Search for: All records

Abstract We present deep, narrowband imaging of the nearby spiral galaxy M101 and its satellites to analyze the oxygen abundances of their Hiiregions. Using Case Western Reserve University’s Burrell Schmidt telescope, we add to the narrowband data set of the M101 Group, consisting of Hα, Hβ, and [Oiii] emission lines and the blue [Oii]λ3727 emission line for the first time. This allows for complete spatial coverage of the oxygen abundance of the entire M101 Group. We used the strong-line ratioR₂₃to estimate oxygen abundances for the Hiiregions in our sample, utilizing three different calibration techniques to provide a baseline estimate of the oxygen abundances. This results in ∼650 Hiiregions for M101, 10 Hiiregions for NGC 5477, and ∼60 Hiiregions for NGC 5474, the largest sample for this Group to date. M101 shows a strong abundance gradient, while the satellite galaxies present little or no gradient. There is some evidence for a flattening of the gradient in M101 beyondR∼ 14 kpc. Additionally, M101 shows signs of azimuthal abundance variations to the west and southwest. The radial and azimuthal abundance variations in M101 are likely explained by an interaction it had with its most massive satellite, NGC 5474, ∼300 Myr ago combined with internal dynamical effects such as corotation. 

Abstract Stellar feedback is fundamental to the modeling of galaxy evolution, as it drives turbulence and outflows in galaxies. Understanding the timescales involved are critical for constraining the impact of stellar feedback on the interstellar medium. We analyzed the resolved star formation histories along with the spatial distribution and kinematics of the atomic and ionized gas of four nearby star-forming dwarf galaxies (NGC 4068, NGC 4163, NGC 6789, and UGC 9128) to determine the timescales over which stellar feedback drives turbulence. The four galaxies are within 5 Mpc and have a range of properties including current star formation rates of 0.0005–0.01M_⊙yr⁻¹, log(M_*/M_⊙) between 7.2 and 8.2, and log(M_Hi/M_⊙) between 7.2 and 8.3. Their color–magnitude diagram derived star formation histories over the past 500 Myr were compared to their atomic and ionized gas velocity dispersion and Hienergy surface densities as indicators of turbulence. The Spearman’s rank correlation coefficient was used to identify any correlations between their current turbulence and their past star formation activity on local scales (∼400 pc). The strongest correlation found was between the Hiturbulence measures and the star formation rate 100–200 Myr ago. This suggests a coupling between the star formation activity and atomic gas on this timescale. No strong correlation between the ionized gas velocity dispersion and the star formation activity between 5 and 500 Myr ago was found. The sample and analysis are the foundation of a larger program aimed at understanding the timescales over which stellar feedback drives turbulence.