2006/05/09 by C. M. Schwartz, C. L. Martin, Crystal L. Martin +7 · 3 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/504961
published as Astrophys.J.646:858-871,2006 · 41 pages, 14 figures, accepted for publication in The Astrophysical Journal
arxiv created 2006/05/09 · openalex publication_date 2006/07/28 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We measure Doppler shifts of interstellar absorption lines in HST STIS spectra of individual star clusters in nearby UV-selected galaxies. Values for systemic velocities, which are needed to quantify outflow speeds, are taken from the literature and verified with stellar lines. We detect outflowing gas in 8 of 17 galaxies via low-ionization lines (e.g., C II, Si II, Al II), which trace cold and/or warm gas. The starbursts in our sample are intermediate in luminosity (and mass) to dwarf galaxies and luminous infrared galaxies (LIRGs), and we confirm that their outflow speeds (ranging from -100 to nearly -520 km s -1 , with an accuracy of ~80 km s -1 ) are intermediate to those previously measured in dwarf starbursts and LIRGs. We do not detect the outflow in high-ionization lines (such as C IV or Si IV); higher quality data will be needed to empirically establish how velocities vary with the ionization state of the outflow. We do verify that the low-ionization UV lines and optical Na I doublet give roughly consistent outflow velocities, solidifying an important link between studies of galactic winds at low and high redshift. To obtain a higher signal-to-noise ratio (S/N), we create a local average composite spectrum and compare it to the high- z Lyman break composite spectrum. It is surprising that the low-ionization lines show similar outflow velocities in the two samples. We attribute this to a combination of weighting toward higher luminosities in the local composite, as well as both samples being, on average, brighter than the "turnover" luminosity in the v -SFR relation.