A Deep Census of Outlying Star Formation in the M101 Group

Garner, Ray; Mihos, J. Christopher; Harding, Paul; Watkins, Aaron E.

doi:10.3847/1538-4357/ac0055

Cited by 5 publications

(9 citation statements)

References 120 publications

(155 reference statements)

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“…However, as described in detail by Garner et al (2021) and noted elsewhere (e.g., Kellar et al 2012;Watkins et al 2017), stars will broadly mimic Hα emission, as our off-band filters can sample absorption features in the stellar continuum. In order to mask the contribution of these stars, we utilized two surveys targeting both bright and faint stars.…”

Section: H II Region Detectionmentioning

confidence: 93%

“…The broadband photometry has been transformed to standard Johnson B and V as described in Mihos et al (2013). Our general technique for detecting H II regions in M101 and its satellites is much the same as utilized in Garner et al (2021) with some key differences described below to account for region detection within a galaxy rather than interspersed throughout the M101 Group.…”

Section: H II Region Detectionmentioning

confidence: 99%

“…Within a 30′ × 30′ cutout centered on M101, this resulted in 421 point sources being detected. In Garner et al (2021), we used Gaia data to remove stars from our imaging of the intragroup field around M101, but here we are working within the bright disk of M101 where such data is not available, thus the necessity of using 2MASS photometry instead.…”

Section: H II Region Detectionmentioning

confidence: 99%

“…Having masked both bright stars in the Tycho-2 Catalog around M101 and dim stars in the 2MASS All-Sky Catalog of Point Sources in front of M101, we create a two-dimensional background object to calculate the background sky level and its uncertainty. As in Garner et al (2021), all galaxies (both background and M101 Group members) were masked, and the sky level was estimated in boxes of 100 × 100 pixels (145″ × 145″) with filter sizes of 10 × 10 pixels (14 5 × 14 5).…”

Section: H II Region Detectionmentioning

confidence: 99%

“…In an effort to add to the growing evidence of radial breaks and azimuthal variations in the oxygen abundances of galaxies, we have used Case Western Reserve University's (CWRU's) Burrell Schmidt 24/36-inch telescope to add to the deep, widefield, multiline, narrowband observations of the nearby spiral galaxy M101 (NGC 5457) and its group environment presented in previous papers (Watkins et al 2017;Garner et al 2021). In addition to the previous narrowband images targeting Hα, Hβ, and [O III] (Watkins et al 2017;Garner et al 2021), we now add deep narrowband images targeting [O II] for the first time. This allows us to sample the entire disks of M101 and its major satellites, NGC 5477 and NGC 5474 (see Table 1), with our large survey area (∼6 deg −2 ) and our photometric depth, which allows us to analyze faint inter-arm and outer disk H II regions.…”

Section: Introductionmentioning

confidence: 99%

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

Garner

Mihos

Harding

et al. 2022

ApJ

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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.

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Section: H II Region Detectionmentioning

confidence: 93%

Section: H II Region Detectionmentioning

confidence: 99%

Section: H II Region Detectionmentioning

confidence: 99%

Section: H II Region Detectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Garner

Mihos

Harding

et al. 2022

ApJ

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Implications on star formation rate indicators from H ii regions and diffuse ionized gas in the M101 Group

Watkins,

Mihos,

Harding

et al. 2024

Monthly Notices of the Royal Astronomical Society

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We examine the connection between diffuse ionised gas (DIG), H ii regions, and field O and B stars in the nearby spiral M101 and its dwarf companion NGC 5474 using ultra-deep Hα narrow-band imaging and archival GALEX UV imaging. We find a strong correlation between DIG Hα surface brightness and the incident ionising flux leaked from the nearby H ii regions, which we reproduce well using simple Cloudy simulations. While we also find a strong correlation between Hα and co-spatial FUV surface brightness in DIG, the extinction-corrected integrated UV colours in these regions imply stellar populations too old to produce the necessary ionising photon flux. Combined, this suggests that H ii region leakage, not field OB stars, is the primary source of DIG in the M101 Group. Corroborating this interpretation, we find systematic disagreement between the Hα- and FUV-derived star formation rates (SFRs) in the DIG, with SFRHα <SFRFUV everywhere. Within H ii regions, we find a constant SFR ratio of 0.44 to a limit of ∼10−5 M⊙ yr−1. This result is in tension with other studies of star formation in spiral galaxies, which typically show a declining SFRHα/SFRFUV ratio at low SFR. We reproduce such trends only when considering spatially averaged photometry that mixes H ii regions, DIG, and regions lacking Hα entirely, suggesting that the declining trends found in other galaxies may result purely from the relative fraction of diffuse flux, leaky compact H ii regions, and non-ionising FUV-emitting stellar populations in different regions within the galaxy.

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Discovery of Extraplanar H i Clouds and a H i Tail in the M101 Galaxy Group with FAST

Zhang

et al. 2021

ApJ

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We present a new high-sensitivity H i observation toward nearby spiral galaxy M101 and its adjacent 2° × 2° region using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). From the observation, we detect a more extended and asymmetric H i disk around M101. While the H i velocity field within the M101's optical disk region is regular, indicating that the relatively strong disturbance occurs in its outer disk. Moreover, we identify three new H i clouds located on the southern edge of the M101's H i disk. The masses of the three H i clouds are 1.3 × 107 M ⊙, 2.4 × 107 M ⊙, and 2.0 × 107 M ⊙, respectively. The H i clouds similar to dwarf companion NGC 5477 rotate with the H i disk of M101. Unlike NGC 5477, they have no optical counterparts. Furthermore, we detect a new H i tail in the extended H i disk of M101. The H i tail detected gives reliable evidence for M101 interaction with the dwarf companion NGC 5474. We argue that the extraplanar gas (three H i clouds) and the H i tail detected in the M101's disk may originate from a minor interaction with NGC 5474.

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A Deep Census of Outlying Star Formation in the M101 Group

Cited by 5 publications

References 120 publications

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

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

Implications on star formation rate indicators from H ii regions and diffuse ionized gas in the M101 Group

Discovery of Extraplanar H i Clouds and a H i Tail in the M101 Galaxy Group with FAST

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