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CIRPASS near-infrared integral-field spectroscopy of massive star clusters in the starburst galaxy NGC 1140
We analyse near-infrared integral field spectroscopy of the centralstarburst region of NGC 1140, obtained at the Gemini-South telescopeequipped with CIRPASS. Our ~1.45-1.67μm wavelength coverage includesthe bright [FeII]λ 1.64-μm emission line, as well ashigh-order Brackett (hydrogen) lines. While strong [FeII] emission,thought to originate in the thermal shocks associated with supernovaremnants, is found throughout the galaxy, both Br 12-4 and Br 14-4emission, and weak CO(6,3) absorption, is predominantly associated withthe northern starburst region. The Brackett lines originate fromrecombination processes occurring on smaller scales in (young) HIIregions. The time-scale associated with strong [FeII] emission impliesthat most of the recent star-formation activity in NGC 1140 was inducedin the past ~35-55Myr. Based on the spatial distributions of the [FeII]versus Brackett line emission, we conclude that a galaxy-wide starburstwas induced several tens of Myr ago, with more recent starburst activityconcentrated around the northern starburst region.This scenario is (provisionally) confirmed by our analysis of thespectral energy distributions of the compact, young massive starclusters (YMCs) detected in new and archival broad-band Hubble SpaceTelescope images. The YMC ages in NGC 1140 are all <~20Myr,consistent with independently determined estimates of the starburst ageof the galaxy, while there appears to be an age difference between thenorthern and southern YMC complexes in the sense expected from ourCIRPASS analysis. Our photometric mass estimates of the NGC 1140 YMCs,likely upper limits, are comparable to those of the highest-massGalactic globular clusters and to spectroscopically confirmed masses of(compact) YMCs in other starburst galaxies. Our detection of similarlymassive YMCs in NGC 1140 supports the scenario that such objects formpreferentially in the extreme environments of interacting and starburstgalaxies.
| UBV photometry of early-type stars in two regions at high galactic latitudes
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| A Finding List of Stars of Spectral Type A7 and Earlier in Regions at High Galactic Latitudes. IV. 3 HLF 4
An objective prism survey has been made of stars of spectral type A7 andearlier in a 45 square degree region in the 3 HLF 4 area (l^II = 0°,b^II = -45°) as part of an investigation of galactic structureperpendicular to the galactic plane. The survey reported here was madewith the 4° prism on the Michigan Curtis Schmidt telescope at CerroTololo. A finding list containing positions and spectral types for 146stars is presented with finding charts for the stars too faint to beincluded on the Cordoba Durchmusterung charts.
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