Deep Narrowband Photometry of the M101 Group: Strong-line Abundances of 720 H ii Regions

Abstract

We present deep, narrowband imaging of the nearby spiral galaxy M101 and its satellites to analyze the oxygen abundances of their H ii regions. 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 [O iii] emission lines and the blue [O ii] 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 ratio R 23 to estimate oxygen abundances for the H ii regions in our sample, utilizing three different calibration techniques to provide a baseline estimate of the oxygen abundances. This results in ∼650 H ii regions for M101, 10 H ii regions for NGC 5477, and ∼60 H ii regions 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 beyond R ∼ 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.

The Preexplosion Environments and the Progenitor of SN 2023ixf from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX)

“…For a given R 23 , there are two associated metallicity values, one is in the metal-poor branch, and the other is in the metal-rich branch (e.g., Kobulnicky et al 1999). SN 2023ixf is ∼4.5 kpc away from the center of M101, which is within the break radius in the abundance gradient at 15.4 kpc (Garner et al 2022). This suggests that the surroundings of SN 2023ixf would probably favor the metal-rich branch.…”

A Dynamic Galaxy: Stellar Age Patterns across the Disk of M101

“…The narrowband imaging data for this project were taken over four observing seasons using CWRU Astronomy's 24/ 36 inch Burrell Schmidt telescope located at Kitt Peak Observatory. Full details of our narrowband imaging techniques are given in Watkins et al (2017) and Garner et al (2022). Quantitative information about the narrowband filters and final imaging stacks for the data set is given in Table 2 of Garner et al (2022).…”

“…Full details of our narrowband imaging techniques are given in Watkins et al (2017) and Garner et al (2022). Quantitative information about the narrowband filters and final imaging stacks for the data set is given in Table 2 of Garner et al (2022). Briefly, we summarize our observations here.…”

“…In an effort to study stellar ages and their connection to the nature of spiral patterns, we have used Case Western Reserve Universityʼs (CWRU's) Burrell Schmidt 24/36 inch telescope and its accompanying narrowband filters to image the nearby spiral galaxy M101 (NGC 5457). While these images targeting Hα, Hβ, [O III] λλ4959,5007, and [O II] λλ3726,3729 have been used to study the emission line properties of M101 and its group environment (Watkins et al 2017;Garner et al 2021Garner et al , 2022, these images also reveal age-diagnostic absorption signatures in the stellar disk of M101 (Figure 2). Thus, by measuring EWs through our narrowband filters, we are able to place constraints on the stellar ages throughout M101ʼs disk.…”

Far-ultraviolet to Near-infrared Observations of SN 2023ixf: A High-energy Explosion Engulfed in Complex Circumstellar Material

“…We adopt a mean distance of 6.82 ± 0.14 Mpc (μ = 29.17 ± 0.04 mag). The gas-phase metallicity was computed by Garner et al (2022) using various H II regions in the galaxy and estimated an oxygen abundance of 12 + log[O/H] ∼ 8.7 in the outer spiral arms of the galaxy, which is similar to solar metallicity (Asplund et al 2009).…”