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Full-Text Articles in Physical Sciences and Mathematics
A Wfc3 Study Of Globular Clusters In Ngc 4150 - An Early-Type Minor Merger, Sugata Kaviraj, R. Mark Crockett, Bradley C. Whitmore, Joseph Silk, Robert W. O'Connell, Rogier A. Windhorst, Max Mutchler, Marina Rejkuba, Sukyoung Yi, Jay A. Frogel, Daniela Calzetti
A Wfc3 Study Of Globular Clusters In Ngc 4150 - An Early-Type Minor Merger, Sugata Kaviraj, R. Mark Crockett, Bradley C. Whitmore, Joseph Silk, Robert W. O'Connell, Rogier A. Windhorst, Max Mutchler, Marina Rejkuba, Sukyoung Yi, Jay A. Frogel, Daniela Calzetti
Daniela Calzetti
We combine near-ultraviolet (NUV; 2250 {\AA}) and optical (U, B, V, I) imaging from the Wide Field Camera 3 (WFC3), on board the Hubble Space Telescope (HST), to study the globular cluster (GC) population in NGC 4150, a sub-L* (M_B ~ -18.48 mag) early-type minor-merger remnant in the Coma I cloud. We use broadband NUV-optical photometry from the WFC3 to estimate individual ages, metallicities, masses and line-of-sight extinctions [E_(B-V)] for 63 bright (M_V < -5 mag) GCs in this galaxy. In addition to a small GC population with ages greater than 10 Gyr, we find a dominant population of clusters with ages centred around 6 Gyr, consistent with the expected peak of stellar mass assembly in faint early-types residing in low-density environments. The old and intermediate-age GCs in NGC 4150 are metal-poor, with metallicities less than 0.1 ZSun, and reside in regions of low extinction (E_(B-V) < 0.05 mag). We also find a population of young, metal-rich (Z > 0.3 ZSun) clusters that have formed within the last Gyr and reside in relatively dusty (E_(B-V) > 0.3 mag) regions that are coincident with the part of the …
Dust-Corrected Star Formation Rates Of Galaxies. Ii. Combinations Of Ultraviolet And Infrared Tracers, Cai-Na Hao, C. Kennicutt Kr., Benjamin D. Johnson, Daniela Calzetti, Daniel A. Dale, John Moustakas
Dust-Corrected Star Formation Rates Of Galaxies. Ii. Combinations Of Ultraviolet And Infrared Tracers, Cai-Na Hao, C. Kennicutt Kr., Benjamin D. Johnson, Daniela Calzetti, Daniel A. Dale, John Moustakas
Daniela Calzetti
We present new calibrations of far-ultraviolet (FUV) attenuation as derived from the total infrared to FUV luminosity ratio (IRX) and the FUV-NUV color. We find that the IRX-corrected FUV luminosities are tightly and linearly correlated with the attenuation-corrected H\alpha\ luminosities (as measured from the Balmer decrement), with a rms scatter of $\pm 0.09$ dex. The ratios of these attenuation-corrected FUV to H\alpha\ luminosities are consistent with evolutionary synthesis model predictions, assuming a constant star formation rate over 100 Myr, solar metallicity and either a Salpeter or a Kroupa IMF with lower and upper mass limits of 0.1 and 100\msun. The …