBS 0335-052E. We determine metallicities of 12 + log(O/H) = 7.75 and 7.63 for W0801+26 and W1702+18, respectively, placing them amongst a very small group of very metal deficient galaxies (Z < 1/10 Zsun). Their > 300 Angstrom Hbeta equivalent widths, similar to SBS 0335-052E, imply the existence of young (< 5 Myr) star forming regions. We measure star formation rates of 2.6 and 10.9 Msun/yr for W0801+26 and W1702+18, respectively. These BCDs, showing recent star formation activity in extremely low metallicity environments, provide new laboratories for studying star formation in extreme conditions and are low-redshift analogs of the first generation of galaxies to form in the universe. Using the all-sky WISE survey, we discuss a new method to identify similar star forming, low metallicity BCDs.

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SBS0335-052E
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Title: Super Star Clusters in SBS0335-052E
Authors: Rodger I. Thompson, Marc Sauvage, Robert C. Kennicutt, Charles Engelbracht, Leonardo Vanzi, Glenn Schneider

As one of the lowest metallicity star forming galaxies, with a nucleus of several super star clusters, SBS0335-052E is the subject of substantial current study. We present new insights on this galaxy based on new and archival high spatial resolution NICMOS and ACS images. We provide new measurements and limits on the size of several of the SSCs. The images have sufficient resolution to divide the star formation into compact regions and newly discovered extended regions, indicating a bi-modal form of star formation. The star formation regions are dated via the equivalent width of the Pa alpha emission and we find that two of the extended regions of star formation are less than 10 million years old. Our previous finding that stellar winds confine the photo-ionising flux to small regions around individual stars is consistent with the new observations. This may allow planet formation in what would traditionally be considered a harsh environment and has implications for the number of planets around globular cluster stars. In addition the images pinpoint the regions of H2 emission as located in, but not at the centre of the two star forming super star clusters, S1 and S2.

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Posts: 131433
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Blue Compact Dwarf Galaxies
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Title: Blue Compact Dwarf Galaxies with Spitzer: The Infrared/Radio Properties
Authors: Yanling Wu, V. Charmandaris, J.R. Houck, J.Bernard-Salas, V.Lebouteiller, B.R. Brandl, D. Farrah

We study the correlation between the radio, mid-infrared and far-infrared properties for a sample of 28 blue compact dwarf (BCD) and low metallicity star-forming galaxies observed by Spitzer. We find that these sources extend the same far-infrared to radio correlation typical of star forming late type galaxies to lower luminosities. In BCDs, the 24um (or 22um) mid-infrared to radio correlation is similar to starburst galaxies, though there is somewhat larger dispersion in their q_24 parameter compared to their q_FIR. No strong correlations between the q parameter and galaxy metallicity or effective dust temperature have been detected, though there is a hint of decreasing q_24 at low metallicities. The two lowest metallicity dwarfs in our sample, IZw18 and SBS0335-052E, despite their similar chemical abundance, deviate from the average q_{24} ratio in opposite manners, displaying an apparent radio excess and dust excess respectively.

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